Biomimetic intelligent nanoplatform with cascade amplification effect for tumor synergy therapy

doi:10.21203/rs.3.rs-4913584/v1

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Biomimetic intelligent nanoplatform with cascade amplification effect for tumor synergy therapy

https://doi.org/10.21203/rs.3.rs-4913584/v1

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Tumor heterogeneity, immune-suppressive microenvironment and the precise killing of tumor cells by drugs are important factors affecting tumor treatment. In this study, an environment-responsive therapeutic nanoplatform based on metal-organic frameworks (FM@IQ/PST&ZIF-8/DOX) is developed. Under near-infrared (NIR) irradiation, it realizes the combined treatment of photothermal/immunotherapy/chemotherapy, compensating for the deficiencies of each single treatment and effectively achieving the cascade effect of tumor treatment. When it enters the blood circulation, the surface-modified erythrocyte cell membrane can disguise itself, effectively avoiding its elimination by body immune system. Moreover, the surface-modified folic acid molecules can specific binding with the folic acid receptors on the surface of tumor cells, increasing the uptake of tumor cells to them and thereby promoting its accumulation in tumor tissues. Under NIR irradiation, it induces apoptosis of tumor cells and releases tumor-associated antigen, effectively solving the problem of poor therapeutic effect caused by tumor heterogeneity. Subsequently, the slightly acidic tumor microenvironment can cause the framework of FM@IQ/PST&ZIF-8/DOX to collapse, achieving the precise release of imiquimod and doxorubicin. In this therapeutic platform, imiquimod, as a small molecule immune modulator, can effectively improve the immunosuppressive microenvironment, stimulate the body's anti-tumor immune response and inhibit the recurrence and metastasis of tumors. Therefore, the novel FM@IQ/PST&ZIF-8/DOX drug delivery system designed in this research can not only achieve controllable and precise drug release, but also improve the immunosuppressive tumor microenvironment. It is expected to become a promising new strategy for tumor treatment and provide corresponding inspiration for the later research and development of environment-responsive drugs.

Biological sciences/Biotechnology/Biomaterials

Physical sciences/Engineering/Biomedical engineering

Tumor heterogeneity

tumor microenvironment

precise release

combined therapy for tumors

Tumors are caused by the abnormal proliferation of local cells and tissues under the influence of various factors, characterized by high recurrence and mortality rates, posing a serious threat to human health.^1–2 The main clinical methods for treating tumors include chemotherapy, radiotherapy, surgical resection and immunotherapy.³ Among them, immunotherapy mainly uses the body's immune system to kill tumor cells, which can not only effectively avoid the damage to normal tissues of the body, but also effectively avoid the recurrence and metastasis of tumors.⁴ It has shown increasingly significant advantages in the field of tumor treatment and is expected to become a primary method for cancer therapy. However, the heterogeneity of tumor tissues and the immune-suppressive microenvironment associated with tumors lead to suboptimal outcomes in immunotherapy.⁵

To improve the efficacy of tumor immunotherapy, various immunotherapeutic strategies have emerged in recent years, such as PD1/PDL1 antibody therapy, adoptive cell immunotherapy and immune vaccines.^6–7 Among these, immune vaccines have the potential to become the most promising treatment for completely eradicating tumors due to their strong specificity, low cost, and minimal side effects.⁸ However, the effectiveness of tumor vaccines is often compromised because tumors undergo multiple rounds of proliferation and division during their growth, leading to differences in the molecular and genetic composition of the daughter cells compared to the original tumor cells.⁹ This results in variations in tumor growth, invasiveness, and sensitivity to drugs, which adversely affects the therapeutic outcomes of tumor vaccines.¹⁰ In the absence of clearly defined tumor-specific antigens, whole-cell tumor vaccines encompass a comprehensive range of tumor-associated antigen (TAA) and are rich in epitopes for CD8⁺ T cells and CD4⁺ helper T cells.¹¹ They can simultaneously express MHC class I and II restricted antigens, triggering a broad and effective anti-tumor immune response, which gives them a unique advantage in tumor immunotherapy.¹² In view of this, some scientists have taken an alternative approach. They treat autologous or allogeneic tumor cells with physical factors (irradiation, high temperature, etc.), chemical factors (enzymolysis, etc.) and biological factors (viral infection, gene transfer, etc.) to prepare tumor whole-cell vaccines, which have become an effective method for personalized tumor treatment.^13–14 The greatest advantage of this vaccine is its inclusion of a comprehensive array of TAA, which reduces or eliminates the tumorigenicity of the tumor cells while preserving their immunogenicity, thereby effectively addressing the issue of tumor heterogeneity and activating the unique antigen-specific anti-tumor immunity in cancer patients. Among these methods, photothermal ablation offers high selectivity, low invasiveness, and controllability in both time and space, demonstrating exceptional advantages in the field of tumor treatment.^15–16

However, single photothermal therapy can easily cause damage to the surrounding normal tissues of the tumor.¹⁷ With the development of nanotechnology, particularly the research and development of near-infrared light-responsive nanoparticles, it is now possible to achieve passive accumulation in tumor tissues through retention and permeability. Under near-infrared light (NIR) excitation, these nanoparticles can generate a significant amount of heat in tumor tissues, inducing apoptosis of tumor cells and releasing TAA, which effectively solve the issue of tumor heterogeneity.^18–19 However, the immune-suppressive microenvironment of tumor tissues is a critical barrier that hinders the effectiveness of tumor vaccines.²⁰ To achieve efficient drug loading and targeted delivery to tumor tissues, metal-organic frameworks (MOFs) have emerged as typical photothermal nanocarriers. Due to their large specific surface area and porosity, rich interactions between host and guest molecules, good biocompatibility and easy surface functionalization, they demonstrate significant application potential in drug delivery systems and tumor treatment.^21–22 Furthermore, MOFs can achieve controlled and precise release of drug molecules based on specific tumor microenvironments (such as acidity, high concentrations of H₂O₂ and GSH). MOFs also possess high drug loading capacity, allowing them to carry multiple drugs and biomolecules simultaneously, thereby enabling multi-modal synergistic therapy for tumors.^23–24 However, there are challenges in the practical application of MOFs, such as low biocompatibility, poor biodegradability, insufficient long-term stability and susceptibility to clearance by the body's immune system during circulation, which hinder their effective clinical translation.²⁵ To overcome these problems, researchers are continuously exploring new strategies for the preparation and synthesis of MOFs such as surface modification and functionalization.²⁶ Nonetheless, the size of MOFs is similar to that of viruses, making them prone to be cleared by the immune system once they enter the bloodstream, significantly reducing their circulation time.²⁷ Therefore, researchers have begun to wrap cell membranes around the surface of MOFs and use the properties of the cell membranes themselves to improve the half-life and targeted delivery of MOFs in the bloodstream.^28–29 Zeolitic imidazolate framework-8 (ZIF-8), a widely and deeply studied MOF, exhibits great application potential in the biomedical field due to its simple and rapid synthesis and uniform pore structure.³⁰ More importantly, ZIF-8 has pH-responsive decomposition characteristics, releasing Zn²⁺ ions and loaded drugs under acidic conditions.³¹ Additionally, the released Zn²⁺ ions can induce anion influx and promote the generation of reactive oxygen species, leading to the rupture of the endosomal/lysosomal membranes within tumor cells.³² Although new strategies for tumor treatment based on ZIF-8 have emerged in recent years, chemotherapy remains the primary method for treating tumors in clinical practice.

In summary, this study presents an environment-responsive FM@IQ/PST&ZIF-8/DOX nanocarrier based on ZIF-8, which not only achieves efficient and targeted drug delivery but also enables the combined treatment of photothermal/chemotherapy/immunotherapy of tumors under NIR excitation, effectively inhibiting the metastasis and recurrence of tumor cells. As illustrated in the following Scheme 1a, this research employs Zn²⁺ ions, 2-methylimidazole and doxorubicin (DOX) to prepare ZIF-8/DOX nanocarriers through biomimetic mineralization and co-precipitation reactions. In order to improve the biocompatibility of ZIF-8/DOX and avoid damage to normal tissues caused by leakage of DOX during transportation in vivo, endogenous neurotransmitter serotonin is used to form Polyserotonin (PST) by oxidative polymerization on the surface of ZIF-8/DOX (PST&ZIF/DOX). The prepared PST shell exhibits superior photothermal conversion performance in the near-infrared region. And its unique conjugated molecular structure and adhesive properties enables for the PST shell to load the small molecular immunomodulator imiquimod (IQ) via π-π stacking interactions, thereby improving the immune-suppressive microenvironment and enhancing photothermal-based tumor immunotherapy strategies. To avoid clearance by the body’s immune system and non-specific distribution in vivo, folate-modified red blood cell membranes (FM) are used to encapsulate IQ/PST&ZIF/DOX and FM@IQ/PST&ZIF-8/DOX nanoplatform is prepared. When it is injected into the body through the tail vein of 4T1 transplanted tumor mice, the red blood cell membrane "stealth" the nanoplatform, preventing FM@IQ/PST&ZIF-8/DOX from being cleared by macrophages during circulation. Furthermore, the folate molecules on the surface of FM@IQ/PST&ZIF-8/DOX are used to bind with folate receptors on the surface of tumor cells, effectively promoting the uptake of FM@IQ/PST&ZIF-8/DOX by tumor cells. When FM@IQ/PST&ZIF-8/DOX enters the tumor tissue, the acidic tumor microenvironment disrupts the π-π interactions between PST and the drug molecules, which facilitates the release of IQ adsorbed on PST. Additionally, the acidic environment can lead to the degradation of FM@IQ/PST&ZIF-8/DOX and further release the loaded DOX (Scheme 1b). Therefore, FM@IQ/PST&ZIF-8/DOX nanocarriers for the treatment of cancer can effectively prolong the half-life of drugs in vivo, reducing the non-specific distribution of drugs in the body and realize the precise attack on tumor tissues. At the same time, they can also realize the combined therapy of photoheat/chemotherapy/immunization by using the photothermal properties of PST, thus making up for the defects of each single therapy and realizing the cascade effect of tumor therapy.

2.1 Synthesis process of FM@IQ/PST&ZIF-8/DOX

Firstly, blood specimens of healthy BALB/c mice were collected through ocular blood collection. The supernatant was discarded by centrifugation (2000 rpm, 5 min) and the collected erythrocyte cells were washed with PBS several times to remove serum and unwanted cells. Then, the collected erythrocyte cells were mixed with 10 mL of ultrapure water and kept statically at 4°C for 1 h to fully release the components contained in the erythrocyte cells such as hemoglobin, and then washed several times with ultrapure water until the supernatant was colorless and transparent. Subsequently, 10 mg of DSPE-PEG-FA was added to the erythrocyte membrane solution and stirred for 12 h. Finally, DSPE-PEG-FA-modified red blood cell membranes (FM) were collected by centrifugation (2000 rpm, 5 min).^33–34

The preparation process of FM@IQ/PST&ZIF-8/DOX was carried out according to the relevant references with slight modifications.³⁵ Firstly, the collected FM was resuspended in 1 mL of PBS solution and the above dispersion was added to the FM@IQ/PST&ZIF-8/DOX dispersion. After stirring for 24 h, the precipitate was collected by centrifugation and washed several times with PBS until the supernatant was colorless and transparent. Finally, it was freeze-dried and stored at -20°C for future use.

2.2 Cell Culture and Fluorescence Imaging

RAW264.7 cells, 4T1 cells and GES-1 cells were respectively placed in culture dishes containing RPMI 1640 medium, and 10% fetal bovine serum, 100 U/mL penicillin and 100 U/mL streptomycin were added to the above culture dishes. Subsequently, all cell lines were cultured in an environment of 37°C (containing 5% CO₂).

Immune clearance method: RAW264.7 cells were respectively inoculated in confocal culture dishes (1×10⁴) and placed in a cell culture incubator (37°C, 5% CO₂). After 12 h, IQ/PST&ZIF-8/DOX, M@IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX nanoplatform were respectively added to the above culture dishes. After 3 h, the supernatant was discarded and DAPI staining solution was added. After 15 min, the staining solution was discarded and the fluorescence intensity of each treatment group was observed by confocal laser scanning microscope (CLSM). ³⁶

Targeted uptake: 1×10⁴ 4T1 cells and GES-1 cells were respectively inoculated in cell culture dishes and placed in a cell culture incubator (37°C, 5% CO₂). After 12 h, FM@IQ/PST&ZIF-8/DOX nanoplatform was respectively added to the above culture dishes. After 3 h, the supernatant was discarded and fixed with 4% paraformaldehyde, then DAPI staining solution was added and washed 3 times with PBS. Finally, the fluorescence intensities of 4T1 cells and GES-1 cells were observed by CLSM. ³⁷

2.3 In vitro verification of the environmental response release performance of FM@IQ/PST&ZIF-8/DOX

To study the release behavior of DOX from FM@IQ/PST&ZIF-8/DOX. Firstly, 100 mg of FM@IQ/PST&ZIF-8/DOX was respectively immersed in in vitro simulated normal physiological environments (pH = 7.4), pH = 5.5, 10 mM glutathione (GSH), 30 µM hydrogen peroxide (H₂O₂), and simulated tumor microenvironment (TEM, pH = 5.5, 10 mM GSH, 30 µM H₂O₂). The FM@IQ/PST&ZIF-8/DOX dispersions in the above different environments were placed in a horizontal shaker and incubated at 37°C at a rotational speed of 300 rpm/min. At the designed different time points, the environmental response release behavior of DOX was determined using a fluorescence spectrometer. ^38–39

2.4 Photothermal Conversion Performance of FM@IQ/PST&ZIF-8/DOX

To evaluate the photothermal conversion performance of FM@IQ/PST&ZIF-8/DOX. Firstly, 100 µl of FM@IQ/PST&ZIF-8/DOX dispersion with different concentrations (100 and 200 µg/mL) were placed in Eppendorf tubes respectively and then irradiated under different powers of NIR (0.5, 0.75 and 1.0 W/cm²) for 2 min. The temperature changes of different treatment groups were recorded in real time by an infrared thermal imaging instrument and the corresponding temperature change graphs were plotted. ^40–41

To determine the photothermal conversion efficiency (η) of the FM@IQ/PST&ZIF-8/DOX dispersion, the 200 µg/mL FM@IQ/PST&ZIF-8/DOX dispersion was placed in an Eppendorf tube and exposed under NIR irradiation with a power of 0.75 W/cm² for 600 s. Then, the NIR excitation was turned off and the FM@IQ/PST&ZIF-8/DOX dispersion was allowed to cool naturally for 600 s. The temperature changes of the FM@IQ/PST&ZIF-8/DOX dispersion were recorded in real time by an infrared thermal imaging instrument. The photothermal conversion efficiency (η) of the FM@IQ/PST&ZIF-8/DOX dispersion is as follows: ^42–44

θ = (T - T_min) / (T_max - T_min) (1)

hs = - m*Cp/ζ (2)

η = hs (ΔT_max,mix - ΔT_max,H2O) /I (1 − 10^− A808) (3)

θ is the dimensionless driving force temperature, defined as the ratio of (T - T_min) to (T_max - T_min). ζ is the slope of t and -ln θ. Therefore, m and Cp of nanoplatform are ignored. M is 2 × 10^− 4 kg. Cp is 4.2 × 10³ J/(kg·℃). ΔT_max, mix is the temperature change of FM@IQ/PST&ZIF-8/DOX at the highest steady-state temperature. ΔT_max, H₂O is the temperature change of water at the highest steady-state temperature. I is the laser power and A₈₀₈ is the ultraviolet absorbance value of FM@IQ/PST&ZIF-8/DOX at the wavelength of 808 nm.

2.5 Release of tumor antigens induced by FM@IQ/PST&ZIF-8/DOX

4T1 cells (2 × 10⁵/well) were inoculated in 24-well culture plates. After 12 h, they were co-incubated with FM@IQ/PST&ZIF-8/DOX and placed under NIR (0.75 W/cm², 2 min). Subsequently, they were incubated with anti-calreticulin Alexa Fluor 594 conjugate for 1 h. 4T1 cells were washed with PBS three times and then the fluorescence signals of calreticulin in each treatment group were detected by CLSM. The secretion of HMGB1 by 4T1 cells was detected by enzyme-linked immunosorbent assay of high mobility group protein B1 (HMGB1).^45–46

2.6 Construction of subcutaneous transplanted tumor model of 4T1 mice

5×10⁶ 4T1 cells were injected subcutaneously into the lower right mammary gland of female BALB/c mice to construct the subcutaneous transplanted tumor model. When the tumors grew to approximately ~ 100 cm³, the 4T1 transplanted tumor mice were randomly divided into 6 groups (n = 6/group), and 200 µL PBS, 200 µL DOX, 200 µL IQ, 200 µL PST&ZIF-8/DOX, 200 µL IQ/PST&ZIF-8/DOX and 200 µL FM@IQ/PST&ZIF-8/DOX were injected via the tail vein respectively. Subsequently, the mice in each treatment group were placed under NIR (0.75 W/cm², 2 min). Each group was injected via the tail vein on the 1st, 3rd, 6th, 9th, 12th and 15th days respectively. The temperature changes of tumor tissues were monitored by a thermal imaging camera. After 15 days of treatment, the mice were sacrificed by cervical dislocation for further study. The tumor volume changes of each mouse were measured every 3 days and the calculation formula was: volume = width² × length/2.⁴⁷

5×10⁶ 4T1 cells were injected subcutaneously into the right lower mammary gland of female BALB/c mice as primary tumors. When the primary tumors grew to approximately 100 mm³, the mice were randomly divided into 6 groups (n = 6/group). Subsequently, 0.5×10⁶ 4T1 cells were injected on the left side to establish the distant tumor model. PBS, 200 µL DOX, 200 µL IQ, 200 µL PST&ZIF-8/DOX, 200 µL IQ/PST&ZIF-8/DOX and 200 µL FM@IQ/PST&ZIF-8/DOX were injected every 3 days. Then, the primary tumors of each group of mice were exposed to NIR (0.75 W/cm², 2 min). After 15 days of treatment, the inguinal lymph nodes of the mice were collected, mechanically ground and suspended with PBS. Subsequently, they were stained with anti-mouse CD11c, anti-mouse CD80 and anti-mouse CD86 to detect the maturation of dendritic (DC) cells in the inguinal lymph nodes. To observe the infiltration of T cells in tumor tissues, the collected cells were stained with CD3, CD8a, CD44 and CD62L, and CD3, CD4 as well as CD8a, and the expression of memory T cells and cytotoxic T lymphocytes was analyzed by flow cytometry.^48–49 And the animal study is reported in accordance with ARRIVE guidelines.

2.7 Analysis of T cells in tumor tissues

The distant tumors of 4T1 transplanted tumors in each treatment group were taken, minced and digested with Dulbecco's Modified Eagle Medium containing DNase I (100 µg/mL), hyaluronidase (100 µg/mL), type IV collagenase (1 mg/mL) and 10% fetal bovine serum at 37°C and 200 rpm with continuous shaking for 40 min. Then, the red blood cell lysis solution and 40% percoll solution were used for purification. The extracted lymphocytes were collected and stained with CD3, CD4 and CD8a for flow cytometry analysis.^50–51

2.8 Histological analysis

After 15 days of treatment, all the major organs (heart, spleen, liver, lung, and kidney) and tumor tissues of the treatment group mice were collected and immersed in 4% paraformaldehyde buffer. After 24 hours, they were embedded in paraffin. Hematoxylin and eosin (H&E) staining, terminal deoxynucleotidyl transferase-mediated nick end labeling (TUNEL) staining, Cell proliferation staining (Ki67), CD8⁺T cells and CD31 were performed.^52–53

2.9 Statistical analysis

Experimental data were analyzed using OriginPro and SPSS 17.0. All experimental data were repeated at least three times and the results were recorded as the mean ± standard deviation. Statistical analysis was performed using the t-test. A difference was considered statistically significant at p < 0.05. * p < 0.05, ** p < 0.01, *** p < 0.001.

3.1 Physical characterization of FM@IQ/PST&ZIF-8/DOX nanoplatform

The study found that the organic compound 2-methylimidazole and Zn²⁺ ions can successfully construct a ZIF-8 drug carrier with a large specific surface area and environmental response properties through a one-step method for the loading of anti-tumor drugs.³⁰ Therefore, in this study, 2-methylimidazole, DOX and Zn²⁺ were used to successfully construct the ZIF-8/DOX anti-tumor drug carrier through a one-step method. Transmission electron microscopy (TEM) results showed (Fig. 1b) that the structure of ZIF-8/DOX did not change significantly compared with ZIF-8 (Fig. 1a). During this process, DOX was encapsulated into the ZIF-8 nanocarrier through the chelation effect with Zn²⁺ and the π-π stacking effect with 2-methylimidazole.³¹ BET results showed (Fig. 1f) that the specific surface area of the prepared ZIF-8 is 442.3 m²/g, which is suitable for the loading of the anti-tumor drug DOX. XPS results showed that before and after the loading of DOX, the elemental composition of ZIF-8 and ZIF-8/DOX did not change significantly and both were composed of C, N, O and Zn elements (Fig. 1j and 1k). Fluorescence spectroscopy showed (Fig. 1l) that the loading efficiency of DOX is as high as 44.2%. To avoid the leakage of DOX due to the blood flow during the transportation of ZIF-8/DOX, a layer of polyserotonin shell (PST&ZIF-8/DOX) was formed on the surface of ZIF-8/DOX by taking advantage of the property that serotonin is prone to oxidative polymerization under alkaline conditions.⁵⁴ As shown in the Fig. 1g and 1h, the particle size increased from 40 nm (ZIF-8/DOX) to 60 nm (PST&ZIF-8/DOX) and the potential decreased to -7.5 mV (PST&ZIF-8/DOX). To improve the immunosuppressive microenvironment of tumor tissues, the small molecule immune modulator-IQ was loaded by using the adsorption performance of PST. When IQ was successfully adsorbed on the surface of PST&ZIF-8/DOX nanoparticles through electrostatic adsorption and π-π stacking (Fig. 1g and 1h), the particle size increased from 60 nm (PST&ZIF-8/DOX) to 65 nm (IQ/PST&ZIF-8/DOX) and the potential increased to -3.6 mV (IQ/PST&ZIF-8/DOX). And the TEM results showed that the shape of IQ/PST&ZIF-8/DOX did not change significantly (Fig. 1c).⁵⁵ However, the particle size of IQ/PST&ZIF-8/DOX is similar to that of viruses, which is prone to trigger the immune response of the body, thereby causing IQ/PST&ZIF-8/DOX nanoplatform to be cleared by the mononuclear system of the body. To prolong its circulation cycle in the body and enhance its phagocytosis by tumor cells, folic acid-modified erythrocyte membranes (FM) were used to encapsulate IQ/PST&ZIF-8/DOX nanoplatform. When FM was successfully encapsulated, the particle size of IQ/PST&ZIF-8/DOX increased from 60 nm (IQ/PST&ZIF-8/DOX) to 75 nm (FM@IQ/PST&ZIF-8/DOX) and the potential dropped to -22.4 mV (FM@IQ/PST&ZIF-8/DOX). Moreover, the TEM results showed (Fig. 1d) that the surface of FM@IQ/PST&ZIF-8/DOX was wrapped by a light coat. The XRD results showed (Fig. 1e) that during the synthesis of FM@IQ/PST&ZIF-8/DOX, its lattice structure did not change significantly. Fourier transform infrared (FTIR) spectra results further verified that the peaks at 3138 cm^− 1, 2933 cm^− 1 and 1580 cm^− 1 all corresponded to the -CH₃, C-H and C = N bonds of dimethylimidazole (Figure S1a). In addition, the peak position of DOX completely matched that of FM@IQ/PST&ZIF-8/DOX. The gel electrophoresis results showed that the protein composition of FM@IQ/PST&ZIF-8/DOX had a good match with pure erythrocyte membranes (EM), indicating that the folic acid-modified erythrocyte membrane (FM) was successfully fused into IQ/PST&ZIF-8/DOX (Fig. 1i). Furthermore, UV–vis absorption further verified that FM@IQ/PST&ZIF-8/DOX was successfully prepared and had a broad absorption peak at 808 nm (Figure S1b). X-ray powder diffraction (XRD) results showed that the elemental composition of the prepared FM@IQ/PST&ZIF-8/DOX did not change compared with ZIF-8/DOX, but only the elemental content changed (Fig. 1m). In particular, the content of Zn element decreased from 26.28–13.81%, which might be related to the introduction of PST. The above results demonstrated that the FM@IQ/PST&ZIF-8/DOX drug carrier was successfully constructed.

3.2 Biological performance of FM@IQ/PST&ZIF-8/DOX

Because the size of FM@IQ/PST&ZIF-8/DOX is similar to that of viruses, it is prone to cause immune responses in the body during its circulation process, resulting in premature elimination of FM@IQ/PST&ZIF-8/DOX by the body immune system. Therefore, for FM@IQ/PST&ZIF-8/DOX as an anti-tumor drug carrier, effectively avoiding elimination by the mononuclear system of the body during its circulation in vivo is a prerequisite for achieving efficient anti-tumor effects. Studies have found that nanoparticles wrapped by cell membranes can effectively avoid their elimination by the body's immune system.^28–29 Therefore, to verify the "stealth" performance of folic acid-modified erythrocyte membranes (FM) on FM@IQ/PST&ZIF-8/DOX. M@IQ/PST&ZIF-8/DOX, FM@IQ/PST&ZIF-8/DOX and PST&ZIF-8/DOX were co-incubated with RAW264.7 cells. After 3 hours, the phagocytosis of the above drug carriers by RAW264.7 cells was observed by CLSM. In Fig. 2a, when PST&ZIF-8/DOX was co-incubated with RAW264.7 cells, a strong fluorescence signal could be detected. However, when M@IQ/PST&ZIF-8/DOX was co-incubated with RAW264.7 cells, the fluorescence signal of DOX was very weak and the fluorescence signal could not even be detected in some cells. However, when the surface of erythrocyte membranes was modified by folic acid molecules, the fluorescence signal of DOX in RAW264.7 cells recovered to some extent. The above results indicated that erythrocyte membrane wrapping has a certain "stealth" performance for PST&ZIF-8/DOX, but the "stealth" performance of FM@IQ/PST&ZIF-8/DOX is affected to some extent after modification by folic acid molecules. However, comparing with PST&ZIF-8/DOX, FM@IQ/PST&ZIF-8/DOX can effectively avoid it being phagocytosed by RAW264.7 cells. Therefore, the wrapping of folic acid-modified erythrocyte membranes can effectively prevent PST&ZIF-8/DOX from eliminated by the body's immune system.

Furthermore, the efficient uptake of anti-tumor drug molecules by tumor cells is the key to achieving efficient anti-tumor effects. Therefore, 4T1 cells and GES-1 cells were respectively co-incubated with FM@IQ/PST&ZIF-8/DOX. After 3 hours, the fluorescence intensity of DOX in the two types of cells was observed using CLSM to evaluate whether FM@IQ/PST&ZIF-8/DOX could be efficiently taken up by tumor cells. In the Fig. 2b, when GES-1 cells were co-incubated with FM@IQ/PST&ZIF-8/DOX, the DOX fluorescence signal in GES-1 cells was weak. However, when 4T1 cells were co-incubated with FM@IQ/PST&ZIF-8/DOX, the fluorescence signal in 4T1 cells significantly enhanced, approximately three times that in GES-1 cells. This result indicated that FM@IQ/PST&ZIF-8/DOX has a strong affinity for 4T1 cells, which mainly attributed to the fact that the folate receptor on the surface of 4T1 cells can specifically bind to the folic acid molecules on the surface of FM@IQ/PST&ZIF-8/DOX, thereby increasing the uptake of 4T1 cells to it.⁵⁶ The above results showed that FM@IQ/PST&ZIF-8/DOX can effectively avoid being cleared by the body's immune system and can be efficiently taken up by tumor cells.

3.3 Environmental Responsive Performance of FM@IQ/PST&ZIF-8/DOX

As an anti-tumor drug carrier, the environmental responsive release of FM@IQ/PST&ZIF-8/DOX nanoplatform is the key to achieving precise tumor treatment. Therefore, FM@IQ/PST&ZIF-8/DOX was immersed in in vitro simulated normal physiological environment (pH = 7.4), acidic environment (pH = 5.5), high concentration H₂O₂ (30 µM), GSH (10 mM) environment and in vitro simulated TME (pH = 5.5, 10 mM GSH and 30 µM H₂O₂) to verify the environmental responsive release performance of DOX. As shown in Fig. 3a, when FM@IQ/PST&ZIF-8/DOX was immersed in the normal physiological environment, only 5.6% of DOX was released from the surface of FM@IQ/PST&ZIF-8/DOX after 24 hours, which was mainly due to the fact that some DOX was not completely loaded into ZIF-8, causing the release of DOX.⁵⁶ However, when FM@IQ/PST&ZIF-8/DOX was immersed in H₂O₂ (30 µM) and GSH (10 mM) environments respectively, the release rates of DOX were 37.2% and 42.9%, respectively. This was mainly attributed to the accumulation of H₂O₂ on the surface of the erythrocyte membrane, which enlarged the pore size of the erythrocyte membrane, promoted the direct contact of H₂O₂ with IQ/PST&ZIF-8/DOX and further promoted the release of DOX.⁵⁷ When FM@IQ/PST&ZIF-8/DOX was immersed in the GSH environment, GSH could undergo a redox reaction with PST, resulting in the agglomeration of the PST shell and ultimately the release of the loaded DOX. However, when FM@IQ/PST&ZIF-8/DOX was immersed in the acidic environment with pH = 5.5, the release efficiency of DOX was up to 90%. To further explore the release mechanism of FM@IQ/PST&ZIF-8/DOX in the acidic environment, TEM (Fig. 3b) results showed that the framework structure of FM@IQ/PST&ZIF-8/DOX collapsed and the XPS (Fig. 3c) results showed that after FM@IQ/PST&ZIF-8/DOX was immersed in the in vitro simulated TME, the content of zinc element decreased from the original 13.81–1.19%. The above results indicated that FM@IQ/PST&ZIF-8/DOX is prone to cause the collapse of the framework structure in the acidic environment, release Zn²⁺ and further promote the release of DOX, which is consistent with the previous report that ZIF-8 was easily degraded in the acidic environment.³⁰ When FM@IQ/PST&ZIF-8/DOX was immersed in the in vitro simulated TME, DOX was completely released at 20 hours. Therefore, after FM@IQ/PST&ZIF-8/DOX was immersed in the TME, it could achieve rapid and precise release of DOX.

In addition, the UV–vis absorption results showed that FM@IQ/PST&ZIF-8/DOX exhibits superior absorption performance near 808 nm, which prompts us to further explore the photothermal conversion performance of FM@IQ/PST&ZIF-8/DOX under NIR excitation. Therefore, FM@IQ/PST&ZIF-8/DOX dispersion with different concentrations (100 µg/mL and 200 µg/mL) were placed under different powers of NIR (0.5, 0.75 and 1.0 W/cm²) respectively. Subsequently, the temperature changes of each treatment group were recorded in real time by an infrared thermal imaging instrument (Fig. 3d) and the corresponding temperature change graphs were drawn (Fig. 3e). The above results showed that FM@IQ/PST&ZIF-8/DOX has superior photothermal conversion performance and its photothermal conversion performance is positively correlated with irradiation time, power and dispersion concentration. When the concentration of FM@IQ/PST&ZIF-8/DOX dispersion is 200 µg/mL and it exposed under NIR of 0.75 W/cm² for 2 min, the temperature rises to 50.5°C. There is no significant difference from the rising temperature (51.2°C) of IQ/PST&ZIF-8/DOX dispersion under the same condition. Therefore, FM has no significant effect on the photothermal conversion performance of FM@IQ/PST&ZIF-8/DOX and the photothermal conversion efficiency of FM@IQ/PST&ZIF-8/DOX dispersion is up to 42.9% (Fig. 3f), which is superior to other photothermal materials.⁵⁸ To further verify whether FM@IQ/PST&ZIF-8/DOX can be reused multiple times, the FM@IQ/PST&ZIF-8/DOX dispersion was placed under NIR (0.75 W/cm², 2 min) and irradiated repeatedly for 4 times. The photothermal conversion performance of FM@IQ/PST&ZIF-8/DOX did not decrease and the temperature increased after each irradiation, eventually reaching 51.2°C (Fig. 3g). This is mainly due to the evaporation of water after each irradiation, which in turn increaseed the photothermal conduction performance of the FM@IQ/PST&ZIF-8/DOX dispersion.⁵⁶

The superior environmental response performance of FM@IQ/PST&ZIF-8/DOX prompts us to further explore the killing effect of FM@IQ/PST&ZIF-8/DOX combined with NIR on tumor cells. 4T1 cells and GES-1 cells were respectively co-incubated FM@IQ/PST&ZIF-8/DOX with different concentrations and placed under 0.75 W/cm² NIR for 2 minutes. As the Fig. 3h and 3i shown, with the increase of the dispersion concentration, the survival rate of cells in each treatment group decreased significantly. When the concentration of FM@IQ/PST&ZIF-8/DOX reached 200 µg/mL, the survival rate of 4T1 cells was only 18.2% while that of GES-1 cells remained at 51.3%. And at the same concentration, the survival rate of 4T1 cells was significantly lower than that of GES-1 cells. This is mainly attributed to the folic acid molecules on the surface of FM@IQ/PST&ZIF-8/DOX, which can bind to the folic acid receptors on the surface of tumor cells, thereby enhancing the uptake of it by tumor cells and releasing the loaded DOX according to the special tumor TME. However, after treatment with DOX, the mortality rate of GES-1 cells was significantly higher than that of 4T1 cells under the same conditions. Therefore, FM@IQ/PST&ZIF-8/DOX can effectively avoid the toxic and side effects of DOX on normal cells GES-1 and can effectively kill 4T1 cells.

3.4 NIR-triggered tumor antigen releasing

According to relevant literature reports, photothermal ablation can induce immunogenic cell death of tumor cells, thereby promoting tumor cell apoptosis as well as the release of tumor-associated antigen (TAA) and damage associated molecular patterns, mainly including high mobility group box 1 protein, ATP and calreticulin.^45–46 These molecular patterns can serve as "find me" signals, thereby promoting the maturation of DC cells. For example, calreticulin exposed on the surface of apoptotic tumor cells can act as an "eat me" signal, effectively promoting the phagocytosis and antigen processing of DC cells.^47–48 Therefore, 4T1 cells were co-incubated with FM@IQ/PST&ZIF-8/DOX and placed under NIR (0.75 W/cm², 2 min). When 4T1 cells were co-treated with FM@IQ/PST&ZIF-8/DOX and NIR irradiation, the red fluorescence signal of calreticulin on the cell membrane surface significantly enhanced, approximately three times that of the FM@IQ/PST&ZIF-8/DOX treatment group (Fig. 4a). And the contents of ATP and high mobility group B1protein were 2.45 times and 1.58 times that of the FM@IQ/PST&ZIF-8/DOX treatment group respectively (Fig. 4b and 4c). The above results indicated that under the excitation of NIR, FM@IQ/PST&ZIF-8/DOX can effectively induce immunogenic cell death of 4T1 cells and release a large amount of TAAs. Among them, DC cells, as the "sentinels" of the body's immune system, are responsible for initiating the body's anti-tumor immunity. ⁵⁰ Therefore, to explore whether FM@IQ/PST&ZIF-8/DOX combined with NIR can effectively promote the maturation of DC cells in vitro, FM@IQ/PST&ZIF-8/DOX was co-incubated with 4T1 cells and then co-incubated with DC cells for 24 hours. Compared with the PBS treatment group, all other treatment groups could effectively promote the maturation of DC cells. Among them, after treatment with FM@IQ/PST&ZIF-8/DOX, the maturation amount of DC cells was 3.01 times that of the PBS group (Fig. 4d). This is mainly attributed to the fact that FM@IQ/PST&ZIF-8/DOX can be efficiently taken up by 4T1 cells and release the loaded drugs according to the slightly acidic environment in the cytoplasm, further inducing apoptosis of 4T1 cells and continuously releasing TAA. The above results proved that FM@IQ/PST&ZIF-8/DOX combined with NIR can effectively induce apoptosis of 4T1 cells and release the "eat me" signals, thereby promoting their uptake by DC cells and ultimately inducing the maturation of DC cells.

3.5 Antitumor effect and immune mechanism in vivo of NIR-triggered FM@IQ/PST&ZIF-8/DOX

Based on the fact that FM@IQ/PST&ZIF-8/DOX can be effectively taken up by tumor cells and combined with NIR therapy to effectively inhibit the growth of tumor cells, it prompts us to further evaluate its therapeutic effect on tumors in vivo. It is shown by the small animal imaging instrument (Figure S2) that after FM@IQ/PST&ZIF-8/DOX was injected through the tail vein, a large amount of red fluorescent signals could be detected in the tumor tissue after 24 hours. The above results indicated that FM@IQ/PST&ZIF-8/DOX can be effectively targeted and delivered to the tumor tissue. Therefore, when FM@IQ/PST&ZIF-8/DOX was injected through the tail vein for 24 hours, the mice in each treatment group were respectively placed under NIR (0.75 W/cm², 2 min) and the temperature changes of the tumor tissue in mice were monitored in real time by an infrared thermal image. In the Fig. 5a and Fig. 5b, after the tumor tissues of PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX were treated with NIR, the tumor tissues increased significantly compared with the PBS, DOX and IQ groups. Especially after the FM@IQ/PST&ZIF-8/DOX was treated with NIR for 120 seconds, the temperature of the tumor tissue could rise to 53.4°C. The above results indicated that FM@IQ/PST&ZIF-8/DOX has targeted delivery performance and can efficiently accumulate in the tumor tissue, thereby rapidly increasing the local temperature of the tumor tissue. In the Fig. 5c, after the treatment with PBS and with NIR, tumor tissues continued to grow, showing that NIR irradiation alone could not inhibit tumor growth. In contrast, other treatments (DOX, IQ, PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX) could effectively inhibit tumor growth after NIR (0.75 W/cm², 2 min). 15 days later, all mice in the treatment groups were sacrificed and the tumors of each treatment group were collected. The combined treatment of FM@IQ/PST&ZIF-8/DOX and NIR showed excellent tumor suppression effect and the average tumor volume was only 254.6 mm³ (Fig. 5e and 5d). And after 40 days of treatment, the mice with 4T1 transplanted tumors in all treatment groups mostly died, but after the combination treatment of FM@IQ/PST&ZIF-8/DOX and NIR, the survival rate of mice still remained at 50% (Fig. 5f). The above results demonstrated that the combined treatment of FM@IQ/PST&ZIF-8/DOX and NIR shows excellent anti-tumor effect and can effectively prolong the survival cycle of mice.

Subsequently, the tumor tissues of each treatment group were collected to further explore the anti-tumor mechanism of FM@IQ/PST&ZIF-8/DOX + NIR. The results of H&E staining showed that after the treatment of FM@IQ/PST&ZIF-8/DOX + NIR, widespread karyopyknosis, karyolysis, and vacuolization were observed in the tumor cells of the tumor tissues (Fig. 6a). The results of TUNEL staining further confirmed that a large number of apoptotic and necrotic tumor cells (green fluorescence) could be detected in the tumor tissues after the treatment of FM@IQ/PST&ZIF-8/DOX + NIR (Fig. 6b). In addition, the therapeutic effect of FM@IQ/PST&ZIF-8/DOX + NIR was further evaluated by observing the cell proliferation marker Ki67. The results showed that after the combined treatment of FM@IQ/PST&ZIF-8/DOX + NIR, the expression level of Ki67 in the tumor tissues significantly reduced (Fig. 6c), which was consistent with the results of H&E and TUNEL staining. As a small molecule immunomodulator, IQ can effectively regulate the immunosuppressive microenvironment of tumors, thereby promoting the infiltration of immune cells.²⁰ The results of in vitro experiments showed that FM@IQ/PST&ZIF-8/DOX + NIR can effectively kill tumor cells and release TAA, thereby promoting the maturation of DC cells. As the primary antigen-presenting cells, DC cells can effectively activate CD8⁺ T cells, which in turn kill tumor cells. Observations through immunofluorescence staining indicated that FM@IQ/PST&ZIF-8/DOX + NIR treatment can significantly promote the infiltration of CD8⁺ T cells into tumor tissues, leading to the destruction of tumor cells (Fig. 6d). The study found that tumor cell growth requires a substantial supply of nutrients. Next, from the perspective of vascular damage, the study will verify the feedback interaction between vascular damage and tumor cells in vivo.⁵⁰ Through CD31 immunofluorescence staining (endothelial cell marker), the changes in tumor vasculature after the combined treatment of FM@IQ/PST&ZIF-8/DOX + NIR were elucidated. After the 4T1 tumor-bearing mice underwent the FM@IQ/PST&ZIF-8/DOX + NIR combined treatment (Fig. 6e), the red fluorescence in the tumor tissue exhibited a discontinuous distribution, indicating the complete integrity of the blood vessels within the tumor tissue. However, after treatments with PBS + NIR, DOX + NIR, IQ + NIR, PST&ZIF-8/DOX + NIR and IQ/PST&ZIF-8/DOX + NIR, the damage to the tumor vasculature was not severe, with some vessels in treatment groups were almost intact. The above results suggested that the apoptosis of tumor cells, immune cell infiltration, and vascular destruction induced by the FM@IQ/PST&ZIF-8/DOX + NIR combined treatment are closely interdependent with the FM-mediated targeted delivery.

Because lymph nodes are important immune organs of the body, they can effectively stimulate the body's anti-tumor immunity, thereby effectively inhibiting the metastasis and recurrence of tumor cells.⁵⁹ Subsequently, through the 4T1 transplanted tumor model, the expression of immune cells in the inguinal lymph nodes were analyzed to explore the immunomodulatory effect of FM@IQ/PST&ZIF-8/DOX. According to relevant literature reports, CD8⁺ T cells are the main immune cells that limit tumor development. The successful induction of CD8⁺ T cells requires the activation of immature DC cells into mature DC cells. In the Fig. 7a, after the treatment of FM@IQ/PST&ZIF-8/DOX, the proportion of matured cells (CD80⁺/CD86⁺) in inguinal lymph nodes was higher than that of other treatment groups (DOX, IQ, PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX). Moreover, the proportion of matured cells in the FM@IQ/PST&ZIF-8/DOX treatment group was 1.2 times higher than that in the IQ/PST&ZIF-8/DOX treatment group, which was mainly attributed to the targeted delivery performance of IQ/PST&ZIF-8/DOX. Among them, CD8⁺ T cells play an important role in the anti-tumor immune response, which can be activated by tumor-derived antigens and then directly kill tumor cells. Therefore, the expression level of CD8⁺ T cells in the inguinal matured cells was further analyzed. As shown in Fig. 7b, after treatments with PBS, DOX, IQ, PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX, the percentages of CD8⁺ T cells in 4T1 transplanted tumor mice were 11.2%, 14.0%, 14.6%, 14.3%, 19.9% and 28.2% respectively. Among them, after treatment with FM@IQ/PST&ZIF-8/DOX, the expression level of CD8⁺ T cells was the highest. In addition, the high expression of memory T cells can effectively achieve a continuous and long-lasting anti-tumor immunity in the body. Subsequently, the induction effect of FM@IQ/PST&ZIF-8/DOX treatment on memory T lymphocytes (CD44⁺CD62L⁻CD3⁺CD8a⁺) in lymph nodes were further verified. It is demonstrated in Fig. 7c after treatment with FM@IQ/PST&ZIF-8/DOX, the proportion of memory T lymphocytes was approximately 2.39 times that of the PBS group. These results indicated that FM@IQ/PST&ZIF-8/DOX, as a potential tumor-targeting carrier, can significantly activate the body's immune system, promoting the maturation of DC cells, the expression of CD8⁺ T cells and the activation of memory T lymphocytes.

3.6 Mechanism of long-term anti-tumor effect in vivo induced by FM@IQ/PST&ZIF-8/DOX

Since the treatment of FM@IQ/PST&ZIF-8/DOX combined with NIR (0.75 W/cm², 2 min) can effectively inhibit the growth of transplanted tumors in mice and promote the expression of immune cells related to inguinal lymph nodes in 4T1 transplanted tumor mice. It is expected to further explore whether treatment of FM@IQ/PST&ZIF-8/DOX combined with NIR can effectively prevent tumor recurrence. 4T1 cells were inoculated subcutaneously on the right side of mice to construct a primary tumor model and then 4T1 cells were inoculated on the left side of mice to simulate the distant recurrence tumor model. After 7 days, the 4T1 transplanted tumor models were randomly divided into 6 groups (n = 6/group). PBS, DOX, IQ, PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX were injected respectively through the tail vein of mice. After 24 hours injection, the mouse in each treatment group was placed under NIR (0.75 W/cm², 2 min) irradiation, respectively. Except PBS treatment group, the other treatment groups showed a certain degree of inhibitory effect on the primary transplanted tumor and the distant simulated tumor. Especially, the treatment of FM@IQ/PST&ZIF-8/DOX combined with NIR could effectively inhibit the growth of the primary inhibitory tumor and the distant simulated tumor to some certain extent (Fig. 8a). After the treatment, the average volume of the distal tumor was only 76.3 mm³ (Fig. 8b and 8c). And after the treatment with FM@IQ/PST&ZIF-8/DOX, the mental state of 4T1 transplanted tumor mice remained good and their body weight did not significantly decrease (Fig. 8d). Since the combined treatment of FM@IQ/PST&ZIF-8/DOX + NIR can effectively increase the content of memory T cells in the inguinal lymph nodes, after the treatment ended, tumor tissues from each treatment group were collected to analyze the infiltration of CD8⁺ T cells in the tumor tissues and further clarify the immunomodulatory mechanism of FM@IQ/PST&ZIF-8/DOX (Fig. 8e). Compared with the PBS treatment group, after the 4T1 transplanted tumor mice were treated with DOX, IQ, PST&ZIF-8/DOX, IQ/PST&ZIF-8/DOX and FM@IQ/PST&ZIF-8/DOX, the expression of CD8⁺ T cells in the distant tumor tissues of each treatment group increased. And after the treatment with FM@IQ/PST&ZIF-8/DOX, the content of CD8⁺ T cells in the distal tumor tissue increased significantly, which was 2.38 times that of the PBS treatment group. In conclusion, FM@IQ/PST&ZIF-8/DOX can effectively activate the body's immune system and prevent the recurrence and metastasis of tumors.

3.7 Biocompatibility of the FM@IQ/PST&ZIF-8/DOX nanoplatform

Since the combined therapy of FM@IQ/PST&ZIF-8/DOX + NIR can effectively inhibit the growth and recurrence of tumors, the premise for its application in mouse tumor treatment is that it is low-toxic or even non-toxic to the organism. Therefore, the main organs (heart, liver, spleen, lung and kidney) of mice in each treatment group were collected for H&E staining and hematological examination to analyze the biocompatibility of FM@IQ/PST&ZIF-8/DOX. After 15 days of treatment with FM@IQ/PST&ZIF-8/DOX, compared with the PBS treatment group, no obvious inflammation or tissue damage was observed in the main organs of mice. At the same time, FM@IQ/PST&ZIF-8/DOX could effectively alleviate the toxic and side effects of DOX and IQ on the organism during the treatment process, especially reducing the damage of DOX to the mouse heart tissue (Figure S3). Subsequently, the blood of 4T1 transplanted tumors was collected for blood routine and biochemical examinations on day 0, 1, 7 and 14 of FM@IQ/PST&ZIF-8/DOX + NIR treatment, whose results showed that during the treatment with FM@IQ/PST&ZIF-8/DOX, the blood routine and related biochemical indicators of mice did not fluctuate significantly (Figure S4). The above results indicated that FM@IQ/PST&ZIF-8/DOX, as a drug carrier, shows superior biocompatibility during the tumor treatment process.

In conclusion, a multifunctional drug delivery system FM@IQ/PST&ZIF-8/DOX, which integrates immune escape, tumor targeting and environmental response properties, is successfully constructed in this study. FM@IQ/PST&ZIF-8/DOX, with the help of folic acid-modified erythrocyte cells membrane, can not only effectively avoid it being cleared by the body's mononuclear system, but also achieve targeted delivery to tumor tissues and be efficiently taken up by tumor cells. When excited by NIR light, it can induce apoptosis of tumor cells and release tumor-associated pattern molecules and TAA, increase the uptake of DC cells and promote the maturation of DC cells, and activate T cells to generate a continuous anti-tumor immune response, thus effectively killing tumor cells and preventing tumor cell metastasis. In addition, the slightly acidic TME can cause the framework structure of FM@IQ/PST&ZIF-8/DOX nanoplatform to collapse, thereby achieving precise and continuous release of drugs in tumor tissues. While effectively avoiding the toxic side effects of monomeric drug molecules on the body, IQ is used to regulate the immunosuppressive microenvironment of tumor tissues and promote the infiltration of immune cells in tumor tissues to kill tumor cells. Therefore, under the excitation of NIR, the FM@IQ/PST&ZIF-8/DOX drug delivery system can achieve a combined treatment of chemotherapy/photothermal therapy/immunotherapy, effectively compensating for the deficiencies of individual treatments, greatly improving the anti-tumor effect and providing ideas for the later development of more efficient, safer and smarter drug carriers.

Ethics approval and consent to participate

5-week-old BALB/c mice were purchased from Biological science and technology co., LTD (Zhenjiang, China) and feed in specific pathogen-free-conditions. All experimental procedures were approved by the Institutional Animal Care and Use Committee of Jiangsu University. And the study is reported in accordance with ARRIVE guidelines.

Consent for publication

Each coauthor has read the manuscript and approves its submission. This work is being submitted exclusively to your journal.

Data Availability

The datasets supporting the results of this article are included within the article. All data generated or analysed during this study are included in this published article [and its supplementary information files].

The authors declared that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Funding

This research was supported by the “Jinshanyingcai Project of Zhenjiang City” (JSYC2022-008) and “Science and Technology Planning Social Development Project of Zhenjiang City” (FZ2023058).

Authors' contributions

Ying Wang and Qing ji are responsible for the original draft, experimental operations, data collection and analysis. Chao Yan are responsible for the date analysis. Ji Pang are responsible for the experimental design and writing of the manuscript. All authors read and approved the final manuscript.

Acknowledgements

The acknowledged are included within the article.

Conflicts of interest

The authors declare no conflict of interest.

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Scheme 1 is available in the Supplementary Files section.

No competing interests reported.

Supplement.docx
floatimage1.png
Scheme 1. (a) The schematic illustration of preparation process of FM@IQ/PST&ZIF-8/DOX. (b) The mechanism of FM@IQ/PST&ZIF-8/DOX in vivo tumor therapy.

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You are reading this latest preprint version

Biomimetic intelligent nanoplatform with cascade amplification effect for tumor synergy therapy

Status:

Version 1

Abstract

Figures

1. Introduction

2. Experimental Section

2.1 Synthesis process of FM@IQ/PST&ZIF-8/DOX

2.2 Cell Culture and Fluorescence Imaging

2.4 Photothermal Conversion Performance of FM@IQ/PST&ZIF-8/DOX

2.5 Release of tumor antigens induced by FM@IQ/PST&ZIF-8/DOX

2.6 Construction of subcutaneous transplanted tumor model of 4T1 mice

2.7 Analysis of T cells in tumor tissues

2.8 Histological analysis

2.9 Statistical analysis

3. Results and Discussion

3.1 Physical characterization of FM@IQ/PST&ZIF-8/DOX nanoplatform

3.2 Biological performance of FM@IQ/PST&ZIF-8/DOX

3.3 Environmental Responsive Performance of FM@IQ/PST&ZIF-8/DOX

3.4 NIR-triggered tumor antigen releasing

3.7 Biocompatibility of the FM@IQ/PST&ZIF-8/DOX nanoplatform

4. Conclusion

Declarations

References

Scheme 1

Additional Declarations

Supplementary Files

Status:

Version 1