A. Preparation of monoclonal antibodies conjugated with magnetic particles and sperm
Control Sample
The monoclonal antibody reaction test with flow cytometer used in the screening of sperm sex was divided into two groups: the control sample test and its negative result (control and negative control, respectively) and a monoclonal antibody 1F9, which is an IgG antibody that binds to the H-Y antigen located on the surface of Y sperm-specific cells. The control samples were A01 and A02; A01 was the conjugate control (CC), which consisted of 50 µL of FACS buffer and 50 µL of bull sperm; A02 was isotype control (IC), which consisted of 1 µL of ST28A antibody, 50 µL of FACS buffer, and 50 µL of bull sperm. However, there is no specificity for the sperm that it should not bind to the sperm. The control samples A01 and A02 are collectively referred to as negative controls (NC). They probability of the population (P1) to analyze the results of the control sample (Control), which shows the probability of the relationship between forward scatter height (FSC-H) and side scatter height (SSC-H) is represented as a dot plot format with the probability of correlation between fluorescent light intensity (FL1-H) and number. The cell (Count) in the form of a histogram, is shown in Fig. 1.
Monoclonal Antibody 1F9
Comparison with the negative control sample revealed that the monoclonal antibody 1F9 affected the bindable sperm, as mentioned above. Negative controls are unable to bind to sperm. However, the positive results obtained with the 1F9 monoclonal antibody revealed that the 1F9 monoclonal antibody had the ability to bind to sperm, as shown in Fig. 2. A03 is a 1F9 monoclonal antibody at a concentration of 50 µg/mL, consisting of 100 µg/mL monoclonal antibody (50 µL). A04 is a 1F9 monoclonal antibody at a concentration of 25 µg/mL, consisting of 50 µL of 50 µg/mL monoclonal antibody and 50 µL of cow sperm. And A06 is a monoclonal antibody 1F9 at a concentration of 6.25 µg/ml, consisting of a monoclonal antibody at a concentration of 12.5 µg/ml of 50 µl and cow sperm of 50 µl.
Sperm preparation with the 1F9 monoclonal antibody at various concentrations, it yielded different results with the sperm test and the sperm test with the ST28A antibody yielding a negative (Negative) test showing that the sperm with the 1F9 monoclonal antibody bind together and at reduced concentrations. There is a tendency to catch each other down as well. The optimum concentration for sperm binding was A04 at a concentration of 25 µg/mL.
Preparation of monoclonal antibodies conjugated with magnetic particles
Magnetic beads (Pierce™ NHS-Activated Magnetic Beads; Thermo Scientific™) were used for the preparation of monoclonal antibodies conjugated with magnetic particles. Magnetic particles were prepared by balancing protein and magnetic particles at room temperature, and then 300 µL of magnetic particles were inserted into a 1.5 mL microcentrifuge tube. Next, the tubes were placed in a magnetic stand, the magnetic particles were collected, and the suspended solids were disposed. Ice-cold 1 mM hydrochloric acid (1 ml) was added to the tube and blended for 15 s. The tubes were placed in a magnetic stand, the magnetic particles were collected, and suspended solids were discarded. Then, 300 µL of protein solution (1 mg/mL in coupling buffer) was added to the tube and blended for 300 s. The tube was incubated for 2 h at room temperature on a rotary agitator. During the first 30 min of incubation, the mixture was mixed for 15 s every 5 min and then every 15 s every 15 min, until the curing was complete. The tube was then placed in the magnetic stand, the magnetic particles were collected, and the suspended solids were discarded. Then, 1 mL of 0.1 M glycine (pH 2) was added to the magnetic particles and mixed for 15 s, and the tubes were placed in the magnetic stand. The magnetic particles were collected, and the solution of suspended solids was discarded; this process was repeated once. Thereafter, 1 mL of ultrapure water was added to the magnetic particles and mixed for 15 s in the magnetic stand. The magnetic particles were collected, while the suspended solids were discarded. A 1 mL of 3 M ethanolamine (pH 9) was added to the magnetic particles, blended for 30 s, and incubated for 2 h at room temperature on a rotary agitator, and the tubes were placed in a magnetic stand. The magnetic particles were collected and the suspensions were discarded again. Subsequently, 1 mL of purified water was added and mixed well, the magnetic particles were collected with a magnetic stand and suspended solids were discarded before adding 1 mL of coupling buffer (50 M borate, pH 8.5) with 0.05% sodium azide and mixed well. The magnetic particles were collected with a magnetic stand, discarding the suspension, and the process was repeated two more times, with 300 µL of coupling buffer and 0.05% sodium azide, mixed well, and stored at 4°C until use. Finally, monoclonal antibodies conjugated with magnetic particles were rechecked by flow cytometry, as shown in Fig. 3.
From the flow cytometry test of the A07 sample, the test result was negative. The result of the A07 sample was used as a negative control sample for comparison with the A08 sample. The A08 sample is a GαM-FITC-dyed magnetic bead on a monoclonal antibody, as shown in Fig. 4. From the flow cytometry test of the A08 sample, the test was positive when comparing the negative result from the A07 sample, the magnetic bead and the monoclonal antibody matched each other. The compatibility was 94.54%, as shown in Table 1.
Table 1. Physical Characteristics of Magnetic Particle Beads on Monoclonal Antibody Stained with GαM-FITC (Plot 2)
Plot 2: A08 Beads+anti-sperm+ GαM-FITC
|
Count
|
Events/µL
|
% of This Plot
|
% of All
|
Mean FL1-H
|
CV FL1-H
|
All
|
11,931
|
5966
|
100.00%
|
100.00%
|
25,833.83
|
177.21%
|
V1-L (1.0/528.0)
|
652
|
326
|
5.46%
|
5.46%
|
144.73
|
78.39%
|
V1-R (528.0/16,777,215.0)
|
11,279
|
5640
|
94.54%
|
94.54%
|
27,318.83
|
170.78%
|
Monoclonal antibodies conjugated with magnetic particles and sperm
The Holstein Friesian bull semen samples used in this study were purchased from the Dairy Farming Promotion Organization of Thailand. A single straw of bull semen sample containing 30 × 106 spermatozoa preserved in liquid nitrogen was thawed in a water bath at 37°C for 40 s. Thereafter, the sample was placed into a 1.5 mL micro centrifuge tube and stored in a chamber at a temperature of 37°C. Live sperm with mortality greater than 70% was used. One microliter of warm PBS extender at 37°C was added to remove the egg yolk extender from the spermatozoa. Subsequently, a tube of sperm sample was centrifuged at 12,000 rpm for 10 s thrice, and the supernatant was discarded to collect the sperm pellet. Turk’s solution was mixed with sperm at a ratio of 1:10. Then, the sperm was blocked with AB serum (FC Receptor) for 30 min. Finally, a total of six sperm tubes were prepared: Tube 1, monoclonal antibody 100 µg/mL, 50 µL volume and 50 µL sperm. Tube 2, 50 µg/mL monoclonal antibody, 50 µL volume and 50 µL sperm. Tube 3, 25 µg/mL monoclonal antibody, 50 µL, and 50 µL sperm. Tube 4, 12.5 µg/mL monoclonal antibody, 50 µL volume, and 50 µL sperm. Tube 5, 1 µL ST28A antibody, 50 µL FACS buffer, and 50 µL sperm. Tube 6, 50 µL FACS Buffer, and 50 µL sperm.
B. Microfluidic Device Fabrication
The design of the microfluidic chip, which mainly consists of a Y channel cell microfluidic channel (Fig. 5a) with a pair of electrodes positioned at the separation regions is shown in Fig. 5b. The microfluidic chip was designed using a layout editor program. The dimensions of the microfluidic chip were 6,000 µm × 150 µm, and it was 50 µm in thickness. A pair of Ti/Au electrodes was deposited with dimensions of 5,000 × 500 µm and a thickness of 100 nm.
The microfluidic chip was placed on a glass wafer using UV and soft lithography processes. Figure 6 illustrates the microfabrication process. To create a microelectrode, the UV patterned electrode deposition was fabricated by spin-coating the AZ P1512 photoresist on the substrate and exposed to UV to develop the patterned electrode. Thin files of Ti/Au layers (50/50 nm) were deposited on the glass substrate by thermal evaporation. Then, left off by acetone was employed to achieve the final electrodes (Fig. 6a). To create a microchannel, the SU-8 photoresist (SU-8 drysheet 50 µm) for the microstructure was laminate-coated and patterned. UV exposure was performed on SU-8 at 60 s to achieve a thickness of 50 µm of SU-8. The entrapping structure was designed to be wider than the space between the two sidewall electrodes to create the detection signal in the chamber. To provide the inlet and outlet flow of fluidic interconnections, a replicated polydimethylsiloxane sylgard 184 (PDMS-184) with multi-wall carbon nanotubes was used as the master mold replication (Fig. 6b). Finally, PDMS with multi-wall carbon nanotubes, which have a microchannel-patterned underneath, were bonded by the plasma O2 method on a pair of Ti/Au electrodes (Fig. 6c).
To set up the electrical base on the microelectrode connection, the microdevice was attached to the print circuit board and connected by using the wire bonding method in the experimentation.