SBA-15

To detect antibody binding to SARS‐CoV‐2‐S protein, HEK‐293T cells were cotransfected with SARS‐CoV‐2‐S DNA and a GFP reporter plasmid (e.g., pEGFP‐C1) using the PEI method as described previously [63 (link)]. A total of 10⁵ thawed or freshly transfected cells were incubated first in 96‐well plate with 100 μL undiluted hybridoma supernatant or 100 μL mouse serum (1:200 dilutions in R10+ medium), bound antibodies were detected with a Cy5‐conjugated goat anti‐pan‐mouse IgG antibody (Southern Biotechnology, Birmingham, USA, #SBA‐1030‐15). Cells were washed in FACS buffer and analyzed with an Attune Nxt, CytoFlex, or a Gallios flow cytometer (Thermo Fisher Scientific or Beckman Coulter, Brea, USA, respectively) and evaluated with Flow Logic^TM (IInivai Technologies Mentone, Australia). Flow cytometric analysis adhered to “Guidelines for the use of flow cytometry and cell sorting in immunological studies” [64 (link)].
Hybridoma cells were stained intracellularly for the assessment of the monoclonality of the colonies and the determination of the IgG subtype. Briefly, 10⁵ cells were fixed for 20 min in 2% paraformaldehyde (Morphisto, Frankfurt am Main, Germany) diluted in PBS, washed twice with FACS buffer, resuspended in permeabilization buffer (0.5% Saponin Sigma Aldrich, in FACS buffer) containing fluorochrome‐conjugated murine H and L isotype‐specific antibodies (anti‐mouse IgG1‐APC # 550874 and anti‐mouse IgG3‐bio # 020620 from BD, Franklin Lakes, USA, anti‐mouse IgG2b‐PE SBA‐1090‐09 and anti‐mouse IgG2c‐bio SBA‐1079‐08 from Southern Biotech, anti‐mouse Ig light chain lambda APC # 407306 and anti‐mouse IgG light chain kappa PE both from Biolegend, San Diego, USA) and incubated for 1 h at 4°C. Cells were again washed in FACS buffer and analyzed with an Attune Nxt, CytoFlex, or a Gallios flow and evaluated with Flow Logic^TM.

The Brunauer–Emmett–Teller (BET) surface area, pore
volume, and average pore size of SBA-15 before and after modification
with Ni were determined by a NOVAtouch LX^{4 (link)} surface area and pore size analyzer (Quantachrome Instruments, USA)
at 77 K. Prior to analysis, the material was degassed at 150 °C
for 3 h. The data from the desorption branch of the nitrogen isotherm
were then analyzed by the Barrett–Joyner–Halenda (BJH)
method to obtain the pore volume and pore diameter of the materials.^{52 (link)}

Images of SBA-15 and Ni/SBA-15 were
captured using a Phenom X5 Pro Desktop scanning electron microscope
(Thermo Fisher Scientific, USA). Elemental mapping was conducted simultaneously
using EDS using Phenom-World software. The samples were coated with
gold prior to analysis.

A mesoporous
silica support, SBA-15, was synthesized using an ultrasonic-assisted
sol–gel method modified from Zhao et al.^{27 (link)} A total of 16 g of Pluronic P-123 was placed in an Erlenmeyer
flask and dissolved in 600 mL of 2 M HCl solution. The mixture was
then sonicated using Krisbow Ultrasonic Cleaner 1400 mL with an ultrasonic
frequency of 42 kHz until its
temperature reached 37–40 °C. Next, 34 mL of TEOS was
added dropwise to the mixture, and sonication was continued for 3
h. After that, the mixture was transferred to a reagent bottle and
heated in an oven at 100 °C for 24 h. Next, the mixture was cooled
to room temperature and filtered to obtain a white solid. Then, the
solid was washed with distilled water until the pH of the filtrate
was equal to the pH of the distilled water. The solid was then dried
in an oven at 100 °C. After that, the solid was calcined at 500
°C for 8 h. The white solid obtained was SBA-15.
SBA-15
was then doped with 10% nickel (Ni) using the wet impregnation method.
A total of 2.49 g of nickel nitrate hexahydrate was dissolved in 30
mL of distilled water. Then, 4 g of SBA-15 was added to the mixture,
and the mixture was sonicated using Krisbow Ultrasonic Cleaner 1400
mL with an ultrasonic frequency of 42 kHz for 3 h. To evaporate the
water, the mixture was heated in an oven at 110 °C. The solid
was then calcined at 500 °C for 5 h. The resulting solid was
denoted Ni/SBA-15.