## 3 Results
### Biocompatibility Studies of the Ionogels  
Cytocompatibility of the silica ionogel samples was studied using an MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay. Immortalized human epidermal keratinocytes HaCaT and Swiss fibroblast S3T6 cells were used for the assay. Twelve thousand cells per well were seeded in 48-well tissue culture plates and incubated for 24 h in a CO2 incubator at 37 \({}^{\circ}\)C for the proliferation of cells. The seeded plates were treated with different concentrations (1, 5, 10, 25, 50, 75, and 100 \(\upmu\)g/mL) of all the gel samples (IL 0, IL 0.1, IL 0.1, IL 3.0, IL 5.0, and IL 10.0). Then, after 24 h of incubation, MTT solution (0.5 mg/mL) was added and incubated for another 4 h at 37 \({}^{\circ}\)C. The formazan complex was solubilized with dimethyl sulfoxide, and adsorption was measured using a microplate reader at 570 nm.  
The cytocompatibility of the ionogels with different concentrations of ionic liquids for Swiss fibroblast and HaCaT cells is presented in Figure 6. The % cell viability of IL 0 was found to be 76.75% and 99% for the lowest concentration of 1 \(\upmu\)g/mL in Swiss fibroblast and HaCaT cells, respectively. In the case of the highest concentration of 100 \(\upmu\)g/mL, the % cell viability was 17.43% and 20.3% in Swiss fibroblast and HaCaT cells, respectively. In the case of IL 0.1, 89.9% and 98% cell viability was observed for the lowest concentration of 1 \(\upmu\)g/mL in Swiss fibroblast and HaCaT cells, respectively. In the case of a higher concentration (100 \(\upmu\)g/mL), the % cell viability was estimated as 19.45% and 23.1% in Swiss fibroblast and HaCaT cells, respectively. The half-maximal inhibitory concentration (IC\({}_{50}\)) value was observed above 10 \(\upmu\)g/mL for both cells. The gel sample IL 1.0 showed 85.6% and 95% cell viability for the minimum concentration of 1 \(\upmu\)g/mL in Swiss fibroblast and HaCaT cells, respectively. The cell viability was reduced to 32.4% and 13.9% in Swiss fibroblast and HaCaT cells, respectively, for the higher concentration of the 100 \(\upmu\)g/mL sample. The IL 3.0 sample exhibited 80.8% and 97% viability for both cells at the minimum concentration of 1 \(\upmu\)g/mL, whereas the higher dose (100 \(\upmu\)g/mL) showed 22.9% and 27% viability for both types of cells. The MTT assay indicates that 99.5% and 97% viability of cells was observed for IL 5.0 in both cells with a dose of 1 \(\upmu\)g/mL. The higher dose of 100 \(\upmu\)g/mL relatively  
Figure 4: SEM images of silica ionogels: (**a**) IL 0 (\(\times\)50 K), (**b**) IL 1.0 (\(\times\)100 K), (**c**) IL 5.0 (\(\times\)30 K), and (**d**) IL 10.0 (\(\times\)50 K).  
showed 20% and 16% in the tested cells. The IL 10 sample clearly exhibited 88.46% and 89% cell viability for the 1 \(\mathrm{\SIUnitSymbolMicro}\)/mL dose concentration in Swiss fibroblast and HaCaT cells, respectively. The cell viability was observed as 20% and 21.5% in the 100 \(\mathrm{\SIUnitSymbolMicro}\)/mL dose of the sample in both the cells. Overall, more than 50% cell viability (Swiss fibroblast and HaCaT cells) was observed for all the gel samples till the 10 \(\mathrm{\SIUnitSymbolMicro}\)/mL concentration. The micrographs of the Swiss and HaCaT cell lines treated with various gel samples with a concentration 1 \(\mathrm{\SIUnitSymbolMicro}\)/mL are provided in Figures 7 and 8. It can be observed from Figure 6 that gel samples provided very good viability and proliferation to HaCaT cell lines for the different concentrations of ionic-liquid-loaded ionogel samples (\(>\)90%). The addition of ionic liquid greatly influenced the Swiss cell viability of the IL 5.0 sample (99.5%) compared with the gel without ionic liquid (IL 0 (76%)). After 5% IL content, the Swiss cell viability decreased to 88%. The MTT assay clearly indicates that the prepared gel samples exhibit very good biocompatibility, which helps us to encapsulate biomolecules and retain their stability over a period.