The interaction of silica nanoparticles with catalase and human mesenchymal stem cells: biophysical, theoretical and cellular studies

Figures & data

Figure 1 Fluorescence quenching of CAT in the presence of different concentrations of SiO₂ NPs: 0 (red), 1 (blue), 5 (purple), 10 (grey), 15 (yellow) and 20 μM (green) at 298 (A), 310 (B) and 315 K (C).

Table 1 The K_SV and kq values for the SiO₂ NPs/CAT complex at three different temperatures

T	KSV (M^−1)	kq (M^−1 s^−1)	R^2
298	(4.1±0.76)×10^4	(4.1±0.76)×10^12	0.92
310	(4.3±0.64)×10^4	(4.3±0.64)×10^12	0.91
315	(5.0±0.61)×10^4	(5.0±0.61)×10^12	0.95

Figure 2 Stern–Volmer plots of CAT in the presence of different concentrations of SiO₂ NPs at 298 (blue), 310 (orange) and 315 K (grey).

Figure 3 Modified Hill plot of CAT in the presence of different concentrations of SiO₂ NPs at 298 (blue), 310 (orange) and 315 K (grey).

Table 2 The n and logK_b values for the SiO₂ NPs/CAT complex at different temperatures

T	n	logKb (M^−1)	R^2
298	0.51±0.07	2.28±0.32	0.95
310	0.55±0.08	2.54±0.27	0.95
315	0.63±0.08	2.92±0.41	0.92

Figure 4 van’t Hoff plot of CAT in the presence of SiO₂ NPs at 298, 310 and 315 K.

Table 3 The thermodynamic parameters of SiO₂ NPs/CAT complex at three different temperatures

T	∆H (kJ/mol)	T∆S (kJ/mol)	∆G (kJ/mol)
298	69.67±8.34	81.62±9.11	−11.95±1.81
310	69.67±8.34	84.90±10.28	−15.23±2.29
315	69.67±8.34	86.27±13.35	−16.60±2.41

Figure 5 CD spectra of CAT in the presence of different concentrations of SiO₂ NPs: 0 (black), 5 (red), 10 (blue) and 20 μM (green), at room temperature.

Table 4 The kinetic parameters of CAT in the presence of varying concentrations of SiO₂ NPs

[SiO2 NP] (µM)	Km (mM)	Vmax (mM/min)	Kcat (min^−1)	Efficiency (min^−1mM^−1)
0	3.9±0.21	2.8±0.11×10^−1	2.8×10^8	7.1×10^7
10	3.9±0.19	2.8±0.25×10^−1	2.8×10^8	7.1×10^7
20	3.9±0.33	2.7±0.17×10^−1	2.7×10^8	6.9×10^7
50	4.0±0.39	2.6±0.28×10^−1	2.6×10^8	6.5×10^7

Figure 6 The docked (SiO₂)_72/CAT (A) and Si₂₀/CAT (B) systems.

Figure 7 The interacting residues of CAT with (SiO₂)₇₂ cluster from two different view angles.

Figure 8 The interacting residues of CAT with Si₂₀ cluster from two different view angles.

Figure 9 SiO₂ cluster/CAT complex in the beginning and after 200 ps simulation.

Figure 10 SiO₂ NPs (up to 200 μg/mL) decrease the viability of hMSCs. The cells were incubated with varying concentrations of SiO₂ NPs for 24 hrs before MTT assay was carried out. *P<0.05 compared to the control group.

Figure 11 Cellular internalization of SiO₂ NPs into the hMSCs. (A) Control cells and (B) treated cells with SiO₂ NPs (200 μg/mL).

Figure 12 Morphological changes of hMSCs induced by different concentrations of SiO₂ [0 (A), 10 (B), 50 (C), 100 (D) and 200 µg/mL (E)].

Figure 13 SiO₂ NPs cause no increase in the level of LDH in cell culture medium. hMSCs cells were incubated with varying concentrations of SiO₂ NPs for 24 hrs before examining the LDH activity of cell culture medium.

Figure 14 SiO₂ NPs at concentrations of 100 and 200 μg/mL increase the level of ROS in hMSCs. hMSCs cells were incubated with SiO₂ NPs for 24 hrs before the ROS level was examined. *P<0.05 compared to control group.

Figure 15 SiO₂ NPs at concentration of 200 μg/mL activate caspase-3 in hMSCs. hMSCs cells were incubated with varying concentrations of SiO₂ NPs for 24 hrs before the caspase-3 activity was assessed. *P<0.05 compared to control group.

Figure 16 hMSCs cells were incubated with 200 μg/mL of SiO₂ NPs for 24 hrs, then co-stained with Annexin V-FITC/PI to quantify the apoptosis induction. (A) Control cells and (B) SiO₂ NPs-treated cells.