Cell sheet engineering: solvent effect on nanometric grafting of poly-n-isopropylacrylamide onto polystyrene substrate under ultraviolet radiation

Figures & data

Table 1 Grafting percentage of polymer on surface according to solvents used

Solvent	Water	Methanol/water 10%	Methanol/water 25%	Methanol/water 50%	Methanol 100%
Grafting (%)	45	55	42	20	7

Table 2 Grafting percentage of polymer on surface according to n-isopropylacrylamide concentration

NIPAAm (%)	0	10	20	40	60
Grafting (%)	0	55	65	120	100

Abbreviation: NIPAAm, n-isopropylacrylamide.

Figure 1 A) Grafting percentage of n-isopropylacrylamide onto polystyrene with two different solvents and B) Effect of n-isopropylacrylamide concentration on grafting in 9:1 (v/v) water/methanol solvent.

Figure 2 Attenuated total reflection Fourier transform infrared spectra of the ungrafted polystyrene (bottom) and spectra of the grafted polystyrene by ultraviolet radiation (top).

Figure 3 Atomic force microscopic image of grafted polystyrene under ultraviolet radiation (scale 1 × 1 μm). A) Preirradiated by gamma radiation (40 KGy), B) Grafted sample in water, C) Grafted sample in 9:1 (v/v) water/methanol solvent, D) Grafted sample in pure methanol solvent.

Figure 4 Atomic force microscopic image of grafted polystyrene with better grafting (120%) with 40% n-isopropylacrylamide concentration resolved in the solvent of 9:1 (v/v) water/methanol under ultraviolet radiation (scale 1 × 1 μm).

Figure 5 Scanning electron microscopy of grafted polystyrene under ultraviolet radiation. A) Grafted sample in water (cross section), B) Grafted sample in the solvent of 9:1 (v/v) water/methanol (cross section), C) Grafted sample in the solvent of 9:1 (v/v) water/methanol with 40% n-isopropylacrylamide (cross section), and D) Surface morphology of grafted sample.

Table 3 Contact angles for normal and preirradiated and grafted samples

	Normal	Grafted samples
Temperature (°C)	θH2O	θH2O
25 Preirradiated (gamma ray)	90	58.6 ± 3.2°
37	90	60.4 ± 0.7°
4	90	43.3 ± 1.3°

Figure 6 Differential scanning calorimetry spectra of the grafted polystyrene with 40% n-isopropylacrylamide concentration resolved in the solvent of 9:1 (v/v) water/methanol under ultraviolet radiation.

Figure 7 Cell viability in grafted sample with 40% n-isopropylacrylamide concentration resolved in a solvent of 9:1 (v/v) water/methanol under ultraviolet radiation at physiological temperature (37°C, Figure 7A) and detached cells on the sample surface after 60 minutes of incubation at 4°C (Figure 7B) with cell viability on control tissue culture polystyrene dishes.

Figure 8 Epithelial cell growth on the grafted Petri dish at 37°C in Figure 5A, and in Figure 8B the cells detached spontaneously when temperature decreases below 4°C on the grafted sample is shown.