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. Author manuscript; available in PMC: 2020 May 1.

Published in final edited form as: Biomaterials. 2019 Feb 23;202:26–34. doi: 10.1016/j.biomaterials.2019.02.021

Figure 1. — a Schematic of polyacrylamide hydrogel conjugation. On polyacrylamide hydrogels fabricated by the conventional method, only a few amide groups () react with photoactivated nitrophenyl azide groups () from the sulfo-SANPAH crosslinker, leading to low protein conjugation efficiency. When primary amine groups () are introduced into the polyacrylamide hydrogel surface, photoactivated nitrophenyl azide groups dominantly react with primary amines, thereby enhancing the amount of NHS groups () from the sulfo-SANPAH crosslinker on the surface for conjugation of amine-containing proteins. b Young’s moduli of three polyacrylamide hydrogel groups determined via atomic force microscopy. Data are mean values; standard error of the mean is given as error bars. (n=18, ****p<0.0001, One-way ANOVA by Tukey’s multiple comparisons test) c Photograph of polyacrylamide hydrogels after sulfo-SANPAH incorporation. The orange color of the modified polyacrylamide hydrogel indicates high incorporation of orange sulfo-SANPAH, whereas the conventional hydrogel remains clear. d Fluorescence image of FITC-BSA incorporation into polyacrylamide hydrogels fabricated with the conventional or modified protocol. With the same exposure time, the hydrogel with primary amine groups more efficiently conjugated FITC-BSA than the hydrogel without primary amine groups. Scale bar: 100 μm. e Quantification of fluorescence of FITC-BSA on conventional or modified polyacrylamide hydrogels of three stiffnesses. Modified polyacrylamide hydrogels with primary amine groups show a 10-fold higher fluorescence intensity than hydrogels without primary amine groups. Data are mean values; error bars are standard error of the mean. (n=3)

Inline graphic — a Schematic of polyacrylamide hydrogel conjugation. On polyacrylamide hydrogels fabricated by the conventional method, only a few amide groups () react with photoactivated nitrophenyl azide groups () from the sulfo-SANPAH crosslinker, leading to low protein conjugation efficiency. When primary amine groups () are introduced into the polyacrylamide hydrogel surface, photoactivated nitrophenyl azide groups dominantly react with primary amines, thereby enhancing the amount of NHS groups () from the sulfo-SANPAH crosslinker on the surface for conjugation of amine-containing proteins. b Young’s moduli of three polyacrylamide hydrogel groups determined via atomic force microscopy. Data are mean values; standard error of the mean is given as error bars. (n=18, ****p<0.0001, One-way ANOVA by Tukey’s multiple comparisons test) c Photograph of polyacrylamide hydrogels after sulfo-SANPAH incorporation. The orange color of the modified polyacrylamide hydrogel indicates high incorporation of orange sulfo-SANPAH, whereas the conventional hydrogel remains clear. d Fluorescence image of FITC-BSA incorporation into polyacrylamide hydrogels fabricated with the conventional or modified protocol. With the same exposure time, the hydrogel with primary amine groups more efficiently conjugated FITC-BSA than the hydrogel without primary amine groups. Scale bar: 100 μm. e Quantification of fluorescence of FITC-BSA on conventional or modified polyacrylamide hydrogels of three stiffnesses. Modified polyacrylamide hydrogels with primary amine groups show a 10-fold higher fluorescence intensity than hydrogels without primary amine groups. Data are mean values; error bars are standard error of the mean. (n=3)