Protein Removal from Hydrogels through Repetitive Surface Degradation

Abstract

Suppression of protein adsorption is a necessary property for materials used in the living body. In this study, thermoresponsive and degradable hydrogels were prepared by the radical polymerization of 2-methylene-1,3-dioxepane, 2-hydroxyethyl acrylate (HEA), and poly(ethylene glycol) monomethacrylate (PEGMA). The prepared hydrogels re-exposed PEG-grafted chains to the interface through surface degradation, which was confirmed by the maintenance of the chemical composition of the hydrogel surfaces after hydrolysis. Notably, adsorbed proteins can be removed from the hydrogel surfaces through hydrogel surface degradation at least thrice.

Keywords: 2-methylene-1,3-dioxepane; degradation; hydrogel surface; hydrogels; protein removable surface; thermoresponsive.

Figure 1

Illustration of protein removal by degradation of the hydrogel.

Scheme 1. Synthesis of Thermoresponsive Degradable Hydrogels via Radical Polymerization

Figure 2

Characterization of hydrogels during alkaline hydrolysis. Hydrogels prepared with the composition of (MDO + HEA)/PEGMA = 100:1 (mol/mol) and MDO/HEA = 6:4 (mol/mol). (a) Hydrolysis time-dependent changes in swelling ratios of the hydrogels at 37 and 10 °C. Data are expressed as the mean ± SD (n = 3). Red plot: 37 °C and blue plot: 10 °C. (b) Optical images of the hydrogel during hydrolysis at 10 and 37 °C.

Figure 3

Characterization of the hydrogel surface and degradation supernatant during alkaline hydrolysis. Hydrogels were prepared with the composition of (MDO + HEA)/PEGMA = 100:1 (mol/mol) and MDO/HEA = 6:4 (mol/mol). (a) ¹H NMR spectra of supernatants during hydrolysis of hydrogels for 1 and 3 h. (b) ATR-FTIR spectra of dried hydrogels before and after hydrolysis for 3 h.

Figure 4

Fluorescence microscopic images of hydrogels (a) immersed in FITC–BSA solution (1.0 mg/mL in PBS, pH 7.4) for 1 h (upper) and hydrolyzed in 1.0 mmol/L NaOH solution for 1 h (bottom) and (b) immersed in FITC–BSA solution (1.0 mg/mL in PBS, pH 7.4) for 1 h (upper) and PBS for 1 h (bottom). (c) Signal intensity ratio of adsorbed BSA on hydrogels. Yellow and red bars: the signal intensity ratio for the hydrogels immersed in FITC–BSA solution for 1 h. Blue bars: the signal intensity ratio for the hydrogels immersed in 1.0 mmol/L NaOH solution for 1 h after 1 h incubation in FITC–BSA solution. Black bars: The signal intensity ratio for the hydrogels immersed in PBS for 1 h after 1 h incubation in FITC–BSA solution. (d) Signal intensity ratio of adsorbed fibrinogen on hydrogels. Yellow and red bars: the signal intensity ratio for the hydrogels immersed in fibrinogen solution for 1 h. Blue bars: the signal intensity ratio for the hydrogels immersed in 1.0 mmol/L NaOH solution for 1 h after 1 h incubation in fibrinogen solution. Black bars: the signal intensity ratio for the hydrogels immersed in PBS for 1 h after 1 h incubation in fibrinogen solution.