Enzymatic Digestion of Keratin for Preparing a pH-Sensitive Biopolymer Hydrogel

Abstract

Keratin, a typical natural biopolymer, has been applied in the biomedical field due to its biocompatible, eco-friendly, and inexpensive characteristics. In this paper, pig hair keratin (PHK) was pre-treated and efficiently digested by enzyme to afford enzymatically digested pig hair keratin (E-PHK) with short polymer chains. Then, by using methacrylic acid (MAA), as a functional monomer, a novel keratin (E- PHK)-based biopolymer hydrogel (E-PHKPGel) was prepared via grafting copolymerization. It was characterized by Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, and scanning electron microscopy. The swelling behaviours, salt sensitivity, and release behaviours of E-PHKPGel were also investigated. As a result, the enzymatic digestion method was found to improve the swelling and release properties of PHK. The release behaviours of pH-sensitive E-PHKPGel were controllable by adjustment of the pH value. For the small molecular model drug (rhodamine B), the cumulative release rate was 89 % in 12 h at pH 7.2. For the macromolecular model drug (bovine serum albumin), the cumulative release rate reached 70.7 % in 12 h at pH 7.2. In conclusion, a simple and efficient enzymatic digestion method to PHK has been found. E-PHKPGel is expected to be used in the biomedical field as a sustained drug carrier as well as a humid medicinal material in the clinical nursing field.