Modification and release of calcitonin gene-related peptide on silk fibroin film

Abstract

As a breakthrough in traditional textiles, silk fibroin (SF) has been widely studied for biomedical material applications. In order to enhance the electronegativity of SF for electrostatic adsorption of positively charged biological factors, a kind of blend film was designed by introducing adipic acid (AA) with two carboxyl groups using ethanol treatment or chemical crosslinking. Following this, a positively charged calcitonin gene-related peptide (CGRP, pI = 9.5) was introduced onto the SF/AA film surfaces through electrostatic interaction. The loading capacity and release kinetics of the CGRP were explored. Results showed that the zeta potential on the SF/AA film surfaces decreased with the increasing AA content. When the mass ratio of SF to AA changed from 100:0 to 100:2.5, the zeta potential of crosslinked blends decreased from –13.6 to –32.6 mV. The maximum loading dose of CGRP on the crosslinked blends (100:2.5) was 500 ng/cm2. In phosphate buffered saline (pH = 7.4), the CGRP on the film surfaces was released rapidly and in high quantity from 12 to 24 h. The release rate was relatively slow under weakly acidic conditions at pH = 5, and it also decreased when the pH value was changed from 7.4 to 9.0. This study provides a new strategy for improving the biological activity of SF used as specific tissue repair materials.