Synthesis and Degradation Properties of Sericin/PVA Hydrogels

Abstract

One method of treating diabetic foot ulcers, mainly superficial and deep ulcers, is using a wound dressing in the form of a hydrogel. Sericin derived from silkworm cocoons is a promising hydrogel material candidate because it has anti-inflammatory properties and stimulates collagen production. Sericin was combined with PVA to increase the stability of the resulting hydrogel. Sericin/PVA hydrogel was prepared using the freeze-thawing method with variations in the solution concentration and volume ratio of PVA and sericin. Sericin was successfully extracted using an autoclave method. The FTIR results confirmed that sericin extracted from the cocoon had a dominant secondary structure in the form of a β-sheet. Hydrogel with a concentration of 4% with a 1:1 ratio of PVA and sericin showed good stability and resulted in a hydrogel with characteristics that combine PVA and sericin. The resulting hydrogel had an average pore size range of 24-191 µm and a porosity range of 70-85%, which meets the requirements for wound dressings. Through degradation testing in PBS solution, it was found that the sericin/PVA hydrogel experienced degradation of 60-75% after 672 h of testing.

Keywords: PVA; diabetic foot ulcer; hydrogel; sericin; wound dressing.

Figure 1

(a) FTIR spectra of cocoon and sericin (b) Fourier deconvolution results and Gauss peak fitting from the absorption of the amide group I of the FTIR spectrum of sericin (c) XRD patterns of cocoon and sericin.

Figure 2

(a) Composition and freeze–thawing cycle effect on the physical appearance of the hydrogel (b) freeze-dried hydrogel after four cycles of freeze–thawing. S and P denote sericin and PVA with various volume ratio.

Figure 3

SEM images of the hydrogel surface at a concentration of 2% and 4% with various sericin and PVA ratio compositions.

Figure 4

SEM images of the hydrogel cross-section at a concentration of 2% and 4% with various sericin and PVA ratio compositions.

Figure 5

The porosity of the sericin/PVA hydrogels resulting from SEM image analysis on the sample surface and cross-section. Hydrogels 2% and 4% denote the concentration of sericin and PVA.

Figure 6

Hydrogel degradation rate after 672 h and initial 3 h for samples with a concentration of (a,b) 2% and (c,d) 4%. (e) Visual data of 4% hydrogel sample before and after 336 h degradation test.

Figure 7

Surface (top) and cross-section (bottom) morphology of 4% PVA-sericin hydrogel before PBS solution immersion and after 336 h (14 days) PBS solution immersion.