Fabrication and Characterization of Sericin-PVA Composite Films from Gonometa postica, Gonometa rufobrunnea, and Argema mimosae: Potentially Applicable in Biomaterials

Abstract

This study deals with the fabrication and characterization of sericin-poly(vinyl alcohol) (PVA) composite films from three southern African silkworm cocoons. The sericin-PVA films were achieved by chemically cross-linking poly(vinyl alcohol) (PVA) with pure silk sericin protein using glutaraldehyde (GA) as a cross-linking agent. Fourier transform infrared (FTIR) results confirmed the overall cross-linking of pure silk sericin into PVA-GA networks to form cross-linked sericin-PVA films. This incident was shown by the incorporation of distinct major amide I (ν = 1640-1650 cm-1), amide II (ν = 1538-1540 cm-1), and amide III (ν = 1238-1244 cm-1) peaks. X-ray diffraction (XRD) showed sericin-PVA films to have two features, one representing amorphous and crystalline regions of silk sericin and the other representing sharp high-intensity PVA peaks at around 2θ = 20.2°, demonstrating a high crystallinity in the films as a result of the hydroxyl groups in its side chain. The swelling capacity of the three sericin-PVA films was influenced by the glutaraldehyde content used during the cross-linking process and pH of the aqueous medium into which the films were immersed after a period of time. The water contact angles of the sericin-PVA films were low, at 56.6 ± 0.56 and 60.2 ± 0.86, indicating further their hydrophilic nature. The scanning electron microscopy (SEM) images of the sericin-PVA films showed a rough texture with a granular network pattern on their surface. From the preliminary results, it was observed that the cytotoxicity of three sericin strains (Gonometa rufobrunnea, Argema mimosae, and Gonometa postica) had a cell viability percentage of 103, 90, and 80% respectively, demonstrating their biocompatibility in providing a favorable natural microenvironment for cell culture. The characterization results of the three silk sericin-PVA films demonstrated their potential for application in biomedical and biomaterial fields.