Silk sericin (SS) from the Bombyx mori silk cocoons has received much attention from biomedical scientists due to its outstanding properties, such as antioxidant, antibacterial, UV-resistant, and ability to release moisturizing factors. Unmodified SS does not self-assemble strongly enough to be used as a hydrogel wound dressing. Therefore, there is a need for suitable stabilization techniques to interlink the SS peptide chains or strengthen their structural cohesion. Here, we reported a method to form a silk semi-interpenetrating network (semi-IPN) structure through reacting with the short-chain poly(ethylene glycol) diacrylate (PEGDA) in the presence of a redox pair. Various hydrogels were prepared in aqueous media at the final SS/PEGDA weight percentages of 8/92, 15/85, and 20/80. Results indicated that all semi-IPN samples underwent a sol-gel transition within 70 min. The equilibrium water content (EWC) for all samples was found to be in the range of 70-80%, depending on the PEGDA content. Both the gelation time and the sol fraction decreased with the increased PEGDA content. This was due to the tightened network structure formed within the hydrogel matrices. Among all hydrogel samples, the 15/85 (SS/PEGDA) hydrogel displayed the maximum compressive strength (0.66 MPa) and strain (7.15%), higher than those of pure PEGDA. This implied a well-balanced molecular interaction within the SS/PEGDA/water systems. Based on the direct and indirect MTS assay, the 15/85 hydrogel showed excellent in vitro biocompatibility towards human dermal fibroblasts, representing a promising material for biomedical wound dressing in the future. A formation of a semi-IPN structure has thus proved to be one of the best strategies to extend a practical limit of using SS hydrogels for wound healing treatment or other biomedical hydrogel matrices in the future.

In this study, the preparation of biocompatible cellulose‐based microcapsules encapsulating gallic acid (GA), an important antioxidant of Bambara groundnut extracts, by water‐in‐oil inverse microsuspension polymerization was studied. GA and carboxymethyl cellulose (CMC) were selected as core and shell materials, respectively. For high encapsulation efficiency, CMC was firstly modified (modified‐CMC (m‐CMC)) with 3‐(trimethoxysilyl)propyl methacrylate (MPS) as a silane coupling agent. It was subsequently polymerized with methacrylic acid (MAA) monomer through a radical route, forming a PMAA grafted m‐CMC (m‐CMC‐g‐PMAA) biocompatible polymer shell. Using CMC:MPS in a ratio of 75:25 (w/w %), highly water‐soluble m‐CMC containing a C=C bond for further radical polymerization was obtained. After inverse microsuspension polymerization at various ratios of m‐CMC:MAA, highly stable spherical m‐CMC‐g‐PMAA microcapsules encapsulating GA were formed in all ratios. It was observed that the encapsulation efficiency increased with increase in MAA content. m‐CMC:MAA in a ratio of 33:67 (w/w%) presented the highest encapsulation efficiency which may due to the increase of hydrophilicity of the aqueous phase. It also presented rapid release and non‐cytotoxic characteristics, suited for use in cosmetic products. © 2018 Society of Chemical Industry

Silk fibroin (SF) hydrogels has recently been explored as promising matrices for biomedical applications due to their excellent biodegradability, biocompatibility and hydrophilicity. Despite these, native SF hydrogels showed poor water resistance with typical uncontrollable gelation kinetics. To overcome these drawbacks, a new method of chemical crosslinking using O'O-bis[2-(N-succinimidyl succinylamino) ethyl]polyethylene glycol (NHSP) as a homobifunctional protein crosslinker was employed. A crosslinking reaction, performed under physiological conditions, was completed within 24 hours, producing a hybrid interconnected porous architecture. This network formation contributed to the shortened gelation kinetics and was confirmed by the appearance of a new IR absorption peak of the ether linkage (1102-1104 cm À1 ). A new thermal degradation temperature found at 430 C also reconfirmed the presence of such newly-formed covalent network within the samples. In addition, NHSP could induce a silk phase transformation from the a-helices into the b-sheets, as convinced by the shifts of the amide absorption bands (Amide I, Amide II and Amide III), illustrating their strong intermolecular interactions. The new proposed method has thus, proven its potential use to render the silk-based materials for controlled drug delivery applications.

The Bombyx mori silk fibroin (SF) has recently received much attention as promising hydrogel matrices due to its biocompatibility, hydrophilicity and good permeability. Beside these, porous SF is too brittle in its dry state that does not provide sufficient strength for practical use. To overcome this drawback, semiinterpenetrating networks of SF were synthesized by a redox-initiated reaction using poly(ethylene glycol) diacrylate (PEGa) as a precursor to form a primary network. Various hydrogel properties, including swelling ability, gelation kinetics, morphology and drug release, were evaluated through both physical and spectroscopic techniques. For all hydrogels, the gelation time, sol-gel fraction and equilibrium water content (EWC) were found to decrease with the increasing of PEGa content. Moreover, a sustained delivery of a model compound, Rhodamine B, was also observed. This could be explained in terms of tighter interconnected network and the retardation effects mediated by SF. The proposed method had thus, demonstrated its potential use to improve performance of silk-based materials for drug delivery applications.