A sandcastle worm-inspired strategy to functionalize wet hydrogels.

Hydrogels have been extensively used in many fields. Current synthesis of functional hydrogels requires incorporation of functional molecules either before or during gelation via the pre-organized reactive site along the polymer chains within hydrogels, which is tedious for polymer synthesis and not flexible for different types of hydrogels. Inspired by sandcastle worm, we develop a simple one-step strategy to functionalize wet hydrogels using molecules bearing an adhesive dibutylamine-DOPA-lysine-DOPA tripeptide. This tripeptide can be easily modified with various functional groups to initiate diverse types of polymerizations and provide functional polymers with a terminal adhesive tripeptide. Such functional molecules enable direct modification of wet hydrogels to acquire biological functions such as antimicrobial, cell adhesion and wound repair. The strategy has a tunable functionalization degree and a stable attachment of functional molecules, which provides a tool for direct and convenient modification of wet hydrogels to provide them with diverse functions and applications.

Bio-inspired poly-DL-serine materials resist the foreign-body response.

Implantation-caused foreign-body response (FBR) is a commonly encountered issue and can result in failure of implants. The high L-serine content in low immunogenic silk sericin, and the high D-serine content as a neurotransmitter together inspire us to prepare poly-DL-serine (PSer) materials in mitigating the FBR. Here we report highly water soluble, biocompatible and easily accessible PSer hydrogels that cause negligible inflammatory response after subcutaneous implantation in mice for 1 week and 2 weeks. No obvious collagen capsulation is found surrounding the PSer hydrogels after 4 weeks, 3 months and 7 months post implantation. Histological analysis on inflammatory cytokines and RNA-seq assay both indicate that PSer hydrogels show low FBR, comparable to the Mock group. The anti-FBR performance of PSer hydrogels at all time points surpass the poly(ethyleneglycol) hydrogels that is widely utilized as bio-inert materials, implying the potent and wide application of PSer materials in implantable biomaterials and biomedical devices.

Silk-Inspired ß-Peptide Materials Resist Fouling and the Foreign-Body Response.

The functions of implants like medical devices are often compromised by the host's foreign-body response (FBR). Herein, we report the development of low-FBR materials inspired by serine-rich sericin from silk. Poly-ß-homoserine (ß-HS) materials consist of the hydrophilic unnatural amino acid ß-homoserine. Self-assembled monolayers (SAMs) of ß-HS resist adsorption by diverse proteins, as well as adhesion by cells, platelets, and diverse microbes. Experiments lasting up to 3 months revealed that, while implantation with control PEG hydrogels induced obvious inflammatory responses, collagen encapsulation, and macrophage accumulation, these responses were minimal with ß-HS hydrogels. Strikingly, the ß-HS hydrogels induce angiogenesis in implant-adjacent tissues. Molecular dynamics simulations indicated that the low FBR performance of ß-HS results from what we term "dual hydrogen bonding hydration", wherein both the backbone amide groups and the sidechain hydroxyl groups of ß-HS undergo hydration.