Water depth affects submersed macrophyte more than herbivorous snail in mesotrophic lakes.

Introduction: Water depth (WD) and snail abundance (SA) are two key factors affecting the growth of submersed aquatic plants in freshwater lake ecosystems. Changes in WD and SA drive changes in nutrients and other primary producers that may have direct or indirect effects on submersed plant growth, but which factor dominates the impact of both on aquatic plants has not been fully studied. Methods: To investigate the dominant factors that influence aquatic plant growth in plateau lakes, a one-year field study was conducted to study the growth of three dominant submersed macrophyte (i.e., Vallisneria natans, Potamogeton maackianus, and Potamogeton lucens) in Erhai Lake. Results: The results show that, the biomass of the three dominant plants, P.maackianus, is the highest, followed by P.lucens, and V.natans is the lowest. Meanwhile, periphyton and snails attached to P.maackianus are also the highest. Furthermore, WD had a positive effect on the biomass of two submersed macrophyte species of canopy-type P.maackianus and P.lucens, while it had a negative effect on rosette-type V.natans. Snail directly inhibited periphyton attached on V.natans and thereby increasing the biomass of aquatic plants, but the effect of snails on the biomass of the other two aquatic plants is not through inhibition of periphyton attached to their plants. Discussion: The dominant factors affecting the biomass of submersed macrophyte in Erhai Lake were determined, as well as the direct and indirect mechanisms of WD and snails on the biomass of dominant submersed macrophyte. Understanding the mechanisms that dominate aquatic plant change will have implications for lake management and restoration.

Injectable keratin hydrogels as hemostatic and wound dressing materials.

Injectable hydrogels hold promise in biomedical applications due to their noninvasive administration procedure and capacity enabling the filling of irregularly shaped defects. Protein-based hydrogels provide features including good biocompatibility and inherent biofunction. However, challenges still remain to develop a protein-based injectable hydrogel in a convenient way due to the limited active groups in proteins. Keratins are a group of cysteine-rich structural proteins found abundantly in skin and skin appendages. In this work, we utilized keratin and the Au(iii) salt to develop an injectable hydrogel based on the dynamic exchange between disulfide bonds (S-S) and gold(i)-thiolates (Au-S). Such a hydrogel could be prepared at the physiological pH and applied as an injectable hydrogel for biomedical applications including hemostatic and wound dressing materials. Our findings demonstrated that this keratin injectable hydrogel showed a good hemostatic effect in both tail amputation and liver injury models. Moreover, it was proved efficient as a drug loading carrier, and the deferoxamine-loaded hydrogel showed a desirable wound healing effect in a full-thickness excision wound model.

Regenerated keratin-encapsulated gold nanorods for chemo-photothermal synergistic therapy.

Gold nanorods (AuNRs) have been widely applied to photothermal therapy against cancer. However, the chemically synthesized AuNRs such as that via seed-mediate method usually demonstrated a high cytotoxicity due to the existence of cetyltrimethylammonium bromide (CTAB) coating. In this work, keratin, a family of cysteine-rich structural fibrous proteins was used for the first time to encapsulate AuNRs by a simple mixing method. Compared with CTAB-AuNRs, the keratin-encapsulated AuNRs (AuNRs@Kr) showed an improved colloid stability and good biocompatibility including low cytotoxicity and hemolytic effect. Moreover, AuNRs@Kr exhibited great potential as drug carriers with redox-responsive drug release behavior, due to the high concentration of disulfide crosslinking in keratin coating, and the DOX-loaded AuNRs@Kr demonstrated higher chemo-photothermal synergistic therapy efficiency against 4T1 cells compared with either free DOX or AuNRs@Kr alone, suggesting a promising nanoplatform for cancer therapy.

Tunable keratin hydrogel based on disulfide shuffling strategy for drug delivery and tissue engineering.

Protein-based hydrogels that possess tunable properties have long been a challenge in tissue engineering. Keratin is a group of natural proteins derived from skin and skin appendant, and features a rich content of cysteine residue which exists in the form of disulfide bonds. Inspired by this, in this work, a simple disulfide shuffling strategy was utilized to develop keratin hydrogels by converting the intramolecular disulfide bonds into the intermolecular disulfide bonds. To achieve this, the intramolecular disulfide bonds were first cleaved by the reductive reagent such as cysteine, to liberate free thiol group, which formed intermolecular disulfide bonds through thiol oxidation. It was demonstrated that control of the cysteine level led to a tunable disulfide crosslinking density, and thus an altered network structure, gel degradation, and drug release rate. Also, this strategy enables good biocompatibility of the material owing to avoiding extra chemical crosslinkers in the preparation procedure. Moreover, this keratin hydrogel had redox-responsive capacity in both gel degradation and drug release due to the disulfide-bond based network structure, providing extensive applicability in tissue engineering and drug release.

Comparative study of kerateine and keratose based composite nanofibers for biomedical applications.

In this work, two forms of keratins, kerateine (KR) and keratose (KO), were fabricated respectively into electrospun nanofibers by combination with polyurethane (PU). The differences of the structure and material properties between KR and KO based fibers were investigated by SEM observation, ATR-FTIR, XRD, contact angle, tensile test, in vitro degradation and cytocompatibility assay. The results indicated that the KR based nanofibers exhibited a higher tensile modulus, lower fracture strain and slower degradation rate, mainly due to the reformation of disulfide crosslinking between the regenerated cysteines in KR after the reductive extraction. The KO based nanofibers demonstrated a stronger hydrophilic property and higher water uptake ability due to the cysteic acid residues resulting from the oxidative extraction. Furthermore, the combination of keratins, regardless of KR or KO, could obviously improve the cytocompatibility of PU, especially in the cell attachment stage.