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Collagen fibril hydrogel (CH), with controllable micro-structure, sufficient modifying sites and excellent biocompatibility, has received widely attention in the regulation of biomacromolecules. Herein, dialdehyde carboxymethyl cellulose (DCMC) in different -CHO contents and molecular weights demonstrated two types of cross-linking behaviors to CH, 'limited and long-range' or 'multiple and short range' cross-linking, corresponding to -CHO content ranged from 0 to 53 % and 53 to 90 %, respectively. In regard of structure, non-destroying effect of DCMC on collagen was supported by FT-IR and XRD analysis. CH cross-linked by DCMC (CH-DC) showed declining porosity and aggregating fibrils as -CHO content of DCMC rising. In regard of physicochemical properties, DCMC with >53 % -CHO strengthened the hydrophilicity, thermal stability and degradation resistance of CH-DC. Also, there was 110 % growth on gel strength, 86 Pa enhancements on storage modulus, and 4.6 times decrease on the swelling ratio of CH-DC. Results indicated that DCMC with 79 % -CHO remarkably improved the physicochemical properties of CH via developing sufficient Schiff-base bonds with collagen fibril in a short distance. This study distinguished two patterns of DCMC cross-linking from physicochemical view. In other words, DCMC is potential to meet the requirement of protein-based materials with different expectations by adjusting its -CHO content and molecular weight., Competing Interests: Declaration of competing interest There are no conflicts to declare., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Collagen Type I derived from fish is mainly limited by its poor physicochemical properties for further applications. In this study, we developed epigallocatechin gallate (EGCG) cross-linked collagen hydrogels (EC hydrogels) to realize physicochemical improvements, basing on the interaction mechanism between collagen and EGCG. The integrity of collagen framework with slight secondary structure change in the presence of EGCG was confirmed. The stronger stability of collagen fibrils was proved by slower swelling ratio, declined enzymatic degradation, improved thermal analysis and mechanical test due to EGCG modification. To illustrate the potential mechanism between collagen and EGCG, molecular docking was used to identify both covalent (CN bond, between lysine of collagen and C 2 -ring B of EGCG) and non-covalent bonds (hydrogen bond and hydrophobic interaction) within in EC hydrogel. Taken together, this work would offer some insights into the further study about the interaction between EGCG and collagen., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

In the current era, the treatment of collagen hydrogels with natural phenolics for the improvement in physicochemical properties has been the subject of considerable attention. The present research aimed to fabricate collagen hydrogels cross-linked with gallic acid (GA) and ellagic acid (EA) at different concentrations depending on the collagen dry weight. The structural, enzymatic, thermal, morphological, and physical properties of the native collagen hydrogels were compared with those of the GA/EA cross-linked hydrogels. XRD and FTIR spectroscopic analyses confirmed the structural stability and reliability of the collagen after treatment with either GA or EA. The cross-linking also significantly contributed to the improvement in the storage modulus, of 435 Pa for 100% GA cross-linked hydrogels. The thermal stability was improved, as the highest residual weight of 43.8% was obtained for the hydrogels cross-linked with 50% GA in comparison with all the other hydrogels. The hydrogels immersed in 30%, 50%, and 100% concentrations of GA also showed improved swelling behavior and porosity, and the highest resistance to type 1 collagenase (76.56%), was obtained for 50% GA cross-linked collagen hydrogels. Moreover, GA 100% and EA 100% obtained the highest denaturation temperatures (Td) of 74.96 °C and 75.78 °C, respectively. In addition, SEM analysis was also carried out to check the surface morphology of the pristine collagen hydrogels and the cross-linked collagen hydrogels. The result showed that the hydrogels cross-linked with GA/EA were denser and more compact. However, the improved physicochemical properties were probably due to the formation of hydrogen bonds between the phenolic hydroxyl groups of GA and EA and the nitrogen atoms of the collagen backbone. The presence of inter- and intramolecular cross-links between collagen and GA or EA components and an increased density of intermolecular bonds suggest potential hydrogen bonding or hydrophobic interactions. Overall, the present study paves the way for further investigations in the field by providing valuable insights into the GA/EA interaction with collagen molecules. [ABSTRACT FROM AUTHOR]

Nowadays, collagen hydrogels with both good physicochemical and antibacterial properties for tissue engineering have drawn broad attention. Herein, a biocompatible and antibacterial collagen hydrogel is developed via alginate dialdehyde (ADA) modification and tetracycline hydrochloride (TC) loading based on Schiff's base formation. Fourier transform infrared spectroscopy and X‐ray diffraction spectra suggest the maintenance of collagen structure integrity after ADA modification. The modification significantly contributes to the improved swelling property, resistance against type I collagenase, and strengthens storage modulus of hydrogels with an increase of ADA concentrations. Meanwhile, dynamic release curves of tetracycline hydrochloride (TC)‐loaded hydrogels describe the burst release at the first 15 min then a gradual release, hydrogels act ideally as carriers in antibacterial activity. Furthermore, in vitro biocompatibility and antibacterial properties are successfully confirmed from the fabricated collagen hydrogels. This physicochemical‐ and antibacterial‐property–improved collagen hydrogel would be a potential candidate for wound healing as a scaffold. [ABSTRACT FROM AUTHOR]