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Mussel adhesive proteins (MAPs) have a unique ability to firmly adhere to different surfaces in aqueous environments via the special amino acid, 3,4-dihydroxyphenylalanine (DOPA). The catechol groups in DOPA are a key group for adhesive proteins, which is highly informative for the biomedical domain. By simulating MAPs, medical products can be developed for tissue adhesion, drug delivery, and wound healing. Hydrogel is a common formulation that is highly adaptable to numerous medical applications. Based on a discussion of the adhesion mechanism of MAPs, this paper reviews the formation and adhesion mechanism of catechol-functionalized hydrogels, types of hydrogels and main factors affecting adhesion, and medical applications of hydrogels, and future the development of catechol-functionalized hydrogels.

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Classic hypotheses of Alzheimer’s disease (AD) include cholinergic neuron death, acetylcholine (ACh) deficiency, metal ion dynamic equilibrium disorder, and deposition of amyloid and tau. Increased evidence suggests neuroinflammation and oxidative stress may cause AD. However, none of these factors induces AD independently, but they are all associated with the formation of Aβ and tau proteins. Current clinical treatments based on ACh deficiency can only temporarily relieve symptoms, accompanied with many side-effects. Hence, searching for natural neuroprotective agents, which can significantly improve the major symptoms and reverse disease progress, have received great attention. Currently, several bioactive marine products have shown neuroprotective activities, immunomodulatory and anti-inflammatory effects with low toxicity and mild side effects in laboratory studies. Recently, chitosan (CTS), chitooligosaccharide (COS) and their derivatives from exoskeletons of crustaceans and cell walls of fungi have shown neuroprotective and antioxidative effects, matrix metalloproteinase inhibition, anti-HIV and anti-inflammatory properties. With regards to the hypotheses of AD, the neuroprotective effect of CTS, COS, and their derivatives on AD-like changes in several models have been reported. CTS and COS exert beneficial effects on cognitive impairments via inhibiting oxidative stress and neuroinflammation. They are also a new type of non-toxic β-secretase and AChE inhibitor. As neuroprotective agents, they could reduce the cell membrane damage caused by copper ions and decrease the content of reactive oxygen species. This review will focus on their anti-neuroinflammation, antioxidants and their inhibition of β-amyloid, acetylcholinesterase and copper ions adsorption. Finally, the limitations and future work will be discussed.

Our earlier research indicated that chitosan-gentamicin conjugate (CS-GT) possesses superior antimicrobial activity and good water solubility. To develop CS-GT-based scald dressings, the antibacterial properties of CS-GT were further studied, and the biosafety of CS-GT and the healing mechanism of CS-GT hydrogel was systematically explored in this article. It was found that cell viability shows a declined inclination with the prolonged culture time and the increased concentration of CS-GT. After three day’s culture, the cell viability could still remain at 79.72% when CS-GT concentration was as high as 1000 μg/mL. On the other hand, the hemolysis rate of CS-GT was lower than 5% when its concentration is 800 μg/mL. Therefore CS-GT has good cytocompatibility and hemocompatibility. A wound-healing experiment has shown that the skin healing rate of CS-GT hydrogel was the highest at 99.61%, followed by the positive control (wet burn ointment) 94.98%, GT hydrogel 87.50%, and matrix 77.39%. The blank control group, however, possessed the lowest healing rate of 75.45%. Further analysis indicated that CS-GT hydrogel could promote the synthesis of total protein (TP) in skin granulation tissue, resulting in the enhanced hydroxyproline (HYP) content, which facilitated collagen fibrogenesis, reduced cytokine expression in an inflammatory response, and, ultimately, accelerated wound healing. To sum up, CS-GT hydrogel is a promising scald dressing.