One of the important routes of drug administration for localized delivery of contraceptives and cervical cancer treatment agents is vaginal canal. Due to the low pH of vagina, a pH-responsive drug delivery system was developed. This hydrogel was synthesized based on a mucoadhesive biopolymer, chitosan (CS), that promotes the interaction between the hydrogel and mucosal surface of the vagina, potentially increasing the residence time of the system. This injectable hydrogel was formed via acid-labile Schiff-base linkages between free amine groups and aldehyde functionalities on modified chitosan. A novel approach was taken to add aldehyde functionalities to chitosan using a two-step reaction. Two types of slow and fast degrading hydrogels were prepared and loaded with iron (II) gluconate dihydrate, a non-hormonal spermicide, and doxorubicin hydrochloride, an anti-cancer drug. The release profiles of these drugs at different pH environments were assessed to determine the pH-dependent release mechanism. Mechanical properties, swell-ability and degradation rate of these matrices were studied. The cross-linking density of the hydrogel as well as pH changes played an important role in the characteristic of these hydrogels. The hydrogels degraded faster in lower pH, while the hydrogel with lower cross-linking density showed longer gelation time and faster degradation rate compared to the gel with higher cross-linking density. In vitro cytotoxicity assessment of these hydrogels in 48 h indicated the non-toxic effect of these hydrogels toward mesenchymal stem cells (MSCs) in the test period.
A comprehensive understanding of the human body endogenous microbiota is essential for acquiring an insight into the involvement of microbiota in tissue healing and regeneration process in order to enable development of biomaterials with a better integration with human body environment. Biomaterials used for biomedical applications are normally germ‐free, and the human body as the host of the biomaterials is not germ‐free. The complexity and role of the body microbiota in tissue healing/regeneration have been underestimated historically. Traditionally, studies aiming at the development of novel biomaterials had focused on the effects of environment within the target tissue, neglecting the signals generated from the microbiota and their impact on tissue regeneration. The significance of the human body microbiota in relation to metabolism, immune system, and consequently tissue regeneration has been recently realised and is a growing research field. This review summarises recent findings on the role of microbiota and mechanisms involved in tissue healing and regeneration, in particular skin, liver, bone, and nervous system regrowth and regeneration highlighting the potential new roles of microbiota for development of a new generation of biomaterials.
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