Chitin and chitosan: Properties and applications

http://www.mtdna.or.kr/neowiz/board/up_files/files_17/Chitin_Chitosan_polymers_chemistrySolubilityFiberFormation.pdf

Chitin and chitosan polymers: Chemistry, solubility and fiber formation

Injectable hydrogels with biodegradability have in situ formability which in vitro/in vivo allows an effective and homogeneous encapsulation of drugs/cells, and convenient in vivo surgical operation in a minimally invasive way, causing smaller scar size and less pain for patients. Therefore, they have found a variety of biomedical applications, such as drug delivery, cell encapsulation, and tissue engineering. This critical review systematically summarizes the recent progresses on biodegradable and injectable hydrogels fabricated from natural polymers (chitosan, hyaluronic acid, alginates, gelatin, heparin, chondroitin sulfate, etc.) and biodegradable synthetic polymers (polypeptides, polyesters, polyphosphazenes, etc.). The review includes the novel naturally based hydrogels with high potential for biomedical applications developed in the past five years which integrate the excellent biocompatibility of natural polymers/synthetic polypeptides with structural controllability via chemical modification. The gelation and biodegradation which are two key factors to affect the cell fate or drug delivery are highlighted. A brief outlook on the future of injectable and biodegradable hydrogels is also presented (326 references).

Injectable and biodegradable hydrogels: gelation, biodegradation and biomedical applications

Smart polymeric-based devices and surfaces that reversibly alter their physico-chemical characteristics in response to their environment are the center of many studies related to the development of materials and concepts in a broad-range of biomedical fields. Although the initial interests were more focused in systems for the delivery of therapeutic molecules, other applications have been raised in topics ranging from actuators to biomaterials for tissue engineering and regenerative medicine. The general aspects of the different types of stimuli that can be used to modulate the response are reviewed mainly for the case of hydrogels and surfaces, based on natural-origin or biodegradable macromolecules. Thermosensitive or light responsive surfaces that can modulate cell adhesion or protein adsorption are addressed as well as less conventional smart surfaces, such as substrates onto which biomineralization may be triggered. Injectable liquids that turn to gels by the action of heating (sol-gel thermo-reversible hydrogels) or by changing pH or the ionic milieu (bioinspired self-assembling systems) may find great applicability as temporary scaffolds in non invasive procedures to deliver drugs or cells to particular places in the body. Examples of systems that recognize independently or simultaneously more than one stimulus will also be presented. Besides the typical response to temperature and pH, recent developments on materials that react to biochemical stimuli, including specific enzymes, antibodies or cells, are also highlighted.

Stimuli-Responsive Polymeric Systems for Biomedical Applications

https://pubs.rsc.org/en/Content/ArticlePDF/2016/GC/C5GC02396C

and André Bégin

Papers

Physical Gelation of Chitosan in the Presence of β-Glycerophosphate: The Effect of Temperature