Marine Derived Polysaccharides for Biomedical Applications: Chemical Modification Approaches

Abstract

Polysaccharide-based biomaterials are an emerging class in several biomedical fields such as tissue regeneration, particularly for cartilage, drug delivery devices and gel-entrapment systems for the immobilization of cells. Important properties of the polysaccharides include controllable biological activity, biodegradability, and their ability to form hydrogels. Most of the polysaccharides used derive from natural sources; particularly, alginate and chitin, two polysaccharides which have an extensive history of use in medicine, pharmacy and basic sciences, and can be easily extracted from marine plants (algae kelp) and crab shells, respectively. The recent rediscovery of poly-saccharide-based materials is also attributable to new synthetic routes for their chemical modification, with the aim of promoting new biological activities and/or to modify the final properties of the biomaterials for specific purposes. These synthetic strategies also involve the combination of polysaccharides with other polymers. A review of the more recent research in the field of chemical modification of alginate, chitin and its derivative chitosan is presented. Moreover, we report as case studies the results of our recent work concerning various different approaches and applications of polysaccharide-based biomaterials, such as the realization of novel composites based on calcium sulphate blended with alginate and with a chemically modified chitosan, the synthesis of novel alginate-poly(ethylene glycol) copolymers and the development of a family of materials based on alginate and acrylic polymers of potential interest as drug delivery systems.

Produção de alginato por microrganismos

“…Outros materiais de interesse também podem ser obtidos por modificação química do alginato, pois existe um grande interesse em desenvolver novos materiais poliméricos. Pesquisas recentes na modificação química do alginato reportam a elaboração de materiais compósitos com sulfato de cálcio, com quitosana ou com polímeros acrílicos que apresentam aplicações de interesse especial em sistemas para liberação controlada de medicamentos [24] .…”

Quitosana: biopolímero funcional com potencial industrial biomédico

“…1 O aumento do interesse nas aplicações biomédicas da quitosana tem gerado oportunidades de produção de biomateriais especializados, principalmente com novas modificações químicas e físicas, as quais têm promovido novas atividades biológicas para fins específicos. Estas estratégias também têm envolvido a combinação da quitosana com outros polímeros e materiais inorgânicos na produção de materiais compósitos.…”

“…Estes biomateriais apresentam características mecânicas, físico-químicas e propriedades funcionais especiais. 1,2 A quitosana é obtida pela reação de desacetilação da quitina em meio alcalino. A quitina é um polímero natural extraído de exoesqueleto de crustáceos, insetos etc., composto pelas unidades monoméricas de β-(1→4)-2-amino-2-desoxi-D-glicose e β-(1→4)-2-acetamida-2-desoxi-D-glicose.…”

Chitosan Mucoadhesive Buccal Films: Effect of Different Casting Solvents on Their Physicochemical Properties

“…The swelling index of medicated mucoadhesive films was determined using two aqueous vehicles; namely, distilled water and simulated saliva solution (2.38g NaR 2RHPOR4R, 0.19g KHR 2RPOR4R and 8g NaCl/liter of distilled water adjusted with phosphoric acid to pH 6.8±0.05) [16]. Films (1x1 cm) were weighed alone and placed on a pre-weighed wire mesh (49 openings/cm 2 The Swelling Index was calculated using the formula [17][18][19].…”

“…Chitin, an abundant natural polysaccharide, is a straight polymer consisting of β-(1-4)-Nacetyl-D-glucosamine units with a three-dimensional α-helical arrangement. Partial deacetylation of chitin leads to the production of chitosan, which is (poly-(N-acetyl-glucosamine) [1,2].…”