Structural Studies on Methylated Starch Granules

Hydrogel-Forming Algae Polysaccharides: From Seaweed to Biomedical Applications

With the increasing growth of the algae industry and the development of algae biorefinery, there is a growing need for high-value applications of algae-extracted biopolymers. The utilization of such biopolymers in the biomedical field can be considered as one of the most attractive applications but is challenging to implement. Historically, polysaccharides extracted from seaweed have been used for a long time in biomedical research, for example, agarose gels for electrophoresis and bacterial culture. To overcome the current challenges in polysaccharides and help further the development of high-added-value applications, an overview of the entire polysaccharide journey from seaweed to biomedical applications is needed. This encompasses algae culture, extraction, chemistry, characterization, processing, and an understanding of the interactions of soft matter with living organisms. In this review, we present algae polysaccharides that intrinsically form hydrogels: alginate, carrageenan, ulvan, starch, agarose, porphyran, and (nano)cellulose and classify these by their gelation mechanisms. The focus of this review further lays on the culture and extraction strategies to obtain pure polysaccharides, their structure-properties relationships, the current advances in chemical backbone modifications, and how these modifications can be used to tune the polysaccharide properties. The available techniques to characterize each organization scale of a polysaccharide hydrogel are presented, and the impact on their interactions with biological systems is discussed. Finally, a perspective of the anticipated development of the whole field and how the further utilization of hydrogel-forming polysaccharides extracted from algae can revolutionize the current algae industry are suggested.

Cytocompatibility of a matrix of methylated cassava starch and chitosan

Starches can be used to form edible or biodegradable films, and recently modified starches have been used to form self-supporting films by casting from aqueous solution. In this work, we aimed to propose a novel starch-based composite biomaterial matrix for use in biomedical applications, especially tissue engineering. The goal of the study was to evaluate the cytocompatibility of composite hydrogels of methylated starch and chitosan, using glutaraldehyde as the cross-linker. Commercial cassava starch with high purity (96.69%) was methylated with dimethyl sulfate in order to obtain a rigid material that could possibly render stronger mechanical properties to chitosan hydrogels. Therefore, methylated starch was mixed with a solution of chitosan and the cross-linking was induced by the addition of glutaraldehyde, allowing the formation of hydrogel films which were visualized under scanning electron microscopy. The method of fabrication was optimized based on the capacity of the cells to attach to the material and proliferate. After thorough washes with ethanol and saline solution, human fibroblasts were seeded on top of the gels and allowed to grow for 3 to 5 days. Cell viability was measured using an (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) MMT assay, and cell morphology was visualized by light microscopy. It was found that cells were viable at every time point, with their metabolic activity comparable to the controls (tissue culture plastic and chitosan alone), as well as clear cell–matrix interactions. Moreover, an increase in the metabolic activity over time indicated the capacity of the material to support cell proliferation. The proposed methylated starch–chitosan system is an excellent matrix that allows cell adhesion and could thereby be further assessed as a scaffold for tissue engineering.