Fabrication of natural polysaccharide-based layer-by-layer films

Abstract

Layer-by-layer (LbL) assembly is a facile and versatile method for surface engineering. LbL assembly has been widely applied to various applications, including drug delivery, tissue engineering, single-cell nanoencapsulation (SCNE) by applying nature-derived biopolymers, which have intrinsic biocompatibility and biodegradability. In particular, polysaccharides are the most abundant polymer in nature and also basic structural materials of natural organisms. Due to these advantageous features of polysaccharides, polysaccharide-based LbL films have considerable potential for making the functional interface with biodegradability and nature-mimetic properties. In this thesis, various LbL films have been designed and fabricated with nature-derived polysaccharides, and can be categorized as follows. (1) Ulvan-based neurocompatible LbL films: Ulvan, the sulfated polysaccharide extracted from the cell wall of green seaweed of Ulva species, has a similar structure with extracellular matrix (ECM) molecules, which is expected to have neurocompatibility in general. LbL films with ulvan and chitosan were fabricated, and the neurocompatibility was examined on the films with hippocampal neurons. Ulvan-based LbL films showed stable adhesion of neuronal cells and even accelerated neurite outgrowth, which was comparable with poly-D-lysine-coated control substrates. The ulvan-based surface could also suppress astrocyte adhesion. This LbL film with ulvan and chitosan could be a functional neurocompatible surface for further applications, including neuro-implants.(2) Starch-based cytocompatible and degradable LbL films: Starch has intrinsic cytocompatibility and outstanding biodegradability which induced by -amylase. The starch-based LbL nanofilms were fabricated with synthesized cationic starch (c-ST) and alginate (ALG). All the processes, including film formation and degradation, proved highly cytocompatible, and this cytocompatible characteristic of the system was advantageously applied to SCNE. The c-ST/ALG shells were formed and degraded in a controlled fashion on individual Saccharomyces cerevisiae without any noticeable loss in cell viability. The -amylase-triggered film degradation was also applied to the controlled release of DNA molecules from the multilayer films.The nature-derive polysaccharides-based LbL films were successfully fabricated and demonstrated neurocompatibility and cytocompatible degradability with ulvan and starch, respectively. These polysaccharides showed their intrinsic characteristics on the LbL films and proved their applicability in neuronal culture and SCNE. The systems designed in this thesis could have considerable potential in further biomedical applications and provide possibilities for further studies with nature-derived polysaccharides.