Study On Chitosan–based Liquid Crystalline Biomaterials

Chitosan is the deacetylated product of chitin, which is the second most plentiful structural biopolymer after cellulose. Chitosan is a nontoxic, bioactive, biocompatible and biodegradable polymer, which has been widely used as a functional material in tissue engineering recently. It is well known that high molecular weight chitosan and its derivatives often display lyotropic liquid crystalline behavior, due to its rigidity of the chain. There are many hydroxyl and amido groups on the chain, on which can be grafted. Gelatin is biocompatible, which can accelerate the attachment and preliferation of cells. Cholesterol is an important component of life, which is also liquid crystalline matericals. There are many liquid crystals (LC) in life. Biomaterials and LC can be related by cholesterol. We hoped that liquid crystalline biomaterials can be used for tissue engineering.In this paper lyotropic liquid crystals was employed to prepare chitosan, chitosan/gelatin liquid crystal films and scaffolds. The influences of degree of deacetylation (D.D.), molecular weight (M.W.) and addition of gelatin on the critical concentration(C*) for formation of liquid crystalline phase were investigated. The texture, hydrophilicity, rheological properties, temperature of transition of liquid crystalline materials were studied by using polarizing optical microscopy (POM), scanning electron microscopy(SEM), X-ray Diffraction (XRD) and fourier transtorm infrared spectrum(FT-IR), rheometric expansion system, dynamic contact angle, differential scanning calorimetry(DSC). Biocompatibility of Liquid Crystalline materials was also studied. Results showed that the critical concentration(C*) of liquid crystalline-isotropic transition for chitosan solution decreased significantly with the increase of D.D. and M.W., and the addition of gelatin had negative influence on the critical concentration(C*) of liquid crystalline-isotropic transition for chitosan/Gelatin solution. Fingerprint-like texture was tested by POM, IR, XRD. The rheological properties of liquid crystals are different from normal polymers, there were isotropic, biphasic, and anisotropic in phase diagrams, and the viscosity-concentration curve exhibits a maximum at the phase separation concentration. DSC results showed the temperature of liquid crystalline-isotropic transition increased with liquid crystalline higher sequence.