Structural characterization and properties of polyols plasticized chitosan films.

In this study, the influence of different polyols such as glycerol, xylitol and maltitol on the crystalline structure and thermal properties of chitosan films were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The concentration of polyol was fixed at 20 wt%. FTIR result showed that the addition of polyols weakened the hydrogen bonding between chitosan molecules, whereas the electrostatic interactions remained nearly unchanged. Structural analysis revealed that the plasticizer which promoted the crystallization of chitosan was moisture rather than polyol contained in the polymer films. DSC result indicated that glycerol plasticized film had a lower glass transition temperature (Tg) and lower melting temperature (Tm). The low thermal transition temperatures suggested that the moisture content is higher in glycerol plasticized film, which was evidenced by TGA result. In addition, the polyols incorporation resulted in a decrease of the tensile strength of chitosan films, while their ductility was improved. These observations indicate that the addition of polyols as plasticizers could regulate the microstructure as well as the properties of chitosan films, which is essential for their usage in food industry.

Molecular interactions in gelatin/chitosan composite films.

Gelatin and chitosan were mixed at different mass ratios in solution forms, and the rheological properties of these film-forming solutions, upon cooling, were studied. The results indicate that the significant interactions between gelatin and chitosan promote the formation of multiple complexes, reflected by an increase in the storage modulus of gelatin solution. Furthermore, these molecular interactions hinder the formation of gelatin networks, consequently decreasing the storage modulus of polymer gels. Both hydrogen bonds and electrostatic interactions are formed between gelatin and chitosan, as evidenced by the shift of the amide-II bands of polymers. X-ray patterns of composite films indicate that the contents of triple helices decrease with increasing chitosan content. Only one glass transition temperature (Tg) was observed in composite films with different composition ratios, and it decreases gradually with an increase in chitosan proportion, indicating that gelatin and chitosan have good miscibility and form a wide range of blends.

[Development of a new noninvasive blood sugar detector].

The level of blood sugar is an improtant indicator used in the diagnosis and management of diabetes mellitus. In this respect, polarimeter and blood sugar detector were conventionally and generally used in hospitals; However, the former one is already obsolete; the latter one is invasive. In this paper, the development of a novel noninvasive blood-sugar detector is described. The experiment indicate that this detector is nonivasive, safe, fast, and easy to operate, and it can be of wide application.