Chitosan/PVA

Poly(vinyl alcohol)-gel spheres with chitosan (PVA-GS/Ch) or without chitosan (PVA-GS) were prepared to control the GI transit time of drugs, and their particles were 5-10 pm [26]. PVA-GS/Ch displayed a longer small-intestinal transit time than PVA-GS. The transit rate was considered to decrease by the adhesion of chitosan to the intestinal mucus layer. PVA-GS/Ch and PVA-GS were loaded with theophylline and ampicillin. These released the drugs in a similar manner. The drugs were released almost completely at 4 h after the start of the release test. Both the gel spheres containing theophylline exhibited a bioavailability similar to that of the theophylline solution. Also, the bioavailability of ampicillin was greater in PVA-GS/Ch than in the PVA-GS and ampicillin solution the bioavailability of PVA-GS/Ch was approximately 150% of that of ampicillin solution (Table 3.2). As theophylline is rapidly absorbed in... 

Duan B et al (2007) Degradation of electrospun PLGA-chitosan/PVA membranes and their cytocompatibility in vitro. J Biomater Sci Polym lid 18(1) 95—115... 

Duan B et al (2006) A nanofibrous composite membrane of PLGA-chitosan/PVA prepared by electrospinning. Eur Polym J 42(9) 2013-2022... 

Ferdous, S., Mustafa, A.I. and Khan, M. (2003) A Study on mechanical properties of photo-cured films of chitosan/PVA and PEO/PVA blend with acrylic monomers. Journal of Macromolecular Science, Part A. Pure and Applied Chemistry, A40(8), 817-832. 

At first, 2g chitosan was dispersed in lOOmL distilled water and stirred for 30min. One milliliter of acetic acid was added into the chitosan aqueous solution, and mixed for 24 h at room temperature. The PVA powder of Nacalai Tesque. Inc. was used as a sample, and possessed a degree of polymerization of 2000% and 98% hydrolysis. The PVA powders were dissolved in distilled water to maintain a 3% solution concentration and stirred for 40 min at 95°C. After, the solution was cooled down to room temperature. The corresponding solutions of chitosan and PVA, respectively, were simultaneously poured into a flask in the desired proportion of chitosan/PVA and stirred for 3-5 h at room temperature. The weight compositions chosen were 100/0 (chitosan homopolymer), 61/39, 50/50, 40/60, 30/70, 22/78, and 0/100 (PVA homopolymer). The mixed solution was poured into a petri-dish and the distilled water was allowed to evaporate to produce the cast film. The resulting film was first immersed into 4% sodium hydroxide for 2h to neutralize the cast film and then washed well with distilled water. Finally, the film was vacuum-dried for 1 day to remove residual traces of water and then placed inside a desiccator to avoid moisture absorption. 

The densities of all the chitosan/PVA blend films were measured using a density gradient tube with n-heptane and carbon tetrachloride as the medium at 20°C. Since the density of the blend film was dependent on a complete absence of moisture within the film, great care was taken to remove moisture of the film. The samples were cut into fragments, washed through an ultrasonic treatment in ethanol, and then dried in vacuum for 1 day prior to measuring the density. 

The surface of the chitosan/PVA blend fihn was analyzed by electron spectroscopy for chemical analysis (ESCA-850, Shimadzu). The sample was irradiated with monochromated MgKa x-rays (8kV, 30 mA) and the scanning speed was 0.05 V/s. 

Figure 9.3 shows the x-ray diffraction intensity curves from chitosan, PVA and four chitosan/ PVA blend films (61/39, 50/50, 40/60, 22/78) measured at 25°C, respectively. The curves were drawn in the range of twice the Bragg angle from 16° to 24°. The open circles show the overlapped experimental intensity. Regarding the preliminary experiments, the temperature dependence of the... 

Figure 9.6 shows the temperature dependence of the storage modulus (E ) and loss modulus (E") at a frequency of 10 Hz for chitosan (100/0), chitosan/PVA blend (40/60 and 22/78), and PVA (0/100) films. The results for the second heating run were shown as figures. The first heating run was... 

Further analysis of the chitosan/PVA blend film was done in terms of the simple additivity of the complex moduli of chitosan and PVA. Theoretical calculations were carried out as a function of chitosan content by using the three-dimensional model in Figure 9.7 (Matsuo et al. 1980, 1990, 2001), in which the chitosan layers are surrounded by a PVA plane, so that the strains of the two phases at the boundary in three directions are identical. The parameters 8, n, and p, correspond to the fraction length of chitosan in the three directions, and the volume fraction of chitosan is given as Sop. By using the model system, the complex moduli of the blend may be given by... 

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