The drug release characteristics of calcium alginate hydrogels, (Ca-Alg), under an electric field assisted transdermal drug delivery system were systematically investigated. The Ca-Alg hydrogels were prepared by the solution-casting using CaCl(2) as a crosslinking agent. The diffusion coefficients and the release mechanism of the anionic model drugs, benzoic acid and tannic acid, and a cationic model drug, folic acid on the Ca-Alg hydrogels were determined and investigated using a modified Franz-Diffusion cell in an MES buffer solution of pH 5.5, at a temperature of 37°C, for 48 h. The influences of the crosslinking ratio, -the mole of the crosslinking agent to the mole of the alginate monomer-mesh size, model drug size, drug charge, electric field strength, and electrode polarity were systematically studied. The drug diffusion coefficient decreased with an increasing crosslinking ratio and drug size for all of the model drugs. The drug diffusion coefficient is precisely controlled by an applied electric field and the electrode polarity depending on the drug charge, suitable for a tailor-made transdermal drug delivery system.

Poly(p-phenylenevinylene) (PPV) was chemically synthesized via the polymerization of p-xylene-bis(tetrahydrothiophenium chloride) monomer and doped with H2SO4. To improve the electrical conductivity sensitivity of the conductive polymer, Zeolites Y (Si/Al = 5.1, 30, 60, 80) were added into the conductive polymer matrix. All composite samples show definite positive responses towards NH4NO3. The electrical conductivity sensitivities of the composite sensors increase linearly with increasing Si/Al ratio: with values of 0.201, 1.37, 2.80 and 3.18, respectively. The interactions between NH4NO3 molecules and the PPV/zeolite composites with respect to the electrical conductivity sensitivity were investigated through the infrared spectroscopy.

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