PVA−DNA Cryogel Membranes: Characterization, Swelling, and Transport Studies

Double-stranded (ds) DNA from salmon testes has been incorporated into PVA hydrogels obtained by a technique of repeated freezing and thawing. The cryogels obtained are free of potential toxic species like chemical cross-linkers, and consequently, they can be used in pharmaceutical or medical applications. These cryogels show a good mechanical resistance and a white and opaque appearance caused by a heterogeneous porous structure. Encapsulated DNA molecules can be in a compacted or an extended conformation in the PVA matrix and can be controlled by tailoring the degree of crystallinity of the PVA network; this is supported by fluorescence microscopy and UV and FTIR spectroscopic studies. The two forms of encapsulated DNA were observed for different types of matrixes: an extended one in a more crystalline network and a globular one in a more amorphous one. Different associations of base pairs have also been observed. PVA cryogel crystallinity could be tailored by the cryogel contact with different salt solutions. Cryogel surface (scanning electron microscopy) and bulk morphology (porosimetry), swelling, DNA retention, and delivery kinetics have also been studied. All these investigations clearly show strong interactions between PVA and DNA

A permittivity study for PVA membranes, obtained by freeze-thaw technique

Late diffusion or selective diffusion through polymeric membranes has various applications in separation processes, environmental protection, pharmaceutics for drug delivery systems, etc. The aim of this work is to present the results of some ions diffusion through poly(vinyl alcohol) [PVA] hydrogel membranes, obtained by freeze-thaw technique. The diffusion of potentially toxic ions -Pb(II)- and of alkaline ions like Na+ and K+ is tested using conductometry, flame photometry and atomic absorption spectrometry. The membrane permitivitty is calculated for every ionic species and the opportunity is studied to use these membranes in environmental protection, for waste water purification. The modifications of the PVA structure have been made by mixing the PVA solution with some natural products (beta-cyclodextrine or chitosan) or by compounding PVA hydrogel with Cu2+