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Mixed-interpenetrated polymeric networks based on sodium alginate (ALG) and poly(N-isopropylacryl amide) (PNI-PAAm) covalently cross-linked with N,N'-methylenebisacrylamide are studied for their biocompatibility, nontoxicity, and biodegradability aiming their application in drug delivery. The presence of drug-polymeric matrix interactions and the distribution of the drug in the polymeric network for theophylline-loaded ALG/PNIPAAm hydrogels are also investigated by spectroscopic and microscopic methods. The quantitative evaluation of theophylline loaded hydrogels performed by NIR-CI technique shows a better drug entrapment and a higher homogeneity of the samples with increased alginate content. The thermal behavior of the hydrogels is significantly modified by theophylline presence. The application of the ALG/PNIPAAm hydrogels as carriers for sustained drug release formulations was assessed by the theophylline release tests performed both by in vitro and in vivo studies. V C 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40733.

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The xanthan/chondroitin sulfate (X/CS) hydrogels, obtained by a crosslinking technique, were evaluated in vitro and in vivo as matrices for theophylline release. The influence of pH of simulated physiological media on the X/CS swelling behaviour at 37°C was investigated. The hydrogels theophylline loading degree was evaluated by near infrared chemical imaging (NIR-CI) technique and confirmed also by FT-IR spectroscopy; the drug loading was about 77.5% based on PLS-DA prediction (Partial least squares-Discriminate Analysis). The release profiles of theophylline from X/CS hydrogels in simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) depend on CS content. The release mechanisms were controlled by the drug solubility and ionic properties of the polymers. In vivo theophylline delivery was done by oral administration. Pharmacokinetic analysis revealed sustained-release characteristics for 50/50 X/CS theophylline-loaded formulation compared with raw theophylline which was rapidly absorbed, distributed and eliminated. A good in vitro-in vivo correlation was found.

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