Polyvinylpyrrolidone-polyurethane interpolymer hydrogel coating as a local drug delivery system.

Hydrogels are continuous hydrophilic threedimensional polymeric networks able to swell large amounts of water or aqueous fluid, without dissolution (1, 2). They are extensively exploited in the field of biomedical applications, since the middle of the twentieth century, when the first synthetic hydrogel poly(2-hydroxyethyl methacrylate) (PHEMA), a material for contact lenses, was reported (3). Then introduced were biological adhesives, soft tissue replacements, wound healing supports, membranes of the drug releasing systems, sophisticated self-assembling ìsmartî polymers and the most widely used: lubricious coatings for less invasive devices, having the best cost to effect ratio. Hydrogel coating as a method for solid substrate surface modification, beside advantages like improving material biocompatibility (4), hydrophilization and lubrication (5), brings the additional possibility of the active agent incorporation during the coating process (6, 7). Thus hydrogel modified surface have an advantage over unmodified one, while it can serve as a drug reservoir for a local drug delivery (8). There are cases when drug dosage time should last at least few hours, but no longer than 3 days. It can be desirable in case of implantation of devices like tracheotomy tubes, when anti-inflammatory active substance should be released at the very beginning to prevent later side effects like tracheal stenosis, but later can not interrupt normal cell divisions in subsequent levels of healing process and epithelium formation. In case of hydrophilic matrix with hydrophobic drug these profile can be easy obtained due to its behavior as the swelling controlled drug release system. EXPERIMENTAL