Acta Poloniae Pharmaceutica ñ Drug Research, Vol. 65 No. 6 pp. 763ñ766, 2008 ISSN 0001-6837 Polish Pharmaceutical Society Hydrogels are continuous hydrophilic three- dimensional polymeric networks able to swell large amounts of water or aqueous fluid, without dissolu- tion (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 report- ed (3). Then introduced were biological adhesives, soft tissue replacements, wound healing supports, membranes of the drug releasing systems, sophisti- cated self-assembling ìsmartî polymers and the most widely used: lubricious coatings for less inva- sive devices, having the best cost to effect ratio. Hydrogel coating as a method for solid sub- strate surface modification, beside advantages like improving material biocompatibility (4), hydrophilization and lubrication (5), brings the addi- tional 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 sub- sequent 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 The method for coating of medical polymeric devices by water insoluble hydrogel, based on inter- polymer of polyurethane (PUR) and polyvinylpyrrolidone (PVP), previously proposed by Micklus (5), was modified and developed to avoid involving diisocyanates, monomers or any polymerization promoters that can be harmful and difficult to remove (9). This dip-coating technique briefly consists of one (one solution of precursors; less stabile) or two steps (each precursor of inter- polymer in separate bath), when the solid polymeric substrate, poly(vinyl chloride) (PVC) or polysilox- ane (silicone), is immersed for 15 to 60 seconds in solution of each polymer (1-3 wt % in organic sol- vents) and air-dried. Materials High molecular weight (MW = 360 000) 1- ethenyl-2-pyrrolidinone homopolymer (polyvinyl- pyrrolidone K90, PVP) was purchased from Fluka; the term polyurethane (PUR) refers to ESTANE 5715P; 5-chloro-2-(2,4-dichlorophenoxy)phenol (Irgasan DP 300, triclosan) purchased from Brenntag; poly(iminoimidocarbonyl)iminohexam- ethylene hydrochloride (polyhexamethylene biguanide, PHMB) was a sample gift from Scunder, Shanghai; tested PVC catheters were a gift of the manufacturer (Galmed, Bydgoszcz); phosphate buffered saline (PBS) was the composition of NaCl (0.8 wt%), KCl (0.02 wt%), KH 2 PO 4 (0.02 wt%), Na 2 PO 4 . 12H 2 O (0.023 wt%) and methanol or ethanol (20 vol%) in distilled H 2 O; all solvents and inorganic salts were of analytical grade. POLYVINYLPYRROLIDONE-POLYURETHANE INTERPOLYMER HYDROGEL COATING AS A LOCAL DRUG DELIVERY SYSTEM KATARZYNA A. KAèMIERSKA*, KATARZYNA KUC and TOMASZ CIACH Warsaw University of Technology, Faculty of Chemical Engineering, 1, WaryÒskiego St., 00-645 Warsaw, Poland Keywords: hydrogel coating, polyvinylpyrrolidone, triclosan, polyhexamethylene biguanide hydrochloride, dissolution test 763 * Corresponding author: kazmierska@ichip.pw.edu.pl