Preparation, Characterization, and Drug Release Properties of Poly(2-hydroxyethyl methacrylate) Hydrogels having b-Cyclodextrin Functionality Serap Demir, M. Vezir Kahraman, Nil Bora, Nilhan Kayaman Apohan, Ay¸ se Ogan Department of Chemistry, Faculty of Art & Science, Marmara University, 34722 Go ¨ztepe-Istanbul, Turkey Received 8 May 2007; accepted 21 January 2008 DOI 10.1002/app.28284 Published online 17 April 2008 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: A new b-cyclodextrin urethane-methacry- late monomer was synthesized from the reaction of tolu- ene-2,4-diisocyanate, 2-hydroxyethyl methacrylate (HEMA), and b-cyclodextrin (b-CD). Based on inclusion character of b-CD, a series of hydrogels were prepared by irradiating the mixtures of b-cyclodextrin urethane-methacrylate monomer (b-CD-UM), poly(ethylene glycol) diacrylate (PEG-DA), HEMA, and the photoinitator. Gel percentages and equilibrium swelling ratios (%) of hydrogels were investigated. It was observed that the equilibrium-swelling ratio increased with increasing b-CD-UM content in the hydrogel composition. SEM images demonstrated that b- CD-UM based hydrogel have porous fractured surface. In this study four different drug molecules, salicylic acid, sul- fathiazole, rifampicin, and methyl orange as model drug, which are capable of forming inclusion complexes with b-CD were chosen. For sulfathiazole and rifampicin, the drug loadings are very low (0.04 and 0.008 mmol/g dry gel), whereas methyl orange and salicylic acid drug uptakes are found as 0.15 and 0.18 mmol/g dry gel, respectively. The incorporation of b-CD-UM comonomer into the gel slightly reduces the methyl orange and sali- cylic acid releases. However, a significant enhancement was achieved in the case of sulfathiazole delivery. It can be concluded that the inclusion complex formation capa- bility of b-CD moiety increases the drug release by improving the aqueous solubility of hydrophobic drugs. On the other hand, in the case of hydrophilic drugs, the drug release retards by forming strong drug-b-CD com- plex and reducing the drug diffusivity. Ó 2008 Wiley Peri- odicals, Inc. J Appl Polym Sci 109: 1360–1368, 2008 Key words: b-cyclodextrin; photoinitiation; drug release; inclusion complex; hydrogel INTRODUCTION The hydrogels represent an important class of bio- materials in biotechnology and medicine. Their biocompatibility allows them to be considered for medical applications, whereas their hydrophilicity can import desirable release characteristics to con- trolled and sustained release formulations. 1 Although hydrogels are available in various physi- cal forms, such as discs, powders, or microspheres, they are generally glassy in the dehydrated state, but swell to become elastic gels upon water absorption. In drug delivery applications, the entrapped drug dif- fuses through the swollen network into the surround- ing aqueous medium. 2–4 Various characteristics in- cluding gel structure, reactive sites, and crosslinking degree are considered for describing the overall per- formance of hydrogels in drug release applications. Moreover, some other factors, namely gel-drug inter- actions, still play an important role in determining release kinetics. In particular, the modification of the drug mobility through the swollen polymer can be used to modulate release. 5 One of the possible strat- egies is the introduction of a third component into the release device, which is able to decrease the effective mobility of the drug in a controlled way. It is well-known that cyclodextrins (CDs) possess remarkable ability to include a wide range of guest molecules via noncovalent interactions into their hydrophobic cavities. 6–8 The ability to form inclusion complexes depends on the size and polarity of the host molecule. This unique behavior leads CDs to have wide spread applications in the biomedical and phar- maceutical fields. 9–12 It is found that the incorporation of the CDs into polymeric drug release systems could change the drug-polymer interactions and as a result, the mechanisms of drug release may be modified. 13–16 Among CDs, b-CD and its derivatives are the first choices because of their suitable cavity sizes. It has 21 hydroxyl groups with 7 primary and 14 second- ary hydroxyls. All of these hydroxyl groups are available as starting points for structural modifica- tions. Previously Sreenivasan reported the coupling of b-CD to polyurethane using 2,4-toluene diisocya- Correspondence to: N. Kayaman-Apohan (napohan@mar- mara.edu.tr). Contract grant sponsor: Marmara University, Commis- sion of Scientific Research Project; contract grant number: FEN-YLS-290506-0123. Journal of Applied Polymer Science, Vol. 109, 1360–1368 (2008) V V C 2008 Wiley Periodicals, Inc.