Clonazepam release from bioerodible hydrogels based on semi-interpenetrating polymer networks composed of poly(epsilon-caprolactone) and poly(ethylene glycol) macromer

Poly(ethylene glycol)(PEG) macromers terminated with acrylate groups and se mi-interpenetrating polymer networks (SIPNs) composed of poly(epsilon-capro lactone)(PCL) and PEG macromer were synthesized to obtain a bioerodible hyd rogel. Polymerization of PEG macromer resulted in the formation of cross-li nked gels due to the multifunctionality of macromer. Glass transition tempe rature (T-g) and melting temperature (T-m) of PEG networks and PCL in the S IPNs were inner-shifted, indicating an interpenetration of PCL and PEG chai ns. Water content in the SIPNs increased with increasing PEG weight fractio n due to the hydrophilicity of PEG. The amount of clonazepam (CNZ) released from the SIPNs increased with higher content in the SIPNs, lower drug load ing, lower concentration of PEG macromer during the SIPNs preparation, and higher molecular weight of PEG. In particular, a combination with low PEG c ontent and low CNZ solubility in water led to long-term constant release fr om these matrices in vitro and in vivo. (C) 1999 Elsevier Science B.V. All rights reserved.