Drug release behavior of poly(ε-caprolactone)-b-poly(acrylic acid) shell crosslinked micelles below the critical micelle concentration

To explore the potential of shell crosslinked micelle (SCM) as a drug carrier, the drug release behavior of poly(epsilon-caprolactone)-b-poly(acrylic acid) (PCL-b-PAA) SCMs was investigated. PCL-b-PAA was synthesized by ring opening polymerization of epsilon-caprolactone and atom transfer radical polymerization of tert-butyl acrylate, followed by selective hydrolysis of tent-butyl ester groups to acrylic acid groups. The resulting amphiphilic polymer was used to prepare SCMs by crosslinking of PAA corona via amidation chemistry. The drug release behavior of the SCMs was studied, using pyrene as a model drug, and was compared with that of non-crosslinked micelles, especially below the critical micelle concentration (CMC). When the shell layers were crosslinked, the drug release behavior of the SCMs was successfully modulated at a controlled rate compared with that of the non-crosslinked micelles, which showed a burst release of drug within a short time.