Controlled degradation of poly-ε-caprolactone for resorbable scaffolds

A lipase from Burkholderia cepacia was successfully adsorbed on the surface of halloysite nanotubes and the coated tubes were incorporated into poly-ε-caprolactone (PCL). The efficiency of the halloysite in the adsorption of the enzyme was characterized by the total protein content determined with the Bradford method. The activity of the adsorbed enzyme was estimated by the kinetic resolution of racemic 1-phenylethanol. The immobilized enzyme was mixed with the polymer and compression molded films were prepared at 70 °C. Activity measurements proved that the enzyme remains active even after adsorption; in fact, larger activities were measured for the immobilized enzyme than for the neat enzyme preparation. The supported enzyme degraded PCL efficiently, the rate of degradation depended on the amount of enzyme adsorbed. The kinetics of degradation was described quantitatively with an appropriate model accounting for two of the three steps of the process, i.e. degradation and the denaturation of the enzyme. The determination of time constants allows the adjustment of degradation rate. This is the first time that the enzyme, which catalyzes degradation, is incorporated into the polymer, and not into the degradation medium, thus allowing the preparation of resorbable scaffolds with controlled lifetime.