| A unique strategy to control bioresorbable polymer lifetime by embedding enzymes in polymer matrices has been developed. Lipase from Candida Antarctica Lipase B (CALB) is surfactant paired enabling it to be organo-soluble and active for hydrolysis of the polymer matrix. The ion-paired lipase prepared by this technique is embedded within the poly(caprolactone) (PCL) matrix. Degradation studies of enzyme embedded PCL films were performed in three different incubation conditions namely i) batch; ii) continuous flow; iii) static (controlled humidity). In our batch studies ion paired CALB (6.5 and 1.65% (w/w)) was reported to degrade the PCL films in 1 day and 18 days respectively. Enzyme-catalyzed degradation of PCL films with embedded CALB (1.6 %-by-wt) under continuous fluid exchange (flow) conditions and in controlled humidity desiccators were also determined. At 0.2 mL/min flow rate, film weight loss reached 85% in 3 days relative to static incubations where 70% degradation occurred in 9 days. However, further increase in flow rate from 0.2 to 0.5 mL/min results in slower weight loss (7 days, 70%) as increased flow rate appears to negatively influence enzyme stability. The removal of degradation products is more efficient leading to formation of a porous matrix where SEM cross sectional images show larger better defined pores under continuous flow conditions. 1.6% CALB-embedded PCL films were incubated in desiccators set at 20, 75 and 95% relative humidity (RH). Water uptake and molecular weight change at 20% RH were insignificant. However, at 75 and 95% RH, by 28 days, %-water content increased to 0.30 and 0.82, and film Mn decreased by 25% to 59300 and 58% to 33900, respectively. From studies performed in embedded enzymatic polymer systems, we have extended our work to develop a new method for micro contact printing (μCP), which involves enzymes that has site-specific recognition domains for the polymer substrates. We have shown that degradation can occur under ambient conditions, at temperature 37 deg C and 30% humidity. A patterned degradation at this micron level wherein PCL films are degraded only along the areas of contact by stamping with CALB has not been reported by soft lithography using PDMS stamp. |
