Polymer microneedles fabricated from PCL and PCL/PEG blends for transdermal delivery of hydrophilic compounds

The merits of low-cost, easy-fabrication, and FDA-approved biodegradable poly-ε-caprolactone (PCL) and dissolving poly(ethylene glycol) (PEG) have initiated our research on developing a gentle fabrication method consisting of solution-casting process in sequence with thermal press molding for preparing microneedle (MN) patches with model hydrophilic compounds of rhodamine 6G and fluorescein isothiocyanate (FITC)-labeled collagen encapsulated in the MN tip. The best PCL/PEG molar ratio of 1/19 was selected for molding the tip after considering the MN performances from mechanical compression and in vitro drug-release tests. A modified Korsmeyer and Peppas model was further proposed to simulate and elucidate the initial burst and slow dissociation-diffusion of the model drugs into the phosphate buffer. Moreover, the confocal microscope images at the insertion depth around 200 μm to the porcine skin together with drug permeation tests in a Franz-type diffusion cell showed that both drugs might rapidly dissolve and diffuse across the skin. These results suggest that the designed MN patches may serve as a useful device for transdermal delivery of hydrophilic biomolecules in a short-term manner.