Bioactive PCL matrices with a range of structural & rheological properties

Safer pharmaceutical and medical device excipients are being sought as alternatives to polyvinyl polymers that are commonly plasticised by carcinogenic phthalates. This paper demonstrates a biodegradable and non-toxic bioactive polymer matrix that can be easily modified through plasticiser addition in the presence of low dosage active pharmaceutical ingredient (API). Poly(ε-caprolactone) (PCL) was selected as an alternative polymer to polyvinyls as it is biodegradable and has high amorphous content, which improves drug solubility. Bulk PCL and various blends with 5 and 25% polyethylene glycol (PEG, a plasticiser and pore former) and 5% nalidixic acid (NA, the API) were processed using extrusion and pressed into plaques. The resultant material properties were investigated in terms of microscopic, morphological and topographical modification. No evidence of miscibility was found by IR. The rheology and contact angle of the matrix could be easily manipulated through the addition of PEG. Increased loading of PEG to 25% (w/w) caused a 10-fold increase in the melt flow index, a similar increase in the elongational viscosity, and a contact angle decrease of 10°, indicating that the resultant fluid was becoming more Newtonian. It was concluded that the structural and rheological properties of the blend, while easily modified through the addition of PEG, were unaffected by the monodispersion of the API, nalidixic acid.