Implantable
devices are versatile and promising drug delivery systems,
and their advantages are well established. Of these advantages, long-acting
drug delivery is perhaps the most valuable. Hydrophilic compounds
are particularly difficult to deliver for prolonged times. This work
investigates the use of poly(caprolactone) (PCL)-based implant
coatings as a novel strategy to prolong the delivery of hydrophilic
compounds from implantable devices that have been prepared by additive
manufacturing (AM). Hollow implants were prepared from poly(lactic
acid) (PLA) and poly(vinyl alcohol) (PVA) using fused filament fabrication
(FFF) AM and subsequently coated in a PCL-based coating. Coatings
were prepared by solution-casting mixtures of differing molecular
weights of PCL and poly(ethylene glycol) (PEG). Increasing the proportion
of low-molecular-weight PCL up to 60% in the formulations decreased
the crystallinity by over 20%, melting temperature by over 4 °C,
and water contact angle by over 40°, resulting in an increased
degradation rate when compared to pure high-molecular-weight PCL.
Addition of 30% PEG to the formulation increased the porosity of the
formulation by over 50% when compared to an equivalent PCL-only formulation.
These implants demonstrated
in vitro
release rates
for hydrophilic model compounds (methylene blue and ibuprofen sodium)
ranging from 0.01 to 34.09 mg/day, depending on the drug used. The
versatility of the devices produced in this work and the range of
release rates achievable show great potential. Implants could be specifically
developed in order to match the specific release rate required for
a number of drugs for a wide range of conditions.
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