Micro-CT in drug delivery

Abstract

Micro-computed tomography (micro-CT) has not to date been fully exploited in the area of controlled drug delivery despite its capability for providing detailed, 3-D images of morphology and the opportunity this presents for exploring the relationships between delivery device formulation, structure and performance. Micro-CT was used to characterize the internal structure of polycaprolactone (PCL) matrix-type devices incorporating soluble particulates (lactose Mw 342.30, gelatin Mw 20–25 kDa) as models of hydrophilic bioactives or pore-forming excipients. Micro-CT images confirmed that the lactose and gelatin particles were uniformly dispersed throughout the PCL phase and that efficient delivery of 95–100% of each species in 9 days involved transport from the matrix core. Quantitative analysis of micro-CT images provided values for matrix macroporosity, which were within 15% of the theoretical value and revealed uniform porosity throughout the samples. Total release of protein occurred in 9 days (PBS, 37 °C) from matrices containing a high protein load (44% w/w) and was independent of particle size. Measurements of equivalent pore diameter and frequency distribution identified a large population of sub-40 μm pores in each material, indicative of a high density of connecting channels between particles which facilitates protein transport through the matrices.