Morphological characterization of encapsulated fish oil with β-cyclodextrin and polycaprolactone

The present study characterized the morphology of fish oil beta-cyclodextrin (beta-CD) complex or fish oil encapsulated with polycaprolactone (PCL) by transmission electron microscopy (TEM) observation using low or high voltage with or without phosphotungstic acid (PTA) staining. Emulsion-diffusion or self-assembly aggregation methods were used to encapsulate fish oil in PCL or beta-CD. PCL spheres averaged 200 nm in diameter. However, beta-CD spheres were significantly larger and dependent on host:guest mixing ratio (w:w), being approximately 300 nm and 600 nm at ratios of 10:1 and 10:10, respectively. TEM enabled the visual distinction of core and wall materials, and revealed that fish oil was encapsulated with a different structure depending on whether the self-resembling aggregation of beta-CD or emulsion-diffusion method with PCL was used. Hexagonal-type beta-CD aggregates were evident at a mixing ratio 10:1 between beta-CD and fish oil. The hexagonal arrangement of beta-CD enveloped the fish oil with a thick (100-150 nm) membrane. Incorporation of beta-CD with fish oil at a 10:10 mixing ratio produced a worm-type of beta-CD. It is suggested that the fish oil might be physically blended without wrapping with beta-CD. For the PCL formulation, the lower voltage TEM operating condition better enabled the observation of the thin PCL layer (1-2 nm) encapsulating the fish oil. Nanosizer (R) and TEM yielded comparable measurements. (C) 2009 Elsevier Ltd. All rights reserved.