(297e) Analysis of Transient Protein Distribution in Plga Microparticles during Polymer Degradation and in Vitro Release

In light of the potential utilization of the biodegradable polyesters in drug delivery, this study intends to reveal the transient protein distribution profiles in the microparticles over long-term release. Firstly, poly (lactide-co-glycolide) (PLGA 75:25) microparticles containing ovalbumin (OVA) as a model protein were fabricated by double-emulsion (w/o/w) method. Then the in vitro polymer erosion, transient protein distribution profiles and protein release behaviors were investigated. Specifically, the microparticles were incubated at 37 ºC and 250 rpm in PBS buffer (pH 7.4) over a 100-day period; internal protein distribution changes were examined by TEM at various time points; and, the protein release profiles were measured via spectrophotometry using a BCA assay. Three complete sets of consecutive TEM images were obtained as well for OVA-loaded microparticles before and during degradation (0 day, 30 days and 60 days), and the corresponding 3-D images were reconstructed in the software of Amira 3.0 (NIH). The 2-D TEM images clearly illustrated the transient protein distribution in cross-sections of the particle. From the 3-D images, the overall protein distribution of the entire microparticle was vividly reflected (Figure 1). The time-dependent protein distribution shown in TEM images agreed well with the measured protein release profiles. Furthermore, based on the TEM images, a quantitative approach of protein distribution was conducted by pixel analysis. Finally, the distribution function was compared to a diffusion model in ordr to determine the role of diffusion during protein release.

Figure 1 The 3-D image of OVA distribution in PLGA 75:25 microparticles before degradation.