<p>This dissertation focuses on enhancing our understanding of microbicide transport mechanisms from gel delivery vehicles into vaginal mucosal tissues through the development and application of novel transport assays. We demonstrated the capabilities of Raman spectroscopy to measure four leading microbicide drugs, Tenofovir, IQP-0528, MIV 150, and Dapivirine, in fluids, microbicide gels, and biological tissues. Strong linear dependences of spectral Raman intensities on drug concentrations suggested that Raman spectrometry could be used in practice for quantitative analysis of drug concentrations in biologically-relevant matrices. Concentration measurements in fluids and tissues demonstrated good correlation with gold standard LC-MS/MS data.</p><p>Next, we investigated the accuracy of confocal Raman measurements of uniform and non-uniform (linear) concentration distributions of Vitamin K in a tissue phantom. A chemometric method was used to perform the quantitative analyses of concentration distributions and to correct for signal attenuation due to elastic scattering that increased with depth into the tissue. The measured concentration distributions demonstrated an expected trend of the linear profile up to a depth of 180 to 200 μm, thereby validating the confocal Raman approach for concentration profiling in scattering matrices.</p><p>We developed a label-free assay using Raman spectroscopy to quantify the drug diffusion coefficient within a gel. The concentration distributions of Tenofovir in gel over time and space were measured and the concentration profiles were fitted to PDE diffusion models to obtain diffusion coefficients. The gel was tested undiluted, and in 10-50% serial dilutions with vaginal fluid simulant, to capture the range of conditions that likely occur in vivo. Tenofovir exhibited diffusion-like behavior that could be fitted to the diffusion model reasonably well (R2: 0.86 – 0.99). The dilutions with vaginal fluid simulant increased diffusion coefficients of Tenofovir in the test gel by up to 50%. </p><p>Finally, we developed a real-time transport assay using a combined CRS-OCT instrument constructed by our team to study and distinguish the microbicide transport mechanisms between epithelial and stromal layers of vaginal tissue. Measurements were corrected by taking into account the effects of out-of-focus light contributions from the Tenofovir overlying gel layer. Data were translated to fundamental transport properties, the diffusion and partition coefficients. The diffusion coefficient in stroma was found to be 2 to 15 times larger than that in epithelium, suggesting that epithelium could present a diffusion barrier to Tenofovir transport in vaginal tissue.</p><p>The series of transport assays developed here can provide useful information of microbicide transport mechanisms. The transport parameters can be used as salient measures to investigate the drug delivery performance of different drugs and gel vehicles. The parameters are important inputs to the deterministic transport models that predict the gels’ dosing regimen in PK studies. Collectively, this thesis will contribute to a better understanding of anti-HIV drug delivery and pharmacokinetics, and be of significant help in creation of products for prevention of HIV/AIDS.</p> / Dissertation
| Identifer | oai:union.ndltd.org:DUKE/oai:dukespace.lib.duke.edu:10161/11351 |
| Date | January 2015 |
| Creators | Chuchuen, Oranat |
| Contributors | Katz, David F. |
| Source Sets | Duke University |
| Detected Language | English |
| Type | Dissertation |
Page generated in 0.0018 seconds