Nanoparticles Containing Anti-inflammatory Agents as Chemotherapy Adjuvants II: Role of Plasma Esterases in Drug Release

Le résumé fourni par la source

The pre-administration of the anti-inflammatory drugs dexamethasone (DEX) and cortisone acetate reduces toxicity and enhances efficacy of anticancer agents in murine models and in human clinical trials (1–5). We previously reported on the formulation of the lipophilic dexamethasone palmitate ester (DEX-P) in nanoparticles (NPs) employing a microemulsion template engineering technique to achieve tumor-specific delivery of dexamethasone (6). The nanoparticles exhibited significantly enhanced stealth properties as indicated by reduced macrophage uptake and decreased adsorption of opsonin proteins in in vitro assays (6). Unexpectedly, preliminary biodistribution studies of NPs containing [3H]-DEX-P in tumor-bearing mice showed that the radiolabel was cleared from the circulation rapidly and exhibited high liver uptake. Our previous in vitro release studies demonstrated that rapid release of the radiolabel from the NPs was observed when 10% mouse plasma was used as the medium, while nominal release was observed in phosphate-buffered saline (PBS) buffer (6). Esterolysis of NP-associated DEX-P was presumed to be the main cause for the rapid drug release in plasma, as most of the released radioactivity was in the form of DEX and not DEX-P. High degradation rates of ester prodrugs in rodent plasma has been attributed to increased esterase activity, while only minimal degradation in human plasma has been observed (7–9). Based on our observation of the release of [3H]-DEX from NPs in mouse plasma, we studied the release of DEX from nanoparticles in various plasma sources as a guide for the design of future in vivo experiments.

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