Drug-Integrating Amphiphilic Nano-Assemblies: 3. PEG-PPS/Palmitate Nanomicelles for Sustained and Localized Delivery of Dexamethasone in Cell and Tissue Transplantations.

Background

Glucocorticoids are an important class of therapeutics used in a variety of applications, including allotransplantations. Dexamethasone (Dexa) is well-known for its strong anti-inflammatory, immunosuppressive, and anticancer properties. However, its clinical use is often limited by its poor water solubility, poor pharmacokinetics, and high likelihood of systemic side effects.

Methods

To address the issues, we tested a combined strategy where our original Drug-Integrating Amphiphilic Nano-Assemblies (DIANAs), a class of self-assembling polymeric nanoparticles designed for controlled drug release, were used to solubilize and deliver dexamethasone palmitate (DexP), a hydrophobic prodrug of dexamethasone.

Results

The palmitate chains of the prodrug can form strong van der Waals interactions with the hydrophobic moieties of the PEG-PPS block copolymer used here. In water, this resulted in the self-assembling of stable dexamethasone palmitate-PEG-PPS nanomicelles, termed DexP-nMICs, with a 25 nm average diameter that slowly released Dexa over more than two weeks.

Conclusions

Here we demonstrated that DexP-nMICs can carry elevated amounts of Dexa-increasing its solubility in water-prolong circulation in its pharmacologically active form in vivo and provide passive targeting to inflammation sites. The anti-inflammatory efficacy of DexP-nMICs was first confirmed in vitro on stimulated macrophages, demonstrating a significant reduction in cytokine secretion. An allogeneic mouse skin transplant model, used to assess the therapeutic potential of DexP-nMICs in vivo, confirmed its ability to provide graft-targeted delivery and prolong graft survival as compared to the unformulated parent drug. Therefore, DexP-nMICs are a promising candidate for sustained and localized use of anti-inflammatory drugs in cell and tissue transplantations.