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

<b>Background:</b> 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. <b>Methods</b>: 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. <b>Results</b>: 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. <b>Conclusions</b>: 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.