Preclinical development and clinical translation of a PSMA-targeted docetaxel nanoparticle with a differentiated pharmacological profile.

We describe the development and clinical translation of a targeted polymeric nanoparticle (TNP) containing the chemotherapeutic docetaxel (DTXL) for the treatment of patients with solid tumors. DTXL-TNP is targeted to prostate-specific membrane antigen, a clinically validated tumor antigen expressed on prostate cancer cells and on the neovasculature of most nonprostate solid tumors. DTXL-TNP was developed from a combinatorial library of more than 100 TNP formulations varying with respect to particle size, targeting ligand density, surface hydrophilicity, drug loading, and drug release properties. Pharmacokinetic and tissue distribution studies in rats showed that the NPs had a blood circulation half-life of about 20 hours and minimal liver accumulation. In tumor-bearing mice, DTXL-TNP exhibited markedly enhanced tumor accumulation at 12 hours and prolonged tumor growth suppression compared to a solvent-based DTXL formulation (sb-DTXL). In tumor-bearing mice, rats, and nonhuman primates, DTXL-TNP displayed pharmacokinetic characteristics consistent with prolonged circulation of NPs in the vascular compartment and controlled release of DTXL, with total DTXL plasma concentrations remaining at least 100-fold higher than sb-DTXL for more than 24 hours. Finally, initial clinical data in patients with advanced solid tumors indicated that DTXL-TNP displays a pharmacological profile differentiated from sb-DTXL, including pharmacokinetics characteristics consistent with preclinical data and cases of tumor shrinkage at doses below the sb-DTXL dose typically used in the clinic.

Shear-regulated uptake of nanoparticles by endothelial cells and development of endothelial-targeting nanoparticles.

The purpose of this research project was to develop nanoparticles with improved targeting, adhesion, and cellular uptake to activated or inflamed endothelial cells (ECs) under physiological flow conditions. Our hypothesis is that by mimicking platelet binding to activated ECs through the interaction between platelet glycoprotein Ibalpha (GP Ibalpha) and P-selectin on activated endothelial cells, GP Ibalpha-conjugated nanoparticles could exhibit increased targeting and higher cellular uptake in injured or activated endothelial cells under physiological flow conditions. To test this hypothesis, fluorescent-carboxylated polystyrene nanoparticles were selected for the study as a model particle because of its narrow size distribution as a "proof-of-concept." Using confocal microscopy, fluorescent measurements, and protein assays, cellular uptake properties were characterized for these polystyrene nanoparticles. The study also found that conjugation of 100-nm polystyrene nanoparticles with glycocalicin (the extracellular segment of GP Ibalpha) significantly increased the particle adhesion on P-selectin-coated surfaces and cellular uptake of nanoparticles by activated endothelial cells under physiological flow conditions. The results demonstrate that these novel endothelial-targeting nanoparticles could be the first step toward developing a targeted and sustained drug delivery system that can improve shear-regulated particle adhesion and cellular uptake.

Factorial analyses of photopolymerizable thermoresponsive composite hydrogels for protein delivery.

A smart protein delivery system for wound healing applications was developed using composite nanoparticle hydrogels that can release protein in a temperature-responsive manner. This system can also be formed in situ in the presence of ultraviolet light and Irgacure 2959 photoinitiator. The system consists of temperature-sensitive poly(N-isopropylacrylamide-co-acrylamide) (PNIPAM-AAm) nanoparticles embedded in a poly(ethylene glycol) diacrylate (PEGDA) matrix. A factorial analysis was performed to evaluate the effects of PEGDA concentration (10% and 15% w/v) and PEGDA molecular weight (MW; 3.4 kDa and 8 kDa), as well as PNIPAM-AAm nanoparticle concentration (2% and 4% w/v) and temperature (23 degrees C and 40 degrees C) on the protein release profiles and swelling ratios of the hydrogels. Results indicate that PNIPAM-AAm nanoparticle concentration and temperature were the most important factors affecting the protein release during the burst release phase. Additionally, PEGDA MW was the most important factor affecting the protein release in the plateau region. It was also important in controlling the hydrogel swelling ratio. A dual-layered hydrogel was further developed to produce a protein delivery system with a better sustained release. These findings have improved our understanding of the composite hydrogel systems and will help in tailoring future systems with desired release profiles. FROM THE CLINICAL EDITOR: A smart protein delivery system for wound healing applications using composite nanoparticle hydrogels that can release protein in a temperature-responsive manner is reported in this paper. Systems like this may aid in optimal would healing in the surgical and trauma-related settings.

Cytocompatibility studies of an in situ photopolymerized thermoresponsive hydrogel nanoparticle system using human aortic smooth muscle cells.

We have been investigating thermoresponsive hydrogel nanoparticle composite networks to develop photopolymerized hydrogels to deliver drugs for prevention of restenosis after angioplasty. These composite systems can form a gel under physiological conditions and release drugs in response to temperature changes. Our novel system, consisting of poly(N-isopropylacrylamide) thermoresponsive nanoparticles, photo cross-linker poly(ethylene glycol) diacrylate, and UV photoinitiator, 2-hydroxy-1-[4-(2-hydroxyethoxy) phenyl]-2-methyl-1-propanone-1-one (Irgacure 2959), would be photopolymerized in situ in the presence of UV light. The focus of this study was to evaluate the effects of photoinitiator and UV exposure on human aortic smooth muscle cells (HASMCs). We found that the exposure to UV light did not significantly affect the cellular survival within doses required for photopolymerization. The photoinitiator was cytocompatible at low concentrations (< or = 0.015% w/v); however, cytotoxicity increased with increasing photoinitiator concentrations. In addition, free radicals formed in the presence of a photoinitiator and UV light caused significant levels of cell death. An antioxidant (free radical scavenger), ascorbic acid, added to the cell media, significantly improved relative cell survival but increased the hydrogel gelation time. Finally, HASMC survival when exposed to all potential cytotoxic components was also evaluated by exposing HASMCs to media incubated with our composite hydrogels. In summary, our studies show that the photoinitiator and free radicals are responsible for the cytotoxicity on HASMCs, and the addition of antioxidants can significantly reduce these harmful effects.