This research aims to develop targeted nanoparticles as drug carriers to the injured arterial wall under fluid shear stress by mimicking the natural binding ability of platelets via interactions of glycoprotein Ib-alpha (GP Ibα) of platelets with P-selectin of damaged endothelial cells (ECs) and/or with von Willebrand factor (vWF) of the subendothelium. Drug-loaded poly (D, L-lactic-co-glycolic acid) (PLGA) nanoparticles were formulated using a standard emulsion method and conjugated with glycocalicin, the external fraction of platelet GPIbα, via carbodiimide chemistry. Surface-coated and cellular uptake studies in ECs showed that conjugation of PLGA nanoparticles with GPIb significantly increased nanoparticle adhesion to P-selectin- and vWF-coated surfaces as well as nanoparticle uptake by activated ECs under fluid shear stresses. In addition, effects of nanoparticle size and shear stress on adhesion efficiency were characterized through parallel flow chamber studies. The observed decrease in bound nanoparticle density with increased particle sizes and shear stresses is also explained through a computational model. Our results demonstrate that the GPIb-conjugated PLGA nanoparticles can be used as a targeted and controlled drug delivery system under flow conditions at the site of vascular injury.

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 Ibα (GP Ibα) and P-selectin on activated endothelial cells, GP Ibα-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 due to its narrow size distribution as a “proof-of-concept”. Using confocol microscopy, fluorescent measurement, 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 Ibα) 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 towards developing a targeted and sustained drug delivery system that can improve shear-regulated particle adhesion and cellular uptake.

The objective of this study was to investigate the physical characteristics of poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) coated with two surfactants, Pluronic or the commonly used polyvinyl alcohol (PVA); and determine their in vitro efficiency as drug carriers for cancer therapy. Free surfactant cytotoxicity results indicated that Pluronic F127 (PF127) was most cytocompatible among the Pluronics tested and hence chosen for coating PLGA NPs for further studies. Release studies using doxorubicin (DOX) as a drug model showed sustained release of DOX from both PVA- and PF127-coated PLGA NPs (PLGA-PVA and PLGA-PF127, respectively) over 28 days. Further, there was no significant difference in human dermal fibroblasts and human aortic smooth muscle cell survival when exposed to both types of NPs. Cellular uptake studies demonstrated that uptake of both nanoparticle types was dose-dependent for both prostate and breast cancer cells. However, these cancer cells internalized more PLGA-PF127 NPs than PLGA-PVA NPs. Moreover, studies showed that drug-loaded PLGA-PF127 NPs not only killed more cancer cells than drug-loaded PLGA-PVA NPs, but also overcame drug resistance in LNCaP, MDA-MB-231, and MDA-MB-468 cancer cells on re-exposure. These results indicate that PLGA-PF127 NPs can form a promising system that not only delivers anti-cancer drugs, but also overcomes drug resistance, which is prevalent in most cancer cells.

Under physiological and pathological conditions, vascular smooth muscle cells (SMC) are exposed to different biochemical factors and biomechanical forces. Previous studies pertaining to SMC responses have not investigated the effects of both factors on SMCs. Thus, in our research we investigated the combined effects of growth factors like Bfgf (basic fibroblast growth factor), TGF-β (transforming growth factor β) and PDGF (platelet-derived growth factor) along with physiological cyclic strain on SMC responses. Physiological cyclic strain (10% strain) significantly reduced SMC proliferation compared to static controls while addition of growth factors bFGF, TGF-β or PDGF-AB had a positive influence on SMC growth compared to strain alone. Microarray analysis of SMCs exposed to these growth factors and cyclic strain showed that several bioactive genes (vascular endothelial growth factor, epidermal growth factor receptor, etc.) were altered upon exposure. Further work involving biochemical and pathological cyclic strain stimulation will help us better understand the role of cyclic strain and growth factors in vascular functions and development of vascular disorders.