Polymeric nanoparticles have gained attention for their wide range of utilizations in biomedical applications including but not limited to drug delivery, non-viral DNA delivery, and imaging. We have previously reported the fabrication of anisotropic biphasic nanoparticles prepared by an electrified jetting process, in which two parallel streams of polymeric solutions are simultaneously introduced into the electrical field, resulting in nanoparticles with two distinct phases [1]. Unlike the conventional single phase particles, biphasic and anisotropic characteristics of these particles enable independent loading as well as surface modification of each phase. Consequently, the degrees of freedom and multi-functionality achievable with each nanoparticle are increased. More recently, we have extended this concept and reported the preparation and characterization of biphasic nanoparticles that are stable in aqueous environment, which are more relevant for biomedical applications [2]. In the study presented herein, model biphasic nanoparticles containing FITC- and biotin-conjugated dextrans in one phase and rhodamine-conjugated dextran in the other phase were further characterized especially with respect to their biocompatibility. In addition, their potential applicability as tools for targeted drug delivery or imaging, taking advantage of the multi-functionality, was assessed. To minimize complications with cellular uptake of these particles, human umbilical vein endothelial cells (HUVECs) were used to assess cellular response to the biphasic nanoparticles. Upon co-culture of HUVECs with varying doses of particles, there were no significant effects on cell viability as determined by trypan blue exclusion, for at least 48 hrs. The viability of cells not receiving any particles and those receiving up to 1 mg/ml particles were not statistically different, with more than 94% of the cells viable for all time points and doses. To evaluate the multi-functionality of anisotropic particles, specific ligand-mediated binding of particles to HUVECs was evaluated using confocal microscopy. Fixed and permeabilized HUVECs were stained with biotinylated CD29 followed by incubation with streptavidin to specifically immobilize streptavidin to HUVEC surfaces. Cells were then incubated with biphasic nanoparticles containing biotin only in one phase to demonstrate biotin-mediated orientation of the particles with respect to the cell surface. While some specific-orientation of biphasic nanoparticles to HUVEC surface was observed by confocal microscopy, some non-specific binding was also seen. This non-specific binding was quantified using flow cytometry, and was determined to be dose-dependent. With increasing doses of biphasic nanoparticles incubated with cells, there was a substantial increase in the fraction of cell population that was associated with the particles. At the highest concentration examined, 1 mg/ml, almost 100% of cells had attached particles. Taken together, these results suggest that the water-stable biphasic nanoparticles are a biocompatible approach for targeted delivery vehicle as well as for imaging when incorporated with trackers such as fluorescent dyes and magnetic particles.

1. Roh KH, Martin DC, Lahann J. Biphasic Janus particles with nanoscale anisotropy. Nat Mater 2005;4(10):759-63.

2. Roh KH, Martin DC, Lahann J. Triphasic Nanocolloids. J Am Chem Soc 2006;in press.