(203c) Fabrication and Characterization of Fluorescently Labeled Polymeric Nanoparticles for Biodistribution Studies of Drug Delivery

The use of nanoparticles in drug delivery can address many of the difficulties faced by traditional methods such as systemic toxicity, transport limitations, and drug solubility. By loading drugs into biocompatible polymeric nanoparticles, drugs that were previously unusable due to their solubility or toxicity can now be used, and by fluorescently labeling the nanoparticles with a small molecule like 6,13-Bis(triisopropylsilylethynyl)pentacene (TIPS pentacene), the particles can be tracked for biodistribution studies in biological systems. TIPS pentacene is a fluorophore that has been primarily used in the optoelectronic device field. However, its high quantum yield and photostability make it a promising candidate as a fluorescent imaging agent for biomedical applications.

Using the Flash Nanoprecipitation process¹, different loadings of this fluorophore as well as a filler homopolymer of poly(L-lactic acid) (PLLA) have been incorporated into amphiphilic diblock copolymer nanoparticles of poly(ethylene oxide)-b-poly(D,L-lactic acid) (PEO-PDLLA). The effects of varying the TIPS pentacene loading as well as the homopolymer to diblock copolymer weight:weight ratio on the characteristics of the resulting nanoparticles such as size, zeta potential, and fluorescent intensity have been studied.

Nanoparticles were fabricated with hydrodynamic diameters in the range of 80-120 nm and polydispersity indices less than 0.3 as measured by dynamic light scattering. The zeta potentials of the particles were typically around -15 mV in phosphate buffered saline diluted 100X. Fluorescence studies show that the nanoparticles containing TIPS pentacene could be excited at wavelengths of 600 nm and below and had a principal emission peak at 650 nm. These nanoparticles were colloidally stable in cell-growth media supplemented with fetal bovine serum (FBS) for periods up to 12 hours. Cell culture studies with macrophage cells show that they were neither immunogenic nor cytotoxic. ELISA tests showed that the nanoparticles induced levels of the inflammatory cytokines interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFa) in both M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophage cells similar to those of mock negative control experiments. Further results will be presented on how these nanoparticles are internalized by macrophages.

1. Gindy, M. E.; Panagiotopoulos, A. Z.; Prud'homme, R. K., Composite block copolymer stabilized nanoparticles: Simultaneous encapsulation of organic actives and inorganic nanostructures. Langmuir 2008, 24 (1), 83-90.