(678a) Engineering the Surfaces of Fluorescently-Labeled Polymeric Nanoparticles for 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. 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 semiconductors, LEDs and solar cells.^1,2 However, its high quantum yield and photostability make it a promising candidate as a fluorescent imaging agent for biomedical applications.

Using the Flash Nanoprecipitation process³, different loadings of this fluorophore and a filler homopolymer of poly(D,L-lactic acid) (PDLLA) have been incorporated into amphiphilic diblock copolymer nanoparticles of poly(ethylene oxide)-b-poly(D,L-lactic acid) (PEO-PDLLA). We investigated 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.

The PEO-PDLLA nanoparticles made with varying amounts of fluorophore and homopolymer resulted in particles with sizes ranging from 60-200 nm. The zeta potentials were typically ~-15 to -20 mV. Previous work done by Pansare et al. analyzed a synthesized pentacene derivative Et-TP5 showing promising optical properties.⁴ Recent work from our group showed TIPS pentacene loaded nanoparticles readily taken up by macrophages and the TIPS pentacene visible through imaging cytometry even at weight percent loadings in particles as low as 1 wt%.⁵ The presentation will delve into the nanoparticle fabrication and engineering of these particles, looking at the fluorescence and quenching properties of the loaded TIPS pentacene. Initial studies showed that even at TIPS pentacene loadings of 1 wt%, self-quenching due to Forster Resonance Energy Transfer (FRET) may be present. Through similar analysis to that of Pansare et al., the work presented shows that the TIPS pentacene may be a comparable fluorophore appropriate for these applications but with the advantage that it is commercially available.

This research also tests the hypothesis that the surface chemistry of the particles can easily be altered by the addition of acid end capped PDLLA homopolymer to increase carboxylate groups on the surface while also changing the size properties. The carboxylate groups provide a useful functional group for coupling streptavidin to the surface. Streptavidin is a glycoprotein from the bacteria Streptomyces avidinii and with biotin, form on of the strongest non-covalent interactions with a dissociation constant of K_D ≈ 10^-15 M. By coating the nanoparticles with streptavidin, it provides a facile method for functionalizing the surface with biotinylated ligands for targeted drug delivery.

Flash nanoprecipitation shows promise in its scalability and efficacy in producing well-defined nanoparticles and this talk explores a potential design and processing framework of engineering polymeric nanoparticles appropriate for biological studies in a variety of different applications within the drug delivery field.

References

1. Anthony, J. E., Silylethyne-Substituted Pentacenes. Material Matters: Organic and Molecular Electronics 2009, 4 (3), 58-60.
2. Platt, A. D.; Day, J.; Subramanian, S.; Anthony, J. E.; Ostroverkhova, O., Optical, Fluorescent, and (Photo)conductive Properties of High-Performance Functionalized Pentacene and Anthradithiophene Derivatives. Journal of Physical Chemistry C 2009, 113 (31), 14006-14014.
3. 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.
4. Pansare, V. J.; Bruzek, M. J.; Adamson, D. H.; Anthony, J.; Prud'homme, R. K., Composite Fluorescent Nanoparticles for Biomedical Imaging. Mol. Imaging. Biol. 2014, 16 (2), 180-188.
5. McDaniel, D. K.; Jo, A.; Ringel-Scaia, V. M.; Coutermarsh-Ott, S.; Rothschild, D. E.; Powell, M. D.; Zhang, R.; Long, T. E.; Oestreich, K. J.; Riffle, J. S.; Davis, R. M.; Allen, I. C., TIPS pentacene loaded PEO-PDLLA core-shell nanoparticles have similar cellular uptake dynamics in M1 and M2 macrophages and in corresponding in vivo microenvironments. Nanomedicine: Nanotechnology, Biology and Medicine 2017, 13 (3), 1255-1266.