Alkyne-tagged PLGA allows direct visualisation of nanoparticles in vitro and ex vivo by stimulated Raman scattering microscopy

Polymeric nanoparticles (NPs) are attractive candidates for the controlled and targeted delivery of therapeutics in vitro and in vivo. However, detailed understanding of the uptake, location and ultimate cellular fate of the NPs is necessary in order to satisfy safety concerns, which is difficult because of the nanoscale size of these carriers. In this work, we show how small chemical labels can be appended to poly(lactic acid-co-glycolic acid) (PLGA) in order to synthesise NPs that can then be imaged by stimulated Raman scattering (SRS) microscopy, a vibrational imaging technique which can elucidate bond specific information in biological environments, such as the identification of alkyne signatures in modified PLGA terpolymers. We show that both deuterium and alkyne labelled NPs can be imaged within primary rat microglia, and the alkyne NPs can also be imaged ex vivo cortical mouse brain tissue. Immunohistochemical analysis confirms that the NPs localize in microglia in the mouse brain tissue, demonstrating that these NPs have the potential to deliver therapeutics selectively to microglia.