High-Resolution Label-Free Detection of Biocompatible Polymeric Nanoparticles in Cells

The design of efficient drug nanocarriers necessitates a deep understanding of their interaction with targeted cells. Polymeric poly(lactic acid) (PLA) or poly(d,l-lactic-co-glycolic acid) nanoparticles (NPs) with sizes lower than 200 nm are among the most employed nanocarriers in drug delivery. Their detection inside cells requires appropriate labeling for high-resolution imaging techniques, which unfortunately often alter their physicochemical properties and biological fate. Moreover, nowadays no high-resolution method allows precise detection simultaneously to the identification of NPs chemical composition in cells, which is of outmost interest to gain insights on their fate. Here, this challenge is addressed by using an innovative atomic force microscope coupled with a tunable infrared laser source (nanoIR). NanoIR is used to unambiguously identify PLA NPs of around 170 nm with high resolution. A reliable, nondestructive, and direct method able to precisely locate and chemically characterize PLA NPs within a cell without the need of labeling is presented.