Label-Free Morpho-Molecular Imaging for Studying the Differential Interaction of Black Phosphorus with Tumor Cells

Black phosphorus nanosheets (2D BP) are emerging as very promising, highly selectivechemotherapeutic agents due to their fast degradation in the intracellular matrix of cancer cells.Here, optical diffraction tomography (ODT) and Raman spectroscopy were exploited as a powerfullabel-free approach to achieve integrated insights into the processes accompanying the administrationof exfoliated 2D BP flakes in human prostatic adenocarcinoma and normal human prostate epithelialcells. Our ODT experiments provided unambiguous visualization of the 2D BP internalizationin cancer cells and the morphological modifications of those cells in the apoptotic phase. Thecellular internalization and damaging occurred, respectively, 18 h and 36-48 h after the 2D BPadministration. Changes in the chemical properties of the internalized 2D BP flakes were monitoredby Raman spectroscopy. Interestingly, a fast oxidation process of the 2D BP flakes was activated in theintracellular matrix of the cancer cells after 24 h of incubation. This was in sharp contrast to the low 2DBP uptake and minimal chemical changes observed in the normal cells. Along with the understandingof the 2D BP fate in the cancer cells, the proposed label-free morpho-molecular approach offersa powerful, rapid tool to study the pharmacokinetic properties of engineered nanomaterials inpreclinical research