Intracellular and Extracellular Platinum Quantification at Single-Cell Scale with LA-ICP-TOFMS.

Understanding the localized fate of metal-based therapeutics is critical for optimizing anticancer efficacy and mitigating systemic toxicities, including nephrotoxicity, neurotoxicity, and ototoxicity. While platinum-based drugs are known to interact with both healthy and tumor cells as well as the extracellular matrix (ECM), conventional methods often lack the spatial resolution required to distinguish between these compartments. Here, we present an analytical framework integrating immunohistochemistry (IHC) with high-resolution laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). While preserving spatial architecture, this approach enabled the partitioning of intracellular and extracellular platinum fractions in a three-dimensional multicellular tumor spheroid model (MDA-MB-468), revealing that 23% of the total platinum mass remained associated with the added collagen matrix. The robustness of this framework was further validated in murine spleen and kidney tissues. By applying area-based normalization to account for varying cell densities, we successfully differentiated distribution trends within complex regions, such as the splenic red and white pulp. This strategy provides a quantitative tool for assessing drug penetration and compartmentalized biodistribution in complex biological matrices.