Investigation of Mechanical and Viscoelastic Properties of Macrophage Membrane-Cytoskeleton Induced by Gold Nanorods in Leishmania Infection

Cell membranes and cytoskeleton play a crucial role in regulating cellular responses by mediating mechanical forces and physical stimuli from the microenvironment through their viscoelastic properties. Investigating these properties provides valuable insights into disease mechanisms and therapeutic strategies. Gold nanorods (GNRs), especially under irradiation, exhibit lethal effects against Leishmania parasites through plasmonic photothermal conversion. However, their mechanical interaction with cells remains poorly understood. Here, Defocusing Microscopy (DM), a quantitative phase microscopy technique, was employed to analyze membrane fluctuations in macrophages (M∅s) exposed to GNRs and infected with Leishmania amazonensis. Measuring the membrane-cytoskeleton fluctuation of defocused images, we quantified viscoelastic parameters such as bending modulus (kc) and viscosity (η), enabling a detailed char-acterization of membrane behavior. Results indicate that infection increases both kc and η, while IC50 treatment reduces infection and selectively increases kc without affecting viscosity. In healthy macrophages, GNRs reduced both parameters, suggesting a fluidizing effect. These findings contribute to a deeper understanding of GNRs' therapeutic performance and cytotoxicity, contributing to improved phototherapy applications.