Assessing cellular metabolic dynamics with NAD(P)H fluorescence polarization imaging.

Altered metabolism enables adaptive advantages for cancer, driving the need for improved methods for non-invasive long-term monitoring of cellular metabolism from organelle to population level. Here we present two-photon steady-state fluorescence polarization ratiometric microscopy (FPRM), a label-free imaging method that uses nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) autofluorescence as a functional readout of cellular metabolism. The method is simple to implement and operates an order of magnitude faster than the NAD(P)H-fluorescence lifetime imaging microscopy (FLIM) imaging modality, reducing cytotoxic stress while providing long-term monitoring capacity. FPRM enables high-resolution dynamic tracking of NAD(P)H signals with subcellular details and we have established a set of instrument-independent ratiometric parameters that correlates NAD(P)H signals with metabolic status during pharmaceutical and environmental perturbations. We further integrated FPRM readouts with other parameters such as cell shape and migration on 2D and 3D collagen matrices, demonstrating the technique's versatility across bioengineered platforms for cancer metabolism research.