Dual-mode microfluidic RELS-QCM platform for label-free profiling of mitochondrial preparations from a graded stress...

Rapid comparison of fragile isolated organelles requires consistent sample handling and concentration normalization. We present a polycarbonate microfluidic platform that sequentially combines resonance elastic light scattering (RELS) and quartz crystal microbalance (QCM) sensing of the same unstained mitochondrial suspension. Mitochondria were isolated from neuron-like SH-SY5Y cultures exposed to 100-500 μM 1-methyl-4-phenylpyridinium (MPP+) for 24 h and adjusted to defined protein concentrations. The upstream optical module records the 532-nm elastic scattering line at 90°, whereas a downstream cysteamine-modified gold electrode records surface-coupled acoustic loading. Across 0.010-0.050 mg/mL mitochondrial protein, RELS signals were linear and the fitted slope increased with MPP+ exposure. QCM responses depended on both protein loading and treatment, with the clearest plateau separation at 0.050 mg/mL. Cellular assays independently confirmed increased oxidant-sensitive fluorescence, reduced metabolic activity and mitochondrial depolarization. Same-sample QCM comparisons gave a 2% response difference after regeneration of the same crystal and 3.64% across three independently fabricated chips, each tested with five to six crystals. The optical and acoustic outputs are empirical physical descriptors of the recovered preparations, not direct measurements of mitochondrial size, morphology or dry mass. Their agreement does not establish a specific remodeling mechanism or exclude shared preparation-related confounders. The demonstrated capability is a paired, protein-normalized comparison within a controlled injury model; structural specificity and suitability for compound screening remain to be established.