Rapid classification of proteins suspended in an evaporated sessile drop.

Reliable and accessible technologies for biological sample analysis are crucial for rapid, accurate illness diagnosis in resource-limited settings. Conventional methods like mass spectrometry and enzyme-linked immunosorbent assay (ELISA) often face challenges of technological complexity and equipment immobility, leading to delayed diagnoses and elevated costs. This study introduces evaporative deposition patterns from sessile droplets as a simple, cost-effective approach for classifying proteins in protein-salt mixtures, leveraging quantitative texture analysis to achieve high diagnostic accuracy. Using mixtures of potassium chloride (KCl) or sodium chloride (NaCl) with Bovine Serum Albumin (BSA) or Ovalbumin (OVA) as model systems, we varied salt (0.25-2 wt%) and protein (0.5-1.5 wt%) concentrations, observing distinct deposition morphologies such as coffee rings, cruciform/dendritic crystals at high salt levels, and volcano-shaped /spoke-like patterns at low or high protein levels. A novel quantitative framework integrating radial density distributions, gray-level co-occurrence matrix (GLCM) texture features, and receiver operating characteristic (ROC) curves achieved a 96.74 % classification accuracy for NaCl-protein mixtures, surpassing traditional texture analysis in simplicity and efficacy. These findings demonstrate the potential of evaporative deposition analysis as a simple tool for distinguishing molecular mixtures, laying the groundwork for future diagnostic applications. Unlike prior qualitative studies, this work provides a robust, quantitative method for protein classification, advancing the understanding of protein-salt interactions.