Rapid estimation of the β-sheet content of Human Serum Albumin from the drying patterns of HSA-nanoparticle droplets

The formation of specific patterns during evaporation of biofluids e.g. blood, serum etc. can be analyzed for quick identification of several diseases. Human Serum Albumin (HSA) is frequently used as the model protein to study amyloid fibril formation that is responsible for numerous neurodegenerative diseases like Parkinson’s disease, Alzheimer’s disease etc. In the present study the fibril growth of HSA is characterized by analyzing the drying patterns of the protein solution. The fibril formation of HSA is confirmed by spectrofluorimetry and the β-sheet content is quantified by far-UV Circular Dichroism spectrometry. Examinations of the drying patterns of HSA, in presence of fluorescent nanoparticles, reveals distinctive pattern transformations with increase in the β-sheet content visualized through fluorescence microscopy and FESEM. The fluorescence images of the dried droplet are analyzed using image processing by the color thresholding method. A rapid quantification methodology of the β-sheet content of HSA and the fraction of unfolded protein has been developed by comparing the results of the image analysis with those of the far-UV CD data.