Tracking Nullomer Peptide Uptake in Cells Using Raman Microspectroscopy

Traditional methods of visualizing the uptake of peptide treatments in a cell usually includes labeling, which could alter a peptide’s chemical properties. This could affect a compound's functionality or make it bulkier, potentially altering their ability to enter a cell’s membrane. To address this, we explored Confocal Raman Microspectroscopy (CRM) to analyze subcellular features and track a compound of interest without additional sample-labeling. CRM is a method which combines Raman spectroscopy with a confocal microscope. To test whether CRM can be an effective method in tracking a specific compound in a cell, we imaged Neuroblastomas treated with 9S1R and 124R Nullomer peptides.Nullomer peptides are short amino acid sequences absent from the proteome of a species. Nullomer 9S1R is a 5-amino acid peptide prime sequence attached to a 5-arginine aa(amino acid). The Nullomer 124R(a control peptide) is also a 5-aa peptide sequence attached to a 5-arginine aa. Although both peptides share similar sequences, 9S1R (RRRRRWCMNW) includes cysteine and asparagine, while 124R (RRRRRWFMHW) contains phenylalanine and histidine. To analyze the two added Nullomers, we chose the amino acids with the most distinct Raman signals, cysteine and phenylalanine. Thereby we would enable label-free detection and intracellular location of Nullomers in our cells.