Thermal ‘Fingerprinting’ of Cells Using FTIR

Abstract

Every cell is composed of a combination of proteins and lipids that define the cell. The biomolecular composition of a cell can yield a unique IR spectral profile, termed chemical “fingerprint”, in the FTIR. Even though it provides overall information on the state and composition, the challenge is in obtaining a more sensitive and mechanistically relevant “fingerprint” of a cell particularly in the protein regime where numerous detection assays are now based [1]. Heat induced denaturation of proteins in a cell, which can be termed as thermal “fingerprint”, offers detailed and mechanistically relevant information for identification and characterization of different cells. For this study, the chemical and the thermal “fingerprint” of four different cell types are characterized and compared — human dermal fibroblasts (HDFs), LNCaP prostate tumor cells, smooth muscle cells (SMCs) and microvascular endothelial cells (MVECs). Multiple protein denaturation peaks were observed during heating from room temperature to 90°C at 1°C/min that are cell specific. A correlation coefficient (r) was used to compare responses between the cell types (higher ‘r’ implies closer resemblance). For the chemical “fingerprint”, r values of cells compared to HDFs are 0.97 for MVECs, 0.91 for LNCaPs and 0.70 for SMCs. Similarly, for the thermal “fingerprint”, r values of cells compared to HDFs are 0.86 for MVECs, 0.73 for LNCaPs and 0.54 for SMCs. The deviation of ‘r’ values from 1.00 is wider in the case of the thermal “fingerprint” than the chemical “fingerprint”. This result demonstrates that thermal “fingerprinting”, based on protein denaturation, offers a mechanistic basis for enhanced differentiation between cells as compared to chemical “fingerprinting”. Extensive applications ranging from rapid disease diagnostics, forensics, cell culture quality control, cell sorting techniques etc. may benefit from this approach.