Raman Tweezers Spectroscopy of Live, Single Red and White Blood Cells

Aseefhali Bankapur,Deepak Mathur,Elsa Zachariah,Santhosh Chidangil,Manna Valiathan,Jian R Lu

doi:10.1371/journal.pone.0010427

Abstract

An optical trap has been combined with a Raman spectrometer to make high-resolution measurements of Raman spectra of optically-immobilized, single, live red (RBC) and white blood cells (WBC) under physiological conditions. Tightly-focused, near infrared wavelength light (1064 nm) is utilized for trapping of single cells and 785 nm light is used for Raman excitation at low levels of incident power (few mW). Raman spectra of RBC recorded using this high-sensitivity, dual-wavelength apparatus has enabled identification of several additional lines; the hitherto-unreported lines originate purely from hemoglobin molecules. Raman spectra of single granulocytes and lymphocytes are interpreted on the basis of standard protein and nucleic acid vibrational spectroscopy data. The richness of the measured spectrum illustrates that Raman studies of live cells in suspension are more informative than conventional micro-Raman studies where the cells are chemically bound to a glass cover slip.

Highlights

Optical tweezers are proving to be of widespread utility in contemporary research in a number of fields, in the biomedical sciences [1,2]
In order to facilitate spectroscopic studies of single living cells in a physiological medium, we have developed a high-resolution, dual-wavelength apparatus that combines optical trapping with Raman spectroscopy, utilizing near infrared wavelength light at 1064 nm for trapping and 785 nm light for Raman excitation at very low levels of incident power (,10 mW)
We describe in the following details of a successful coupling in our laboratory of a Raman spectrometer with an optical trap that allows, without physical contact, simultaneous optical trapping, optical manipulation, and recording of Raman spectra of micronsized objects floating in a medium

Summary

Introduction

Optical tweezers are proving to be of widespread utility in contemporary research in a number of fields, in the biomedical sciences [1,2]. In order to facilitate spectroscopic studies of single living cells in a physiological medium, we have developed a high-resolution, dual-wavelength apparatus that combines optical trapping with Raman spectroscopy, utilizing near infrared wavelength light at 1064 nm for trapping and 785 nm light for Raman excitation at very low levels of incident power (,10 mW). We have utilized this apparatus to probe, in sensitive and high-resolution fashion, Raman features in red and white blood cells

Methods

Results

Conclusion