Distinction of tumor-derived vesicles from normal vesicles by Raman microspectroscopy

Type:
Oral presentation
Authors:
E. van der Pol, F.A.W. Coumans, C.M. Hau, C. Otto, A.T.M. Lenferink, A. Sturk, R. Nieuwland, T.G. van Leeuwen
Location: 
SPIE Photonics West 2014, San Francisco, United States
Date:
February 1, 2014

Summary

Cell-derived vesicles have a diameter of 30 nm to 1 μm and are abundantly present in human blood. The origin and composition of these vesicles is disease (state) dependent and therefore vesicles are a potential biomarker for disease. The cellular origin of vesicles is usually established by fluorescent antibody labeling, which involves practical problems. We have applied Raman microspectroscopy to distinguish tumor-derived vesicles from normal vesicles in solution without labeling. Single optically trapped tumor-derived vesicles showed unique Raman transitions compared to normal vesicles. For the first time, single tumor-derived vesicles were distinguished from normal vesicles without labeling using Raman microspectroscopy.

Abstract

Background: Cells release vesicles, also called exosomes or microparticles, which are spherical particles containing a phospholipid bilayer. These vesicles are abundantly present in human blood and it is becoming increasingly clear that they contribute to many homeostatic processes, for example coagulation and intercellular signaling. Therefore, vesicles are a potential biomarker for disease. However, due to their small size (30 nm – 1 μm), vesicle detection is a major challenge. The cellular origin of vesicles is usually established by fluorescent antibody labeling, which is laborious and involves practical problems. We have applied Raman microspectroscopy to distinguish tumor-derived vesicles from normal vesicles in solution without labeling.

Methods: Tumor-derived vesicles were isolated from a human pancreatic adenocarcinoma cell line and platelet and erythrocyte vesicles were isolated from blood bank concentrates. Vesicles were isolated using differential centrifugation and analyzed by transmission electron microscopy, nanoparticle tracking analysis, and Raman microspectroscopy. For Raman microspectroscopy, a 100 mW krypton ion laser operating at a wavelength of 647 nm was focused to a probe volume of 1 fL, which overlaps with the dimension of vesicles. The Stokes shift from light scattered by optically trapped vesicles was measured using a spectrograph dispersing in the range 646–849 nm.

Results: The Raman spectra of single optically trapped vesicles showed spectral transitions characteristic of phospholipids. Moreover, single optically trapped tumor-derived vesicles showed unique Raman transitions compared to platelet and erythrocyte vesicles.

Conclusions: For the first time, single tumor-derived vesicles were distinguished from normal vesicles without fluorescent antibody labeling using Raman microspectroscopy.

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