DIY micro-Raman: Flexible and cheap

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  • Published: Jul 6, 2016
  • Author: David Bradley
  • Channels: Raman
thumbnail image: DIY micro-Raman: Flexible and cheap

Micro power

Concentration maps of the end-members in cells of Jurkat and MIA PaCa-2 cell lines. Credit: Image courtesy of IOS Press

Researchers have demonstrated how to build an inexpensive and flexible micro-Raman system at a fraction of the cost and with greater capability than was previously possible. Details are discussed in the journal Biomedical Spectroscopy and Imaging.

As we know, Raman spectroscopy can provide detailed chemical information about a sample and is even more powerful when combined with microscopy techniques, when it can non-destructively analyse biological samples, for instance. There are several commercial, research-grade Raman microscopes available but they can be costly and less flexible than some experimenters would wish for. Now, a team has used twenty readily available components - mirrors and filters, lenses, cameras, and a motorized table - to assemble a versatile micro-Raman system at a fraction of the cost of a commercial instrument; the team suggests a price of 10,000 euros for the components, then add on the cost of laser, spectrograph and CCD detector, Christophr Krafft of the University Jena, Germany, told SpectroscopyNOW. "Custom built solutions are feasible for the latter components, but low-cost commercial equipment might be also appropriate for most applications," he adds.

Collection point

Because micro-Raman spectroscopy combines chemical characterization with imaging in what is a label-free manner, it is particularly well suited to biological and biomedical research as it can be used to detect changes in composition and find correlations with biological changes due to metabolism or pathology without interfering with the sample. The same technique also holds promise for rapid clinical diagnostics in living cells and various other applications, such as observation of cell metabolism, growth, and ageing. It might also be used in investigations of how drug resistance arises, drug uptake and transport, chemical mapping of cells, and others areas. Most disease processes begin at the cellular level so this technique is perfectly suited for such research.

The team points out that the system can be flipped between an upright and inverted configuration for different experiments. It is, they suggest, particularly effective for hyperspectral imaging experiments wherein the chemical composition related to each pixel in a scanned image can be obtained. In addition to Raman spectroscopy, the system can be combined with other modalities such as fluorescence imaging. In a proof of principle, the team has collected Raman maps of individual cells from two different cancer cell lines, MIA PaCs-2 pancreatic cancer and Jurkat, T-lymphocytes. By collecting the spectra at each point, they were able to map the relative concentrations of lipids versus proteins/DNA. "Fibre coupling enables [us] to connect various lasers for excitation and spectrometer/CCD combinations for signal detection," the team says, "The performance of the instrument is demonstrated via Raman spectroscopy at 785 nm excitation wavelength."

Biomedical

"We acquired Raman images of single human cells with a custom instrument. These data demonstrated that the instrument provides spectra of sufficient quality to distinguish the cell type. This result will be exploited in projects about identification of tumour cells circulating in blood," says Krafft.

Krafft worked with Jürgen Popp, Roman Kiselev and Iwan Schie, from the Leibniz Institute, and Sonja Aškrabić of the University of Belgrade, Serbia. Popp and Krafft hope that other researchers will be able to build on their blueprint and construct similar inexpensive tools for their own research. The work could lead to rapid growth in Raman micro-spectroscopic imaging of biological samples including cancer tissues. The team adds that, "Since the major part of the system consists of separate general purpose optomechanical components, it can be rebuilt, modified or extended. For example, a combination with fluorescence imaging requires an additional light source, a set of optical filters and a suitable camera for detection."

"This microscope is intended for integration in a device to identify and characterize circulating tumor cells in blood," Krafft told us. "Lab work demonstrated accurate classification of cultured cells. A prototype will be installed at clinical partners to collect first data in a dedicated cartridge from preprocessed patient blood samples."

Related Links

Biomed Spectrosc Imaging 2016, online: "Design and first applications of a flexible Raman micro-spectroscopic system for biological imaging"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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