Femtogram Near-field Infrared Spectrometer for Biological Systems

Trustees Of Boston University, Boston

Investigators

Abstract

ABSTRACT 9987157 Shyamsunder Erramilli Boston University Femtogram Near-field Infrared Spectrometer for Biological Systems Biological molecules like proteins, nucleic acids, and lipids can be studied using infrared spectroscopy. The peaks in an infrared spectrum are caused by the chemical structure of the molecules themselves. The nature of the chemical groups in a molecule can often be recognized by its infrared spectrum. That spectrum can also serve as a fingerprint. Infrared microspectroscopy combines infrared spectroscopy with high-resolution imaging. Because the technique uses an intrinsic property of the molecules, it is possible to get contrast in images without using radioactive or fluorescent labels. One traditional shortcoming of infrared microscopy is that the spatial resolution is poor, due to the longer wavelengths involved (compared to visible light). The use of near-field techniques makes it possible to overcome the diffraction limit and permits the study of sub-micron size samples in water. With support from the National Science Foundation, a table-top imaging spectrometer capable of acquiring the infrared spectrum of an aqueous biological sample is being developed. The spectrometer will be built along the same general principles as an atomic force microscope. To this basic design a tunable infrared laser and infrared collecting optics will be added. The resulting microscope will be unique in that it allows for infrared imaging under water. Once it is complete, single living cells will be examined using infrared radiation. Development of the infrared spectrometer will provide a new window to study single living cells without requiring the use of either radioactive or fluorescent stains. Radioactive labeling is very sensitive, but the samples have to be handled and disposed of carefully, in order to avoid environmental problems. Many fluorescent labels are carcinogenic, and may perturb the cells that are being stained. In addition to allowing the imaging of single living cells, the near-field infrared spectrometer has the potential to identify the type of bacteria from its characteristic infrared signature. If this application is successful, the instrument would provide a convenient method to detect pathogenic bacteria.