Page 285 - Vibrational Spectroscopic Imaging for Biomedical Applications

260 Cha pte r Ei g h t

conditions. Nonlinear enhancement effects such as CARS and stimu-
70
lated Raman scattering microscopy will improve the sensitivity
which is the key to collect Raman images at real-time video-time
frame rates. These techniques will not only provide label-free chemi-
cal contrast in biomedical imaging of tissue, but also of single cells.
The diffraction limit of light can be overcome by coupling Raman
spectroscopy with near-field microscopy. The most promising tech-
nique is TERS which combines signal enhancements in the close
vicinity of metal nanoparticles and AFM tips for excitation and far-
field microscopy for effective detection.
A major obstacle for the broader dissemination of Raman-based
methods in the medical field is their technical complexity. Therefore,
user-friendly Raman instruments are another important requirement.
Besides the Raman systems for the detection and classification of
microorganisms (see section “Excitation in the Visible Wavelength
Range”), other Raman systems have been introduced for skin stud-
ies, e.g., to detect carotenoid levels (Pharmanex, United States) or to
record depth concentration profiles (River Diagnostics, The Nether-
lands). Although in its early stages, these developments clearly
demonstrate that Raman spectroscopy has the potential to be fully
accepted as a complementary diagnostic tool for rapid and nondestruc-
tive in vitro, ex vivo, and in vivo analyses of tissues, cells and bacteria.

Acknowledgments
Financial support of the European Union via the Europäischer Fonds
für Regionale Entwicklung (EFRE) and the “Thüringer Kultusminis-
terium (TKM)” (project: B714-07037) is highly acknowledged.

References
1. S. W. Hell, “Microscopy and Its Focal Switch,” Nature Methods, 6:24–32, 2009.
2. C. Krafft and V. Sergo, “Biomedical Applications of Raman and Infrared
Spectroscopy to Diagnose Tissues,” Spectroscopy, 20:195–218, 2006.
3. D. I. Ellis and R. Goodacre, “Metabolic Fingerprinting in Disease Diagnosis:
Biomedical Applications of Infrared and Raman Spectroscopy,” Analyst,
131:875–885, 2006.
4. C. Krafft, G. Steiner, C. Beleites, and R. Salzer, “Disease Recognition by Infrared
and Raman Spectroscopy,” Journal of Biophotonics, 2:13–28, 2008.
5. I. Notingher and L. L. Hench, “Raman Microspectroscopy: A Noninvasive Tool
for Studies of Individual Living Cells In Vitro,” Expert Review of Medical Devices,
3:215–234, 2006.
6. R. J. Swain and M. M. Stevens, “Raman Microspectroscopy for Non-Invasive
Biochemical Analysis of Single Cells,” Biochemical Society Transactions,
35:544–549, 2007.
7. C. Krafft, B. Dietzek, and J. Popp, “Raman and CARS Spectroscopy of Cells
and Tissues,” Analyst, 134:1046–1052, 2009.
8. C. Krafft, M. Kirsch, C. Beleites, G. Schackert, and R. Salzer, “Methodology
for Fiber-Optic Raman Mapping and FT-IR Imaging of Metastases in Mouse
Brains,” Analytical and Bioanalytical Chemistry, 389:1133–1142, 2007.