Infrared Imaging and Mapping for Biosensors
Lateral resolution. When brilliant light sources like lasers or synchrotron radiation are used, the lateral resolution typically is diffraction limited in the range of a few micrometers for IR microscopy [2, 11]. This can be improved by orders of magnitude with near-field IR microscopy , which enables resolution down to a few tens of nanometers, and spectroscopic studies by tuning of lasers  or use of a broadband synchrotron or laser source. IRSE biochip characterization with lateral resolution down to approximately 200 × 400 μm is possible.
Sensitivity. For SNIM, RAIRS, ATR, and IRSE, the high sensitivity allows detection of nanometer thick biomolecular films.
Quantification of experimental results. Reliable quantification of optical spectra and signals can be performed by optical modeling of RAIRS, ATR, and IRSE spectra. Here, IRSE has some advantages because it delivers up to three method-independent parameters (phase shift and amplitude ratio of s- and p-polarized reflection coefficients and the polarization degree). For SNIM quantitative evaluation is more complex than for the other methods and is dependent on the geometry of the SNIM experiment.
Key Research Findings
Sensors in Biochemistry and Biomedical Applications
Infrared imaging and mapping can be used for design of new functional sensing templates based on smart thin films and surfaces. Label-free observation of vibrational bands allows specific identification of molecular bonds, molecular groups, and materials. The interpretation of IR signals enables the analysis of the binding chemistry, structure, and molecular interactions and can give quantitative conclusions on the amount of adsorbed material. In situ characterization might be used for monitoring of chemical changes as well as molecule adsorption in dependence of growth conditions and external stimuli.
Sensors in Microfluidic Devices
In combination with reversible and smart templates, analysis of liquids in a flow cell can be performed.
Sensors in Combination with SEIRA
Specific substrates like, e.g., metallic island films or metallic wires, may show a SEIRA effect. In combination with a device, this effect can enhance the detection sensitivity.
With the development of infrared lasers (e.g., quantum cascade lasers) having spectral tunability or are available as broadband source in the MIR spectral range, the implementation of such lasers in infrared measurement technology is increasing. Due to possible higher lateral resolution and faster measurement protocols, such techniques are expected to be especially valuable for new sensing systems which include functional surfaces and thin films sensitive on external stimuli (pH, temperature, electric field, light, etc.). Such smart interfaces can be combined with techniques either sensing or releasing specific analytes. Using in situ IR spectroscopy studies in liquid environment is feasible, providing a high potential for bioanalytical and biomedical applications.
- 1.Eggins BR (2002) Chemical sensors and biosensors. Wiley, ChichesterGoogle Scholar
- 4.Clayborn M, Umemura J, Merklin GT, Kattner J, Hoffmann H, Mendelsohn R, Flach CR, Frey BL, Corn RM, Weibel SC, Röseler A, Korte E-H (2002) Mid-infrared external reflection spectroscopy. In: Griffiths PR, Chalmers J (eds) Handbook of vibrational spectroscopy, vol 2. Wiley, Chichester, pp 969–1090Google Scholar
- 6.Mirabella FM, Fitzpatrick J, Reffner JA, Chabal YJ (2002) Mid-infrared internal reflection spectroscopy. In: Griffiths PR, Chalmers J (eds) Handbook of vibrational spectroscopy, vol 2. Wiley, Chichester, pp 1091–1123Google Scholar
- 8.Kidder LH, Haka AS, Lewies EN (2002) Instrumentation of FT-IR imaging. In: Griffiths PR, Chalmers J (eds) Handbook of vibrational spectroscopy, vol 2. Wiley, Chichester, pp 1386–1404Google Scholar
- 9.Attas M (2002) Functional infrared imaging for biomedical applications. In: Griffiths PR, Chalmers J (eds) Handbook of vibrational spectroscopy, vol V. Wiley, Chichester, pp 3388–3398Google Scholar
- 10.Fabian H, Mäntele W (2002) Infrared spectroscopy of proteins. In: Griffiths PR, Chalmers J (eds) Handbook of vibrational spectroscopy, vol V. Wiley, Chichester, pp 3399–3425Google Scholar
- 12.Raschke MB, Molina L, Elsaesser T, Kim DH, Knoll W, Hinrichs K (2005) Aperture less near-field vibrational imaging of block-copolymer nanostructures with ultra high spectral resolution. Chem Phys Chem 6:2197–2203Google Scholar
- 14.Zhang X, Tretjakov A, Hovestaedt M, Sun G, Syritski V, Reut J, Volkmer R, Hinrichs K, Rappich J (2012) Electrochemical functionalization of gold and silicon surfaces by maleimide-group towards biosensor for immunological application. Acta Biomater 9(2013):5838–5844Google Scholar
- 15.Hinrichs K, Eichhorn K-J (eds) (2014) Ellipsometry of functional organic surfaces and films. Springer, HeidelbergGoogle Scholar