Biomedical Spectroscopy and Imaging

Here, we present a short overview of our implementation of label-free digital pathology by infrared (IR) imaging. We address the major issues to overcome for clinical translation. First, we elucidate that label-free IR imaging not only identifies cancer in tissue sections but also is even able to provide differential diagnostics as exemplified for colorectal and lung cancer. We obtained sensitivities and specificities far above 90% as compared to the gold standard histopathology. The information is obtained label-free, automated and observer independent. We showed that the spectral patterns observed in the infrared corresponds directly to protein alterations in tissue. This was achieved by integrating IR imaging with laser capture microdissection and subsequent proteome analysis. Furthermore, we demonstrated that IR imaging could replace immunohistochemical marker panels for differential diagnosis. Following one of the most important steps towards translation was the reduction of the measurement time, which now matches the time consumed for immediate diagnostics. Finally, we integrate deep neural networks for the automated annotation. All hurdles has been overcome and label-free digital pathology is ready to validate now the approach in clinically relevant unmet medical needs. This will facilitate acceptance of the approach by clinicians and pave the road for clinical translation.

MR Spectroscopy (MRS) has been used for diagnosis of many neurological disorders such as central nervous system tumors and neuro-inflammatory diseases. Despite many studies on MRS in neurodegenerative disorders and particularly Alzheimer’s disease, its utility has been hampered by lack of standard techniques across studies and limited data on the association between the level of metabolites in MRS and pathological changes of AD. In this review we have summarized the findings of MRS in Alzheimer’s disease, discussed the limitation of the current data and the pitfalls in interpretation of the MRS results and also we presented the latest developments in this field and potential future steps in order to utilize MRS more effectively in clinical practice.

Vibrational spectroscopic techniques have recently gained increasing clinical importance as non-invasive, rapid and inexpensive methods to obtain information on the content of biological samples. For some time Raman spectroscopy has been involved in preclinical applications, mainly in the cancer space, with evolving applications towards new horizons in the dermatology and companion diagnostics arena. It is attractive as an analytical technique due to its exquisite sensitivity, label-free operation and low water detectivity such that in-vivo applications are possible. In cytometry, Raman spectroscopy has been applied to the analysis of single cells providing a label-free alternative to cell classification approaches in the laboratory. In this review we collate in-vitro, ex-vivo and in-vivo examples of research using Raman spectroscopy for the detection, quantification and analysis of immune signaling at the cellular level. While cancer biology has recently focussed on the role of immunological signals in the development of the disease, it is timely to examine these applications as research in this space evolves.

In many scientific fields there is a high interest to study molecular adsorption processes on surfaces. The adsorbed molecule can have significant impact on the properties of the material under study, for example protein adsorption to inorganic material can enhance its biocompatibility. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy is a suitable method to monitor such adsorption processes close to a surface. In this study, ZnO films were synthesized on silicon ATR substrates via a mild hydrothermal reaction. The films were then characterized by scanning electron microscopy (SEM) and FTIR microscopy. Chemical imaging with FTIR microscopy allowed to analyze the composition of the heterogeneous film samples. ATR-FTIR spectroscopy was then applied to investigate the adsorption properties of the ZnO films. Protein solutions of bovine serum albumine (BSA) were circulated in a closed cycle over the ZnO film and IR spectra were recorded during the adsorption process. A stronger protein adsorption was observed for silicon substrates coated with ZnO than for plain silicon. Furthermore, subsequent flushing with pure water and desorption measurements indicated a stronger protein binding to ZnO than to plain silicon.

The function of membrane proteins is highly impacted by their membrane environment. One suitable approach to get insights into the interaction-induced dynamics of membrane proteins and lipid membranes is time-resolved infrared (IR) spectroscopy. Conclusions about environmental influences to the system can be drawn by correlating the observed kinetics to the well-characterized photocycles of light-driven transmembrane proton pumps like bacteriorhodopsin (BR). For the investigation of photoreceptor-membrane interactions, also minor changes in the absorption spectra must be resolved. Therefore, we applied IR laser spectroscopy using tunable quantum cascade lasers (QCLs) as IR light source. Several QCLs were implemented in a home-built spectrometer and provide a tunability in a broad spectral region covering protein, chromophore and lipid vibrational modes. Kinetics of the BR photocycle were monitored at single wavenumbers. This study demonstrates the high potential of QCL-based spectroscopy for the application to membrane protein studies.

The development of non-invasive blood glucose measuring devices continues to be developed. The photosensor is one of the instruments for detection the blood glucose, and the high performance of sensor is depending on the optical properties. Consequently, the observation about optical properties of Ba_0.2Sr_0.8TiO₃ (Barium Strontium Titanate) is important. In this paper, a solution of Ba_0.2Sr_0.8TiO₃ (Barium Strontium Titanate) with chlorophyll extract from spinach and papaya leaves has been deposited on the p-type Si (100) by spin coating technique. This research aims to find the effects of presence of chlorophyll in the Ba_0.2Sr_0.8TiO₃ films according to their optical properties and phonon mode. The film fabricated consisting of BST, BST with 2.5% spinach chlorophyll, BST with 5% spinach chlorophyll, BST with 2.5% papaya chlorophyll, and BST with 5% papaya chlorophyll. Therefore, the characterization was using UV-Vis spectrophotometer and micro Raman spectroscopy. The result showed that the addition of papaya chlorophyll have the optimal character than spinach chlorophyll. BST with papaya chlorophyll showed a significant decrease in the energy gap. Also, it has a phonon mode with a Raman shift that supports the result.

Cyanobacterial photosystem I (PSI) and photosystem II (PSII) complexes were assembled on a gold nanoparticle (GNP) to generate a biohybrid photocatalyst. Optical absorption and fluorescence measurements of the generated GNP conjugates showed signals from both PSI and PSII. Moreover, single-particle fluorescence analysis using a cryogenic microscopy provided definitive evidence that both PSI and PSII complexes are bound together to a single GNP. This PSI-GNP-PSII conjugate will be a useful platform for further development of a water-splitting nanodevice for hydrogen production using solar energy.