Multianalytical approach for surface- and tip-enhanced infrared spectroscopy study of a molecule-metal conjugate: deducing its adsorption geometry.

This study presents a multianalytical approach for surface-enhanced infrared absorption spectroscopy (SEIRA) and tip-enhanced infrared nanospectroscopy (TEIRA) studies of the α-methyl-dl-tryptophan adsorption geometry on a gold nanoparticle surface. Comparison of SEIRA spectra obtained in the transmission, attenuated total reflection and reflection modes verified the reproducibility of the adsorption. The application of the AutoSeagull (Harrick Scientific) accessory enabled us to track the dependence of the incident angle on the relative band intensity in the same area of the sample. Furthermore, the effect of two polarization modulations (p and s) in TEIRA was examined to deduce the adsorption geometry and to better understand the molecule/metal interaction. The nanogap between a gold-coated atomic force microscopy (AFM) tip and the gold surface induced electromagnetic enhancement in the optical field intensity. This is associated with the additional near-field electromagnetic field trapping effect. The local field intensity reinforcement significantly increased the infrared absorption cross-section of the compound under the tip with simultaneous improvement in spatial resolution. The originality of this study lies in the combination of various measurement modes and incident angles in SEIRA and two orthogonal polarizations in TEIRA to provide comprehensive characterization of the adsorption phenomenon. The results give important insights into tracking subtle changes in molecule geometry upon adsorption.

Vibrational microspectroscopy analysis of human lenses.

In this study we present vibrational analysis of healthy (non-affected by cataract) and cataractous human lenses by means of Raman and FTIR spectroscopy methods. The performed analysis provides complex information about the secondary structure of the proteins and conformational changes of the amino acid residues due to the formation of opacification of human lens. Briefly, the changes in the conformation of the Tyr and Trp residues and the protein secondary structure between the healthy and cataractous samples, were recognized. Moreover, the observed spectral pattern suggests that the process of cataract development does not occur uniformly over the entire volume of the lens.

Differentiation of protein secondary structure in clear and opaque human lenses: AFM - IR studies.

Here, we present the first approach to human lenses investigations with and without cataract development changes in nanoscale resolution using AFM - IR spectroscopy. We proved that the application of this technique allowed us to better understand of structural changes connected with advancing disease process in studied lenses. The obtained results show the impact of the disease development on the secondary structure of proteins in these human tissues. The domination of the ß-turn protein secondary structure is observed in the clear (non-affected by cataract) lens. While, in the case of the opaque (cataractous) samples the different degree of the degradation due to development of cataract, was recognized. Briefly, this process is associated with the protein secondary changes from ß-turn/ß-sheet parallel for less altered part of the lens to stable anti-parallel ß-sheet for the more degraded part. Interestingly, the AFM - IR technique provided estimation of the protein secondary structure without the need for using deconvolution procedure.

FT-IR study of montmorillonite-chitosan nanocomposite materials.

Bone defect is one of the most frequent problems in bone tissue reconstruction in which application of a biomaterial filling is necessary. It creates a still rising demand of biomaterials for bone surgery. Polymer-ceramic nanocomposites (e.g. based on chitosan matrix) is a group of novel materials whose properties such as strength, Young's modulus, bioactivity and controlled degradation time make them suitable materials for filling bone defects. Investigations of nanocomposite foils which consisted of biopolymer-chitosan (CS) matrix and montmorillonite (MMT) as a nano-filler was the subject of the work. The nanocomposite materials were produced by a two-step dispersion of the nanoparticles in the biopolymer matrix. The first stage involved mechanical stirring and the second one - ultrasonic agitation. Mechanical tests were performed on the nanocomposites and their Young's modulus was estimated. Significant improvement of mechanical properties of the nanocomposites in comparison with the pure polymer (CS) was observed. The nanocomposite foils (CS/MMT) were subjected to FT-IR spectroscopy investigations whose objective was to explain the reason of the change in mechanical characteristics of the nanocomposites. Transmission and ATR techniques operating in MIR range were used to study the nanocomposites. The FT-IR techniques were used to determine interactions at nanoparticle-biopolymer matrix interface. A pure unmodified CS foil was used as a reference material for FT-IR studies. It was proven that application of FT-IR techniques allows not only to identify phases, but also to explain structural changes in the systems studied.

FT-Raman, FT-IR spectroscopy and PIXE analysis applied to gallstones specimens.

Fourier transform Raman (FT-Raman) spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were used as the main analytical techniques for the determination of human gallstone structural composition. These techniques provide rapid, qualitative and quantitative information about stone structure. The gallstones were obtained from. 40 patients during both surgical operations and laparoscopy. The results of FT-Raman and FT-IR analysis allowed to distinguish of four main groups of gallstones according their cholesterol and bilirubinate salt content. Our studies were extended to trace element analysis by means of proton induced X-ray emission (PIXE). On 14 elements detected, six elements Ca, Mn, Fe, Cu, Zn and Br were chosen for quantitative analysis. The concentration levels of these elements varied depending the chemical structure of the gallstones. The relationship between Ca and Cu appears to be of particular significance. In this paper a correlation between stone structure and trace element concentrations is presented.