Implementation of a classification strategy of Raman data collected in different clinical conditions: application to the diagnosis of chronic lymphocytic leukemia.

The literature is rich in proof of concept studies demonstrating the potential of Raman spectroscopy for disease diagnosis. However, few studies are conducted in a clinical context to demonstrate its applicability in current clinical practice and workflow. Indeed, this translational research remains far from the patient's bedside for several reasons. First, samples are often cultured cell lines. Second, they are prepared on non-standard substrates for clinical routine. Third, a unique supervised classification model is usually constructed using inadequate cross-validation strategy. Finally, the implemented models maximize classification accuracy without taking into account the clinician's needs. In this paper, we address these issues through a diagnosis problem in real clinical conditions, i.e., the diagnosis of chronic lymphocytic leukemia from fresh unstained blood smears spread on glass slides. From Raman data acquired in different experimental conditions, a repeated double cross-validation strategy was combined with different cross-validation approaches, a consensus label strategy and adaptive thresholds able to adapt to the clinician's needs. Combined with validation at the patient level, classification results were improved compared to traditional strategies.

Biocompatibility of sol-gel hydroxyapatite-titania composite and bilayer coatings.

Titania-Hydroxyapatite (TiO2/HAP) reinforced coatings are proposed to enhance the bioactivity and corrosion resistance of 316L stainless steel (316L SS). Herein, spin- and dip-coating sol-gel processes were investigated to construct two kinds of coatings: TiO2/HAP composite and TiO2/HAP bilayer. Physicochemical characterization highlighted the bioactivity response of the TiO2/HAP composite once incubated in physiological conditions for 7days whereas the TiO2/HAP bilayer showed instability and dissolution. Biological analysis revealed a failure in human stem cells adhesion on TiO2/HAP bilayer whereas on TiO2/HAP composite the presence of polygonal shaped cells, possessing good behaviour attested a good biocompatibility of the composite coating. Finally, TiO2/HAP composite with hardness up to 0.6GPa and elastic modulus up to 18GPa, showed an increased corrosion resistance of 316L SS. In conclusion, the user-friendly sol-gel processes led to bioactive TiO2/HAP composite buildup suitable for biomedical applications.

Identification of Raman spectroscopic markers for the characterization of normal and adenocarcinomatous colonic tissues.

Raman spectroscopy has been recognised as a valuable analytical tool in biological and medical research. This technique allows probing molecular vibrations of samples without external labels or extensive preparation. This non-destructive optical technique can provide rapid and objective and reproducible measurements of sample biochemistry and identify variations that occur between healthy and diseased tissues. In fact, biochemical changes within tissue may either initiate disease or occur as a result of the disease process. The qualitative analysis of such changes provides important clues in the search for a specific diagnosis and the quantitative analysis of biochemical abnormalities is important in measuring the extent of the disease process, designing therapy and evaluating the efficacy of treatment. In this paper, we discuss one medical application of near-infrared Raman microspectroscopic imaging as a diagnostic tool to investigate, ex vivo, the changes between normal and adenocarcinomatous human colonic tissues. Multivariate statistical analysis was applied on these measured data to identify the molecular composition and distribution of lipids, proteins, mucus and collagens in normal and malignant tissue. Unsupervised hierarchical cluster analysis shows two unsupervised distinct clusters that were assigned to normal and adenocarcinomatous in accordance with conventional histopathological examination. The spectral images allowed good correlation between pseudo-color Raman and histopathological features.

Surface-enhanced Raman scattering and fluorescence spectroscopy reveal molecular interactions of all-trans retinoic acid and RAR gamma ligand-binding domain.

Surface-enhanced Raman scattering and fluorescence were used to investigate the interactions of all-trans retinoic acid with the gamma-type retinoic acid receptor. Raman data revealed a significant attenuation in intensity of the bands originating from the retinoic acid polyenic chain upon receptor binding, with the spectrum being dominantly that of the beta-ionone ring. Fluorescence measurements supported the hydrophobic character of the ligand binding. These novel spectroscopic results are fully consistent with the published X-ray crystallographic data and suggest that these techniques may be valuable additional tools to characterize the interactions of agonists and antagonists with residues in the ligand-binding pockets of retinoid receptor homo- and heterodimers.

Characterization of island films as surface-enhanced Raman spectroscopy substrates for detecting low antitumor drug concentrations at single cell level.

Gold and silver vacuum-deposited island films were characterized by studying deposition variables such as film thickness, evaporation rate, and substrate temperature. For both metals, these parameters were correlated with the surface-enhanced Raman spectroscopy (SERS) effect and an increase in film thickness and low evaporation rates were shown to upshift the wavelength at maximum optical density (lambda max) and increase the optical density of the substrates. In contrast, pre- and postdeposition annealing of gold films led to the formation of substrates that exhibited a downshift of lambda max. Our spectral data also indicated that silver films are substrates that are more suited for SERS applications where high frequency visible excitations are used. Measurements on gold films classified them into two groups: thin Au films (10-50 A) well adapted for red excitations and thicker ones that are operative in the near infrared. SERS results, which were obtained from a single HL60 cell treated with micromolar drug quantities, placed on thin gold island films indicated that these island films could be future promising substrates for SERS imaging at the cellular level.

Structure-activity relation in camptothecin antitumor drugs: why a detailed molecular characterisation of their lactone and carboxylate forms by Raman and SERS spectroscopies?

Lactone and carboxylate forms of potent antitumor agents, camptothecins (CPTs) have been studied by Raman, Fourier-transform Raman (FT-Raman) and surface-enhanced Raman scattering (SERS) spectroscopy. Similarity of the Raman spectra of CPTs with corresponding FT-Raman spectra in the near-infrared allowed the latter to be compared with their SERS counterparts in order to analyse the interaction of the drugs with silver colloids. Different types of silver colloids (reduced with sodium borohydride or sodium citrate, with or without activation by anions) have been evaluated. Citrate-reduced colloid, activated with chloride anions (CAS) has been found to be the best compromise for SERS studies of both forms of CPTs. We suggest that in general CPTs are adsorbed on CAS via the nitrogen in ring B and are more inclined to a flat orientation than to a perpendicular one. However, probable interactions of substitution groups and/or of the COO- groups of hydrolysed CPTs with the CAS surface introduce some particularities in the adsorption patterns. As a result, SERS spectra are highly sensitive to hydrolysis and substitutions at distant rings of CPT and uniquely characteristic of each of the CPT derivatives. The pronounced hydrolysis-induced changes, similar in the Raman and SERS spectra of CPTs, involve similar vibrations in the spectra of different CPTs. Vibrational assignments, proposed for the main Raman and SERS bands of CPT and its derivatives (21-lactam-S-CPT, 10,11-(methylenedioxy)-CPT, CPT-11, SN-38 and topotecan) indicate that most of the bands which decreased upon lactone hydrolysis are those preferentially related to stretching modes of the quinoline rings A and B, and the bands which increased are those of the ring D stretching modes. Our data make the spectroscopic approach very promising for the further investigations of the molecular mechanisms of biological activity of CPTs.