Correction: Confocal Raman microspectroscopy for skin characterization: a comparative study between human skin and pig skin.

Correction for 'Confocal Raman microspectroscopy for skin characterization: a comparative study between human skin and pig skin' by Sana Tfaili et al., Analyst, 2012, 137, 3673-3682, DOI: .

Vibrational Analysis of Lung Tumor Cell Lines: Implementation of an Invasiveness Scale Based on the Cell Infrared Signatures.

Assessing the tumor invasiveness is a paramount diagnostic step to improve the patients care. Infrared spectroscopy access the chemical composition of samples; and in combination with statistical multivariate processing, presents the capacity to highlight subtle molecular alterations associated with malignancy development. Our investigation demonstrated that infrared signatures of cell lines presenting various invasiveness phenotypes contain discriminant spectral features, which are useful informative signals to implement an objective invasiveness scale. This last development reflects the interest of vibrational approach as a candidate biophotonic label-free technique, usable in routine clinics, to characterize quantitatively tumor aggressiveness. In addition, the methodology can reveal the heterogeneity of cancer cells, opening the way to further researches in cancer science.

Probing in vitro ribose induced DNA-glycation using Raman microspectroscopy.

To identify and characterize glycation, induced modifications of DNA are crucial toward understanding their functional significance due to their significant role in the long term control of aging and age-related diseases. In this study, we present the ability of Raman microspectroscopy as a novel analytical technique for a rapid and reliable identification of glycated DNA in a reagent-free manner. We have demonstrated that this technique has potential to provide very small conformational modifications. The combination of principal component analysis (PCA) and two-dimensional (2D) correlation spectroscopy has assisted us to explore in vitro DNA-glycation and provide more insights into the dynamics of the DNA-glycation process in an easier fashion. PCA analysis of Raman spectra shows a clear discrimination between native and glycated DNA samples. On the other hand, 2D correlation Raman analysis provides sequential order of the mechanism of the DNA-glycation process, and most likely, it occurs in the following sequence: Structural modifications of individual nucleobases (G > A > C) → DNA backbone modifications → partial transition of DNA conformations (A to B form). Our observations clearly suggest that the structure of DNA is altered, i.e., a partial transition of DNA backbone conformation from A to B form when glycated, but does not induce any final transition in DNA double helix conformation, and eventually, DNA presents in an intermediate A-B form, more toward the B form.

Investigating the relationship between changes in collagen fiber orientation during skin aging and collagen/water interactions by polarized-FTIR microimaging.

Upon chronological aging, human skin undergoes structural and molecular modifications, especially at the level of type I collagen. This macromolecule is one of the main dermal structural proteins and presents several age-related alterations. It exhibits a triple helical structure and assembles itself to form fibrils and fibers. In addition, water plays an important role in stabilizing the collagen triple helix by forming hydrogen-bonds between collagen residues. However, the influence of water on changes of dermal collagen fiber orientation with age has not been yet understood. Polarized-Fourier Transform Infrared (P-FTIR) imaging is an interesting biophotonic approach to determine in situ the orientation of type I collagen fibers, as we have recently shown by comparing skin samples of different ages. In this work, P-FTIR spectral imaging was performed on skin samples from two age groups (35- and 38-year-old on the one hand, 60- and 66-year-old on the other hand), and our analyses were focused on the effect of H2O/D2O substitution. Spectral data were processed with fuzzy C-means (FCM) clustering in order to distinguish different orientations of collagen fibers. We demonstrated that the orientation was altered with aging, and that D2O treatment, affecting primarily highly bound water molecules, is more marked for the youngest skin samples. Collagen-bound water-related spectral markers were also highlighted. Our results suggest a weakening of water/collagen interactions with age. This non-destructive and label-free methodology allows us to understand better the importance of bound water in collagen fiber orientation alterations occurring with skin aging. Obtaining such structural information could find benefits in dermatology as well as in cosmetics.

Vibrational spectroscopies for the analysis of cutaneous permeation: experimental limiting factors identified in the case of caffeine penetration.

Caffeine is utilised as a reference for permeation studies in dermatology and cosmetology. The present work aimed to monitor the permeation of a caffeine solution through the skin. For this purpose, Raman and infrared studies were performed. Raman microspectroscopy permitted a dynamic follow-up of the caffeine diffusion. In complementary, infrared microimaging provided information of the caffeine localization in the skin by applying multivariate statistical processing on skin tissue sections. Herein, we prove the possibility of tracking low concentrations of caffeine through the skin and we highlight some experimental limitations of vibrational spectroscopies.

Confocal Raman microspectroscopy for skin characterization: a comparative study between human skin and pig skin.

The present paper provides a spectral comparison between abdominal human skin (Transkin) and pig ear skin using confocal Raman microspectroscopy at 660 nm. Pig ear skin is usually utilized as a substitute for human skin for active ingredients assessment in dermatological and cosmetics fields. Herein, the comparison is made at the level of the stratum corneum (SC), the SC/epidermis junction and the viable epidermis. The 660 nm excitation source appears to be the most appropriate wavelength for such skin characterization. From Raman signatures of both skin types, a tentative assignment of vibrations was performed in the fingerprint and the high wavenumber spectral regions. Significant differences were highlighted for lipid content in in-depth spectra and for hyaluronic acid (HA) and carotenoid in SC spectra. Marked tissular variability was also revealed by certain Raman vibrations. These intrinsic molecular data probed by confocal Raman microspectroscopy have to be considered for further applications such as cutaneous drug permeation.

Shedding light on the laser wavelength effect in Raman analysis of skin epidermises.

Confocal Raman microspectroscopy is a promising technique which enables measuring the molecular composition of the skin layers, non-destructively and without extrinsic markers. The Raman approach is increasingly used in skin research but with various experimental conditions. In addition to the different skin types, one of the varying parameters is the wavelength of laser excitation. This parameter contributes strongly in the skin Raman response. The present work aimed to evaluate this effect for 3 different wavelengths, 532, 633 and 785 nm, on pig ear skin models. The Raman signal was assessed in the spectral fingerprint region. According to the Raman response for stability, repeatability, variability and fluorescence contribution, the 785 nm excitation wavelength was shown to be the most suitable for epidermis depth profiling in the fingerprint region.

Confined detection volume of fluorescence correlation spectroscopy by bare fiber probes.

A fiber-tip-based near-field fluorescence correlation spectroscopy (FCS) has been developed for confining the detection volume to sub-diffraction-limited dimensions. This near-field FCS is based on near-field illumination by coupling a scanning near-field optical microscope (SNOM) to a conventional confocal FCS. Single-molecule FCS analysis at 100 nM Rhodamine 6G has been achieved by using bare chemically etched, tapered fiber tips. The detection volume under control of the SNOM system has been reduced over one order of magnitude compared to that of the conventional confocal FCS. Related factors influencing the near-field FCS performance are investigated and discussed in detail. In this proof-of-principle study, the preliminary experimental results suggest that the fiber-tip-based near-field FCS might be a good alternative to realize localized analysis at the single-molecule level.

New insights into spectral histopathology: infrared-based scoring of tumour aggressiveness of squamous cell lung carcinomas.

Spectral histopathology, based on infrared interrogation of tissue sections, proved a promising tool for helping pathologists in characterizing histological structures in a quantitative and automatic manner. In cancer diagnosis, the use of chemometric methods permits establishing numerical models able to detect cancer cells and to characterize their tissular environment. In this study, we focused on exploiting multivariate infrared data to score the tumour aggressiveness in preneoplastic lesions and squamous cell lung carcinomas. These lesions present a wide range of aggressive phenotypes; it is also possible to encounter cases with various degrees of aggressiveness within the same lesion. Implementing an infrared-based approach for a more precise histological determination of the tumour aggressiveness should arouse interest among pathologists with direct benefits for patient care. In this study, the methodology was developed from a set of samples including all degrees of tumour aggressiveness and by constructing a chain of data processing steps for an automated analysis of tissues currently manipulated in routine histopathology.

Cellular Cholesterol Distribution Influences Proteolytic Release of the LRP-1 Ectodomain.

Low-density lipoprotein receptor-related protein-1 (LRP-1) is a multifunctional matricellular receptor composed of a large ligand-binding subunit (515-kDa α-chain) associated with a short trans-membrane subunit (85-kDa ß-chain). LRP-1, which exhibits both endocytosis and cell signaling properties, plays a key role in tumor invasion by regulating the activity of proteinases such as matrix metalloproteinases (MMPs). LRP-1 is shed at the cell surface by proteinases such as membrane-type 1 MMP (MT1-MMP) and a disintegrin and metalloproteinase-12 (ADAM-12). Here, we show by using biophysical, biochemical, and cellular imaging approaches that efficient extraction of cell cholesterol and increased LRP-1 shedding occur in MDA-MB-231 breast cancer cells but not in MDA-MB-435 cells. Our data show that cholesterol is differently distributed in both cell lines; predominantly intracellularly for MDA-MB-231 cells and at the plasma membrane for MDA-MB-435 cells. This study highlights the relationship between the rate and cellular distribution of cholesterol and its impact on LRP-1 shedding modulation. Altogether, our data strongly suggest that the increase of LRP-1 shedding upon cholesterol depletion induces a higher accessibility of the sheddase substrate, i.e., LRP-1, at the cell surface rather than an increase of expression of the enzyme.

Monitoring caffeine and resveratrol cutaneous permeation by confocal Raman microspectroscopy.

Dynamic follow-up of exogenous molecules permeation through the skin is one among many competing applications for confocal Raman microspectroscopy. Previous studies showed the feasibility of tracking actives through the skin; the next step should be recording in vivo kinetics. Thus, we conducted a study to evaluate the possibility of detecting low concentrations of caffeine and resveratrol solutions through the skin using confocal Raman microspectroscopy. After topical application of each active on the skin surface, Raman profiles were recorded over nine hours. The challenge was to pursuit these actives respecting the concentration used in some dermatological formulations. Molecules were successfully detected and kinetic profiles were registered over time. The heterogeneity of skin structure and the complexity of molecules diffusion were reflected through the kinetic results.