Tri-mode optical biopsy probe with fluorescence endomicroscopy,Raman spectroscopy,and time-resolved fluorescence spectroscopy

We present an endoscopic probe that combines three distinct optical fibre technologies including: A high-resolution imaging fibre for optical endomicroscopy, a multimode fibre for time-resolved fluorescence spectroscopy, and a hollow-core fibre with multimode signal collection cores for Raman spectroscopy. The three fibers are all enclosed within a 1.2 mm diameter clinical grade catheter with a 1.4 mm end cap. To demonstrate the probe's flexibility we provide data acquired with it in loops of radii down to 2 cm. We then use the probe in an anatomically accurate model of adult human airways, showing that it can be navigated to any part of the distal lung using a commercial bronchoscope. Finally, we present data acquired from fresh ex vivo human lung tissue. Our experiments show that this minimally invasive probe can deliver real-time optical biopsies from within the distal lung - simultaneously acquiring co-located high-resolution endomicroscopy and biochemical spectra.     

Raman confocal microscopy and biophysics multiparametric characterization of the skin barrier evolution with age

Skin aging is a multifactorial phenomenon that involves alterations at the molecular, cellular and tissue levels. Our aim was to carry out a multiparametric biophysical and Raman characterization of skin barrier between individuals of different age groups (<24 and >70 years old). Our results showed a significant decrease of lipids to proteins ratio overall the thickness of the stratum corneum and higher lateral packing in the outer part of the SC for elderly. This can explain the decrease in trans epidermal water loss measured values rather than only SC thickening. Both age groups showed similar water content at SC surface while elderly presented higher water content in deep SC and viable epidermis. Mechanical measurements showed a decrease in the elasticity and an increase in the fatigability with age and were correlated with partially bound water. Highest correlation and anti-correlation values were observed for the deepest part of the SC and the viable epidermis.     

Validation model for Raman based skin carotenoid detection

Raman spectroscopy holds promise as a rapid objective non-invasive optical method for the detection of carotenoid compounds in human tissue in vivo. Carotenoids are of interest due to their functions as antioxidants and/or optical absorbers of phototoxic light at deep blue and near UV wavelengths. In the macular region of the human retina, carotenoids may prevent or delay the onset of age-related tissue degeneration. In human skin, they may help prevent premature skin aging, and are possibly involved in the prevention of certain skin cancers. Furthermore, since carotenoids exist in high concentrations in a wide variety of fruits and vegetables, and are routinely taken up by the human body through the diet, skin carotenoid levels may serve as an objective biomarker for fruit and vegetable intake. Before the Raman method can be accepted as a widespread optical alternative for carotenoid measurements, direct validation studies are needed to compare it with the gold standard of high performance liquid chromatography. This is because the tissue Raman response is in general accompanied by a host of other optical processes which have to be taken into account. In skin, the most prominent is strongly diffusive, non-Raman scattering, leading to relatively shallow light penetration of the blue/green excitation light required for resonant Raman detection of carotenoids. Also, sizable light attenuation exists due to the combined absorption from collagen, porphyrin, hemoglobin, and melanin chromophores, and additional fluorescence is generated by collagen and porphyrins. In this study, we investigate for the first time the direct correlation of in vivo skin tissue carotenoid Raman measurements with subsequent chromatography derived carotenoid concentrations. As tissue site we use heel skin, in which the stratum corneum layer thickness exceeds the light penetration depth, which is free of optically confounding chromophores, which can be easily optically accessed for in vivo RRS measurement, and which can be easily removed for subsequent biochemical measurements. Excellent correlation (coefficient R = 0.95) is obtained for this tissue site which could serve as a model site for scaled up future validation studies of large populations. The obtained results provide proof that resonance Raman spectroscopy is a valid non-invasive objective methodology for the quantitative assessment of carotenoid antioxidants in human skin in vivo.     

Superpixel Raman spectroscopy for rapid skin cancer margin assessment

Spontaneous Raman micro‐spectroscopy has been demonstrated great potential in delineating tumor margins; however, it is limited by slow acquisition speed. We describe a superpixel acquisition approach that can expedite acquisition between ~×100 and ×10 000, as compared to point‐by‐point scanning by trading off spatial resolution. We present the first demonstration of superpixel acquisition on rapid discrimination of basal cell carcinoma tumor from eight patients undergoing Mohs micrographic surgery. Results have been demonstrated high discriminant power for tumor vs normal skin based on the biochemical differences between nucleus, collagen, keratin and ceramide. We further perform raster‐scanned superpixel Raman imaging on positive and negative margin samples. Our results indicate superpixel acquisition can facilitate the use of Raman microspectroscopy as a rapid and specific tool for tumor margin assessment.     

Noninvasive characterization of human stratum corneum of undiseased skin of patients with atopic dermatitis and psoriasis as studied by Fourier transform Raman spectroscopy

Etiopathogenetic regulatory disorders of epidermal metabolism and the subsequent changes in the molecular pattern of the stratum corneum play an important role in the clinical differentiation of particular dermatoses (e.g., psoriasis, atopic dermatitis). In this study we present in vitro Fourier transform Raman spectra of the stratum corneum from healthy skin, as well as from clinically undiseased skin of the right heel of atopic and psoriatic volunteers. Differences in the averaged spectra were detected, particularly in the spectral ranges of 1112-1142 (lipid band), 1185-1220, and 1394-1429 cm(-1). By using the first derivative of the averaged spectra and/or a statistical evaluation of the spectroscopic data it was possible to distinguish the skin types examined.     

Comparing Raman and fluorescence lifetime spectroscopy from human atherosclerotic lesions using a bimodal probe

Fluorescence lifetime imaging (FLIm) and Raman spectroscopy are two promising methods to support morphological intravascular imaging techniques with chemical contrast. Both approaches are complementary and may also be used in combination with OCT/IVUS to add chemical specificity to these morphologic intravascular imaging modalities. In this contribution, both modalities were simultaneously acquired from two human coronary specimens using a bimodal probe. A previously trained SVM model was used to interpret the fluorescence lifetime data; integrated band intensities displayed in RGB false color images were used to interpret the Raman data. Both modalities demonstrate unique strengths and weaknesses and these will be discussed in comparison to histologic analyses from the two coronary arteries imaged.

     

Raman spectroscopy of human skin for kidney failure detection

The object of this paper is in vivo study of skin spectral-characteristics in patients with kidney failure by conventional Raman spectroscopy in near infrared region. The experimental dataset was subjected to discriminant analysis with the projection on latent structures (PLS-DA). Application of Raman spectroscopy to investigate the forearm skin in 85 adult patients with kidney failure (90 spectra) and 40 healthy adult volunteers (80 spectra) has yielded the accuracy of 0.96, sensitivity of 0.94 and specificity of 0.99 in terms of identifying the target subjects with kidney failure. The autofluorescence analysis in the near infrared region identified the patients with kidney failure among healthy volunteers of the same age group with specificity, sensitivity, and accuracy of 0.91, 0.84, and 0.88, respectively. When classifying subjects by the presence of kidney failure using the PLS-DA method, the most informative Raman spectral bands are 1315 to 1330, 1450 to 1460, 1700 to 1800 cm⁻¹. In general, the performed study demonstrates that for in vivo skin analysis, the conventional Raman spectroscopy can provide the basis for cost-effective and accurate detection of kidney failure and associated metabolic changes in the skin.     

Portable spectroscopic system for in vivo skin neoplasms diagnostics by Raman and autofluorescence analysis

The present paper studies the applicability of a portable cost‐effective spectroscopic system for the optical screening of skin tumors. in vivo studies of Raman scattering and autofluorescence (AF) of skin tumors with the 785 nm excitation laser in the near‐infrared region included malignant melanoma, basal cell carcinoma and various types of benign neoplasms. The efficiency of the portable system was evaluated by comparison with a highly sensitive spectroscopic system and with the diagnosis accuracy of a human oncologist. Partial least square analysis of Raman and AF spectra was performed; specificity and sensitivity of various skin oncological pathologies detection varied from 78.9% to 100%. Hundred percent accuracy of benign and malignant skin tumors differentiation is possible only with a combined analysis of Raman and AF signals.      

Hydrogen bound water profiles in the skin influenced by optical clearing molecular agents—Quantitative analysis using confocal Raman microscopy

Confocal Raman microscopy has been used to measure depth‐dependent profiles of porcine skin ex vivo in the high wavenumber region after application of molecular optical clearing agents (OCAs). Glycerol (70%) and iohexol (100% Omnipaque [300]) water solutions were used as OCAs and topically applied to porcine ear skin for 30 and 60 minutes. Using Gaussian function–based deconvolution, the changes of hydrogen bound water molecule types have been microscopically analyzed down to the depth of 200 μm. Results show that both OCAs induced skin dehydration (reduction of total water), which is 51.3% for glycerol (60 minutes), 33.1% for glycerol (30 minutes), 8.3% for Omnipaque (60 minutes) and 4.4% for Omnipaque (30 minutes), on average for the 40 to 200 μm depths. Among the water types in the skin, the following reduction was observed in concentration of weakly bound (51.1%, 33.2%, 7.5% and 4.6%), strongly bound (50.4%, 33.0%, 7.9% and 3.4%), tightly bound (63.6%, 42.3%, 26.1% and 12.9%) and unbound (55.4%, 28.7%, 10.1% and 5.9%) water types on average for the 40 to 200 μm depths, post application of glycerol (60 minutes), glycerol (30 minutes), Omnipaque (60 minutes) and Omnipaque (30 minutes), respectively. As most concentrated in the skin, weakly and strongly bound water types are preferentially involved in the OCA‐induced water flux in the skin, and thus, are responsible for optical clearing efficiency.      

Sub millimetre flexible fibre probe for background and fluorescence free Raman spectroscopy

Using the shifted-excitation Raman difference spectroscopy technique and an optical fibre featuring a negative curvature excitation core and a coaxial ring of high numerical aperture collection cores, we have developed a portable, background and fluorescence free, endoscopic Raman probe. The probe consists of a single fibre with a diameter of less than 0.25 mm packaged in a sub-millimetre tubing, making it compatible with standard bronchoscopes. The Raman excitation light in the fibre is guided in air and therefore interacts little with silica, enabling an almost background free transmission of the excitation light. In addition, we used the shifted-excitation Raman difference spectroscopy technique and a tunable 785 nm laser to separate the fluorescence and the Raman spectrum from highly fluorescent samples, demonstrating the suitability of the probe for biomedical applications. Using this probe we also acquired fluorescence free human lung tissue data.     

拉曼光谱在皮肤领域的研究进展

拉曼光谱是一种新型的光学检测技术,常用于材料鉴定。近年来,随着无创检测需求的增加,拉曼光谱逐渐应用于疾病诊断、物质鉴别等生物领域。综述了拉曼光谱在皮肤领域的研究进展,及其对皮肤组织成分鉴别和皮肤疾病诊断的价值,以期推动拉曼光谱广泛应用于皮肤病学的机理研究和临床诊断。     

Molecular characterization of reconstructed skin model by Raman microspectroscopy: comparison with excised human skin

Human skin is directly exposed to different exogenous agents. Many research works have studied the diffusion, interactions, absorption mechanisms, and/or toxicity of these agents toward different cutaneous structures. With the use of living animals for such tests being more and more rejected; and the number of human volunteers being limited; different types of skin models are used. In the last few years, reconstructed epidermis from cell cultures has been frequently employed, and recent changes in the European chemical policy have approved and encouraged the use of these reconstructed models for skin-related research works and assessments. Among the techniques used actually to study the skin, Raman microspectroscopy is a rising and powerful nondestructive technique that detects characteristic molecular vibrations. In this study, we created a spectral database to index the vibration peaks and bands of a well-known reconstructed epidermis model, the Episkin. The comparison with a native epidermis signal enabled us to put in evidence several spectral differences associated with molecular and structural differences between the skin and the reconstructed model, both maintained in living conditions. In addition to that, we have showed the feasibility of tracking the penetration of a pharmaceutical molecule through the Episkin model. (     

Independent component analysis of Raman spectra: Application on paraffin-embedded skin biopsies

Raman spectra provide wealthy but complex information about the chemical constituents of biological samples. Digital processing techniques are usually needed to extract the spectra of chemical constituents and their associated concentration profiles. However, spectral signatures may admit transformations from those recorded on pure constituents and these techniques require a priori knowledge of spectra to be estimated. We propose in this study to analyse paraffin-embedded skin biopsies of malignant and benign tumors dedicated to oncology researches by Raman spectroscopy and advanced signal processing methods. We show that the commonly used principal component analysis (PCA) does not give physically interpretable estimators of spectra and associated concentration profiles. Based on a linear model and taking into account the statistical properties of spectra, independent component analysis (ICA) is used to better estimate the spectra of chemical constituents. The estimators of associated concentration profiles are no longer orthogonal and have only positive values, contrary to PCA. ICA allows to model the paraffin by three Raman spectra and provides good estimators of underlying spectra of the human skin, which is of great interest in oncology since the retrieval of spectral features of different types of skin tumors is sufficient for their discrimination.     

Time-gated interferometric detection increases Raman scattering to fluorescence signal ratio in biological samples

Attainable levels of signal-to-background ratio (SBR) in Raman spectroscopy of biological samples is limited by the presence of endogenous fluorophores. It is customary to remove the ubiquitous fluorescence background using postacquisition data processing. However, new approaches are needed to reduce background contributions and maximize the fraction of the sensor dynamical range occupied by Raman photons. Time-resolved detection using pulsed lasers and time-gated measurements can be used to address the signal-to-background problem in biological samples by limiting light detection to nonresonant interaction phenomena with relaxation time scales occurring on sub-nanosecond time scales, thereby excluding contributions from resonant phenomena such as fluorescence. A time-gated Fourier-transform spectrometer was assembled using a commercially available interferometer, a single channel single-photon avalanche diode and time tagging electronics. A time gate of 300 ps increased the signal-to-background-ratio of the 1440 cm^?1 Raman band from 36% to 69% in an olive oil sample hereby demonstrating the potential of this approach for autofluorescence suppression.      

Interaction of antitumoral 9-aminoacridine drug with DNA and dextran sulfate studied by fluorescence and surface-enhanced Raman spectroscopy

Fluorescence spectroscopy and surface-enhanced Raman spectroscopy are applied to study the interaction of the drug 9-aminoacridine (9AA) with DNA and dextran sulfate. The effect of the electrostatic interaction between the positively charged 9AA and negatively charged groups in relation to the excimer or exciplex emission is investigated. The exciplex emission of 9AA is connected to the intercalation of this drug between nucleic base residues. The importance of negative groups in this interaction is evaluated by using dextran and dextran sulfate as model polymers. The existence of negative charges seems to induce an increase of the drug concentration in the vicinity of the polymers. The role of electrostatic attraction in the 9AA dimerization is confirmed by the excimer emission of 9AA in the presence of dextran sulfate. In the case of DNA, the phosphate groups may induce the drug approach to the DNA chain, but the exciplex fluorescence emission could be due to a charge transfer between the drug and adenine-rich sequences of DNA.     

Raman structural markers of tryptophan and histidine side chains in proteins

The Raman spectrum of a protein contains a wealth of information on the structure and interaction of the protein. To extract the structural information from the Raman spectrum, it is necessary to identify and interpret the marker bands that reflect the structure and interaction in the protein. Recently, new Raman structural markers have been proposed for the tryptophan and histidine side chains by examining the spectra-structure correlations of model compounds. Raman structural markers are now available for the conformation, hydrogen bonding, hydrophobic interaction, and cation-pi interaction of the indole ring of Trp. For His, protonation, tautomerism, and metal coordination of the imidazole ring can be studied by using Raman markers. The high-resolution X-ray crystal structures of proteins provide the basis for testing and modifying the Raman structural markers of Trp and His. The structures derived from Raman spectra are generally consistent with the X-ray crystal structures, giving support for the applicability of most Raman structural makers. Possible modifications and limitations to some marker bands are also discussed.     

Raman spectroscopy and order in biological systems

The Raman spectra in the low 5–200 cm⁻¹ frequency region of metabolically activeE. coli cells have been analyzed to determine whether they are indicators of a possible in vivo underlying order by applying standard concepts derived from the Raman spectroscopy of crystalline systems with varying degrees of order. The analysis suggests that in-vivo space-time ordered structures involving amino acids associated with DNA exist since the low frequency lines of metabolically active cells can be assigned to lines seen in the spectra of crystals of given amino acids known to associated with DNA early in the lifetime of a cell.     

Solid state fluorescence of lyophilized proteins

Fluorescence spectroscopy has been used to measure changes in the tertiary structure of proteins in the solution state. The sensitivity of fluorescence to the protein tryptophan environment has made it a useful tool for studying protein conformation and stability. Using fluorescence spectroscopy to probe structural alterations in lyophilized proteins has been limited due to technical challenges and overwhelming background light scattering. We have investigated the possibility of analyzing lyophilized proteins using the Cary-Eclipse spectrofluorometer by monitoring the fluorescence of the protein therapeutic after subjecting the lyophilized cake to heat-induced accelerated degradation. We have been able to obtain reproducible fluorescence spectra, detecting possible structural changes under these conditions. Fluorescence and circular dichroism spectroscopic analyses of the reconstituted proteins indicated that changes in fluorescence intensities observed in the solid state could be correlated to that in solution and to possible tertiary structural changes. Size exclusion chromatography analysis of protein Y subject to accelerated degradation showed a correlation between decreasing fluorescence intensity and increasing protein Y tetramer in solution, consistent with long-term stability. This suggests that solid state, intrinsic protein fluorescence measurements using the Cary-Eclipse holder may be feasible for long-term stability studies and formulation development.     

Investigation on the effect of fluorescence quenching of bovine serum albumin by cefoxitin sodium using fluorescence spectroscopy and synchronous fluorescence spectroscopy

The reaction mechanism of cefoxitin sodium with bovine serum albumin was investigated using fluorescence spectroscopy and synchronous fluorescence spectroscopy at different temperatures. The results showed that the change of binding constant of the synchronous fluorescence method with increasing temperature could be used to estimate the types of quenching mechanisms of drugs with protein and was consistent with one of fluorescence quenching method. In addition, the number of binding sites, type of interaction force, cooperativity between drug and protein and energy‐transfer parameters of cefoxitin sodium and bovine serum albumin obtained from two methods using the same equation were consistent. Electrostatic force played a major role in the conjugation reaction between bovine serum albumin and cefoxitin sodium, and the type of quenching was static quenching. The primary binding site for cefoxitin sodium was sub‐hydrophobic domain IIA, and the number of binding sites was 1. The value of Hill's coefficients (n_H) was approximately equal to 1, which suggested no cooperativity in the bovine serum albumin–cefoxitin sodium system. The donor‐to‐acceptor distance r < 7 nm indicated that static fluorescence quenching of bovine serum albumin by cefoxitin sodium was also a non‐radiation energy‐transfer process. The results indicated that synchronous fluorescence spectrometry could be used to study the reaction mechanism between drug and protein, and was a useful supplement to the conventional method. Copyright © 2015 John Wiley & Sons, Ltd.     

晚期糖基化终末产物荧光光谱检测法在糖尿病筛查中的应用研究

主要研究人体皮肤晚期糖基化终末产物(Advanced glycation end products,AGE)荧光光谱的检测方法,并对AGE荧光光谱在糖尿病检测中的应用价值进行评估.利用研制的AGE荧光光谱检测装置,分别对73例受试者前臂内侧皮肤组织中AGE的荧光进行检测.同时,采用酶联免疫吸附法(ELISA)对受试者血...