Label‐free multiphoton microscopy reveals altered tissue architecture in hippocampal sclerosis

The properties and structure of tissue can be visualized without labeling or preparation by multiphoton microscopy combining coherent anti‐Stokes Raman scattering (CARS), addressing lipid content, second harmonic generation (SHG) showing collagen, and two‐photon excited fluorescence (TPEF) of endogenous fluorophores. We compared samples of sclerotic and nonsclerotic human hippocampus to detect pathologic changes in the brain of patients with pharmacoresistant temporomesial epilepsy (n = 15). Multiphoton microscopy of cryosections and bulk tissue revealed hippocampal layering and micromorphologic details in accordance with reference histology: CARS displayed white and gray matter layering and allowed the assessment of axonal myelin. SHG visualized blood vessels based on adventitial collagen. In addition, corpora amylacea (CoA) were found to be SHG‐active. Pyramidal cell bodies were characterized by intense cytoplasmic endogenous TPEF. Furthermore, diffuse TPEF around blood vessels was observed that co‐localized with positive albumin immunohistochemistry and might indicate degeneration‐associated vascular leakage. We present a label‐free and fast optical approach that analyzes pathologic aspects of HS. Hippocampal layering, loss of pyramidal cells, and presence of CoA indicative of sclerosis are visualized. Label‐free multiphoton microscopy has the potential to extend the histopathologic armamentarium for ex vivo assessment of changes of the hippocampal formation on fresh tissue and prospectively in vivo.     

Raman spectroscopy for early real-time endoscopic optical diagnosis based on biochemical changes during the carcinogenesis of Barrett’s esophagus

Raman spectroscopy is a spectroscopic technique based on the inelastic scattering of monochromatic light that represents the molecular composition of the interrogated volume to provide a direct molecular fingerprint. Several investigations have revealed that confocal Raman spectroscopy can differentiate non-dysplastic Barrett’s esophagus from esophageal high-grade dysplasia and adenocarcinoma with high sensitivity and specificity. An automated on-line Raman spectral diagnostic system has made it possible to use Raman spectroscopy to guide accurate target biopsy instead of multiple random forceps-biopsies,this novel system is expected to improve in vivo precancerous diagnosis and tissue characterization of Barrett’s esophagus.     

Freeze‐drying as a preserving preparation technique for in vitro testing of human skin

In vitro testing of drugs with excised human skin is a valuable prerequisite for clinical studies. However, the analysis of excised human skin presents several obstacles. Ongoing drug diffusion, microbial growth and changes in hydration state influence the results of drug penetration studies. In this work, we evaluate freeze‐drying as a preserving preparation method for skin samples to overcome these obstacles. We analyse excised human skin before and after freeze‐drying and compare these results with human skin in vivo. Based on comprehensive thermal and spectroscopic analysis, we demonstrate comparability to in vivo conditions and exclude significant changes within the skin samples due to freeze‐drying. Furthermore, we show that freeze‐drying after skin incubation with drugs prevents growth of drug crystals on the skin surface due to drying effects. In conclusion, we introduce freeze‐drying as a preserving preparation technique for in vitro testing of human skin.     

矿物药雄黄的红外及拉曼光谱鉴定

目的:对3批雄黄生品及1批雄黄饮片进行红外光谱、拉曼光谱研究.方法:利用傅立叶红外光谱法、激光拉曼光谱并结合二阶导数拉曼光谱对各雄黄样品进行鉴别分析.结果:各样品的红外光谱在3 400,1 630 cm-1附近出现了吸收峰,在1 500～400 cm-1也出现了吸收峰,但均不是雄黄的红外特征吸收峰,各样品的拉曼光谱及其二阶导数谱均在182,234,271,342 cm-1等波数位置出现了特征性较强的拉曼振动峰.结论:红外光谱法不适用于雄黄的特征鉴别,拉曼光谱能较好地反映出雄黄的特征吸收峰,具有快速、简便、准确等优点,该法值得在中药鉴定中得到更广泛的应用.     

SERS and resonance Raman studies of p-aminoazobenzene on gold and silver electrodes

Surface-enhanced Raman scattering (SERS) spectra and cyclic voltammetry were used to detect the products of the oxidation and reduction of p-aminoazobenzene (PAAB) on roughened gold and silver electrodes in acidic and neutral solutions.The results indicated that oligomerization products are formed during the oxidation of PAAB on a gold electrode. We identified these products as oligomers formed by CN coupling of the PAAB cation radicals. The same products are formed on a silver electrode at a lower potential as the result of a photoelectrochemical reaction.The measurements carried out in the negative potential range proved that PAAB undergoes irreversible reduction in acidic media and reversible reduction to hydrazobenzene in neutral media.     

腮腺良性肿瘤拉曼光谱特征及诊断模型研究

目的 研究腮腺良性肿瘤拉曼光谱(Raman spectra)特征,并结合统计学方法建立诊断分类模型.方法 收集腮腺正常组织、腮腺多形性腺瘤和Warthin瘤组织样本各20例,以785 nm波长近红外激发光对样本进行拉曼光谱扫描,分析不同组织光谱的特征,应用主成分分析法(principle component analy...     

Similar appearance,different mechanisms: xerosis in HIV,atopic dermatitis and ageing

Xerosis is one of the most common dermatologic disorders occurring in the elderly and in patients with atopic dermatitis (AD) and human immunodeficiency virus (HIV) infection. Xerosis has been linked to an impaired skin barrier function of the stratum corneum. Using Raman microspectroscopy, we concentrated on deeper skin layers, viable epidermis and dermis of 47 volunteers and associated molecular alterations to the evolution of xerosis and the skin barrier, for example, lipid, water and antioxidant content. A decrease in lipids within the viable epidermis is found for elderly and HIV‐patients. Lipid and water values of AD patients and their healthy reference group are similar. Decreases in lipids and simultaneous increases in water are found in the dermis for HIV and AD patients in comparison to their healthy reference groups. Excessive levels of epidermal carotenoids, mainly lycopene, in HIV‐patients were found potentially leading to adverse effects such as premature skin ageing.     

Raman Spectroscopy as a Novel Method for the Characterization of Polydioxanone Medical Stents Biodegradation

Polydioxanone (PPDX), as an FDA approved polymer in tissue engineering, is an important component of some promising medical devices, e.g., biodegradable stents. The hydrolytic degradation of polydioxanone stents plays a key role in the safety and efficacy of treatment. A new fast and convenient method to quantitatively evaluate the hydrolytic degradation of PPDX stent material was developed. PPDX esophageal stents were degraded in phosphate-buffered saline for 24 weeks. For the first time, the changes in Raman spectra during PPDX biodegradation have been investigated here. The level of PPDX hydrolytic degradation was determined from the Raman spectra by calculating the area under the 1732 cm⁻¹ peak shoulder. Raman spectroscopy, unlike Fourier transform infrared (FT-IR) spectroscopy, is also sensitive enough to monitor the decrease in the dye content in the stents during the degradation. Observation by a scanning electron microscope showed gradually growing cracks, eventually leading to the stent disintegration. The material crystallinity was increasing during the first 16 weeks, suggesting preferential degradation of the amorphous phase. Our results show a new easy and reliable way to evaluate the progression of PPDX hydrolytic degradation. The proposed approach can be useful for further studies on the behavior of PPDX materials, and for clinical practice.     

Femtosecond Laser Fabrication of Anisotropic Structures in Phosphorus- and Boron-Doped Amorphous Silicon Films

Femtosecond laser-modified amorphous silicon (a-Si) films with optical and electrical anisotropy have perspective polarization-sensitive applications in optics, photovoltaics, and sensors. We demonstrate the formation of one-dimensional femtosecond laser-induced periodic surface structures (LIPSS) on the surface of phosphorus- (n-a-Si) and boron-doped (p-a-Si) amorphous silicon films. The LIPSS are orthogonal to the laser polarization, and their period decreases from 1.1 ± 0.1 µm to 0.84 ± 0.07 µm for p-a-Si and from 1.06 ± 0.03 to 0.98 ± 0.01 for n-a-Si when the number of laser pulses per unit area increases from 30 to 120. Raman spectra analysis indicates nonuniform nanocrystallization of the irradiated films, with the nanocrystalline Si phase volume fraction decreasing with depth from ~80 to ~40% for p-a-Si and from ~20 to ~10% for n-a-Si. LIPSS’ depolarizing effect, excessive ablation of the film between LIPSS ridges, as well as anisotropic crystalline phase distribution within the film lead to the emergence of conductivity anisotropy of up to 1 order for irradiated films. Current–voltage characteristic nonlinearity observed for modified p-a-Si samples may be associated with the presence of both the crystalline and amorphous phases, resulting in the formation of potential barriers for the in-plane carrier transport and Schottky barriers at the electric contacts.     

The Wavelength-Dependent SERS Template Based on a Nanopillar Array

Surface-enhanced Raman spectroscopy (SERS) can be regarded as a powerful tool for probing chemical molecules by effectively enhancing Raman signals. However, the enhancement factors depend on the SERS template, the probed molecular structures, and the excitation laser wavelength. Herein, we proposed a simple and easily fabricated nanostructured template for SERS and analyzed the wavelength-dependent factors. Three types of golden nanopillar arrays on silicon wafers were designed and manufactured. The SERS signals of the Rhodamine 6G (R6G) molecules were extracted. Three laser sources, a blue 17 mW 458 nm diode laser, a green 20 mW 532 nm laser, and a red 6 mW 633 nm laser, were employed as the excitation laser sources. The 458 nm laser was located far from the resonate spectrum of R6G. The optical intensity distributions for the different SERS templates excited by three laser beams were also simulated. The enhancement factors (EFs) of R6G on the three nanostructured templates were measured and compared. The photoluminescence spectrum of the nanostructured templates and SERS signals of R6G were also measured. In addition, the experimental results concerned optical simulations. The analysis tool that was used was a convolution profile of multiple Lorentzian line shapes with a Gaussian profile. It is helpful to understand the SERS signals when the excitation laser wavelength is located out of the resonance region of molecules. It can also provide a new design approach to fabricate an SERS Template with a nanopillar array for different excitation wavelengths.