Confocal Raman Microspectroscopy Research Articles

Trans-cinnamaldehyde inhibits Penicillium italicum by damaging mitochondria and inducing apoptosis mechanisms

Plant-derived essential oils have excellent antifungal effects and can be used for the preservation of fresh foods such as fruits and vegetables, but the detailed mechanism has not been fully elucidated. In this study, we investigated the inhibitory effects of trans-cinnamaldehyde on Penicillium italicum, a common pollution fungus in citrus, and explored the antifungal mechanism of trans-cinnamaldehyde by detecting fungal oxidative damage, mitochondrial metabolism, and cell apoptosis. These results showed that trans-cinnamaldehyde made the carboxylic acid cycle deregulated by altering the related enzyme activities (succinate dehydrogenase, malate dehydrogenase) and mid product. Moreover, the level of reactive oxygen species rose sharply while the redox level was out of regulation. The mitochondrial membrane potential collapsed, leading to the leakage of cytochrome c, and then triggering the activation of apoptotic protease, which was further confirmed by the significant increase in caspase-3 activity from (3.6 ± 0.6) U to (8.8 ± 1.1) U (P < 0.05). The cytochrome c in mitochondria was detected by confocal Raman microspectroscopy, the characteristic intensity index (I750/I2944) was decreased, indicating that the cytochrome c in mitochondria was reduced and leakage. Besides, the strong negative correlation between Raman intensity and the amount of cytochrome c leakage was established with the correlation coefficient of -0.9817. This study revealed that destroying the integrity of the mitochondrial membrane, activating the mitochondrial-mediated apoptosis pathway was the in-depth antifungal mechanism of trans-cinnamaldehyde; and Raman spectroscopy technology provided new ideas to study this process with high sensitivity determination of cytochrome c.

Effect of Diabetes Mellitus on Implant Osseointegration of Titanium Screws: An Animal Experimental Study.

ObjectiveTo explore the effect of diabetes mellitus (DM) on implant osseointegration of titanium screws.MethodsSixty rats were randomly divided into a DM group and a control group (each group, n = 30). DM group rats were injected with 1% Streptozotocin solution at 65 mg/kg to establish a DM model. Titanium screws were implanted into the rats' distal femurs in both groups. The rats were sacrificed for micro‐CT scanning, micro‐indentation, biomechanical detection, confocal Raman microspectroscopy, and histological and histomorphometric analysis at 4, 8, and 12 weeks post‐implantation, respectively. Messenger RNA (mRNA) expression and protein expression of the related growth factors around the implant were analyzed using real‐time polymerase chain reaction and Western blots.ResultsAt 4, 8 and 12 weeks, micro‐CT scanning, hematoxylin‐eosin (HE) staining, Gieson's acid‐magenta staining, and fluorescent labeled staining showed disorder in the bone tissue arrangement, a lack of new bone tissue, poor maturity and continuity, and poor trabecular bone parameters around the implant in the DM group. At 4, 8, and 12 weeks, the interfacial bone binding rate in the DM group was significantly lower (16.2% ± 4.8%, 25.7% ± 5.7%, 42.5% ± 5.8%, respectively) than that in the control group (23.6% ± 5.2%, 40.8% ± 6.3%, 64.2% ± 7.3%, respectively; P < 0.05). At 8 and 12 weeks, the elastic modulus (17.0 ± 1.8 and 15.1 ± 1.5 GPa, respectively) and trabecular bone hardness (571 ± 39 and 401 ± 37 MPa, respectively) in the DM group were significantly lower than the elastic modulus (23.4 ± 2.3 and 23.8 ± 1.8 GPa, respectively) and trabecular bone hardness (711 ± 45 and 719 ± 46 MPa, respectively) in the control group (P < 0.05). The maximum load required for the prosthesis pull‐out experiment in the DM group at 4, 8, and 12 weeks (55.14 ± 6.74 N, 73.34 ± 8.43 N, and 83.45 ± 8.32 N, respectively) was significantly lower than that in the control group (77.45 ± 7.48 N, 93.28 ± 8.29 N, and 123.62 ± 9.43 N, respectively, P < 0.05). At 8 and 12 weeks, the mineral‐to‐collagen ratio in the DM group (6.56 % ± 1.35% and 4.45%± 1.25%, respectively) was significantly higher than that in the control group (5.31% ± 1.42% and 3.62% ± 1.33%, respectively, P < 0.05). At 12 weeks, mRNA and protein expression levels of bone morphogenetic protein 2, transforming growth factor‐β1, vascular endothelial growth factor, osteopontin, osteocalcin, and runt‐related transcription factor 2 in the DM group were significantly lower than that in the control group.ConclusionsDM can negatively affect bone osseointegration, manifesting as disorder in bone tissue arrangement around the implant, a lack of new bone tissue, poor maturity and continuity, poor trabecular bone parameters and lower expression of the related growth factors.

A Spatial-Temporal Analysis of Cellular Biopolymers on Leaf Blight-Infected Tea Plants Using Confocal Raman Microspectroscopy.

The objective of the present study was to characterize the temporal and spatial variation of biopolymers in cells infected by the tea leaf blight using confocal Raman microspectroscopy. We investigated the biopolymers on serial sections of the infection part, and four sections corresponding to different stages of infection were obtained for analysis. Raman spectra extracted from four selected regions (circumscribing the vascular bundle) were analyzed in detail to enable a semi-quantitative comparison of biopolymers on a micron-scale. As the infection progressed, lignin and other phenolic compounds decreased in the vascular bundle, while they increased in both the walls of the bundle sheath cells as well as their intracellular components. The amount of cellulose and other polysaccharides increased in all parts as the infection developed. The variations in the content of lignin and cellulose in different tissues of an individual plant may be part of the reason for the plant’s disease resistance. Through wavelet-based data mining, two-dimensional chemical images of lignin, cellulose and all biopolymers were quantified by integrating the characteristic spectral bands ranging from 1,589 to 1,607 cm–1, 1,087 to 1,100 cm–1, and 2,980 to 2,995 cm–1, respectively. The chemical images were consistent with the results of the semi-quantitative analysis, which indicated that the distribution of lignin in vascular bundle became irregular in sections with severe infection, and a substantial quantity of lignin was detected in the cell wall and inside the bundle sheath cell. In serious infected sections, cellulose was accumulated in vascular bundles and distributed within bundle sheath cells. In addition, the distribution of all biopolymers showed that there was a tylose substance produced within the vascular bundles to prevent the further development of pathogens. Therefore, confocal Raman microspectroscopy can be used as a powerful approach for investigating the temporal and spatial variation of biopolymers within cells. Through this method, we can gain knowledge about a plant’s defense mechanisms against fungal pathogens.

Co-localized line-field confocal optical coherence tomography and confocal Raman microspectroscopy for three-dimensional high-resolution morphological and molecular characterization of skin tissues ex vivo.

Line-field confocal optical coherence tomography (LC-OCT) is an optical modality that provides three-dimensional (3D) images of the skin at cellular resolution. Confocal Raman microspectroscopy (CRM) is a label-free optical technique that can provide point measurement of the molecular content of the skin. This work presents a method to co-localize LC-OCT and CRM acquisitions for morpho-molecular analysis of ex vivo skin tissues at cellular level. The co-localization method allows acquisition of Raman spectra at specific locations in a sample identified from a 3D LC-OCT image, with an accuracy of ± 20 µm. The method was applied to the characterization of tattooed skin biopsies with adverse tattoo reactions. LC-OCT images allowed to target specific regions in the biopsies where the presence of tattoo ink was revealed by detection of the Raman signature of ink pigments. Micrometer-sized foreign bodies of various materials as well as inflammatory cells were also identified within the biopsies. From these results, we demonstrate the value of the LC-OCT-CRM co-localization method and its potential for future ex vivo analysis of suspicious skin lesions.

Evaluation of Label-Free Confocal Raman Microspectroscopy for Monitoring Oxidative Stress In Vitro in Live Human Cancer Cells.

Understanding the impact of free radicals and antioxidants in cell biology is vital; however, noninvasive nonperturbative imaging of oxidative stress remains a challenge. Here, we evaluated the ability of label-free Raman spectroscopy to monitor redox biochemical changes in antioxidant (N-acetyl-l-cysteine, NAC) and pro-oxidant (tert-butyl hydroperoxide, TBHP) environments. Cellular changes were compared to fluorescence microscopy using CellROX Orange as a marker of oxidative stress. We also investigated the influence of cell media with and without serum. Incubation of cells with NAC increased the Raman signal at 498 cm−1 from S-S disulphide stretching mode, one of the most important redox-related sensors. Exposure of cells to TBHP resulted in decreased Raman spectral signals from DNA/proteins and lipids (at 784, 1094, 1003, 1606, 1658 and 718, 1264, 1301, 1440, 1746 cm−1). Using partial least squares–discriminant analysis, we showed that Raman spectroscopy can achieve sensitivity up to 96.7%, 94.8% and 91.6% for control, NAC and TBHP conditions, respectively, with specificity of up to 93.5, 90.1% and 87.9%. Our results indicate that Raman spectroscopy can directly measure the effect of NAC antioxidants and accurately characterize the intracellular conditions associated with TBHP-induced oxidative stress, including lipid peroxidation and DNA damage.

Single-Cell Photothermal Analysis Induced by MoS2 Nanoparticles by Raman Spectroscopy.

Two-dimensional nanomaterials, such as MoS2 nanosheets, have been attracting increasing attention in cancer diagnosis and treatment, thanks to their peculiar physical and chemical properties. Although the mechanisms which regulate the interaction between these nanomaterials and cells are not yet completely understood, many studies have proved their efficient use in the photothermal treatment of cancer, and the response to MoS2 nanosheets at the single-cell level is less investigated. Clearly, this information can help in shedding light on the subtle cellular mechanisms ruling the interaction of this 2D material with cells and, eventually, to its cytotoxicity. In this study, we use confocal micro-Raman spectroscopy to reconstruct the thermal map of single cells targeted with MoS2 under continuous laser irradiation. The experiment is performed by analyzing the water O-H stretching band around 3,400 cm−1 whose tetrahedral structure is sensitive to the molecular environment and temperature. Compared to fluorescence-based approaches, this Raman-based strategy for temperature measurement does not suffer fluorophore instability, which can be significant under continuous laser irradiation. We demonstrate that irradiation of human breast cancer MCF7 cells targeted with MoS2 nanosheets causes a relevant photothermal effect, which is particularly high in the presence of MoS2 nanosheet aggregates. Laser-induced heating is strongly localized near such particles which, in turn, tend to accumulate near the cytoplasmic membrane. Globally, our experimental outcomes are expected to be important for tuning the nanosheet fabrication process.

A fast-healing and high-performance metallosupramolecular elastomer based on pyridine-Cu coordination

Elastomers easily undergo a catastrophic failure as soon as a crack is introduced by mechanical damage. Thus, it is extremely important for elastomers to possess fast healing ability, which enables the quick reparation of cracks. However, developing elastomers with fast self-healing ability and high mechanical strength is highly challenging. Herein, we fabricate a metallosupramolecular elastomer by facilely introducing pyridine-Cu coordination into a copolymer of ethyl acrylate and vinyl pyridine. Interestingly, the pyridine-Cu coordination has a strong photothermal effect, which readily increases the sample temperature to 60°C in 30 s under near-infrared light. At this temperature, the sticky reptation modes are activated and thus serve as the driving force for network reorganization and fast self-healing of the metallosupramolecular elastomer. Albeit with a tensile strength of 10 MPa, the scratched and completely fractured samples can be healed within 2 min and 3 h, respectively. Moreover, during the damage and healing processes, the break and reformation of the coordination bonds can be tracked through laser confocal micro-Raman spectroscopy. This provides a microscopic methodology to monitor the bond-level healing kinetics of metallosupramolecular polymers.

Femtosecond laser inscribed Yb:LuAG waveguides: guiding performance, micro-spectroscopy characterizations, and refractive index reconstruction

We report on fabrication of dual-line waveguides in Yb:LuAG crystal by 1030-nm femtosecond laser inscription, 450 fs pulses at a 100 kHz repetition rate. The efficient single-mode guidance is demonstrated in the type II waveguide structures when propagating light along both TE and TM polarization at 632.8 nm and 1064 nm. Based on the configuration, the minimum propagation loss of the 18-µm width waveguide is determined to be 0.55 dB/cm at wavelength of 632.8 nm. Both the lattice-damaged tracks and strain-affected regions are characterized by means of the confocal micro-Raman spectroscopy. In combination with beam propagation calculations, we quantitatively determine the corresponding contribution of each effect to the refractive-index field of the fabricated waveguides.

Safety and efficacy of combined essential oils for the skin barrier properties: In vitro, ex vivo and clinical studies.

To evaluate the safety and the synergistic effects of tea tree, lavender, eucalyptus and tangerine essential oils in combination on the skin using in vitro, ex vivo and clinical studies. The phototoxicity was predicted using 3T3 neutral red uptake phototoxicity test (OECD TG 432). Skin penetration was evaluated by confocal Raman microspectroscopy using direct application of essential oils to pig ears. For the clinical studies, 40 participants were enrolled and randomized in three groups: (1) lavender, eucalyptus and tangerine, (2) the same essential oils plus melaleuca and (3) placebo group. The skin was evaluated by noninvasive techniques before and after a 90-day period of topical use. The essential oils were non-phototoxic, but the tangerine oil showed dose-dependent cytotoxicity (IC50: 33.1µg/ml), presenting 35% of penetration in the viable epidermis. On the contrary, 17.7µg/ml in combination was applied per day in the clinical study and the penetration rate for the combinations (10%, 1.77µg/ml achieving the viable epidermis) guaranteed the safety, since in the clinical study, the application of the four essential oils improved skin barrier and morphologic skin characteristics, as well as increased skin hydration and decreased sebum levels, with no unwanted effects reported. All essential oils studied were considered non-cytotoxic or non-phototoxic separately except tangerine, which present a dose-dependent cytotoxicity. Finally, the essential oils in combination in an appropriate amount were safe and effective in the improvement of the hydrolipidic balance and morphological properties of the skin.

Effect of chlorine on water incorporation in magmatic amphibole: experimental constraints with a micro-Raman spectroscopy approach

Abstract. Amphibole represents an important repository of water (among other volatiles, e.g., chlorine and fluorine) in the lithosphere in all those environments characterized by the circulation of fluids and hydrous melts, such as subduction zones and subcontinental lithospheric mantle. Therefore, detailed knowledge of the mechanisms ruling water incorporation in amphibole is essential to assess the amount of water that can be fixed in the lithosphere by this mineral and, ultimately, gain a better insight into the deep water cycle. Water is incorporated into the structure of amphibole as hydroxyl (OH−), which is hosted in the anion site O(3), and the incorporation is mainly controlled by the oxo-substitution mechanism M(1)Ti14++O(3)O22- M(1)(Mg2+, Fe2+)-1+ O(3)(OH-)-2-. However, the fluids and melts circulating in the lithospheric mantle can be variably enriched in halogens (Cl− and F−) that can substitute OH− in the anion site O(3) of amphibole, thus potentially affecting its water budget. The aim of this study is to evaluate the effect of Cl on the oxo-substitution and the incorporation of water in amphibole. End-loaded piston cylinder experiments were conducted at pressure and temperature conditions compatible with the upper-mantle depth (1.4 GPa and 1015–1050 ∘C) in order to favor the crystallization of amphibole at equilibrium with the coexisting melt. Alkali basalt powder was used as starting material, and water doped with different contents of Cl was added to each experiment. Two ranges of oxygen fugacity (fO2) were investigated at ΔFMQ = −2.6 (log fO2 [experiment] − log fO2 [FMQ buffer]) and ΔFMQ = +1.7, where FMQ is fayalite–magnetite–quartz, in order to preliminarily identify the potential influence of the fO2 on the water budget in amphibole. In this contribution, we propose a new method to quantify water in amphiboles using confocal micro-Raman spectroscopy. The H2O contents range from 2.20 ± 0.10 wt % to 5.03 ± 0.47 wt % in glasses and from 0.93 ± 0.08 wt % to 1.50 ± 0.12 wt % in amphiboles, resulting in a partition coefficient of water between amphibole and glass (Amph/LDH2O) ranging from 0.29 ± 0.06 to 0.52 ± 0.08. Our results show a positive correlation between the Cl content of amphibole (from 0.18 wt % to 0.88 wt %) and the Amph/LDH2O. This effect is ascribed to the incorporation of Cl at the anion site O(3) that influences the oxo-substitution mechanism by impeding the entrance of Ti4+ at the M(1) sites and thus preventing the amphibole dehydrogenation. The effect of Cl reported in this study, which is related to a change in the amphibole crystal structure, highlights that high Cl concentrations in magmatic systems favor the incorporation of water in amphibole rather than in the coexisting melt, although the exchange coefficient between Amph/LDH2O and Amph/LDCl supports a preferential incorporation of water over Cl in amphibole. Therefore, the presence of abundant Cl influences the hydration state of magmas evolving from upper-mantle conditions towards crustal roots with the crystallization of amphibole.

Investigating the cellular responses of osteosarcoma to cisplatin by confocal Raman microspectroscopy.

Confocal Raman Microspectroscopy (CRM) was employed to clarify the cellular response of cisplatin in osteosarcoma (OS) cells with different dosages and incubation times. The K7M2 mouse osteosarcoma cells were treated by cisplatin in 0μM (UT group), 20μM (20T group), and 40μM (40T group) doses for 24-h (24H group) and 48-h (48H group), respectively. Raman spectroscopy was utilized to analyze the drug induced variations of intracellular biochemical components in osteosarcoma cells. The spectral results shows that the main changes in its biochemical composition come from nucleic acids. By adopting three different kernel functions (linear, polynomial, and Gaussian radial basis function (RBF)), principal component analysis combined with support vector machine models (PCA-SVM) was built to address the spectral variations among all investigated groups. Meanwhile, multivariate curve resolution alternating least squares (MCR-ALS) was further utilized to discuss on the chemical interpretation on the acquired spectral results. Moreover, Raman spectral images, which is reconstructed by K-means cluster analysis (KCA) with point-scanned hyperspectral dataset, was applied to illustrate the drug induced compositional and morphological variations in each subcellular region. The achieved results not only prove the application potential of Raman based analytical technique in non-labeled intracellular studies, but also illustrate the detailed compositional and structural information of cisplatin induced OS cell responses from the perspective of multivariate analysis and imaging of Raman spectroscopy.

Influence of the measurement configuration on the results of Raman microspectroscopy of human hair

Increasing interest in spectroscopic studies of human hair raises the question about the accuracy of measurement of their spectra and requires optimisation of experimental facilities. An original method of obtaining transverse hair sections without using a microtome and chemical influence is proposed. The results obtained by confocal Raman microspectroscopy of human hair differently oriented with respect to the optical axis of the measuring setup are compared. It is shown that, in addition to expected changes in the spectra measured at different distances from the hair periphery in the direction to its centre, the spectra measured in the case of hair excitation perpendicular and parallel to its axis are also considerably different.

Ex vivo confocal Raman microspectroscopy of porcine dura mater supported by optical clearing.

The effect of tissue optical clearing (TOC) to increase the probing depth and observe in-depth structure of the ex vivo porcine dura mater was studied by confocal Raman microspectroscopy (CRM). Raman intensities were significantly increased at the depth of 250 μm for all collagen bands after treatment with glycerol. The influence of glycerol on collagen hydration was also investigated. The results indicate that the process of TOC can be divided into three main steps. The first one is a fast process of tissue dehydration accompanied by collagen shrinkage while the second relatively slow process is related to the glycerol penetration into the interfibrillar space of collagen combined with swelling of tissue. The third step is collagen dissociation caused by the high concentration of glycerol. To the best of our knowledge, this study is the first example to introduce the TOC technique in assisting CRM of ex vivo dura mater in-depth probing.

Optical waveguides in Pr:LuAG crystal based on direct femtosecond laser writing

We report on the dual-line waveguides in Pr:LuAG crystal fabricated by femtosecond laser using 1030 nm, 450 fs pulses at a 100 kHz repetition rate. The efficient single-mode guidance is demonstrated in the type II waveguide structures when propagating light along both TE and TM polarization at 632.8 nm. The minimum propagation loss of 4.07 dB/cm is obtained in the as-fabricated waveguide in width of 18 μm. Both the lattice-damaged tracks and strain-affected regions are characterized by means of the confocal micro-Raman spectroscopy, and the refractive index modification is also analyzed. The micro-luminescence result indicates that the Pr3+ fluorescence is well preserved in the Pr:LuAG waveguide.

Optical coherence tomography-guided confocal Raman microspectroscopy for rapid measurements in tissues.

We report a joint system with both confocal Raman spectroscopy (CRS) and optical coherence tomography (OCT) modules capable of quickly addressing the region of interest in a tissue for targeted Raman measurements from OCT. By using an electrically tunable lens in the Raman module, the focus of the module can be adjusted to address any specific depth indicated in an OCT image in a few milliseconds. We demonstrate the performance of the joint system in the depth dependent measurements of an ex vivo swine tissue and in vivo human skin. This system can be useful in measuring samples embedded with small targets, for example, to identify tumors in skin in vivo and assessment of tumor margins, in which OCT can be used to perform initial real-time screening with high throughput based on morphological features to identify suspicious targets then CRS is guided to address the targets in real time and fully characterize their biochemical fingerprints for confirmation.

Non-Destructive Spatial Mapping of Glycosaminoglycan Loss in Native and Degraded Articular Cartilage Using Confocal Raman Microspectroscopy.

Articular cartilage is a collagen-rich tissue that provides a smooth, lubricated surface for joints and is also responsible for load bearing during movements. The major components of cartilage are water, collagen, and proteoglycans. Osteoarthritis is a degenerative disease of articular cartilage, in which an early-stage indicator is the loss of proteoglycans from the collagen matrix. In this study, confocal Raman microspectroscopy was applied to study the degradation of articular cartilage, specifically focused on spatially mapping the loss of glycosaminoglycans (GAGs). Trypsin digestion was used as a model for cartilage degradation. Two different scanning geometries for confocal Raman mapping, cross-sectional and depth scans, were applied. The chondroitin sulfate coefficient maps derived from Raman spectra provide spatial distributions similar to histological staining for glycosaminoglycans. The depth scans, during which subsurface data were collected without sectioning the samples, can also generate spectra and GAG distributions consistent with Raman scans of the surface-to-bone cross sections. In native tissue, both scanning geometries demonstrated higher GAG content at the deeper zone beneath the articular surface and negligible GAG content after trypsin degradation. On partially digested samples, both scanning geometries detected an ∼100 μm layer of GAG depletion. Overall, this research provides a technique with high spatial resolution (25 μm pixel size) to measure cartilage degradation without tissue sections using confocal Raman microspectroscopy, laying a foundation for potential in vivo measurements and osteoarthritis diagnosis.

Confocal Fluorescence Microscopy and Confocal Raman Microspectroscopy of X-ray Irradiated LiF Crystals

Radiation-induced color centers locally produced in lithium fluoride (LiF) are successfully used for radiation detectors. LiF detectors for extreme ultraviolet radiation, soft and hard X-rays, based on photoluminescence from aggregate electronic defects, are currently under development for imaging applications with laboratory radiation sources, as well as large-scale facilities. Among the peculiarities of LiF-based detectors, noteworthy ones are their very high intrinsic spatial resolution across a large field of view, wide dynamic range, and versatility. LiF crystals irradiated with a monochromatic 8 keV X-ray beam at KIT synchrotron light source (Karlsruhe, Germany) and with the broadband white beam spectrum of the synchrotron bending magnet have been investigated by optical spectroscopy, laser scanning confocal microscopy in fluorescence mode, and confocal Raman micro-spectroscopy. The 3D reconstruction of the distributions of the color centers induced by the X-rays has been performed with both confocal techniques. The combination of the LiF crystal capability to register volumetric X-ray mapping with the optical sectioning operations of the confocal techniques has allowed performing 3D reconstructions of the X-ray colored volumes and it could provide advanced tools for 3D X-ray detection.

Interactions between recrystallized rice starch and flavor molecules

Two flavor compounds in cooked rice—2,3-butanedione and 2-acetyl-1-pyrroline were selected as representative flavors that could respectively form B- and V-type crystal complexes with starch. Interactions between recrystallized starch and these flavor compounds were systematically investigated using Fourier-transform infrared (FT-IR), laser confocal micro-Raman (LCM-Raman) spectroscopy and 13C cross-polarization/magic angle spinning nuclear magnetic resonance (13C CP/MAS NMR). Results of FT-IR and LCM-Raman showed that 2,3-butanedione and 2-acetyl-1-pyrroline molecules could interact with recrystallized starch via hydrogen bonding affecting the molecular water environment of starch but with different modes of action. 13C CP/MAS NMR results further indicated that flavor molecules affect the water distribution microenvironment and starch chains conformations in the recrystallized region. The 2-acetyl-1-pyrroline molecules could potentially enter the hydrophobic cavities of B- and V-type crystals, whereas 2,3-butanedione could only interact with the starch chains. These results could enrich knowledge on the flavor retention mechanisms of recrystallized starch.

Design of a confocal micro-Raman spectroscopy system and research on microplastics detection.

Traditional micro-Raman spectroscopy technology has the disadvantages of a weak signal and low signal-to-noise ratio. To fix these issues, a cost-effective and rigorous design method is proposed in this paper, whereby a confocal micro-Raman spectroscopy system is designed and built, and a low-cost reflector and high-pass filter are introduced into the Raman signal-receiving module. The Raman light incident is fully perpendicular to the coupling lens by adjusting the reflection angle of the mirror, making the focus of the coupling lens highly conjugate with the focus of the microscope objective, to enhance the intensity of the Raman signal and improve the signal-to-noise ratio. In order to better apply this technology to the detection and study of microplastics in offshore sediments, a reflective illumination light path is used to avoid the visual interference caused by the capillary structure and opacity of the glass cellulose filter membrane. The detection and analysis of the microplastics on the glass cellulose filter membrane have been carried out by the confocal micro-Raman system designed, which is low cost and capable of obtaining good detection results and meeting the requirements of microplastics detection. The system designed in this paper is expected to be applied to the research and development of Raman detection equipment for microplastics in marine sediments, which is beneficial to promote the development of marine microplastic monitoring technology in the world.

Confocal Raman microspectroscopy combined with chemometrics as a discrimination method of clostridia and serotypes of Clostridium botulinum strains

AbstractRapid and accurate identification of Clostridium botulinum is of great importance because it has been considered as an emerging food‐borne pathogen and potential zoonotic agent. Raman spectroscopy can differentiate bacteria based on Raman scattering spectral patterns of whole cells in a fast, reagentless, and easy‐to‐use manner. This study demonstrates that confocal Raman microspectroscopy (CRM) combined with chemometrics can serve as a fast, reliable, and nondestructive method for detection and identification of C. botulinum at both species and serotypes level without any laborious pre‐treatments. Three significant bacillus pathogens including C. botulinum, C. perfringens, and C. difficile were investigated with CRM. Additionally, two main C. botulinum strains causing botulism, C. botulinum type A, and C. botulinum type B were examined with CRM. Principal component analysis (PCA) was performed to differentiate the three species. PCA and linear discrimination analysis (LDA) were used for serotyping C. botulism strains. Four common and important preprocessing methods including Savitzky–Golay algorithm smoothing (SG), standard normal variate (SNV), multivariate scatter correction (MSC), and Savitzky–Golay algorithm 1st Derivative (SG 1st Der) were applied to improve the accuracy of identification and explore the impact of various single preprocessing methods on the model. The results proved that CRM coupled with chemometrics can be utilized for fast, reliable, and nondestructive identification of clostridia and serotypes of C. botulinum strains. This study proves for the first time that the CRM combined with chemometrics methods can be used as a potential means to detect and identify C. botulinum.