High-Frequency Raman Analysis in Biological Tissues Using Dual-Wavelength Excitation Raman Spectroscopy.

A dual-wavelength excitation Raman probe with laser inputs at 866 nm or 1064 nm is customized and integrated into a compact Raman spectrometer that is based on an InGaAs detector. Under 1064 nm illumination, the spectrometer detects fingerprint Raman signals below 2000 cm-1. While under 866 nm illumination, the spectral range is extended to cover high-frequency region (2400-4000 cm-1) that includes major C-H and O-H Raman vibrations. We demonstrate that the dual excitation InGaAs Raman is beneficial in detecting high-frequency Raman signals, especially water contents in high-fluorescent biological samples such as human dental tissues, grape skin, and plum skin due to the suppressed fluorescence interference.

Comparative Analysis of Long-Term Variation Characteristics of SO2, NO2, and O3 in the Ecological and Economic Zones of the Western Sichuan Plateau, Southwest China.

Sulfur dioxide (SO2), nitrogen dioxide (NO2), and ozone (O3) are important atmospheric pollutants that affect air quality. The long-term variations of SO2 and NO2 in 2008-2018 and O3 in 2015-2018 in the relatively less populated ecological and economic zones of Western Sichuan Plateau, Southwest China were analyzed. In 2008-2018, the variations in SO2 and NO2 in the ecological zone were not significant, but Ganzi showed a slight upward trend. SO2 decreased significantly in the economic zone, especially in Panzhihua, where NO2 changes were not obvious. From 2015 to 2018, the concentration of O3 in the ecological zone increased significantly, while the economic zone showed a downward trend. The rising trend of the concentration ratio of SO2 to NO2 in the ecological zone and the declining trend in the economic zone indicate that the energy consumption structure of these two zones is quite different. The lower correlation coefficients between NO2 and O3 in the Western Sichuan Plateau imply that the variations of O3 are mainly affected by the regional background. The effects of meteorological factors on SO2, NO2, and O3 were more obvious in the economic zone where there are high anthropometric emissions.

Full-scale Raman imaging for dental caries detection.

Early detection of dental caries is critical for avoiding more invasive and advanced treatment at a later stage. However, currently available techniques are unsatisfactory for early detection. Raman spectroscopy is known to have both high sensitivity and specificity in the analysis of mineral content in a tooth; but translating Raman spectroscopy to clinical caries detection remains a challenge. In this study, we report a full-scale Raman imaging system that can provide fast full-scale (~7 mm in diameter) tooth mineral analysis which could be feasible for clinical application. The results show that the Raman imaging system could not only confirm carious lesions that are obvious to the naked eye but also identify those which are not conclusive to traditional visual examination and probing.

A Point-of-Care Raman Spectroscopy-Based Device for the Diagnosis of Gout and Pseudogout: Comparison With the Clinical Standard Microscopy.

OBJECTIVE: To demonstrate the usefulness of a novel medical device based on Raman spectroscopy for the rapid point-of-care diagnosis of gout and pseudogout. METHODS: A shoebox-sized point-of-care Raman spectroscopy (POCRS) device was developed for use in the diagnosis of gout and pseudogout. The device included a disposable syringe microfiltration kit to collect arthropathic crystals from synovial fluid and a customized automated Raman spectroscopy system to chemically identify crystal species. Diagnosis according to the findings of POCRS was compared with the clinical standard diagnosis based on compensated polarized light microscopy (CPLM) of synovial fluid aspirates collected from symptomatic patients (n = 174). Kappa coefficients were used to measure the agreement between POCRS and CPLM findings. RESULTS: Overall, POCRS and CPLM results were consistent in 89.7% of samples (156 of 174). For the diagnosis of gout, the kappa coefficient for POCRS and CPLM was 0.84 (95% confidence interval [95% CI] 0.75-0.94). For the diagnosis of pseudogout, the kappa coefficient for POCRS and CPLM was 0.61 (95% CI 0.42-0.81). CONCLUSION: Kappa coefficients indicated that there was excellent agreement between POCRS and CPLM for the diagnosis of gout, with good agreement for the diagnosis of pseudogout. The POCRS device holds the potential to standardize and expedite the time to clinical diagnosis of gout and pseudogout, especially in settings where certified operators trained for CPLM analysis are not available.

Wide-field Raman imaging of dental lesions.

Detection of dental caries at the onset remains as a great challenge in dentistry. Raman spectroscopy could be successfully applied towards detecting caries since it is sensitive to the amount of Raman active mineral crystals, the most abundant component of enamel. Effective diagnosis requires full examination of a tooth surface via Raman mapping. Point-scan Raman mapping is not clinically relevant (feasible) due to lengthy data acquisition time. In this work, a wide-field Raman imaging system was assembled based on a high-sensitivity 2D CCD camera for imaging the mineralization status of teeth with lesions. Wide-field images indicated some lesions to be hypomineralized and others to be hypermineralized. The observations of wide-field Raman imaging were in agreement with point-scan Raman mapping. Therefore, sound enamel and lesions can be discriminated by Raman imaging of the mineral content. In conclusion, wide-field Raman imaging is a potentially useful tool for visualization of dental lesions in the clinic.

A customized Raman system for point-of-care detection of arthropathic crystals in the synovial fluid.

Monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) are the most frequently observed crystals in joint space, leading to painful arthropathies. Correct diagnosis of the crystal identity is critical for the appropriate course of treatment. In this work, a custom Raman device in combination with a practical and efficient sample preparation method is used for chemically selective diagnosis of MSU and CPPD crystals in an automated fashion. The samples were prepared by brief enzymatic digestion treatment of synovial fluid followed by a customized filtration process which was able to congregate crystals over a submillimeter sized spot. The data acquisition and collection were automated to collect multiple spectra distributed over the filtration spot. The performance of the cost-efficient Raman system was compared to a research-grade high fidelity Raman instrument. The custom-designed Raman device could detect MSU crystals at sub-clinical concentrations of 0.1 µg mL(-1) and 1 µg mL(-1) for CPPD crystals. This practical sample preparation approach in tandem with the low-cost customized Raman device has potential to be a novel tool for point-and-shoot Raman diagnosis of arthritic crystals in synovial fluid at the point of care.

Laser Wavelength Dependence of Background Fluorescence in Raman Spectroscopic Analysis of Synovial Fluid from Symptomatic Joints.

Gout is a disease process where the nucleation and growth of crystals in the synovial fluid of joints elicit painful arthritis-like symptoms. Raman spectroscopy is evolving as a potential diagnostic tool in identifying such crystals; however, attainment of sufficient Raman signal while overcoming the background fluorescence remains as a major challenge. The current study focused on assessing whether excitation in 532-700 nm range will provide greater signal intensity than the standard 785 nm while not being impeded by background fluorescence. We characterized the fluorescence spectra, absorption spectra and Raman spectra of synovial fluid from patients who presented "gout-like symptoms" (symptomatic) and controls (asymptomatic). A digestion and filtration method was developed to isolate crystals from synovial fluid while reducing the organic burden. Spectral profile and photobleaching dynamics during Raman spectroscopy were observed under an excitation wavelength range spanning 532 to 785 nm. Absorbance and fluorescence profiles indicated the digestion and filtration worked effectively to extract crystals from symptomatic synovial fluid without introducing additional fluorescence. Raman spectral analyses at 532 nm, 660 nm, 690 nm and 785 nm indicated that both asymptomatic and symptomatic samples had significant levels of fluorescence at excitation wavelengths below 700 nm, which either hindered the collection of Raman signal or necessitated prolonged durations of photobleaching. Raman-based diagnostics were more feasible at the longest excitation wavelength of 785 nm without employing photobleaching. This study further demonstrated that a near-infrared OEM based lower-cost Raman system at 785 nm excitation has sufficient sensitivity to identify crystals isolated from the synovial fluid. In conclusion, while lower excitation wavelengths provide greater signal, the fluorescence necessitates near-infrared wavelengths for Raman analysis of crystal species observed in synovial aspirates.

Controlling the growth behaviour of multilayered films via layer-by-layer assembly with multiple interactions.

Layer-by-layer (LbL) assembly of chitosan-graft-phenyl (CHI-g-Ph) and poly(aspartic-graft-octadecyl) chain (PASP-g-OD) with multiple interactions, i.e. electrostatic interaction and hydrophobic interaction, was studied and the growth rate of multilayered films was found to be strongly dependent on the concentration of NaCl in the aqueous solution. LbL assembly of phenyl chitosan-graft-cyclodextrin (Ph-CHI-g-CD)/PASP-g-OD and chitosan-graft-cyclodextrin (CHI-g-CD)/PASP-g-OD with electrostatic interaction and host-guest interaction was further carried out. The growth of these multilayered films was also affected by the concentration of NaCl in the aqueous solution. For comparison, the LbL assembly of the chitosan (CHI)/polyaspartic acid (PASP) and CHI/PASP-g-OD multilayered films fabricated with electrostatic interaction only were also studied to identify the effect of the multiple interactions on the LbL assembly. (1)H MNR, transmission electron microscopy (TEM), fluorescence spectroscopy and dynamic light scattering (DLS) were used to characterize the polyelectrolytes. LbL assembly processes were monitored by UV-Vis spectroscopy, and the morphology of multilayered films was observed by atomic force microscopy (AFM). This research may provide a new strategy to control the growth behaviour of multilayered films via LbL assembly with multiple interactions.