Integrated LIBS-Raman spectroscopy: A comprehensive approach to monitor microplastics and heavy metal contamination in water resources.

The increased use of plastic products and global industrial conditions have contaminated natural resources, especially water, with pollutants such as microplastics and trace elements, including heavy metals. Hence, continuous monitoring of water samples is an urgent requirement. However, the existing microplastic-heavy metal monitoring methodologies require discrete and sophisticated sampling approaches. The article proposes a multi-modal LIBS-Raman spectroscopy system for detecting microplastics and heavy metals from water resources with unified sampling and pre-processing approaches. The accomplishment of the detection process is using a single instrument by exploiting the trace element affinity of microplastics, which operates in an integrated methodology to monitor water samples for microplastic-heavy metal contamination. The polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET) plastic types dominate the identified microplastics from different sampling spots: in an estuary formed by the Swarna River near Kalmadi (Malpe) in Udupi district, and from River Netravathi in Mangalore, Dakshina Kannada District, Karnataka, India. The detected trace elements from microplastic surfaces include heavy metals such as Al, Zn, Cu, Ni, Mn, and Cr and other elements counting Na, Mg, Ca, and Li. The system could record concentrations of trace elements down to 10 ppm, and comparing results with the conventional technique of Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) confirms the ability of the system to detect trace elements from microplastic surfaces. In addition, comparing results with direct LIBS analysis of water from the sampling site shows better results in microplastic-based trace element detection.

A hybrid LIBS-Raman system combined with chemometrics: an efficient tool for plastic identification and sorting.

Classification of plastics is of great importance in the recycling industry as the littering of plastic wastes increases day by day as a result of its extensive use. In this paper, we demonstrate the efficacy of a combined laser-induced breakdown spectroscopy (LIBS)-Raman system for the rapid identification and classification of post-consumer plastics. The atomic information and molecular information of polyethylene terephthalate, polyethylene, polypropylene, and polystyrene were studied using plasma emission spectra and scattered signal obtained in the LIBS and Raman technique, respectively. The collected spectral features of the samples were analyzed using statistical tools (principal component analysis, Mahalanobis distance) to categorize the plastics. The analyses of the data clearly show that elemental information and molecular information obtained from these techniques are efficient for classification of plastics. In addition, the molecular information collected via Raman spectroscopy exhibits clearly distinct features for the transparent plastics (100% discrimination), whereas the LIBS technique shows better spectral feature differences for the colored samples. The study shows that the information obtained from these complementary techniques allows the complete classification of the plastic samples, irrespective of the color or additives. This work further throws some light on the fact that the potential limitations of any of these techniques for sample identification can be overcome by the complementarity of these two techniques. Graphical Abstract ᅟ.

Advanced chemometric methodologies on single shot hyphenated LIBS data for rapid and reliable characterization of plastic classes.

BACKGROUND: Plastic Solid Waste (PSW) sorting is a procedure of paramount importance in the mechanical recycling process of plastics waste. The major limitation of the techniques relying on physical properties of plastics is the time taken for analysis and poor accuracy. Spectroscopy has been shown to be a suitable method in plastic sorting due to its atomic and molecular characterization capabilities, and ability to give results in very short time scales. However, for practical applications it is essential to translate this technique into an automatic technology, by combining it with advanced chemometric tools which can give observer independent judgement. RESULTS: The indigenously developed bi-model Laser Induced Breakdown Spectroscopy (LIBS)-Raman system with single source and single detector can record the LIBS-Raman spectral signals in single-shot mode in a total time frame of 20 ms. Out of the combinations of Principal Component Analysis (PCA) and Partial Least Squares (PLS) with Logistic Regression (LR), Linear Discriminant Analysis (LDA), Support Vector Machine (SVM), and Partial Least Squares-Discriminant Analysis (PLS-DA) based classifiers, the PLS-DA based model showed the maximum classification accuracy with 95 % based on LIBS data and 100 % based on Raman data. The reliability of the model was assessed using 4-fold cross-validation which showed a sensitivity of 90.28 % and specificity of 98.29 % for predictions based on LIBS data, and 99 % sensitivity and 99.82 % specificity for predictions relying on Raman data. SIGNIFICANCE: The results show how the combination of multimodal spectroscopy with chemometric analysis enhances the applicability of spectroscopic techniques for plastic sorting. The classification model successfully classified seven types of post-consumer plastic samples based on combined LIBS and Raman data. With the home-built software for automated prediction, the system takes less than a second to predict the plastic type illustrating the potential of the method for translation to regular routine industrial applications.

Protein profile pattern analysis: A multifarious, in vitro diagnosis technique for universal screening.

Universal health care is attracting increased attention nowadays, because of the large increase in population all over the world, and a similar increase in life expectancy, leading to an increase in the incidence of non-communicable (various cancers, coronary diseases, neurological and old-age-related diseases) and communicable diseases/pandemics like SARS-COVID 19. This has led to an immediate need for a healthcare technology that should be cost-effective and accessible to all. A technology being considered as a possible one at present is liquid biopsy, which looks for markers in readily available samples like body fluids which can be accessed non- or minimally- invasive manner. Two approaches are being tried now towards this objective. The first involves the identification of suitable, specific markers for each condition, using established methods like various Mass Spectroscopy techniques (Surface-Enhanced Laser Desorption/Ionization Mass Spectroscopy (SELDI-MS), Matrix-Assisted Laser Desorption/Ionization (MALDI-MS), etc., immunoassays (Enzyme-Linked Immunoassay (ELISA), Proximity Extension Assays, etc.) and separation methods like 2-Dimensional Polyacrylamide Gel Electrophoresis (2-D PAGE), Sodium Dodecyl-Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), Capillary Electrophoresis (CE), etc. In the second approach, no attempt is made the identification of specific markers; rather an efficient separation method like High-Performance Liquid Chromatography/ Ultra-High-Performance Liquid Chromatography (HPLC/UPLC) is used to separate the protein markers, and a profile of the protein pattern is recorded, which is analysed by Artificial Intelligence (AI)/Machine Learning (MI) methods to derive characteristic patterns and use them for identifying the disease condition. The present report gives a summary of the current status of these two approaches and compares the two in the use of their suitability for universal healthcare.

Serum protein profile study of myocardial infarction using a LED induced fluorescence based HPLC system.

Cardiovascular diseases (CVDs) are the major health conditions for high mortality and morbidity in humans. Delay in the diagnosis of CVDs effect patients long and short-term health condition. In -house assembled UV-light emitting diode (LED) based fluorescence detector for high -performance liquid chromatography (HPLC) (HPLC-LED-IF) system is used to record serum chromatograms of three categories of samples namely, before medicated- myocardial infarction (B-MI), after medicated- MI (A-MI), and normal. The sensitivity and performance of HPLC-LED-IF system is estimated using commercial serum proteins. Statistical analysis tools like, descriptive statistics, principal component analysis (PCA), and Match/ No Match test were applied to visualize the variation in three groups of samples. Statistical analysis of the protein profile data showed fairly good discrimination among the three categories. The receiver operating characteristic (ROC) curve also supported the reliability of the method to diagnose MI.

Protein profile analysis of tear fluid with hyphenated HPLC-UV LED-induced fluorescence detection for the diagnosis of dry eye syndrome.

Tear fluid contains organic and inorganic constituents, variations in their relative concentrations could provide valuable information and can be useful for the detection of several ophthalmological diseases. This report describes the application of the lab-assembled light-emitting diode (LED)-based high-performance liquid chromatography system for protein profiling of tear fluids to diagnose dry eye disease. Principal Component Analysis (PCA), match/no-match, and Artificial Neural Network (ANN) based binary classification of protein profile data were performed for disease diagnosis. Results from the match/no-match test of the protein profile data showed 94.4% sensitivity and 87.8% specificity. ANN with the leaving one out procedure has given 91.6% sensitivity and 93.9% specificity.

Laser induced fluorescence spectroscopy analysis of kidney tissues: A pilot study for the identification of renal cell carcinoma.

The 325 nm-excited autofluorescence spectra from cancerous and normal renal tissues were collected ex vivo biopsy tissue samples, through an optical fiber probe-based system. Noticeable changes in intensity/wavelength were observed in the fluorescence emissions from endogenous fluorophores such as collagen, Nicotinamide adenine dinucleotide (NADH), Vitamin A (retinol), and flavin adenine dinucleotide, in pathological conditions with respect to the normal state. The energy metabolism involved in clear cell renal cell carcinoma (ccRCC) and chromophobe renal cell carcinoma (chRCC) are reflected in the fluorescence emission band at 445 nm due to bound NADH attributed to enhanced oxidative phosphorylation in chRCC and emission at 465 nm contributed by free NADH showing higher glycolytic action in ccRCC. The principal component analysis and one-way ANOVA effectively discriminate ccRCC from chRCC. It is shown that laser induced fluorescence technique with 325 nm excitation can be a suitable technique for optical pathology and in vivo surgical boundary demarcation in renal cell carcinoma.

Correction: Protein profile analysis of tear fluid with hyphenated HPLC-UV LED-induced fluorescence detection for the diagnosis of dry eye syndrome.

[This corrects the article DOI: 10.1039/D3RA04389D.].

Application of HPLC combined with laser induced fluorescence for protein profile analysis of tissue homogenates in cervical cancer.

A highly objective method, High Performance Liquid Chromatography with Laser Induced Fluorescence (HPLC-LIF) technique was used to study the protein profiles of normal and cervical cancer tissue homogenates. A total of 44 samples including normal cervical biopsy samples from the hysterectomy patients and the patients suffering from different stages of the cervical cancer were recorded by HPLC-LIF and analysed by Principle Component Analysis (PCA) to get statistical information on different tissue components. Discrimination of different stages of the samples was carried out by considering three parameters--scores of factor, spectral residual, and Mahalanobis Distance. Diagnostic accuracy of the method was evaluated using Receiver Operating Characteristic (ROC) analysis, and Youden's index (J) plots. The PCA results showed high sensitivity and specificity (~100) for cervical cancer diagnosis. ROC and Youden's index curves for both normal and malignant standard sets show good diagnostic accuracy with high AUC values. The statistical analysis has shown that the differences in protein profiles can be used to diagnose biochemical changes in the tissue, and thus can be readily applied for the detection of cervical cancer, even in situations where a histopathology examination is not easy because of nonavailability of experienced pathologists.

Development of an inter-confirmatory plastic characterization system using spectroscopic techniques for waste management.

Ever-accumulating amounts of plastic waste raises alarming concern over environmental and public health. A practical solution for addressing this threat is recycling, and the success of an industry-oriented plastic recycling system relies greatly on the accuracy of the waste sorting technique adapted. We propose a multi-modal spectroscopic sensor which combines laser-induced breakdown spectroscopy (LIBS) and Raman spectroscopy in a single optical platform for characterizing plastics based on elemental and molecular information to assist the plastic identification-sorting process in recycling industries. The unique geometry of the system makes it compact and cost-effective for dual spectroscopy. The performance of the system in classifying industrially important plastic classes counting PP, PC, PLA, Nylon-1 1, and PMMA is evaluated, followed by the application of the same in real-world plastics comprising PET, HDPE, and PP in different chemical-physical conditions where the system consumes less than 30 ms for acquiring LIBS-Raman signals. The evaluation of the system in characterizing commuting samples shows promising results to be applied in industrial conditions in future. The study on effect of physical-chemical conditions of plastic wastes in characterizing them using the system shows the necessity for combining multiple techniques together. The proposal is not to determine the paramount methodology to characterize and sort plastics, but to demonstrate the advantages of dual-spectroscopy sensors in such applications. The outcomes of the study suggest that the system developed herein has the potential of emerging as an industrial-level plastic waste sorting sensor.

Cardiovascular biomarkers in body fluids: progress and prospects in optical sensors.

Cardiovascular diseases (CVD) are the major causative factors for high mortality and morbidity in developing and developed nations. The biomarker detection plays a crucial role in the early diagnosis of several non-infectious and life-threatening diseases like CVD and many cancers, which in turn will help in more successful therapy, reducing the mortality rate. Biomarkers have diagnostic, prognostic and therapeutic significances. The search for novel biomarkers using proteomics, bio-sensing, micro-fluidics, and spectroscopic techniques with good sensitivity and specificity for CVD is progressing rapidly at present, in addition to the use of gold standard biomarkers like troponin. This review is dealing with the current progress and prospects in biomarker research for the diagnosis of cardiovascular diseases. Expert opinion. Fast diagnosis of cardiovascular diseases (CVDs) can help to provide rapid medical intervention, which can affect the patient's short and long-term health. Identification and detection of proper biomarkers for early diagnosis are crucial for successful therapy and prognosis of CVDs. The present review discusses the analysis of clinical samples such as whole blood, blood serum, and other body fluids using techniques like high-performance liquid chromatography-LASER/LED-induced fluorescence, Raman spectroscopy, mainly, optical methods, combined with nanotechnology and micro-fluidic technologies, to probe patterns of multiple markers (marker signatures) as compared to conventional techniques.

In vivo spectroscopy: optical fiber probes for clinical applications.

INTRODUCTION: Fiber optic probe-based in vivo spectroscopy techniques are fast and highly objective methods for intraoperative diagnoses and minimally invasive surgical interventions for all procedures where endoscopic observations are carried out for cancers of different types. The Raman spectral features provide molecular fingerprint-type information and can reveal the subjects' pathological state in label-free manner, making endoscopy multiplexed fiber optic probe-based devices with the potential for translation from bench to bedside for routine applications. AREAS COVERED: This review provides a general overview of different fiber-optic probes for in vivo measurements with emphasis on Raman spectroscopy for biomedical application. Various aspects such as fiber-optic probe, radiation source, detector, and spectrometer for extracting optimum spectral features have also been discussed. EXPERT OPINION: Optical spectroscopy-based fiber probe systems with 'Chip-on-Tip' technology, combined with machine learning, can in the near future, become a complementary diagnostic tool to magnetic resonance imaging (MRI), computed tomography (CT) scan, ultrasound, etc. Hyperspectral imaging and fluorescence-based devices are in the advanced stage of technology readiness level (TRL), and with advances in lasers and miniature spectroscopy systems, probe-based Raman devices are also coming up.

Development of a spectroscopic technique that enables the saliva based detection of COVID-19 at safe distances.

Research activities are in full swing globally to translate the use of saliva as a non-invasive and highly potential specimen for clinical diagnostics, particularly for COVID-19 detection. Being comprised of a pool of biomarkers also enriched with ACE-2 receptors, saliva can provide vital information regarding the state of the human body. Advancements in biophotonics tools for saliva investigation may offer promise for developing rapid, highly objective, optical modalities for COVID- 19 detection. This article presents concept/design study, which propose the use of Raman/laser induced fluorescence spectroscopic device that have the potential for viral detection via saliva from a safer distance. Noticeable changes of biomarkers present in saliva in response to viral infection can reflect the pathological state, thus can altogether affect the Raman spectral pattern. Monitoring these spectral patterns of saliva, which are further enhanced by using cost effective and reproducible Surface Enhanced Raman Spectroscopy substrates can be a viable option for sensitive and non-invasive viral detection. The spectral information acquired from the optical device can be processed using various multivariate statistical analytical tools, which ultimately facilitate effective viral detection in few minutes. This method doesn't demand the necessity of qualified professionals and sample processing with reagents unlike in RT-PCR test. The proposed optical device can be further modified into a portable form, which can be easily transported for field applications. The stand-off observation, contactless and highly non-invasive technique can be of paramount importance in the current context, where the safer screening of a large population for viral infection by maintaining social distances is a necessity. The proposed stand-off spectroscopic technique can also address the major concern of nosocomial viral transmission amongst healthcare workers during sample collection in a pandemic scenario.

Photonics of human saliva: potential optical methods for the screening of abnormal health conditions and infections.

Human saliva can be treated as a pool of biological markers able to reflect on the state of personal health. Recent years have witnessed an increase in the use of optical devices for the analysis of body fluids. Several groups have carried out studies investigating the potential of saliva as a non-invasive and reliable clinical specimen for use in medical diagnostics. This brief review aims to highlight the optical technologies, mainly surface plasmon resonance (SPR), Raman, and Fourier transform infrared (FTIR) spectroscopy, which are being used for the probing of saliva for diverse biomedical applications. Advances in bio photonics offer the promise of unambiguous, objective and fast detection of abnormal health conditions and viral infections (such as COVID-19) from the analysis of saliva.

Echelle LIBS-Raman system: A versatile tool for mineralogical and archaeological applications.

There are a number of analytical techniques used to study material related problems. Most of them imply experimental determination of parameters and functions by means of which elemental, optical and other properties of materials can be described. Laser Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are highly complementary spectroscopic techniques used for lab, in-situ, and remote analyses of materials. The LIBS-Raman system provides further information compared to other conventional techniques since it can detect the presence of low atomic number-elements, isotopic composition, hydration and structure of trace materials which may be present as surface layers etc., which are very difficult, if not impossible, by portable X-ray based systems. A setup for LIBS and Raman spectroscopy measurements in a single unit has been developed and reported recently by us using an echelle spectrograph system. The system utilizes a single nanosecond pulsed Nd:YAG laser (532 nm) and an ICCD coupled echelle spectrograph for both measurements. The unit has been successfully used for multipurpose applications such as identification of minerals, pigments etc and also for checking quality assurance. The combined atomic and molecular information from the same location on a sample, at several locations, can provide more comprehensive information regarding its properties than using either of these quantities taken singly. In many cases, it has been observed that the high resolution of the echelle spectrograph provides better quality Raman signals by virtue of the small degeneracy/crystal field splitting of many fundamental Raman bands. This can provide valuable information on inclusions in bulk samples, changes due to symmetry alteration or complex formation with surroundings, hydrogen bonding etc. The advantage of echelle system to identify natural and artificial pigments by identifying the minor and trace components by the spectra of the elements therein, is also helpful in many situations. In the present paper, the orthogonal use of LIBS and Raman spectroscopy is assessed and highlighted. The results clearly demonstrate the potential of echelle-based LIBS-Raman system in applications where more detailed information on complex samples like minerals, archaeological artifacts etc, is required with minimum sample damage or consumption.

Dynamics of L-tryptophan in aqueous solution by simultaneous laser induced fluorescence (LIF) and photoacoustic spectroscopy (PAS).

An experimental system for measuring simultaneously photoacoustic (PA) and fluorescence signals is described. The simultaneous measurement of laser induced fluorescence and photoacoustic signals provide a suitable method for the study of different quenching phenomena occurring in fluorescent systems. In this paper we report tryptophan solvation dynamics in water using fluorescence and photoacoustic spectra recorded simultaneously by photoacoustic and fluorescence signals as functions of concentration, indicate that quantum yield is maximum at low concentrations. Also, the energy lost in the fluorescence path of tryptophan, due to different quenching phenomena like self quenching, Resonance energy transfer (RET), solvation relaxation, etc. is clearly seen from the photoacoustic signal intensity which increases as the fluorescence intensity decreases.

A hyphenated echelle LIBS-Raman system for multi-purpose applications.

We have developed and standardized a novel hybrid laser-induced breakdown spectroscopy (LIBS)-Raman system using a single pulsed laser and a high-resolution intensified charge coupled device coupled echelle spectrograph. LIBS and Raman spectroscopy are highly complementary techniques which yield elemental and molecular information. Both techniques share an apparently similar instrumental configuration but need entirely different requirements like spectral range covered, resolution, and light-gathering efficiencies. There are thus many challenges to be faced in developing a combined system. In the present work, we show that an echelle spectrograph combined with a compact Q-switched Nd:YAG laser operating at 532 nm as an excitation source in a portable configuration can be efficiently used for such multi-purpose spectroscopy. Atomic and molecular emissions from the sample surface have been recorded in a gated mode using this setup. Compared to conventional spectrographs, echelle provides simultaneous broad bandpass (250-900 nm) and better spectral resolution at an extremely small fixed slit width of 10 × 50 µm without moving the dispersive elements. The echelle-based hyphenated system provides fast and reliable analysis of materials with combined atomic and molecular spectra of the same spot with better reliability. In this paper, we discuss the optimization of various instrumental parameters and optical components of this hyphenated system using a medium Raman cross section sample, CaCO3. The feasibility of single shot LIBS-Raman measurement capabilities of echelle has also been demonstrated using the developed system.

Laser-induced breakdown spectroscopy-Raman: An effective complementary approach to analyze renal-calculi.

Presence of renal-calculi (kidney stones) in human urethra is being increasingly diagnosed over the last decade and is considered as one of the most painful urological disorders. Accurate analysis of such stones plays a vital role in the evaluation of urolithiasis patients and in turn helps the clinicians toward exact etiologies. Two highly complementary laser-based analytical techniques; laser-induced breakdown spectroscopy (LIBS) and micro-Raman spectroscopy have been used to identify the chemical composition of different types of renal-calculi. LIBS explores elemental characteristics while Raman spectroscopy provides molecular details of the sample. This complete information on the sample composition might help clinicians to identify the key aspects of the formation of kidney stones, hence assist in therapeutic management and to prevent recurrence. The complementarity of both techniques has been emphasized and discussed. LIBS spectra of different types of stones suggest the probable composition of it by virtue of the major, minor and trace elements detected from the sample. However, it failed to differentiate the crystalline form of different hydrates of calcium oxalate stone. This lacuna was overcome by the use of Raman spectroscopy and these results are compared with conventional chemical analysis.

Characterisation of uterine sarcoma cell lines exhibiting MDR phenotype by vibrational spectroscopy.

Multidrug resistance (MDR) enables cancer cells to escape cytotoxic insults of anticancer drugs. Rapid identification of cells exhibiting the MDR phenotype is very important since it can lead to an effective and individual patient based treatment plan. We have investigated a combined vibrational spectroscopic approach, using both micro-Raman and FTIR techniques, in order to characterise a sensitive human uterine sarcoma cell line MES-SA and its multidrug-resistant derivative Garf. In this study, these two complementary methods have been evaluated via the use of principal components analysis (PCA), for discrimination of cells exhibiting the MDR phenotype. Our results indicate that, though they inherently have different sensitivities, both Raman and IR methods can provide a good differentiation of cell phenotypes.

Fourier transform infrared and quasielectron neutron scattering studies on the binding modes of methanol molecules in the confined spaces of HMCM-41 and HZSM-5: role of pore structure and surface acid sites.

Quasielastic neutron scattering (QENS) and Fourier transform infrared spectroscopic studies were carried out on methanol molecules adsorbed in HMCM-41 and HZSM-5 molecular sieves to monitor the effect of pore structure on their occluded state under the conditions of ambient temperature and 5-250 mbar pressures. The QENS results have shown that the pore geometry of the host matrix and the dipolar character of the adsorbate are together responsible for the binding state of guest molecules in the confining medium. Thus, neither translational nor free rotational motion was noticed for methanol molecules adsorbed in HZSM-5, in contrast to benzene and cyclohexane molecules of almost similar size that are reported to undergo a rotational motion under the identical conditions of loading (Phys. Chem. Chem. Phys. 2001, 3, 4449; 2003, 5, 3066). In the case of HMCM-41, a translational motion of occluded methanol molecules was clearly observed with a diffusion constant D approximately 1.5 x 10(-5) cm2 s(-1), as compared to a value of D approximately 2.6 x 10(-5) cm2 s(-1) for its liquid state. These results indicate that the adsorbed methanol experiences a considerable extent of supercooling due to capillary condensation in zeolitic pores, giving rise to formation of a metastable state even at room temperature. In HZSM-5, entrapped methanol exists in an almost solidlike state, whereas in HMCM-41, its density lies between that of the solid and the liquid phases. Infrared spectroscopic study conducted using deuterium-labeled adsorbate and host matrixes have given evidence for different kinds of interactions between the methanol molecules and the host matrix, depending upon the loading. For small loadings the internal hydroxy groups within the pore system get perturbed first, giving rise to formation of the methoxy groups. Multilayer adsorption and capillary condensation of methanol occur for a loading of 0.05 mmol per gram and above, within the pore system and also at the external surface, giving rise to a highly compressed state due to strong intermolecular bonding. At the same time, a considerable amount of exchange occurred between the hydroxy groups of the adsorbed methanol and those of the host matrix. Such exchange of hydroxy groups may play an important role in the catalytic properties of the porous aluminosilicates.