Use of laser-induced breakdown spectroscopy for the differentiation of pathogens and viruses on substrates

Remote Laser-Induced Breakdown Spectroscopy of Bacterial Growths in Carbonate Rocks in a Mars-like Atmosphere

Understanding the past habitable environments of Mars increases the requirement to recognize and examine modern analogs and to evaluate the mechanisms that may preserve biosignatures in them. The phenomenon that originates and preserves possible microbial biosignatures in mineral phases is of particular interest in astrobiology. On Earth, the precipitation of carbonate matrices can be mediated by bacteria. Besides microbialites and other sedimentary structures, carbonate formations can be observed in certain karstic caves. The present work is focused on the remote laser-induced breakdown spectroscopy (LIBS) characterization of cyanobacteria, exploring the possibilities for identification and discrimination on carbonate substrates. For this purpose, the extremophile cyanobacterium Chroococcidiopsis sp. (collected from the Nerja Cave, Malaga, Spain) was analyzed under laboratory-simulated martian conditions in terms of chemical composition and gas pressure. LIBS results related to acquired molecular emission features allowed bacterial differentiation from the colonized mineral substrate. In addition, the limits of detection were estimated with a laboratory-grown culture of the cyanobacterium Microcystis aureginosa. Our results reveal LIBS's capability to detect biological traces under simulated martian conditions. Additionally, the time-resolved analysis of the biological samples demonstrates the selection of optimal temporal conditions as a critical parameter for the preferential acquisition of molecular species in organic material.

Label-free laser spectroscopy for respiratory virus detection: A review

Infectious diseases are among the most severe threats to modern society. Current methods of virus infection detection based on genome tests need reagents and specialized laboratories. The desired characteristics of new virus detection methods are noninvasiveness, simplicity of implementation, real-time, low cost and label-free detection. There are two groups of methods for molecular biomarkers' detection and analysis: (i) a sample physical separation into individual molecular components and their identification, and (ii) sample content analysis by laser spectroscopy. Variations in the spectral data are typically minor. It requires the use of sophisticated analytical methods like machine learning. This review examines the current technological level of laser spectroscopy and machine learning methods in applications for virus infection detection.

Silver Microparticle-Enhanced Laser-Induced Breakdown Spectroscopy

Enhanced emission was observed in the laser-induced breakdown spectroscopy (LIBS) atomic emission spectra of bacterial cells deposited upon a nitrocellulose filtration medium in the presence of one-micron silver microparticles. A deposition chamber was constructed that allowed a uniform coating of the filter with trace amounts of silver microparticles. Masses from 10 to 100 μg were deposited in a circular area of 52.18 mm². A 30 s deposition time was used for all experiments resulting in a mass deposition of 39 μg ± 17 μg. This mass coverage on the filter provided for a single laser shot silver mass ablation of 3.3 ng per laser shot. LIBS spectra were acquired with single-shot 1064 nm laser pulses from specimens of E. coli, M. smegmatis, and E. cloacae deposited on both microparticle-coated filters and blank filters. An increase in emission intensity for all elements detected in the bacterial LIBS spectrum as well as the carbon emission which derives in part from the nitrocellulose filter medium was observed due to the ablation with silver microparticles relative to the intensity measured from the ablation of bacterial cells deposited on a blank filter. The ratio of emission intensity with microparticles to emission intensity without microparticles was measured to be 3.6 for phosphorus, 4.5 for magnesium, 5.3 for calcium, 4.0 for sodium, and 1.2 for carbon. An enhancement in LIBS emission intensity in the range of 1-10 was observed for all the spectra, with an average enhancement ratio of 4.3.

The use of laser-based diagnostics for the rapid identification of blood borne viruses in human plasma samples

AIMS

To demonstrate the use of a laser-based method of detection as a potential diagnostic test for the rapid identification of blood borne viruses in human plasma.

METHODS AND RESULTS

In this study, using light emissions from laser sparks on plasma samples, the successful differentiation of both human immunodeficiency virus (HIV) and hepatitis C virus (HCV) in both residual de-identified plasma samples and plasma samples spiked to clinically relevant levels with each virus were demonstrated using plasma from more than 20 individuals spanning six different blood types (O+, O-, A+, A-, B+, B-).

CONCLUSIONS

These experiments demonstrate that mathematical analysis of spectral data from laser sparks can provide accurate results within minutes. This capability was demonstrated using both spiked laboratory plasma samples and clinical plasma samples collected from infected and uninfected individuals.

SIGNIFICANCE AND IMPACT OF THE STUDY

There is an ongoing need to rapidly detect viral infections and to screen for multiple viral infections. A laser-based approach can achieve sensitive, multiplex detection with minimal sample preparation and provide results within minutes. These properties along with the flexibility to add new agent detection by adjusting the detection programming make it a promising tool for clinical diagnosis. The potential for a laser-based approach has been previously demonstrated using pathogens spiked into human blood to clinically relevant levels. This study demonstrates this same ability to detect infections in clinical and laboratory spiked plasma samples. The ability to differentiate between plasma samples from infected and uninfected donors and determine the virus type using a laser-based diagnostic has not been previously demonstrated. Furthermore, this study is the first demonstration of the capability to differentiate viral infections in clinical plasma samples whereas previously published work used laboratory samples spiked with a virus or dealt with the detection of cancer in clinical plasma samples.

Methodology for the Implementation of Internal Standard to Laser-Induced Breakdown Spectroscopy Analysis of Soft Tissues

The improving performance of the laser-induced breakdown spectroscopy (LIBS) triggered its utilization in the challenging topic of soft tissue analysis. Alterations of elemental content within soft tissues are commonly assessed and provide further insights in biological research. However, the laser ablation of soft tissues is a complex issue and demands a priori optimization, which is not straightforward in respect to a typical LIBS experiment. Here, we focus on implementing an internal standard into the LIBS elemental analysis of soft tissue samples. We achieve this by extending routine methodology for optimization of soft tissues analysis with a standard spiking method. This step enables a robust optimization procedure of LIBS experimental settings. Considering the implementation of LIBS analysis to the histological routine, we avoid further alterations of the tissue structure. Therefore, we propose a unique methodology of sample preparation, analysis, and subsequent data treatment, which enables the comparison of signal response from heterogenous matrix for different LIBS parameters. Additionally, a brief step-by-step process of optimization to achieve the highest signal-to-noise ratio (SNR) is described. The quality of laser-tissue interaction is investigated on the basis of the zinc signal response, while selected experimental parameters (e.g., defocus, gate delay, laser energy, and ambient atmosphere) are systematically modified.

The use of laser-based diagnostics for the rapid identification of infectious agents in human blood

AIMS

To investigate the use of a laser-based method of detection as a potential diagnostic test for the rapid identification of infectious agents in human blood.

METHODS AND RESULTS

In this study, the successful differentiation of blood spiked with viruses, bacteria or protozoan parasites to clinically relevant levels is demonstrated using six blood types (O+, O-, AB+, A+, A-, B+) using blood from different individuals with blood samples prepared in two different laboratories. Experiments were performed using various compositions of filters, experimental set-ups and experimental parameters for spectral capture.

CONCLUSIONS

The potential for developing a laser-based diagnostic instrument to detect the presence of parasites, bacteria and viruses in human blood capable of providing analysis results within minutes was demonstrated.

SIGNIFICANCE AND IMPACT OF THE STUDY

There is an ongoing need for clinical diagnostics to adapt to newly emerging agents and to screen simultaneously for multiple infectious agents. A laser-based approach can achieve sensitive, multiplex detection with minimal sample preparation and provide rapid results (within minutes). These properties along with the flexibility to add new agent detection by simply adjusting the detection programming make it a promising tool for clinical diagnosis.

Laser-induced breakdown spectroscopy (LIBS): a novel technology for identifying microbes causing infectious diseases

With the advent of improved experimental techniques and enhanced precision, laser-induced breakdown spectroscopy (LIBS) offers a robust tool for probing the chemical constituents of samples of interest in biological sciences. As the interest continues to grow rapidly, the domain of study encompasses a variety of applications vis-à-vis biological species and microbes. LIBS is basically an atomic emission spectroscopy of plasma produced by the high-power pulsed laser which is tightly focused on the surface of any kinds of target materials in any phase. Due to its experimental simplicity, and versatility, LIBS has achieved its high degree of interest particularly in the fields of agricultural science, environmental science, medical science, forensic sciences, and biology. It has become a strong and sensitive elemental analysis tool as compared to the traditional gold standard techniques. As such, it offers a handy, rapid, and flexible elemental measurement of the sample compositions, together with the added benefits of less cumbersome sample preparation requirements. This technique has extensively been used to detect various microorganisms, extending the horizon from bacteria, molds, to yeasts, and spores on surfaces, while also being successful in sensing disease-causing viruses. LIBS-based probe has also enabled successful detection of bacteria in agriculture as well. In order for good quality processing of food, LIBS is also being used to detect and identify bacteria such as Salmonella enteric serovar typhimurium that causes food contamination. Differences in soil bacteria isolated from different mining sites are a very good indicator of relative environmental soil quality. In this connection, LIBS has effectively been employed to discriminate both the inter- and intra-site differences of the soil quality across varying mining sites. Therefore, this article summarizes the basic theory and use of LIBS for identifying microbes causing serious agricultural and environmental infectious diseases.

Rapid Identification and Characterization of Francisella by Molecular Biology and Other Techniques

Francisella tularensis is the causative pathogen of tularemia and a Tier 1 bioterror agent on the CDC list. Considering the fact that some subpopulation of the F. tularensis strains is more virulent, more significantly associated with mortality, and therefore poses more threat to humans, rapid identification and characterization of this subpopulation strains is of invaluable importance. This review summarizes the up-to-date developments of assays for mainly detecting and characterizing F. tularensis and a touch of caveats of some of the assays.

Importance of laser-induced breakdown spectroscopy for hard tissues (bone, teeth) and other calcified tissue materials

Laser-induced breakdown spectroscopy (LIBS) as a sensitive optical technique capable of fast multielemental analysis proved to be a versatile tool in different applications. It became visible in the analytical atomic spectroscopy scene in the late 1980s and since then, its applications having been developed continuously in different field of science and technology including biomedical science. Here, we review the use and importance of LIBS for trace element determination in different calcified tissue materials. In this article, we have also reported a comprehensive review of the recent progress of biomedical applications of LIBS.

Detection of biological contaminants on foods and food surfaces using laser-induced breakdown spectroscopy (LIBS)

The rapid detection of biological contaminants, such as Escherichia coli O157:H7 and Salmonella enterica , on foods and food-processing surfaces is important to ensure food safety and streamline the food-monitoring process. Laser-induced breakdown spectroscopy (LIBS) is an ideal candidate technology for this application because sample preparation is minimal and results are available rapidly (seconds to minutes). Here, multivariate regression analysis of LIBS data is used to differentiate the live bacterial pathogens E. coli O157:H7 and S. enterica on various foods (eggshell, milk, bologna, ground beef, chicken, and lettuce) and surfaces (metal drain strainer and cutting board). The type (E. coli or S. enterica) of bacteria could be differentiated in all cases studied along with the metabolic state (viable or heat killed). This study provides data showing the potential of LIBS for the rapid identification of biological contaminants using spectra collected directly from foods and surfaces.

Proof of Principle for a Real-Time Pathogen Isolation Media Diagnostic: The Use of Laser-Induced Breakdown Spectroscopy to Discriminate Bacterial Pathogens and Antimicrobial-Resistant Staphylococcus aureus Strains Grown on Blood Agar

Laser-Induced Breakdown Spectroscopy (LIBS) is a rapid, in situ, diagnostic technique in which light emissions from a laser plasma formed on the sample are used for analysis allowing automated analysis results to be available in seconds to minutes. This speed of analysis coupled with little or no sample preparation makes LIBS an attractive detection tool. In this study, it is demonstrated that LIBS can be utilized to discriminate both the bacterial species and strains of bacterial colonies grown on blood agar. A discrimination algorithm was created based on multivariate regression analysis of spectral data. The algorithm was deployed on a simulated LIBS instrument system to demonstrate discrimination capability using 6 species. Genetically altered Staphylococcus aureus strains grown on BA, including isogenic sets that differed only by the acquisition of mutations that increase fusidic acid or vancomycin resistance, were also discriminated. The algorithm successfully identified all thirteen cultures used in this study in a time period of 2 minutes. This work provides proof of principle for a LIBS instrumentation system that could be developed for the rapid discrimination of bacterial species and strains demonstrating relatively minor genomic alterations using data collected directly from pathogen isolation media.

Detection of pesticides and dioxins in tissue fats and rendering oils using laser-induced breakdown spectroscopy (LIBS)

In laser-induced breakdown spectroscopy (LIBS), a series of powerful laser pulses are directed at a surface to form microplasmas from which light is collected and spectrally analyzed to identify the surface material. In most cases, no sample preparation is needed, and results can be automated and made available within seconds to minutes. Advances in LIBS spectral data analysis using multivariate regression techniques have led to the ability to detect organic chemicals in complex matrices such as foods. Here, the use of LIBS to differentiate samples contaminated with aldrin, 1,2,3,4,6,7,8-heptachlorodibenzo-p-dioxin, chlorpyrifos, and dieldrin in the complex matrices of tissue fats and rendering oils is described. The pesticide concentrations in the samples ranged from 0.005 to 0.1 μg/g. All samples were successfully differentiated from each other and from control samples. Sample concentrations could also be differentiated for all of the pesticides and the dioxin included in this study. The results presented here provide first proof-of-principle data for the ability to create LIBS-based instrumentation for the rapid analysis of pesticide and dioxin contamination in tissue fat and rendered oils.

Laser-Induced Breakdown Spectroscopy: Fundamentals, Applications, and Challenges

Laser-induced breakdown spectroscopy (LIBS) is a technique that provides an accurate in situ quantitative chemical analysis and, thanks to the developments in new spectral processing algorithms in the last decade, has achieved a promising performance as a quantitative chemical analyzer at the atomic level. These possibilities along with the fact that little or no sample preparation is necessary have expanded the application fields of LIBS. In this paper, we review the state of the art of this technique, its fundamentals, algorithms for quantitative analysis or sample classification, future challenges, and new application fields where LIBS can solve real problems.