A pilot study on fingerprinting Leishmania species from the Old World using Fourier transform infrared spectroscopy

Synchrotron-Infrared Microspectroscopy of Live Leishmania major Infected Macrophages and Isolated Promastigotes and Amastigotes

The prevalence of neglected tropical diseases (NTDs) is advancing at an alarming rate. The NTD leishmaniasis is now endemic in over 90 tropical and sub-tropical low socioeconomic countries. Current diagnosis for this disease involves serological assessment of infected tissue by either light microscopy, antibody tests, or culturing with in vitro or in vivo animal inoculation. Furthermore, co-infection by other pathogens can make it difficult to accurately determine Leishmania infection with light microscopy. Herein, for the first time, we demonstrate the potential of combining synchrotron Fourier-transform infrared (FTIR) microspectroscopy with powerful discrimination tools, such as partial least squares-discriminant analysis (PLS-DA), support vector machine-discriminant analysis (SVM-DA), and k-nearest neighbors (KNN), to characterize the parasitic forms of Leishmania major both isolated and within infected macrophages. For measurements performed on functional infected and uninfected macrophages in physiological solutions, the sensitivities from PLS-DA, SVM-DA, and KNN classification methods were found to be 0.923, 0.981, and 0.989, while the specificities were 0.897, 1.00, and 0.975, respectively. Cross-validated PLS-DA models on live amastigotes and promastigotes showed a sensitivity and specificity of 0.98 in the lipid region, while a specificity and sensitivity of 1.00 was achieved in the fingerprint region. The study demonstrates the potential of the FTIR technique to identify unique diagnostic bands and utilize them to generate machine learning models to predict Leishmania infection. For the first time, we examine the potential of infrared spectroscopy to study the molecular structure of parasitic forms in their native aqueous functional state, laying the groundwork for future clinical studies using more portable devices.

Mitigation of graphene oxide toxicity in C. elegans after chemical degradation with sodium hypochlorite

Graphene oxide (GO) is a promising and strategic carbon-based nanomaterial for innovative and disruptive technologies. It is therefore essential to address its environmental health and safety aspects. In this work, we evaluated the chemical degradation of graphene oxide by sodium hypochlorite (NaClO, bleach water) and its consequences over toxicity, on the nematode Caenorhabditis elegans. The morphological, chemical, and structural properties of GO and its degraded product, termed NaClO-GO, were characterized, exploring an integrated approach. After the chemical degradation of GO at room temperature, its flake size was reduced from 156 to 29 nm, while NaClO-GO showed changes in UV-vis absorption, and an increase in the amount of oxygenated surface groups, which dramatically improved its colloidal stability in moderately hard reconstituted water (EPA medium). Acute and chronic exposure endpoints (survival, growth, fertility, and reproduction) were monitored to evaluate material toxicities. NaClO-GO presented lower toxicity at all endpoints. For example, an increase of over 100% in nematode survival was verified for the degraded material when compared to GO at 10 mg L^-1. Additionally, enhanced dark-field hyperspectral microscopy confirmed the oral uptake of both materials by C. elegans. Finally, this work represents a new contribution toward a better understanding of the links between the transformation of graphene-based materials and nanotoxicity effects (mitigation), which is mandatory for the safety improvements that are required to maximize nanotechnological benefits to society.

Infrared Spectroscopy of Blood

The magnitude of infectious diseases in the twenty-first century created an urgent need for point-of-care diagnostics. Critical shortages in reagents and testing kits have had a large impact on the ability to test patients with a suspected parasitic, bacteria, fungal, and viral infections. New point-of-care tests need to be highly sensitive, specific, and easy to use and provide results in rapid time. Infrared spectroscopy, coupled to multivariate and machine learning algorithms, has the potential to meet this unmet demand requiring minimal sample preparation to detect both pathogenic infectious agents and chronic disease markers in blood. This focal point article will highlight the application of Fourier transform infrared spectroscopy to detect disease markers in blood focusing principally on parasites, bacteria, viruses, cancer markers, and important analytes indicative of disease. Methodologies and state-of-the-art approaches will be reported and potential confounding variables in blood analysis identified. The article provides an up to date review of the literature on blood diagnosis using infrared spectroscopy highlighting the recent advances in this burgeoning field.

Discrimination of bacteria using whole organism fingerprinting: the utility of modern physicochemical techniques for bacterial typing

This review compares and contrasts MALDI-MS, FT-IR spectroscopy and Raman spectroscopy for whole organism fingerprinting and bacterial typing.

Compressed FTIR spectroscopy using low-rank matrix reconstruction

Fourier transform infrared (FTIR) spectroscopy is a powerful technique in analytical chemistry. Typically, spatially distributed spectra of the substance of interest are conducted simultaneously using FTIR spectrometers equipped with array detectors. Scanning-based methods such as near-field FTIR spectroscopy, on the other hand, are a promising alternative providing higher spatial resolution. However, serial recording severely limits their application due to the long acquisition times involved and the resulting stability issues. We demonstrate that it is possible to significantly reduce the measurement time of scanning methods by applying the mathematical technique of low-rank matrix reconstruction. Data from a previous pilot study of Leishmania strains are analyzed by randomly selecting 5% of the interferometer samples. The results obtained for bioanalytical fingerprinting using the proposed approach are shown to be essentially the same as those obtained from the full set of data. This finding can significantly foster the practical applicability of high-resolution serial scanning techniques in analytical chemistry and is also expected to improve other applications of FTIR spectroscopy and spectromicroscopy.

Lactococcus lactis expressing sand fly PpSP15 salivary protein confers long-term protection against Leishmania major in BALB/c mice

Cutaneous leishmaniasisis a vector-borne disease transmitted by Leishmania infected sand flies. PpSP15 is an immunogenic salivary protein from the sand fly Phlebotomus papatasi. Immunization with PpSP15 was shown to protect against Leishmania major infection. Lactococcus lactis is a safe non-pathogenic delivery system that can be used to express antigens in situ. Here, the codon-optimized Ppsp15-egfp gene was cloned in pNZ8121 vector downstream of the PrtP signal peptide that is responsible for expression and secretion of the protein on the cell wall. Expression of PpSP15-EGFP recombinant protein was monitored by immunofluorescence, flow cytometry and Western blot. Also, expression of protein in cell wall compartment was verified using whole cell ELISA, Western blot and TEM microscopy. BALB/c mice were immunized three times with recombinant L. lactis-PpSP15-EGFPcwa, and the immune responses were followed up, at short-term (ST, 2 weeks) and long-term (LT, 6 months) periods. BALB/c mice were challenged with L. major plus P. papatasi Salivary Gland Homogenate. Evaluation of footpad thickness and parasite burden showed a delay in the development of the disease and significantly decreased parasite numbers in PpSP15 vaccinated animals as compared to control group. In addition, immunized mice showed Th1 type immune responses. Importantly, immunization with L. lactis-PpSP15-EGFPcwa stimulated the long-term memory in mice which lasted for at least 6 months.

Evaluating the biochemical changes of LPS-stimulated endothelial cells by synchrotron FTIR microspectroscopy at a single-cell level

Endothelial damage is a major manifestation in many forms of heart and lung injuries induced by lipopolysaccharide (LPS), but the biochemical responses and activation mechanisms of endothelial cells have not been fully explicit. In this study, the biochemical changes to endothelial cells exposed to LPS were investigated by synchrotron FTIR microspectroscopy at a single-cell level. We found that the whole infrared spectrum of endothelial cells shifted after LPS treatment, indicating chemical component changes within cells. Principal component analysis (PCA) and t tests on subspectra (fatty acid region, protein region, and nucleic acid-sugar region, respectively) further showed that sugar components as well as fatty acids changed dramatically while proteins had no significant variation following LPS exposure. These results suggested that the glycocalyx layer structure on endothelial cell membrane may be mainly influenced by LPS and also proved that synchrotron FTIR microspectroscopy was a useful technique to evaluate the biochemical changes of endothelial damage at the single-cell level. Graphical abstract.

Compressed sensing FTIR nano-spectroscopy and nano-imaging

Infrared scattering scanning near-field optical microscopy (IR s-SNOM) provides for spectroscopic imaging with nanometer spatial resolution, yet full spatio-spectral imaging is constrained by long measurement times. Here, we demonstrate the application of compressed sensing algorithms to achieve hyperspectral FTIR-based nano-imaging at an order of magnitude faster imaging speed to achieve the same spectral content compared to conventional approaches. At the example of the spectroscopy of a single vibrational resonance, we discuss the relationship of prior knowledge of sparseness of the employed Fourier base functions and sub-sampling. Compressed sensing nano-FTIR spectroscopy promises both rapid and sensitive chemical nano-imaging which is highly relevant in academic and industrial settings for fundamental and applied nano- and bio-materials research.