Natural fluorescence of white blood cells: spectroscopic and imaging study

Deep learning-assisted smartphone-based quantitative microscopy for label-free peripheral blood smear analysis

Hematologists evaluate alterations in blood cell enumeration and morphology to confirm peripheral blood smear findings through manual microscopic examination. However, routine peripheral blood smear analysis is both time-consuming and labor-intensive. Here, we propose using smartphone-based autofluorescence microscopy (Smart-AM) for imaging label-free blood smears at subcellular resolution with automatic hematological analysis. Smart-AM enables rapid and label-free visualization of morphological features of normal and abnormal blood cells (including leukocytes, erythrocytes, and thrombocytes). Moreover, assisted with deep-learning algorithms, this technique can automatically detect and classify different leukocytes with high accuracy, and transform the autofluorescence images into virtual Giemsa-stained images which show clear cellular features. The proposed technique is portable, cost-effective, and user-friendly, making it significant for broad point-of-care applications.

Time-Resolved Fluorescence Spectroscopy of Blood, Plasma and Albumin as a Potential Diagnostic Tool for Acute Inflammation in COVID-19 Pneumonia Patients

Fluorescence lifetime measurements of blood or plasma offer valuable insights into the microenvironment and molecular interactions of fluorophores, particularly concerning albumin. Neutrophil- and hypoxia-induced oxidative stress in COVID-19 pneumonia patients leads to hyperinflammation, various oxidative modifications of blood proteins, and potential alterations in the fluorescence lifetime of tryptophan-containing proteins, especially albumin. The objective of this study was to investigate the efficacy of time-resolved fluorescence spectroscopy of blood and plasma as a prompt diagnostic tool for the early diagnosis and severity assessment of COVID-19-associated pneumonia. This study examined a cohort of sixty COVID-19 patients with respiratory symptoms. To investigate whether oxidative stress is the underlying cause of the change in fluorescence lifetime, human serum albumin was treated with chloramine T. The time-resolved spectrometer Life Spec II (Edinburgh Instruments Ltd., Livingston, UK), equipped with a sub-nanosecond pulsed 280 nm diode, was used to measure the fluorescence lifetime of blood and plasma. The findings revealed a significant reduction in the fluorescence lifetime of blood (diluted 200 times) and plasma (diluted 20 times) at 360 nm in COVID-19 pneumonia patients compared with their respective values recorded six months post-infection and those of healthy individuals. Significant negative correlations were observed between the mean fluorescence lifetime of blood and plasma at 360 nm and several severity biomarkers and advanced oxidation protein products, while a positive correlation was found with albumin and the albumin-globulin ratio. The time-resolved fluorescence spectroscopy method demonstrates the potential to be used as a preliminary screening technique for identifying patients who are at risk of developing severe complications. Furthermore, the small amount of blood required for the measurements has the potential to enable a rapid fingerstick blood test.

Photophysical Mechanisms of Photobiomodulation Therapy as Precision Medicine

Despite a significant focus on the photochemical and photoelectrical mechanisms underlying photobiomodulation (PBM), its complex functions are yet to be fully elucidated. To date, there has been limited attention to the photophysical aspects of PBM. One effect of photobiomodulation relates to the non-visual phototransduction pathway, which involves mechanotransduction and modulation to cytoskeletal structures, biophotonic signaling, and micro-oscillatory cellular interactions. Herein, we propose a number of mechanisms of PBM that do not depend on cytochrome c oxidase. These include the photophysical aspects of PBM and the interactions with biophotons and mechanotransductive processes. These hypotheses are contingent on the effect of light on ion channels and the cytoskeleton, the production of biophotons, and the properties of light and biological molecules. Specifically, the processes we review are supported by the resonant recognition model (RRM). This previous research demonstrated that protein micro-oscillations act as a signature of their function that can be activated by resonant wavelengths of light. We extend this work by exploring the local oscillatory interactions of proteins and light because they may affect global body circuits and could explain the observed effect of PBM on neuro-cortical electroencephalogram (EEG) oscillations. In particular, since dysrhythmic gamma oscillations are associated with neurodegenerative diseases and pain syndromes, including migraine with aura and fibromyalgia, we suggest that transcranial PBM should target diseases where patients are affected by impaired neural oscillations and aberrant brain wave patterns. This review also highlights examples of disorders potentially treatable with precise wavelengths of light by mimicking protein activity in other tissues, such as the liver, with, for example, Crigler-Najjar syndrome and conditions involving the dysregulation of the cytoskeleton. PBM as a novel therapeutic modality may thus behave as "precision medicine" for the treatment of various neurological diseases and other morbidities. The perspectives presented herein offer a new understanding of the photophysical effects of PBM, which is important when considering the relevance of PBM therapy (PBMt) in clinical applications, including the treatment of diseases and the optimization of health outcomes and performance.

Automated Characterisation of Neutrophil Activation Phenotypes in Ex Vivo Human Candida Blood Infections

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Candida bloodstream infections are difficult to diagnose and treat in humans.

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Infection processes give rise to activation of host immune cells.

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Immune cell activation is reflected by characteristic cell morphology.

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Neutrophils exhibit distinct morphodynamics for different Candida species.

Rapid identification of pathogens is required for early diagnosis and treatment of life-threatening bloodstream infections in humans. This requirement is driving the current developments of molecular diagnostic tools identifying pathogens from human whole blood after successful isolation and cultivation. An alternative approach is to determine pathogen-specific signatures from human host immune cells that have been exposed to pathogens. We hypothesise that activated immune cells, such as neutrophils, may exhibit a characteristic behaviour — for instance in terms of their speed, dynamic cell morphology — that allows (i) identifying the type of pathogen indirectly and (ii) providing information on therapeutic efficacy. In this feasibility study, we propose a method for the quantitative assessment of static and morphodynamic features of neutrophils based on label-free time-lapse imaging data. We investigate neutrophil activation phenotypes after confrontation with fungal pathogens and isolation from a human whole-blood assay. In particular, we applied a machine learning supported approach to time-lapse microscopy data from different infection scenarios and were able to distinguish between Candida albicans and C. glabrata infection scenarios with test accuracies well above 75%, and to identify pathogen-free samples with accuracy reaching 100%. These results significantly exceed the test accuracies achieved using state-of-the-art deep neural networks to classify neutrophils by their morphodynamics.

Autofluorescence of blood and its application in biomedical and clinical research

Autofluorescence of blood has been explored as a label free approach for detection of cell types, as well as for diagnosis and detection of infection, cancer, and other diseases. Although blood autofluorescence is used to indicate the presence of several physiological abnormalities with high sensitivity, it often lacks disease specificity due to use of a limited number of fluorophores in the detection of several abnormal conditions. In addition, the measurement of autofluorescence is sensitive to the type of sample, sample preparation, and spectroscopy method used for the measurement. Therefore, while current blood autofluorescence detection approaches may not be suitable for primary clinical diagnosis, it certainly has tremendous potential in developing methods for large scale screening that can identify high risk groups for further diagnosis using highly specific diagnostic tests. This review discusses the source of blood autofluorescence, the role of spectroscopy methods, and various applications that have used autofluorescence of blood, to explore the potential of blood autofluorescence in biomedical research and clinical applications.

Effect of low-dose fast neutrons on the protein components of peripheral blood mononuclear cells of whole-body irradiated Wistar rats

The immune system is exposed to extremely low doses of neutrons under different circumstances, such as through exposure to cosmic rays, nuclear accidents, and neutron therapy. Peripheral blood mononuclear cells (PBMCs) are the primary immune cells that exhibit selective immune responses. Changes in the functions of the protein components of PBMC can be induced by structural modifications of these proteins themselves. Herein, we have investigated the effect of low-dose fast neutrons on PBMC proteins at 0, 2, 4, and 8 days post-whole body irradiation. 64 Wistar rats were used in this study of which, 32 were exposed to fast neutrons at a total dose of 10 mGy (²⁴¹Am-Be, 0.2 mGy/h), and the other 32 were used as controls. Blood samples were drawn, and PBMCs were isolated from whole blood. Fourier transform infrared (FTIR) spectroscopy and fluorescence spectroscopy were used to estimate the changes in the proteins of PBMCs. An alkaline comet assay was performed to assess DNA damage. Hierarchical cluster analysis (HCA) and principal components analysis (PCA) were utilized to discriminate between irradiated and non-irradiated samples. FTIR and fluorescence spectra of the tested samples revealed alterations in the amides and tryptophan, and therefore protein structure at time intervals of 2 and 4 days post-irradiation. No changes were recorded in samples tested at time intervals of 0 and 8 days post-irradiation. The FTIR band intensities of the PBMC proteins of the irradiated samples decreased slightly and were statistically significant. Curve fitting of the amide I band in the FTIR spectra showed changes in the secondary structure of the proteins. At 2 days post-irradiation, fluorescence spectra of the tested samples revealed decreases in the band tryptophan. The comet assay revealed low levels of DNA damage. In conclusion, low-dose fast neutrons can affect the proteins of PBMC.

Cancer cell detection device for the diagnosis of bladder cancer from urine

Bladder cancer is common and has one of the highest recurrence rates. Cystoscopy, the current gold standard diagnosis approach, has recently benefited from the introduction of blue light assisted photodynamic diagnostic (PDD). While blue light cystoscopy improves diagnostic sensitivity, it remains a costly and invasive approach. Here, we present a microfluidic-based platform for non-invasive diagnosis which combines the principle of PDD with whole cell immunocapture technology to detect bladder cancer cells shed in patient urine ex vivo. Initially, we demonstrate with model cell lines that our non-invasive approach achieves highly specific capture rates of bladder cancer cells based on their Epithelial Cell Adhesion Molecule expression (>90%) and detection by the intensity levels of Hexaminolevulinic Acid-induced Protoporphyrin IX fluorescence. Then, we show in a pilot study that the biosensor platform successfully discriminates histopathologically diagnosed cancer patients (n = 10) from non-cancer controls (n = 25). Our platform can support the development of a novel non-invasive diagnostic device for post treatment surveillance in patients with bladder cancer and cancer detection in patients with suspected bladder cancer.

Fluorescence spectral detection of acute lymphoblastic leukemia (ALL) and acute myeloid leukemia (AML): A novel photodiagnosis strategy

Acute lymphoblastic leukemia (ALL) is a cancer of the lymphoid line of blood cell, showing a rapid growth of lymphoblastic immature cells. Acute myeloid leukemia (AML) is a cancer of the myeloid line of blood cells. Early diagnosis is crucial for the effective treatment of these patients. The current standard procedure of diagnosis is extensive blood count analysis, microscopic morphological investigations, bone marrow biopsy and flow-cytometer which are all time- consuming and expensive. Here we demonstrate the advantage a new technique for the diagnosis of ALL and AML based on the fluorescence spectra of blood plasma and RBCs samples from the above patients. Based on the 85 patients analyzed the results reveal that our approach could discriminate the two malignancies unambiguously from the normal with 88 % sensitivity and 80 % specificity. The abnormal decrease in the level of amino acid, tryptophan and coenzyme NADH and abnormal increase in the other amino acid, tyrosine and another coenzyme FAD, (both in comparison to the normal control) act as malignancy indicative biomarkers. Since the contrast parameter between the normal and malignant samples is four- fold, the potential for early detection of leukemia is high. The instrumentation and technique are new and simple; hence may have significant supplementary or complementary value with the existing diagnostic methods.

Label-free characterization of white blood cells using fluorescence lifetime imaging and flow-cytometry: molecular heterogeneity and erythrophagocytosis [Invited]

Blood cell analysis is one of the standard clinical tests. Despite the widespread use of exogenous markers for blood cell quantification, label-free optical methods are still of high demand due to their possibility for in vivo application and signal specific to the biochemical state of the cell provided by native fluorophores. Here we report the results of blood cell characterization using label-free fluorescence imaging techniques and flow-cytometry. Autofluorescence parameters of different cell types - white blood cells, red blood cells, erythrophagocytic cells - are assessed and analyzed in terms of molecular heterogeneity and possibilities of differentiation between different cell types in vitro and in vivo.

In Vivo Reflectance Confocal Microscopy: Emerging Role in Noninvasive Diagnosis and Monitoring of Eczematous Dermatoses

Dermatologic diagnosis and monitoring have been dependent largely on visual grading. A skin biopsy is performed in case of diagnostic uncertainty, but can be traumatic, and results are delayed due to time for specimen transport and processing. Biopsies also destroy specimens, prohibiting lesion evolution monitoring. In vivo reflectance confocal microscopy (RCM) offers a diagnostic alternative to skin biopsy. RCM captures real-time, high-resolution images, and has been piloted for the evaluation of various dermatologic conditions. Identification of unique RCM features may distinguish dermatoses with similar clinical morphologies. Allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) are diagnosed by patch testing that currently uses a subjective scoring system. RCM has increasingly been studied for early detection and severity grading of CD. Common RCM features shared by ACD and ICD are stratum corneum disruption, vesicle formation, exocytosis, spongiosis, and parakeratosis. Features unique to ACD are vasodilation, increased epidermal thickness, intercellular edema, and acanthosis. Features unique to ICD are detached corneocytes and targetoid keratinocytes. This review summarizes the use of RCM in evaluating contact eccematous conditions and aims to spark future research and interest in this promising tool.

Accurate label-free 3-part leukocyte recognition with single cell lens-free imaging flow cytometry

Three-part white blood cell differentials which are key to routine blood workups are typically performed in centralized laboratories on conventional hematology analyzers operated by highly trained staff. With the trend of developing miniaturized blood analysis tool for point-of-need in order to accelerate turnaround times and move routine blood testing away from centralized facilities on the rise, our group has developed a highly miniaturized holographic imaging system for generating lens-free images of white blood cells in suspension. Analysis and classification of its output data, constitutes the final crucial step ensuring appropriate accuracy of the system. In this work, we implement reference holographic images of single white blood cells in suspension, in order to establish an accurate ground truth to increase classification accuracy. We also automate the entire workflow for analyzing the output and demonstrate clear improvement in the accuracy of the 3-part classification. High-dimensional optical and morphological features are extracted from reconstructed digital holograms of single cells using the ground-truth images and advanced machine learning algorithms are investigated and implemented to obtain 99% classification accuracy. Representative features of the three white blood cell subtypes are selected and give comparable results, with a focus on rapid cell recognition and decreased computational cost.

Autofluorescence and Nonspecific Immunofluorescent Labeling in Frozen Bovine Intestinal Tissue Sections: Solutions for Multicolor Immunofluorescence Experiments

Autofluorescent compounds present in intestinal tissue often hinder the ability to utilize multiple, spectrally different, fluorophores. In addition, fixatives and blocking solutions may contribute to background autofluorescence or nonspecific immunofluorescent labeling. During immunofluorescence protocol development, autofluorescent pigments were observed in frozen bovine mid-ileal intestinal tissue sections. Coagulant fixatives, normal serum blocking, histochemical stains Sudan Black B (SBB) and 3,3'-diaminobenzidine (DAB), and spectral separation using imaging software were compared for their ability to reduce autofluorescence, as well as their effect on immunofluorescent labeling. Fluorescent pigments of frozen bovine mid-ileal intestinal tissue sections, most likely caused by eosinophils and lipofuscin, were masked successfully with a combination of DAB and SBB. Little to no statistical differences were observed for all other methods investigated; however, tissue fixed with 1:1 acetone methanol and 10% horse serum diluted in 0.05 M Tris buffer demonstrated lower mean fluorescence intensities. Spectral separation of specific immunofluorescent labeling from background autofluorescence is a simple method for removing unwanted fluorescence; however, successful separation is dependent on tissue and labeling quality.

Sustained and Cost Effective Silver Substrate for Surface Enhanced Raman Spectroscopy Based Biosensing

While surface enhanced Raman spectroscopy (SERS) based biosensing has demonstrated great potential for point-of-care diagnostics in the laboratory, its application in the field is limited by the short life time of commonly used silver based SERS active substrates. In this work, we report our attempt towards SERS based field biosensing, involving the development of a novel sustained and cost-effective substrate composed of silver nanoparticles protected by small nitrogen-doped Graphene Quantum Dots, i.e. Ag NP@N-GQD, and its systematic evaluation for glucose sensing. The new substrate demonstrated significantly stronger Raman enhancement compared to pure silver nanoparticles. More importantly, the new substrate preserved SERS performance in a normal indoor environment for at least 30 days in both the wet and dry states, in contrast to only 10 days for pure silver nanoparticles. The Ag NP@N-GQD thin film in the dry state was then successfully applied as a SERS substrate for glucose detection in mouse blood samples. The new substrate was synthesized under mild experimental conditions, and the cost increase due to N-GQD was negligible. These results suggest that the Ag NP@N-GQD is a cost-effective and sustained SERS substrate, the development of which represents an important step towards SERS based field biosensing.

Evidence of anti-inflammatory effect and percutaneous penetration of a topically applied fish oil preparation: a photoacoustic spectroscopy study

This paper investigates the topical anti-inflammatory effect of a fish oil preparation (FOP) in a croton oil (CO) model of skin inflammation. The photoacoustic spectroscopy (PAS) was applied to estimate the percutaneous penetration of the FOP and as a model to evaluate the topical inflammatory response. After applying CO, the groups of mice received a topical application of a FOP on the left ear. The right ear received the vehicle that was used to dilute the CO. After 6 h, ear tissue was collected to determine the percent inhibition of edema, myeloperoxidase (MPO) activity, and cytokine levels and to perform PAS measurements. Treatment with FOP reduced edema and MPO activity, which was at least partially attributed to a decrease in the levels of tumor necrosis factor, interleukin- 1 ? , interleukin-6, keratinocyte-derived chemokine, and monocyte chemoattractant protein-1. The topically applied FOP penetrated into the tissue and decreased the area of the bands that characterize inflamed tissue. The present results demonstrated the topical anti-inflammatory effect of the FOP. PAS suggests that FOP anti-inflammatory activity is linked with its ability to penetrate through the skin.

Autofluorescence Spectroscopy for Monitoring Metabolism in Animal Cells and Tissues

Excitation of biological substrates with light at a suitable wavelength can give rise to a light emission in the ultraviolet (UV)-visible, near-infrared (IR) spectral range, called autofluorescence (AF). This is a widespread phenomenon, ascribable to the general presence of biomolecules acting as endogenous fluorophores (EFs) in the organisms of the whole life kingdom. In cytochemistry and histochemistry, AF is often an unwanted signal enhancing the background and affecting in particular the detection of low signals or rare positive labeling spots of exogenous markers. Conversely, AF is increasingly considered as a powerful diagnostic tool because of its role as an intrinsic biomarker directly dependent on the nature, amount, and microenvironment of the EFs, in a strict relationship with metabolic processes and structural organization of cells and tissues. As a consequence, AF carries multiple information that can be decrypted by a proper analysis of the overall emission signal, allowing the characterization and monitoring of cell metabolism in situ, in real time and in the absence of perturbation from exogenous markers. In the animal kingdom, AF studies at the cellular level take advantage of the essential presence of NAD(P)H and flavins, primarily acting as coenzymes at multiple steps of common metabolic pathways for energy production, reductive biosynthesis and antioxidant defense. Additional EFs such as vitamin A, porphyrins, lipofuscins, proteins, and neuromediators can be detected in different kinds of cells and bulk tissues, and can be exploited as photophysical biomarkers of specific normal or altered morphofunctional properties, from the retinoid storage in the liver to aging processes, metabolic disorders or cell transformation processes. The AF phenomenon involves all living system, and literature reports numerous investigations and diagnostic applications of AF, taking advantage of continuously developing self-assembled or commercial instrumentation and measuring procedures, making almost impossible to provide their comprehensive description. Therefore a brief summary of the history of AF observations and of the development of measuring systems is provided, along with a description of the most common EFs and their metabolic significance. From our direct experience, examples of AF imaging and microspectrofluorometric procedures performed under a single excitation in the near-UV range for cell and tissue metabolism studies are then reported.

The manifestation of optical centers in UV-Vis absorption and luminescence spectra of white blood human cells

A white blood human cells spectral investigation is presented. The aim of this series of experiments was to obtain and analyze the absorption and luminescence (fluorescence and phosphorescence) spectra at room temperature and at 78 K of newly isolated white blood human cells and their organelles. As a result the optical centers and possible biochemical components that form the studied spectra where identified. Also the differences between the spectra of abnormal cells (B-cell chronic lymphocytic leukemia BCLL) and normal ones were studied for the whole cells and individual organelles.

Endogenous light scattering as an optical signature of circulating tumor cell clusters

Circulating tumor cell clusters (CTCCs) are significantly more likely to form metastases than single tumor cells. We demonstrate the potential of backscatter-based flow cytometry (BSFC) to detect unique light scattering signatures of CTCCs in the blood of mice orthotopically implanted with breast cancer cells and treated with an anti-ADAM8 or a control antibody. Based on scattering detected at 405, 488, and 633 nm from blood samples flowing through microfluidic devices, we identified 14 CTCCs with large scattering peak widths and intensities, whose presence correlated strongly with metastasis. These initial studies demonstrate the potential to detect CTCCs via label-free BSFC.

Autofluorescence spectroscopy and imaging: a tool for biomedical research and diagnosis

Native fluorescence, or autofluorescence (AF), consists in the emission of light in the UV-visible, near-IR spectral range when biological substrates are excited with light at suitable wavelength. This is a well-known phenomenon, and the strict relationship of many endogenous fluorophores with morphofunctional properties of the living systems, influencing their AF emission features, offers an extremely powerful resource for directly monitoring the biological substrate condition. Starting from the last century, the technological progresses in microscopy and spectrofluorometry were convoying attention of the scientific community to this phenomenon. In the future, the interest in the autofluorescence will certainly continue. Current instrumentation and analytical procedures will likely be overcome by the unceasing progress in new devices for AF detection and data interpretation, while a progress is expected in the search and characterization of endogenous fluorophores and their roles as intrinsic biomarkers.

Cytokine reporter mice: the special case of IL-10

IL-10 is one of the key cytokines preventing inflammation-mediated tissue damage. In an attempt to identify IL-10-producing cells in vivo, several groups have recently developed IL-10 reporter mouse strains. Up until now, in total, eight IL-10 reporter strains have been published. This incomparable interest in IL-10 reporter mice emphasizes the importance and difficulties in tracking and subsequently investigating the role of IL-10-producing cells in infectious, inflammatory, autoimmune and cancer diseases. In this review, I summarize and compare the properties of those published IL-10 reporter mouse models. I also discuss the necessity to develop new strategies to generate 'multi-cytokine' reporter mouse models enabling highly sensitive in/ex vivo detection of many cytokines in the same single cell. Such 'multi-cytokine' reporter mice will enable to reconsider the dichotomy 'T-effector versus T-regulatory' paradigm and to provide an accurate revised model for cellular sources of cytokines. Finally, I propose to launch cooperative, international initiatives to promote and coordinate the generation of accurate, combinatorial, reporter mice for every individual murine cytokine.

Comparison of cryotherapy and photodynamic therapy in treatment of oral leukoplakia

Oral leukoplakia is a pre-malignant lesion of the oral mucosa. The aim of this study is to compare the curative effects of photodynamic therapy and cryotherapy in the treatment of oral leukoplakia. The first group, treated by photodynamic therapy (δ-aminolevulinic acid (ALA), 630-635 nm wavelength), consisted of 48 patients suffering from leukoplakia. The second group consisted of 37 patients treated using cryotherapy. Analyses and comparisons of the complete responses, recurrences, numbers of procedures and adverse effects after both PDT and cryotherapy were obtained. In the first group, a complete response was obtained in 35 patients (72.9%), with thirteen recurrences observed (27.1%) over a six-month period. In the second group, a complete response was obtained in 33 patients (89.2%), and recurrence was observed in nine patients (24.3%). Photodynamic therapy and cryotherapy appear to be comparative methods of treatment that may both serve as alternatives for the traditional surgical treatment of oral leukoplakia. The advantages of PDT are connected with minimally invasive and localized character of the treatment and with not damage of collagenous tissue structures, therefore normal cells will repopulate these arrangements. PDT is more convenient for patients, less painful, and more esthetic.

Riboflavin mobilization from eleocyte stores in the earthworm Dendrodrilus rubidus inhabiting aerially-contaminated Ni smelter soil

A 6-week reciprocal transfer laboratory exposure experiment was conducted with two populations of the epigeic earthworm Dendrodrilus rubidus; one population inhabited a site approx. 200 m downwind of an active Ni smelter co-contaminated with Ni and Cu (3648 and 977 microg g(-1)d.w., respectively), the other inhabited uncontaminated soil. Worms transferred from unpolluted to Ni/Cu-polluted soil lost body mass (62%); they also had reduced (70%) total coelomocyte number, including autofluorescent eleocytes, and had significantly decreased (92%) riboflavin-derived fluorescence emission measured at 525 nm. Coelomocyte counts were low, and 525 nm emission was negligible in worms maintained on their native Ni/Cu soil. Earthworms and their coelomocytes were unaffected when transferred from Ni/Cu-polluted soil to unpolluted soil. In conclusion, exposing worms to stress-inducing factors, including metal pollution, alters the riboflavin status within the immune-competent cells of D. rubidus, but it requires further in vivo studies to establish whether the reduction in the fluorescence signal is predominantly due to depletion of riboflavin-containing eleocytes, or to riboflavin quenching, or to enzymatic conversion (and thus depletion) of stored riboflavin into its functional immune-potentiating flavin derivatives, FMN and FAD. The flavin budget of D. rubidus coelomocytes recovered by a reproducible extrusion procedure is a potentially useful biomarker for assessing sublethal stress in this early colonizer of disturbed soils.

Differentiation of malignant B-lymphoma cells from normal and activated T-cell populations by their intrinsic autofluorescence

Patients with active posterior and intermediate uveitis have inflammatory cells in their vitreous; those with primary intraocular lymphoma have malignant B-lymphoma cells concomitantly. These cell types cannot be distinguished clinically. The goal of this study was to investigate intrinsic autofluorescence as a noninvasive way of differentiating immune and lymphomatous cell populations. Human primary T cells were stimulated with or without anti-CD3 plus anti-CD28 stimulation. B-lymphoma cells (CA46) were cultured separately. Five experimental groups were prepared: unstimulated T cells, stimulated T cells, CA46 cells, and stimulated T cells mixed with CA46 cells at a ratio of 1:3 or mixed at a ratio of 3:1. Samples were excited with three wavelengths and imaged with a confocal microscope. For each condition, the autofluorescent emissions from the sample were measured. In separate experiments, T cells or CA46 cells were injected into the anterior chamber of a BALB/c mouse eye and autofluorescence was measured. Pure T-cell and lymphoma populations were clearly distinguishable based on autofluorescence intensity spectra. CA46 cells were the least fluorescent when excited with 351-nm light, but most fluorescent when excited with longer wavelengths like 488 nm. Mixed populations of T cells and CA46 cells had emission intensities that fell predictably in between those of the pure populations. An ex vivo study showed that CA46 cells could be detected based on their intrinsic autofluorescence. Our studies showed that normal activated and malignant lymphocyte populations can be distinguished based on their intrinsic autofluorescent properties. Future work with in vivo models may prove useful in facilitating the diagnosis of uveitis and other ocular diseases.

Multispectral imaging autofluorescence microscopy in colonic and gastric cancer metastatic lymph nodes

BACKGROUND & AIMS

The lymphadenectomy and extended lymphadenectomy procedures have been points of controversy in surgical oncology. The methods available for the detection of metastatic lymph nodes are numerous. These include lymphoscintigraphy and radiolabeled antibody detection, but in most cancers the currently used technique is sentinel lymph node identification, performed primarily through the use of immunohistochemistry. We propose the application of autofluorescence (AF)-based techniques for lymph node evaluation in colorectal and gastric tumors.

METHODS

We studied 30 clinical cases: 15 colorectal cancers and 15 gastric cancers. All of the patients were in the advanced stages of the disease and were candidates for adjuvant therapy. Autofluorescence microspectroscopy and multispectral imaging autofluorescence microscopy have been used to analyze the AF emission of metastatic lymph node sections, excited with 365-nm wavelength radiation. The AF spectra were recorded in the range of 400-700 nm. Monochrome AF images were acquired sequentially through interference filters peaked at 450, 550, and 650 nm, and then combined together in a single red-green-blue image. The AF pattern and the emission spectrum of metastatic lymph nodes have unique characteristics that can be used to distinguish them from the normal ones.

RESULTS

The results, compared with standard histopathologic procedures and with specific staining methods, supplied a satisfactory validation of the proposed technique, revealing the possibility of improving the actual diagnostic procedures for malignant lymph node alterations.

CONCLUSIONS

With the development of appropriate instrumentation, the proposed technique could be particularly suitable in intrasurgical diagnosis of metastatic lymph nodes.

Synchronous fluorescence spectroscopic characterization of DMBA-TPA-induced squamous cell carcinoma in mice

While initially confined to the epidermis, squamous cell carcinoma can eventually penetrate into the underlying tissue if not diagnosed early and treated. The noninvasive early detection of the carcinoma is important to achieve a complete treatment of the disease. Of the various non-invasive optical techniques, the synchronous fluorescence (SF) technique is considered to provide a simplified spectral profile with more sharp spectral signatures of the endogenous fluorophores in complex systems. The potential use of the SF technique in the characterization of the sequential tissue transformation in 7,12-dimethylbenz(a)anthracene-12-O-tetradecanoylphorbol-13-acetate (DMBA-TPA)-induced mouse skin tumor model in conjunction with simple statistical analysis is explored. The SF spectra show distinct differences during the earlier weeks of the tumor-induction period. Intensity ratio variables are calculated and used in three discriminant analyses. All the discriminant analyses show better classification results with accuracy greater than 80%. From the observed differences in the spectral characteristics and the ratio variables that resulted in better classification between groups, it is concluded that tryptophan, collagen, and NADH are the key fluorophores that undergo changes during tissue transformation process and hence they can be targeted as tumor markers to diagnose normal from abnormal tissues using the SF technique.

Cytokine expression in healthy and inflamed mucosa: probing the role of eosinophils in the digestive tract

BACKGROUND

In eosinophilic esophagitis (EE), the esophagus is infiltrated with activated eosinophils that often evoke tissue damage, but the intestines of these patients remain unaffected. We thus hypothesized that different tissue-dwelling eosinophil populations may coexist: activated eosinophils that infiltrate the esophagus and resting eosinophils that reside in unaffected intestines. We sought to characterize different eosinophil subpopulations by comparing the expression of certain proinflammatory proteins in tissue-dwelling eosinophils at different parts of the gastrointestinal tract.

METHODS

The 8 patients participating included 6 men and 2 women with a previously confirmed diagnosis of EE, whose average age was 39.4 years (range, 20-55 yr) and average disease duration was 13.6 years (range, 2-26 yr). Controls were 3 men and 1 woman, with a mean age of 43.3 years (range, 29-56 yr) with untreated functional dyspepsia who underwent diagnostic esophagogastroduodenoscopy. Six additional individuals having normal blood eosinophils were recruited for cytokine measurements in blood eosinophils. Immunofluorescence and immunoassays charted expression of CD25 and the TH2 cytokines, interleukin (IL)-4, IL-5, IL-10, and IL-13, in esophageal, intestinal, and blood eosinophils from controls and patients.

RESULTS

Controls showed a small but significant proportion of intestinal, but no blood, eosinophils expressing CD25 and IL-13, suggesting physiologic activation occurring in the digestive tract. On the other hand, eosinophils infiltrating the inflamed esophageal mucosa of patients with EE showed strong evidence of activation, with most expressing CD25, IL-4, and IL-13. Moreover, IL-13-positive intestinal eosinophils were increased in patients compared with controls.

CONCLUSIONS

We thus conclude that tissue-dwelling eosinophils show different and distinct cytokine expression patterns under noninflammatory and inflammatory conditions.

Non-invasive evaluation of the kinetics of allergic and irritant contact dermatitis

Reflectance confocal microscopy (RCM) allows non-invasive visualization of human skin in vivo. It has been used to describe the histopathological features of acute contact dermatitis (CD). This work was designed to investigate the kinetics of both allergic and irritant CD (ACD and ICD) in vivo. Eighteen subjects with a prior diagnosis of ACD were patch tested with the specific allergen sodium lauryl sulfate as an irritant, and appropriate controls. RCM, transepidermal water loss (TEWL), and fluorescence excitation spectroscopy (FES) were performed at several time points within 2 wk after patch removal. After removal of the Finn chambers at 48 h, superficial epidermal changes, primarily involving the stratum corneum, and increased epidermal thickness were mainly present in ICD. ACD, on the other hand, showed microvesicle formation peaking at 96 h following patch removal. Both ACD and ICD showed exocytosis and similar degrees of spongiosis on RCM. TEWL and FES demonstrated a significant difference between ACD and ICD. RCM, TEWL, and FES are valuable non-invasive tools to quantitatively study the kinetics of the pathophysiology of acute CD reactions in vivo and monitor the changes at a cellular level.

Cell and tissue autofluorescence research and diagnostic applications

Cells contain molecules, which become fluorescent when excited by UV/Vis radiation of suitable wavelength. This fluorescence emission, arising from endogenous fluorophores, is an intrinsic property of cells and is called auto-fluorescence to be distinguished from fluorescent signals obtained by adding exogenous markers. The majority of cell auto-fluorescence originates from mitochondria and lysosomes. Together with aromatic amino acids and lipo-pigments, the most important endogenous fluorophores are pyridinic (NADPH) and flavin coenzymes. In tissues, the extracellular matrix often contributes to the auto-fluorescence emission more than the cellular component, because collagen and elastin have, among the endogenous fluorophores, a relatively high quantum yield. Changes occurring in the cell and tissue state during physiological and/or pathological processes result in modifications of the amount and distribution of endogenous fluorophores and chemical-physical properties of their microenvironment. Therefore, analytical techniques based on auto-fluorescence monitoring can be utilized in order to obtain information about morphological and physiological state of cells and tissues. Moreover, auto-fluorescence analysis can be performed in real time because it does not require any treatment of fixing or staining of the specimens. In the past few years spectroscopic and imaging techniques have been developed for many different applications both in basic research and diagnostics.

Native fluorescence spectroscopy of blood plasma in the characterization of oral malignancy

Native fluorescence characteristics of blood plasma were studied in the visible spectral region, at two different excitation wavelengths, 405 and 420 nm, to discriminate patients with different stages of oral malignancy from healthy subjects. The fluorescence spectra of blood plasma of oral malignant subjects exhibit characteristic spectral differences with respect to normal subjects. Different ratios were calculated using the fluorescence intensity values at those emission wavelengths that give characteristic spectral features of each group of experimental subjects studied. These fluorescence intensity ratios were used as input variables for a multiple linear discriminant analysis across different groups. Leave-one out cross-validation was used to check the reliability of each discriminant analysis performed. The discriminant analysis performed across normal and oral cancerous subjects classified 94.7% of the original grouped cases and 93.7% of the cross-validated grouped cases. A classification algorithm was developed on the basis of the score of the discriminant functions (discriminant score) resulted in the analyses. The diagnostic potentiality of the present technique was also estimated in the discrimination of malignant subjects from normal and nonmalignant diseased subjects such as liver diseases. In the discriminant analysis performed across the three groups, normal, oral malignancy (including early and advanced stages) and liver diseases, 99% of the original grouped cases and 95.9% of the cross-validated grouped cases were correctly classified. Similar analysis performed across normal, early stage of oral malignancy, advanced oral malignancy and liver diseases correctly classified 94.9% of the original grouped cases and 91.8% of the cross-validated grouped cases.

Photodynamic therapy (PDT) using topically applied delta-aminolevulinic acid (ALA) for the treatment of oral leukoplakia

BACKGROUND

Photodynamic therapy (PDT) is a non-invasive method for topical and selective treatment of pre-malignant lesions of oral cavity. The aim of our study was to determine therapeutic response to PDT in patients with oral leukoplakia.

METHODS

Twelve patients participated in our study. Lesions affected a variety of intraoral sites. The most common location was buccal, gingival and mandibular mucosa. Patients were treated with topically applied 10% delta-aminolevulinic acid (ALA) and light from an argon-pumped dye laser. Irradiation was performed in several (6-8) sessions using light at 635 nm wavelength, delivering a total dose of 100 J/cm2 per session.

RESULTS

A complete response was obtained in 10 out of 12 treated patients. One recurrence was observed during 6 months.

CONCLUSION

Photodynamic therapy appears to be a feasible alternative to conventional therapy of pre-malignant lesions of oral cavity.

Fluorescence excitation spectroscopy provides information about human skin in vivo

Fluorescence spectroscopy of human skin has the potential to provide useful morphologic and biochemical information. The endogenous fluorescence of human skin has been investigated in vivo on normal human volunteers as well as on patients with psoriasis and it was found that characteristic bands can be identified in the fluorescence spectra that are associated with specific skin fluorophores. One epidermal band (295 nm excitation, attributed to tryptophan) and two dermal bands (335 and 370 nm excitation, attributed to collagen cross-links) were consistently present in all fluorescence spectra. In addition, the fluorescence spectra obtained from lesions and nonlesional sites of psoriatic patients differed from those obtained from healthy volunteers and the hyperproliferative state of the lesions was characterized by a significantly larger signal at 295 nm excitation. These results indicate that fluorescence spectroscopy is a promising technique for the investigation of human skin in vivo.

Endogenous skin fluorescence is a good marker for objective evaluation of comedolysis

OBJECTIVE

evaluation of comedone lesions, especially in vivo, remains a challenge. We have used the rhino mouse model in combination with topical application of all-trans retinoic acid as a comedolytic agent, to investigate the potential of fluorescence spectroscopy as a noninvasive technique in the assessment of noninflammatory acne. The results indicate that there is a strong correlation between the fluorescence excitation spectral features assessed in vivo, and the histologic changes identified, particularly the size of the utriculi as well as the dermal and epidermal thickness. We conclude that fluorescence excitation spectroscopy represents a promising novel and useful tool in the quantitative evaluation of the pseudocomedones and could also be used for the rapid and noninvasive assessment of comedolysis induced by the application of pharmacologic agents such as retinoids.

Fluorescence in situ hybridization (FISH) for direct visualization of microorganisms

As a technique allowing simultaneous visualization, identification, enumeration and localization of individual microbial cells, fluorescence in situ hybridization (FISH) is useful for many applications in all fields of microbiology. FISH not only allows the detection of culturable microorganisms, but also of yet-to-be cultured (so-called unculturable) organisms, and can therefore help in understanding complex microbial communities. In this review, methodological aspects, as well as problems and pitfalls of FISH are discussed in an examination of past, present and future applications.

Multispectral imaging autofluorescence microscopy for the analysis of lymph-node tissues

Although histochemical and immunohistochemical methods are the standard procedures in diagnosis of lymphoproliferative disorders, useful improvements in evidencing histopathologic manifestations can be obtained with the introduction of tissue autofluorescence analyses. We used microspectrofluorometry and a Multispectral Imaging Autofluorescence Microscopy (MIAM) technique to analyze lymph-node biopsies from patients with lymphoadenopathy of different origins. Images of tissue autofluorescence were obtained by excitation at 365 nm of lymph-node sections and sequential detection with interference filters (50 nm bandwidth) peaked at 450, 550 and 658 nm. Monochrome images were combined together in a single red-green-blue color image. Most of the fluorescence was observed within the blue spectral band because of large contributions from extracellular collagen and elastin fibers as well as from reduced form of intracellular nicotinamide adenine dinucleotide (phosphate). Autofluorescence imaging shows morphological differences between neoplastic and non-neoplastic tissues. The reactive hyperplasia samples show the typical lymph-node organization with weak fluorescent follicles separated by high fluorescent connective trabeculae. In the neoplastic lymph nodes the loss of follicle organization is observed. Consequently, MIAM permits to discriminate between non-neoplastic and neoplastic tissues on the basis of their autofluorescence pattern. Multispectral imaging of tissue autofluorescence may present some advantages with respect to standard histochemical microscopy since it (1) does not require any chemical manipulation of samples; (2) gives real-time results performing the analysis immediately upon specimen resection; and (3) supplies a representation of the biological structure organization linked to endogenous fluorophores.