Mapping of the total fluorescence of human blood serum as a new method for its characterization

Integrating time since deposition estimation of bloodstains into a DNA profiling workflow: A novel approach using fluorescence spectroscopy

Determining the time since deposition (TSD) of bloodstains is important to establish a timeline of bloodshed, while DNA profiling addresses identity (source attribution). Traditionally treated as separate processes, this study integrates TSD estimation into routine DNA profiling by analyzing typically discarded cell lysate (eluates) from spin-column-based DNA extractions. Fluorescence spectroscopy was used to analyze eluates from bloodstains deposited up to 99 weeks. Two excitation-emission matrices (EEMs) were acquired for each sample and deconvoluted using parallel factor analysis (PARAFAC) to identify individual fluorophores. For example, tryptophan demonstrated a time-dependent decrease in fluorescence. Additionally, we observed an accumulation of fluorescent oxidation products (FOX) and advanced glycation end products (AGEs) over TSD. An untargeted metabolomics high-performance liquid chromatography-mass spectrometry workflow was applied to assist with fluorophore identification. Chemometric models were used to estimate TSD from EEM fluorescence data. Boruta feature selection coupled with random forest regression outperformed all other models and achieved high accuracy, with an R2 of 0.993 and root mean square error of prediction (RMSEP) of 2.83 weeks for the full 99-week period, and an R2 of 0.987 and RMSEP of 2.06 weeks for the 1-year timeframe. Comparisons were also made between anticoagulant-free (AC-free) and anticoagulant-treated (AC-treated) bloodstains deposited up to 3 months. We noted differences in fluorescence based on AC treatment, with AC-free blood exhibiting higher FOX and lower AGE fluorescence than AC-treated blood. Our findings demonstrate the effectiveness and feasibility of integrating TSD estimation into routine forensic DNA extractions while maintaining high prediction accuracies.

Discrimination between Covid-19 positive and negative blood serum based on excitation-emission matrix fluorescence spectroscopy and chemometrics

The outbreak of the disease caused by the SARS-CoV-2 virus (Covid-19) has resulted in a global health emergency that has caused millions of deaths in recent years. The control of the pandemic was significantly impacted by the availability of inputs and qualified labor to correctly diagnose the population. The challenges faced by numerous countries in conducting this extensive diagnosis, utilizing methods such as RT-PCR, emphasize the necessity for alternative testing strategies that are less reliant on expensive raw materials and can be implemented on a larger scale. This paper proposes a methodology for classifying blood serum samples as either positive or negative for Covid-19 infection using excitation-emission matrix (EEM) fluorescence spectroscopy associated with multivariate analysis. The proposed methodology uses EEM spectra of samples diagnosed by the reference method (RT-PCR) to train and validate classification models. Two approaches were tested: the first using PARAFAC and the second by unfolding the excitation-emission matrices. The DD-SIMCA model performed best in the PARAFAC approach, with an error rate of 0.05, sensitivity of 0.98 and specificity of 0.96. The PLS-DA and PCA-DA models in the second approach effectively distinguished between classes. The PCA-DA model performed the best with an error rate of 0.06 and sensitivity and specificity of 0.94. Fluorescence spectroscopy was found to be effective in analyzing serum samples and obtaining discrimination models to determine if a patient is infected with SARS-CoV-2. The findings are encouraging and could aid in the development of an inexpensive and reliable auxiliary diagnostic method.

Elevated antibody binding to striatal cholinergic interneurons in patients with pediatric acute-onset neuropsychiatric syndrome

Pediatric Acute-onset Neuropsychiatric Syndrome (PANS) is characterized by the abrupt onset of significant obsessive-compulsive symptoms (OCS) and/or severe food restriction, together with other neuropsychiatric manifestations. An autoimmune pathogenesis triggered by infection has been proposed for at least a subset of PANS. The older diagnosis of Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcus (PANDAS) describes rapid onset of OCD and/or tics associated with infection with Group A Streptococcus. The pathophysiology of PANS and PANDAS remains incompletely understood. We recently found serum antibodies from children with rigorously defined PANDAS to selectively bind to cholinergic interneurons (CINs) in the striatum. Here we examine this binding in children with relapsing and remitting PANS, a more heterogeneous condition, collected in a distinct clinical context from those examined in our previous work, from children with a clinical history of Streptococcus infection. IgG from PANS cases showed elevated binding to striatal CINs in both mouse and human brain. Patient plasma collected during symptom flare decreased a molecular marker of CIN activity, phospho-riboprotein S6, in ex vivo brain slices; control plasma did not. Neither elevated antibody binding to CINs nor diminished CIN activity was seen with plasma collected from the same children during remission. These findings replicate what we have seen previously in PANDAS and support the hypothesis that at least a subset of PANS cases have a neuroimmune pathogenesis. Given the critical role of CINs in modulating basal ganglia function, these findings confirm striatal CINs as a locus of interest in the pathophysiology of both PANS and PANDAS.

Microfluidic antibody affinity profiling of alloantibody-HLA interactions in human serum

Antibody profiling is a fundamental component of understanding the humoral response in a wide range of disease areas. Most currently used approaches operate by capturing antibodies onto functionalised surfaces. Such measurements of surface binding are governed by an overall antibody titre, while the two fundamental molecular parameters, antibody affinity and antibody concentration, are challenging to determine individually from such approaches. Here, by applying microfluidic diffusional sizing (MDS), we show how we can overcome this challenge and demonstrate reliable quantification of alloantibody binding affinity and concentration of alloantibodies binding to Human Leukocyte Antigens (HLA), an extensively used clinical biomarker in organ transplantation, both in buffer and in crude human serum. Capitalising on the ability to vary both serum and HLA concentrations during MDS, we show that both affinity and concentration of HLA-specific antibodies can be determined directly in serum when neither of these parameters is known. Finally, we provide proof of principle in clinical transplant patient sera that our assay enables differentiation of alloantibody reactivity against HLA proteins of highly similar structure, providing information not attainable through currently available techniques. These results outline a path towards detection and in-depth profiling of humoral immunity and may enable further insights into the clinical relevance of antibody reactivity in clinical transplantation and beyond.

Specific fluorescent signatures for body fluid identification using fluorescence spectroscopy

Non-invasive, rapid, on-site detection and identification of body fluids is highly desired in forensic investigations. The use of fluorescence-based methods for body fluid identification, have so far remain relatively unexplored. As such, the fluorescent properties of semen, serum, urine, saliva and fingermarks over time were investigated, by means of fluorescence spectroscopy, to identify specific fluorescent signatures for body fluid identification. The samples were excited at 81 different excitation wavelengths ranging from 200 to 600 nm and for each excitation wavelength the emission was recorded between 220 and 700 nm. Subsequently, the total emitted fluorescence intensities of specific fluorescent signatures in the UV-visible range were summed and principal component analysis was performed to cluster the body fluids. Three combinations of four principal components allowed specific clustering of the body fluids, except for fingermarks. Blind testing showed that 71.4% of the unknown samples could be correctly identified. This pilot study shows that the fluorescent behavior of ageing body fluids can be used as a new non-invasive tool for body fluid identification, which can improve the current guidelines for the detection of body fluids in forensic practice and provide the robustness of methods that rely on fluorescence.

Performance of feature extraction method for classification and identification of proteins based on three-dimensional fluorescence spectrometry

Three-dimensional excitation emission matrix (EEM) fluorescence spectroscopy was employed to discriminate protein samples comprising bovine serum albumin, neurotensin, ovalbumin, ricin, trypsin from bovine pancreas and trypsin from porcine pancreas. Two methods of feature extraction with and without parameterization were applied to the spectral data in order to evaluate their performance of discrimination between protein samples. The discrimination of protein samples was conducted by k-means clustering algorithm and eigenvalue extracting procedure based on principal component analysis (PCA). It was found that the method of feature extraction without parameterization performed best, correctly attributing 100% of the spectral data in the condition of two principal components (PCs) captured. Features extracted with spectral parameterization failed to separate ricin and trypsin from bovine pancreas in same condition. Without spectral parameterization, less dimensionality and unique principal components captured by PCA indicates the spectrally-resolved features of corresponding protein samples. By clustering using each spectrum at fixed excitation wavelength, excitation wavelengths matched with common intrinsic fluorophores were found to be more sensitive to the classification accuracy. Contributions of spectral features extracted from EEM to the principal components were discussed and demonstrated their feature differentiation capabilities among six protein samples. These results reveal that appropriate extraction approach of features in combination with PCA analysis could be used in discrimination of protein samples at species level as a spectroscopic diagnostic tool. Our study provides fundamental references about computational strategies when EEM are used to explore proteins in ambient environment.

Enhanced chemodiversity, distinctive molecular signature and diurnal dynamics of dissolved organic matter in streams of two headwater catchments, Southeastern China

Dissolved organic matter (DOM) is a complicated assembly of organic molecules, including thousands of molecules with various structures and properties. However, how the stream DOM sources respond to carbon compositions and the transformation processes remains unclear. In this study, the chemical characteristics and spectral and mass spectrometry (FT-ICR MS) of DOM were analyzed. Six sampling points of headwater stream (HWSs) were sampled, and an effluent polluted stream (WSR) and a main stream of the Changjiang River (DT) were also sampled for comparison. In situ degradation experiments and FT-ICR MS analysis were also performed to observe the dynamic processes of DOM in HWS. The results showed that the anthropogenic markers of sewage (i.e. sulfur (S) compounds and marker from antibiotics and estrogen) in HWS were higher than those in DT. The molecular weight decreased while the degradation products (S-containing compounds and unsaturated compounds (HU)) increased after in situ degradation due to the influence of both the photodegradation and biodegradation process. In addition, the KMD plots showed that the DOM homologue intensities in range 400-600 Da changed significantly after demethylation by biodegradation. The components of highly refractory substances and the degradation degree of DOM in DT was higher than that in HWS. We extracted the refractory DOM pool in HWS, which was mainly small molecular with molecular weights < 600 Da. These molecular will be difficult to remove in traditional drinking water treatment processes and easily produced disinfection byproducts (DBPs). This study emphasized the necessity of identifying the sources and transformation processes of DOM in HWS and clarified the types and characteristics of DOM that should be considered in future drinking water treatment.

Multifaceted Interaction Studies between Carbon Dots and Proteins of Clinical Importance for Optical Sensing Signals

Carbon dots (CDs) are emerging as efficient optical probes. However, their application potential for clinical diagnosis has not been adequately explored. Herein, we examined the suitability of pyroglutamate CDs for detecting glucose, cholesterol, and alcohol in blood serum through their peroxidative activity in the respective enzyme-catalyzed reactions following fluorometric and colorimetric approaches. In buffer, the CD's fluorescence intensity (λex 354nm) enhanced over 115% after interaction with the enzyme proteins due to different lifetime components on its surface. The enhancement was also linked to FRET with the proteins (λex 274nm for TRP/TYR). The electrostatic interactions, as revealed from the zeta potential study, generated binding energy (ΔG, kcal/mol) in the range of -5.8 to -6.3 and greatly shifted the protein's secondary structure to β-strand contents. The CD's fluorescence in the blood serum medium was also enhanced where serum's particulate components contributed to the emission. All these subvert fluorescence emissions could be substantially cleaned for detection of peroxide generated in the enzymatic reaction by filtering the serum particulates and redox proteins prior to the addition of CDs to the reaction systems. The CD, however, could complement well in ABTS-based (absorbance at λmax 414nm) colorimetric reaction in blood serum without introducing protein or particle separation steps for sensitive detection of peroxide. The limit of detection, dynamic range, and sensitivity discerned for peroxide in the glucose oxidase-catalyzed reaction system were 183 μM, 0.02-0.10 mM (R2 = 0.98), and 0.2482 AU mM-1, respectively. Overall, these findings will guide clinical application of the peroxidatic CDs to detect various analytes in blood serum following fluorometric- and colorimetric-based principles.

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.

Fluorescence Liquid Biopsy for Cancer Detection Is Improved by Using Cationic Dendronized Hyperbranched Polymer

(1) Background: Biophysical techniques applied to serum samples characterization could promote the development of new diagnostic tools. Fluorescence spectroscopy has been previously applied to biological samples from cancer patients and differences from healthy individuals were observed. Dendronized hyperbranched polymers (DHP) based on bis(hydroxymethyl)propionic acid (bis-MPA) were developed in our group and their potential biomedical applications explored. (2) Methods: A total of 94 serum samples from diagnosed cancer patients and healthy individuals were studied (20 pancreatic ductal adenocarcinoma, 25 blood donor, 24 ovarian cancer, and 25 benign ovarian cyst samples). (3) Results: Fluorescence spectra of serum samples (fluorescence liquid biopsy, FLB) in the presence and the absence of DHP-bMPA were recorded and two parameters from the signal curves obtained. A secondary parameter, the fluorescence spectrum score (FSscore), was calculated, and the diagnostic model assessed. For pancreatic ductal adenocarcinoma (PDAC) and ovarian cancer, the classification performance was improved when including DHP-bMPA, achieving high values of statistical sensitivity and specificity (over 85% for both pathologies). (4) Conclusions: We have applied FLB as a quick, simple, and minimally invasive promising technique in cancer diagnosis. The classification performance of the diagnostic method was further improved by using DHP-bMPA, which interacted differentially with serum samples from healthy and diseased subjects. These preliminary results set the basis for a larger study and move FLB closer to its clinical application, providing useful information for the oncologist during patient diagnosis.

Analytical Challenges Assessing Protein Aggregation and Fragmentation Under Physiologic Conditions

Therapeutic proteins are administered by injection or infusion. After administration, the physiologic environment in the desired body compartment - fluid or tissue - can impact protein stability and lead to changes in the safety and/or efficacy profile. For example, protein aggregation and fragmentation are critical quality attributes of the drug product and can occur after administration to patients. In this context, the in vivo stability of therapeutic proteins has gained increasing attention. However, in vivo protein aggregation and fragmentation are difficult to assess and have been rarely investigated. This mini-review summarizes analytical approaches to assess the stability of therapeutic proteins using simulated physiologic conditions. Furthermore, we discuss factors potentially causing in vivo protein aggregation, precipitation, and fragmentation in complex biological fluids. Different analytical approaches are evaluated with respect to their applicability and possible shortcomings when it comes to these degradation events in biological fluids. Tracking protein stability in biological fluids typically requires purifying or labeling the protein of interest to circumvent matrix interference of biological fluids. Improved analytical methods are strongly needed to gain knowledge on in vivo protein aggregation and fragmentation. In vitro models can support the selection of lead candidates and accelerate the pre-clinical development of therapeutic proteins.

Toward a Point-of-Need Bioluminescence-Based Immunoassay Utilizing a Complete Shelf-Stable Reagent

Enzyme-linked immunosorbent assays (ELISAs) are used extensively for the detection and quantification of biomolecules in clinical diagnostics as well as in basic research. Although broadly used, the inherent complexities of ELISAs preclude their utility for straightforward point-of-need testing, where speed and simplicity are essential. With this in mind, we developed a bioluminescence-based immunoassay format that provides a sensitive and simple method for detecting biomolecules in clinical samples. We utilized a ternary, split-NanoLuc luciferase complementation reporter consisting of two small peptides (11mer, 13mer) and a 17 kDa polypeptide combined with a luminogenic substrate to create a complete, shelf-stable add-and-read assay detection reagent. Directed evolution was used to optimize reporter constituent sequences to impart chemical and thermal stability, as well as solubility, while formulation optimization was applied to stabilize an all-in-one reagent that can be reconstituted in aqueous buffers or sample matrices. The result of these efforts is a robust, first-generation bioluminescence-based homogenous immunoassay reporter platform where all assay components can be configured into a stable lyophilized cake, supporting homogeneous, rapid, and sensitive one-step biomolecule quantification in complex human samples. This technology represents a promising alternative immunoassay format with significant potential to bring critical diagnostic molecular detection testing closer to the point-of-need.

Assessing Particle Formation of Biotherapeutics in Biological Fluids

The stability of therapeutic proteins can be impacted in vivo after administration, which may affect patient safety or treatment efficacy, or both. Stability testing of therapeutic proteins using models representing physiologic conditions may guide preclinical development strategy; however, to date only a few studies assessing the physical stability are available in the public domain. In this manuscript, the stability of seven fluorescently labeled monoclonal antibodies (mAbs) was evaluated in human serum and phosphate-buffered saline, two models often discussed to be representative of the situation in humans after intravenous administration. Subvisible particles were analyzed using light obscuration, flow imaging, and imaging flow cytometry. All methods showed that serum itself formed particles under in vitro conditions. Imaging flow cytometry demonstrated that mean particle size and counts of mAbs increased substantially in serum over five days; however, particle formation in phosphate-buffered saline was comparably low. Stability differences were observed across the mAbs evaluated, and imaging flow cytometry data indicated that fluorescently labeled mAbs primarily interacted with serum components. The results indicate that serum may be more suitable as in vitro model to simulate physiologic intravenous conditions in patients closely and evaluate the in vivo stability of therapeutic proteins. Fluorescence labeling and detection methods may be applied to differentiate particles containing therapeutic protein from high amounts of serum particles that form over time.

An effective approach to the early diagnosis of colorectal cancer based on three-dimensional fluorescence spectra of human blood plasma

Colorectal cancer (CRC) is a common malignancy in the gastrointestinal tract, and its screening rates remain relatively low in the general population due to the lack of specific symptoms and effective methods. It is still in urgent need to develop rapid and reliable approach to the early diagnosis of CRC. Herein, based on the three-dimensional (3D) fluorescence spectra of human blood plasma, a combination strategy of Tchebichef image moments coupled with partial least squares-discriminate analysis (TM-PLS-DA) was proposed for the detection of CRC from three classes (CRC samples, adenomas samples and non-malignant findings). The established TM-PLS-DA classification model provided an 84 % correct classification for CRC prediction. Venetian blinds 10-fold cross validation was carried out. The error rates both in cross validation and test sets were less than 0.16. Sensitivity and specificity for CRC prediction were 0.95 and 0.88, respectively. At the same time, the diagnostic capacity of the proposed method was tested by receiver operating characteristics (ROC) analysis with area under the curve (AUC) of 0.94 for CRC diagnosis. These results demonstrate that the proposed TM-PLS-DA method based on the 3D fluorescence spectra of blood plasma has great advantage for the accurate CRC detection, which will provide a potential alternative approach for cancer diagnostics.

Introducing Principal Coordinate Analysis (PCoA) Assisted EEMF Spectroscopic Based Novel Analytical Approach for the Discrimination of Commercial Gasoline Fuels

In the present work, a novel analytical procedure by integrating principal coordinate analysis (PcoA) with excitation-emission matrix fluorescence (EEMF) spectroscopy was introduced for discriminating the commercial gasoline fuels. The PcoA technique involved analysis of the distance matrices containing the dissimilarity information and it can serve as an efficient tool for capturing the major as well as subtle compositional differences among the analyzed commercial gasoline samples. The utility of the proposed PcoA assisted EEMF analytical procedure was successfully tested by discriminating gasoline fuel samples belonging to five different industrial brands. The obtained results clearly showed that combination of PcoA and EEMF could provide a simple, sensitive and economical analytical procedure to carry out the rapid analyses of the gasoline samples belonging to different brands.

Identification and characterisation of fluorescent substances in spent dialysis fluid

Patients who suffer from end-stage renal disease require renal replacement therapy, including haemodialysis. While applying extracorporeal blood treatment, uraemic toxins accumulated in the patients' blood pass into a physiological solution, the dialysis fluid. Thus, important information about the patient's health status can be obtained by analysing the spent dialysis fluid. To make use of this information, corresponding analysis concepts must be developed. In this context, this article reports the analysis of fluorescence in spent dialysis fluid. Excitation and emission maxima of fluorescence in spent dialysis fluid were recorded, and the main fluorescent substances were identified and quantified using high-performance liquid chromatography analysis. Fluorescence in spent dialysis fluid has two prominent excitation maxima at λ_ex1 = 228 nm and λ_ex2 = 278 nm. However, both excitation maxima cause emission with maxima at λ_em = 350 nm. Identification of fluorescent substances using high-performance liquid chromatography showed that the main contributors to the overall fluorescence in spent dialysis fluid are tyrosine, tryptophan, indoxyl sulphate and indole-3-acetic acid. However, these substances are responsible for only one-third of the overall fluorescence of spent dialysis fluid. A large number of substances, each of which contributes only to a small part to the overall fluorescence, emit the remaining fluorescence.

Serum Autofluorescence and Biochemical Markers in Athlete's Response to Strength Effort in Normobaric Hypoxia: A Preliminary Study

The human organism has the ability to adapt to hypoxia conditions. Training in hypoxia is used in sport to improve the efficiency of athletes; however, type of training affects the direction and scope of this process. Therefore, in this study, the usefulness of serum fluorescence spectroscopy to study the assessment of athlete's response to strength effort in hypoxia is considered in comparison with biochemical assay. Six resistance-trained male subjects took part in a research experiment. They performed barbell squats in simulated normobaric hypoxic conditions with deficiency of oxygen 11.3%, 13% 14.3% compared to 21% in normoxic conditions. Fluorescence intensity of tyrosine revealed high sensitivity on strength effort whereas tryptophan was more dependent on high altitude. Changes in emission in the visible region are associated with altering cell metabolism dependent on high altitude as well as strength training and endurance training. Significant changes in serum fluorescence intensity with relatively weak modifications in biochemical assay at 3000 m above sea level (ASL) were observed. Training at 5000 m ASL caused changes in fluorescence parameters towards the normobaric specific values, and pronounced decreases of lactate level and kinase creatine activity were observed. Such modifications of fluorescence and biochemical assay indicate increased adaptation of the organism to effort in oxygen-deficient conditions at 5000 m ASL, unlike 3000 m ASL. Fluorescence spectroscopy study of serum accompanied by biochemical assay can contribute to the understanding of metabolic regulation and the physiological response to hypoxia. The results of serum autofluorescence during various concepts of altitude training may be a useful method to analyze individual response to acute and chronic hypoxia. An endogenous tryptophan could be exploited as intrinsic biomarker in autofluorescence studies. However, these issues require further research.

Bimetallic gold/silver nanoclusters as a fluorescent probe for detection of methotrexate and doxorubicin in serum

New bimetallic gold/silver nanoclusters (NCs) are reported that display strong blue fluorescence with excitation/emission maxima at 370/455 nm, decay times of around 14 ns for the main components, and a quantum yield of around 20%. The NCs were synthesized by using L-tryptophan (L-Trp) as the template to react with tetrachloroauric acid and silver nitrate at 120 °C for 4 h in a one-pot reaction. Their fluorescence is around 5 times stronger than that of pure gold nanoclusters. The fluorescence of the bimetallic NCs is strongly reduced in the presence of the antitumor drugs methotrexate (MTX) and doxorubicin (DOX) due to an inner filter effect. Response to MTX is linear in the 2.5-150 μM concentration range, and to DOX in the 2.5-150 μM concentration range. The detection limits are as low as 2.5 nM and 3 nM, respectively. The recoveries from spiked serum are between 87.7% - 101.2% for MTX and between 86.2%-105.4% for DOX. Graphical abstract Schematic presentation of the synthesis of Au/AgNCs and the fluorometric determination of methotrexate (MTX) and doxorubicin (DOX) based on the inner filter effect.

A Novel Quantitative Method for the Detection of Lipofuscin, the Main By-Product of Cellular Senescence, in Fluids

Lipofuscin accumulation is a hallmark of senescence. This nondegradable material aggregates in the cytoplasm of stressed or damaged cells due to metabolic imbalance associated with aging and age-related diseases. Indications of a soluble state of lipofuscin have also been provided, rendering the perspective of monitoring such processes via lipofuscin quantification in liquids intriguing. Therefore, the development of an accurate and reliable method is of paramount importance. Currently available assays are characterized by inherent pitfalls which demote their credibility. We herein describe a simple, highly specific and sensitive protocol for measuring lipofuscin levels in any type of liquid. The current method represents an evolution of a previously described assay, developed for in vitro and in vivo senescent cell recognition that exploits a newly synthesized Sudan Black-B analog (GL13). Analysis of human clinical samples with the modified protocol provided strong evidence of its usefulness for the exposure and surveillance of age-related conditions.

An Allosteric-Probe for Detection of Alkaline Phosphatase Activity and Its Application in Immunoassay

A fluorescence strategy for alkaline phosphatase (ALP) assay in complicated samples with high sensitivity and strong stability is developed based on an allosteric probe (AP). This probe consists of two DNA strands, a streptavidin (SA) aptamer labeled by fluorophore and its totally complementary DNA (cDNA) with a phosphate group on the 5′ end. Upon ALP introduction, the phosphate group on the cDNA is hydrolyzed, leaving the unhydrolyzed cDNA sequence for lambda exonuclease (λ exo) digestion and releasing SA aptamer for binding to SA beads, which results in fluorescence enhancement of SA beads that can be detected by flow cytometry or microscopy. We have achieved a detection limit of 0.012 U/mL with a detection range of 0.02~0.15 U/mL in buffer and human serum. These figures of merit are better than or comparable to those of other methods. Because the fluorescence signal is localized on the beads, they can be separated to remove fluorescence background from complicated biological systems. Notably, the new strategy not only applies to ALP detection with simple design, easy operation, high sensitivity, and good compatibility in complex solution, but also can be utilized in ALP-linked immunosorbent assays for the detection of a wide range of targets.

The multi-resolution capability of Tchebichef moments and its applications to the analysis of fluorescence excitation-emission spectra

Fluorescence spectroscopy with an excitation-emission matrix (EEM) is a fast and inexpensive technique and has been applied to the detection of a very wide range of analytes. However, serious scattering and overlapping signals hinder the applications of EEM spectra. In this contribution, the multi-resolution capability of Tchebichef moments was investigated in depth and applied to the analysis of two EEM data sets (data set 1 consisted of valine-tyrosine-valine, tryptophan-glycine and phenylalanine, and data set 2 included vitamin B1, vitamin B2 and vitamin B6) for the first time. By means of the Tchebichef moments with different orders, the different information in the EEM spectra can be represented. It is owing to this multi-resolution capability that the overlapping problem was solved, and the information of chemicals and scatterings were separated. The obtained results demonstrated that the Tchebichef moment method is very effective, which provides a promising tool for the analysis of EEM spectra. It is expected that the applications of Tchebichef moment method could be developed and extended in complex systems such as biological fluids, food, environment and others to deal with the practical problems (overlapped peaks, unknown interferences, baseline drifts, and so on) with other spectra.

Oblique rotation of factors: a novel pattern recognition strategy to classify fluorescence excitation-emission matrices of human blood plasma for early diagnosis of colorectal cancer

Colorectal cancer (CRC) ranks high in both men and women, accounting for about 13% of all cancers. In this study, a novel pattern recognition strategy is proposed to improve early diagnosis of CRC through visualizing the relationship between different spectral patterns in a case-control research. Partial least squares-discriminant analysis (PLS-DA) and supervised Kohonen network (SKN) were used to classify the fluorescence excitation-emission matrices (EEMs) from 289 human blood plasma samples containing CRC patients, adenomas tumor, other non-malignant findings and healthy individuals. To obtain optimal factors, oblique rotation (OR) and genetic algorithm (GA) were used to rotate the factors by optimizing transformation matrix elements. Transformed factors were introduced to SKN to build a classification model and the model performance was examined via comparison with a common classifier; PLS-DA. Classification models were built for CRC-healthy and adenomas-healthy samples and the best results were obtained through applying GA-OR on PLS factors and introducing them to the classifiers. Non-error rates for SKN and PLS-DA models assisted with GA (for selecting more informative PLS factors) and OR were equal to 0.97 and 0.95 in cross validation and 0.93 and 0.90 for prediction of the external test set, respectively. Moreover, according to the acceptable results for adenomas-healthy cases using optimal factors, CRC can be diagnosed in early stages. Combining classifiers and optimal factors proved to be efficient for distinguishing healthy and malignant samples, and OR can significantly improve performance of the classification model.

Reverse Fluorescence Enhancement and Colorimetric Bimodal Signal Readout Immunochromatography Test Strip for Ultrasensitive Large-Scale Screening and Postoperative Monitoring

Ultrasensitive and quantitative fast screening of cancer biomarkers by immunochromatography test strip (ICTS) is still challenging in clinic. The gold nanoparticles (NPs) based ICTS with colorimetric readout enables a quick spectrum screening but suffers from nonquantitative performance; although ICTS with fluorescence readout (FICTS) allows quantitative detection, its sensitivity still deserves more efforts and attentions. In this work, by taking advantages of colorimetric ICTS and FICTS, we described a reverse fluorescence enhancement ICTS (rFICTS) with bimodal signal readout for ultrasensitive and quantitative fast screening of carcinoembryonic antigen (CEA). In the presence of target, gold NPs aggregation in T line induced colorimetric readout, allowing on-the-spot spectrum screening in 10 min by naked eye. Meanwhile, the reverse fluorescence enhancement signal enabled more accurately quantitative detection with better sensitivity (5.89 pg/mL for CEA), which is more than 2 orders of magnitude lower than that of the conventional FICTS. The accuracy and stability of the rFICTS were investigated with more than 100 clinical serum samples for large-scale screening. Furthermore, this rFICTS also realized postoperative monitoring by detecting CEA in a patient with colon cancer and comparing with CT imaging diagnosis. These results indicated this rFICTS is particularly suitable for point-of-care (POC) diagnostics in both resource-rich and resource-limited settings.

Rapid and non-invasive diagnosis of coronary artery disease via clinical laboratory parameters and1H-NMR spectra of human blood plasma

Coronary artery disease (CAD), one of the most common fatal diseases in the world, was examinedviainvestigation of the¹H-NMR spectra of human blood plasma and clinical laboratory parameters with the aim of early disease diagnosis.

Spectrally matched upconverting luminescent nanoparticles for monitoring enzymatic reactions

We report on upconverting luminescent nanoparticles (UCLNPs) that are spectrally tuned such that their emission matches the absorption bands of the two most important species associated with enzymatic redox reactions. The core-shell UCLNPs consist of a β-NaYF4 core doped with Yb(3+)/Tm(3+) ions and a shell of pure β-NaYF4. Upon 980 nm excitation, they display emission bands peaking at 360 and 475 nm, which is a perfect match to the absorption bands of the enzyme cosubstrate NADH and the coenzyme FAD, respectively. By exploiting these spectral overlaps, we have designed fluorescent detection schemes for NADH and FAD that are based on the modulation of the emission intensities of UCLNPs by FAD and NADH via an inner filter effect.

Antigen detection based on background fluorescence quenching immunochromatographic assay

Gold immunochromatographic assay (GICA) has been around for quite a while, but it is qualitative in the vast majority of applications. A fast, simple and quantitative GICA is in call for better medicine. In the current study, we have established a novel, quantitative GICA based on fluorescence quenching and nitrocellulose membrane background signals, called background fluorescence quenching immunochromatographic assay (bFQICA). Using model analyte alpha-fetoprotein (AFP), the present study assessed the performance of bFQICA in numerous assay aspects. With serial dilutions of the international AFP standard, standard curves for the calculation of AFP concentration were successfully established. At 10 and 100ngmL(-1) of the international AFP standard, the assay variability was defined with a coefficient of variance at 10.4% and 15.2%, respectively. For samples with extended range of AFP levels, bFQICA was able to detect AFP at as low as 1ngmL(-1). Fluorescence in bFQICA strips stayed constant over months. A good correlation between the results from bFQICA and from a well-established Roche electrochemiluminescence immunoassay was observed in 27 serum samples (r=0.98, p<0.001). In conclusion, our study has demonstrated distinctive features of bFQICA over conventional GICA, including utilization of a unique fluorescence ratio between nitrocellulose membrane background and specific signals (F1/F2) to ensure accurate measurements, combined qualitative and quantitative capabilities, and exceptionally high sensitivity for detection of very low levels of antigens. All of these features could make bFQICA attractive as a model for antigen-antibody complex based GICA, and could promote bFQICA to a broad range of applications for investigation of a variety of diseases.

Quantification of doxorubicin in biofluids using white light excitation fluorescence

A fiber optic spectrometer setup was designed for white light excitation fluorescence 'WLEF' based measurements. Using this setup, two different analytical methods, a self referencing ratio-metric and a difference WLEF methods, were developed for the quantification of doxorubicin (DXR) in biofluids. It was seen that Acetonitrile (ACN) acts as an efficient and transparent extracting medium for DXR. The figures of merit and the percent recoveries of DXR in blood serum, even in presence of external fluorophores and in urine samples are comparable with existing analytical methods. The compact spectrometer is expected to be useful for easy quantification of fluorescent pharmaceuticals in biofluids.

Early diagnosis of colorectal cancer in rats with DMH induced carcinogenesis by means of urine autofluorescence analysis

Cancer is one of the most highlighted topics of current research. Early detection of this disease allows more effective therapy, hence higher chance of cure. Application of fluorescence spectral techniques into oncological diagnostic is one of the potential alternatives. Chemically induced carcinogenesis in rats is widely used model for exploration of various aspects of colorectal cancer. This study shows value of discriminate analysis of urine fluorescent fingerprint between healthy control group of rats and those with dimethylhydrazine induced early lesions of colorectal cancer. Using fluorescence spectroscopy, significant difference (P < 0.05) between both of group was achieved.

Diagnosis of liver cancer and cirrhosis by the fluorescence spectra of blood and urine

Liver cancer or hepato cellular carcinoma (HCC) is a serious malady with only 10% survival rate and is fatal next only to pancreatic cancer. This disease is conventionally detected and diagnosed by ultra sound, CT or MRI scans which are quite expensive. Also the discrimination between cirrhosis and HCC, by these imaging techniques, is poor. The conventional tissue biopsy is quite invasive and painful. In the new diagnostic procedure presented in this paper we have obtained fluorescence emission spectra with excitation at 400 nm and the synchronous emission spectra (Δλ = 10 nm) for a set of blood and urine samples (Normal control N = 25, Liver Malfunction N = 58). Based on the ratio fluorometric parameters, all the three liver maladies (minor inflammation like Hepatitis C, serious diseases like Cirrhosis and hepatoma) could be detected and discriminated with an accuracy of about 80%. Hence this inexpensive, non invasive, optical technique may have significant impact in screening, diagnosis and also prognosis of HCC in large segment of people in the populous Asian countries.

Data fusion in metabolomic cancer diagnostics

We have recently shown that fluorescence spectroscopy of plasma samples has promising abilities regarding early detection of colorectal cancer. In the present paper, these results were further developed by combining fluorescence with the biomarkers, CEA and TIMP-1 and traditional metabolomic measurements in the form of (1)H NMR spectroscopy. The results indicate that using an extensive profile established by combining such measurements together with the biomarkers is better than using single markers.

Spectral discrimination between normal and leukemic human sera using delayed luminescence

In this work, photoinduced delayed luminescence (DL) was used to distinguish serum samples of patients with acute lymphoblastic leukemia from those of healthy volunteers. DL decay kinetics of human serum samples was measured using a homebuilt ultraweak luminescence detection system. It was found a significant difference in the weight distribution of the decay rate between normal and leukemic serum samples. A comparison of the DL kinetics parameters including the initial intensity, the peak decay rate, and the peak weight value was used in making discrimination between normal and leukemic human sera. Results in this work contribute to the development of a novel optical method for the early diagnosis of leukemia.

Second-order calibration applied to quantification of two active components of Schisandra chinensis in complex matrix

The effectiveness of traditional Chinese medicine (TCM) against various diseases urges more low cost, speed and sensitive analytical methods for investigating the phamacology of TCM and providing a theoretical basis for clinical use. The potential of second-order calibration method was validated for the quantification of two effective ingredients of Schisandra chinensis in human plasma using spectrofluorimetry. The results obtained in the present study demonstrate the advantages of this strategy for multi-target determination in complex matrices. Although the spectra of the analytes are similar and a large number of interferences also exist, second-order calibration method could predict the accurate concentrations together with reasonable resolution of spectral profiles for analytes of interest owing to its ‘second-order advantage’. Moreover, the method presented in this work allows one to simply experimental procedure as well as reduces the use of harmful chemical solvents.

Cancer detection by native fluorescence of urine

Because cancer is a dreaded disease, a number of techniques such as biomarker evaluation, mammograms, colposcopy, and computed tomography scan are currently employed for early diagnosis. Many of these are specific to a particular site, invasive, and often expensive. Hence, there is a definite need for a simple, generic, noninvasive protocol for cancer detection, comparable to blood and urine tests for diabetes. Our objective is to show the results of a novel study in the diagnosis of several cancer types from the native or intrinsic fluorescence of urine. We use fluorescence emission spectra (FES) and stokes shift spectra (SSS) to analyze the native fluorescence of the first voided urine samples of healthy controls (N=100) and those of cancer patients (N=50) of different etiology. We show that flavoproteins and porphyrins released into urine can act as generic biomarkers of cancer with a specificity of 92%, a sensitivity of 76%, and an overall accuracy of 86.7%. We employ FES and SSS for rapid and cost-effective quantification of certain intrinsic biomarkers in urine for screening and diagnosis of most common cancer types with an overall accuracy of 86.7%.

Luminescent chemical sensing, biosensing, and screening using upconverting nanoparticles

Upconverting nanoparticles (UCNPs) display the unique property of converting near-infrared light (with wavelengths of typically 800-1,000 nm) into visible luminescence. Following a short introduction into the mechanisms leading to the effect, the main classes of materials used are discussed. We then review the state of the art of using UCNPs: (1) to label biomolecules such as antibodies and (synthetic) oligomers for use in affinity assay and flow assays; (2) to act as nanolamps whose emission intensity is modulated by chemical indicators, thus leading to a novel kind of chemical sensors; and (3), to act as donors in luminescence resonance energy transfer in chemical sensors and biosensors.

Fluorescence intensity calibration using the Raman scatter peak of water

Fluorescence data of replicate samples obtained from different fluorescence spectrometers or by the same spectrometer but with different instrument settings can have great intensity differences. In order to compare such data an intensity calibration must be applied. Here we explain a simple calibration method for fluorescence intensity using only the integrated area of a water Raman peak. By applying this method to data from three different instruments, we show that it is possible to remove instrument-dependent intensity factors, and we present results on a unified scale of Raman units. The method presented is a rapid and simple approach suitable for routine measurements with no need for hazardous chemicals.