A platform for combined DNA and protein microarrays based on total internal reflection fluorescence

Design of Hydrogel Silk-Based Microarrays and Molecular Beacons for Reagentless Point-of-Care Diagnostics

We have developed a novel microarray system based on three technologies: 1) molecular beacons designed to interact with DNA targets at room temperature (25–27°C), 2) tridimensional silk-based microarrays containing the molecular beacons immersed in the silk hydrogel, and 3) shallow angle illumination, which uses separated optical pathways for excitation and emission. Unlike conventional microarrays that exhibit reduced signal-to-background ratio, require several stages of incubation, rinsing, and stringency control, and measure only end-point results, our microarray technology provides enhanced signal-to-background ratio (achieved by separating the optical pathways for excitation and emission, resulting in reduced stray light), performs analysis rapidly in one step without the need for labeling DNA targets, and measures the entire course of association kinetics between target DNA and the molecular beacons. To illustrate the benefits of our technology, we conducted microarray assays designed for the identification of influenza viruses. We show that in a single microarray slide, we can identify the virus subtype according to the molecular beacons designed for hemagglutinin (H1, H2, and H3) and neuraminidase (N1, N2). We also show the identification of human and swine influenza using sequence-specific molecular beacons. This microarray technology can be easily implemented for reagentless point-of-care diagnostics of several contagious diseases, including coronavirus variants responsible for the current pandemic.

Live-Cell Total Internal Reflection Fluorescence (TIRF) Microscopy to Investigate Protein Internalization Dynamics

The establishment of apicobasal or planar cell polarity involves many events that occur at or near the plasma membrane including focal adhesion dynamics, endocytosis, exocytosis, and cytoskeletal reorganization. It is desirable to visualize these events without interference from other regions deeper within the cell. Total internal reflection fluorescence (TIRF) microscopy utilizes an elegant optical sectioning approach to visualize fluorophores near the sample-coverslip interface. TIRF provides high-contrast fluorescence images with limited background and virtually no out-of-focus light, ideal for visualizing and tracking dynamics near the plasma membrane. In this chapter, we present a general experimental and analysis TIRF pipeline for studying cell surface receptor endocytosis. The approach presented can be easily applied to study other dynamic biological processes at or near the plasma membrane using TIRF microscopy.

Multicolor Coding Up-Conversion Nanoplatform for Rapid Screening of Multiple Foodborne Pathogens

Technologies for rapid screening of multiple foodborne pathogens have been urgently needed because of the complex food matrix and high outbreaks of foodborne diseases. In this study, multicolor coding up-conversion nanoparticles (UCNPs) were synthesized and applied for rapid and simultaneous detection of five kinds of foodborne pathogens. The multicolor coding UCNPs were obtained through doping different concentrations of a sensitizer (Yb³⁺) on the shell of the synthesized NaYF₄:Yb³⁺, Tm³⁺ (20%/2%)@NaYF₄:Yb³⁺, and Er³⁺ (x %/2%) core/shell nanocrystals. All the UCNPs could emit red and green luminescence simultaneously once excited with near-infrared wavelength (980 nm), and the ratio of red and green (R/G ratio) emission light intensity of each kind of UCNPs varied depending on the Yb³⁺ doping concentration. In addition, the magnetic nanoparticles (MNPs) modified with the monoclonal antibodies (mAbs) against the target bacteria were used to capture and separate the bacteria, resulting in obtaining the MNP-bacterium complexes. Different UCNPs with multicolor coding acted as signal probes were also modified with the mAbs to react with the MNP-bacterium complexes to form the MNP-bacterium-UCNP sandwich complexes. After the sandwich complexes were excited with a wavelength of 980 nm, the obtained R/G ratios and the green photoluminescence intensity (PL intensity) could be used to distinguish and quantitatively detect foodborne pathogens, respectively. This proposed nanoplatform could detect five foodborne pathogens simultaneously within 2 h with good sensitivity and specificity, showing great potential for multiplex detection of other targets in the fields of medical diagnosis and food security.

Phosphorylation of NMDA receptors by cyclin B/CDK1 modulates calcium dynamics and mitosis

N-methyl-D-aspartate receptors (NMDAR) are glutamate-gated calcium channels named after their artificial agonist. NMDAR are implicated in cell proliferation under normal and pathophysiological conditions. However, the role of NMDAR during mitosis has not yet been explored in individual cells. We found that neurotransmitter-evoked calcium entry via endogenous NMDAR in cortical astrocytes was transient during mitosis. The same occurred in HEK293 cells transfected with the NR1/NR2A subunits of NMDAR. This transient calcium entry during mitosis was due to phosphorylation of the first intracellular loop of NMDAR (S584 of NR1 and S580 of NR2A) by cyclin B/CDK1. Expression of phosphomimetic mutants resulted in transient calcium influx and enhanced NMDAR inactivation independent of the cell cycle phase. Phosphomimetic mutants increased entry of calcium in interphase and generated several alterations during mitosis: increased mitotic index, increased number of cells with lagging chromosomes and fragmentation of pericentriolar material. In summary, by controlling cytosolic calcium, NMDAR modulate mitosis and probably cell differentiation/proliferation. Our results suggest that phosphorylation of NMDAR by cyclin B/CDK1 during mitosis is required to preserve mitotic fidelity. Altering the modulation of the NMDAR by cyclin B/CDK1 may conduct to aneuploidy and cancer.

Development of a multiplex and sensitive lateral flow immunoassay for the diagnosis of periprosthetic joint infection

The diagnosis of periprosthetic joint infection (PJI) remains a challenge. However, recent studies showed that synovial fluid biomarkers have demonstrated greater diagnostic accuracy than the currently used PJI diagnostic tests. In many diagnostic tests, combining several biomarkers into panels is critical for improving diagnostic efficiency, enhancing the diagnostic precision for specific diseases, and reducing cost. In this study, we prove that combining alpha-defensin and C-reactive protein (CRP) as biomarkers possesses the potential to provide accurate PJI diagnosis. To further verify the result, we developed a multi-target lateral flow immunoassay strip (msLFIA) with staking pad design to obtain on-site rapid response for clinical diagnosis of PJI. A total of 10 synovial fluid samples were tested using the msLFIA, and the results showed that the combined measurements of synovial fluid alpha-defensin and CRP levels were consistent with those obtained from a commercial enzyme-linked immunosorbent assay kit. In addition, we developed a multi-target lateral flow immunoassay strip (msLFIA) with staking pad design to obtain on-site rapid response for clinical diagnosis of PJI, which the multi-target design is used to increase specificity and the stacking pad design is to enhance detection sensitivity. As a result, the turnaround time of the highly sensitive test can be limited from several hours to 20 min. We expect that the developed msLFIA possesses the potential for routine monitoring of PJI as a convenient, low-cost, rapid and easy to use detection device for PJI.

Heterologous calcium-dependent inactivation of Orai1 by neighboring TRPV1 channels modulates cell migration and wound healing

Store-operated calcium entry (SOCE) is an essential calcium influx mechanism in animal cells. One of the most important auto regulatory control systems involves calcium-dependent inactivation (CDI) of the Orai channel, which prevents excessive calcium influx. In the present study we analyze the role of two channels in the induction of CDI on Orai1. Here we show that calcium entering through freely diffusing TRPV1 channels induce strong CDI on Orai1 while calcium entering through P2X₄ channel does not. TRPV1 can induce CDI on Orai1 because both channels were found in close proximity in the cell membrane. This was not observed with P2X₄ channels. To our knowledge, this is the first study demonstrating that calcium arising from different channels may contribute to the modulation of Orai1 through CDI in freely diffusing single channels of living cells. Our results highlight the role of TRPV1-mediated CDI on Orai1 in cell migration and wound healing.

Bastián-Eugenio et al. showed that calcium entering the cell via TRPV1, but not P2X₄ channels, can induce calcium-dependent inactivation of Orai1. This inactivation impacts thrombin-induced cell migration and wound healing suggesting an important role of Orai1 modulation by TRPV1 channels.

Fluorescence-based kinetic analysis of miniaturized protein microarrays

Ideal monitoring devices should enjoy a combination of characteristics, e.g. high sensitivity, multiplexing, portability, short time-to-result (TTR). Typically, no device meets all of these demands since some of them are contradictory, to some extent. Herein, we present a miniaturized platform based on fluorescent detection, which is sensitive, readily allows multiplexing, and allows real-time monitoring of the signal, thus allowing extraction of kinetic information as well as drastic reduction of TTR. This is achieved via miniaturization of active spots, integration with microfluidics, and algorithmic approaches. We validate its performance by comparing with evanescent field excitation, which obtains similar results, however without the addition of the necessary complex hardware.

A novel family of mammalian transmembrane proteins involved in cholesterol transport

Cholesterol is an essential compound in mammalian cells because it is involved in a wide range of functions, including as a key component of membranes, precursor of important molecules such as hormones, bile acids and vitamin D. The cholesterol transport across the circulatory system is a well-known process in contrast to the intracellular cholesterol transport, which is poorly understood. Recently in our laboratory, we identified a novel protein in C. elegans involved in dietary cholesterol uptake, which we have named ChUP-1. Insillicoanalysis identified two putative orthologue candidate proteins in mammals. The proteins SIDT1 and SIDT2 share identity and conserved cholesterol binding (CRAC) domains with C. elegans ChUP-1. Both mammalian proteins are annotated as RNA transporters in databases. In the present study, we show evidence indicating that SIDT1 and SIDT2 not only do not transport RNA, but they are involved in cholesterol transport. Furthermore, we show that single point mutations directed to disrupt the CRAC domains of both proteins prevent FRET between SIDT1 and SIDT2 and the cholesterol analogue dehydroergosterol (DHE) and alter cholesterol transport.

A cholesterol-binding domain in STIM1 modulates STIM1-Orai1 physical and functional interactions

STIM1 and Orai1 are the main components of a widely conserved Calcium influx pathway known as store-operated calcium entry (SOCE). STIM1 is a calcium sensor, which oligomerizes and activates Orai channels when calcium levels drop inside the endoplasmic reticulum (ER). The series of molecular rearrangements that STIM1 undergoes until final activation of Orai1 require the direct exposure of the STIM1 domain known as SOAR (Stim Orai Activating Region). In addition to these complex molecular rearrangements, other constituents like lipids at the plasma membrane, play critical roles orchestrating SOCE. PI(4,5)P₂ and enriched cholesterol microdomains have been shown as important signaling platforms that recruit the SOCE machinery in steps previous to Orai1 activation. However, little is known about the molecular role of cholesterol once SOCE is activated. In this study we provide clear evidence that STIM1 has a cholesterol-binding domain located inside the SOAR region and modulates Orai1 channels. We demonstrate a functional association of STIM1 and SOAR to cholesterol, indicating a close proximity of SOAR to the inner layer of the plasma membrane. In contrast, the depletion of cholesterol induces the SOAR detachment from the plasma membrane and enhances its association to Orai1. These results are recapitulated with full length STIM1.

Evanescent wave fluorescence biosensors: Advances of the last decade

Biosensor development has been a highly dynamic field of research and has progressed rapidly over the past two decades. The advances have accompanied the breakthroughs in molecular biology, nanomaterial sciences, and most importantly computers and electronics. The subfield of evanescent wave fluorescence biosensors has also matured dramatically during this time. Fundamentally, this review builds on our earlier 2005 review. While a brief mention of seminal early work will be included, this current review will focus on new technological developments as well as technology commercialized in just the last decade. Evanescent wave biosensors have found a wide array applications ranging from clinical diagnostics to biodefense to food testing; advances in those applications and more are described herein.

Quantitative evaluation of ABC transporter-mediated drug resistance based on the determination of the anticancer activity of camptothecin against breast cancer stem cells using TIRF

Total internal reflection fluorescence microscopy (TIRF) and Qdot probe based analytical method for the simultaneous evaluation of the cytotoxic ability of camptothecin and the drug resistance profile upon the inhibition of drug efflux pumps in breast cancer stem cells.

Shrink-induced silica multiscale structures for enhanced fluorescence from DNA microarrays

We describe a manufacturable and scalable method for fabrication of multiscale wrinkled silica (SiO2) structures on shrink-wrap film to enhance fluorescence signals in DNA fluorescence microarrays. We are able to enhance the fluorescence signal of hybridized DNA by more than 120 fold relative to a planar glass slide. Notably, our substrate has improved detection sensitivity (280 pM) relative to planar glass slide (11 nM). Furthermore, this is accompanied by a 30-45 times improvement in the signal-to-noise ratio (SNR). Unlike metal enhanced fluorescence (MEF) based enhancements, this is a far-field and uniform effect based on surface concentration and photophysical effects from the nano- to microscale SiO2 structures. Notably, the photophysical effects contribute an almost 2.5 fold enhancement over the concentration effects alone. Therefore, this simple and robust method offers an efficient technique to enhance the detection capabilities of fluorescence based DNA microarrays.

Exploiting fluorescence for multiplex immunoassays on protein microarrays

Protein microarray technology is becoming the method of choice for identifying protein interaction partners, detecting specific proteins, carbohydrates and lipids, or for characterizing protein interactions and serum antibodies in a massively parallel manner. Availability of the well-established instrumentation of DNA arrays and development of new fluorescent detection instruments promoted the spread of this technique. Fluorescent detection has the advantage of high sensitivity, specificity, simplicity and wide dynamic range required by most measurements. Fluorescence through specifically designed probes and an increasing variety of detection modes offers an excellent tool for such microarray platforms. Measuring for example the level of antibodies, their isotypes and/or antigen specificity simultaneously can offer more complex and comprehensive information about the investigated biological phenomenon, especially if we take into consideration that hundreds of samples can be measured in a single assay. Not only body fluids, but also cell lysates, extracted cellular components, and intact living cells can be analyzed on protein arrays for monitoring functional responses to printed samples on the surface. As a rapidly evolving area, protein microarray technology offers a great bulk of information and new depth of knowledge. These are the features that endow protein arrays with wide applicability and robust sample analyzing capability. On the whole, protein arrays are emerging new tools not just in proteomics, but glycomics, lipidomics, and are also important for immunological research. In this review we attempt to summarize the technical aspects of planar fluorescent microarray technology along with the description of its main immunological applications.

Point-of-care diagnostic tools to detect circulating microRNAS as biomarkers of disease

MicroRNAs or miRNAs are a form of small non-coding RNAs (ncRNAs) of 19–22 nucleotides in length in their mature form. miRNAs are transcribed in the nucleus of all cells from large precursors, many of which have several kilobases in length. Originally identified as intracellular modulators of protein synthesis via posttranscriptional gene silencing, more recently it has been found that miRNAs can travel in extracellular human fluids inside specialized vesicles known as exosomes. We will be referring to this miRNAs as circulating microRNAs. More interestingly, the miRNA content inside exosomes changes during pathological events. In the present review we analyze the literature about circulating miRNAs and their possible use as biomarkers. Furthermore, we explore their future in point-of-care (POC) diagnostics and provide an example of a portable POC apparatus useful in the detection of circulating miRNAs.

A cholesterol recognition amino acid consensus domain in GP64 fusion protein facilitates anchoring of baculovirus to mammalian cells

Baculoviridae is a large family of double-stranded DNA viruses that selectively infect insects. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) is the best-studied baculovirus from the family. Many studies over the last several years have shown that AcMNPV can enter a wide variety of mammalian cells and deliver genetic material for foreign gene expression. While most animal viruses studied so far have developed sophisticated mechanisms to selectively infect specific cells and tissues in an organism, AcMNPV can penetrate and deliver foreign genes into most cells studied to this date. The details about the mechanisms of internalization have been partially described. In the present study, we have identified a cholesterol recognition amino acid consensus (CRAC) domain present in the AcMNPV envelope fusion protein GP64. We demonstrated the association of a CRAC domain with cholesterol, which is important to facilitate the anchoring of the virus at the mammalian cell membrane. Furthermore, this initial anchoring favors AcMNPV endocytosis via a dynamin- and clathrin-dependent mechanism. Under these conditions, efficient baculovirus-driven gene expression is obtained. In contrast, when cholesterol is reduced from the plasma membrane, AcMNPV enters the cell via a dynamin- and clathrin-independent mechanism. The result of using this alternative internalization pathway is a reduced level of baculovirus-driven gene expression. This study is the first to document the importance of a novel CRAC domain in GP64 and its role in modulating gene delivery in AcMNPV.

Protein arrays as tool for studies at the host-pathogen interface

Pathogens and parasites encode a wide spectrum of multifunctional proteins interacting to and modifying proteins in host cells. However, the current lack of a reliable method to unveil the protein-protein interactions (PPI) at the host-pathogen interface is retarding our understanding of many important pathogenic processes. Thus, the identification of proteins involved in host-pathogen interactions is important for the elucidation of virulence determinants, mechanisms of infection, host susceptibility and/or disease resistance. In this sense, proteomic technologies have experienced major improvements in recent years and protein arrays are a powerful and modern method for studying PPI in a high-throughput format. This review focuses on these techniques analyzing the state-of-the-art of proteomic technologies and their possibilities to diagnose and explore host-pathogen interactions. Major technical advancements, applications and protocol concerns are presented, so readers can appreciate the immense progress achieved and the current technical options available for studying the host-pathogen interface. Finally, future uses of this kind of array-based proteomic tools in the fight against infectious and parasitic diseases are discussed.

Microarray technology for major chemical contaminants analysis in food: current status and prospects

Chemical contaminants in food have caused serious health issues in both humans and animals. Microarray technology is an advanced technique suitable for the analysis of chemical contaminates. In particular, immuno-microarray approach is one of the most promising methods for chemical contaminants analysis. The use of microarrays for the analysis of chemical contaminants is the subject of this review. Fabrication strategies and detection methods for chemical contaminants are discussed in detail. Application to the analysis of mycotoxins, biotoxins, pesticide residues, and pharmaceutical residues is also described. Finally, future challenges and opportunities are discussed.