A microarray biosensor for multiplexed detection of microbes using grating-coupled surface plasmon resonance imaging

Recent advances in surface plasmon resonance imaging and biological applications

Surface Plasmon Resonance Imaging (SPRI) is a robust technique for visualizing refractive index changes, which enables researchers to observe interactions between nanoscale objects in an imaging manner. In the past period, scholars have been attracted by the Prism-Coupled and Non-prism Coupled configurations of SPRI and have published numerous experimental results. This review describes the principle of SPRI and discusses recent developments in Prism-Coupled and Non-prism Coupled SPRI techniques in detail, respectively. And then, major advances in biological applications of SPRI are reviewed, including four sub-fields (cells, viruses, bacteria, exosomes, and biomolecules). The purpose is to briefly summarize the recent advances of SPRI and provide an outlook on the development of SPRI in various fields.

Development of a biomarker signature using grating-coupled fluorescence plasmonic microarray for diagnosis of MIS-C

Multisystem inflammatory syndrome in children (MIS-C) is a rare but serious condition that can develop 4–6 weeks after a school age child becomes infected by SARS-CoV-2. To date, in the United States more than 8,862 cases of MIS-C have been identified and 72 deaths have occurred. This syndrome typically affects children between the ages of 5–13; 57% are Hispanic/Latino/Black/non-Hispanic, 61% of patients are males and 100% have either tested positive for SARS-CoV-2 or had direct contact with someone with COVID-19. Unfortunately, diagnosis of MIS-C is difficult, and delayed diagnosis can lead to cardiogenic shock, intensive care admission, and prolonged hospitalization. There is no validated biomarker for the rapid diagnosis of MIS-C. In this study, we used Grating-coupled Fluorescence Plasmonic (GCFP) microarray technology to develop biomarker signatures in pediatric salvia and serum samples from patients with MIS-C in the United States and Colombia. GCFP measures antibody-antigen interactions at individual regions of interest (ROIs) on a gold-coated diffraction grating sensor chip in a sandwich immunoassay to generate a fluorescent signal based on analyte presence within a sample. Using a microarray printer, we designed a first-generation biosensor chip with the capability of capturing 33 different analytes from 80 μL of sample (saliva or serum). Here, we show potential biomarker signatures in both saliva and serum samples in six patient cohorts. In saliva samples, we noted occasional analyte outliers on the chip within individual samples and were able to compare those samples to 16S RNA microbiome data. These comparisons indicate differences in relative abundance of oral pathogens within those patients. Microsphere Immunoassay (MIA) of immunoglobulin isotypes was also performed on serum samples and revealed MIS-C patients had several COVID antigen-specific immunoglobulins that were significantly higher than other cohorts, thus identifying potential new targets for the second-generation biosensor chip. MIA also identified additional biomarkers for our second-generation chip, verified biomarker signatures generated on the first-generation chip, and aided in second-generation chip optimization. Interestingly, MIS-C samples from the United States had a more diverse and robust signature than the Colombian samples, which was also illustrated in the MIA cytokine data. These observations identify new MIS-C biomarkers and biomarker signatures for each of the cohorts. Ultimately, these tools may represent a potential diagnostic tool for use in the rapid identification of MIS-C.

Challenges and perspectives of multi-virus biosensing techniques: A review

In the context of globalization, individuals have an increased chance of being infected by multiple viruses simultaneously, thereby highlighting the importance of developing multiplexed devices. In addition to sufficient sensitivity and rapid response, multi-virus sensing techniques are expected to offer additional advantages including high throughput, one-time sampling for parallel analysis, and full automation with data visualization. In this paper, we review the optical, electrochemical, and mechanical platforms that enable multi-virus biosensing. The working mechanisms of each platform, including the detection principle, transducer configuration, bio-interface design, and detected signals, are reviewed. The advantages and limitations, as well as the challenges in implementing various detection strategies in real-life scenarios, were evaluated. Future perspectives on multiplexed biosensing techniques are critically discussed. Earlier access to multi-virus biosensors will efficiently serve for immediate pandemic control, such as in emerging SARS-CoV-2 and monkeypox cases.

FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America

We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.

Recent progress in nanomaterial-based sensing of airborne viral and bacterial pathogens

Airborne pathogens are small microbes that can cause a multitude of diseases (e.g., the common cold, flu, asthma, anthrax, tuberculosis, botulism, and pneumonia). As pathogens are transmitted from infected hosts via a number of routes (e.g., aerosolization, sneezing, and coughing), there is a great demand to accurately monitor their presence and behavior. Despite such need, conventional detection methods (e.g., colony counting, immunoassays, and various molecular techniques) generally suffer from a number of demerits (e.g., complex, time-consuming, and labor-intensive nature). To help overcome such limitations, nanomaterial-based biosensors have evolved as alternative candidates to realize portable, rapid, facile, and direct on-site identification of target microbes. In this review, nano-biosensors developed for the detection of airborne pathogens are listed and discussed in reference to conventional options. The prospects for the development of advanced nano-biosensors with enhanced accuracy and portability are also discussed.

Immunoassay Biosensing of Foodborne Pathogens with Surface Plasmon Resonance Imaging: A Review

Surface plasmon resonance imaging (SPRi) has been increasingly used in the label-free detections of various biospecies, such as organic toxins, proteins, and bacteria. In combination with the well-developed microarray immunoassay, SPRi has the advantages of rapid detection in tens of minutes and multiplex detection of different targets with the same biochip. Both prism-based and prism-free configurations of SPRi have been developed for highly integrated portable immunosensors, which have shown great potential on pathogen detection and living cell imaging. This review summarizes the recent advances in immunoassay biosensing with SPRi, with special emphasis on the multiplex detections of foodborne pathogens. Additionally, various spotting techniques, surface modification protocols, and signal amplification methods have been developed to improve the specificity and sensitivity of the SPRi biochip. The challenges in multiplex detections of foodborne pathogens in real-world samples are addressed, and future perspectives of miniaturizing SPRi immunosensors with nanotechnologies are discussed.

Early detection of bacteria using SPR imaging and event counting: experiments with Listeria monocytogenes and Listeria innocua

Foodborne pathogens are of significant concern in the agrifood industry and the development of associated rapid detection and identification methods are of major importance. This paper describes the novel use of resolution-optimized prism-based surface plasmon resonance imaging (RO-SPRI) and data processing for the detection of the foodborne pathogens Listeria monocytogenes and Listeria innocua. With an imaging spatial resolution on the order of individual bacteria (2.7 ± 0.5 μm × 7.9 ± 0.6 μm) over a field of view 1.5 mm2, the RO-SPRI system enabled accurate counting of individual bacteria on the sensor surface. Using this system, we demonstrate the detection of two species of Listeria at an initial concentration of 2 × 102 CFU mL-1 in less than 7 hours. The surface density of bacteria at the point of positive detection was 15 ± 4 bacteria per mm2. Our approach offers great potential for the development of fast specific detection systems based on affinity monitoring.

Selective Uropathogenic E. coli Detection Using Crossed Surface-Relief Gratings

Urinary tract infections (UTIs) are one of the major burdens on public healthcare worldwide. One of the primary causes of UTIs is the invasion of the urinary tract by uropathogenic Escherichia coli (UPEC). Improper treatment of bacterial infections like UTIs with broad-spectrum antibiotics has contributed to the rise of antimicrobial resistance, necessitating the development of an inexpensive, rapid and accurate detection of UPEC. Here, we present real-time, selective and label-free detection of UPEC using crossed surface-relief gratings (CSRGs) as nanometallic sensors incorporated into an optical sensing platform. CSRGs enable real-time sensing due to their unique surface plasmon resonance (SPR)-based light energy exchange, resulting in detection of a very-narrow-bandwidth SPR signal after the elimination of residual incident light. The platform’s sensing ability is experimentally demonstrated by the detection of bulk refractive index (RI) changes, with a bulk sensitivity of 382.2 nm/RIU and a resolution in the order of 10⁻⁶ RIU. We also demonstrate, for the first time, CSRG-based real-time selective capture and detection of UPEC in phosphate-buffered saline (PBS) solution, in clinically relevant concentrations, as opposed to other UTI-causing Gram-negative bacteria. The platform’s detection limit is calculated to be 10⁵ CFU/mL (concentration on par with the clinical threshold for UTI diagnosis), with a dynamic range spanning four orders of magnitude. This work paves the way for the development of inexpensive point-of-care diagnosis devices focusing on effective treatment of UTIs, which are a burden on public healthcare due to the rise in the number of cases and their recurrences in the recent past.

Recent strategies for the diagnosis of early Lyme disease

Lyme disease (LD) is the most common tick-borne disease in the Northern Hemisphere. As the most prevalent vector-borne disease in the USA, LD affects 300,000 human cases each year. LD is caused by inoculation of the bacterial spirochete, Borrelia burgdorferi sensu lato, from an infected tick. If not treated quickly and completely, the bacteria disseminate from the tick's biting site into multiple organs including the joints, heart, and brain. Thus, the best outcome from medical intervention can be expected with early detection and treatment with antibiotics, prior to multi-organ dissemination. In the absence of a characteristic rash, LD is diagnosed using serological testing involving enzyme-linked immunosorbent assay (ELISA) followed by western blotting, which is collectively known as the two-tier algorithm. These assays detect host antibodies against the bacteria, but are hampered by low sensitivity, which can miss early LD cases. This review discusses the application of some current assays for diagnosing LD clinically, thus providing a foundation for exploring newer techniques being developed in the laboratory for more sensitive detection of early LD.

Ultrasensitive Detection of Bacterial Protein Toxins on Patterned Microarray via Surface Plasmon Resonance Imaging with Signal Amplification by Conjugate Nanoparticle Clusters

Sensitive detection and monitoring of biological interactions in a high throughput, multiplexed array format has numerous advantages. We report here a method to enhance detection sensitivity in surface plasmon resonance (SPR) spectroscopy and SPR imaging via the effect of accumulation of conjugated nanoparticles of varying sizes. Bacterial cholera toxin (CT) was chosen for the demonstration of enhanced immunoassay by SPR. After immobilization of CT on a gold surface, specific recognition is achieved by biotinylated anti-CT. The signal is amplified by the attachment of biotinylated 20 nm AuNP via streptavidin bridge, followed by attachment of 5 nm streptavidin-functionalized Fe₃O₄NP to the AuNP-biotin surface. The continuous surface binding of two differently sized conjugated nanoparticles effectively increases their packing density on surface and significantly improves SPR detection sensitivity, allowing quantitative measurement of CT at very low concentration. The dense packing of conjugated nanoparticles on the surface was confirmed by atomic force microscopy characterization. SPR imaging of the immunoassay for high-throughput analysis utilized an Au-well microarray that attenuated the background resonance interference on the resulting images. A calibration curve of conjugated nanoparticle binding signal amplification for CT detection based on surface coverage has been obtained that shows a correlation in a range from 6.31 × 10^-16 to 2.51 × 10^-13 mol/cm² with the limit of detection of 5.01 × 10^-16 mol/cm². The absolute quantity of detection limit using SPR imaging was 0.25 fmol. The versatile nanoparticles and biotin-streptavidin interaction used here should allow adaptation of this enhancement method to many other systems that include DNA, RNA, peptides, and carbohydrates, opening new avenues for ultrasensitive analysis of biomolecules.

Detection of bacterial contamination in food matrices by integration of quorum sensing in a paper-strip test

There are an estimated 48 million cases of foodborne illness in the United States every year. In general, these illnesses are the result of unintentional contamination and improper food handling. Because bacterial contamination plays a major role in food spoilage and, hence, in foodborne illnesses, it is important to design easy, portable methods to detect bacteria in food. Quorum sensing (QS) enables bacteria to communicate with one another and by doing so they can modulate their behavior in a cell-density dependent manner. In bacteria, quorum sensing molecules (QSMs) are known to control several factors such as virulence factor production, antibiotic production, biofilm formation, and gene regulation. Herein, we demonstrate the applicability of whole cell biosensing systems for the early identification of food contamination via detection of QSMs. Additionally, we have developed a portable system for detection of bacterial contamination using microdots of immobilized whole cell-based biosensors on paper that boast nanomolar level detection of QSMs in two different food matrices, namely beef and milk. Limits of detection ranged from 1 × 10-7 M to 1 × 10-9 M with relative standard deviations (RSDs) of 1-16%. This rapid, easy, and portable test could be a useful tool for use in the field and during all stages of food manipulation, i.e., from farms to distribution, storage, sales, and preparation prior to consumption, to ensure that food is free of bacterial contamination.

Biosensor for the detection of Listeria monocytogenes: emerging trends

The early detection of Listeria monocytogenes (L. monocytogenes) and understanding the disease burden is of paramount interest. The failure to detect pathogenic bacteria in the food industry may have terrible consequences, and poses deleterious effects on human health. Therefore, integration of methods to detect and trace the route of pathogens along the entire food supply network might facilitate elucidation of the main contamination sources. Recent research interest has been oriented towards the development of rapid and affordable pathogen detection tools/techniques. An innovative and new approach like biosensors has been quite promising in revealing the foodborne pathogens. In spite of the existing knowledge, advanced research is still needed to substantiate the expeditious nature and sensitivity of biosensors for rapid and in situ analysis of foodborne pathogens. This review summarizes recent developments in optical, piezoelectric, cell-based, and electrochemical biosensors for Listeria sp. detection in clinical diagnostics, food analysis, and environmental monitoring, and also lists their drawbacks and advantages.

Analysis of Multiplexed Nanosensor Arrays Based on Near-Infrared Fluorescent Single-Walled Carbon Nanotubes

The high-throughput, label-free detection of biomolecules remains an important challenge in analytical chemistry with the potential of nanosensors to significantly increase the ability to multiplex such assays. In this work, we develop an optical sensor array, printable from a single-walled carbon nanotube/chitosan ink and functionalized to enable a divalent ion-based proximity quenching mechanism for transducing binding between a capture protein or an antibody with the target analyte. Arrays of 5 × 6, 200 μm near-infrared (nIR) spots at a density of ≈300 spots/cm² are conjugated with immunoglobulin-binding proteins (proteins A, G, and L) for the detection of human IgG, mouse IgM, rat IgG2a, and human IgD. Binding kinetics are measured in a parallel, multiplexed fashion from each sensor spot using a custom laser scanning imaging configuration with an nIR photomultiplier tube detector. These arrays are used to examine cross-reactivity, competitive and nonspecific binding of analyte mixtures. We find that protein G and protein L functionalized sensors report selective responses to mouse IgM on the latter, as anticipated. Optically addressable platforms such as the one examined in this work have potential to significantly advance the real-time, multiplexed biomolecular detection of complex mixtures.

Fluorescence-Free Biosensor Methods in Detection of Food Pathogens with a Special Focus on Listeria monocytogenes

Food pathogens contaminate food products that allow their growth on the shelf and also under refrigerated conditions. Therefore, it is of utmost importance to lower the limit of detection (LOD) of the method used and to obtain the results within hours to few days. Biosensor methods exploit the available technologies to individuate and provide an approximate quantification of the bacteria present in a sample. The main bottleneck of these methods depends on the aspecific binding to the surfaces and on a change in sensitivity when bacteria are in a complex food matrix with respect to bacteria in a liquid food sample. In this review, we introduce surface plasmon resonance (SPR), new advancements in SPR techniques, and electrochemical impedance spectroscopy (EIS), as fluorescence-free biosensing technologies for detection of L. monocytogenes in foods. The application of the two methods has facilitated L. monocytogenes detection with LOD of 1 log CFU/mL. Further advancements are envisaged through the combination of biosensor methods with immunoseparation of bacteria from larger volumes, application of lab-on-chip technologies, and EIS sensing methods for multiplex pathogen detection. Validation efforts are being conducted to demonstrate the robustness of detection, reproducibility and variability in multi-site installations.

Paper-based magnetic nanoparticle-peptide probe for rapid and quantitative colorimetric detection of Escherichia coli O157:H7

There is a critical and urgent demand for a simple, rapid and specific qualitative and quantitative colorimetric biosensor for the detection of the food contaminant Escherichia coli O157:H7 (E. coli O157:H7) in complex food products due to the recent outbreaks of food-borne diseases. Traditional detection techniques are time-consuming, require expensive instrumentation and are labour-intensive. To overcome these limitations, a novel, ultra-rapid visual biosensor was developed based on the ability of E. coli O157:H7 proteases to change the optical response of a surface-modified, magnetic nanoparticle-specific (MNP-specific) peptide probe. Upon proteolysis, a gradual increase in the golden color of the sensor surface was visually observed. The intensification of color was correlated with the E. coli O157:H7 concentration. The color change resulting from the dissociation of the self-assembled monolayer (SAM) was detected by the naked eye and analysed using an image analysis software (ImageJ) for the purpose of quantitative detection. This biosensor demonstrated high sensitivity and applicability, with lower limits of detection of 12CFUmL-1 in broth samples and 30-300CFUmL-1 in spiked complex food matrices. In conclusion, this approach permits the use of a disposable biosensor chip that can be mass-produced at low cost and can be used not only by food manufacturers but also by regulatory agencies for better control of potential health risks associated with the consumption of contaminated foods.

Integration of Curved D-Type Optical Fiber Sensor with Microfluidic Chip

A curved D-type optical fiber sensor (OFS) combined with a microfluidic chip is proposed. This OFS, based on surface plasmon resonance (SPR) of the Kretchmann’s configuration, is applied as a biosensor to measure the concentrations of different bio-liquids such as ethanol, methanol, and glucose solutions. The SPR phenomenon is attained by using the optical fiber to guide the light source to reach the side-polished, gold-coated region. Integrating this OFS with a polymethylmethacrylate (PMMA)-based microfluidic chip, the SPR spectra for liquids with different refractive indices are recorded. Experimentally, the sensitivity of the current biosensor was calculated to be in the order of 10⁻⁵ RIU. This microfluidic chip-integrated OFS could be valuable for monitoring subtle changes in biological samples such as blood sugar, allergen, and biomolecular interactions.

Recent advances in M13 bacteriophage-based optical sensing applications

Recently, M13 bacteriophage has started to be widely used as a functional nanomaterial for various electrical, chemical, or optical applications, such as battery components, photovoltaic cells, sensors, and optics. In addition, the use of M13 bacteriophage has expanded into novel research, such as exciton transporting. In these applications, the versatility of M13 phage is a result of its nontoxic, self-assembling, and specific binding properties. For these reasons, M13 phage is the most powerful candidate as a receptor for transducing chemical or optical phenomena of various analytes into electrical or optical signal. In this review, we will overview the recent progress in optical sensing applications of M13 phage. The structural and functional characters of M13 phage will be described and the recent results in optical sensing application using fluorescence, surface plasmon resonance, Förster resonance energy transfer, and surface enhanced Raman scattering will be outlined.

Enhancement and control of surface plasmon resonance sensitivity using grating in conical mounting configuration

In this work we propose a method to enhance and control the angular sensitivity of a grating coupled surface plasmon resonance (GCSPR) sensor. We lighted a silver grating, mounted in conical configuration, with a laser source and we measured the transmittance of the grating as a function of the azimuthal angle. To evaluate the sensitivity, grating surface was functionalized with four different alkanethiol self assembled monolayers (SAM) and the correspondent azimuthal transmittance peak shifts were measured. The sensitivity control was performed by simply change the light incident angle. This method offers the possibility to design dynamic GCSPR sensor benches that can be used to amplify the SPR angle shift at any step of a biological detection process.

Biosensors for the Detection of Food Pathogens

Food pathogens frequently cause foodborne diseases. There is a need to rapidly identify the source of the bacteria in order to contain their spread and epidemics. A pre-enrichment culture or a direct culture on agar plate are standard microbiological methods. In this review, we present an update on alternative molecular methods to nucleic acid-based detection for species identification. Biosensor-based methods rely on the recognition of antigen targets or receptors by antibodies, aptamers or high-affinity ligands. The captured antigens may be then directly or indirectly detected through an antibody or high-affinity and high-specificity recognition molecule. Various different detection methods are discussed, from label-free sensors and immunosensors to fluorescence-based ones. Each method shows advantages and disadvantages in terms of equipment, sensitivity, simplicity and cost-effectiveness. Finally, lab-on-a-chip (LOC) devices are introduced briefly, with the potential to be fast, sensitive and useful for on-site bacteria detection in food processing laboratories to check potential contamination by sample monitoring combined with a rapid pre-enrichment step.

Sensitivity enhancement of a grating-based surface plasmon-coupled emission (SPCE) bionsor chip using gold thickness

We describe a novel approach to enhance the sensitivity of a grating-based surface plasmon-coupled emission (SPCE) sensor by increasing the thickness of the metal film used in this system. The calculated optical properties of grating-based SPR spectra were significantly affected by both grating depth and by gold thickness. Higher angular sensitivity could be achieved at short wavelengths and under in situ measurement (analysis under aqueous condition). We confirmed the predicated enhancements of SPCE response using Alexa Fluor 647-labeled anti-mouse IgG immobilized on the SPCE sensor chips. Grating-coupled SPCE sensor chips can be used as a useful tool for high contents analysis of chemical and biomolecular interactions.

Development of a virus concentration method using lanthanum-based chemical flocculation coupled with modified membrane filtration procedures

Direct membrane filtration is often used to concentrate viruses in water but it may suffer from severe membrane fouling and clogging. Here, a lanthanum-based flocculation method coupled with modified membrane filtration procedures was developed and evaluated to detect viruses in large volume (40 L) water samples. The lanthanum-based flocculation method could easily reduce the water sample volume by a factor of 40. Additional volume reduction was achieved by a two-step membrane filtration approach. First, selected membrane filters (including 1MDS electropositive filters and nitrocellulose electronegative filters-Millipore HATF filters) were used to reduce water sample volume further and compare their efficiencies in virus recovery. The Mg²⁺-modified HATF membrane performed better on MS2 retention with an average virus recovery of 83.4% (±4.5% [standard deviation]). After HATF membrane filtration and elution, centrifugal ultrafiltration through a 30 kDa cut-off membrane resulted in an overall concentration factor of 20,000. Results from the infectivity assay showed that the MS2 recovery efficiencies from the NanoCeram- and 1MDS-based direct filtration and the lanthanum-based concentration coupled with the modified filtration procedure were 10.1% (±1.0%), 3.3% (±0.1%), and 17.5% (±1.1%), respectively. Results from the PCR analysis showed that the virus recoveries of the lanthanum-based method were 20.6% (±2.9%) and 19.5% (±3.4%) for MS2 and adenovirus, respectively, while no adenovirus could be detected through the NanoCeram- and 1MDS-based direct filtration. The lanthanum-based concentration method coupled with modified membrane filtration procedures is therefore a promising method for detecting waterborne viruses.

Cloning and characterization of a hybridoma secreting a 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-specific monoclonal antibody and recombinant F(ab)

Smokeless tobacco products have been associated with increased risks of oro-pharyngeal cancers, due in part to the presence of tobacco-specific nitrosamines (TSNAs) such as 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). These potent carcinogens are formed during tobacco curing and as a result of direct nitrosation reactions that occur in the oral cavity. In the current work we describe the isolation and characterization of a hybridoma secreting a high-affinity, NNK-specific monoclonal antibody. A structurally-related benzoyl derivative was synthesized to facilitate coupling to NNK-carrier proteins, which were characterized for the presence of the N-nitroso group using the Griess reaction, and used to immunize BALB/c mice. Splenocytes from mice bearing NNK-specific antibodies were used to create hybridomas. Out of four, one was selected for subcloning and characterization. Approximately 99% of the monoclonal antibodies from this clone were competitively displaced from plate-bound NNKB conjugates in the presence of free NNK. The affinity of the monoclonal antibody to the NNKB conjugates was Kd = 2.93 nM as determined by surface plasmon resonance. Free nicotine was a poor competitor for the NNKB binding site. The heavy and light chain antibody F(ab) fragments were cloned, sequenced and inserted in tandem into an expression vector, with an FMDV Furin 2A cleavage site between them. Expression in HEK 293 cells revealed a functional F(ab) with similar binding features to that of the parent hybridoma. This study lays the groundwork for synthesizing transgenic tobacco that expresses carcinogen-sequestration properties, thereby rendering it less harmful to consumers.

Mining the salivary proteome with grating-coupled surface plasmon resonance imaging and surface plasmon coupled emission microarrays

Biological indicators have numerous and widespread utility in personalized medicine, but the measurement of these indicators also poses many technological and practical challenges. Blood/plasma has typically been used as the sample source with which to measure these indicators, but the invasiveness associated with sample procurement has led to increased interest in saliva as an attractive alternative. However, there are unique issues associated with the measurement of saliva biomarkers. These issues are compounded by the imperfect correlation between saliva and plasma with respect to biomarker profiles. In this manuscript, we address the technical challenges associated with saliva biomarker quantification. We describe a high-content microarray assay that employs both grating-coupled surface plasmon resonance imaging and surface plasmon-coupled emission modalities in a highly sensitive assay with a large dynamic range. This powerful approach provides the tools to map the proteome of saliva, which in turn should greatly enhance the utility of salivary biomarker profiles in personalized medicine.