A lateral electrophoretic flow diagnostic assay

Immunochromatographic assays are a cornerstone tool in disease screening. To complement existing lateral flow assays (based on wicking flow) we introduce a lateral flow format that employs directed electrophoretic transport. The format is termed a “lateral e-flow assay” and is designed to support multiplexed detection using immobilized reaction volumes of capture antigen. To fabricate the lateral e-flow device, we employ mask-based UV photopatterning to selectively immobilize unmodified capture antigen along the microchannel in a barcode-like pattern. The channel-filling polyacrylamide hydrogel incorporates a photoactive moiety (benzophenone) to immobilize capture antigen to the hydrogel without a priori antigen modification. We report a heterogeneous sandwich assay using low-power electrophoresis to drive biospecimen through the capture antigen barcode. Fluorescence barcode readout is collected via a low-resource appropriate imaging system (CellScope). We characterize lateral e-flow assay performance and demonstrate a serum assay for antibodies to the hepatitis C virus (HCV). In a pilot study, the lateral e-flow assay positively identifies HCV+ human sera in 60 min. The lateral e-flow assay provides a flexible format for conducting multiplexed immunoassays relevant to confirmatory diagnosis in near-patient settings

Microfluidic barcode assay for antibody-based confirmatory diagnostics.

Confirmatory diagnostics offer high clinical sensitivity and specificity typically by assaying multiple disease biomarkers. Employed in clinical laboratory settings, such assays confirm a positive screening diagnostic result. These important multiplexed confirmatory assays require hours to complete. To address this performance gap, we introduce a simple 'single inlet, single outlet' microchannel architecture with multiplexed analyte detection capability. A streptavidin-functionalized, channel-filling polyacrylamide gel in a straight glass microchannel operates as a 3D scaffold for a purely electrophoretic yet heterogeneous immunoassay. Biotin and biotinylated capture reagents are patterned in discrete regions along the axis of the microchannel resulting in a barcode-like pattern of reagents and spacers. To characterize barcode fabrication, an empirical study of patterning behaviour was conducted across a range of electromigration and binding reaction timescales. We apply the heterogeneous barcode immunoassay to detection of human antibodies against hepatitis C virus and human immunodeficiency virus antigens. Serum was electrophoresed through the barcode patterned gel, allowing capture of antibody targets. We assess assay performance across a range of Damkohler numbers. Compared to clinical immunoblots that require 4-10 h long sample incubation steps with concomitant 8-20 h total assay durations; directed electromigration and reaction in the microfluidic barcode assay leads to a 10 min sample incubation step and a 30 min total assay duration. Further, the barcode assay reports clinically relevant sensitivity (25 ng ml(-1) in 2% human sera) comparable to standard HCV confirmatory diagnostics. Given the low voltage, low power and automated operation, we see the streamlined microfluidic barcode assay as a step towards rapid confirmatory diagnostics for a low-resource clinical laboratory setting

Microfluidic Validation of Diagnostic Protein Markers for Spontaneous Cerebrospinal Fluid Rhinorrhea

Cerebrospinal fluid (CSF) rhinorrhea is a potentially dangerous condition identified by CSF leakage into the nasal cavity. This malady stands to benefit from rapid and noninvasive screening diagnostics to complement low-throughput imaging based methods currently in use. To address this gap, we demonstrate on-chip immunosubtraction to accelerate biomarker validation and immunoassay development for a putative CSF rhinorrhea diagnostic marker, transthyretin, by combining high-specificity immunoaffinity capture with subsequent polyacrylamide gel electrophoresis (PAGE). We demonstrate the on-chip assay using photopatterned polyacrylamide immunofilters. The filter consists of polymer with controlled pore-sizes to size-exclude (i.e., “subtract”) large antibody-target immune complexes from downstream PAGE separation. A control PAGE separation is also performed for comparison without immunoaffinity capture (i.e., no antibody present). We compare on-chip immunosubtraction to Western blotting and ELISA to validate CSF rhinorrhea biomarkers from nasal surgery samples. For samples representative of spontaneous rhinorrhea, the 5 min on-chip assay achieved clinical specificity of 100%, compared to 50% for ELISA which required 6 h. On-chip immunosubtraction also generated results for clinical samples not assayable via ELISA due to matrix protein spurious signals. The pilot study suggests the capability of a rapid on-chip validation tool to expedite scrutiny of putative protein markers for new clinical assays

Microfluidic Validation of Diagnostic Protein Markers for Spontaneous Cerebrospinal Fluid Rhinorrhea

Cerebrospinal fluid (CSF) rhinorrhea is a potentially dangerous condition identified by CSF leakage into the nasal cavity. This malady stands to benefit from rapid and noninvasive screening diagnostics to complement low-throughput imaging based methods currently in use. To address this gap, we demonstrate on-chip immunosubtraction to accelerate biomarker validation and immunoassay development for a putative CSF rhinorrhea diagnostic marker, transthyretin, by combining high-specificity immunoaffinity capture with subsequent polyacrylamide gel electrophoresis (PAGE). We demonstrate the on-chip assay using photopatterned polyacrylamide immunofilters. The filter consists of polymer with controlled pore-sizes to size-exclude (i.e., “subtract”) large antibody-target immune complexes from downstream PAGE separation. A control PAGE separation is also performed for comparison without immunoaffinity capture (i.e., no antibody present). We compare on-chip immunosubtraction to Western blotting and ELISA to validate CSF rhinorrhea biomarkers from nasal surgery samples. For samples representative of spontaneous rhinorrhea, the 5 min on-chip assay achieved clinical specificity of 100%, compared to 50% for ELISA which required 6 h. On-chip immunosubtraction also generated results for clinical samples not assayable via ELISA due to matrix protein spurious signals. The pilot study suggests the capability of a rapid on-chip validation tool to expedite scrutiny of putative protein markers for new clinical assays

Microfluidic Screening of Electrophoretic Mobility Shifts Elucidates Riboswitch Binding Function

Riboswitches are RNA sensors that change conformation upon binding small molecule metabolites, in turn modulating gene expression. Our understanding of riboswitch regulatory function would be accelerated by a high throughput, quantitative screening tool capable of measuring riboswitch-ligand binding. We introduce a microfluidic mobility shift assay that enables precise and rapid quantitation of ligand binding and subsequent riboswitch conformational change. In 0.3% of the time required for bench top assays (3.2 min vs. 1020 min), we screen and validate five candidate SAM-I riboswitches isolated from thermophilic and cryophilic bacteria. The format offers enhanced resolution of conformational change compared to slab gel formats, quantitation and repeatability for statistical assessment of small mobility shifts, low reagent consumption, and riboswitch characterization without modification of the aptamer structure. Appreciable analytical sensitivity coupled with high resolution separation performance allows quantitation of equilibrium dissociation constants (K(d)) for both rapidly and slowly interconverting riboswitch-ligand pairs as validated through experiments and modeling. Conformational change, triplicate mobility shift measurements, and K(d) are reported for both a known and a candidate SAM-I riboswitch with comparison to in-line probing assay results. The microfluidic mobility shift assay establishes a scalable format for the study of riboswitch-ligand binding that will advance the discovery and selection of novel riboswitches and the development of antibiotics to target bacterial riboswitches

Chemical composition and antibacterial activity of Gongronema latifolium

Chemical composition of Gongronema latifolium leaves was determined using standard methods. Aqueous and methanol G. latifolium extracts were tested against thirteen pathogenic bacterial isolates. Crude protein, lipid extract, ash, crude fibre and nitrogen free extractives obtained are: 27.2%, 6.07%, 11.6%, 10.8% and 44.3% dry matter respectively. Potassium, sodium, calcium, phosphorus and cobalt contents are 332, 110, 115, 125 and 116 mg/kg respectively. Dominant essential amino acids are leucine, valine and phenylalanine. Aspartic acid, glutamic acid and glycine are 13.8%, 11.9% and 10.3% respectively of total amino acid. Saturated and unsaturated fatty acids are 50.2% and 39.4% of the oil respectively. Palmitic acid makes up 36% of the total fatty acid. Extracts show no activity against E. faecalis, Y. enterolytica, E. aerogenes, B. cereus and E. agglomerans. Methanol extracts were active against S. enteritidis, S. cholerasius ser typhimurium and P. aeruginosa (minimum inhibitory concentration (MIC) 1 mg; zone of growth inhibition 7, 6.5 and 7 mm respectively). Aqueous extracts show activity against E. coli (MIC 5 mg) and P. aeruginosa (MIC 1 mg) while methanol extracts are active against P. aeruginosa and L. monocytogenes. G. latifolium has potential food and antibacterial uses