Screening of biochemical interactions becomes simpler, less expensive, and more accurate when labels, such as fluorescent dyes, radioactive markers, and colorimetric reactions, are not required to quantify detected material. SRU Biosystems has developed a biosensor technology that is manufactured on continuous sheets of plastic film and incorporated into standard microplates and microarray slides to enable label-free assays to be performed with high throughput, high sensitivity, and low cost per assay. The biosensor incorporates a narrowband guided-mode resonance reflectance filter, in which the reflected color is modulated by the attachment/detachment of biochemical material to the surface. The technology offers 4 orders of linear dynamic range and uniformity within a plate, with a coefficient of variation of 2.5%. Using conventional biochemical immobilization surface chemistries, a wide range of assay applications are enabled. Small molecule screening, cell proliferation/ cytotoxicity, enzyme activity screening, protein-protein interaction, and cell membrane receptor expression are among the applications demonstrated. (Journal of Biomolecular Screening 2004:481-490)

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This review describes a new type of label-free optical biosensor that is inexpensively manufactured from continuous sheets of plastic film and incorporated into standard format microplates to enable highly sensitive, high-throughput detection of small molecules, proteins and cells. The biosensor and associated detection instrumentation are applied to review two fundamental limiting issues for assays in proteomics research and drug discovery: requirement for quantitative measurement of protein concentration and specific activity, and measurements made with complex systems in highly parallel measurements. SRU BIosystems, Inc.'s BIND label-free detection will address these issues using data examples for hybridoma screening, epitope binning and mapping, small-molecule screening, and cell-based functional assays. The review describes several additional applications that are under development for the system, and the key issues that will drive adoption of the technology over the next 5 years.

The iron responsive element (IRE) is a conserved RNA structure that is found in the 5' UTR of ferritin mRNA and in the 3' UTR of transferrin receptor mRNA. It is the binding site of the iron responsive protein (IRP), and the interaction is part of the regulation of cellular iron metabolism. The IRE six-nucleotide hairpin loop, 5'C1A2G3U4G5N6, is conserved in sequence, and mutations have shown that it is required for IRP binding. On the basis of the thermodynamic and NMR experiments utilized here, the IRE loop structure 5'C1A2G3U4G5C6, is described in detail. Measurements of loop stability show that it has 2.9 kcal/mol more free energy than predicted. NMR data suggest that there is hydrogen bonding between C1 and G5 in a tertiary interaction across the loop. A model structure, produced by MC-SYM/energy minimization, illustrates the conformational flexibility of U4 and C6, which appear to exhibit considerable local motion in solution. NMR data indicate that the position of G3 is not well defined, leading to two families of loop structures.

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BackgroundApproximately 18–20% of all human breast cancers have overexpressed human epidermal growth factor receptor 2 (HER2). Standard clinical practice is to treat only overexpressed HER2 (HER2+) cancers with targeted anti-HER2 therapies. However, recent analyses of clinical trial data have found evidence that HER2-targeted therapies may benefit a sub-group of breast cancer patients with non-overexpressed HER2. This suggests that measurement of other biological factors associated with HER2 cancer, such as HER2 signaling pathway activity, should be considered as an alternative means of identifying patients eligible for HER2 therapies.MethodsA new biosensor-based test (CELxTM HSF) that measures HER2 signaling activity in live cells is demonstrated using a set of 19 human HER2+ and HER2– breast cancer reference cell lines and primary cell samples derived from two fresh patient tumor specimens. Pathway signaling is elucidated by use of highly specific agonists and antagonists. The test method relies upon well-established phenotypic, adhesion-related, impedance changes detected by the biosensor.ResultsThe analytical sensitivity and analyte specificity of this method was demonstrated using ligands with high affinity and specificity for HER1 and HER3. The HER2-driven signaling quantified ranged 50-fold between the lowest and highest cell lines. The HER2+ cell lines were almost equally divided into high and low signaling test result groups, suggesting that little correlation exists between HER2 protein expression and HER2 signaling level. Unexpectedly, the highest HER2-driven signaling level recorded was with a HER2– cell line.ConclusionsMeasurement of HER2 signaling activity in the tumor cells of breast cancer patients is a feasible approach to explore as a biomarker to identify HER2-driven cancers not currently diagnosable with genomic techniques. The wide range of HER2-driven signaling levels measured suggests it may be possible to make a distinction between normal and abnormal levels of activity. Analytical validation studies and clinical trials treating HER2- patients with abnormal HER2-driven signaling would be required to evaluate the analytical and clinical validity of using this functional biomarker as a diagnostic test to select patients for treatment with HER2 targeted therapy. In clinical practice, this method would require patient specimens be delivered to and tested in a central lab.Electronic supplementary materialThe online version of this article (doi:10.1186/s12885-017-3181-0) contains supplementary material, which is available to authorized users.

Microplate-based optical biosensors are enabling a variety of cell-based assays, inhibition assays, protein-protein binding assays and protein-small molecule binding assays to be performed with high-throughput and high sensitivity.