Label-Free Assays on the BIND System

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 narrow band 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.

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Colorimetric Sensing with Gold Nanoparticles on Electrowetting-Based Digital Microfluidics

Micromachines ◽

10.3390/mi12111423 ◽

2021 ◽

Vol 12 (11) ◽

pp. 1423

Author(s):

Zhen Gu ◽

Jing-Jing Luo ◽

Le-Wei Ding ◽

Bing-Yong Yan ◽

Jia-Le Zhou ◽

...

Keyword(s):

Gold Nanoparticles ◽

Low Cost ◽

Digital Microfluidics ◽

High Sensitivity ◽

Bulk Solution ◽

Label Free ◽

Colorimetric Sensing ◽

Wide Range ◽

The Stability ◽

Digital Microfluidic

Digital microfluidic (DMF) has been a unique tool for manipulating micro-droplets with high flexibility and accuracy. To extend the application of DMF for automatic and in-site detection, it is promising to introduce colorimetric sensing based on gold nanoparticles (AuNPs), which have advantages including high sensitivity, label-free, biocompatibility, and easy surface modification. However, there is still a lack of studies for investigating the movement and stability of AuNPs for in-site detection on the electrowetting-based digital microfluidics. Herein, to demonstrate the ability of DMF for colorimetric sensing with AuNPs, we investigated the electrowetting property of the AuNPs droplets on the hydrophobic interface of the DMF chip and examined the stability of the AuNPs on DMF as well as the influence of evaporation to the colorimetric sensing. As a result, we found that the electrowetting of AuNPs fits to a modified Young–Lippmann equation, which suggests that a higher voltage is required to actuate AuNPs droplets compared with actuating water droplets. Moreover, the stability of AuNPs was maintained during the processing of electrowetting. We also proved that the evaporation of droplets has a limited influence on the detections that last several minutes. Finally, a model experiment for the detection of Hg2+ was carried out with similar results to the detections in bulk solution. The proposed method can be further extended to a wide range of AuNPs-based detection for label-free, automatic, and low-cost detection of small molecules, biomarkers, and metal ions.

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Nanotechnology in emerging liquid biopsy applications

Nano Convergence ◽

10.1186/s40580-021-00263-w ◽

2021 ◽

Vol 8 (1) ◽

Author(s):

Despina P. Kalogianni

Keyword(s):

Liquid Biopsy ◽

Dynamic Range ◽

Low Cost ◽

Invasive Procedure ◽

High Sensitivity ◽

Attractive Alternative ◽

Sample Collection ◽

Comprehensive Overview ◽

Early Cancer Diagnosis ◽

Wide Range

AbstractLiquid biopsy is considered as the most attractive alternative to traditional tissue biopsies. The major advantages of this approach lie in the non-invasive procedure, the rapidness of sample collection and the potential for early cancer diagnosis and real-time monitoring of the disease and the treatment response. Nanotechnology has dynamically emerged in a wide range of applications in the field of liquid biopsy. The benefits of using nanomaterials for biosensing include high sensitivity and detectability, simplicity in many cases, rapid analysis, the low cost of the analysis and the potential for portability and personalized medicine. The present paper reports on the nanomaterial-based methods and biosensors that have been developed for liquid biopsy applications. Most of the nanomaterials used exhibit great analytical performance; moreover, extremely low limits of detection have been achieved for all studied targets. This review will provide scientists with a comprehensive overview of all the nanomaterials and techniques that have been developed for liquid biopsy applications. A comparison of the developed methods in terms of detectability, dynamic range, time-length of the analysis and multiplicity, is also provided.

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Label-Free Fluorescent Aptasensor for Small Targets via Displacement of Groove Bound Curcumin Molecules

Sensors ◽

10.3390/s19194181 ◽

2019 ◽

Vol 19 (19) ◽

pp. 4181 ◽

Cited By ~ 3

Author(s):

Baraa J. Alyamani ◽

Omar A. Alsager ◽

Mohammed Zourob

Keyword(s):

Small Molecules ◽

Dynamic Range ◽

Fluorescent Sensor ◽

Low Cost ◽

High Sensitivity ◽

Synthetic Dyes ◽

Label Free ◽

Target Molecule ◽

Small Targets ◽

Aptamer Sequence

Signal transduction based on fluorescence is one of the most common optical aptasensors for small molecules. Sensors with a number of unique features including high sensitivity, low cost, and simple operation can be constructed easily. However, the label-free fluorescent approach is limited to synthetic dyes that bind strongly to the aptamer sequence and result in a diminished sensor operation with high detection limits. In this study, we report the use of curcumin as a fluorescent probe to signal aptamer/small target binding events. A substantial enhancement in curcumin’s fluorescent emission was observed when bound into the grooves of vitamin D3 (VTD3) binding aptamer, as an example. However, the introduction of the target molecule causes the aptamer to undergo a conformational change that favors complexing the target molecule over binding the curcumin dye. The sensor was able to detect VTD3 down to 1 fM concentration in buffer solutions and extracted blood samples, operate at a wide dynamic range, and discriminate against potential biological interfering molecules including VTD2. The operation of the curcumin based fluorescent sensor is at least six orders of magnitude more sensitive than a VTD3 sensor constructed with the synthetic dye SYBR Green I. The generality of the reported label-free approach was applied with a previously isolated 75-mer bisphenol-A (BPA) aptamer, confirming that the reported sensing strategy is not confined on a particular aptamer sequence. Our work not only reports a novel sensor format for the detection of small molecules, but also serves fluorescent sensor’s most pressing need being novel fluorophores for multiplex targets detection.

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Integrating high-performing electrochemical transducers in lateral flow assay

Analytical and Bioanalytical Chemistry ◽

10.1007/s00216-021-03301-y ◽

2021 ◽

Author(s):

Antonia Perju ◽

Nongnoot Wongkaew

Keyword(s):

High Performance ◽

Point Of Care ◽

Low Cost ◽

High Sensitivity ◽

Lateral Flow ◽

Analytical Performance ◽

Label Free ◽

High Performing ◽

Lateral Flow Assays ◽

Electrochemical Transducers

AbstractLateral flow assays (LFAs) are the best-performing and best-known point-of-care tests worldwide. Over the last decade, they have experienced an increasing interest by researchers towards improving their analytical performance while maintaining their robust assay platform. Commercially, visual and optical detection strategies dominate, but it is especially the research on integrating electrochemical (EC) approaches that may have a chance to significantly improve an LFA’s performance that is needed in order to detect analytes reliably at lower concentrations than currently possible. In fact, EC-LFAs offer advantages in terms of quantitative determination, low-cost, high sensitivity, and even simple, label-free strategies. Here, the various configurations of EC-LFAs published are summarized and critically evaluated. In short, most of them rely on applying conventional transducers, e.g., screen-printed electrode, to ensure reliability of the assay, and additional advances are afforded by the beneficial features of nanomaterials. It is predicted that these will be further implemented in EC-LFAs as high-performance transducers. Considering the low cost of point-of-care devices, it becomes even more important to also identify strategies that efficiently integrate nanomaterials into EC-LFAs in a high-throughput manner while maintaining their favorable analytical performance.

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Airborne fine-resolution UHF radar: an approach to the study of englacial reflections, firn compaction and ice attenuation rates

Journal of Glaciology ◽

10.3189/2015jog14j089 ◽

2015 ◽

Vol 61 (225) ◽

pp. 89-100 ◽

Cited By ~ 12

Author(s):

Cameron Lewis ◽

Sivaprasad Gogineni ◽

Fernando Rodriguez-Morales ◽

Ben Panzer ◽

Theresa Stumpf ◽

...

Keyword(s):

Dynamic Range ◽

High Sensitivity ◽

Ultra Wideband ◽

West Antarctica ◽

Ice Shelves ◽

Ross Ice Shelf ◽

Transmission Coefficients ◽

Ice Surface ◽

Wide Range ◽

Fine Resolution

AbstractWe have built and operated an ultra-wideband UHF pulsed-chirp radar for measuring firn stratigraphy from airborne platforms over the ice sheets of Greenland and West Antarctica. Our analysis found a wide range of capabilities, including imaging of post firn–ice transition horizons and sounding of shallow glaciers and ice shelves. Imaging of horizons to depths exceeding 600 m was possible in the colder interior regions of the ice sheet, where scattering from the ice surface and inclusions was minimal. The radar’s high sensitivity and large dynamic range point to loss tangent variations as the dominant mechanism for these englacial reflective horizons. The radar is capable of mapping interfaces with reflection coefficients as low as −80 dB near the firn–ice transition and as low as −64 dB at depths of 600 m. We found that firn horizon reflectivity strongly mirrored density variance, a result of the near-unity interfacial transmission coefficients. Zones with differing compaction mechanisms were also apparent in the data. We were able to sound many ice shelves and areas of shallow ice. We estimated ice attenuation rates for a few locations, and our attenuation estimates for the Ross Ice Shelf, West Antarctica, appear to agree well with earlier reported results.

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A Label-Free Fluorescent AND Logic Gate Aptasensor for Carbohydrate Antigen 15-3 Detection Based on Graphene Oxide

Combinatorial Chemistry & High Throughput Screening ◽

10.2174/1386207324666210216095053 ◽

2021 ◽

Vol 24 ◽

Author(s):

Wenxiao Hu ◽

Yafei Dong ◽

Luhui Wang ◽

Yue Wang ◽

Mengyao Qian ◽

...

Keyword(s):

Fluorescent Dyes ◽

Logic Gate ◽

High Sensitivity ◽

Carbohydrate Antigen ◽

Fluorescence Signal ◽

Label Free ◽

Molecular Logic ◽

Long Stem ◽

Middle Ring ◽

Fluorescent Aptasensor

Background: Molecular logic gate always used fluorescent dyes to realize fluorescence signal. The labeling of the fluorophore is relatively expensive, low yield and singly labeled impuritiesaffects the affinity between the target and the aptamer. Label-free fluorescent aptamer biosensor strategy has attracted widespread interest due to lower cost and simple. Objective: Herein, we have designed a AND logic gate fluorescent aptasensor for detecting carbohydrate antigen 15-3(CA15-3) based on label-free fluorescence signal output. Materials and Methods: A hairpin DNA probe consists of CA15-3 aptamer and partly anti-CA15-3 aptamer sequences as a long stem and G-rich sequences of the middle ring as a quadruplex-forming oligomer. G-rich sequences can fold into a quadruplex by K+, and then G-quadruplex interacts specifically with N-methylmesoporphyrin IX(NMM), leading to a dramatic increase in fluorescence of NMM. With CA15-3 and NMM as the two inputs, the fluorescence intensity of the NMM is the output signal. Lacking of CA15-3 or NMM, there is no significant fluorescence enhancing, and the output of the signal is “0”. The fluorescence signal was dramatically increasing and the output of the signal is “1” only when CA15-3 protein and NMM were added at the same time. Results: This biosensor strategy possessed selectivity, high sensitivity for detecting CA15-3 protein from 10 to 500 U mL-1 and the detection limit was 10 U mL-1, and also showed good reproducibility in spiked human serum. Conclusion: In summary, the proposed AND logic gate fluorescent aptasensor could specifically detect CA15-3.

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Fabrication of Precise Asymmetric Nanoshells Array with Nanogaps for a Label-Free Immunoassay Based on NIR-Light Responsive LSPR

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.523-524.680 ◽

2012 ◽

Vol 523-524 ◽

pp. 680-685

Author(s):

Shuhei Uchida ◽

Kazuya Yamamura ◽

Nobuyuki Zettsu

Keyword(s):

Near Infrared ◽

Atmospheric Pressure Plasma ◽

High Sensitivity ◽

Medical Diagnostics ◽

Localized Surface Plasmon ◽

Label Free ◽

Fabrication Technique ◽

Alternative Structures ◽

Wide Range ◽

Surrounding Refractive Index

Localized surface plasmon resonance (LSPR) based sensors are a well established technology utilized for label-free biochemical sensing in immunoassay, medical diagnostics and environmental monitoring. The understanding of asymmetric metal nanoparticles, new object for complex, coupled plasmon systems providing localized significantly enhanced E-field, is central to a wide range of novel applications and processes in science of higher sensitive sensing systems. However, few methods are available for actual characterization of such nanostructures at the single particle level. Here we propose a precise and large sized scale fabrication technique for asymmetric nanoshells array with nanogaps of several tens of nanometers for LSPR sensor through atmospheric pressure plasma etching processes. A nanoshell was simply constructed by laminating thin Au films on periodic isolated polymer nanoparticles template. This nanoshells array was expected to exhibit specific near-infrared plasmonic properties. When measuring the sensitivity, nanoshells array exhibited a high sensitivity to changes of surrounding refractive index and showed a higher sensor figure of merit than the alternative structures. This indicated that the enhanced plasmon E-field in the asymmetric nanostructures improved sensor performance. Our fabrication technique and the optical properties of the arrays will provide useful information for developing new plasmonic applications.

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Quantification of Neuropeptide Y with Picomolar Sensitivity Enabled by Guided-Mode Resonance Biosensors

Sensors ◽

10.3390/s20010126 ◽

2019 ◽

Vol 20 (1) ◽

pp. 126 ◽

Cited By ~ 3

Author(s):

Mohammad G. Abdallah ◽

Joseph A. Buchanan-Vega ◽

Kyu J. Lee ◽

Brett R. Wenner ◽

Jeffery W. Allen ◽

...

Keyword(s):

Neuropeptide Y ◽

Near Infrared ◽

Single Point ◽

High Sensitivity ◽

Quantitative Detection ◽

Label Free ◽

Sensor Surface ◽

Detection Range ◽

Guided Mode ◽

Guided Mode Resonance

Assessing levels of neuropeptide Y (NPY) in the human body has many medical uses. Accordingly, we report the quantitative detection of NPY biomarkers applying guided-mode resonance (GMR) biosensor methodology. The label-free sensor operates in the near-infrared spectral region exhibiting distinctive resonance signatures. The interaction of NPY with bioselective molecules on the sensor surface causes spectral shifts that directly identify the binding event without additional processing. In the experiments described here, NPY antibodies are attached to the sensor surface to impart specificity during operation. For the low concentrations of NPY of interest, we apply a sandwich NPY assay in which the sensor-linked anti-NPY molecule binds with NPY that subsequently binds with anti-NPY to close the sandwich. The sandwich assay achieves a detection limit of ~0.1 pM NPY. The photonic sensor methodology applied here enables expeditious high-throughput data acquisition with high sensitivity and specificity. The entire bioreaction is recorded as a function of time, in contrast to label-based methods with single-point detection. The convenient methodology and results reported are significant, as the NPY detection range of 0.1–10 pM demonstrated is useful in important medical circumstances.

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Gas Sensing Properties of TiO2 and SnO2 Nanopowders Obtained through Gel Combustion

Advances in Science and Technology ◽

10.4028/www.scientific.net/ast.45.1828 ◽

2006 ◽

Vol 45 ◽

pp. 1828-1833

Author(s):

Fabio A. Deorsola ◽

P. Mossino ◽

Ignazio Amato ◽

Bruno DeBenedetti ◽

A. Bonavita ◽

...

Keyword(s):

Response Time ◽

Metal Oxides ◽

Gas Sensing ◽

Low Cost ◽

High Sensitivity ◽

Fast Response ◽

High Specific Surface Area ◽

Research Field ◽

Wide Range ◽

Gel Combustion

Nanostructured semiconductor metal oxides have played a central role in the gas sensing research field, because of their high sensitivity, selectivity and low response time. Among all the processes, developed for the synthesis of nanostructured metal oxides, gel combustion seems to be the most promising route due to low-cost precursors and simplicity of the process. It combines chemical gelation and combustion, involving the formation of a gel from an acqueous solution and an exothermic redox reaction, yielding to very porous and softly agglomerated nanopowders. In this work, nanostructured tin oxide, SnO2, and titanium oxide, TiO2, have been synthesized through gel combustion. Powders showed nanometric particle size and high specific surface area. The so-obtained TiO2 and SnO2 nanopowders have been used as sensitive element of resistive λ sensor and ethanol sensor respectively, realized depositing films of nanopowders dispersed in water onto alumina substrates provided with Pt contacts and heater. TiO2-based sensors showed at high temperature good response, fast response time, linearity in a wide range of O2 concentration and long-term stability. SnO2-based sensors have shown high sensitivity to low concentrations of ethanol at moderate temperature.

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A multipurpose biochip for food pathogen detection

Analytical Methods ◽

10.1039/c5ay03295d ◽

2016 ◽

Vol 8 (15) ◽

pp. 3055-3060 ◽

Cited By ~ 22

Author(s):

Elisabetta Primiceri ◽

Maria Serena Chiriacò ◽

Francesco de Feo ◽

Elisa Santovito ◽

Vincenzina Fusco ◽

...

Keyword(s):

Pathogen Detection ◽

Low Cost ◽

High Sensitivity ◽

Label Free ◽

Food Pathogen

We realized an innovative biosensing platform with high sensitivity, low-cost and label-free features forS. aureusandL. monocytogenesdetection from meat.

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