A lateral flow biosensor for rapid detection of DNA-binding protein c-jun

A signal-enhanced and sensitive lateral flow aptasensor for the rapid detection of PDGF-BB

Platelet-derived growth factor BB (PDGF-BB) is a potential biomarker of tumor angiogenesis. For the first time, we developed a highly sensitive aptasensor for PDGF-BB with an enhanced test line signal by using two different gold nanoparticles (AuNPs). Herein, we describe a highly sensitive biosensor for PDGF-BB detection that combines biotinylated aptamer on a sample pad and poly thymine-Cy3-AuNP-monoclonal antibody complexes against PDGF-BB immobilized on conjugate pad A. Streptavidin (SA) and rabbit anti-mouse polyclonal antibody were also immobilized in the nitrocellulose membrane at the test and control zones, respectively. When the target PDGF-BB protein was added, it first bound the aptamer, and later the monoclonal antibody to form a biotinylated complex that was captured by SA, resulting in a visual red line on the test zone. In addition, to enhance the sensitivity, another monoclonal antibody against Cy3 was conjugated on AuNP B and immobilized on conjugate pad B to form a AuNPs (A&B)-antibody-(PDGF-BB-Cy3)-aptamer-biotin-SA complex on the test line when a loading buffer was subsequently added. This approach showed a linear response to PDGF-BB from 3 ng mL⁻¹ to 300 ng mL⁻¹ with a limit of detection as low as 1 ng mL⁻¹ obtained in 10 minutes. Our biosensor displayed results through red lines readable by the naked eye. Interestingly, our approach has been successfully applied for real sample verification, proving its applicability for cancer monitoring and diagnosis.

Platelet-derived growth factor BB (PDGF-BB) is a potential biomarker of tumor angiogenesis.

Lateral flow biosensors based on the use of micro- and nanomaterials: a review on recent developments

This review (with 187 refs.) summarizes the progress that has been made in the design of lateral flow biosensors (LFBs) based on the use of micro- and nano-materials. Following a short introduction into the field, a first section covers features related to the design of LFBs, with subsections on strip-based, cotton thread-based and vertical flow- and syringe-based LFBs. The next chapter summarizes methods for sample pretreatment, from simple method to membrane-based methods, pretreatment by magnetic methods to device-integrated sample preparation. Advances in flow control are treated next, with subsections on cross-flow strategies, delayed and controlled release and various other strategies. Detection conditionst and mathematical modelling are briefly introduced in the following chapter. A further chapter covers methods for reliability improvement, for example by adding other validation lines or adopting different detection methods. Signal readouts are summarized next, with subsections on color-based, luminescent, smartphone-based and SERS-based methods. A concluding section summarizes the current status and addresses challenges in future perspectives. Graphical abstractRecent development and breakthrough points of lateral flow biosensors.

A highly sensitive and specific lateral flow aptasensor for the detection of human osteopontin

The rapid determination of human osteopontin (OPN) protein, a potential cancer biomarker, holds substantial promise for point-of-care diagnostics and biomedical applications. To date, most reported platforms for OPN detection are apparatus-dependent, time-consuming, and expensive. Herein, we established a lateral flow biosensor (LFB) for OPN detection. A biotinylated aptamer was used for OPN pre-capture from samples, an antibody for OPN was immobilized on the test line for a second specific target identification, and streptavidin-modified gold nanoparticles were sprayed on the conjugation pad for color detection. This LFB achieved as low as 0.1 ng mL^-1 OPN sensitivity with a good dynamic detection between 10 and 500 ng mL^-1 within 5 min. Intriguingly, the LFB allowed a qualitative and semi-quantitative detection of OPN in serum at clinically cut-off levels as in cancer patients, and can discriminate OPN from interfering proteins with high specificity. Thus, it is a promising alterative approach for point-of-care OPN screening and detection.

Paper-based biodetection using luminescent nanoparticles

Point-of-care and in-field technologies for rapid, sensitive and selective detection of molecular biomarkers have attracted much interest. Rugged bioassay technology capable of fast detection of markers for pathogens and genetic diseases would in particular impact the quality of health care in the developing world, but would also make possible more extensive screening in developed countries to tackle problems such as those associated with water and food quality, and tracking of infectious organisms in hospitals and clinics. Literature trends indicate an increasing interest in the use of nanomaterials, and in particular luminescent nanoparticles, for assay development. These materials may offer attributes for development of assays and sensors that could achieve improvements in analytical figures of merit, and provide practical advantages in sensitivity and stability. There is opportunity for cost-efficiency and technical simplicity by implementation of luminescent nanomaterials as the basis for transduction technology, when combined with the use of paper substrates, and the ubiquitous availability of cell phone cameras and associated infrastructure for optical detection and transmission of results. Luminescent nanoparticles have been described for a broad range of bioanalytical targets including small molecules, oligonucleotides, peptides, proteins, saccharides and whole cells (e.g., cancer diagnostics). The luminescent nanomaterials that are described herein for paper-based bioassays include metal nanoparticles, quantum dots and lanthanide-doped nanocrystals. These nanomaterials often have broad and strong absorption and narrow emission bands that improve opportunity for multiplexed analysis, and can be designed to provide emission at wavelengths that are efficiently processed by conventional digital cameras. Luminescent nanoparticles can be embedded in paper substrates that are designed to direct fluid flow, and the resulting combination of technologies can offer competitive analytical performance at relatively low cost.

A Lateral Flow Biosensor for the Detection of Single Nucleotide Polymorphisms

A lateral flow biosensor (LFB) is introduced for the detection of single nucleotide polymorphisms (SNPs). The assay is composed of two steps: circular strand displacement reaction and lateral flow biosensor detection. In step 1, the nucleotide at SNP site is recognized by T4 DNA ligase and the signal is amplified by strand displacement DNA polymerase, which can be accomplished at a constant temperature. In step 2, the reaction product of step 1 is detected by a lateral flow biosensor, which is a rapid and cost effective tool for nuclei acid detection. Comparing with conventional methods, it requires no complicated machines. It is suitable for the use of point of care diagnostics. Therefore, this simple, cost effective, robust, and promising LFB detection method of SNP has great potential for the detection of genetic diseases, personalized medicine, cancer related mutations, and drug-resistant mutations of infectious agents.

A versatile valving toolkit for automating fluidic operations in paper microfluidic devices

Failure to utilize valving and automation techniques has restricted the complexity of fluidic operations that can be performed in paper microfluidic devices. We developed a toolkit of paper microfluidic valves and methods for automatic valve actuation using movable paper strips and fluid-triggered expanding elements. To the best of our knowledge, this is the first functional demonstration of this valving strategy in paper microfluidics. After introduction of fluids on devices, valves can actuate automatically after a) a certain period of time, or b) the passage of a certain volume of fluid. Timing of valve actuation can be tuned with greater than 8.5% accuracy by changing lengths of timing wicks, and we present timed on-valves, off-valves, and diversion (channel-switching) valves. The actuators require ~30 μl fluid to actuate and the time required to switch from one state to another ranges from ~5 s for short to ~50 s for longer wicks. For volume-metered actuation, the size of a metering pad can be adjusted to tune actuation volume, and we present two methods - both methods can achieve greater than 9% accuracy. Finally, we demonstrate the use of these valves in a device that conducts a multi-step assay for the detection of the malaria protein PfHRP2. Although slightly more complex than devices that do not have moving parts, this valving and automation toolkit considerably expands the capabilities of paper microfluidic devices. Components of this toolkit can be used to conduct arbitrarily complex, multi-step fluidic operations on paper-based devices, as demonstrated in the malaria assay device.

A sensitive lateral flow biosensor for Escherichia coli O157:H7 detection based on aptamer mediated strand displacement amplification

Foodborne diseases caused by pathogens are one of the major problems in food safety. Convenient and sensitive point-of-care rapid diagnostic tests for food-borne pathogens have been a long-felt need of clinicians. Commonly used methods for pathogen detection rely on conventional culture-based tests, antibody-based assays and polymerase chain reaction (PCR)-based techniques. These methods are costly, laborious and time-consuming. Herein, we present a simple and sensitive aptamer based biosensor for rapid detection of Escherichia coli O157:H7 (E. coli O157:H7). In this assay, two different aptamers specific for the outmembrane of E. coli O157:H7 were used. One of the aptamers was used for magnetic bead enrichment, and the other was used as a signal reporter for this pathogen, which was amplified by isothermal strand displacement amplification (SDA) and further detected by a lateral flow biosensor. Only the captured aptamers on cell membrane were amplified, limitations of conventional DNA amplification based method such as false-positive can be largely reduced. The generated signals (red bands on the test zone of a lateral flow strip) can be unambiguously read out by the naked eye. As low as 10 colony forming units (CFU) of E. coli O157:H7 were detected in this study. Without DNA extraction, the reduced handling and simpler equipment requirement render this assay a simple and rapid alternative to conventional methods.

Gold-nanoparticle-decorated silica nanorods for sensitive visual detection of proteins

We report a rapid and highly sensitive approach based on gold-nanoparticle-decorated silica nanorods (GNP-SiNRs) label and lateral-flow strip biosensor (LFSB) for visually detecting proteins. Owing to its biocompatibility and convenient surface modification, SiNRs were used as carriers to load numerous GNPs, and the GNP-SiNRs were used as labels for the lateral-flow assay. The LFSB detection limit was lowered 50 times compared to the traditional GNP-based lateral-flow assay. Rabbit IgG was used as a model target to demonstrate the proof-of-concept. Sandwich-type immunoreactions were performed on the immunochromatographic strips, and the accumulation of GNP-SiNRs on the test zone produced the characteristic colored bands, enabling visual detection of proteins without instrumentation. The quantitative detection was performed by reading the intensities of the colored bands with a portable strip reader. The response of the optimized device was highly linear for the range of 0.05-2 ng mL(-1), and the detection limit was estimated to be 0.01 ng mL(-1). The GNP-SiNR-based LFSB, thus, offered an ultrasensitive method for rapidly detecting trace amounts of proteins. This method has a potential application with point-of-care screening for clinical diagnostics and biomedical research.

A universal lateral flow biosensor for proteins and DNAs based on the conformational change of hairpin oligonucleotide and its use for logic gate operations

A universal lateral flow biosensor for proteins and DNAs was designed on the base of target-induced conformational changes of hairpin oligonucleotide (HO). CEA (carcinoembryonic antigen) protein and c-DNA were detected both with the naked eye and a strip reader. The scheme of detecting proteins and DNAs were based on the unique molecular recognition properties of HO to the targets to form different quantities of "active" biotin groups on the surface of gold nanoparticles (AuNPs). The output of the strip is the color of the test line, which inspired us to combine strip biosensor with logic gate. Two strip logic gates ("OR" and "INH") were designed in our paper and the combinatorial logic gates in our paper could be used to make high-throughput judgment about what targets were present in the input samples according to the output results. The biosensor facilitates a portable analysis at ambient temperature as it is simple to be conducted and no requirement of training is needed. The strip logic system is proved an excellent selection and can operate effectively as well as in human serum samples. Therefore, we indicate that such logic strips a foreseeable promise in application of intelligent point-of-care and in-field diagnostics.

Paper-based nanobiosensors for diagnostics

In this review we discuss how nanomaterials can be integrated in diagnostic paper-based biosensors for the detection of proteins, nucleic acids and cells. In particular first the different types and properties of paper-based nanobiosensors and nanomaterials are briefly explained. Then several examples of their application in diagnostics of several biomarkers are reported. Finally our opinions regarding future trends in this field are discussed.

Lateral flow biosensors for the detection of nucleic acid

The detection of nucleic acid is of central importance for the diagnosis of genetic diseases, infectious agents, and biowarfare agents. Traditional strategies and technologies for nucleic acid detection are time-consuming and labor-intensive. Recently, isothermal strand-displacement reaction-based lateral flow biosensors have attracted a great deal of research interest because they are sensitive, simple, fast, and easy to use. Here, we describe a lateral flow biosensor based on isothermal strand-displacement polymerase reaction and gold nanoparticles for the visual detection of nucleic acid.

Computational lateral flow biosensor for proteins and small molecules: a new class of strip logic gates

The first example of strip logic gates ("OR" and "AND" functions) for proteins and small molecules has been constructed on the basis of target-induced self-assembly of split aptamer fragments. Using thrombin and ATP as inputs, the corresponding split/integrated aptamers as molecular recognition elements, and gold nanoparticles as a tracer, the output signals can be directly visualized by observing the red bands on the test zones of the strips. The assay is simple, easy to perform, and cost-effective, allowing portable analysis at ambient temperature. The strip logic system is resistant to nonspecific interfering agents and can operate effectively even in human serum samples. Such logic strips hold great promise for application in intelligent point-of-care and in-field diagnostics.