Label-free, all-electrical, in situ human epidermal growth receptor 2 detection

Epidermal Wearable Biosensors for the Continuous Monitoring of Biomarkers of Chronic Disease in Interstitial Fluid

Healthcare technology has allowed individuals to monitor and track various physiological and biological parameters. With the growing trend of the use of the internet of things and big data, wearable biosensors have shown great potential in gaining access to the human body, and providing additional functionality to analyze physiological and biochemical information, which has led to a better personalized and more efficient healthcare. In this review, we summarize the biomarkers in interstitial fluid, introduce and explain the extraction methods for interstitial fluid, and discuss the application of epidermal wearable biosensors for the continuous monitoring of markers in clinical biology. In addition, the current needs, development prospects and challenges are briefly discussed.

Electrochemical immunosensor for breast cancer biomarker detection using high-density silicon microneedle array

Electrochemical devices for transdermal monitoring of key biomarkers are the potential next frontier of wearable technologies for point-of-care disease diagnosis, including Cancer in which Cancer is the leading cause of death worldwide with estimated 10 million deaths in 2018 according to the World Health Organization and breast cancer is one of the five most common causes of cancer death with over two million cases recorded in 2018. Early diagnosis and prognosis based on monitoring of breast cancer biomarkers is of high importance. In this work, high-density gold coated silicon microneedle arrays (Au-Si-MNA) were simultaneously used as biomarker extraction platform and electrochemical transducer, enabling the selective immunocapture of epidermal growth factor receptor 2 (ErbB2), a key breast cancer biomarker, and its subsequent quantification. The analytical performance of the device was tested in artificial interstitial fluid exhibiting a linear response over a wide concentration range from 10 to 250 ng/mL, with a detection limit of 4.8 ng/mL below the biomarker levels expected in breast cancer patients. As a proof of concept, the immunosensor demonstrated its ability to successfully extract ErbB2 from a phantom gel mimicking the epidermis and dermis layers, and subsequently quantify it showing a linear range from 50 to 250 ng/mL and a detection limit of 25 ng/mL. The uniqueness of this sensing platform combining direct transdermal biomarker extraction and quantification opens up new avenues towards the development of high performing wearable point-of-care devices.

Advances in HER2 testing

HER2-positive breast cancer is a particularly aggressive type of breast cancer. Indication of HER2 positivity is essential for its treatment. In addition to a few FDA-approved methods such as immunohistochemical (IHC) detection of HER2 protein expression and in situ hybridization (ISH) assessment of HER2 gene amplification, several novel methods have been developed for HER2 testing in recent years. This chapter provides an overview of HER2 testing with emphasis on those new methods.

A fluorescent aptasensor for the femtomolar detection of epidermal growth factor receptor-2 based on the proximity of G-rich sequences to Ag nanoclusters

Human epidermal growth factor receptor-2 (HER2) has been recognized as an important biomarker for the early diagnosis and management of breast cancer. However, there is still challenge in the clinical detection of HER2. In this work, a simple strategy for "turn on" fluorescent detection of HER2 with ultra-sensitivity and high specificity was developed. Herein, HER2-binding aptamer (HApt) and DNA2 containing G-rich sequences, templated sequences for Ag nanoclusters (AgNCs), and complementary bases at both ends were involved to achieve the double stranded DNA templated AgNCs (dsDNA-AgNCs) as a fluorescence probe for HER2 detection. In the presence of HER2, the highly specific binding of HER2 to HApt caused HApt separating from dsDNA-AgNCs, resulting in the folding of DNA2-AgNCs because of the complementary bases at both ends, which led to AgNCs' proximity to G-rich sequences, and therefore the enhanced fluorescence intensity. By monitoring the change in fluorescence signal (ΔF), HER2 was measured, and a linear range from 8.5 fM to 225 fM with a limit of detection (LOD) 0.0904 fM was obtained. More significantly, the detection of HER2 in serum samples was achieved with high accuracy, and the breast cancer patients were successfully discriminated from healthy persons. In summary, this strategy is simple, time-saving, cost-effective, ultrasensitive, specific, universal and more applicable for the detection of HER2. Therefore, we expect this present aptasensor can be used in the clinical detection of biomakers, which lays a potential foundation for the early diagnosis of cancer.

Ultra-low fouling methylimidazolium modified surfaces for the detection of HER2 in breast cancer cell lysates

We synthesized novel ultra-low fouling ionic liquids and demonstrated their use with surface plasmon resonance (SPR) sensing for the analysis of HER2 in breast cancer cell lysates.

Recent advances in biosensor development for the detection of cancer biomarkers

Cancer is the second largest disease throughout the world with an increasing mortality rate over the past few years. The patient's survival rate is uncertain due to the limitations of cancer diagnosis and therapy. Early diagnosis of cancer is decisive for its successful treatment. A biomarker-based cancer diagnosis may significantly improve the early diagnosis and subsequent treatment. Biosensors play a crucial role in the detection of biomarkers as they are easy to use, portable, and can do analysis in real time. This review describes various biosensors designed for detecting nucleic acid and protein-based cancer biomarkers for cancer diagnosis. It mainly lays emphasis on different approaches to use electrochemical, optical, and mass-based transduction systems in cancer biomarker detection. It also highlights the analytical performances of various biosensor designs concerning cancer biomarkers in detail.

Nanomechanical Sensors

This chapter introduces nanomechanical sensors and their applications. All molecules have “volume” and “mass.” Direct measurement of these fundamental parameters can realize label-free and real-time measurements. Nanomechanical sensors have been emerging as a key device for such label-free and real-time measurements with their multiple operation modes; static and dynamic modes for detecting volume- and mass-related features, respectively. A cantilever array sensor is a representative example among various geometries, while structural optimization can enhance the scope of nanomechanical sensors in both academic and industrial applications. One of the most advanced sensing platforms is a membrane-type surface stress sensor (MSS), which realizes both high sensitivity and compact system at the same time. The MSS is also expected to contribute to addressing nanomechanical behavior of living cells and their network.

A rapid method to regenerate piezoelectric microcantilever sensors (PEMS)

Piezoelectric microcantilever sensors (PEMS) can be sensitive tools for the detection of proteins and cells in biological fluids. However, currently available PEMS can only be used a single time or must be completely stripped and refunctionalized prior to subsequent uses. Here we report the successful use of an alternative regeneration protocol employing high salt concentrations to remove the target, leaving the functional probe immobilized on the microcantilever surface. Our model system employed the extracellular domain (ECD) of recombinant human Epidermal Growth Factor Receptor (EGFR) as the probe and anti-human EGFR polyclonal antibodies as the target. We report that high concentrations of MgCl₂ dissociated polyclonal antibodies specifically bound to EGFR ECD immobilized on the sensor surface without affecting its bioactivity. This simple regeneration protocol both minimized the time required to re-conjugate the probe and preserved the density of probe immobilized on PEMS surface, yielding identical biosensor sensitivity over a series of assays.

Label-free Growth Receptor-2 Detection and Dissociation Constant Assessment in Diluted Human Serum Using a Longitudinal Extension Mode of a Piezoelectric Microcantilever Sensor

We have investigated real-time, label-free, in-situ detection of human epidermal growth factor receptor 2 (Her2) in diluted serum using the first longitudinal extension mode of a lead zirconate-lead titanate (PZT)/glass piezoelectric microcantilever sensor (PEMS) with H3 single-chain variable fragment (scFv) immobilized on the 3-mercaptopropyltrimethoxysilane (MPS) insulation layer of the PEMS surface. We showed that with the longitudinal extension mode, the PZT/glass PEMS consisting of a 1 mm long and 127 μm thick PZT layer bonded with a 75 μm thick glass layer with a 1.8 mm long glass tip could detect Her2 at a concentration of 6-60 ng/ml (or 0.06-0.6 nM) in diluted human serum, about 100 times lower than the concentration limit obtained using the lower-frequency flexural mode of a similar PZT/glass PEMS. We further showed that with the longitudinal mode, the PZT/glass PEMS determined the equilibrium H3-Her2 dissociation constant K(d) to be 3.3±0.3 × 10(-8) M consistent with the value, 3.2±0.28 ×10(-8) M deduced by the surface plasmon resonance method (BIAcore).

Recombinant antibodies and their use in biosensors

Inexpensive, noninvasive immunoassays can be used to quickly detect disease in humans. Immunoassay sensitivity and specificity are decidedly dependent upon high-affinity, antigen-specific antibodies. Antibodies are produced biologically. As such, antibody quality and suitability for use in immunoassays cannot be readily determined or controlled by human intervention. However, the process through which high-quality antibodies can be obtained has been shortened and streamlined by use of genetic engineering and recombinant antibody techniques. Antibodies that traditionally take several months or more to produce when animals are used can now be developed in a few weeks as recombinant antibodies produced in bacteria, yeast, or other cell types. Typically most immunoassays use two or more antibodies or antibody fragments to detect antigens that are indicators of disease. However, a label-free biosensor, for example, a quartz-crystal microbalance (QCM) needs one antibody only. As such, the cost and time needed to design and develop an immunoassay can be substantially reduced if recombinant antibodies and biosensors are used rather than traditional antibody and assay (e.g. enzyme-linked immunosorbant assay, ELISA) methods. Unlike traditional antibodies, recombinant antibodies can be genetically engineered to self-assemble on biosensor surfaces, at high density, and correctly oriented to enhance antigen-binding activity and to increase assay sensitivity, specificity, and stability. Additionally, biosensor surface chemistry and physical and electronic properties can be modified to further increase immunoassay performance above and beyond that obtained by use of traditional methods. This review describes some of the techniques investigators have used to develop highly specific and sensitive, recombinant antibody-based biosensors for detection of antigens in simple or complex biological samples.

Proteomic technologies for the identification of disease biomarkers in serum: advances and challenges ahead

Serum is an ideal biological sample that contains an archive of information due to the presence of a variety of proteins released by diseased tissue, and serum proteomics has gained considerable interest for the disease biomarker discovery. Easy accessibility and rapid protein changes in response to disease pathogenesis makes serum an attractive sample for clinical research. Despite these advantages, the analysis of serum proteome is very challenging due to the wide dynamic range of proteins, difficulty in finding low-abundance target analytes due to the presence of high-abundance serum proteins, high levels of salts and other interfering compounds, variations among individuals and paucity of reproducibility. Sample preparation introduces pre-analytical variations and poses major challenges to analyze the serum proteome. The label-free detection techniques such as surface plasmon resonance, microcantilever, few nanotechniques and different resonators are rapidly emerging for the analysis of serum proteome and they have exhibited potential to overcome few limitations of the conventional techniques. In this article, we will discuss the current status of serum proteome analysis for the biomarker discovery and address key technological advancements, with a focus on challenges and amenable solutions.

Highly sensitive detection of HER2 extracellular domain in the serum of breast cancer patients by piezoelectric microcantilevers

Rapid and sensitive detection of serum tumor biomarkers are needed to monitor cancer patients for disease progression. Highly sensitive piezoelectric microcantilever sensors (PEMS) offer an attractive tool for biomarker detection; however, their utility in the complex environment encountered in serum has yet to be determined. As a proof of concept, we have functionalized PEMS with antibodies that specifically bind to HER2, a biomarker (antigen) that is commonly overexpressed in the blood of breast cancer patients. The function and sensitivity of these anti-HER2 PEMS biosensors was initially assessed using recombinant HER2 spiked into human serum. Their ability to detect native HER2 present in the serum of breast cancer patients was then determined. We have found that the anti-HER2 PEMS were able to accurately detect both recombinant and naturally occurring HER2 at clinically relevant levels (>2 ng/mL). This indicates that PEMS-based biosensors provide a potentially effective tool for biomarker detection.

Microcantilever biosensors for chemicals and bioorganisms

In the last fifteen years, microcantilevers (MCLs) have been emerging as a sensitive tool for the detection of chemicals and bioorganisms. Because of their small size, lightweight, and high surface-to-volume ratio, MCL-based sensors improve our capability to detect and identify biological agents by orders of magnitude. A biosensor is a device for the detection of an analyte that combines a biological component with a physicochemical detector component. The MCL biosensors have recently been reviewed in several papers. All of these papers were organized based on the sensing biological elements (antibody, enzyme, proteins, etc.) for recognition of analytes. In this review, we intend to summarize the microcantilever biosensors in a format of each specific chemical and bioorganism species to make information on individual biosensors easily accessible. We did this to aid researchers to locate relevant references.

Label free detection of white spot syndrome virus using lead magnesium niobate-lead titanate piezoelectric microcantilever sensors

We have investigated rapid, label free detection of white spot syndrome virus (WSSV) using the first longitudinal extension resonance peak of five lead-magnesium niobate-lead titanate (PMN-PT) piezoelectric microcantilever sensors (PEMS) 1050-700 μm long and 850-485 μm wide constructed from 8 μm thick PMN-PT freestanding films. The PMN-PT PEMS were encapsulated with a 3-mercaptopropyltrimethoxysilane (MPS) insulation layer and further coated with anti-VP28 and anti-VP664 antibodies to target the WSSV virions and nucleocapsids, respectively. By inserting the antibody coated PEMS in a flowing virion or nucleocapsid suspension, label free detection of the virions and nucleocapsids were respectively achieved by monitoring the PEMS resonance frequency shift. We showed that positive label free detection of both the virion and the nucleocapsid could be achieved at a concentration of 100virions(nucleocapsids)/ml or 10 virions(nucleocapsids)/100 μl, comparable to the detection sensitivity of polymerase chain reaction (PCR). However, in contrast to PCR, PEMS detection was label free, in situ and rapid (less than 30 min), potentially requiring minimal or no sample preparation.

Array lead zirconate titanate/glass piezoelectric microcantilevers for real-time detection of Bacillus anthracis with 10 spores/ml sensitivity and 1/1000 selectivity in bacterial mixtures

An array of three identical piezoelectric microcantilever sensors (PEMSs) consisting of a lead zirconate titanate layer bonded to a glass layer was fabricated and examined for simultaneous, in situ, real-time, all-electrical detection of Bacillus anthracis (BA) spores in an aqueous suspension using the first longitudinal extension mode of resonance. With anti-BA antibody immobilized on the sensor surfaces all three PEMS exhibited identical BA detection resonance frequency shifts at all tested concentrations, 10-10(7) spores/ml with a standard deviation of less than 10%. The detection concentration limit of 10 spores/ml was about two orders of magnitude lower than would be permitted by flexural peaks. In blinded-sample testing, the array PEMS detected BA in three samples containing BA: (1) 3.3x10(3) spores/ml, (2) a mixture of 3.3x10(3) spores/ml and 3.3x10(5) S. aureus (SA) and P. aeruginosa (PA) per ml, and (3) a mixture of 3.3x10(3) spores/ml with 3.3x10(6) SA+PA/ml. There was no response to a sample containing only 3.3x10(6) SA+PA/ml. These results illustrate the sensitivity, specificity, reusability, and reliability of array PEMS for in situ, real-time detection of BA spores.

Label-free technologies for quantitative multiparameter biological analysis

In the postgenomic era, information is king and information-rich technologies are critically important drivers in both fundamental biology and medicine. It is now known that single-parameter measurements provide only limited detail and that quantitation of multiple biomolecular signatures can more fully illuminate complex biological function. Label-free technologies have recently attracted significant interest for sensitive and quantitative multiparameter analysis of biological systems. There are several different classes of label-free sensors that are currently being developed both in academia and in industry. In this critical review, we highlight, compare, and contrast some of the more promising approaches. We describe the fundamental principles of these different methods and discuss advantages and disadvantages that might potentially help one in selecting the appropriate technology for a given bioanalytical application.