Oligonucleotide-based systems:DNA, microRNAs, DNA/RNA aptamers

There is an increasing number of applications that have been developed for oligonucleotide-based biosensing systems in genetics and biomedicine. Oligonucleotide-based biosensors are those where the probe to capture the analyte is a strand of DNA, RNA or a synthetic analogue to naturally occurring nucleic acids. This chapter will draw light upon various types of nucleic acids such as DNA, RNA (particularly microRNAs), their role and their application in biosensing. Also, it will cover DNA/RNA aptamers, which can be used as bioreceptors to a wide range of targets such as proteins, small molecules, bacteria and even cells. It will also highlight how the invention of synthetic oligonucleotides like PNA or LNA has pushed the limits of molecular biology and biosensor development to new perspectives. These technologies are very promising albeit still in need of development in order to bridge the gap between the lab-based status and the reality of biomedical applications

Introduction to biosensors

Biosensors are nowadays ubiquitous in biomedical diagnosis as well as a wide range of other areas such as point-of-care monitoring of treatment and disease progression, environmental monitoring, food control, drug discovery, forensics and biomedical research. A wide range of techniques can be used for the development of biosensors. Their coupling with high affinity biomolecules allows the sensitive and selective detection of a range of analytes.We here give a general introduction to biosensors and biosensing technologies, including a brief historical overview, introducing key developments in the field and illustrate the breadth of biomolecular sensing strategies and the expansion of nanotechnological approaches that are now available.<br/

DNA Aptamer-based detection of prostate cancer

AbstractThe use of aptamers in biosensing has attracted considerable attention as an alternative to antibodies because of their unique properties such as long-term stability, cost-effectiveness and adjustability to various applications. Among cancers, the early diagnosis of prostate cancer (PCa) is one of the greatest concerns for ageing men worldwide. One of the most commonly used biomarkers for PCa is prostate-specific antigen (PSA), which can be found in elevated levels in patients with cancer. This review presents the gradual transition of research from antibody-based to aptamerbased biosensors, specifically for PSA. A brief description on aptamer-based biosensing for other PCa biomarkers is also presented. Special attention is given to electrochemical methods as analytical techniques for the development of simple, sensitive and cost-effective biosensors. The review also focuses on the different surface chemistries exploited for fabrication and their applications in clinical samples. The use of aptamers represents a promising tool for the development of point-ofcare biosensors for the early detection of prostate cancer. In view of the unmatched upper hand of aptamers, future prospects are also discussed, not only in the point-of-care format but also in other novel applications.</jats:p

Development of a sensitive multiplexed open circuit potential system for the detection of prostate cancer biomarkers

We report the development of a sensitive label-free, cost-effective detection system with simultaneous multi-channel measurement of open circuit potential (OCP) variations for the detection of prostate specific antigen (PSA). We demonstrate a significant increase of 600 times in the sensitivity as compared to the reported literature. To accurately measure OCP variations, a complete monolithic field-effect transistor (FET)-input ultra-low input bias current instrumentation amplifier is used to form the electronic circuit to measure the variation between a working electrode and a reference electrode. This amplifier electronic system setup provides a differential voltage measurement with high input impedance and low input bias current. Since no current is applied to the electrochemical system, a true and accurate measurement of the variation can be performed. This is the first report on the use of DNA aptamers with an OCP system where we employed a DNA aptamer against PSA. An optimised ratio of anti-PSA DNA aptamer with 6-mercapto-1-hexanol (MCH) was used to fabricate the aptasensor using gold electrodes. The electrodes are hosted in a cell with an automated flow system. A wide range of concentrations of PSA (0.1 to 100 ng/mL) were injected through the system. The sensor could potentially differentiate 0.1 ng/mL PSA from blank measurement, which is well below the required clinical range (&amp;gt;1 ng/mL). The sensor was also challenged with 4% human serum albumin and human kallikrein2 as control proteins where the sensor demonstrated excellent selectivity. The developed system can be further generalised to various other targets using specific probes.</p

Introduction to biosensors

Biosensors are nowadays ubiquitous in biomedical diagnosis as well as a wide range of other areas such as point-of-care monitoring of treatment and disease progression, environmental monitoring, food control, drug discovery, forensics and biomedical research. A wide range of techniques can be used for the development of biosensors. Their coupling with high-affinity biomolecules allows the sensitive and selective detection of a range of analytes. We give a general introduction to biosensors and biosensing technologies, including a brief historical overview, introducing key developments in the field and illustrating the breadth of biomolecular sensing strategies and the expansion of nanotechnological approaches that are now available

Aptamer-based Field-Effect Biosensor for Tenofovir Detection

During medical treatment it is critical to maintain the circulatory concentration of drugs within their therapeutic range. A novel biosensor is presented in this work to address the lack of a reliable point-of-care drug monitoring system in the market. The biosensor incorporates high selectivity and sensitivity by integrating aptamers as the recognition element and field-effect transistors as the signal transducer. The drug tenofovir was used as a model small molecule. The biointerface of the sensor is a binary self-assembled monolayer of specific thiolated aptamer and 6-mercapto-1-hexanol (MCH), whose ratio was optimized by electrochemical impedance spectroscopy measurements to enhance the sensitivity towards the specific target. Surface plasmon resonance, performed under different buffer conditions, shows optimum specific and little non-specific binding in phosphate buffered saline. The dose-response behavior of the field-effect biosensor presents a linear range between 1 nM and 100 nM of tenofovir and a limit of detection of 1.2 nM. Two non-specific drugs and one non-specific aptamer, tested as stringent control candidates, caused negligible responses. The applications were successfully extended to the detection of the drug in human serum. As demonstrated by impedance measurements, the aptamer-based sensors can be used for real-time drug monitoring

A PNA-based Lab-on-PCB diagnostic platform for rapid and high sensitivity DNA quantification

We report the development of a Lab-on-PCB DNA diagnostic platform, exploiting peptide nucleic acid (PNA) sequences as probes. The study demonstrates the optimization and characterization of two commercial PCB manufacturing gold electroplating processes for biosensing applications. Using an optimized ratio of PNA with a spacer molecule (MCH), the lowest limit of detection (LoD) to date for PCB-based DNA biosensors of 57 fM is reported. The study also showcases a fully integrated Lab-on-PCB microsystem designed for rapid detection, which employs PCB-integrated sample delivery, achieving DNA quantification in the 0.1–100 pM range for 5 μL samples analyzed within 5 min under continuous flow. The demonstrated biosensor proves the capability of PCB-based DNA biosensors for high sensitivity and paves the way for their integration in Lab-on-PCB DNA diagnostic microsystems