An antifouling interface integrated with HRP-based amplification to achieve a highly sensitive electrochemical aptasensor for lysozyme detection

Development of an electrochemical biosensor utilizing a combined aptamer and MIP strategy for the detection of the food allergen lysozyme

This study aims to develop a MIP-Apt-based electrochemical biosensor for the sensitive and selective determination of Lysozyme (Lyz), a food allergen. For the development of the sensor, in the first stage, modifications were made to the screen-printed electrode (SPE) surface with graphene oxide (GO) and gold nanoparticles (AuNPs) to increase conductivity and surface area. The advantages of using aptamer (Apt) and molecularly imprinted polymer (MIP) technology were combined in a single biointerface in the prepared sensing tool. Surface characterization of the biosensor was performed using scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectrometry (XPS), contact angle measurements, cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS). A wide linear range from 0.001 to 100 pM was obtained under optimized conditions for the determination of Lyz detection using the proposed MIP-Apt sensing strategy. The limit of detection (LOD) and limit of quantification (LOQ) for Lyz were 3.67 fM and 12 fM, respectively. This biosensor displays high selectivity, repeatability, reproducibility, and long storage stability towards Lyz detection. The results show that a sensitive and selective sensor fabrication is achieved compared with existing methods.

Surface-Enhanced Carboxyphenyl Diazonium Functionalized Screen-Printed Carbon Electrode for the Screening of Tuberculosis in Sputum Samples

Curbing tuberculosis (TB) requires a combination of good strategies, including a proper prevention measure, diagnosis, and treatment. This study proposes an improvised tuberculosis diagnosis based on an amperometry approach for the sensitive detection of MPT64 antigen in clinical samples. An MPT64 aptamer specific to the target antigen was covalently attached to the carboxyphenyl diazonium-functionalized carbon electrode via carbodiimide chemistry. The electrochemical detection assay was adapted from a sandwich assay format to trap the antigen between the immobilized aptamer and horseradish peroxidase (HRP) tagged polyclonal anti-MPT64 antibody. The amperometric current was measured from the catalytic reaction response between HRP, hydrogen peroxide, and hydroquinone, which is used as an electron mediator. From the analysis, the detection limit in the measurement buffer was 1.11 ng mL^-1. Additionally, the developed aptasensor exhibited a linear relationship between the current signal and the MPT64 antigen-spiked serum concentration ranging from 10 to 150 ng mL^-1 with a 1.38 ng mL^-1 detection limit. Finally, an evaluation using the clinical sputum samples from both TB (+) and TB (-) individuals revealed a sensitivity and specificity of 88% and 100%, respectively. Based on the analysis, the developed aptasensor was found to be simple in its fabrication, sensitive, and allowed for the efficient detection and diagnosis of TB in sputum samples.

Rational design of smart nano-platforms based on antifouling-nanomaterials toward multifunctional bioanalysis

The ability to design nanoprobe devices with the capability of quantitative/qualitative operation in complex media will probably underpin the main upcoming progress in healthcare research and development. However, the biomolecules abundances in real samples can considerably alter the interface performance, where unwanted adsorption/adhesion can block signal response and significantly decrease the specificity of the assay. Herein, this review firstly offers a brief outline of several significances of fabricating high-sensitivity and low-background interfaces to adjust various targets' behaviors induced via bioactive molecules on the surface. Besides, some important strategies to resist non-specific protein adsorption and cell adhesion, followed by imperative categories of antifouling reagents utilized in the construction of high-performance solid sensory interfaces, are discussed. The next section specifically highlights the various nanocomposite probes based on antifouling-nanomaterials for electrode modification containing carbon nanomaterials, noble metal nanoparticles, magnetic nanoparticles, polymer, and silicon-based materials in terms of nanoparticles, rods, or porous materials through optical or chemical strategies. We specially outline those nanoprobes that are capable of identification in complex media or those using new constructions/methods. Finally, the necessity and requirements for future advances in this emerging field are also presented, followed by opportunities and challenges.

Substrate Materials for Biomolecular Immobilization within Electrochemical Biosensors

Electrochemical biosensors have potential applications for agriculture, food safety, environmental monitoring, sports medicine, biomedicine, and other fields. One of the primary challenges in this field is the immobilization of biomolecular probes atop a solid substrate material with adequate stability, storage lifetime, and reproducibility. This review summarizes the current state of the art for covalent bonding of biomolecules onto solid substrate materials. Early research focused on the use of Au electrodes, with immobilization of biomolecules through ω-functionalized Au-thiol self-assembled monolayers (SAMs), but stability is usually inadequate due to the weak Au-S bond strength. Other noble substrates such as C, Pt, and Si have also been studied. While their nobility has the advantage of ensuring biocompatibility, it also has the disadvantage of making them relatively unreactive towards covalent bond formation. With the exception of Sn-doped In2O3 (indium tin oxide, ITO), most metal oxides are not electrically conductive enough for use within electrochemical biosensors. Recent research has focused on transition metal dichalcogenides (TMDs) such as MoS2 and on electrically conductive polymers such as polyaniline, polypyrrole, and polythiophene. In addition, the deposition of functionalized thin films from aryldiazonium cations has attracted significant attention as a substrate-independent method for biofunctionalization.

An electrochemical sensor for high sensitive determination of lysozyme based on the aptamer competition approach

Protein is a kind of basic substance that constitutes a life body. The determination of protein is very important for the research of biology, medicine, and other fields. Lysozyme is relatively small and simple in structure among all kinds of proteins, so it is often used as a standard target detector in the study of aptamer sensor for protein detection. In this paper, a lysozyme electrochemical sensor based on aptamer competition mechanism is proposed. We have successfully prepared a signal weakening electrochemical sensor based on the lysozyme aptamer competition mechanism. The carboxylated multi-walled carbon nanotubes (MWCNTs) were modified on the glassy carbon electrode, and the complementary aptamer DNA with amino group was connected to MWCNTs. Because of the complementary DNA of daunomycin into the electrode, the electrochemical signal is generated. When there is a target, the aptamer binds to lysozyme with higher binding power, and the original complementary chain breaks down, resulting in the loss of daunomycin inserted into the double chain and the weakening of electrochemical signal. Differential pulse voltammetry was used to determine lysozyme, the response range was 1–500 nM, the correlation coefficient was 0.9995, and the detection limit was 0.5 nM. In addition, the proposed sensor has good selectivity and anti-interference.

Aptasensors for lysozyme detection: Recent advances

Lysozyme is an enzyme existing in multiple organisms where it plays various vital roles. The most important role is its antibacterial activity in the human body; in fact, it is also called "the body's own antibiotic". Despite its proven utility, lysozyme can potentially trigger allergic reactions in sensitive individuals, even in trace amounts. Therefore, lysozyme determination in foods is becoming of paramount importance. Traditional detection methods are expensive, time-consuming and they cannot be applied for fast in-situ quantification. Electrochemical and optical sensors have attracted an increasing attention due to their versatility and ability to reduce the disadvantages of traditional methods. Using an aptamer as the bioreceptor, the sensor selectivity is amplified due to the specific recognition of the analyte. This review is presenting the progresses made in lysozyme determination by means of electrochemical and optical aptasensors in the last five years. A critical overview on the methodologies employed for aptamer immobilization and on the strategies for signal amplification of the assays will be described. Different optical and electrochemical aptasensors will be discussed and compared in terms of analytical performances, versatility and real samples applications.