Single-Walled Carbon Nanotubes as Enhancing Substrates for PNA-Based Amperometric Genosensors

Advancing protein biosensors: redefining detection through innovations in materials, mechanisms, and applications for precision medicine and global diagnostics

Protein biosensors are significant tools in modern diagnostics due to their exceptional sensitivity and specificity in detecting protein biomarkers critical for disease diagnosis, therapeutic monitoring, and biomedical research. Innovations in transduction methods, nanomaterials, and point-of-care system integration have spurred recent advancements in biosensor technology. This summary examines key developments in protein biosensors, focusing on their structure, applications, and future potential. Nanomaterial-enhanced electrochemical biosensors, such as graphene, polyaniline, and carbon nanotubes, offer improved signal transmission due to their large surface area and faster electron transfer rates. Label-free immunosensors activated with gold nanoparticles and MXene-based sensors capable of combined biomarker analysis for detecting ovarian cancer are notable examples. During the COVID-19 pandemic, colorimetric and fluorescence optical biosensors facilitated easier diagnostics. An example of this is the incorporation of SARS-CoV-2 detection technologies into mobile phones. Real-time, label-free tracking with molecular precision is now possible due to the development of new methods, such as CRISPR-based platforms and quartz crystal microbalance (QCM)-based biosensors. This advancement is crucial for effectively managing infectious diseases and cancer. Synthetic fluorescence biosensors increase diagnostics by improving the visualization of protein interactions and cellular communication. Despite these achievements, challenges related to scalability, sustainability, and regulatory compliance remain. Proposed solutions include sustainable biosensor manufacturing, artificial intelligence-enhanced analytics for efficacy evaluation, and multidisciplinary approaches to optimize interaction with decentralised diagnostic systems. This work demonstrates how protein biosensors can advance precision medicine and global health.

Rapid Quantification of SARS-Cov-2 Spike Protein Enhanced with a Machine Learning Technique Integrated in a Smart and Portable Immunosensor

An IoT-WiFi smart and portable electrochemical immunosensor for the quantification of SARS-CoV-2 spike protein was developed with integrated machine learning features. The immunoenzymatic sensor is based on the immobilization of monoclonal antibodies directed at the SARS-CoV-2 S1 subunit on Screen-Printed Electrodes functionalized with gold nanoparticles. The analytical protocol involves a single-step sample incubation. Immunosensor performance was validated in a viral transfer medium which is commonly used for the desorption of nasopharyngeal swabs. Remarkable specificity of the response was demonstrated by testing H1N1 Hemagglutinin from swine-origin influenza A virus and Spike Protein S1 from Middle East respiratory syndrome coronavirus. Machine learning was successfully used for data processing and analysis. Different support vector machine classifiers were evaluated, proving that algorithms affect the classifier accuracy. The test accuracy of the best classification model in terms of true positive/true negative sample classification was 97.3%. In addition, the ML algorithm can be easily integrated into cloud-based portable Wi-Fi devices. Finally, the immunosensor was successfully tested using a third generation replicating incompetent lentiviral vector pseudotyped with SARS-CoV-2 spike glycoprotein, thus proving the applicability of the immunosensor to whole virus detection.

A Folding-Based Electrochemical Aptasensor for the Single-Step Detection of the SARS-CoV-2 Spike Protein

Efficient and timely testing has taken center stage in the management, control, and monitoring of the current COVID-19 pandemic. Simple, rapid, cost-effective diagnostics are needed that can complement current polymerase chain reaction-based methods and lateral flow immunoassays. Here, we report the development of an electrochemical sensing platform based on single-walled carbon nanotube screen-printed electrodes (SWCNT-SPEs) functionalized with a redox-tagged DNA aptamer that specifically binds to the receptor binding domain of the SARS-CoV-2 spike protein S1 subunit. Single-step, reagentless detection of the S1 protein is achieved through a binding-induced, concentration-dependent folding of the DNA aptamer that reduces the efficiency of the electron transfer process between the redox tag and the electrode surface and causes a suppression of the resulting amperometric signal. This aptasensor is specific for the target S1 protein with a dissociation constant (K_D) value of 43 ± 4 nM and a limit of detection of 7 nM. We demonstrate that the target S1 protein can be detected both in a buffer solution and in an artificial viral transport medium widely used for the collection of nasopharyngeal swabs, and that no cross-reactivity is observed in the presence of different, non-target viral proteins. We expect that this SWCNT-SPE-based format of electrochemical aptasensor will prove useful for the detection of other protein targets for which nucleic acid aptamer ligands are made available.

Controlling Dynamic DNA Reactions at the Surface of Single-Walled Carbon Nanotube Electrodes to Design Hybridization Platforms with a Specific Amperometric Readout

Carbon nanotube (CNT)-based electrodes are cheap, highly performing, and robust platforms for the fabrication of electrochemical sensors. Engineering programmable DNA nanotechnologies on the CNT surface can support the construction of new electrochemical DNA sensors providing an amperometric output in response to biomolecular recognition. This is a significant challenge, since it requires gaining control of specific hybridization processes and functional DNA systems at the interface, while limiting DNA physisorption on the electrode surface, which contributes to nonspecific signal. In this study, we provide design rules to program dynamic DNA structures at the surface of single-walled carbon nanotubes electrodes, showing that specific DNA interactions can be monitored through measurement of the current signal provided by redox-tagged DNA strands. We propose the use of pyrene as a backfilling agent to reduce nonspecific adsorption of reporter DNA strands and demonstrate the controlled formation of DNA duplexes on the electrode surface, which we then apply in the design and conduction of programmable DNA strand displacement reactions. Expanding on this aspect, we report the development of novel amperometric hybridization platforms based on artificial DNA structures templated by the small molecule melamine. These platforms enable dynamic strand exchange reactions orthogonal to conventional toehold-mediated strand displacement and may support new strategies in electrochemical sensing of biomolecular targets, combining the physicochemical properties of nanostructured carbon-based materials with programmable nucleic acid hybridization.

PNA-functionalized magnetic microbeads as substrates for enzyme-labelled voltammetric genoassay for DNA sensing applied to identification of GMO in food

A novel enzyme-labelled voltammetric magnetogenoassay for DNA sensing based on the use of carboxyl-surface coated magnetic microbeads functionalized with PNA probes and subsequent read-out on screen-printed electrode (SPE) substrates was developed. The assay was validated for determination of non-amplified genomic DNA from genetically modified Roundup Ready soy. Outstanding performance with respect to other genoassays requiring preliminary amplification of target DNA via PCR was demonstrated. The analytical performance was also improved compared to previous methods based on the immobilization of the same PNA probes on SPE substrates, since the method was found capable of achieving LOD and LOQ of 415 fM and 995 fM, respectively. The ability of the magnetogenoassay to detect the presence of Roundup Ready soy DNA sequence was tested on genomic DNA extract from European Reference Material soy flours, demonstrating the capability of the method to match the European Union regulation for labelling of food containing a percentage of GM products greater than 0,9%.

Electrochemical biosensors: perspective on functional nanomaterials for on-site analysis

BACKGROUND

The electrochemical biosensor is one of the typical sensing devices based on transducing the biochemical events to electrical signals. In this type of sensor, an electrode is a key component that is employed as a solid support for immobilization of biomolecules and electron movement. Thanks to numerous nanomaterials that possess the large surface area, synergic effects are enabled by improving loading capacity and the mass transport of reactants for achieving high performance in terms of analytical sensitivity.

MAIN BODY

We categorized the current electrochemical biosensors into two groups, carbon-based (carbon nanotubes and graphene) and non-carbon-based nanomaterials (metallic and silica nanoparticles, nanowire, and indium tin oxide, organic materials). The carbon allotropes can be employed as an electrode and supporting scaffolds due to their large active surface area as well as an effective electron transfer rate. We also discussed the non-carbon nanomaterials that are used as alternative supporting components of the electrode for improving the electrochemical properties of biosensors.

CONCLUSION

Although several functional nanomaterials have provided the innovative solid substrate for high performances, developing on-site version of biosensor that meets enough sensitivity along with high reproducibility still remains a challenge. In particular, the matrix interference from real samples which seriously affects the biomolecular interaction still remains the most critical issues that need to be solved for practical aspect in the electrochemical biosensor.

Nanomaterials for Healthcare Biosensing Applications

In recent years, an increasing number of nanomaterials have been explored for their applications in biomedical diagnostics, making their applications in healthcare biosensing a rapidly evolving field. Nanomaterials introduce versatility to the sensing platforms and may even allow mobility between different detection mechanisms. The prospect of a combination of different nanomaterials allows an exploitation of their synergistic additive and novel properties for sensor development. This paper covers more than 290 research works since 2015, elaborating the diverse roles played by various nanomaterials in the biosensing field. Hence, we provide a comprehensive review of the healthcare sensing applications of nanomaterials, covering carbon allotrope-based, inorganic, and organic nanomaterials. These sensing systems are able to detect a wide variety of clinically relevant molecules, like nucleic acids, viruses, bacteria, cancer antigens, pharmaceuticals and narcotic drugs, toxins, contaminants, as well as entire cells in various sensing media, ranging from buffers to more complex environments such as urine, blood or sputum. Thus, the latest advancements reviewed in this paper hold tremendous potential for the application of nanomaterials in the early screening of diseases and point-of-care testing.

Recent advances in nanomaterial-based electrochemical and optical sensing platforms for microRNA assays

This review describes recent efforts in the application of nanomaterials as sensing elements in electrochemical and optical miRNAs assays.