Two-Dimensional Non-Carbon Materials-Based Electrochemical Printed Sensors: An Updated Review

Recently, there has been increasing interest in electrochemical printed sensors for a wide range of applications such as biomedical, pharmaceutical, food safety, and environmental fields. A major challenge is to obtain selective, sensitive, and reliable sensing platforms that can meet the stringent performance requirements of these application areas. Two-dimensional (2D) nanomaterials advances have accelerated the performance of electrochemical sensors towards more practical approaches. This review discusses the recent development of electrochemical printed sensors, with emphasis on the integration of non-carbon 2D materials as sensing platforms. A brief introduction to printed electrochemical sensors and electrochemical technique analysis are presented in the first section of this review. Subsequently, sensor surface functionalization and modification techniques including drop-casting, electrodeposition, and printing of functional ink are discussed. In the next section, we review recent insights into novel fabrication methodologies, electrochemical techniques, and sensors' performances of the most used transition metal dichalcogenides materials (such as MoS₂, MoSe₂, and WS₂), MXenes, and hexagonal boron-nitride (hBN). Finally, the challenges that are faced by electrochemical printed sensors are highlighted in the conclusion. This review is not only useful to provide insights for researchers that are currently working in the related area, but also instructive to the ones new to this field.

A Review of Transition Metal Dichalcogenides-Based Biosensors

Transition metal dichalcogenides (TMDCs) are widely used in biosensing applications due to their excellent physical and chemical properties. Due to the properties of biomaterial targets, the biggest challenge that biosensors face now is how to improve the sensitivity and stability. A lot of materials had been used to enhance the target signal. Among them, TMDCs show excellent performance in enhancing biosensing signals because of their metallic and semi-conducting electrical capabilities, tunable band gap, large specific surface area and so on. Here, we review different functionalization methods and research progress of TMDCs-based biosensors. The modification methods of TMDCs for biosensor fabrication mainly include two strategies: non-covalent and covalent interaction. The article summarizes the advantages and disadvantages of different modification strategies and their effects on biosensing performance. The authors present the challenges and issues that TMDCs need to be addressed in biosensor applications. Finally, the review expresses the positive application prospects of TMDCs-based biosensors in the future.

Two-dimensional materials in biomedical, biosensing and sensing applications

Two-dimensional (2D) materials are at the forefront of materials research. Here we overview their applications beyond graphene, such as transition metal dichalcogenides, monoelemental Xenes (including phosphorene and bismuthene), carbon nitrides, boron nitrides along with transition metal carbides and nitrides (MXenes). We discuss their usage in various biomedical and environmental monitoring applications, from biosensors to therapeutic treatment agents, their toxicity and their utility in chemical sensing. We highlight how a specific chemical, physical and optical property of 2D materials can influence the performance of bio/sensing, improve drug delivery and photo/thermal therapy as well as affect their toxicity. Such properties are determined by crystal phases electrical conductivity, degree of exfoliation, surface functionalization, strong photoluminescence, strong optical absorption in the near-infrared range and high photothermal conversion efficiency. This review conveys the great future of all the families of 2D materials, especially with the expanding 2D materials' landscape as new materials emerge such as germanene and silicene.

Electrically-Transduced Chemical Sensors Based on Two-Dimensional Nanomaterials

Electrically-transduced sensors, with their simplicity and compatibility with standard electronic technologies, produce signals that can be efficiently acquired, processed, stored, and analyzed. Two dimensional (2D) nanomaterials, including graphene, phosphorene (BP), transition metal dichalcogenides (TMDCs), and others, have proven to be attractive for the fabrication of high-performance electrically-transduced chemical sensors due to their remarkable electronic and physical properties originating from their 2D structure. This review highlights the advances in electrically-transduced chemical sensing that rely on 2D materials. The structural components of such sensors are described, and the underlying operating principles for different types of architectures are discussed. The structural features, electronic properties, and surface chemistry of 2D nanostructures that dictate their sensing performance are reviewed. Key advances in the application of 2D materials, from both a historical and analytical perspective, are summarized for four different groups of analytes: gases, volatile compounds, ions, and biomolecules. The sensing performance is discussed in the context of the molecular design, structure-property relationships, and device fabrication technology. The outlook of challenges and opportunities for 2D nanomaterials for the future development of electrically-transduced sensors is also presented.

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.

Recent advances in signal amplification strategy based on oligonucleotide and nanomaterials for microRNA detection-a review

MicroRNAs (MiRNAs) play multiple crucial regulating roles in cell which can regulate one third of protein-coding genes. MiRNAs participate in the developmental and physiological processes of human body, while their aberrant adjustment will be more likely to trigger diseases such as cancers, kidney disease, central nervous system diseases, cardiovascular diseases, diabetes, viral infections and so on. What's worse, for the detection of miRNAs, their small size, high sequence similarity, low abundance and difficult extraction from cells impose great challenges in the analysis. Hence, it's necessary to fabricate accurate and sensitive biosensing platform for miRNAs detection. Up to now, researchers have developed many signal-amplification strategies for miRNAs detection, including hybridization chain reaction, nuclease amplification, rolling circle amplification, catalyzed hairpin assembly amplification and nanomaterials based amplification. These methods are typical, feasible and frequently used. In this review, we retrospect recent advances in signal amplification strategies for detecting miRNAs and point out the pros and cons of them. Furthermore, further prospects and promising developments of the signal-amplification strategies for detecting miRNAs are proposed.

Nucleic acid-functionalized transition metal nanosheets for biosensing applications

In clinical diagnostics, as well as food and environmental safety practices, biosensors are powerful tools for monitoring biological or biochemical processes. Two-dimensional (2D) transition metal nanomaterials, including transition metal chalcogenides (TMCs) and transition metal oxides (TMOs), are receiving growing interest for their use in biosensing applications based on such unique properties as high surface area and fluorescence quenching abilities. Meanwhile, nucleic acid probes based on Watson-Crick base-pairing rules are also being widely applied in biosensing based on their excellent recognition capability. In particular, the emergence of functional nucleic acids in the 1980s, especially aptamers, has substantially extended the recognition capability of nucleic acids to various targets, ranging from small organic molecules and metal ions to proteins and cells. Based on π-π stacking interaction between transition metal nanosheets and nucleic acids, biosensing systems can be easily assembled. Therefore, the combination of 2D transition metal nanomaterials and nucleic acids brings intriguing opportunities in bioanalysis and biomedicine. In this review, we summarize recent advances of nucleic acid-functionalized transition metal nanosheets in biosensing applications. The structure and properties of 2D transition metal nanomaterials are first discussed, emphasizing the interaction between transition metal nanosheets and nucleic acids. Then, the applications of nucleic acid-functionalized transition metal nanosheet-based biosensors are discussed in the context of different signal transducing mechanisms, including optical and electrochemical approaches. Finally, we provide our perspectives on the current challenges and opportunities in this promising field.

Recent Advances in Synthesis and Biomedical Applications of Two-Dimensional Transition Metal Dichalcogenide Nanosheets

During recent decades, a giant leap in the development of nanotechnology has been witnessed. Numerous nanomaterials with different dimensions and unprecedented features have been developed and provided unimaginably wide scope to solve the challenging problems in biomedicine, such as cancer diagnosis and therapy. Recently, two-dimensional (2D) transition metal dichalcogenide (TMDC) nanosheets (NSs), including MoS₂ , WS₂ , and etc., have emerged as novel inorganic graphene analogues and attracted tremendous attention due to their unique structures and distinctive properties, and opened up great opportunities for biomedical applications, including ultrasensitive biosensing, biological imaging, drug delivery, cancer therapy, and antibacterial treatment. A comprehensive overview of different synthetic methods of ultrathin 2D TMDC NSs and their state-of-the-art biomedical applications, especially those that have appeared in the past few years, is presented. At the end of this review, the future opportunities and challenges for 2D TMDC NSs in biomedicine are also discussed.

Highly manufacturable graphene oxide biosensor for sensitive Interleukin-6 detection

Reduced graphene oxide can be used as a sensitive label-free sensor transducer for detection of Interleukin-6 proteins, by overcoming the variable coverage and high electrical resistance, via ethanol Chemical Vapour Deposition (CVD).