A novel approach for amine derivatization of MoS 2 nanosheets and their application toward label-free immunosensor

A novel electrochemical immunosensor for the ultrasensitive detection of vascular endothelial growth factor based on MB@Cu-MOFs/MWCNTs composite

A novel proposal is introduced with an unlabeled electrochemical immunosensor for the detection of tumor broad-spectrum biomarker vascular endothelial growth factor (VEGF165) Copper-based metal organic frameworks (Cu MOFs)-carbon nanotubes (MWCNTs) were employed as its substrates, functionalized with methylene blue (MB) for signal enhancement. Cu-MOFs-MWCNTs nanocomposites were synthesized successfully via a solvothermal method and were then deposited on the surface of a glassy carbon electrode (GCE), with the addition of methylene blue to amplify the signal. Due to the expansive specific surface area provided by the carbon nanotubes and the amino groups facilitated by the metal-organic framework nanomaterials, the anti-VEGF165 monoclonal antibody was immobilized on the electrochemical immunosensor through covalent bonding, which could bind specifically to VEGF165, thereby causing a detectable change in the current. The developed immunosensor exhibited a linear detection range for VEGF165 spanning from 1 to 100,000 pg/ml, with the R2 value of 0.997 by differential pulse voltammetry (DPV) method, and the limit of detection was as low as 0.9686. Additionally, the electrochemical immunosensor presented commendable selectivity, availability, and reproducibility, along with an effective capacity for detecting VEGF165 in clinical samples. Consequently, the immunosensor is expected to revolutionize early screening for VEGF165-related diseases, which offer a promising, cost-effective, and precise diagnostic tool for clinical utility.

Development of transition metal oxide platforms for aptasensing of PSA in cell cultures

In this study, a novel aptasensor based on a transition metal oxide-modified pencil graphite electrode (PGE) was developed for the diagnosis of early-stage prostate cancer (PCa) via monitoring the prostate-specific antigen (PSA), which is the main biomarker for PCa. Single-use PGEs modified with pulsed deposited manganese oxide (MnOx) film were used to attach the amino-terminated aptamer specific to the PSA via carbodiimide chemistry. The designed aptasensor was placed in an electrochemical cell containing ferri/ferrocyanide ions as a redox probe to measure the charge transfer resistances (Rct) of the electrode surface by electrochemical impedance spectroscopy (EIS) to follow the response of each modification step. The effect of the medium pH on the ionic structure of the aptamer molecule according to its pI value and, thus, the reversing of the direction of the response (ΔRct) by the pH change was also discussed. The level of PSA secreted from PCa cells was investigated using impedimetric transduction. The specificity of the aptasensor was validated through selectivity studies against non-specific tumor markers like VEGF and different cancer cell lines including breast cancer and androgen-insensitive prostate cancer. The developed system showcases a label-free, fast, specific, and cost-effective approach for PSA detection, highlighting the importance of medium pH and the electrostatic environment on the aptamer's response. Our work emphasizes the potential for such aptasensors in clinical diagnostics and paves the way for further exploration into using transition metal oxides in biosensing applications.

Advancement of metal oxide nanomaterials on agri-food fronts

The application of metal oxide nanomaterials (MOx NMs) in the agrifood industry offers innovative solutions that can facilitate a paradigm shift in a sector that is currently facing challenges in meeting the growing requirements for food production, while safeguarding the environment from the impacts of current agriculture practices. This review comprehensively illustrates recent advancements and applications of MOx for sustainable practices in the food and agricultural industries and environmental preservation. Relevant published data point out that MOx NMs can be tailored for specific properties, enabling advanced design concepts with improved features for various applications in the agrifood industry. Applications include nano-agrochemical formulation, control of food quality through nanosensors, and smart food packaging. Furthermore, recent research suggests MOx's vital role in addressing environmental challenges by removing toxic elements from contaminated soil and water. This mitigates the environmental effects of widespread agrichemical use and creates a more favorable environment for plant growth. The review also discusses potential barriers, particularly regarding MOx toxicity and risk evaluation. Fundamental concerns about possible adverse effects on human health and the environment must be addressed to establish an appropriate regulatory framework for nano metal oxide-based food and agricultural products.

Biomolecule-functionalized nanoformulations for prostate cancer theranostics

BACKGROUND

Even with the advancement in the areas of cancer nanotechnology, prostate cancer still poses a major threat to men's health. Nanomaterials and nanomaterial-derived theranostic systems have been explored for diagnosis, imaging, and therapy for different types of cancer still, for prostate cancer they have not delivered at full potential because of the limitations like in vivo biocompatibility, immune responses, precise targetability, and therapeutic outcome associated with the nanostructured system.

AIM OF REVIEW

Functionalizing nanomaterials with different biomolecules and bioactive agents provides advantages like specificity towards cancerous tumors, improved circulation time, and modulation of the immune response leading to early diagnosis and targeted delivery of cargo at the site of action.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In this review, we have emphasized the classification and comparison of various nanomaterials based on biofunctionalization strategy and source of biomolecules such that it can be used for possible translation in clinical settings and future developments. This review highlighted the opportunities for embedding highly specific biological targeting moieties (antibody, aptamer, oligonucleotides, biopolymer, peptides, etc.) on nanoparticles which can improve the detection of prostate cancer-associated biomarkers at a very low limit of detection, direct visualization of prostate tumors and lastly for its therapy. Lastly, special emphasis was given to biomimetic nanomaterials which include functionalization with extracellular vesicles, exosomes and viral particles and their application for prostate cancer early detection and drug delivery. The present review paves a new pathway for next-generation biofunctionalized nanomaterials for prostate cancer theranostic application and their possibility in clinical translation.

Functionalization of 2D MoS2 Nanosheets with Various Metal and Metal Oxide Nanostructures: Their Properties and Application in Electrochemical Sensors

Two-dimensional transition metal dichalcogenides (2D TMDs) have gained considerable attention due to their distinctive properties and broad range of possible applications. One of the most widely studied transition metal dichalcogenides is molybdenum disulfide (MoS₂). The 2D MoS₂ nanosheets have unique and complementary properties to those of graphene, rendering them ideal electrode materials that could potentially lead to significant benefits in many electrochemical applications. These properties include tunable bandgaps, large surface areas, relatively high electron mobilities, and good optical and catalytic characteristics. Although the use of 2D MoS₂ nanosheets offers several advantages and excellent properties, surface functionalization of 2D MoS₂ is a potential route for further enhancing their properties and adding extra functionalities to the surface of the fabricated sensor. The functionalization of the material with various metal and metal oxide nanostructures has a significant impact on its overall electrochemical performance, improving various sensing parameters, such as selectivity, sensitivity, and stability. In this review, different methods of preparing 2D-layered MoS₂ nanomaterials, followed by different surface functionalization methods of these nanomaterials, are explored and discussed. Finally, the structure-properties relationship and electrochemical sensor applications over the last ten years are discussed. Emphasis is placed on the performance of 2D MoS₂ with respect to the performance of electrochemical sensors, thereby giving new insights into this unique material and providing a foundation for researchers of different disciplines who are interested in advancing the development of MoS₂-based sensors.

Amine-functionalized Cu-MOF nanospheres towards label-free hepatitis B surface antigen electrochemical immunosensors

Metal-organic framework (MOF) nanomaterials offer a wide range of promising applications due to their unique properties, including open micro- and mesopores and richness of functionalization. Herein, a facile synthesis via a solvothermal method was successfully employed to prepare amine-functionalized Cu-MOF nanospheres. Moreover, the growth and the morphology of the nanospheres were optimized by the addition of PVP and TEA. By functionalization with an amine group, the immobilization of a bioreceptor towards the detection of hepatitis B infection biomarker, i.e., hepatitis B surface antigen (HBsAg), could be realized. The immobilization of the bioreceptor/antibody to Cu-MOF nanospheres was achieved through a covalent interaction between the carboxyl group of the antibodies and the amino-functional ligand in Cu-MOF via EDC/NHS coupling. The amine-functionalized Cu-MOF nanospheres act not only as a nanocarrier for antibody immobilization, but also as an electroactive material to generate the electrochemical signal. The electrochemical sensing performance was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). The results showed that the current response proportionally decreased with the increase of HBsAg concentration. More importantly, the sensing performance of the amine-functionalized Cu-MOF nanospheres towards HBsAg detection was found to be consistent in real human serum media. This strategy successfully resulted in wide linear range detection of HBsAg from 1 ng mL-1 to 500 ng mL-1 with a limit of detection (LOD) of 730 pg mL-1. Thus, our approach provides a facile and low-cost synthesis process of an electrochemical immunosensor and paves the way to potentially utilize MOF-based nanomaterials for clinical use.

Microfluidic-Based Electrochemical Immunosensing of Ferritin

Ferritin is a clinically important biomarker which reflects the state of iron in the body and is directly involved with anemia. Current methods available for ferritin estimation are generally not portable or they do not provide a fast response. To combat these issues, an attempt was made for lab-on-a-chip-based electrochemical detection of ferritin, developed with an integrated electrochemically active screen-printed electrode (SPE), combining nanotechnology, microfluidics, and electrochemistry. The SPE surface was modified with amine-functionalized graphene oxide to facilitate the binding of ferritin antibodies on the electrode surface. The functionalized SPE was embedded in the microfluidic flow cell with a simple magnetic clamping mechanism to allow continuous electrochemical detection of ferritin. Ferritin detection was accomplished via cyclic voltammetry with a dynamic linear range from 7.81 to 500 ng·mL⁻¹ and an LOD of 0.413 ng·mL⁻¹. The sensor performance was verified with spiked human serum samples. Furthermore, the sensor was validated by comparing its response with the response of the conventional ELISA method. The current method of microfluidic flow cell-based electrochemical ferritin detection demonstrated promising sensitivity and selectivity. This confirmed the plausibility of using the reported technique in point-of-care testing applications at a much faster rate than conventional techniques.

A colorimetric aptamer-based method for detection of cadmium using the enhanced peroxidase-like activity of Au-MoS2 nanocomposites

In this work, a colorimetric aptamer-based method for detection of cadmium using gold nanoparticles modified MoS₂ nanocomposites as enzyme mimic is established. In short, biotinylated Cd²⁺ aptamers are immobilized by biotin-avidin binding on the bottoms of the microplate, the complementary strands of Cd²⁺ aptamers are connected to the Au-MoS₂ nanocomposites which have the function of enhanced peroxidase-like activity. The csDNA-Au-MoS₂ signal probe and target Cd²⁺ compete for binding Cd²⁺ aptamer, the color change can be observed by addition of chromogenic substrate, thereby realizing visual detection of Cd²⁺. The absorbance of the solution at 450 nm has a clear linear relationship with the Cd²⁺ concentration. The linear range is 1-500 ng/mL, and the limit of detection is 0.7 ng/mL. The assay was used to test white wine samples, the results are consistent with those of atomic absorption spectrometry; which prove that this method can be used for detection of Cd²⁺ in real samples.

Molybdenum disulfide nanosheets: From exfoliation preparation to biosensing and cancer therapy applications

Over the past few decades, nanotechnology has developed rapidly. Various nanomaterials have been gradually applied in different fields. As a kind of two-dimensional (2D) layered nanomaterial with a graphene-like structure, molybdenum disulfide (MoS₂) nanosheets have broad research prospects in the fields of tumor photothermal therapy, biosensors and other biomedical fields because of their unique band gap structure and physical, chemical and optical properties. In this paper, the latest research progress on MoS₂ is briefly summarized. Several commonly used exfoliation methods for the preparation of MoS₂ nanosheets are reviewed based on the studies in the past five years. Additionally, the current research status of MoS₂ nanosheets in the field of biomedicine is introduced. At the end of this review, a brief overview of the limitations of MoS₂ research and its future prospects in the field of biomedicine is also provided.

Lysine-Functionalized Tungsten Disulfide Quantum Dots as Artificial Enzyme Mimics for Oxidative Stress Biomarker Sensing

The color generating from the biochemical reaction between 3,3',5,5'-tetramethylbenzidine and Lysine@WS₂ QDs was used a signal for the detection of hydrogen peroxide. The QDs were prepared using a combination of techniques, that is, probe sonication and hydrothermal treatment. Analysis via UV-vis spectroscopy, Fourier transform infrared and Raman spectroscopy, X-ray diffraction, energy-dispersive spectroscopy, and transmission electron microscopy yielded detailed information on the nature and characteristics of these quantum dots. Furthermore, as-synthesized quantum dots were studied for their capability to mimic peroxidase enzyme using 3,3',5,5'-tetramethylbenzidine as a substrate. Consequently, a colorimetric sensor utilizing Lysine@WS₂ QDs could detect hydrogen peroxide in a range of 0.1-60 μM with a response time of 5 min. The same material was used for H₂O₂ detection using impedance spectroscopy, which yielded a dynamic range of 0.1-350 μM with a response time of 30-40 s.

2D Materials in Development of Electrochemical Point-of-Care Cancer Screening Devices

Effective cancer treatment requires early detection and monitoring the development progress in a simple and affordable manner. Point-of care (POC) screening can provide a portable and inexpensive tool for the end-users to conveniently operate test and screen their health conditions without the necessity of special skills. Electrochemical methods hold great potential for clinical analysis of variety of chemicals and substances as well as cancer biomarkers due to their low cost, high sensitivity, multiplex detection ability, and miniaturization aptitude. Advances in two-dimensional (2D) material-based electrochemical biosensors/sensors are accelerating the performance of conventional devices toward more practical approaches. Here, recent trends in the development of 2D material-based electrochemical biosensors/sensors, as the next generation of POC cancer screening tools, are summarized. Three cancer biomarker categories, including proteins, nucleic acids, and some small molecules, will be considered. Various 2D materials will be introduced and their biomedical applications and electrochemical properties will be given. The role of 2D materials in improving the performance of electrochemical sensing mechanisms as well as the pros and cons of current sensors as the prospective devices for POC screening will be emphasized. Finally, the future scopes of implementing 2D materials in electrochemical POC cancer diagnostics for the clinical translation will be discussed.

Recent advances in molybdenum disulfide-based electrode materials for electroanalytical applications

The primary objective of this review article is to summarize the development and structural diversity of 2D/3D molybdenum disulfide (MoS₂) based modified electrodes for electrochemical sensors and biosensor applications. Hydrothermal, mechanical, and ultrasonic techniques and solution-based exfoliation have been used to synthesize graphene-like 2D MoS₂ layers. The unique physicochemical properties of MoS₂ and its nanocomposites, including high mechanical strength, high carrier transport, large surface area, excellent electrical conductivity, and rapid electron transport rate, render them useful as efficient transducers in various electrochemical applications. The present review summarizes 2D/3D MoS₂-based nanomaterials as an electrochemical platform for the detection and analysis of various biomolecules (e.g., neurotransmitters, NADH, glucose, antibiotics, DNA, proteins, and bacteria) and hazardous chemicals (e.g., heavy metal ions, organic compounds, and pesticides). The substantial improvements that have been achieved in the performance of enzyme-based amperometry, chemiluminescence, and nucleic acid sensors incorporating MoS₂-based chemically modified electrodes are also addressed. We also summarize key sensor parameters such as limits of detection (LODs), sensitivity, selectivity, response time, and durability, as well as real applications of the sensing systems in the environmental, pharmaceutical, chemical, industrial, and food analysis fields. Finally, the remaining challenges in designing MoS₂ nanostructures suitable for electroanalytical applications are outlined. Graphical abstract • MoS₂ based materials exhibit high conductivity and improved electrochemical performance with great potential as a sensing electrode. • The role of MoS₂ nanocomposite films and their detection strategies were reviewed. • Biomarkers detection for disease identification and respective clinical treatments were discussed. • Future Challenges, as well as possible research development for "MoS₂ nanocomposites", are suggested.