Self-assembled GA-Repeated Peptides as a Biomolecular Scaffold for Biosensing with MoS2 Electrochemical Transistors

Hierarchical Assembly of Hemin-Peptide Catalytic Systems on Graphite Surfaces

The formation of molecular hybrid systems with cofactors and peptides on graphite electrodes has recently been demonstrated. The design of peptide sequences is crucial for forming robust catalytic molecular systems on electrodes. However, the relationship between peptide sequences, molecular structure, and catalytic performance has not been fully explored. In this study, we employed peptides with simple dipeptide repeats, which effectively immobilize hemin, to construct a stable catalytic system and investigated the molecular basis of their self-assembly and catalytic activity by varying the sequence. Among peptides containing the dipeptide sequences (YH, VH, and LH), YH demonstrated the most efficient immobilization of hemin, which is catalytically active in electrochemical reactions. Using advanced molecular visualization techniques, specifically frequency modulation atomic force microscopy (FM-AFM), we characterized the well-ordered structures of these peptides on graphite electrodes, revealing their molecular-scale organization. Our findings in electrochemical characterizations include a quantitative evaluation of the surface density of hemin immobilized by self-assembled peptides and the catalytic activity of the peptide-hemin hybrid system under electrochemical conditions in the presence of H2O2. The strong peptide-peptide and peptide-hemin interactions, facilitated by π-π interactions of tyrosine residues, contribute to the system's stability and efficiency. The dipeptide repeats serve as a useful platform to investigate the role of important amino acids, beyond histidine, in stably immobilizing cofactors. These results highlight the potential for developing durable and efficient catalytic interfaces in electrochemical applications.

Protein Detection Based on Field-Effect Transistor Biosensors for Diagnosing Diseases

Proteins have been one of the most important biomarkers for diagnosing diseases, and field-effect transistor (FET) biosensors possess high sensitivity; are label-free; and feature real-time detection, rapidity, and easy integration for protein detection. FET biosensors are mainly made up of FET parts, such as channel materials, and bio parts, such as receptors. This Tutorial provides an in-depth exploration of FET biosensors for protein detection from the composition perspective and discusses the commercialization of point-of-care diagnostics of proteins based on FET biosensors.

Multifunctional Integrated Biosensors Based on Two-Dimensional Field-Effect Transistors

In recent years, field-effect transistor (FET) sensing technology has attracted significant attention owing to its noninvasive, label-free, real-time, and user-friendly detection capabilities. Owing to the large specific surface area, high flexibility, and excellent conductivity of two-dimensional (2D) materials, FET biosensors based on 2D materials have demonstrated unique potential in biomarker analysis and healthcare applications, driving continuous innovation and transformation in the field. Here, we review recent trends in the development of 2D FET biosensors based on key performance metrics and main characteristics, and we also discuss structural designs and modification strategies for biosensing devices utilizing graphene, transition metal dichalcogenides, black phosphorus, and other 2D materials to enhance key performance metrics. Finally, we offer insights into future directions for biosensor advancements, discuss potential improvements, and present new recommendations for practical clinical applications.

Enantioselective Detection of Gaseous Odorants with Peptide-Graphene Sensors Operating in Humid Environments

Replicating the sense of smell presents an ongoing challenge in the development of biomimetic devices. Olfactory receptors exhibit remarkable discriminatory abilities, including the enantioselective detection of individual odorant molecules. Graphene has emerged as a promising material for biomimetic electronic devices due to its unique electrical properties and exceptional sensitivity. However, the efficient detection of nonpolar odor molecules using transistor-based graphene sensors in a gas phase in environmental conditions remains challenging due to high sensitivity to water vapor. This limitation has impeded the practical development of gas-phase graphene odor sensors capable of selective detection, particularly in humid environments. In this study, we address this challenge by introducing peptide-functionalized graphene sensors that effectively mitigate undesired responses to changes in humidity. Additionally, we demonstrate the significant role of humidity in facilitating the selective detection of odorant molecules by the peptides. These peptides, designed to mimic a fruit fly olfactory receptor, spontaneously assemble into a monomolecular layer on graphene, enabling precise and specific odorant detection. The developed sensors exhibit notable enantioselectivity, achieving a remarkable 35-fold signal contrast between d- and l-limonene. Furthermore, these sensors display distinct responses to various other biogenic volatile organic compounds, demonstrating their versatility as robust tools for odor detection. By acting as both a bioprobe and an electrical signal amplifier, the peptide layer represents a novel and effective strategy to achieve selective odorant detection under normal atmospheric conditions using graphene sensors. This study offers valuable insights into the development of practical odor-sensing technologies with potential applications in diverse fields.

Two-Dimensional Layered Nanomaterials Steering Self-Assembly of Dodecapeptides with Three Building Blocks

Self-assembly of peptides on layered nanomaterials such as graphite and MoS2 in the formation of long-range ordered two-dimensional nanocrystal patterns leading to its potential applications for biosensing and bioelectronics has attracted significant interest in nanoscience and nanotechnology. However, controlling the self-assembly of peptides on nanomaterials is still challenging due to the unclear role of nanomaterials in steering self-assembly. Here, we used the in-situ AFM technique to capture different changes of peptide coverage as well as lengthening and widening rates depending on peptide concentrations, show the distinct boundary dynamics of two stabilized peptide domains, and resolve the molecular resolution structural differences and specific orientation of peptide on both nanomaterials. Moreover, ex-situ results showed that the nanomaterial layers tuned the opposite changes of nanowire heights and densities and displayed the different water-resistance stabilities on both nanomaterials. This work provides a basis for understanding nanomaterials steering peptide self-assembly and using hybrid bionanomaterials as a scaffold, enabling for potential biosensing and bioelectronics applications.

Amplified detection of SARS-COV-2 B.1.1.529 (Omicron) gene oligonucleotides based on exonuclease III-aided MoS2 /AIE nanoprobes

The coronavirus disease-2019 pandemic reflects the underdevelopment of point-of-care diagnostic technology. Nuclei acid (NA) detection is the "gold standard" method for the early diagnosis of the B.1.1.529 (Omicron) variant of severe acute respiratory syndrome-coronavirus disease-2. Polymerase chain reaction is the main method for NA detection but requires considerable manpower and sample processing taking ≥ 3 h. To simplify the operation processes and reduce the detection time, exonuclease III (Exo III)-aided MoS2 /AIE nanoprobes were developed for rapid and sensitive detection of the oligonucleotides of Omicron. Molybdenum disulfide (MoS2 ) nanosheets with excellent optical absorbance and distinguishable affinity to single-strand and duplex DNAs were applied as quenchers, and aggregation-induced emission (AIE) molecules with high luminous efficiency were designed as donor in fluorescence resonance energy transfer-based nanoprobes. Exo III with catalytic capability was used for signal amplification to increase the sensitivity of detection. The composite nanoprobes detected the mutated nucleocapsid (N)-gene and spike (S)-gene oligonucleotides of Omicron within 40 min with a limit of detection of 4.7 pM, and showed great potential for application in community medicine.

Protein-Assisted Molybdenum Disulfide as Biomimetic Nanozyme for Antibacterial Application

Molybdenum-based nanomaterials with variable oxidation states can be developed as nanozyme catalysts. In this work, we developed a one-pot method for the preparation of molybdenum disulfide assisted by protein. Protamine was used as a cationic template to link molybdate anions and form complexes. During hydrothermal synthesis, protamine can affect the nucleation process of molybdenum disulfide and inhibit their aggregation, which facilitates the fabrication of small-sized molybdenum disulfide nanoparticles. Moreover, the abundant amino/guanidyl groups of protamine could both physically adsorb and chemically bond to molybdenum disulfide and further modulate the crystal structures. The optimized size and crystalline structure enabled a higher exposure of active sites, which enhanced the peroxidase-like activity of molybdenum disulfide/protamine nanocomposites. Meanwhile, the antibacterial activity of protamine was retained in the molybdenum disulfide/protamine nanocomposites, which could synergize with the peroxidase-like activity of molybdenum disulfide to kill bacteria. Therefore, the molybdenum disulfide/protamine nanocomposites are good candidates for antibacterial agents with lower chances of antimicrobial resistance. This study establishes an easy way to design artificial nanozymes by compounding suitable components.