Diamine Oxidase-Conjugated Multiwalled Carbon Nanotubes to Facilitate Electrode Surface Homogeneity

A comprehensive review on enzyme-based biosensors: Advanced analysis and emerging applications in nanomaterial-enzyme linkage

Biosensors with nanomaterials and enzymes detect and quantify specific targets in samples, converting recognition into measurable signals. The study explores the intrinsic synergy between these elements for detecting and quantifying particular targets in biological and environmental samples, with results demonstrated through bibliometric analysis and a comprehensive review of enzyme-based biosensors. Using WoS, 57,331 articles were analyzed and refined to 880. Key journals, countries, institutions, and relevant authors were identified. The main areas highlighted the multidisciplinary nature of the field, and critical keywords identified five thematic clusters, revealing the primary nanoparticles used (CNTs, graphene, AuNPs), major application fields, basic application themes, and niche topics such as sensitive detection, peroxidase activity, and quantum dot utilization. The biosensor overview covered nanomaterials and their primary applications, addressing recent advances and inherent challenges. Patent analysis emphasized the U.S. leadership in the industrial sector, contrasting with China's academic prominence. Future studies should focus on enhancing biosensor portability and analysis speed, with challenges encompassing efficient integration with recent technologies and improving stability and reproducibility in the nanomaterial-enzyme interaction.

Antibiofilm Effect of Nitric Acid-Functionalized Carbon Nanotube-Based Surfaces against E. coli and S. aureus

Chemically modified carbon nanotubes are recognized as effective materials for tackling bacterial infections. In this study, pristine multi-walled carbon nanotubes (p-MWCNTs) were functionalized with nitric acid (f-MWCNTs), followed by thermal treatment at 600 °C, and incorporated into a poly(dimethylsiloxane) (PDMS) matrix. The materials' textural properties were evaluated, and the roughness and morphology of MWCNT/PDMS composites were assessed using optical profilometry and scanning electron microscopy, respectively. The antibiofilm activity of MWCNT/PDMS surfaces was determined by quantifying culturable Escherichia coli and Staphylococcus aureus after 24 h of biofilm formation. Additionally, the antibacterial mechanisms of MWCNT materials were identified by flow cytometry, and the cytotoxicity of MWCNT/PDMS composites was tested against human kidney (HK-2) cells. The results revealed that the antimicrobial activity of MWCNTs incorporated into a PDMS matrix can be efficiently tailored through nitric acid functionalization, and it can be increased by up to 49% in the absence of surface carboxylic groups in f-MWCNT samples heated at 600 °C and the presence of redox activity of carbonyl groups. MWCNT materials changed the membrane permeability of both Gram-negative and Gram-positive bacteria, while they only induced the production of ROS in Gram-positive bacteria. Furthermore, the synthesized composites did not impact HK-2 cell viability, confirming the biocompatibility of MWCNT composites.

The Voltammetric Detection of Cadaverine Using a Diamine Oxidase and Multi-Walled Carbon Nanotube Functionalised Electrochemical Biosensor

Cadaverine is a biomolecule of major healthcare importance in periodontal disease; however, current detection methods remain inefficient. The development of an enzyme biosensor for the detection of cadaverine may provide a cheap, rapid, point-of-care alternative to traditional measurement techniques. This work developed a screen-printed biosensor (SPE) with a diamine oxidase (DAO) and multi-walled carbon nanotube (MWCNT) functionalised electrode which enabled the detection of cadaverine via cyclic voltammetry and differential pulse voltammetry. The MWCNTs were functionalised with DAO using carbodiimide crosslinking with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS), followed by direct covalent conjugation of the enzyme to amide bonds. Cyclic voltammetry results demonstrated a pair of distinct redox peaks for cadaverine with the C-MWCNT/DAO/EDC-NHS/GA SPE and no redox peaks using unmodified SPEs. Differential pulse voltammetry (DPV) was used to isolate the cadaverine oxidation peak and a linear concentration dependence was identified in the range of 3-150 µg/mL. The limit of detection of cadaverine using the C-MWCNT/DAO/EDC-NHS/GA SPE was 0.8 μg/mL, and the biosensor was also found to be effective when tested in artificial saliva which was used as a proof-of-concept model to increase the Technology Readiness Level (TRL) of this device. Thus, the development of a MWCNT based enzymatic biosensor for the voltammetric detection of cadaverine which was also active in the presence of artificial saliva was presented in this study.