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

Abstract

Carbon nanomaterials have gained significant interest over recent years in the field of electrochemistry, and they may be limited in their use due to issues with their difficulty in dispersion. Enzymes are prime components for detecting biological molecules and enabling electrochemical interactions, but they may also enhance multiwalled carbon nanotube (MWCNT) dispersion. This study evaluated a MWCNT and diamine oxidase enzyme (DAO)-functionalised screen-printed electrode (SPE) to demonstrate improved methods of MWCNT functionalisation and dispersion. MWCNT morphology and dispersion was determined using UV-Vis spectroscopy (UV-Vis) and scanning electron microscopy (SEM). Carboxyl groups were introduced onto the MWCNT surfaces using acid etching. MWCNT functionalisation was carried out using 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC) and N-Hydroxysuccinimide (NHS), followed by DAO conjugation and glutaraldehyde (GA) crosslinking. Modified C-MWNCT/EDC-NHS/DAO/GA was drop cast onto SPEs. Modified and unmodified electrodes after MWCNT functionalisation were characterised using optical profilometry (roughness), water contact angle measurements (wettability), Raman spectroscopy and energy dispersive X-ray spectroscopy (EDX) (vibrational modes and elemental composition, respectively). The results demonstrated that the addition of the DAO improved MWCNT homogenous dispersion and the solution demonstrated enhanced stability which remained over two days. Drop casting of C-MWCNT/EDC-NHS/DAO/GA onto carbon screen-printed electrodes increased the surface roughness and wettability. UV-Vis, SEM, Raman and EDX analysis determined the presence of carboxylated MWCNT variants from their non-carboxylated counterparts. Electrochemical analysis demonstrated an efficient electron transfer rate process and a diffusion-controlled redox process. The modification of such electrodes may be utilised for the development of biosensors which could be utilised to support a range of healthcare related fields.

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

“…With the addition of MWCNTs, an increase in surface roughness, characterized by the presence of irregular peaks and features, was observed (Figure 2b-d). This propensity for CNTs to form aggregates and accumulate in the peaks, increasing the overall surface roughness, has been described in previous studies [49,50]. By comparing the topographic images of p-MWCNT/PDMS and f-MWCNT_N/PDMS (Figures 2b and 2c, respectively), it was observed that a more homogeneous dispersion and distribution of f-MWCNT_N into the PDMS matrix was obtained.…”

Poly(N-vinyl triazole-b-N-vinyl imidazole) Grafted on MWCNTs as Nanofillers to Improve Proton Conducting Membranes

“…Jiang et al used a distillation–precipitation–polymerization approach to grow polymer chains covalently attached on the MWCNT surface and used then as nanofiller with Nafion matrix to create low energy barrier proton transport pathway . A number of interesting articles were published in recent years exploring the effect of surface functionalization of CNTs. − But no report is found to grow block copolymer chains on the CNT surface. In a series of studies, we found that the surface initiated grafting from RAFT polymerization approach allows the in situ formation of the polymer chains on the modified solid surface effectively − and hence we have chosen this technique in the current work, so that we can control the gradual growth of the block copolymer chain at the molecular level, on the surface of the CNT with better precision and check their properties.…”

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

“…In order to carry this out, 1-ethyl-3(3-dimethylaminopropyl)carbodiimide (EDC), a water-soluble zero-length crosslinker, was utilised in the development of the sensing platform [ 38 ]. It is typically used in the coupling of carboxyl groups, which in this study were acid-etched onto the MWCNT surface and used to conjugate EDC to primary amines as previously shown [ 39 ]. EDC undergoes nucleophilic substitution in the presence of strong nucleotides, such as primary amine molecules, and forms an unstable O-acylisourea intermediate [ 40 ].…”

“…Further studies demonstrated a linear range of 50 µM–1.6 mM for cadaverine and similar biogenic amines for a biosensor used on fish samples [ 48 ]. The increased sensitivity of this device may be hypothesised to be due to the modified enzyme/carbon nanotube surface of the working electrode allowing for an increased surface area to enable the enzyme–cadaverine interactions [ 39 ]. This resulted in the ability of the C-MWCNT/DAO/EDC-NHS/GA SPE to detect the electron transfer of the concentrations of cadaverine at lower levels than previously reported ( Table 1 ).…”