Heterogeneous Electron Transfer and Oxygen Reduction Reaction at Nanostructured Iron(II) Phthalocyanine and Its MWCNTs Nanocomposites

Bovine Serum Albumin-Dependent Charge-Transfer Kinetics Controls the Electrochemical Immunosensitive Detection: Vibrio cholerae as a Model Bioanalyte

This work investigates how bovine serum albumin (BSA), a commonly used protein in the fabrication of electrochemical immunosensors, can impact on the sensitivity of detection when integrated with antibody (Ab) pre-encapsulated with (i) insulating polyacrylonitrile (PAN) fibre (i.e., GCE-PAN-Ab-BSA immunosensor) or (ii) conducting PAN-grafted iron (II) phthalocyanine (FePc) (i.e., GCE-PAN@FePc-Ab-BSA immunosensor), using Vibrio cholerae toxin as a case study bioanalyte. Both immunosensors show different charge-transfer kinetics that strongly impact on their immunosensitive detection. From the electrochemical data, GCE-PAN-Ab-BSA is more insulating with the presence of BSA, while the GCE-PAN@FePc-Ab-BSA is more conducting with BSA. The CV of the GCE-PAN-Ab-BSA is dominated by radial diffusion process, while that of the GCE-PAN@FePc-Ab-BSA is planar diffusion process. The behaviour of GCE-PAN@FePc-Ab-BSA has been associated with the facile coordination of BSA and FePc that permits co-operative charge-transport of the redox probe, while that of the GCE-PAN-Ab-BSA is related to the interaction-induced PAN-BSA insulating state that suppresses charge-transport. As a consequence of these different interaction processes, GCE-PAN-Ab-BSA immunosensor provides higher electroanalytical performance for the detection of Vibrio cholerae toxin (with sensitivity of 16.12 Ω/log [VCT, g/mL] and limit of detection (LoD) of 3.20 × 10-13 g/mL compared to those of the GCE-PAN@FePc-Ab-BSA (4.16 Ω/log (VCT, g mL-1) and 2.00 × 10-12 g/mL). The study confirms the need for a thorough understanding of the physico-chemistries of the electrode platforms for the construction of immunosensors. Although this work is on immunosensors for cholera infection, it may well apply to other immunosensors.

GRAPHICAL ABSTRACT

Heat treated carbon supported iron(ii)phthalocyanine oxygen reduction catalysts: elucidation of the structure–activity relationship using X-ray absorption spectroscopy

Correlation between atomic structure and oxygen reduction activity by X-ray absorption spectroscopy.

2,3-Dichloro-5,6-dicyano-1,4-benzoquinone-catalyzed aerobic oxidation reactions via multistep electron transfers with iron(ii) phthalocyanine as an electron-transfer mediator

A new biomimetic catalytic oxidation system was developed for oxidative deprotection of PMB ethers, alcohol oxidation, aromatization and α,β-unsaturated aldehyde formation.

Oxygen reduction reaction at MWCNT-modified nanoscale iron(ii) tetrasulfophthalocyanine: remarkable performance over platinum and tolerance toward methanol in alkaline medium

A novel nanoscale iron(ii) tetrasulfophthalocyanine complex catalyzes oxygen reduction reaction in alkaline medium more efficiently than the expensive state-of-the-art Pt catalyst.

Bio-functionalized Pt nanoparticles based electrochemical impedance immunosensor for human cardiac myoglobin

We report the covalent immobilization of three-dimensional carboxyl-functionalized Pt(MPA) nanoparticles with myoglobin protein antibody by carbodiimide coupling reaction deposited onto an indium-tin-oxide-coated glass plate for the construction of a bioelectrode.

Microstructural and electrochemical impedance characterization of bio-functionalized ultrafine ZnS nanocrystals-reduced graphene oxide hybrid for immunosensor applications

We report a mercaptopropionic acid capped ZnS nanocrystals decorated reduced graphene oxide (RGO) hybrid film on a silane modified indium-tin-oxide glass plate, as a bioelectrode for the quantitative detection of human cardiac myoglobin (Ag-cMb). The ZnS nanocrystals were anchored over electrochemically reduced GO sheets through a cross linker, 1-pyrenemethylamine hydrochloride, by carbodiimide reaction and have been characterized by scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy. The transmission electron microscopic characterization of the ZnS-RGO hybrid shows the uniform distribution of ultra-fine nanoparticles of ZnS in nano-sheets of GO throughout the material. The protein antibody, Ab-cMb, was covalently linked to ZnS-RGO nanocomposite hybrid for the fabrication of the bioelectrode. A detailed electrochemical immunosensing study has been carried out on the bioelectrode towards the detection of target Ag-cMb. The optimal fitted equivalent circuit model that matches the impedance response has been studied to delineate the biocompatibility, sensitivity and selectivity of the bioelectrode. The bioelectrode exhibited a linear electrochemical impedance response to Ag-cMb in a range of 10 ng to 1 μg mL(-1) in PBS (pH 7.4) with a sensitivity of 177.56 Ω cm(2) per decade. The combined synergistic effects of the high surface-to-volume ratio of ZnS(MPA) nanocrystals and conducting RGO has provided a dominant charge transfer characteristic (R(et)) at the lower frequency region of <10 Hz showing a good biocompatibility and enhanced impedance sensitivity towards target Ag-cMb. The impedance response sensitivity of the ZnS-RGO hybrid bioelectrode towards Ag-cMb has been found to be about 2.5 fold higher than that of a bare RGO modified bioelectrode.

Nanostructured metallophthalocyanine complexes: synthesis and electrocatalysis

In this review, we have attempted to summarize the synthesis and catalytic applications of the nanophthalocyanine complexes. In cases where possible, we have compared the catalytic activity of the nanophthalocyanines to the bulk material. Catalytic detection of dopamine, epinephrine, glucose and some pollutants using nanostructured metallophthalocyanine have been covered.