interfaces with biological systems. Switchable and flexible bioelectronics based on

graphene nanostructures broadens the natural biochemical interface and mimic the

biochemical reactions along with electron transfer phenomenon under the influence of

external stimuli. Recent research works focused on graphene-based materials unlocked

significant progress in bioelectronics with large-scale, low-cost, high-quality methods for

the identification, detection, and quantification of biomolecules. Biochemical sensors based

on graphene nanostructures have lately made substantial progress in this regard, exhibiting

specific recognition in complicated biological fluids, remarkable temporal and spatial re­

solution, and adaptation to in-vivo platforms. This section explores contemporary research

that incorporates graphene nanostructures in biochemical sensing systems and flexible

bioelectronic interfaces to improve diagnostics and expand clinical applications.

Among the graphene-based nanostructures, the most widely explored materials in the

production of graphene-based electrochemical biosensors are graphene oxide and re­

duced graphene oxide. Graphene oxide has a lot of oxygen-containing groups; thus, it’s

biocompatible and has a lot of active sites for immobilizing enzymes and other com­

pounds. These oxygen-containing groups, however, would reduce their conductivity,

necessitating the use of other conductive particles or polymers in the systems used to

build electrochemical biosensors. Because of its bigger conjugated structures and fewer

oxygen-containing functional groups, reduced graphene oxide has a greater conductivity

than graphene oxide. It has been claimed that reduced graphene oxide can be utilized to

directly change glassy carbon electrodes, which has proved to have more effects than

other carbon nanomaterials like carbon nanotubes.

T. Zhang et al. [35] used the ultrasonication technique to yield a Pd NPs/rGO com­

posite, which can be used as a sensitive tool to detect H2O2 and as a label-free im­

munosensor to identify alpha-fetoprotein selectively. Xiao et al. [36] originally

transformed the graphene paper with electrodeposited MnO2 nanowires and the as-built

electrode was effectively used to detect H2O2 from living cells with an amperometry

response variation of less than 5%. Gan et al. [37] explored the self-assembly of poly(3,4-

ethylenedioxythiophene) on the polydopamine-reduced and sulfonated graphene oxide

template for preparing a water-soluble, conductive, and redox-active nanosheets. This

polydopamine-reduced and sulfonated graphene oxide greatly improve the conductivity

and hydrophilic property of nanosheets. This material exhibited the highest conductivity

of 108 S/m and was found to be stable for long-term storage under 4°C. The presence of

numerous catechol groups makes the nanosheets redox-active and they can be employed

as versatile nanofillers in the development of conductive and sticky hydrogels. Inside the

hydrogel networks, the nanosheets produce a mussel-inspired redox environment, en­

dowing the hydrogel with long-term and reproducible adhesiveness. This biocompatible

hydrogel can be placed in the body for in-vivo biosignal detection. The adhesiveness and

conducting nature of a prepared hydrogel makes it a suitable adhesive electronic skin for

sensing electromyogram, electrocardiogram, and electroencephalogram signals.

The sensitive, speedy, and less expensive biomolecule analysis is critical in clinical

diagnosis and therapy. For this, carbon nanostructures including carbon nanotubes,

carbon nanodots, and carbon nanofibers have been employed. Lu et al. [38] recently re­

ported that graphene and single-stranded DNA assemblies can be employed to detect

biomolecules homogeneously. The electrochemical detection of four free bases viz ade­

nine, thiamine, guanine, and cytosine has been addressed in the discussions of DNA

sensors. With the rapid progress in the field of biosensors, graphene nanostructures have

been easily integrated into ordinary 3D-printing procedures. Marzo et al. [39]. employed

fused deposition modeling to create 3D-printed graphene with polylactic acid (PLA)

Graphene Nanostructures

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