than a hundred nanojoules, one to two orders of magnitude lower than Au-, C-, and Si-

based nanomaterials. The main advantage connected to such an approach is that pho­

tothermal stimulation using NW-templated 3D fuzzy graphene (NT-3DFG) is flexible due

to its broadband absorption and does not generate cellular stress.

Another important class of carbon-based and nanostructured material for bioelectronics

is represented by carbon nanotubes (CNTs). Similar to graphene, CNTs display the ability

to reinforce cell adhesion and growth. The large surface area of CNTs promotes neuron

adhesion and the formation of tight junctions between CNTs and neural cell membranes,

facilitating sensitive recording or efficient stimulation [20]. Within the context of cell

stimulation, Hanein and collaborators reported the development of a CdS/CdSe

nanorod-carbon nanotube-based platform for wire-free, light-induced retina stimulation

[61]. The authors exploited the high absorption cross-section of the CdS/CdSe nanorods

to capture light. The energy absorbed is then transferred to the carbon nanotubes via a

charge transfer mechanism, which in turn elicits a response in explanted retinas.

Interestingly, such a device has been shown to work with intensities not far from the one

needed for real-life applications.

4.6 Perspectives

Materials technology has essentially played a paramount role in the evolution and de­

velopment of bioelectronics, while organic electronics has certainly inspired new possi­

bilities in the field. Specifically, we believe that these aspects drive not only important

breakthroughs but also shape the way how we think about bioelectronics. For instance,

the choice of material in-fact governs the following features: i) length scale of interaction

with the bio-target, i.e. from the molecular scale to the organism; ii) the degree of inter­

action, i.e. from passive components (i.e. substrates) to active stimulating/probing ele­

ments; iii) the time-scale of interaction, from milliseconds to seconds and minutes. Given

these considerations, we expect that research on bioelectronic materials will still fuel

future advancements in the field.

For instance, one intriguing approach can be the development of living organic compo­

sites that are intrinsically biocompatible, in which two or more material elements are

combined to provide properties unattainable by single components. In this regard, Bazan

and collaborators have reported on the use of living bioelectronic composites, consisting of

living electroactive bacteria and conjugated polymers [62]. These biocomposites sponta­

neously assemble from solution into an intricate arrangement of cells within a conductive

polymer matrix and show almost an order-of-magnitude lower charge transfer resistance

than the conjugated polymer alone. According to the authors, this supports the idea that the

electroactive bacteria and the conjugated polymers can work synergistically toward an

effective bioelectronic composite. Another interesting example is the one reported by

Tortiglione and collaborators [63]. Here, the authors reported that a fluorescent semi­

conducting thiophene dye promotes, in vivo, the synthesis of fluorescent conductive protein

microfibers via metabolic pathways. By feeding Hydra vulgaris with the dye, they demon­

strated the stable incorporation of the dye into supramolecular protein-dye co-assembled

microfibers. In addition, the appreciable electrical conductivity of such hybrid microfibers

can open the door to new opportunities for augmenting electronic functionalities within

living tissue, which may be exploited to modulate bioelectrical signaling.

Materials for Organic Bioelectronics

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