Page 24 - ITU Journal Future and evolving technologies Volume 2 (2021), Issue 3 – Internet of Bio-Nano Things for health applications

ITU Journal on Future and Evolving Technologies, Volume 2 (2021), Issue 3

transduces information‑encoded electronic input signals architecture that can enable the in vivo optical
into biologically‑recognized signals in the form of hy‑ stimulation of brain cells to control neuronal
drogen peroxide through an oxygen reduction reaction. communications based on external EM signals. Their
These signals are recognized by bacterial cells that are at‑ device architecture includes a wireless antenna unit that
tached to the biohybrid electrode, and then biologically connects the implanted device to external networks, an
propagated across a microbial population with quorum ultrasonic energy harvester, and a micro light emitting
sensing molecules. The overall electronic‑biology link is diodes ( - LED) for optical stimulation.
bidirectional such that a microbial subpopulation in the
Fluorescent molecules, such as luorescent proteins,
BioLAN generates speci ic molecules that can be detected quantum dots, and organic dyes, can also be used to rea-
by the electrode via an electrochemical oxidation reac‑ lize a wavelength‑selective optical interface. In [113],
tion. organic dye molecules have been used as
Wearable and epidermal tattoo biosensors and transder‑ nanotransceiver antennas for FRET‑based molecular
mal drug‑delivery systems, which have attracted a sig‑ nanonetworks. They act as single molecular optical
ni icant research interest for various healthcare applica‑ interfaces that receive optical control signals from an
tions, can also be targeted for an macro‑nano interface external source and non‑radiatively transmit them
that can connect intrabody IoBNT to the external commu‑ into a FRET‑based nanonetwork. They enable an
nication networks, with the integration of communication nano‑to‑macro interface as well, since the excited
antennas, such as radio‑frequency‑identi ication (RFID)‑ luorescent molecules return to their ground state by
tag‑antennas [117, 118, 119, 120]. The challenges lie in releasing a photon at a ic wave‑length that can
the further miniaturization of these devices as well as be detected by an external photodetector. Similarly, in
their continuous operation, since biosensors exposed to [75, 126], it is suggested that a nano‑to‑ macro interface
can be realized with engineered bacteria receivers
physiological luids suffer contamination, and drug de‑
expressing pH‑sensitive green luorescent proteins
livery systems require periodic replenishment of their
(GFPs) that change excitation/emission characte-ristics
reservoir.
depending on the pH of the environment. Biolumi‑
3.2.2 Optical Interfaces nescent molecules that are excited upon reaction with a
target molecule can also be used for the direct conversion
of MC signals to optical signals to enable a nano‑to‑macro
Light represents an alternative modality to interface the
interface, as proposed in [127, 108].
intrabody IoBNT with external networks. In the case that
MC is utilized in IoBNT, such an optical interface can be
realized with the help of light‑sensitive proteins and bio‑ 3.2.3 Other Interfacing Methods
luminescent/ luorescent proteins.
Optical control of excitable cells, e.g., neurons and mus‑ Depending on the communication modality utilized in in‑
cle cells, can be achieved through a well‑known technique trabody IoBNT, there are some other nano‑macro inter‑
called optogenetics [121]. The method relies on the ge‑ facing methods proposed in the literature. For example, in
netic ication of natural cells for enabling them to [128], the authors consider the use of magnetic nanopar‑
express light‑sensitive transmembrane ion channel pro‑ ticles (MNs) as information carriers in a MC system. They
teins, e.g., channelrhodopsin. The resulting light‑sensitive propose a wearable magnetic nanoparticle detector in the
ion channels open or close depending on the wavelength form of a ring to connect the intrabody MC to an RF‑based
of the incident photons. The technique enables speci icity backhaul. In a follow‑up study [129], they also demon‑
at the level of single cells in contrast to conventional elec‑ strate the control of MN‑based MC signals in micro luidic
trical interfacing techniques, which generally suffer from channels with external magnetic ields, that could poten‑
low level of icity. It is shown in [122, 123] that tially evolve to a bidirectional interface for IoBNT.
bacteria can also be engineered to express speci ic light‑ In light of the emerging reports on the EM‑based wireless
sensitive proteins, e.g., bacteriorhodopsin, that pump out control of cellular functions via speci ic proteins that are
protons under illumination, and thus, change the pH of its responsive to electromagnetic ields [130], a wireless link
close environment. is proposed to connect THz‑band EM and MC modalities,
In [56], the authors propose that optical control of engi‑ that can translate into an EM‑based nano‑macro interface
neered cells with light‑sensitive ion channels can be ex‑ [131]. The authors in [132], develop an information the‑
ploited to enable an optical macro‑to‑nanoscale interface oretical model for the mechanotransduction communica‑
that can modulate the molecular release of MC transmit‑ tion channel between an implantable THz nanoantenna
ters. The authors in [124], experimentally demonstrate acting as the transmitter and a biological protein as the re‑
that synthetic bacteria expressing bacteriorhodopsin can ceiver undergoing a conformational change upon stimula‑
convert external optical signals to chemical signals in the tion by the THz waves. Although THz‑waves are theore-
form of proton concentration at 1 bit/min conversion tically shown to reliably control the conformational
rate. They use the same technique to enable an expe‑ states of proteins, it remains as a challenge to investigate
rimental MC testbed in [75]. Similarly, in [125], the the use of the same modality in sensing the protein
authors propose an implantable bio‑cyber interface states to enable bidirectional wireless interface.

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