Page 107 - 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

There is no doubt that growth factors are essential for the In [31], a single and multiple transmitter local drug de‑
control of a multitude of biological processes, such as tis‑ livery system with limited resources is designed at an op‑
sue regeneration; but these factors have a short life; be‑ timal release rate. In this case, the nearest transmitters
cause they are eliminated in the body immediately after to a randomly located tumor are activated to provide the
release. The success of tissue regeneration depends on least effective concentration at the target site. In this sce‑
howlongthetissuehasbeenexposedtothesefactors. The nario, the optimal rate of transmitter nanomachines is de‑
highest rate of regeneration is achieved when the tissue is termined in such a way that the total release rate is min‑
exposed to these factors throughout the whole repair pro‑ imized provided that the least effective concentration is
cess. For this purpose, a set of controlled delivery systems available at the target site. Drug nano‑transmitters have
is considered that is able to release growth factors so that limited resources in terms of energy and reservoir and
the tissue is continuously and for a long time exposed to these limitations should be taken into account when de‑
such factors with an almost constant concentration [11]. signing a drug delivery system. Also, drug molecules may
Coordination between the nanomachines responsible for be expensive, and releasing a large number of them can
this operation can be done by molecular communication; lead to damage to healthy parts of the body.
In this way, the release and control of the place and time A controlled‑release drug delivery system with mobile
of growth factors can be done accurately. In this scenario, drug carrier and absorbing receiver is proposed in [32,
we need rate control methods as well to control the rate 33]. Mobile drug carriers are considered as mobile trans‑
of growth factors. mitters, the targeted disease cells as absorbing receiver
and the channel between the transmitter and receiver as
4. CURRENT RESEARCH ON RELEASING a time‑variant channel. This leads to a time‑dependent
RATE CONTROL IN LOCAL DDS release rate of drug molecules. Numerical results show
that the mobile transmitter controlled‑release drug deliv‑
When the goal of delivering a drug at a target site like a tu‑ ery system outperforms constant‑release rate design.
mor is considered, the drug should be released at an ap‑ In [34], the problem of joint optimization of molecules al‑
propriate rate in such a way that the level of the drug is location and relay location is considered to minimize the
kept within the therapeutic limits during the duration of error probability. Molecule allocation is necessary be‑
treatment [28]. In a sustained drug release system, nano‑ cause of the initeavailability ofmolecule synthesizing en‑
transmitters release drug molecules over a relatively long ergy and limited storage capabilities of the reservoir.
period of time to ensure long‑term treatment of the target Another release rate optimization problem is suggested
area. In this treatment method, the concentration of the in [35]. In this paper, an optimization problem is formu‑
drug should be placed between the two values of LEC and lated to optimize the number of transmitters and transmit
the MTC. power such that the drug concentration at the receiver
If the concentration of the drug at the target site is lower site is kept above LEC, while the interference at other re‑
than the LEC, the drug is not effective enough, and if it is ceivers is maintained below the MTC threshold. The path
higher than the MTC, the drug can have harmful effects on loss of the human circulatory system is also taken into ac‑
healthy parts [29]. Rate control in this way can be used in count.
other applications as well, such as tissue engineering, to Authors in [36] proposed a drug release rate optimization
control growth factors rates or to control the rate of acti‑ based on M/M/c/c queue for the purpose of local drug
vators in activating the immune system. delivery. Drug reception model in this paper is based on
In recent years a great deal of research has been devoted M/M/c/c queue to simulate the interactions between lig‑
to showing the application of molecular communication ands and receptors. The optimal release rate is derived
in order to enhance the ef iciency of a TDD system by con‑ from the LEC.
trolling the release rate of bio‑nanomachines. A compari‑ A drug release synchronization issue in a multiple trans‑
son of state‑of‑the‑art literature on releasing rate control mitter local DDS is addressed in [37]. It is assumed that
for TDD is shown in Table 1. The number of required type a trigger source transmits a signal to the transmitting
of molecules, nanomachine mobility, nanomachines con‑ nanomachines to initiate the drug release. However, the
iguration, receiver type and the transport mechanism are propagation delay causes the nanomachines to release
represented in this table. molecules in a nonsimultaneous manner. The aim of this
To achieve this goal, in [30], a local multi‑nanotransmitter work is to minimize the release‑time error considering
drug delivery system at a constant rate is formulated as the propagation delay.
an image processing problem, and the minimum density In [38], the impact of feedback control is investigated in
required to get enough medicine to all parts of an arbi‑ an Amplitude Shift Keying (ASK)‑based Molecular Com‑
trary tumor of a certain size is obtained. The effect of munication (MC) system, which is of great importance in
distribution of nanomachines on system performance is DDS. In this paper, a one‑dimensional channel with drift
also investigated. In this case, only the nano‑transmitters velocity caused by blood low is considered. The receiver
located at the target site are activated. Therefore, the is assumed to be absorbing with a limit on ligand‑receptor
drug is con ined to the target site and is not propagated binding due to saturation. The input is limited by a tox‑
in healthy parts of the body. icity constraint of injected molecules. It is shown that,

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