Page 106 - 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

depends on a network parameter (e.g. how long the error adjust the rate of release of drug molecules based on dif‑
hasn’t occurred), in which case remembering the history ferent conditions, such as the spatial distribution of target
is necessary. cells and bio‑nanomachines.
In the past 30 years, the issue of congestion control TDD enables local drug delivery, which is not possible
in packet networks has been considered by many re‑ with systemic drug delivery. By placing the drug deliv‑
searchers. However, little attention has been paid to this ery system near the tumor site, the drug is released only
issue in molecular networks [21]. In [21], congestion at the site of the disease and the drug level is low in other
is de ined as the inability of the receiver to accept all sensitive areas of the body [23]. On the other hand, other
molecules in the receiver space and the congestion con‑ drug delivery systems that are injected intravenously may
trol problem has been investigated in a drug delivery sce‑ be rapidly excreted by cleansing organs such as the kid‑
nario. This limitation occurs for two reasons: limited neys, which can lead to healthy tissue being exposed to
number of receptors at the receiver surface and signi i‑ toxic levels of the drug. To address these problems, local
cant traf icking time. Traf icking time is de ined as the methods such as intra‑tumor injection and drug release in
time required for a ligand to bind a receptor plus the time the vicinity of unhealthy tissue have been studied, includ‑
needed to internalize the complex. In [21], theoretical ing [24, 25] to treat skin cancer and [26] for the treatment
analysis of congestion reasons in a diffusion‑based molec‑ of bladder cancer.
ular communication is carried out and a receiving model
including a set of queue systems is presented. 3.2 Immune system

3. THERAPEUTIC APPLICATIONS OF RATE Rate control can also be used to activate the immune sys‑
CONTROL tem. The immune system is made up of different types
of cells that are able to perform speci ic functions against
3.1 Targeted drug delivery pathogens and threats. Each type of immune cell special‑
izes in ighting a speci ic threat and is stimulated by a se‑
In drug delivery applications, if the transmitter sends quence of message molecules that are released by the im‑
molecules at a higher rate than what the receiver can pro‑ mune cells responsible for detecting pathogens. The im‑
cess, these molecules will disperse in the environment mune system is stimulated to kill bacteria or viruses, heal
and can lead to adverse side effects in other areas. Also, diseased cells, and eradicate cancerous tumors. Molecu‑
since drug molecules are expensive in some cases, it is im‑ lar communication and arti icial nanomachines can stim‑
portant to prevent the loss of these molecules. ulate the immune system and be used to intensify the re‑
Molecular communication enables new methods of drug sponse to a variety of threats [11]. In some cases, it is also
delivery by creating cooperation between nanomachines. necessary to prevent the immune system from respond‑
For example, a large number of bio‑nanomachines can ing by releasing molecules that can reduce the activity of
be injected into a patient’s body to perform massively the immune system. Synthetic antagonists can also be
parallel searches of the diseased site. When the bio‑ used to reduce the immune response. Therefore, similar
nanomachine detects the signal molecule secreted by the to TDD, there is a need to monitor and control the rate of
disease site, it will amplify the signal molecule, thereby activators or antagonists.
increasing the concentration of the signal molecule in the
environment, causing more bio‑nanomachines to reach 3.3 Tissue engineering
the disease site. A group of bio‑nanomachines at the tar‑
get site can also communicate via quorum sensing to es‑ Another application of molecular communications where
timate the number of bio‑nanomachines in the environ‑ the rate control is required is tissue engineering [14, 11,
ment and increase (or decrease) the rate of drug release if 27]. Tissue engineering can lead to organ construction
the number of nanomachines is small (or large) to achieve and help patients with tissue or organ failure. By plac‑
the continuous release of drug molecules into the envi‑ ing nanomachines in engineered organs, intelligent or‑
ronment. A group of bio‑nanomachines with different gans can be produced that can diagnose diseases.
functions can also be used to detect different environmen‑ Tissue engineering has a role in regenerative medicine.
tal conditions, communicate to aggregate sensed condi‑ The goal of regenerative medicine is the replacement of
tions, and perform complex calculations such as logic cal‑ damaged tissues and organs by using transplanted cells
culations to determine whether drug molecules are re‑ at the injured site. Cellular signaling plays an essential
leased [14]. Another example of collaboration between role in development of the tissue. This signaling is often
nanomachines using molecular communication is encap‑ based on diffusion and direct cell‑to‑cell interactions. Un‑
sulated drug transmitters that help to increase the life‑ der such conditions, molecules such as peptides and pro‑
time of a drug delivery system and solve the problem of teins regulate the absorption of soluble growth factors,
limited reservoir capacity, as described in [22]. These and the adhesion, migration, proliferation and differen‑
methods are designed to maximize the therapeutic effects tiation of a large number of cell types. All these factors
of drug molecules; therefore, a group of nanomachines effectively control the response of the cells and ultimately
must communicate with each other at the target site to the formation of the new tissues.

94 © International Telecommunication Union, 2021