2.1 Introduction

Every system known to man can be categorised as either a living system or a non-living system. There are many features and factors which differentiate the categories. Living systems are distinguishable from non-living systems by their ability to maintain stable, ordered states far from thermodynamic equilibrium [1]. For the living systems to maintain the ordered nonequilibrium states, they continuously exchange information/entropy with their environments, grow and reproduce. Examples of living systems include humans, animals, plants and cells. On the other hand, non-living systems, if isolated or placed in a uniform environment, usually cease all motion very quickly such that no macroscopically observable events occur, thereby maintaining permanent equilibrium. Examples include all inanimate objects.

Typically, the living systems are constantly exposed to various degrading factors such as diseases, injuries, threats to life and extreme environmental conditions. Hence, they must find a way to adjust their physiological conditions in order to overcome the challenges. They often achieve this adjustment by their ability to communicate among themselves and with the environment. Communication among living systems is crucial and happens at every level of the systems, from subcellular proteins, through organelles, to tissues and organs and ultimately up to groups of individuals. For instance, communication in humans is needed to carry out daily tasks and coordinate human activities. At the minuscule level, by exchanging information about the ideal constituents of human body fluids and establishing memory banks, certain human cells are able to identify foreign and harmful agents in the body and eliminate them. It is also known that communication among bacteria is needed to slow down or promote protein synthesis during the phases of nutrient starvation and nutrient plenty [2, 3]. Living systems often encounter injuries, and to heal wounds, their bodies employ cellular signalling pathways that involve complex cell-to-cell communication [4]. For cells to acquire and store up energy, communication is required among the pancreatic cells and between the pancreatic cells and the cells that store up energy. The growth and death of an organism also involve complex signalling network among cells [5]. Hence, information exchange among living systems is fundamental to their survival and coexistence in a given environment. A poor communication network implies vulnerability and eventual breakdown of the system, which results in the disruption of the hitherto ordered state of the system. In cellular communication, the breakdown in communication leads to the manifestation of disease symptoms. When effective actions are not taken to normalise the breakdown in communication or where such actions are not known yet, the anomaly in communication may lead to the death of the organism.

In the case of non-living systems, complex multilevel information exchange among the systems does not exist. However, over the years, man has become capable of coupling and re-engineering materials that are hitherto non-living into still non-living systems but with the capability to communicate, giving birth to contemporary communication systems such as electromagnetic wave-based communication systems. Over a century, man has acquired knowledge of the basic principles of communication between non-living systems by means of electromagnetic wave propagation. He has been able to establish impressive communication among artificially engineered systems placed thousands of miles apart. It is envisaged that the extension of the knowledge of communication principles acquired over many years to analyse and/or redesign communication at the cellular level can help address challenges in correcting disorders that lead to ill health in humans.

2.2 Basics of Communication and Information Exchange Between Systems

In general, communication involves the conveyance of information or meaningful messages from one system or group of systems to another using mutually understood functions and rules. Therefore, it may be said that every communication must involve at least two systems or entities, namely, the transmitter and the receiver as shown in Fig. 2.1. The transmitter generates the message in the form of a function that contains a certain amount of information intended for transmission. In some cases, the function may undergo some conditioning (encoding) in order to make it more suitable and robust for its journey to the receiver. The transmitter then transmits/releases/emits the function into the surrounding space/medium, called the communication channel. Subsequently, based on certain physical principles associated with that particular function, it propagates through the channel and may be received by the receiver system. The reception mechanism depends on the particular function that is transmitted. The receiver then employs certain processing to extract the information that is embedded in the received function and acts accordingly. The mutual information or the correlation between the transmitted message and the received message determines the faithfulness of the communication process.

Fig. 2.1
figure 1

Simple generalised block diagram of communication

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2.2.1 Information Conveying Functions

In many forms of communication, the functions that convey information include electromagnetic, magnetic, chemical and mechanical. Under electromagnetic functions, which are synchronised propagating oscillations of electric and magnetic fields, we have sound waves, radio waves and optical waves, each operating at different frequency ranges.

The sound wave is an electromagnetic wave that operates within the lower frequency range of the electromagnetic spectrum and can propagate through air, water and solids. It can be categorised into infrasound waves and ultrasound waves. Infrasound waves are audible to human ears and are between about 20 Hz and 20 kHz [6], while the ultrasound waves are above 20 kHz [7]. Infrasound is the typical information conveying function in human-to-human communication, such as for conversations and speeches, and in animal-to-animal interactions [8]. Ultrasound waves are often used in tissue imaging [9], airborne communication [10] and communication between biosensors [11, 12]. The use of sound waves as a communication function is often constrained by the heterogeneous physical properties of the material medium, the viscosity of the channel, the temperature of the channel (which defines the speed of propagation) and the motion of the channel itself (which induces uneven Doppler shift across the component frequencies of the wave).

Radio waves span the range of frequencies between 3 kHz and 300 GHz. Communications using radio waves as information conveying functions seem to be common to most man-made systems. Hence, it is widely used in communications between systems such as electronic sensors, mobile phones, computers, televisions and satellites. Some animals such as mormyrids and gymnotids communicate (to find food) wholly through complex electromagnetic waves [13]. The use of radio waves as communication functions is often constrained by factors such as attenuation (increases with frequency), delay spread (frequency selectivity), scattering (increases with frequency) and Doppler spread (time selectivity).

Optical waves span the frequency range between 10 THz and 106 THz, covering the spectrum from far infrared through all visible light to near ultraviolet. They are employed as an information conveying function in many man-made and animal communication systems. Man-made optical communication technologies such as lasers [14], fibre optics [15] and infrared [16] are available globally. In respect to living organisms, information conveyance using optical waves is found among many animals such fireflies [17], pyrosomes [18], Noctiluca scintillans [19], Quantula striata [20] and Omphalotus [21]. These organisms use the process of bioluminescence [22] to transmit information intended for organisms of the same species and predators for the purposes of food search, attraction and defence. Information conveyance using optical waves is naturally suited for communication requiring high data rate. However, it suffers from challenges such as absorption and scattering (except when guided as in the case of fibre optics technology), which attenuate the transmitted optical information and eventually bring about multipath fading, resulting in loss of transmitted information observed at the receiver.

Information can be conveyed using magnetic fields, which operate at low frequency [23]. The magnetic field is generated from a coil and spans very short distances (the near field), which are inversely proportional to the frequency of operation. So, the system uses a low-frequency carrier signal to increase communication coverage up to several metres. This limits the data rate capability of the communication. In the medical field, magnetic fields have been employed to interact with tissues, toxins and nanoparticles so as to achieve remote imaging of tissues [24], detoxification [25], and to guide nanoparticles for targeted drug delivery [26].

Information can also be conveyed to a system by means of chemical (or biochemical) signalling, which may be based on the process of classical diffusion. The chemical function is fundamentally defined by the concentration of molecules whose type and/or pattern desirably influence the activities of the receiving system [27]. This is the type of function involved in many communications among natural cells to coordinate their activities [28]. It is also the communication function between some organelles inside the cells.

The use of mechanical energy as an information conveying function entails the physical conveyance of information from the point of generation to that of reception. This mode of communication is akin to how humans deliver messages to a destination by walking or driving the distance. Such function is also used by cells to convey information from one organelle to another by employing molecular motors such as dynein and protein kinesin [29].

The type of function employed for communication depends on the architecture of the communicating systems and the channel through which the communication is intended to take place. The channel is literarily the space between the transmitter and the receiver defined by its material, temporal and spatial properties. It is the properties of this space that primarily determines the type of function that can propagate through it. For instance, let us assume that the mutually understood function between a transmitter and a receiver is the sound wave. If, for instance, the spatial property of the physical channel indicates a large distance between the communicating terminals, it may imply that a sound wave cannot propagate through such distance, but a radio wave can. Implicitly, effective communication between the two systems can be achieved by conditioning the transmitter sound wave to a radio wave by means of lossless ‘transduction’ before transmission. This process is often termed modulation. At the receiving end, the reverse of the modulation, demodulation takes place to extract the equivalent sound wave. This analogy applies to all forms of functions for conveying information.

2.2.2 Generalised Transmitter/Receiver Model

When a system intends to send information to another system, it acts as the transmitter while the latter is the receiver. The transmitter generates the intended message made up of symbols derived from a set. The information (self-information) in the message is defined by the entropy of the transmitter. The method of generating and transmitting/releasing each of the information conveying functions named above differs from one to another. Hence, different types of functions are generated by different types of transmission mechanisms. Irrespective of the type of transmitter and the transmitted function, a good model of a transmitting system is important in its characterisation and use in a communication scenario. We can generally represent the model of a nanotransmitter by the expression

$$ {\text{Trigger}}{\xrightarrow{{T\_{\text{Model}}}}}{\text{Information signal}} $$
(2.1)

Here, the trigger signal, which may be electromagnetic, electrical, magnetic, optic, chemical or mechanical, initiates the transmission process in the transmitter. This results in the emission of the information signals, which again may be any of the functions named above. The model challenge is that for a given trigger signal and desired information signal, one needs to define the process model T_Model that is truly representational of the nanotransmitter information generation, function encoding and signal release/emit mechanisms.

Characteristically, in information theoretic parlance, the transmitted information is termed self-information and by itself does not usually convey any meaning. Rather, it conveys meaning only when there is a receiver that interprets the specific features of the transmitted function to obtain the sent information, which will usually result in state change at the receiver. Implicitly, what is information to one receiving system may not be information to another. Hence, every transmitting system should have a complementary receiving system. A good model for a receiver in general can be expressed as

$$ {\text{Received signal}}{\xrightarrow{{R\_{\text{Model}}}}}{\text{Response}} $$
(2.2)

The model challenge is as follows. Given a received signal, it is required that the receiver model process R_Model be defined in a manner that is truly representational of the reception and signal processing mechanism of the receiving system under consideration.

2.2.3 Communication Performance Measures

There are some performance metrics which have to be taken into consideration while designing or analysing a communication system, whether it is between living systems or non-living systems. Some of these metrics are described below. The metrics discussed here are transmission rate, end-to-end delay, probability of error, throughput, energy efficiency and consumption and environmental compatibility.

2.2.3.1 Transmission Rate

The transmission rate of a system reflects how quickly transmitted information is processed by a communication system. This depends on the rate at which information is released into the channel, the channel bandwidth, the propagation time and the time is taken to sample the information at the receiver.

2.2.3.2 End-to-End Delay

The end-to-end delay metric defines the unit time it takes to transmit a message, and for the transmitted message to propagate through the channel and be processed by the receiver. It is dependent on the time the transmitter released the message after the release trigger, the type of communication function in use, the propagation characteristics (channel properties as well as those of the intermediate nodes) and the receiver processing time.

2.2.3.3 Probability of Error

To explain the concept of probability of error as a communication metric, let X be the transmitted information, and Y the expected output. We want to quantify the likelihood that the discrepancy between Y and any other observed output is within a certain range. We do this by defining the error probability metric. In essence, error probability is the probability of a given receiving system making a wrong decision, in which case an output other than Y is produced. The discrepancy in output results from the uncertainty in transmitting X through the communication channel that is prone to noise and other perturbations.

2.2.3.4 Throughput

The throughput metric quantifies the amount of information processed by the receiving system in a given amount of time. Just like the end-to-end delay metric, this metric is dependent on the type of communication function in use; the propagation characteristics (channel properties as well as those of the intermediate nodes); and the receiver processing capability.

2.2.3.5 Energy Efficiency and Consumption

This metric quantifies the efficiency in energy usage for information exchange between two systems. Typically, energy is required for the generation and transmission of information, the conveyance of the information through the channel to the receiver and the processing of the information at the receiver. The energy required for these operations will most often come from an external power source or be latent in the system. Therefore, the lesser the energy expended for molecule synthesis, emission, propagation, reception and processing, the more efficient the system is.

2.2.3.6 Environmental Compatibility

The environmental compatibility metric reflects the impact of the communication between systems on the environment, which is inclusive of the effective working of other systems in the environment. The effects that are often considered include the impact on the climatic conditions, the biological/chemical/mechanical conditions and noise emission. For instance, in using an electromagnetic function for communication, the interaction/interference of communication electronic and electrical equipment with its electromagnetic environment is always considered. Hence, electromagnetic communication devices are required to emit electromagnetic energy that is lower than a certain value to ensure that interference with other communication systems is reduced. Issues related to the unhealthy absorption of propagating electromagnetic waves by the human body, which may influence biological activities in living organisms, are defined by the quantity and specific absorption rate [30]. In the case of communication using chemical functions, the quantity, termed supersystem degradation [31], defined as the impact of the biochemical/chemical communication network upon the host organism with regard to its normal operation, should be considered. This can also be related to how energy harvested from the supersystem by the communication systems affects the primary functions of the host organism.

2.3 Communication Between Living Systems

Communication among living systems happens at every level of the system, from subcellular level, through the tissue and organ levels, and up to the level of the organism. Effective communication among living systems at their various levels of existence is fundamental to their harmonious organisation, which ensures that they collaboratively meet the intended goals of the host environment/organism.

2.3.1 Communication at Organism Level

Communication between organisms such as humans, animals and plants takes place by means of one or more of the information conveying functions discussed earlier. The organisms are naturally equipped with transmit/receive facilities such as an auditory system, olfactory system, visual system, chemoreceptor system and mechanoreceptor system. Hence, they can communicate with each other and their environment using functions such as sound waves, optical waves, chemical signalling and mechanical energy.

2.3.1.1 Communication Between Animals

Animals, including humans, communicate among themselves to spread knowledge and establish/improve relationships. The result is a more cohesive organisation, greater productivity and strong working relationships at all levels of the organism. Unaided communication among humans is often done with a syntactically organised system of signals, such as voice sounds, intonations or pitch, gestures or written symbols that communicate thoughts or feelings. Animals also communicate with one another (especially those of the same species) to search for food, mates and avoid dangers/predators, by making special sounds, sending out optical signals, emitting/receiving chemical signals (pheromone communication) [32, 33] and tactile communication [34]. For examples, monkeys use calls to warn one another of danger [35]. Birds such as the peacocks can make imposing feather displays to communicate a territorial warning to other competing peacocks [36]. Many different types of animals mark their territories with their scent (chemical signalling) as a clear message to others to stay away.

2.3.1.2 Communication Between Plants

Plants also communicate with each other and their environment. These living systems are usually exposed to various stress factors such as disease, injury, herbivory and extreme heat/cold [37]; hence, they must find a way to adjust their physiological state either in response to or in preparation for such threats to ensure their well-being and survival [38]. To make this adjustment, plants have developed a communication system to transmit information based on volatile organic compounds [37]. As in all organisms, the evolution, development and growth of plants depend on the success of these communication processes [39]. And just like in the case of animals, communication between plants is multilevel: among the cells of a plant; between plants and microorganisms, fungi and insects; between different plant species; and between members of the same plant species. For more in-depth information on plant communication, the reader is referred to [37, 39, 40–41].

2.3.2 Communication at Cell Level

Aside from communication between organisms, communication also takes place inside the organisms at the basic level of cells. All living organisms are composed of cells, which are the basic building blocks of all living systems. The cells in an organism do not live in isolation but interact among themselves. Their survival depends on receiving and processing information from each other and the extracellular environment. The information may reflect the availability of nutrients in the microenvironment, changes in environmental conditions, the need to reproduce/grow or the need to undergo apoptosis. On the basic cellular level, the information exchange is essentially by means of chemical signalling and electric impulses.

2.3.2.1 Communication at Cell Level in Multicellular Organisms

In multicellular organisms such as animals and plants, there are various kinds of chemical signalling methods with which cells communicate with one another, which is dependent on their proximity to each other. This signalling is grouped into four types, namely, autocrine, juxtracrine, paracrine and endocrine signalling. Autocrine signalling occurs when a cell responds to its own biochemical signalling molecules that it produced. Some examples of this type of signalling include lipophilic and prostaglandins binding to membrane receptors. Juxtracrine signalling occurs between adjacent cells that are in contact; hence, this type of signalling is often referred to as a contact-dependent signalling. It plays a very significant role in controlling cell fate and embryonic development [42]. Paracrine signalling involves signalling between cells that are within the same vicinity. An example of this is the histamines hormone, which is released as a local response to stress and injury [43]. Endocrine signalling is the most common type of cell signalling and involves sending a signal throughout the whole body by secreting hormones into the bloodstream or sap of the organism. Examples include adrenal signalling, thyroid signalling and pancreatic signalling [44, 45].

On the other hand, nerve cells called neurons communicate by means of a combination of electrical and chemical signals. Within the neuron, electrical signals driven by the movement of charged molecules across the cell membrane allow rapid propagation of electric pulses from one end of the cell to the other. Communication between neurons occurs at tiny gaps called synapses, where specialised parts of the two cells (i.e. the presynaptic and postsynaptic neurons) come within nanometres of one another to allow for chemical transmission [46].

2.3.2.2 Communication at Cell Level in Unicellular Organisms

In single-cell primitive organisms such as bacteria, viruses and fungi, communication between organisms has been known to occur by means of chemical signalling. Bacteria can communicate by quorum signalling/sensing, especially when they are in high density [47]. This form of collaborative communication provides the group of bacteria a way to adapt to the environment. It has also been reported that there exists some form of communication between viruses [48]. Communication between fungi and plant/bacteria has also been reported [49, 50].

2.4 Communication Between Non-living Systems

While non-living systems cannot communicate among themselves when placed in a uniform environment, they can be engineered to do so as is evident from communication between man-made electronic devices and machines. From the invention of the electric battery by Alessandro Volta in 1799 through the development of the electric telegraph, the Marconi experiment on wireless telegraphy, the invention of electric telephone in the nineteenth century, and the subsequent invention of the television and man-made satellites systems, communication between man-made systems has impacted tremendously on the human race. These feats have been taken further to the development of high-end and smart electronic communication devices, the most common being phones, computers, radio, television, sensors and the Internet. With these communication devices, we are able to communicate effectively and nearly instantaneously with people at different locations and receive information about innumerable developments and proceedings of importance across the globe.

2.4.1 Medical Applications of Man-Made Communication Systems

In recent times, advances in the design and development of electronic communication systems and devices have enabled ubiquitous healthcare systems, which promises an increase in efficiency, accuracy, affordability and availability of medical treatment. This is necessitated by the need to address many challenges facing the healthcare industry. Some of these challenges include societal changes such as an increase in the population that desire access to healthcare service, the size of the ageing population, the number of chronic diseases, the number of people suffering from them and the uneven distribution of healthcare personnel. Moreover, with the appearance of new diseases that are characterised by complicated strains, early detection and novel therapeutic methods are always urgently required to avoid endemic situations that may significantly threaten global population.

The contemporary application and deployment of electronic communication systems to the healthcare sector are usually for the measurement of biosignals [51]. These biosignals are usually associated with various pathological conditions such as blood pressure, sugar level, pulse rate, body temperature variation, electrical activity of the brain, electrical activity of the muscles and electrical activity of the heart. The medical personnel then employ the values of these measurements to make better judgment on the patient’s condition and administer the best therapeutic actions. The advent of wearable technologies, shown in Fig. 2.2, that can measure these biosignals has revolutionised the healthcare and fitness sector [52]. In wearable technology, sensors are placed at different areas of the body to collect data (in this case, biosignal readings). With the advancement of low-power integrated circuit (IC) and wireless communication technologies, concepts such as the wireless body area network (WBAN) are becoming an emerging research area [53]. The WBAN or body sensor network (BSN) is a wireless network that enables health monitoring anywhere and anytime [54]. Also, with the advances in the Internet of things (IoT), concepts like the Internet of humans (IoH) that integrate the BSN to the IoT have emerged, as illustrated in Fig. 2.3. The IoH [55] paradigm is a cutting-edge enabler that can be used for e-health applications, such as computer-assisted rehabilitation for the aged and handicapped and early detection of medical issues.

Fig. 2.2
figure 2

Illustration of wearable technology applied to a health care and b sports/fitness

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Fig. 2.3
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On-body communication network of biosignal sensors

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2.4.1.1 On-Body Sensor Networks

When sensors are places on the human body for the purpose of data acquisition, the BSN is termed an on-body sensor network. The data generated by each sensor is conveyed to another sensor or to a nearby central processing system or across to a remote processing system for further processing, as depicted in Fig. 2.3. The information conveying function is usually the electromagnetic wave operating at a defined frequency. Therefore, the knowledge of the effect of the wave propagation channel around the body on communication performance is crucial to the design, placement and operation of the on-body sensor network.

2.4.1.2 Intra-body Sensor Networks

In some scenarios, the positioning of the sensors further into the body provides more accurate reading of some biosignals. The benefits of intra-body sensor technology over on-body sensor technology include lower power demand and less susceptibility to electromagnetic interference as well as insecurity issues [56]. Intra-body communications involve the use of non-RF wireless data communication techniques, which employ the human body itself as transmission medium for electric signals. In this case, the sensors are implanted into the body—for instance, under the skin—which implies that they communicate through the body tissues, as shown in Fig. 2. 4. A table showing some comparisons between the on-body and intra-body sensor networks for medical application is given in Table 2.1.

Fig. 2.4
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Intra-body communication network of biosignal sensors

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Table 2.1 Comparison of on-body and intra-body communication networks
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2.5 Communication Between Living and Non-living Systems: Advanced Targeted Nanomedical Solution Basis

Communication among humans is integral to their ability to establish relationships and spread knowledge to enhance cohesive organisation, productivity and survival at all levels of human existence. Breakdown in communication brings about ineffective interactions, which results in uncertainty, misunderstanding, confusion, argument/conflict and ultimately poor productivity and sometimes deaths [57]. It is the need to ensure efficient communication among humans at any time, from anywhere or any source, and in any condition that has necessitated the design and development of many man-made communication technologies and devices. Such devices and technologies include phones, computers, telepresence, satellites and the Internet. We have discussed the potentials and benefits of communication between living systems, and between non-living systems. We shall now focus on the possibility of communication between living and non-living systems, which forms the basis of the ATN.

2.5.1 Diseases as Manifestation of Breakdown in Communication Among Cells

Just like a social communication network is crucial to the survival of humans, the same applies to the organs, tissues, cells and molecules inside the human body. Naturally, for the human body to function well and achieve its goal of survival, all the organs, cells and molecules in the body have to work collaboratively and harmoniously. Such collaboration requires the sending and receiving of information to effect ‘social control’ [58]. A breakdown in communication at the various points in the cell network shatters this harmony resulting in diseases. In man-made communications, breakdown in communication is caused by faulty devices and connections. The repair or replacement of the faulty devices/links normalises connectivity. The same logic applies to breakdown in communications among cells in human body. Indeed, issues relating to diseases and cell defects can be narrowed down to the breakdown in communication among a group of cells in the body. For instance, breakdown in cell-to-cell communications has been implicated in many diseases such as Alzheimer’s [59], diabetes [60], Parkinson’s [61], cancer [62], Huntington’s [63], etc. The repair or replacement of defective cells and cellular pathways normalises communication, and that is the primary goal of medicine.

In medical science and practice, different modalities are employed to achieve this normalisation. One modality is the introduction of specific drug particles to act as extracellular chemical signals, which inform the defective cells to directly carry out desired chemical, physical and biological modifications to achieve therapeutic results, thereby restoring normal communications. The source that introduces the drug particles represents a transmitter and the targeted defective cells, the receiver. In this case, where the drug-introducing source is a man-made machine-like injection machine, this can be regarded as a communication between living and non-living systems.

In another modality, if isolation of the defective cells is the best option to achieve harmonious communications among all other cells in the body, the cells can physically be removed by means of surgery. But if the isolation of the defective cells will have a significant effect on the harmonious working of all other cells in the body, then the modality will further require that the removed defective cells are replaced with artificially engineered replicas, assuming that the technology for engineering the replica exists. Recent developments in tissues engineering, particularly 3D printing [64], have radically changed our ability to integrate inanimate parts into humans. We are already growing new tissues on artificial scaffolding for transplantation, and prosthetics that can be controlled by the minds of patients with paralysis caused by illness or injury have been demonstrated.

To be able to correct anomalies in cellular communications, one has to first obtain a detailed understanding of the architecture and working of the cells of interest in both healthy and unhealthy conditions. Hence, preceding the design and implementations of any modality for disease treatment, study of the cells and cells signalling is crucial. Such study may also involve communication between certain man-made systems and natural cells and tissues. For instance, the use of sensors to read biosignal information from cells can be regarded as communication between cells and man-made systems.

2.5.2 Nanomedical Solution for Normalising Breakdown in Communication Among Cells

In many cases, the complete knowledge of how to address a given breakdown in communication using the currently existing macro technologies is not available. Examples include the treatment of Alzheimer’s, cancer, HIV and many cardiovascular diseases. In some cases, the existing methods of therapy may have side effects that are quite challenging. An example is in the treatment of cancer using chemotherapy, where the issue of toxicity is evident from side effects such as alopecia, compromised immunity, fatigue, haemophilia, loss of appetite, painful urination, nausea and vomiting, nail toxicity and anaemia [65]. Hence, new ideas and concepts are currently being explored to address the challenges posed by various difficult medical conditions.

In the course of normalising breakdown in communication among cells, contemporary medicine often employs non-living, man-made systems to detect anomalies, screen for defects, diagnose disease, treat it and monitor its progress. For instance, man-made systems such as biosignal sensors, magnetic resonance imagers, computed tomography scanners and syringes communicate with living systems such as cells and tissues to detect and treat diseases. These systems use one or more of the information conveying functions discussed earlier to receive information about the cells’ condition or convey therapeutic information to the cells.

In line with the above assertion, there has been a recent paradigm shift from the vastly explored contemporary medicine (based on macro-science and engineering) to nanomedicine (based on nano/micro-science and engineering). The idea of nanomedicine stems from the idea that since diseases manifest from miniscule activities in the cells of living organisms, it is insightful and seemingly effective to tackle health challenges at the cell level. Nanomedicine exploits the unique properties of nanomaterials and the tools of nanotechnology to combat health challenges at the cellular level. It has found applications in diverse medical specialties such as oncology, immunology, osteopathy and urology [66]. For instance, in contemporary medicine, drug molecules are injected into the bloodstream with the expectation that a small but significant percentage of the drug gets to the defective cells and initiates the required therapy. In the nanomedical approach, a nanosystem carrying the required amount of drug that is capable of producing the desired therapeutic result is injected into the blood stream, from where it smartly conveys the drug molecules to the defective cells. This nanomedical approach is termed targeted drug delivery technology [67,68,69]. Aside from delivering drug molecules, genes (for gene therapy) [70] can also be delivered to the targeted tissue or cell using engineered nanomedical nanosystems. Hence, in the context of living-to-non-living systems communication, nanomedicine is concerned with the design of nanoscale systems that can convey or receive information from cells.

In cases where the breakdown in cellular network communication is due to the loss or malfunctioning of tissues, the affected tissue can be replaced by man-made biological substitutes to restore, maintain or improve network performance. The substitute man-made biological nanosystem can be fabricated by means of nanomedical tissue engineering principles [71], which enables the design and fabrication of biocompatible scaffolds at the nanoscale. Nanomedical tissue engineering can also enable the creation of controllable and predictable implantable tissues [66].

In clear terms, the objectives of nanomedicine are as follows: (i) to explore the communication engineering, biology, chemistry, physics and mathematics of human (animal) systems and diseases at the nanoscale; (ii) to use the knowledge obtained to design nano- to macro-size systems that can communicate directly with each other and with the disease cells to detect, screen, correct and monitor anomalies in the cells; thereby addressing health challenges at the root. Communications among synthesised nanosystems and other man-made devices (such as the on-body sensors, which are non-living systems), and between the non-living nanosystems and natural cells (living systems) define the ATN solution.