Biological nanomachines are nano-sized tools used for the monitoring, diagnostic, and treatment of disease at the molecular scale. Biological nanomachines adopt the structure and communication principles of natural biological cells. From a communication engineering perspective, bionanomachines are computational devices that work at a nanoscale to perform simple functionalities like environmental sensing to more complex functionalities like actuation and manipulating the environment (i.e., human body). These devices have limited computation power and memory due to their nano size. Yet, their minute size is an edge for many novel applications, as they can be concealed and implanted in hard to access areas (such as deep inside the tissue of the human body) in a non-invasive manner. These machines are non-invasive and are made up of biodegradable material. The Role of Biological Nanomachines in Pervasive Healthcare Bionanomachines are resource-constrained devices and cannot perform complex tasks alone. Thus, bionanomachines communicate with each other to share information and execute designated tasks, forming a ‘biological ’. nanonetwork Healthcare and biomedical applications are some of the most promising use cases of nanonetworks, along with many other applications in industrial, environmental, and military domains. Some of the envisioned biomedical applications of nanonetworks include , continuous health monitoring, and tissue engineering. targeted drug delivery (TDD) Nanonetworks are envisioned to lead the world to a sophisticated healthcare experience. With the nanosensors and micro-robots patrolling inside the human body to collect physiological parameters, there is no need to go to labs to draw blood samples and wait for results. Even better, if nano actuators are connected to the nano \sensors, they can repair the detected malfunctioning in the body there and then. Biological nanomachines promise maximum therapeutic effects with very limited adverse effects. Other macro-scale therapeutics like chemotherapy not only kills the cancerous cells but also destroys the healthy cells of the human body. Whereas, nanotechnology-based TDD only targets the tumor sites. The potential benefits of nanonetworks can be increased when they are connected to external networks such as the internet. Connecting in body network with external networks enables pervasive healthcare, where a healthcare provider can monitor the patient remotely from the comfort of their home. The healthcare provider can demand physiological parameters like Blood pressure, glucose, ECG at any time, and can administer commands according to received parameters remotely. Additionally, after the recent pandemic of Covid-19 and the lockdown regime, there has been an accelerated interest in exploring remote therapeutics. Architecture of Bionanomachines Nanomachines can be fabricated using novel nanotechnology material (i.e., like and graphene nanoribbons) and by reprogramming biological materials like cells, viruses, bacteria, bacteriophage, erythrocytes, leukocytes, and stem cells or by artificially synthesizing biomolecules like liposome, nanosphere, nanocapsule, micelle, dendrimer, fullerene, and deoxyribonucleic (DNA) capsule. carbon nanotubes Certain design and development factors must be considered during the fabrication of nanomachines. These factors include the size, shape, stability, and biodegradability of the system. In biomedical applications, nanomachines are introduced into the blood vessels, from where they traverse to their targeted location. The smallest blood vessel is a capillary that is 5-10 micrometer in size; hence the upper bound of nanomachines must be set accordingly. On the other hand, nanomachines that are less than 5nm can be easily filtered out by kidneys. Thus, the size of the nanomachine must be propped. Channel characteristics like blood vessel geometry, elimination, adhesion, reaction, extracellular viscosity must be taken into account as well while fabricating nanomachines. Components of Nanomachines A bionanomachine is comprised of several hardware constituents. All the software and programming of the nanomachine is included in the information processing unit. The components of nanomachine are presented below: The information processing unit contains the programming part of nanomachine, which interprets command and process data. The functionality and behavior of nanomachine are coded in this unit. The information processing unit is capable of performing only trivial operations, like Boolean operations using only one transistor. Information Processing Unit Information processing unit for nanomachines is made up of nano-sized transistors like a single atom or quantum dots. Researchers from for the smallest transistor which has a gate length of just one nanometer. The processing unit is analogous to the nucleus of the cell. Lawrence Berkeley National Laboratory have provided a proof of concept Biological cells already exhibit the natural behavior of energy harvesting. A component of the biological cell called mitochondria releases Adenosine Triphosphate (ATP) as a chemical energy supply to charge the cell. Power Unit Communication is the basic functionality in any network, Likewise, the communication unit defines its capability of nanomachine to communicate with the environment. Nanomachines react in response to external stimuli produced by other nanomachines. To accomplish this, gap junctions located on the outer surface of the cell enables communication with the extracellular environment. Communication Unit The memory unit is narrowly associated with the information processing unit. Nanodevice needs a memory unit to store sensed data or memory can be used for some configuration and instruction set to be executed. Some nanomachines might not require memory at all because nanomachines are not supposed to perform complex computations. The nucleus of the cell can act as a long-term memory unit and the cytoplasm can perform the short-term memory functionality. Memory Unit Sensors continuously interact with the environment by collecting the chemical, physical and biological changes in the environment. Actuators work closely with the sensors by manipulating the environment in response to the sensed data. In biological cells, sensing is done by a natural process like ligand-receptor binding, or cilia can be used as a sensing antenna. Gap junction channels are used for actuation. Sensors and Actuators Locomotion is the ability of nanomachines to move around in the environment. The locomotion can be passive via molecular diffusion into the environment or active via molecular motors. Locomotion Unit Nanotechnology in medicine is going to have a major impact on the survival of the human race. - Bernard Marcus
