Patients with metastatic cancer frequently do not respond well to the traditional methods of cancer treatment, which are restricted to radiation, medication chemotherapy, and surgery. They cause a number of detrimental side effects that accompany these treatments by concurrently damaging several healthy tissues. Since the nanoparticles improve therapeutic efficacy and provide significant advantages for targeted drug delivery directly to malignant cells and neoplasms, they may be employed as an alternative treatment. Existing cancer treatment medications effectively destroy growing tumor cells; the main issue with current chemotherapy is not that the treatments are ineffective, but rather that the body cannot withstand the drug concentrations needed to eradicate the cancer cells. The aggressiveness of chemotherapy treatment is typically based on doses the patient can tolerate rather than amounts required to eradicate all malignant cells. Drug concentrations high enough to destroy the tumors can kill the patient first. According to the World Health Organization, 7.6 million people died from cancer last year, making it one of the top causes of death. In the United States, the lifetime risk of acquiring cancer is 1 in 2 for males and 1 in 3 for women. The leading cause of cancer-related mortality for both men and women is lung cancer. The study, design, production, combination, control, and use of materials, devices, and frameworks at the nanometer scale (one meter is made up of one billion nanometers) is known as nanotechnology. In industries including construction, agriculture, development, microelectronics, and healthcare, it is becoming increasingly important. An artificially created device that can freely diffuse throughout the human body and interact molecularly with particular cells is known as a nanorobot.

Various agents can be applied to nanorobots based on their intended use or tissue location. The external shell is important because it must be able to release various ideal matrices that are not hazardous at the nanoscale level and be identified as an inert coating that is a component of the body. By adjusting the hole size, various sized molecules can be released (tunable porosity). Silica is an example of a molecule with a hard shell. Simple chemical techniques can readily functionalize the surface, but the most crucial factor is that the silica is not biodegradable, allowing for prolonged bodily activity. With the use of chemotactic sensors, certain chemicals and cells might be detected and readily targeted for action. Nanorobots will also be able to evaluate the surface antigens of each type of cell to determine the parent organ, if the cell is healthy, and nearly all other information about the cell. At least 0.5 cm3 of chemical agent could be delivered specifically into cells by a 1 cm3 injection of nanorobots, and the sensors could check chemical levels to prevent an unintentional overdose.

       
           
       
Fig 1: Nanobots attack on cancer cell.

Robots have become a viable alternative for the regulated and targeted distribution of medications. When compared to other traditional therapeutic administration methods of smaller sizes, the primary advantage of robotic devices is their regulated, accurate, and site-specific drug delivery capability. For the regulated and targeted administration of cells, genes, or medications, robots such as stimuli-responsive and surface-functionalized magnetic helical microswimmers can target specific single cells as well as the desired regions of the tissues. Usually, minimal changes to the physiological conditions (such as pH and temperature) at the target site trigger the mechanism of cargo/drug release in small robot-like (micro/nanorobots) without active intervention. However, complicated physiological settings or unexpected local differences may result in the delivery of potential off-target therapy.

5. Main objectives of nanobots in cancer therpy:

1.Targeted Drug Delivery:  By delivering chemotherapy medications straight to cancer cells, nanobots can reduce harm to healthy tissues and enhance the effectiveness of treatment.

2. Early Detection: By detecting cancer signals, they can be made to enable early diagnosis and treatment.

3.  Monitoring Treatment Response: By keeping an eye on tumor markers or variations in tumor size, nanobots can give real-time feedback on how effectively a treatment is working.

4. Gene therapy: By delivering genetic material to cancer cells, certain nanobots may be able to improve immune responses or fix mutations.

5. Thermal and Radiofrequency Treatment: By heating or irradiating tumor cells specifically to cause cell death, nanobots can help with targeted radiation therapy or hyperthermia.

6. Enhancement of Immunotherapy: By delivering immune-stimulating drugs straight to the tumor site, they can be utilized to increase the immune response against cancer cells.

7. Decreased Systemic Toxicity: Nanobots can lessen the overall toxicity and adverse effects of traditional therapies by focusing treatment at the tumor site.      

5. Types of Nanobots :

The nanobots can be classified in following some types:-

1.  DNA robots:   DNA nanobots are made of DNA strands and are capable of basic functions like medicine delivery to specific cells or molecular detection. These nanobots can be precisely assembled thanks to DNA origami techniques.

2. Microswimmers:  These nanobots use cilia or flagella to move like biological organisms, such as bacteria. They can be utilized for environmental monitoring or medicine administration because they can move across fluids.

3.magnetically controlled nanobots:  External magnetic fields are used by magnetically controlled nanobots to guide their motion. They are frequently made to carry out internal surgical procedures or to distribute drugs precisely.

4. Biohybrid nanobots : It  combine synthetic materials with biological elements, including live cells. For jobs like sensing or energy production, they can take advantage of the inherent capabilities of cells.

5. Smart Nanobots: These nanobots can change their shape in response to environmental stimuli like temperature or pH since they are outfitted with sensors and responsive materials.

6. Photothermal nanobots: These nanobots produce heat through the absorption of light for uses including cancer treatment, where localized heating aids in the destruction of malignant cells.

5.  Ideal characteristics of Nanobots:

It will use carrier wave frequencies between 1 and 100 MHz to encode messages into acoustic sounds in order to communicate with the doctor. In a process known as self-replication, it may create several copies of itself to replace damaged units. It can also be eliminated by active scavenger systems after the task is finished by letting it excuse itself through the normal human excretory channel. Nanorobots need to be between 0.5 and 3 microns in size, having components that are 1–100 nm in size. It will have a passive, diamond exterior to shield itself from immune system attacks.

5. Construction of nanobots:          

1. Core Framework:  A framework that offers structural stability frequently makes up a nanobot's core. Materials like DNA, polymers, or silica can be used to make this. One noteworthy method that gives you exact control over the stability and form of the nanobot is DNA origami.

2. Functional Modules: Nanobots can have a variety of modules that carry out particular tasks, like:
a. Sensing Units: To use sensors that react to particular stimuli in order to identify biological markers or changes in the environment.

b.  Actuators are devices that allow motion or action, like electrostatic actuators or structures modeled after flagella.

c. Systems for Drug Delivery: These systems can release therapeutic compounds in a controlled way and are frequently encased in polymeric nanoparticles or lipid-based carriers.

3. Communication Systems: Certain nanobots are built with the ability to communicate, which enables them to send and receive commands as well as information about their surroundings. Chemical signals or optical techniques can do this.

4. Energy Sources: Chemical gradients, light (via photosensitive materials), or even enzyme reactions can provide the energy needed for nanobots to function.

5. Approches for developing’s  Nanobots:

The creation of nanobots involves a number of strategies that make use of diverse scientific theories and technological advancements. These methods can be divided into groups according to their application, function, and design. The following are some crucial methods for creating nanobots:

1. Biological Methods:

a. DNA Origami: This technique makes nanostructures out of DNA molecules. By creating particular sequences that fold into desired shapes, researchers are able to precisely regulate the construction of the nanobot.

b. Biohybrid systems are made by fusing synthetic materials with biological elements (such as cells or proteins) to enable sophisticated functions like sensing or movement in response to biological cues.

2. Artificial Methods:

a.  microfluid:  By manipulating fluids at the microscale, microfluidics allows for the creation of nanobots that can traverse and react to chemical surroundings.

b. Nanoscale Fabrication Methods: Nanoscale devices and structures are made using methods like self-assembly and lithography. These techniques enable fine-grained control over nanobots' dimensions and form.

3. Chemical Methods:

a. Chemical Motors: These nanobots move by means of chemical reactions. Catalytic reactions, for instance, can create gas bubbles that move the nanobot through a solution.

b. Smart nanomaterials: These substances react to environmental cues like temperature or pH, enabling nanobots to alter their form or discharge payloads in response to certain circumstances.

4. Mechanical Methods:

a. Self-Propelled Systems: Some nanobots are made to move on their own by utilizing cilia or flagella, which are biologically inspired systems.

       
           
       
Fig 3. Approaches for developing nanobots

5. Advantages of  nanobots used in cancer therpy:   

1. Targeted Drug Delivery:  By specifically targeting cancer cells, nanobots can reduce harm to healthy organs. This focused strategy lessens side effects while increasing chemotherapy's effectiveness.

2. Better Drug Solubility:  By increasing the solubility and bioavailability of poorly soluble medications, nanobots can open up more efficient therapy alternatives.

3. Real-time Monitoring:  Sensor-equipped nanobots can keep an eye on drug distribution and tumor surroundings in real time, providing vital information for modifying treatment regimens.

4. Combination Therapies:  They can help deliver several therapeutic agents at once, enabling combination treatments that can combat drug resistance.

5. Decreased Systemic Toxicity:  Nanobots can dramatically lower systemic toxicity by delivering medications straight to the tumor site, improving patient tolerance and quality of life throughout treatment.

6. Improved Imaging Methods: By enhancing imaging methods, nanobots can help identify and diagnose malignancies early.

5. Disadvantages of nanobots used in cancer therapy:

1. Safety and Biocompatibility: Little is known about how nanobots may affect the human body over time. Nanobot materials may cause immunological reactions or build up in organs, raising questions regarding biocompatibility and possible toxicity.

2. Safety and Biocompatibility: Little is known about how nanobots may affect the human body over time. Nanobot materials may cause immunological reactions or build up in organs, raising questions regarding biocompatibility and possible toxicity.

3. Manufacturing and Scalability: Producing nanobots is frequently an intricate and expensive process. Accessibility and affordability may be impacted by the major hurdle of scaling up production for clinical usage.

4. Regulatory Obstacles: The market launch of nanobots may be delayed due to the strict regulatory criteria for approval. The clearance procedure for nanotechnology may be made more difficult by the absence of set rules.

5. Technical Restrictions: The therapeutic efficacy of current nanobot designs may be hampered by their inability to move, navigate, and function in the intricate environment of the human body.

5. Application of nanobots:  

1. Photothermal Therapy: When directed correctly, nanobots may absorb light and produce heat to kill cancer cells only.

2. Gene therapy: By delivering therapeutic genes to cancer cells, nanobots may be able to stop tumor development or trigger apoptosis.

3. Enhancement of Immunotherapy: By delivering immune-modulating chemicals, nanobots can increase immune responses against malignancies.

4. Imaging and Diagnosis: By enhancing imaging methods, nanobots can help in tumor monitoring and early identification.