Tiny Detectives: Nanorobots and the Early Diagnosis of Breast Cancer
By: Amelia Tong
Breast cancer is the second-most common cancer among women in the United States. While advancements in cancer treatments and diagnoses have rapidly progressed over the last few decades, cancer is still the second leading cause of death for women in the US. Late detection of cancers like breast cancer usually leads to high mortality rates, but if breast cancer is found earlier, there is a wider array of treatment options and an improved chance of survival.
For example, women whose breast cancer is detected at an early stage have a 93% or higher survival rate in the first five years.
Thus, the necessity of developing more sensitive and effective tools for early breast cancer diagnosis cannot be overstated. In this article we will explore challenges for early breast cancer diagnosis, common types of nanorobots and locomotion, and the impact of nanotechnology on breast cancer diagnosis.
While there are many well-known and extensively studied breast cancer diagnostic approaches, such as mammography, biopsy, and magnetic resonance imaging, these techniques often have limitations ranging from cost and accessibility to suitability for women of all ages. In addition, routine screening is not recommended for women under the age of 40, but breast cancer in younger women may be more aggressive and less responsive to treatment. Mammography, the current standard breast screening technique in which an x-ray picture of the breast is taken, is less sensitive to small tumors, is less effective for women under 40 years old and those with dense breasts, and fails to provide information on eventual disease outcome (Wang, 2017). Other limitations of common breast cancer diagnostic methods include the low expense and low specificity of MRI and the exposure to high radiation levels of a contrast-enhanced digital mammography. In addition to the limitations of common breast cancer diagnostics, socioeconomic and status of healthcare within a country also produces challenges to the early diagnosis of breast cancer. In most high-income countries, more than 70% of breast cancer patients are diagnosed in stages I and II while only 20%-50% of patients in the majority of low- and middle-income countries are diagnosed in the earlier stages (Unger-Saldaña, 2014). Thus, there is an urgent need for a highly sensitive and accessible method for rapidly diagnosing breast cancer. Nanotechnology, a possible solution to this issue, may be almost microscopic, but their potential impact is immeasurable.
Nanorobots are extremely small, functional machines that open the door for new procedures at the cellular level along with more precise diagnosis and treatment on the nanometer scale, 10-9 of a meter. Such medical robots necessitate the miniaturization of materials and other parts to carry out their precise functions and to exist harmoniously within the human body (Li et al., 2017). Recently, the field of medical robotics and specifically nanorobotics has expanded drastically, driven by technological advances in areas such as motors, materials, and medical imaging. Another type of nanotechnology, nanoparticles, can be used as probes in biosensing, in vivo imaging, and immunostaining. Nanoparticles have optical properties, which enables the emission of different colors based on the size of the nanoparticle. Another beneficial quality of nanoparticles is their size. While they are large enough to stay in circulation for a relatively period of time before reaching desired target, they are also small enough to penetrate many biological barriers, such as cell membranes (Chen et al., 2014). While nanotechnology is a broad field, there is a distinct potential for revolutionizing early breast cancer diagnosis through nanoparticles and nanorobots.
Figure 1: Graphical abstract of a theoretical, autonomous nanorobot moving through the human bloodstream
Many nanoparticles utilize tumor homing to target and locate cancer, usually by using the overexpressed biomarkers of cancerous cells, such as the human epidermal growth factor receptor 2 (HER2). In about 25% of breast cancers, the HER2 gene over replicates itself, which results in an excess of proteins that cause breast cancer cells to grow and divide uncontrollably (Saeed et al., 2017). This overexpression can be used as a target for nanorobots and nanoparticles in the imaging of breast cancer cells. In the case of gold nanoparticles, a biosensor that enables the identification of HER2 positive breast cancer cells, nanotechnology enables the early diagnosis of breast cancer, as the concentration of nanoparticles relates to the concentration of biomarkers (Leng et al., 2018). Currently, the most common tool of determining the HER2 status of breast cancer involves a biopsy, in which small pieces of breast tissue are removed and then examined more closely in a lab. However, through nanoparticles, HER2 status may be discerned without the removal of breast tissue, shortening diagnosis time and simplifying the process. Similarly, for breast cancer in general, nanoparticles can theoretically simplify the process, resulting in quicker results, and overcome some of the barriers posed by current breast cancer diagnosis tools. While mammograms are sometimes less effective for younger women with dense breast tissue, nanoparticles are not hindered by the physical attributes of breast tissue and can diagnose breast cancer regardless of breast density. Thus, nanoparticles may be a more effective, more accurate, and more direct tool of breast cancer diagnosis compared to the current diagnostic techniques.
The logical next step in the improvement of breast cancer diagnosis and prognosis through nanotechnology is incorporating nanoparticles into nanorobots, as the use of nanodevices with higher complexity is a current focus of nanotechnology today (Chattha et al., 2023). The process of miniaturizing robots that are functional and beneficial in the environment of the human body faces many challenges, such as locomotion and toxicity (Li et al., 2017). Due to the viscosity of blood, it is almost impossible for nanorobots to pass through blood vessels, and the movement of molecules within blood can cause the nanorobot to act unpredictably (Giri et al., 2021). While research on risks related to nanorobots have so far been limited, early indications of potential hazards include the use of hazardous materials and UV light in nanorobots. (Arvidsson et al., 2020). Thus, while nanorobots have incredible potential in the field of breast cancer diagnosis and prognosis, as shown in the success of gold nanoparticles successfully sensing HER2 proteins of breast cancer, there is still an abundant amount about nanorobots that we do not know. However, these tiny machines can have an immeasurable impact and may be the future of medicine.
Figure 2: Breast cancer cell with HER2 protein overexpression, which tends to grow faster and is more likely to spread compared to HER2-negative breast cancers
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Images:
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