# Exploring the Potential of Sensing for Breast Cancer Detection
## 5 Biosensors for Breast Cancer Detection
### Electrochemiluminescence Biosensor  
Electrochemiluminescence (ECL) is a technique in which a specific chemical reaction is triggered by applying an electrical current resulting in light emission [104; 105; 106]. This process has been used in various fields, including analytical chemistry, clinical diagnostics, and biosensors. Biosensors are analytical devices that utilize biological molecules or living organisms to detect and measure different analytes [104; 105; 106]. These devices have numerous applications, including medical diagnosis, environmental monitoring, and food safety. The use of ECL in biosensors offers several advantages over other detection techniques. Firstly, ECL has high sensitivity (i.e., 0.1 fm to 5 Pm [107]) and can detect low concentrations of analytes with high accuracy. Secondly, ECL is a fast and reliable method providing real-time results with minimal sample preparation. Lastly, ECL has a wide dynamic range and can detect a broad range of analytes, making it an ideal detection method for many biosensor applications. One of the most common biosensor applications of ECL is in the detection of biomolecules such as proteins, DNA, and antibodies. In this method, the biosensor is designed to capture the biomolecule of interest using a specific recognition element such as an antibody [104].  
The captured biomolecule is labeled with an ECL probe, emitting light when an electrical current is applied. The amount of light emitted is proportional to the concentration of the biomolecule, allowing for quantitative analysis. ECL biosensors have numerous applications in clinical diagnostics, including detecting infectious diseases, cancer biomarkers, and genetic disorders. These biosensors offer a compassionate and accurate detection method that can be performed rapidly with minimal sample preparation, making them ideal for point-of-care testing. In addition to clinical diagnostics, ECL biosensors are also used in environmental monitoring to detect contaminants such as heavy metals, pesticides, and toxic chemicals. These biosensors offer a reliable and cost-effective method for monitoring  
Figure 3: Detection of target microRNA-21 using SERS [102].  
ecological pollutants, allowing for early detection and mitigation of potential hazards. In conclusion, ECL is a powerful technique that has revolutionized biosensor applications. ECL biosensors offer a sensitive and accurate detection method that can be performed rapidly with minimal sample preparation.  
In [108], the authors designed an ECL biosensor by considering a silica-based mesoporous material for detecting SKBR-3 cells. The authors observed from the experimental setup that (a) the lower limit of quantitation was 20 cells/mL, (b) the linear dynamic range was 20 to 2000 cells/mL, (c) the experimental setup was able to determine the concentration of SKBR3 cells, and (d) MCF-7 and MDA-MB-231 cancer cell lines were determined. In [109], a sensing platform was designed by considering gold-nanoparticle-based carbon nitride, and this arrangement of a potential from \(-1.2\) V to 0 V is associated with ECL in the presence of peroxydisulfate. The outcomes from this experimental setup are as follows: (a) the linear range was found to be from 10 fg mL\({}^{-1}\) to 100 ng mL\({}^{-1}\); (b) the LOD was 0.2 fg mL\({}^{-1}\); (c) the ECL emission experienced a peak at 550 nm; (d) a stable and amplified output response was observed. This ECL method is suitable for specifying cancer biomarkers.