Biosensing has been one of the hottest topic attracting scientific minds since long back. It is so as biological entities are very complex and are directly associated with the existence of a healthy environment. The design of biosensors also has witnessed significant changes in the recent past. Biosensors for applications as diverse as food quality estimation, environmental monitoring, and diagnosis of clinical and metabolic complications have come to the fore. Nanotechnology has bestowed some highly exciting ingredients for the improvement of sensing phenomenon. The use of diverse nanomaterials ranging from nanoparticles, nanotubes, nanorods, and nanowires has enabled faster detection and its reproducibility in a much better way. The unique properties of nanomaterials such as high electrical conductivity, better shock bearing ability, and the sensitive responses such as piezoelectric and versatile color based detection mechanisms are only the results of congregation of nanomaterial properties. This paper highlights the different types of biosensors based on different types of nanomaterials and their developmental and implicational aspects.

ROS have vital roles in cellular signaling and homeostasis. At low concentration, ROS promotes cancer cell survival by the activation of growth factors and MAP-kinases (MAPKs) that further activates cell cycle progression. At high concentration, ROS produces oxidative stress that activates programmed cell death or apoptosis. However, this fine distinction of ROS action either as a growth promoter or pro-apoptotic agent depends not only on dosage (concentration) but also on the duration, type, and site of ROS generation. The female steroid estrogens and their various metabolites generate ROS in the breast cancer cells. Slow, sustained and moderate level of ROS generated by estrogens and their metabolites cause initiation and progression of breast cancer. ROS generated by estrogens affect pro-proliferative (e.g. cyclin D1, Cdc2), prosurvival (e.g. AKT), antiapoptotic (e.g. BCl2) and pro-inflammatory (e.g. NF-κB) molecules. These multipronged actions of ROS lead to the activation of several signaling pathways involved in the breast cancer cell survival and proliferation, resulting in the progression of breast cancer. Present review article provides insights into the role of estrogen generated ROS and its associated signaling pathways in the initiation and progression of breast cancer. The importance of ROS as breast cancer drug target has also been discussed.