Physical sciences / Nanoscience and technology / Nanoscale devices / Biosensors [URI /639/925/927/59] Biological sciences / Biological techniques / Nanobiotechnology / Biosensors [URI /631/1647/350/59] Subject area: NANOMECHANICAL SENSORS Title: Measuring a response in blood serum Standfirst: Nanomechanical cantilevers can determine the concentration of active drugs in human serum. F. Huber, H.P. Lang, and Ch. Gerber The recent increase in the number of bacteria that are resistant to drugs, such as methicillin- resistant S. aureus (MRSA) and vancomycin-resistant Enterococci (VRE), represents a significant threat to public health. According to a report by the Centers for Disease Control and Prevention [1], for example, 2 million people are infected and 23,000 die each year in the United States from bacteria that are resistant to antibiotics; many more deaths occur as the result of complications associated with other conditions caused by an antibiotic-resistant infection. This increase in drug-resistant bacteria combined with a decline in the development of antibiotics, means that drug resistance is an impelling global concern [2]. One innovative way to try to address these clinical problems and develop effective therapies is to use mechanical signals, rather than chemical or electrical signals, to explore novel antibiotic therapies. Nanomechanical sensors based on microcantilevers provide a technology platform for label-free and sensitive detection of biomolecular interactions [3] on a solid surface. However, the development of a new drug requires a detailed understanding of its therapeutic effects in a complex environment, such as in a patient’s blood. Writing in Nature Nanotechnology, Joseph Ndieyira, Rachel McKendry and colleagues now show that arrays of nanomechanical cantilevers can characterise the mechanical response of the bacterial cell wall to antibiotics while taking into account binding to other molecules in solutions that reduce their potency [4]. Nanomechanical sensors work by measuring the bending of a cantilever that is generated by molecular binding/adsorption taking place on the surface of the cantilever (Figure 1). The cantilever bending is a result of surface stress due to factors such as electrostatic and van der Waals forces, as well as conformational changes of molecules and molecular layers upon a binding event. The main advantage of the microcantilever technique is the possibility