Currently, most contemporary nanoparticle-based immunoassays cannot distinguish between metabolically active and dead pathogens. Recently, a novel gold nanoparticle-based method for the assessment of bacterial susceptibility via surface plasmon resonance shifts was reported. The main drawbacks of this technique are the small, although significant, changes in the surface plasmon band and the assay��s inability to work in turbid or opaque media, due to the media��s strong scattering and absorbance that mask the nanoparticles�� plasmonic band. Hence, as some microorganisms, like Staphylococcus Fulvestrant epidermidis and Neisseria spp. among many others, can be present in the blood of infected patients, requiring isolation and growth in bloodcontaining media, it is vital to have clinical diagnostic assays for the assessment of antimicrobial susceptibility in blood. Consequently, we reasoned that a more robust system, which quickly determines bacterial susceptibility independent of the solution��s optical properties, could be developed using magnetic nanosensors and detection via water relaxation. According to the literature, it is widely acknowledged that a major benefit of using magnetic relaxation methods is that molecular detection can be achieved in opaque media, such as cell lysates, tissue extracts and complex biological fluids, notably blood, with high specificity and sensitivity. Therefore, we hypothesized that bacterialsusceptibility- monitoring nanosensors could be designed to differentially respond to the presence of various concentrations of nutrients, such as complex carbohydrates. Although superparamagnetic nanoparticles have been used as magnetic relaxation sensors for the detection of various targets, these nanoprobes have not been previously utilized for the detection of metabolic activity, which might lead to the potential development of nanosensors capable of Niltubacin clinical trial determining antimicrobial susceptibility in complex media. The polysaccharide nanosensors�� clustering should result in a significant change in the spin-spin relaxation time of the solution��s water protons, facilitating the reliable identification of effective antimicrobial agents. This can be achieved using dextran-coated iron oxide nanoparticles along with a protein with high affinity to carbohydrates, such as Concanavalin A, in a competition assay. Specifically, we hypothesized that upon Con A-induced clustering, the dextrancoated iron oxide nanoparticles can differentially respond to the polysaccharide levels associated with bacterial metabolism and growth. Hence, the higher the rate of bacterial metabolic activity, the fewer amount of the available polysaccharides would be, resulting in prominent changes in the sample��s DT2 when compared to those of the sterile medium.