Albumin nanoparticles with tunable ultraviolet-to-red autofluorescence for label-free cell imaging and selective biosensing of copper ion.

Early and simple detection of aberrant cooper metabolism in diseases with neurological-manifestations and several other conditions, including cancer, becomes an urgent necessity. Instrumental methods used today are limited to high-cost equipment and reagents and demand highly qualified personnel. In this work, we report easy-to-use and cost-effective nano-sized sensors for the selective and quantitative detection of copper ion based on fluorescence quenching. Glutaraldehyde cross-linked albumin nanoparticles with tunable ultraviolet-to-red autofluorescence emissions are developed as dual-agents for sensing and imaging. These albumin nanoparticles show great selectivity towards copper ion when tested against a selection of biochemical components and other metal ions, and a limit of detection as low as 1.9 μM, relevant for sensing in clinical diagnosis, was determined. In addition, a lack of toxicity and good cellular uptake were observed and the ultraviolet-to-red intrinsic fluorescence of the albumin nanoparticles was preserved when tested in vitro on NIH:OVCAR3 cell line. Preliminary studies confirm the albumin nanoparticles' ability to detect Cuin vitro and establishes their potential for future practical use.