Plasma-assisted quadruple-channel optosensing of proteins and cells with Mn-doped ZnS quantum dots.

Information extraction from nano-bio-systems is crucial for understanding their inner molecular level interactions and can help in the development of multidimensional/multimodal sensing devices to realize novel or expanded functionalities. The intrinsic fluorescence (IF) of proteins has long been considered as an effective tool for studying protein structures and dynamics, but not for protein recognition analysis partially because it generally contributes to the fluorescence background in bioanalysis. Here we explored the use of IF as the fourth channel optical input for a multidimensional optosensing device, together with the triple-channel optical output of Mn-doped ZnS QDs (fluorescence from ZnS host, phosphorescence from Mn(2+) dopant, and Rayleigh light scattering from the QDs), to dramatically improve the protein recognition and discrimination resolution. To further increase the cross-reactivity of the multidimensional optosensing device, plasma modification of proteins was explored to enhance the IF difference as well as their interactions with Mn-doped ZnS QDs. Such a sensor device was demonstrated for highly discriminative and precise identification of proteins in human serum and urine samples, and for cancer and normal cells as well.