I've seen lots of studies going back over ten years using quantum dots to light up cancer cells or viruses in assays. Their use can make tests brighter, more sensitive and probably more accurate. Here's a quote about the subject from one PubMed NIH paper:

Quantum dots (QDs) are nanoparticles that are emerging as promising probes for ultrasensitive detection of cancer biomarkers. ... Their fluorescent properties have enabled QDs to be used as labels for in-vitro assays to quantify biomarkers, and they have been investigated as in-vivo imaging agents.