Despite significant advances, mortality from brain tumors remains high with five-year survival rates of 36%, according to the National Cancer Institute. More accurate diagnoses might improve the situation, but tissue biopsies are invasive and can miss important information about a tumor’s make-up. Imaging-based methods, meanwhile, do not offer sufficient sensitivity and resolution. Now, researchers reporting in ACS Nano have developed a biosensor that could help physicians precisely diagnose brain cancer from a minute blood sample.