A major impediment to improving the treatment of concussion is our current inability to identify patients that will experience persistent problems after the injury. Recently, brain-derived exosomes, which cross the blood-brain barrier and circulate following injury, have shown great potential as a noninvasive biomarker of brain recovery. However, clinical use of exosomes has been constrained by their small size (30-100 nm) and the extensive sample preparation (>24 hr) needed for traditional exosome measurements. To address these challenges, UPENN researchers developed a smartphone-enabled optofluidic platform to measure brain-derived exosomes. Sample-to-answer on this chip is 1 hour, 10x faster than conventional techniques. The key innovation is an optofluidic device that can detect enzyme amplified exosome biomarkers, and is read out using a smartphone camera. Using this approach, the researchers detected and profiled GluR2+ exosomes in the post-injury state using both in vitro and murine models of concussion.
Rapid exosome-based prognosis of mild traumatic brain injury (mTBI) on a microchip
(a) A microfluidic-based platform to isolate and profile brain-derived exosomes to diagnose mild traumatic brain injury (mTBI). Following mTBI, brain-derived exosomes (pink) that carry molecular information from their mother cells circulate in the blood amongst a vast background exosomes (blue). (b) The results, from serum to a digital read out, are automated on the microchip platform and can be carried out in less than 1 hour, empowering healthcare providers with real-time molecular information at the point of medical care. (c) On our microchip, first CD45 and CD61 coated functionalized microbeads are used to negatively select exosomes from abundant cell types (leukocytes, platelets) prior to positive selection to diminish background, which would otherwise limit sensitivity. (d) CD81 (a pan-exosome marker) functionalized microbeads are then used to capture the remaining exosomes. (e) These isolated exosomes are labeled with GluR2 antibodies, functionalized with the catalyst Horseradish Peroxidase (HRP). (f) The presence of HRP on these microbeads, leads to the enzymatic generation of fluorescent dye, which can be easily detected by our smartphone based fluorescence detection.