A biosensor based on the intrinsic ALP activity of exosomes

This work addresses a biosensor combining the immunomagnetic separation and the electrochemical biosensing based on the intrinsic ALP activity of the exosomes. This approach explores for the first time two different types of biomarkers on exosomes, in a unique biosensing device combining two different biorecognition reaction: immunological and enzymatic. Researchers at Universitat Autònoma de Barcelona also explore the intrinsic activity of alkaline phosphatase (ALP) in exosomes as a potential biomarker of carcinogenesis as well as osseous metastatic invasion.

To achieve that, as an in vitro model, exosomes from human fetal osteoblasts are used. The researchers demonstrate that the electrochemical biosensor improves the analytical performance of the gold standard colorimetric assay for the detection of ALP activity in exosomes, providing a limit of detection of 4.39 mU L^-1, equivalent to 10⁵ exosomes μL^-1. Furthermore, they use this approach to detect and quantify exosomes derived from serum samples of breast cancer patients. The electrochemical biosensor shows reliable results for the differentiation of healthy donors and breast cancer individuals based on the immunomagnetic separation using specific epithelial biomarkers CD326 (EpCAM) combined with the intrinsic ALP activity electrochemical readout.

Different approaches for the detection of alkaline phosphatase (ALP) activity in osteoblast-derived exosomes by optical readout and electrochemical biosensor