The activity of alkaline phosphatase in breast cancer exosomes simplifies the biosensing design

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. Besides, the intrinsic activity of alkaline phosphatase (ALP) in exosomes as a potential biomarker of carcinogenesis as well as osseous metastatic invasion is also explored. To achieve that, as an in vitro model, exosomes from human fetal osteoblasts are used. It is demonstrated 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 mu L-1. Furthermore, this approach is used 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 in-dividuals based on the immunomagnetic separation using specific epithelial biomarkers CD326 (EpCAM) com-bined with the intrinsic ALP activity electrochemical readout.

Automated summary

This article introduces a biosensor combining immunomagnetic separation and electrochemical biosensing based on the intrinsic ALP activity of exosomes. By improving the analytical performance for detecting ALP activity in exosomes, reliable differentiation between breast cancer patients and healthy individuals is achieved.