CRISPR-Cas12a-Assisted DNA Circuit for Nonmicroscopic Detection of Cell Surface Receptor Clustering

Protein–protein interactions (PPIs) on the cell surface have been of great interest due to their high clinical relevance and significance; however, the methods for detecting PPIs heavily rely on microscopic instruments. In this work, we designed a Cas12a-assisted DNA circuit for detecting cell surface receptor clustering events without a dependence on microscopy. This nonmicroscopic approach is based on the proximity principle, where localized protein–protein interactions such as receptor clustering are converted into DNA barcodes. These barcodes can then be identified by Cas12a for signal generation in the bulk. The compatibility of the circuit with Cas12a was first experimentally verified. Several leak reactions were identified and minimized. Lastly, we implemented this design in human breast cancer cell line models to distinguish the different levels of human epidermal growth factor receptor 2 (HER2) homodimers and heterodimers with HER1 and HER3 semiquantitatively without the use of a microscope. Overall, our proposed Cas12a-assisted DNA circuit for detecting cell surface receptor clustering shows the potential for fast screening in diagnostic applications and drug discovery, demonstrating the promising use of enzymatic DNA circuits in biological applications.