The number of receptors expressed by cells plays an important role in controlling cell signaling events, thus determining its behaviour, state and fate. Current methods of quantifying receptors on cells are either laborious or do not maintain the cells in their native form. Here, a method integrating highly sensitive bioluminescence, high precision microfluidics and small footprint of lensfree optics is developed to quantify cell surface receptors. This method is safe to use, less laborious, and faster than the conventional radiolabelling and near field scanning methods. It is also more sensitive than fluorescence based assays and is ideal for high throughput screening. In quantifying β(1) adrenergic receptors expressed on the surface of H9c2 cardiomyocytes, this method yields receptor numbers from 3.12 × 10(5) to 9.36 × 10(5) receptors/cell which are comparable with current methods. This can serve as a very good platform for rapid quantification of receptor numbers in ligand/drug binding and receptor characterization studies, which is an important part of pharmaceutical and biological research.

C. T. Lim and co‐workers describe a rapid and sensitive bioluminescence‐based microfluidic method for quantifying receptor numbers on live cells. On page 943, this integrated, lens‐free optical platform allows the determination of signals from the cell surface with high sensitivity. Compared to conventional approaches, the combined use of bioluminescence and microfluidics makes it safe to use, reduces background noise, improves sensitivity, requires smaller sample volumes, and allows high‐throughput sampling over thousands of cells.