Bioluminescent Immunophage Sensors for the Quantification of Insulin

Diagnosis and then therapeutic management of diabetes require accurate, rapid monitoring of key biomarkers. Currently, only glucose levels guide diabetes management. Reliance on one biomarker can lead to diabetes misdiagnosis and improper treatment. However, adding insulin to the diagnostic portfolio could improve patient outcomes. Toward this goal, we report BLIPS (Bioluminescent Immunophage Sensor), an easy-to-produce, point-of-care immunoassay platform for the detection and quantification of insulin. BLIPS combines the highly specific detection capabilities of antibodies, ease of handling and production of phage display, and a reliable, turn-on optical signal of nanoluciferase. Specifically, fragment antigen binding (Fab) regions of an antibody sandwich pair were each genetically fused to split-nanoluciferase fragments to detect insulin via the activity of the reconstituted nanoluciferase. These constructs are too insoluble for E. coli overexpression, but can be readily displayed on M13 phage. BLIPS allows for the detection of insulin down to 50 pM within minutes and provides a working range of up to 10 nM with no response to the competing and highly homologous peptide hormones IGF-1 and IGF-2. This work paves the way for rapid, low-cost bedside monitoring of insulin to improve the diagnosis and management of diabetes and also expands the generality of the robust split-luciferase sensor system to include phage display-solubilized receptors.