# Bioluminescent Immunophage Sensors for the Quantification of Insulin

## TL;DR

A new bioluminescent sensor called BLIPS can detect insulin quickly and accurately, which could improve diabetes diagnosis and treatment.

## Contribution

The novel BLIPS platform uses phage-displayed immunosensors with split-nanoluciferase to detect insulin with high specificity and sensitivity.

## Key findings

- BLIPS detects insulin down to 50 pM within minutes.
- The sensor has no cross-reactivity with IGF-1 and IGF-2.
- The platform uses phage display to solubilize otherwise insoluble antibody fragments.

## Abstract

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.