Detection of Antibodies in Blood Plasma Using Bioluminescent Sensor Proteins and a Smartphone

Antibody
detection is of fundamental importance in many diagnostic
and bioanalytical assays, yet current detection techniques tend to
be laborious and/or expensive. We present a new sensor platform (LUMABS)
based on bioluminescence resonance energy transfer (BRET) that allows
detection of antibodies directly in solution using a smartphone as
the sole piece of equipment. LUMABS are single-protein sensors that
consist of the blue-light emitting luciferase NanoLuc connected via
a semiflexible linker to the green fluorescent acceptor protein mNeonGreen,
which are kept close together using helper domains. Binding of an
antibody to epitope sequences flanking the linker disrupts the interaction
between the helper domains, resulting in a large decrease in BRET
efficiency. The resulting change in color of the emitted light from
green-blue to blue can be detected directly in blood plasma, even
at picomolar concentrations of antibody. Moreover, the modular architecture
of LUMABS allows changing of target specificity by simple exchange
of epitope sequences, as demonstrated here for antibodies against
HIV1-p17, hemagglutinin (HA), and dengue virus type I. The combination
of sensitive ratiometric bioluminescent detection and the intrinsic
modularity of the LUMABS design provides an attractive generic platform
for point-of-care antibody detection that avoids the complex liquid
handling steps associated with conventional immunoassays.