Photonics for Biomedicine

The challenge of detecting very small amounts of biological material, for example antibodies and viruses, has recently turned from scientifically and medically interesting to an acute general interest problem. Polymerase chain reaction (PCR) amplification is the current method of choice to address this, but takes hours to complete. We have demonstrated the detection of antibodies in an extremely dilute solution by using M13 bacteriophage virus, linked both to fluorescent molecules and to custom antibody receptors. The detection is based on shifts in the lasing threshold of the solution as a function of antibody concentration. This is a first step in creating compact, sensitive and instantly readable detection kits.

Design of the virus laser. a Model of the atomic structure of a lasing detection probe composed of M13 bacteriophage. b Optical configuration for some of the experiments conducted.
Time-dependence of the intensity at 523.5 nm at pump energies initially above threshold at 1.3 × 1016 photons pulse−1 ± 4.7% (purple) and below threshold at 1.6 × 1015 photons pulse−1 ± 4.4% (green). The concentration of cp-mAb, which is a ligand bound by M13, in the gain medium after mixing increases in steps from 0 fmol mL−1 to 9 fmol mL−1, 29 fmol mL−1 and then 90 fmol mL−1. The arrows indicate when cp-mAb was added to the reservoir, and the lengths of the arrows are proportional to the amount added to the reservoir at each step.

Hales, J.E., Matmon, G., Dalby, P.A. et al. Virus lasers for biological detection. Nat Commun 10, 3594 (2019).