Dr. Bashkin gave a background of bioluminescence and limitations of existing imaging modalities and then discussed the next generation probes being developed at Zymera. Bioluminescence imaging (BLI) technology improved tools for biological detection and imaging through nanotechnology allowing for noninvasive study of ongoing biological processes. Bioluminescence imaging utilizes native light emission from one of several organisms which bioluminesce. The three main sources are the North American firefly, the sea pansy (and related marine organisms), and certain bacteria. The DNA encoding the luminescent protein is incorporated into the laboratory animal either via a viral vector or by creating a transgenic animal. Many of the existing imaging modalities like MRI, Ultra Sound, and CT Scan used for imaging, show high resolution but low sensitivity. Bioluminescence gives good sensitivity which can be expanded but there are several limitations in the existing bioluminescence imaging technology. Cell transfection is not possible with certain cell types, short luciferase enzymes have half life in serum, emission wavelengths limit in-vivo sensitivity, there is limited color multiplexing, low in-vivo ATP concentrations, and limited spatial resolution.
Zymera technology overcomes most of these limitations, with injectible probes, mutated luciferase, energy transfer, quantum dots, and renilla luciferase, said Bashkin, and further expanded on each of these. Attributes of the improved luciferase are that they are smaller and lighter with long serum half life. Luc8 (renilla luciferase) is a form of luciferase that exhibits improved light output and serum stability over traditional versions of the enzyme. Dr. Gambhir at Stanford has come up with 8 mutations that increase serum sensitivity 200 times and there is 4 fold increase in light output, as shown by Luc 8 data. Zymera’s Bioluminescent Resonance Energy Transfer (BRET) probes, developed by Dr. Rao at Stanford, combine this recombinant form of renilla luciferase (Luc8) with quantum dots, enabling non radiative energy transfer from Donor to Acceptor. The BRET Qdot probes can be targeted; conjugated with biomolecular recognition molecules (antibodies and peptides), or activity-based. Quantum Dots from Life Technologies are made of semiconductor material with a polymer coating. The BRET-Qdot probes allow tumor xenograft to be made from just 100 cells rather than 20,000 and enable the visualization of early stage metastasis in-vivo. Zymera probes are active in serum and blood, can be multiplexed for in vivo imaging, and are designed as proximity and activity based biosensors. They do not require external illumination source, thus eliminating tissue autofluorescence and facilitate deep tissue imaging. Currently in technology pipeline, there is non toxic version of Qdot, for use in humans, for diagnostic purposes. Zymera is establishing collaborations with pharmaceutical and biotechnology companies for BRET-Qdot probe development and applications, and has active collaborations with OncoHealth, Genentech, and Amgen, said Bashkin.