The idea of using multiplexed arrays of nanometer-sized protein binding sensors to identify several molecules at the same time is well established and used in a variety of drug development applications, from candidate identification to target selection.
Now researchers from the Massachusetts Institute of Technology have shown there is merit in using arrays made up of identical sensors, particularly for producers of monoclonal antibody (MAb) based drugs.
The first thing the team looked at was antibody binding strength. Therapeutic antibodies only work if they bind targets effectively, but hard to control variations resulting from the cell culture-based production process can produce minute differences in binding strength between MAb batches.
At present BioPharmas address this by testing each batch to make sure it has the correct characteristics, which is time consuming and expensive. The MIT team found that, by using nanosensor arrays, they could accelerate this process considerably.
The researchers – under the leadership of chemical engineering professor Michael Strano – could also detect whether the antibodies were glycosylated, which is hard to do otherwise because interactions between the core molecule and the coating sugar units are very weak.
Unglycosylated antibodies – or those that have been glycosylated inappropriately during the production process – can provoke an immune response which renders them useless as therapeutic agents, which is a major headache for BioPharmas as Strano explained.
“This has been a problem for pharmaceutical companies and researchers alike, trying to measure glycosylated proteins by recognizing the carbohydrate chain,” he said, adding that “a nanosensor array can do is greatly expand the number of opportunities to detect rare binding events. You can measure what you would otherwise not be able to quantify with a single, larger sensor with the same sensitivity.”
Cell line selection
Strano and his team – researcher Nigel Reuel, MIT faculty members Krystyn Van Vliet, Christopher Love and Dane Wittrup as well as Ramon Wahl from Novartis – also used the arrays to identify the most productive cell lines for biomanufacturing.
To do this they grew human embryonic kidney cells in a vessel coated with arrays of the sensors, which bound clones that strongly expressed the desired antibody on their outer surfaces thereby enabling their selection and culturing.
Wahl said: “Carbon nanotubes coupled to protein-binding entities are interesting for several areas of bio-manufacturing as they offer great potential for online monitoring of product levels and quality. Our collaboration has shown that carbon nanotube-based fluorescent sensors are applicable for such purposes, and I am eager to follow the maturation of this technology.”