According to my biochem-undergrad kid, surface plasmon resonance is a thing; it had come up in classes. "It's like doing an ELISA with no secondary antibody". Someone here will know what that means. I don't!
A regular ELISA/immunoassay is: surface->Ab->protein<-Ab+signal. In school these are taught as "sandwich-assays". Basically you have one antibody to bind your molecule of interest to your substrate, and then another second which binds the bound molecule... which has been bound to the surface. This second antibody is decorated with an enzyme which will do something fancy (color-change) or a fluorescent protein to light-up if we shoot it with a laser. SPR is a label-free approach which results in an optical response in real-time as molecules associate with the SPR sensor. Detection is then a function of how long you need to let things bind to the sensor before your ability to detect the signal optically.
Sounds like your undergrad kid has been paying attention in class...
It's a very sensitive detection technique that uses some cool properties of light. We used it 20+ years ago in grad school (they were very expensive machines that were extremely hard to master; everything from calibration to routine operation was significantly more challenging than most devices I worked with) and I think it has quite a history before that. Never heard of it being used for rapid detection in a public environment; my experience is that things that work in a lab setting often don't externally unless somebody comes up with a good technology improvement (think vacuum tubes -> transistors -> small radios).
It’s a thing, but doing a saliva test with limited sample prep (which you need to be beat PCR, otherwise you might as well just make more known to work qPCR machines) is not something anyone has accomplished with it for any virus. It’s a promising technology; but not for having a widely deployable test before we have boring old ELISA antigen tests. Which we have developed for plenty of viruses, and which some individual companies alone can manufacture at a rate of several per second with existing production capacity.
I’m glad more money is being put towards research in this tech (I used to study plasmonics from the physics side), I don’t think it’ll make a difference for COVID specifically before it’s too late to matter.
Test complexity (sample prep, test workflow) is a real challenge to achieving testing scales at orders of magnitude above what is presently available.
We should hopefully have boring old ELISA antigen tests shortly, thanks to Abbott and many of the other folks we've all heard from. The real challenge is scaling testing beyond what can be reasonably implemented from central lab facilities.
ELISA tests don’t need to be done at central lab facilities; there are plenty of machines on the market with varying levels of automation (and many already in hospitals, even in ones that aren’t particularly outstanding). I’m curious what barrier to scaling those with COVID (either by making more of these machines, or repurposing other test capacity) you’ve identified that makes bringing a totally new machine to market more attractive, from a scaling perspective.
> The real challenge is scaling testing beyond what can be reasonably implemented from central lab facilities
The SPR machines I’m familiar with are not inexpensive. Are there machines appropriate for these tests that are less expensive such that it could be rolled out widely? Sample cost is low, but a warehouse shift change of several thousand people isn’t going to need only one machine for screening as the load on the machines will be very bursty.
If one is clever, one can use SPR to interrogate a surface: monitor the surface and you can “see” the surface changing when stuff is sticking to it. If you have something with specific binding properties on that surface, like an antibody (as is used in an ELISA), with some additional effort you can maybe have an assay that detects something binding to that antibody.
