Epoxy-functionalized sensor surface for Biacore x100

Hello everyone,

I am attempting to couple a small molecule to a sensor chip for use in a Biacore x100 system.  This small molecule has a primary amine tag I have added to enable immobilization.  Unfortunately due to inductive effects this amine does not react well with NHS esters.  I have been able to successfully couple this molecule to an epoxy-functionalized resin in basic conditions.  My coupling solution (33% acetonitrile, 67% carbonate buffer pH 10.25) is compatible for a short-term coupling step, however the reaction is typically run overnight and I do not want to damage the chip/machine.

I have found two third-party suppliers (Xantec, Sofchip) who offer epoxy-functionalized gold sensors for SPR.  These sensors are sold as standalone products, meaning I would have to remove the gold layer from an existing chip and then attach the new, epoxy-functionalized sensor separately.  This might be an advantage for me, as I could couple my molecule to the epoxy-gold surface overnight prior to placing it on the chip.  However I have never done this before and am a bit nervous about wasting valuable reagents and/or damaging the machine.

I would greatly appreciate any advice on the following topics:

1. What are the dimensions of the gold sensor on a standard (not series S) Biacore chip?  The suppliers offer several different sizes (9x9x0.3mm, 12x12x0.9mm, etc.), and I am not sure which one is the right size.
   
2. How can I best perform the coupling without damaging the other parts of the gold sensor?  (E.g. can I place the entire sensor in my coupling solution, or should I attempt to place a droplet of solution on top of the gold layer only?)
   
3. How exactly do I remove the old gold surface and attach the new one?  The instructions on the third-party supplier sites are vague and do not have images.  I understand that the Sensor Chip Au kit includes a tool for doing this, as well as a glue stamp, however I have not been able to find a copy of this kit's manual with step-by-step instructions or images.

Thanks very much,

ZT

Hi,
1)     The actual glass slide with gold is in Biacore 3000, X100 and T200 (series S) the same (9x9x0.3 mm). The casing however is different so that they are not compatible with each other. The glass slides offered by Xantec are compatible with a X100 instrument when you order the proper slides.
2)     As stated elsewhere it is imperative to keep the side which is docking to the optical interface as clean as possible. No immersing the whole glass sensor square. So, the droplet method in a (wet) chamber is the best option in my opinion (never done it though – anyone an example?).
3)     Why do you want to remove the gold layer because you lose the SPR-interface? Instructions at d3.cytivalifesciences.com/prod/IFU/22057521.pdf  

Kind regards
Arnoud

Hello Arnoud,

Thank you very much for your reply!  It was very helpful.  I will try the wet chamber droplet method first.

As for why I would want to remove the sensor surface, from what I can tell the Sofchip/Xantec sensors come as standalone items - that is, just a little 9x9x0.3mm gold and glass square without any mounting or microfluidics.  The Sofchip website advises removing the sensor from a used chip with a scalpel or razor and then gluing on the new one.  I think I will probably go with a Cytiva Au kit instead of hacking up an old chip, however.

This is also why I was wondering about immersion.  I want the top of the chip covered in my coupling solution, and the bottom can apparently be stuck on with a variety of different glues.  However, your point about keeping the side optical docking surface clean is well taken.  I do not think my buffer will damage this surface and the sofchip chips come in packs of three, so I may also try immersion.  I will let you know how it works out.  

Finally, I'm very glad to have that manual you sent - it's exactly what I needed.

Thanks again,

Zack