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I just got interesting questions from a QNM user:
1. As you mentioned, DMT modulus is not suitable for cells, so could you please show me the use of using PFQNM for live cells?
Even though DMT is not the best model, it will give you a half quantitative image in the YM channel (and it will be qualitative anyway). For ALL other channels, the fact that you have DMT or not doesn’t matter at all (for instance, the deformation is totally independent form the contat model). So all other channels are 100% quantitative. And again, if you use HSDC files, you can chose the model you want and then you will be 100% on the YM too.
2. Or how can we map the mechanical properties of cells through Catalyst? Can only use force mapping, or HSDC or point and shoot to get some force curves of interested areas?
I suggest cone, not pyramid. I saw cone angles from 12 to 35 deg. This is not so critical but if I had the choice, I would go for large cone angles but again this depends on the model you chose: Sneddon suggest an infinite cone… And remember the gold rule for QNM imaging on cells: first optimize the setpoint. Then work on the gain. If you do it backwards, you won't be quantitative! Good luck. Alex.
I suggest cone, not pyramid. I saw cone angles from 12 to 35 deg. This is not so critical but if I had the choice, I would go for large cone angles but again this depends on the model you chose: Sneddon suggest an infinite cone…
And remember the gold rule for QNM imaging on cells: first optimize the setpoint. Then work on the gain. If you do it backwards, you won't be quantitative!
Good luck.
Alex.
I also got an interesting question from a user: for QNM working properly, we suggest to have a minimum indentation/deformation of 2nm (sometimes ppl misunderstand it as the best indentation for QNM to work), but whether should it have a upper limit? Especially on cells, if indentation is 10s or 100s nm, will the model still fit? Anyone wanna comment on this?
Hi Ang,
Sorry for the delay in my answer... Yes I think you are absolutely right. As the measured values strongly depends on the indentation depth, there should definitely be an upper limit not to be overtaken. It of course depends on the sample's compliance. For cells, generally speaking, the indentation is always superior to 50 nm, up to let's say 200 nm under the condition that the setpoint is set properly. In that case for most of the tested cell types I found Young's modulus values right in the expected range. But for really soft cells (< 10 kPa or even <1 kPa), this might not work. I will try to check with my sources if an upper limit can be defined for cells. If I find that, I will come back to you.
Best,