Q&A with Prof Peter Gardner - MSG Online Seminar Series - July 2020

Post date: Jul 31, 2020 7:16:3 PM

For our July blog entry we have decided to dedicate a section to the questions that were not answered due to time constraints during our Inaugural Online Seminar - July 2020.

Prof Peter Gardner has kindly provided the answers to the questions directed to them concerning their talk on

‘Full spectrum optical photothermal infrared with concomitant Raman spectroscopy: A new tool for single cell analysis’

Question 1:

Please can you tell us the pulse rate of the lasers? Could the photothermal effect be evaporating the water?

Prof Peter Gardner:

The IR laser repetition rate was set at ca. 110 kHz at 300 ns per pulse. We do not think that the water is evaporating off. We are able to run for quite long periods of time, many hours and see no change at the powers and the duty cycles used.

Question 2:

What are the advantages of this technique over single cell mass spec?

Prof Peter Gardner:

This is a good question: Mass spectra are very information rich and molecular information can be obtained. However, single cell mass spec imaging at sub cellular resolution (~0.5 micron) requires a ToF-SIMS type instrument to get subcellular resolution. This requires the cells to be dry and in a vacuum so there is a significant amount of sample preparation and perturbation to the cell. To my knowledge ambient mass spec instrument have a resolution of ~50 micron so can’t get subcellular information. So the advantage of the OPTIR Raman is that it is non-destructive, easy sample preparation, can be done in aqueous environment.

Question 3:

Is a biological cell active for Raman spectroscopy?

Prof Peter Gardner:

I am not sure I understand this question. If you mean can a biological cells stay active while being analysed with Raman spectroscopy (or O-PTIR) the answer is yes. The cells remain metabolically active. You do have to keep an eye on the power and it is possible to damage the cells so but it is possible to keep cells alive and active during the analysis.

Question 4:

Can this technology be used for some sort of quantitative studies?

Prof Peter Gardner:

Yes but it depends on the system under study. For non-biological sample this is not a problem but for biological samples we are still learning how best to use the instrument and we do not yet have enough examples to see how quantitative it is. This is a work in progress.