Publications

Below you can find a selection of highlighted publications of our group. A full publication list can be found here: 

https://www.rug.nl/staff/r.schirhagl/research/publications.html

Recent review articles about diamond magnetometry can be found here:

📓 Magnetometry in general

📓 Chemical properties

📓 Magnetometry in cells

📓 Magnetometry in organisms

The Shape and crystallographic orientation of nanodiamonds

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While many researchers have assumed a spherical (or somewhat more isotropic) shape for fluorescent nanodiamonds, we found that they are actually more flake like. In addition, we could show that they have a preferred crystal orientation. This finding has important consequences on the sensing performance as well as chemical and biological properties.

How to get nanodiamond into cells?

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While essentially no cytotoxicity for mammalian cells has been reported for nanodiamonds we did find surprising killing effects on bacteria. However, the effect is not that simple. The effect strongly depends on the medium as well as on the bacteria type. While we see 90% reduction of colony count for one type of medium we see reduction at all in a different medium. This study suggests that one needs to be very careful when using this for comparing nanoparticle toxicities. Later we found that this is due to bacterial aggregation rather than toxicity.

Aggregation of Nanodiamonds in cell media

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We found that nanodiamonds aggregate severely in presence of cellular media. We identified proteins and salts, which are involved in this process. Finally, we also suggest a very simple process of reversing the order of mixing medium components with diamonds to avoid this problem.

Nanodiamond Relaxometry-Based Detection of Free-Radicals from Chemical Reactions in Biologically Relevant Conditions

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Relaxometry is a powerful tool for determining the free radical concentration in biological samples. Here we optimise the protocol and provide calibration measurements which allow us to translate a T1 response into a radical concentration.

Nanodiamonds as labels for integrated microscopy

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Integrated microscopy combines electron microscopy (EM) with light microscopy. However, conventional dyes bleach during the sample preparation for EM. NV centers in diamond, however, are protected within the lattice and thus remain fluorescent. As a result one can at the same time label cells optically and investigate the membrane structure. We can learn from this were diamond particles are within cells.

How to get nanodiamond into cells?

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Some cells as macrophages or Hela cells spontaneously ingest particles. However, most cells do not behave this way and require a different approach. One example is applying a (positively charged) protein coating which prevents aggregation but also facilitates uptake. Entering the cell becomes even trickier for microorganisms with a thick cell wall. Here we have adapted transformation protocols from gene transfection. Using these we have achieved uptake even into yeast cells with a thick cell wall.