About the group
The Bioimaging and Bioanalysis group has been founded in Feb. 2014. We are an interdisciplinary group consisting of biologists, biomedical engineers, chemists and physicists. Our main goal is to pioneer nanoscale magnetic resonance imaging in the nanoscale.
Our main goal
Diamond magnetometry allows reading out a magnetic resonance signals in the nanoscale. The method is based on a fluorescent defect in diamond which changes its optical properties based on its magnetic surrounding. Thus it combines the advantages of both magnetic resonance imaging (functional contrast, spectral information) and fluorescence imaging (sensitive, high spatial resolution, easy, inexpensive). This is so sensitive that it allows the detection of single electron spins 1 or even a few nuclear spins 2. Our aim is to apply this method to visualize, search and job free radical metabolism (an indicator for stress in cells) inside living cells. On the way to achieve this goal we have answered several fundamental questions, which are introduced below.
The Shape and crystallographic orientation of nanodiamonds
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.
Aggregation of Nanodiamonds in cell media3
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.
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?
Some cells as macrophages or Hela cells spontaneously ingest particles4. 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 uptake6. 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 wall7.
How do nanodiamonds interact with cells and bacteria
While essentially no cytotoxicity for mammalian cells8 has been reported for nanodiamonds we did find surprising killing effects on bacteria9. 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% killing for one type of medium we see no killing at all in a different medium. This study suggests that one needs to be very careful when comparing nanoparticle toxicities.
Selected recent articles about this topic
- Nitrogen-Vacancy Centers in Diamond: Nanoscale Sensors for Physics and Biology, R. Schirhagl, K. Chang, M. Loretz, C. L. Degen, Annual Reviews of Physical Chemistry 65 (2014) 83-105 [link]
- Improving surface and defect center chemistry of fluorescent nanodiamonds for imaging purposes - a review. Nagl, A., S. R. Hemelaar, R. Schirhagl. Analytical and bioanalytical chemistry 407.25 (2015): 7521-7536 [link]
- van der Laan, K., Hasani, M., Zheng, T. and Schirhagl, R., 2018. Nanodiamonds for in vivo applications. Small, 14(19), p.1703838 [link]
- M.S. Grinolds, et al. 2013. Nat. Phys. 9:215-219
- H.J. Mamin, et al. 2013. Science 339:557-560
- Hemelaar, S. R., et al. "The interaction of fluorescent nanodiamond probes with cellular media." Microchimica Acta 184.4 (2017): 1001-1009
- Hemelaar, S. R., et al. "Nanodiamonds as multi-purpose labels for microscopy." Scientific Reports 7 (2017)
- Garming, Mathijs WH, I. Gerward C. Weppelman, Pascal De Boer, Felipe Perona Martínez, Romana Schirhagl, Jacob P. Hoogenboom, and Robert J. Moerland. "Nanoparticle discrimination based on wavelength and lifetime-multiplexed cathodoluminescence microscopy." Nanoscale 9, no. 34 (2017): 12727-12734
- T. Zheng, F. Perona Martinez, I. M. Storm, W. Rombouts, J. Sprakel, R. Schirhagl, R. de Vries, Recombinant protein polymers for colloidal stabilization and improvement of cellular uptake of diamond nanosensors. Analytical Chemistry. 89, 23, p. 12812-12820 9 p (2017)
- Hemelaar, Simon R., Kiran J. van der Laan, Sophie R. Hinterding, Manon V. Koot, Else Ellermann, Felipe P. Perona-Martinez, David Roig et al. "Generally Applicable Transformation Protocols for Fluorescent Nanodiamond Internalization into Cells." Scientific Reports 7 (2017)
- Hemelaar, S.R., Saspaanithy, B., L’Hommelet, S.R., Perona Martinez, F.P., van der Laan, K.J. and Schirhagl, R., 2018. The Response of HeLa Cells to Fluorescent NanoDiamond Uptake. Sensors, 18(2), p.355 (2018)
- Ong, S.Y., van Harmelen, R.J., Norouzi, N., Offens, F., Venema, I.M., Najafi, M.H. and Schirhagl, R., 2018. Interaction of nanodiamonds with bacteria. Nanoscale, 10(36), pp.17117-17124