Nanodiamonds and adaptive optics for deep tissue super-resolution microscopy

Diamond presents much promise for biological applications, its stability means it is biocompatible and does not photobleach, unlike most dyes. Nanoscale sized particles of diamond have been shown to be small enough to allow endocytosis. Furthermore, the presence of optically active defects in the diamond structure, such as the nitrogen-vacancy (NV) defect, allow optical addressing of individual nanodiamonds. There is much interest in using the NV centre as a nanoscale sensor for biologically generated electromagnetic fields. We are developing a superresolution microscope to allow the characterisation of the optical properties of nanodiamond in living tissue, such as the sensitivity of the optically active defects to small electromagnetic fields. We will also explore the more general use of diamond as an in-vivo fluorescent marker.
Our microscope is an adaptive optics enhanced, stimulated emission depletion (STED) microscope. Multi-colour excitation means that it is not only suitable for nanodiamonds, but can also simultaneously image a number of the other more conventional fluorophores, including STED-compatible near-infrared dyes such as ATTO 647N and Abberior Star 635. We are incorporating adaptive optics elements, such as a deformable mirror and a spatial light modulator, to correct for the sample-induced optical aberrations that are inevitable when imaging biological samples. While unavoidably adding complexity to the microscope hardware, it has repeatedly been demonstrated that such correction techniques allow high quality images from deep in the tissue of biological samples without the need for additional refractive index matching protocols.
Our microscope is currently under development and this presentation will demonstrate the state of play of the instrument, including the effect of the adaptive optics on conventional confocal imaging and on the integration of the STED-enabling components into the system. We will also present our most up-to-date work on developing nanodiamonds as fluorescent labels for biological samples.