Periodic Reporting for period 1 - iNano (Inverted core/shell Nanocrystals: the future Nanomaterial for the Visualization of Neuron activity)
Período documentado: 2019-07-01 hasta 2021-06-30
For in vivo imaging or image-guided surgery, there is an increasing interest in nanomaterials emitting above 750 nm. Furthermore, NCs possess an enhanced sensitivity to external electronic fields, which makes them attractive tools to explore the vast network and communication pathways of neuron cells in the brain. Currently used technologies to study the brain like electrode-based techniques or voltage-sensitive dyes (VSDs) have several shortcomings as they are not scalable, have slow kinetics, have a limited dynamic range, and can interfere with the membrane capacitance. NCs have shown in the past to outperform VSDs in terms of (PL) intensity changes in the presence of an electronic field. By changing the NC shape from spherical a rod-shaped the sensitivity even becomes stronger. However, up to now, there exists no single report of the synthesis of InP NCs with an anisotropic shape.
The iNano project aimed to develop a new synthesis approach for the preparation of spherical and rod-shaped InP-based NCs and thus responding to the challenges currently faced in the synthesis of InP NCs. A key feature is the use of magic-sized clusters (MSCs) as a seed and epitaxially grow an InP shell around this seed. Thereby the thickness of the InP shell allows to control the PL emission wavelength and potentially enables to reach an emission beyond 750 nm. Furthermore, depending on the crystal structure of the MSCs, the InP shell growth direction should be possible to control yielding either spherical or more elongated, rod-shaped NCs. These nanomaterials should be then explored for their potential as a new tool for neuroscientists to measure and activate the action potential of neuron cells.
Although the preparation of NCs in organic solvents has been shown to result in high-quality optical properties, they need to be rendered water-dispersible for use in biological applications. For these applications, a small size of the NCs is preferred, which can be achieved by the exchange of organic ligands on the NC surface with ligands that enable water dispersibility. In this project, the influence of different organic molecules possessing one, two, or three sulphur groups on the stability and optical properties of NCs after ligand exchange was investigated. The hypothesis that a higher number of sulphur groups per molecule tightly binding to the ZnS outer shell results in more stable water dispersible NCs could be proven and the optical properties were similar to monodentate ligands. The last part of the project, focusing on the interaction of the NCs with neuron cells and evaluating their potential to stimulate and measure the action potential, is still ongoing. Due to the unforeseeable impact of the Corona pandemic situation, it could not be finished within the time frame of the project. The here obtained results were disseminated at conferences and publications are in preparation.