Spatially controlling neuronal adhesion and inflammatory reactions on implantable diamond

The mechanical and chemical properties of diamond and diamond-like carbon (DLC) coatings make them very suitable materials for improving the long-term performance of invasive electrode systems used in brain-computer interfaces (BCIs). We have performed in vitro testing to demonstrate methods for spatially directing neural cell growth and limiting the detrimental attachment of cells involved in the foreign body response on boron-doped diamond and DLC. Inkjet-printing, laser micro-machining, and stencil-assisted patterning techniques were used to control neuronal adhesion and modify inflammatory cell attachment. This work presents micro-tailored materials that could be used to improve the long-term quality of recorded signals from neural-electronic interfaces. © 2011 IEEE

Surface functionalisation of nanodiamonds for human neural stem cell adhesion and proliferation.

Biological systems interact with nanostructured materials on a sub-cellular level. These interactions may govern cell behaviour and the precise control of a nanomaterial's structure and surface chemistry allow for a high degree of tunability to be achieved. Cells are surrounded by an extra-cellular matrix with nano-topographical properties. Diamond based materials, and specifically nanostructured diamond has attracted much attention due to its extreme electrical and mechanical properties, chemical inertness and biocompatibility. Here the interaction of nanodiamond monolayers with human Neural Stem Cells (hNSCs) has been investigated. The effect of altering surface functionalisation of nanodiamonds on hNSC adhesion and proliferation has shown that confluent cellular attachment occurs on oxygen terminated nanodiamonds (O-NDs), but not on hydrogen terminated nanodiamonds (H-NDs). Analysis of H and O-NDs by Atomic Force Microscopy, contact angle measurements and protein adsorption suggests that differences in topography, wettability, surface charge and protein adsorption of these surfaces may underlie the difference in cellular adhesion of hNSCs reported here

Surface functionalisation of nanodiamonds for human neural stem cell adhesion and proliferation.

Biological systems interact with nanostructured materials on a sub-cellular level. These interactions may govern cell behaviour and the precise control of a nanomaterial's structure and surface chemistry allow for a high degree of tunability to be achieved. Cells are surrounded by an extra-cellular matrix with nano-topographical properties. Diamond based materials, and specifically nanostructured diamond has attracted much attention due to its extreme electrical and mechanical properties, chemical inertness and biocompatibility. Here the interaction of nanodiamond monolayers with human Neural Stem Cells (hNSCs) has been investigated. The effect of altering surface functionalisation of nanodiamonds on hNSC adhesion and proliferation has shown that confluent cellular attachment occurs on oxygen terminated nanodiamonds (O-NDs), but not on hydrogen terminated nanodiamonds (H-NDs). Analysis of H and O-NDs by Atomic Force Microscopy, contact angle measurements and protein adsorption suggests that differences in topography, wettability, surface charge and protein adsorption of these surfaces may underlie the difference in cellular adhesion of hNSCs reported here

Diamond for stem cell biotechnology

The recent rise in life expectancy has led an increase in the number of cases of neurological diseases such as Alzheimer’s, Parkinson’s and macular degeneration. Traditional therapeutic approaches are ineffective as regeneration is limited in the Central Nervous System (CNS). Neural prosthetics and stem cell therapy present exciting solutions for enabling the function of the brain to be restored. Implanted materials for neuronal prosthetics must have outstanding electrical properties whilst being inert and biocompatible. Diamond fulfils there criteria, and is the focus of this thesis. Results chapter 5 describes a novel approach to pattern diamond to 5 µm resolution, with feature widths of 2 μm. Selective seeding of nanodiamonds (NDs) was performed using a microprinting technique, which was then grown into Nanocrystalline diamond (NCD) films via Chemical Vapour Deposition (CVD) into the desired pattern. The ability to pattern diamond is not only valuable for biomaterial design, but also for photonic and microelectromechanical systems (MEMS) prototyping applications. Chapter 6 describes the quantitative investigation as to whether the inclusion of boron in NCD (BNCD) has any observable effect on biocompatibility. The effect of nanostructuring BNCD on biocompatibility was also investigated. The attachment and proliferation of human Neural Stem Cells (hNSCs) was used to assess biocompatibility. Nanostructuring of BNCD was done using a CNT scaffold resulting in a material with increased capacitance. Combining the capacitive increase, wide electrochemical window and demonstrated biocompatibility, diamond has shown to be an ideal material for interfacing with neurons. Chapter 7 describes the investigation into whether NDs support hNSC growth. hNSCs were cultured on hydrogen and oxygen functionalised NDs, and it was discovered that O–NDs promote hNSC adhesion whereas H–NDs do not. Contact angle and protein adsorption measurements were employed to investigate and hypothesise why a difference in hNSC adhesion is observed. Chapter 8 demonstrates the capacity of ND for supporting hNSC differentiation. The effect of varying ND functionalisation on differentiation was investigated, with H– and O–NDs inducing the spontaneous differentiation of hNSCs into neurons. Complimenting results obtained in Chapter 7, O–NDs were best at supporting adhesion and promoting neurite outgrowth

Development of Functionalised Carbon Based Substrates for Neuronal Cell Culture and Production of Carbon Nanoparticles for Bioimaging Applications

The desire to create an idealised substrate for the growth of neural based cells has been a research ambition for many years. Neural based cells are notoriously difficult to culture, normally requiring the creation of a specially prepared substrate to allow for their attachment, growth and differentiation. Although polylysine serves as an adequate functional treatment for this purpose in vitro its associated cytotoxicity present difficulties for in vivo applications. Although progress has been made in recent years with regards to the initial development of brain computer interfaces (BCIs) and the bionic eye research in the field could be significantly accelerated through the development of novel successful neurocompatible substrates. It is envisaged that the utilisation of amine-functionalised nanodiamond or diamond-like carbon may fulfill this role due to the ability for diamond surfaces to be neurocompatible, mechanically strong, readily applied as a surface coating, highly stable and easily functionalised. Additionally, there also exists demand for the creation of nanoparticles to act as bioimaging agents which possess the fluorescence capabilities of quantum dots without the associated cytotoxicity issues. Research progression has unveiled that carbon nanoparticles produced swiftly and in large quantities, from the pyrolysis of carbohydrates, may eclipse quantum dots due to their superior biocompatibility, excellent fluorescence emission levels, environmentally friendly synthesis methods and lack of photobleaching. This area of research is still rapidly expanding, with many carbonaceous compounds still awaiting investigation for their potential as creating carbon nanoparticles (CNP) favourable for bioimaging purposes. It is envisaged the key to creating successfully fluorescent CNPs which can be translocated within cells boils down to a number of factors, including surface functionality, CNP diameter, and carbon source. One of the aims of this thesis was to investigate the suitability of amine-functionalised nanodiamond and diamond-like carbon derived substrates for the culture of neuronal cell lines and primary neural cells and also to investigate their effectiveness in comparison to conventional polylysine functionalised surfaces. These novel substrates were illustrated to support neural cells as effectively as conventional polylysine surfaces with cells displaying numerous neuritis of up to 300 µm in length. Furthermore, primary cells were supported on the functionalised substrates for up to three weeks without any indication of apoptosis or cell detachment and cell viability assays indicated no deviation in activity from cells cultured on functionalised and control samples. In addition, a further aim was to identify the suitability of CNPs derived from multiple saccharide sources (i.e. glucose, sucrose and alginate) as potential bioimaging replacements for presently used quantum dots / fluorescent dyes which are unfortunately subject to photobleaching or cytotoxicity issues. Those CNPs derived purely from either glucose, sucrose or alginate were shown to have luminescence capabilities similar to conventional fluorescent tags, clearly allowing for the morphology of the cells tested to be recorded after cells were exposed to the CNPs for a 2 hour period. This luminescence was shown to still be visually detectable three years post CNP synthesis and the particles were shown to have no significant effect upon cell viability illustrating their widespread potential within scientific research