CVD DIAMOND AS A SUBSTRATE FOR BIOLOGICAL CELL GROWTH - TOWARDS DIRECT BRAIN-COMPUTER INTERFACES

Controlling electronic devices using thought-processes may until recently have been in the domain of science-fiction. But brain-computer interface (BCI) research is showing that neural implants may allow computers, electronic equipment, or other mechanical devices to be controlled by thought alone. One of the limiting factors in the development of BCI technology is inflammatory tissue response, which can severely reduce the longevity of the implant. A solution to this problem may be to use bioinert materials, such as thin film diamond or diamond-like carbon (DLC) as the substrate material upon which to grow the neurons that form the biology-to-electronics interface. This is because diamond/DLC films have been shown to be bioinert, and do not produce an immune response when in contact with living cells. Moreover, their surface chemistry can be readily modified, allowing the adhesion properties of different cell types to be tailored for specific requirements. These materials can be doped to change their conductivity allowing electrical signals to pass between the diamond and attached neurons.
The technological, medical, social, and even military implications for this are obvious. In the medical field, BCI holds out the promise of 'cures' for a variety of ailments. For example, amputees or people paralysed due to a damaged spinal cord may be fitted with a BCI implant which would be used to control a pair of robotic legs/arms via a BCI, enabling the patient to walk and function as normal. Recent advances such as the 'Braingate' project, the artificial cochlea and 'bionic' eye projects have demonstrated that technology similar to this may be feasible within a decade. The next step would be to link the BCI to a radio-link, allowing a person fitted with a diamond-based BCI implant to control remote machinery, all by simply thinking about it.
Although there are many different problems to be solved before reliable BCIs can be achieved for commercial applications, the aim of this proposed project is to underpin the first steps towards realising such BCI devices - i.e. studying the interface between the living biological cells (stem cells and neurons) and inorganic diamond electronics. Rather than use rat/mice neurons, as in previous studies, we intend to use neurons derived from human stem cells, which ensures that the results of this study are relevant to human BCIs. Stem cells are special types of cells that can easily be converted into a specific type of neuron (or any other type of cell) depending on the method of tissue culture and the constituents of the culture media. The stem cells will be grown on different diamond & DLC surfaces, and the factors which govern their survival identified and optimised. These factors include such things as whether the surface is oxidised or not, its roughness, doping level, etc. The stem cells will then be treated with suitable chemically defined media (CDM), which over the course of several cell divisions causes the daughter cells to turn into neurons. We wish to investigate the affect of the different surfaces on the ability of the stem cells to turn into neurons. The aim is to optimise the processing conditions and substrate preparation to allow both these cell types to be cultured in the laboratory, and to allow them to survive for many weeks. The network of neurons produced on the diamond surface in this way can be stimulated electrically via signals through the conducting substrate. The ultimate aim is to send signals from the diamond/DLC substrate into a neuron, and back again where it is recorded. This would demonstrate two-way signal processing between the diamond/DLC electronics and the neuron. Prepatterning the diamond/DLC surface with lasers will allow the neurons to grow along predefined 'roadways', allowing designed neural nets to be made. Stimulating these networks using different electrical impulses provides a route to modelling the behaviour of the human brain.

The project focuses upon two types of cells (embryonic stem cells and neurons), since these may have the most immediate and widespread impact for society and medical science.

The first aim of the project will be to develop and optimise a set of parameters which allow the two types of cell to be cultured and survive for the longest duration, using different types of inert synthetic diamond & diamondlike carbon (DLC) substrates. The ready availability of such stem cells should greatly increase the research capability of medical groups trying to find cures for many of today's most pernicious ailments, including cancer, Parkinson's disease, MS, and may allow repair of nerve damage or spinal-cord injuries. Research using these stored cells may even allow damaged organs, limbs, or other body parts to be regrown, either in situ or in the lab and then grafted on using an operation, as has recently been demonstrated with an artificial trachea. Curing these diseases, or regrowing damaged organs, would not only restore the quality of life to the individual, but would also remove them from chronic treatment regimes that are extremely costly to the NHS and place that person back onto the job-market where they could again make a full contribution to society.

The secondary aim of this project is to convert the stem cells into neurons, which will grow to form fully functioning neural networks on the chosen substrate. The research will explore the interface between the biological cells and inorganic electronic materials, making it a stepping-stone towards brain-computer interfaces (BCI). Unlike current implants which provoke an inflammatory or immune response from the body, diamond/DLC-based or diamond-coated implants are bioinert, and thus have a greatly extended lifetime in the body. This would remove the need for costly and painful replacement operations since one implant should work for the lifetime of the patient. As well as the multitude of benefits BCIs could provide for the ordinary person, they also promise 'cures' for spinal injury, degenerative disorders, cerebral palsy and many other neuromuscular disorders. For example, a patient paralysed due to a damaged spinal cord may be fitted with a BCI implant which would be used to control a pair of robotic legs via a computer interface, enabling the patient to walk as normal.

Apart from the obvious benefits in quality of life for individuals and society that should result from the improvements in BCI implants, the technology and infrastructure surrounding these devices would also have a significant wealth-creating effect. Taking just one example of the BCI-controlled artificial legs: a materials company would be required to make the diamond-based BCI, an engineering company to fabricate the artificial legs, a software company to program the BCI to drive the legs, and medical staff to train the patient how to use them. There would be opportunities here for UK based spin-off companies in all these areas. There are also obvious military applications for such technology, both from the viewpoint of helping injured soldiers as well as BCI-controlled drones, tanks or weaponry.

The third aim of the project arises from the ability to direct neuronal growth along patterned pathways and form synaptic connections at predefined junctions, since may allow artificial 'designer' neural networks to be fabricated. Such a network would act as a simplified analogand would allow neuroscientists an unprecedented opportunity to observe how small neural nets operate. Extrapolations from these will enable neuroscientists to gain a far greater insight into the complex workings of the human brain than hitherto possible. Such understanding would have far-reaching implications for the design of artificial intelligence (providing lucrative opportunities for the UK computer programming and IT industries) or for developing drugs for treatment of mental illness (benefiting the UK pharmaceutical industry).