Development and analysis of chemically patterned small neuronal networks for brain-on-a-chip models

Understanding the function and components that form the brain has always been the focus of much research over countless years however, this need has become of paramount importance in the modern age due to the rise in neurological disorders associated with the aging population such as Parkinson’s disease. A fundamental issue in neurological research is the lack of knowledge of how the brain truly functions in health and disease, this is in large part due to the complexity of the brain. There are many models of the brain which have tired to improve our understanding such as rodent models but the complexity still remains. Therefore, developing a model that focuses on single neurons or small networks decreases the complexity and any insights gained from this platform could be used to benefit larger, more complex neuronal models.

This research focuses on the development of brain-on-a-chip microfluidic devices capable of isolating and monitoring the electrical activity of single neurons within a small network. To achieve this a combination of photolithography, using the positive photoresist polymer S1813 with specifically designed photomasks to generate a sacrificial template, and a 3 staged chemical patterning protocol utilising the sequential application of 3-(aminopropyl) triethoxysilane (APTES), Bromoisobutyryl Bromide (BIBB) and poly (3-sulfopropyl methacrylate potassium salt) (pKSPMA) were used to generate a platform with cell repellent regions, caused by chemical patterning, and cell promontory region in a specific pattern, generated by the removal of the sacrificial photoresist polymer. This process was tested on coverslip and utilised the SH-SY5Y neuroblastoma cell line to determine the effects of the method. Through testing it was concluded that the techniques could isolate small numbers of neurons via the formation of a hydrophilic polymer brush across the surface and that the SH-SY5Y cell line was electrophysiologically active.

The platform forming techniques were then optimised on multielectrode arrays (MEAs) to generate a platform capable of monitoring the electrophysiology of SH-SY5Ys growth within designated regions. Through the optimisation process the use of adhesive precoaters polyethyleneimine (PEI) and poly-D-lysine (PDL) was incorporated to to improve neuron adhesion thereby increasing the number of detectable spiking events caused by cultured neurons. However, interactions between the polymer brush and precoaters caused device development issues and require further work. SH-SY5Ys cultured on precoated MEAs showed the establishment of neural networks by electrode stimulation and synchronised spiking activity indicating the platform would, once optimised for the MEA platform, would be capable monitoring complex neural activity within the designated regions.