We demonstrate fabrication of a simple microfluidic device that can be integrated with standard electrophysiology setups to expose microscale surfaces of a brain slice in a well controlled manner to different neurotransmitters.
We have demonstrated the fabrication of a two-level microfluidic device that can be easily integrated with existing electrophysiology setups. The two-level microfluidic device is fabricated using a two-step standard negative resist lithography process 1. The first level contains microchannels with inlet and outlet ports at each end. The second level contains microscale circular holes located midway of the channel length and centered along with channel width. Passive pumping method is used to pump fluids from the inlet port to the outlet port 2. The microfluidic device is integrated with off-the-shelf perfusion chambers and allows seamless integration with the electrophysiology setup. The fluids introduced at the inlet ports flow through the microchannels towards the outlet ports and also escape through the circular openings located on top of the microchannels into the bath of the perfusion. Thus the bottom surface of the brain slice placed in the perfusion chamber bath and above the microfluidic device can be exposed with different neurotransmitters. The microscale thickness of the microfluidic device and the transparent nature of the materials [glass coverslip and PDMS (polydimethylsiloxane)] used to make the microfluidic device allow microscopy of the brain slice. The microfluidic device allows modulation (both spatial and temporal) of the chemical stimuli introduced to the brain slice microenvironments.
SU-8 mold fabrication
Master preparation
PDMS solution preparation
PDMS coating and curing
Construction of the microfluidic device
Removal of PDMS sheet from master
Bonding of PDMS sheet to glass coverslip
Integration of microfluidic device and perfusion chamber
Preparation of the perfusion chamber
Bonding of microfluidic device and perfusion chamber
Exposing brain slices to neurochemical microenvironment using the microfluidic device
Existing macroscale or microscale brain slice perfusion chambers are limited in terms of the spatial resolution they provide to expose brain slices with neurotransmitters. The microfluidic device technology demonstrated here overcomes this limitation using simple bioMEMS techniques. It is anticipated that the simplicity in the fabrication of the microfluidic device and the ease in integrating it with existing electrophysiology setups will allow widespread application of the demonstrated device technology. Interesting experiments that were not possible earlier can be performed with the current microfluidic device. Different microenvironments of the brain slice can be exposed to different neurotransmitters at different time scales. The current prototype device comprises only four parallel channels and circular openings located next to each other. However, this device layout can be easily changed by implementing different designs that would have openings of different shapes or sizes, or the microchannels could be meandered in a fashion that would lead to the positioning of the openings in different microenvironments of brain slices.
The authors have nothing to disclose.
Funding was provided by NIH MH-64611 and NARSAD Young Investigator Award. The authors would also like to acknowledge Adam Beagley, Mark Dikopf, and Ben Smith for their technical assistance.
Material Name | Type | Company | Catalogue Number | Comment |
---|---|---|---|---|
RC-26GPL | Tool | Warner Instruments | W2-64-0236 | Low Profile Large Bath RC-26GLP Recording Chamber |
SHD-26GH/10 | Tool | Warner Instruments | W2-64-0253 | Stainless steel slice hold-down for RC-26G, 1.0 mm thread spacing |
PDMS (polydimethylsiloxane) | Reagent | Dow Corning | Sylgard 184 | Silicone Elastomer Kit |
Plasma Preen-II 862 | Tool | Plasmatic Systems, Inc. | Microwave plasma system | |
Model P-1 | Tool | Warner Instruments | W2-64-0277 | Series 20 Plain Platform, Model P-1 |
SA-NIK | Tool | Warner Instruments | W2-64-0291 | Adapter for Nikon Diaphot/TE200/TE2000, SA-NIK |
Oxygenated, heated ACSF (Artificial cerebro-spinal fluid) | Reagent | Exact composition will vary with application |