Directional axonal growth in a microfluidic device with nanotopography

Axons play a major role in the transmission of neuronal signals along the central nervous system. Dysfunction or degeneration of these neurons is seen in many neurodegenerative diseases as well as spinal cord injuries for many of which no cure has been found yet. This calls for the development of advanced engineering solutions capable of better in vitro modeling axons for gaining a better understanding of axonal function. Microfluidics technology is an ideal candidate for this purpose due to its unique feature for mimicking the natural habitat of the cells as well as offering real-time monitoring of the culture.

In this regard, a research group in Finland has developed a microfluidic chip to study the directional growth of human neuronal axons derived from human pluripotent stem cells (hPSCs) the results of which are published in the journal of advanced interfaces.  

“Here, a polydimethylsiloxane (PDMS) microfluidic chip integrated with a light patterned substrate is utilized to achieve both isolated and unidirectional axonal growth of hPSC-derived neurons. The isolation of axons from somas and dendrites and robust axonal outgrowth to adjacent, axonal compartment, is achieved by optimized cross-sectional area and length of PDMS microtunnels in the microfluidic device.”, the authors explained.

The proposed microfluidic chip for isolation of axons from somas and directional axonal growth was microfabricated from PDMS and consisted of a seeding microchamber in which the cells were grown connected to 15 microchannels. The axons would penetrate through the microchannels during the growth. These microfluidic channels were connected to an outlet port to complete the diffusion of staining reagents and remove the waste. 

Microchannels can guide the axons and promote controlled directional growth. The microfluidic channel dimensions can impact the growth of the axons and were thus optimized in this study for robust isolation of axons of hPSC-derived neurons. The surface of the microfluidic chips was functionalized with a photo-responsive material containing the azobenzene. The surface of the microchannel could reversibly change in response to the light irradiation and thus could be used for modulating the axonal growth and alignment in the desired direction. 

“In this study, we showed that successful isolation of axons from somas and dendrites combined with the robust axonal outgrowth of hPSC-derived and rat primary cortical neurons in a compartmentalized microfluidic PDMS device is greatly influenced by the cross-sectional area and the length of the separating microtunnels. Furthermore, we created an hPSC-derived neuron-based axonal model consisting of a compartmentalized PDMS microtunnel chip integrated with photoinscribed nanotopography on light-responsive, azobenzene-based molecular glass.”, the authors concluded.

Read the original article: Directional Growth of Human Neuronal Axons in a Microfluidic Device with Nanotopography on Azobenzene‐Based Material