Artificial spider silk spun from microfluidic device

The artificial silk gland was able to recreate the complex molecular structure of silk by mimicking chemical and physical changes that naturally occur in a spider’s silk gland.

The team, led by Keiji Numata at the RIKEN Center for Sustainable Resource Science and colleagues from the RIKEN Pioneering Research Cluster, has published its findings in Nature Communications.

Numerous attempts have been made to replicate spider silk to exploit its properties, such as tensile strength comparable to steel of the same diameter, unparalleled strength-to-weight ratio, biocompatibility and biodegradability.

Spider silk is a biopolymer fibre made from large proteins with highly repetitive sequences, called spidroins. Within the silk fibres are molecular substructures (beta sheets), which must be aligned properly for the silk fibres to have their unique mechanical properties.

In a statement, Numata said: “In this study, we attempted to mimic natural spider silk production using microfluidics, which involves the flow and manipulation of small amounts of fluids through narrow channels. Indeed, one could say that the spider’s silk gland functions as a sort of natural microfluidic device.”

The device is said to resemble a small rectangular box with tiny channels grooved into it. Precursor spidroin solution is placed at one end and then pulled towards the other end by means of negative pressure. As the spidroins flow through the microfluidic channels, they are exposed to precise changes in the chemical and physical environment, which are made possible by the design of the microfluidic system. Under the correct conditions, the proteins self-assembled into silk fibres with their characteristic complex structure.

The researchers experimented to find these correct conditions and were eventually able to optimise the interactions among the different regions of the microfluidic system. They discovered that using force to push the proteins through did not work; only when they used negative pressure to pull the spidroin solution could continuous silk fibres with the correct alignment of beta sheets be assembled.

“It was surprising how robust the microfluidic system was, once the different conditions were established and optimised,” said senior scientist Ali Malay, one of the paper’s co-authors. “Fibre assembly was spontaneous, extremely rapid, and highly reproducible. Importantly, the fibres exhibited the distinct hierarchical structure that is found in natural silk fibre.”

According to RIKEN, the ability to artificially produce silk fibres using this method could help reduce the environmentally negative impacts of textile manufacturing. The biodegradable and biocompatible nature of spider silk makes it ideal for biomedical applications, including sutures and artificial ligaments.

“Ideally, we want to have a real-world impact,” said Numata. “For this to occur, we will need to scale up our fibre-production methodology and make it a continuous process. We will also evaluate the quality of our artificial spider silk using several metrics and make further improvements from there.”