A research team at Xi'an Jiaotong University has developed a new method to bioprint living muscle tissue with cells that align in the same way as natural human muscle. Their findings, published in the International Journal of Extreme Manufacturing, address a key challenge in regenerative medicine: creating muscle tissues that not only look like real muscle but also have the correct internal structure.
Muscle strength and function depend on myofibers being aligned in specific directions, which vary between different muscles. While existing tissue-engineering methods can encourage some cell alignment, they are typically limited to flat or simple structures. Bioprinting allows for more complex three-dimensional shapes, but until now, it has struggled to produce organized cellular arrangements within those shapes.
The team used electrohydrodynamic (EHD) bioprinting, a process where electric fields pull out fine jets of bioink rather than simply extruding material through a nozzle. They redesigned the bioink by combining alginate—a common printable gel—with fibrin, a protein involved in blood clotting and wound healing. Fibrin is sensitive to electric fields; when subjected to high voltage during printing, it reorganizes into long nanofibers that guide embedded cells into alignment.
This reorganization happens at what researchers call the Taylor cone stage, under about 3,000 volts. The aligned fibrin fibers act as tracks for cells inside the gel, helping them orient themselves correctly.
"As the material aligns, the cells follow," said Ayiguli Kasimu, doctoral researcher and first author of the study. "The electric field is effectively building a road system at the nanoscale, and the cells naturally grow along it."
By changing how they moved the printer nozzle during EHD bioprinting, researchers could create tissues with straight fibers or more complex curved or circular patterns—mimicking real muscle architectures.
To enhance functionality further, conductive polymers were added to make printed tissues capable of transmitting electrical signals needed for muscle contraction. "Muscle tissue relies on electrical signals to coordinate contraction, and the conductive additives allowed the printed constructs to transmit these signals," explained Assistant Prof. Zijie Meng of Xi'an Jiaotong University.
When implanted into animal models with muscle defects, these printed tissues promoted new muscle formation and improved functional recovery by supporting better fusion of cells into mature fibers and stronger expression of muscle proteins.
The study also suggests broader applications for using electric fields in shaping living matter during bioprinting processes. The authors note that while their results are promising for future regenerative medicine efforts—including potential use with other organs—further work is required to fully understand how fibrin responds at a molecular level and optimize materials for long-term performance.
By using electric fields as design tools inside bioinks during printing, this approach may help close gaps between engineered tissues’ appearance and their biological function.
