3D printed implant supports spinal cord repair

A new 3D printed implant could aid recovery after spinal cord injury by delivering electrical signals to encourage nerve cell growth.

The soft, gel-like implant includes conductive fibres that transmit electrical currents to help neurons regrow.

It was developed using materials designed to replicate the spinal cord’s natural environment, including hyaluronic acid, collagen type-IV and fibronectin—proteins naturally found in the body.

Researchers from the Royal College of Surgeons in Ireland (RCSI) University of Medicine and Health Sciences and Trinity College Dublin embedded microscopic conductive flakes, known as MXene nanosheets, into polycaprolactone (PCL) plastic fibres to form electrical channels.

Professor Fergal O’Brien of RCSI’s tissue engineering research group said: “Promoting the regrowth of neurons after spinal cord injury has been historically difficult; however our group is developing electrically conductive biomaterials that could channel electrical stimulation across the injury, helping the body to repair the damaged tissue.”

In one test, neurons cultured for seven days on high-density scaffolds with electrical stimulation grew axons averaging 108.5 micrometres, compared with 74.3 micrometres in unstimulated controls and 67.4 micrometres on unstimulated MXene-coated scaffolds.

Further experiments using neurospheres—3D clusters of neural stem cells from the olfactory bulb of mice—found longer axons and increased neuronal maturity when stimulated electrically.

Axons reached 203.6 micrometres in the high-density group, compared with 94.1 micrometres on non-conductive controls and 88.6 micrometres in the low-density group.

The spacing of conductive fibres influenced the effect of electrical stimulation.

While denser meshes improved signal transmission, a medium-density layout best supported cell growth.

The MXene content stayed below 0.3 per cent of the scaffold volume but proved highly effective when carefully positioned.

The project was supported by the Irish Rugby Football Union Charitable Trust and the Irish Research Council, and included input from an advisory group of clinicians, researchers and people with spinal injuries.

Dr Ian Woods, who co-led the project with Professor O’Brien, said: “Our regular meetings allowed for a consistent exchange of input, ideas and results.”

Though still in early stages, the implant offers a new approach to combining electrical stimulation with soft, biocompatible materials in a precisely tunable 3D printed format.

Other groups are also pursuing 3D printed implants for spinal cord repair.

Israeli firm Matricelf, using technology developed at Tel Aviv University, created a personalised implant from patients’ reprogrammed stem cells and extracellular matrix.

All mice with acute paralysis regained movement, and 80 per cent of chronically paralysed mice recovered function.

The company planned to begin human trials by late 2024.