Peripheral nerve injury is a common yet difficult-to-repair neurological disorder that often leads to sensory and motor dysfunction, severely affecting daily activities and functional recovery. For long-gap nerve defects, clinical treatment still mainly relies on autologous or allogeneic nerve grafts, but autografting remains limited by restricted donor availability, donor-site morbidity, and mismatches in tissue size and structure. In recent years, nerve guidance conduits have emerged as an important tissue-engineering strategy because they can provide directional support for axonal regeneration and offer a potential alternative to conventional grafting. However, most existing artificial conduits simply reproduce a regular tubular shape and struggle to accommodate the variable diameters and irregular geometries of native nerves, which limits their ability to achieve conformal contact with nerve tissue. "At the same time, these conduits still typically require microsuturing for fixation, making the procedure technically demanding and potentially introducing additional risks such as inflammation, fibrosis, scar formation, and axonal misdirection." said the author Xiaolei Guo, a researcher at Sichuan University, "As a result, there is growing interest in nerve conduits that can achieve adaptive wrapping, stable attachment, and reduced dependence on suturing for peripheral nerve repair."
Inspired by the water-induced closing behavior of pinecone scales, this work developed a peripheral nerve repair conduit that can autonomously curl in an aqueous environment and simultaneously achieve adhesive fixation. The researchers first combined hydrophilic γ-polyglutamic acid (PGA) with hydrophobic polyurethane (PU), and used rapid drying to create a film with asymmetric hydrophilic–hydrophobic distribution across its two sides, allowing the material to curl spontaneously into a tubular structure through differential swelling upon water exposure. A PU adhesive layer was then introduced onto the film surface to provide stable attachment, enabling adaptive wrapping of severed nerve tissue without suturing. On this basis, the study systematically evaluated curling dynamics, the effects of film thickness and component ratio on shape transformation, adhesive performance, and the ability to conform to tubular structures of different diameters. The biological performance of the material was further assessed through Schwann-cell compatibility and migration assays as well as macrophage polarization analysis, and its repair efficacy was finally tested in a rat 8-mm sciatic nerve defect model by comparing the self-curling adhesive conduit with a standard PU conduit, an autograft group, and an untreated control group.
This pinecone-inspired self-curling adhesive conduit showed clear advantages in both material performance and nerve repair efficacy. Among the tested formulations, PU/PGA10 achieved the fastest curling speed and the highest bending curvature, allowing it to rapidly roll into a tubular structure in physiological saline, while its adhesive layer provided stable fixation and enabled conformal wrapping around tubular structures with diameters ranging from 3 to 10 mm. At the same time, the material demonstrated good biocompatibility, with no obvious adverse effect on Schwann-cell viability, while more effectively promoting cell migration and creating a more favorable repair microenvironment. This was reflected by reduced inflammatory signaling and enhanced polarization of macrophages toward the pro-repair M2 phenotype in both in vitro and in vivo evaluations. In the rat 8-mm sciatic nerve defect model, the self-curling adhesive conduit outperformed the standard PU conduit, supporting stronger nerve bridging and better motor recovery, and approached the autograft group across multiple indicators, including axon diameter, myelin thickness, regenerated nerve marker expression, vascularization, and improvement of muscle atrophy. These results highlight its combination of surgical convenience and strong regenerative potential for peripheral nerve repair.
This work offers a peripheral nerve repair strategy that is more aligned with practical surgical needs by combining bioinspired shape transformation with tissue adhesion, allowing the conduit to autonomously curl, conform, and fix onto severed nerves in an aqueous environment. In doing so, it reduces dependence on microsuturing and provides a simpler solution for nerve repair in situations involving irregular tissue dimensions or limited operating space. More importantly, the design does not only address how to secure the conduit, but also improves the regenerative microenvironment through its material composition and biological effects, enabling clearly better repair outcomes than a standard PU conduit and bringing performance closer to that of autografting. Its value lies not only in introducing a new type of nerve conduit, but also in demonstrating how stimuli-responsive materials can be integrated into nerve repair, opening a new direction for suture-free and adaptive tissue-repair devices. At the same time, there is still room to improve the precise control of curling dynamics and curvature. "In the future, we will combine structural design, simulation analysis, and more application verification to further promote the development of these materials towards a more controllable, customized, and clinically applicable direction." said Xiaolei Guo.
Authors of the paper include Xiaolei Guo, Jinwei Li, Hongyu Xu, Shengrong Long, Junhong Li, Ao Wang, Wenkai Liu, Fan Zhang, Zhen Li, Feng Luo, Jiehua Li, Yanchao Wang, Hong Tan, and Ting Lan.
This work was supported by the National Natural Science Foundation of China (52433015, 52373296, 52473138, and 52173287), the State Key Laboratory of Polymer Materials Engineering (sklpme2022-2-07), and the Outstanding Youth Foundation of Sichuan Cancer Hospital & Institute (Grant no. YB2025004).
The paper, "Pinecone-Inspired Water-Responsive Curling Adhesive Conduit for Peripheral Nerve Repair" was published in the journal Cyborg and Bionic Systems on Mar 27, 2026, at https://doi.org/10.34133/cbsystems.0556.
