Physical cues of scaffolds promote peripheral nerve regeneration

Fabrication of piezoelectric/conductive composite nerve conduits for peripheral nerve regeneration

Due to the complex regenerative microenvironment after peripheral nerve injury (PNI), developing a piezoelectric/conductive composite nerve guidance conduit (NGC) for repairing nerve defects remains a great challenge. The conductivity and piezoelectricity have been separately demonstrated to enhance the repair of PNI, yet there is a paucity of studies investigating the synergistic effects of both functions. Herein, a piezoelectric/conductive nerve conduit composed of chitosan (CS), reduced graphene oxide (rGO), and poly-L-lactic acid (PLLA) was fabricated, which provided the conductivity, mechanical support and piezoelectricity. Tensile strength, conductivity, antibacterial activity, and cell viability of piezoelectric/conductive composite NGCs were evaluated. Piezoelectric/conductive composite NGCs exhibited electrical signal output capability and conductive performance. Moreover, rGO significantly promoted cell proliferation and adhesion. Overall, the piezoelectric/conductive CS/rGO/PLLA nerve conduit shows great promise as a potential treatment of PNI.

Sericin-Based 3D High-Precision Biomimetic Microscaffold Fabricated by Laser Direct Writing for Tissue Engineering

In tissue engineering, scaffolds are designed to mimic the extracellular matrix (ECM), creating three-dimensional (3D) microenvironments that support cell adhesion and growth. However, the precise fabrication of heterogenenous ECM-mimicking 3D microstructures remains an unsolved challenge. To address this, high-precise sericin-based scaffolds were developed via femtosecond laser direct writing (FsLDW) technology. Chemically modified sericin served as a monomer in the FsLDW process, achieving nanoscale precision and enabling the fabrication of arbitrary 3D sericin microstructures. Biomimetic 3D models, derived from natural tissue matrices, were employed to construct heterogenenous sericin bioscaffolds. These anisotropic scaffolds effectively supported cell directional growth and differentiation. This advancement greatly enhances the precision of sericin-based tissue-engineered scaffolds, enabling the creation of heterogenenous, multifunctional microenvironments that mimic natural ECM to support functional tissue development and address challenges in accurately simulating ECM microstructures in tissue regeneration.

Bioinspired Paste-Extrusion Printed Microlattices with Natural Bone-Like Porosity and Performance

The structure feature determines its performance. In the field of biological implants, microlattices are commonly used as building blocks for light-weight and adaptive purposes, which however show limitations in biological and mechanical properties as compared with natural bones. Inspired by the efficient mass transfer and high fault tolerance of biological neural networks derived from the hierarchical structure and functional gradient, a bioinspired paste-extrusion printed microlattice (BPPM) structure is developed and its tunable properties are demonstrated. The mechanical properties of non-crossing microlattice structures are first verified outweigh crossing one under equivalent compressive stress. Then, by introducing gradient components and a paste-extrusion 3D printing process, a BPPM structure with a hierarchical porosity, and gradient composites is fabricated. As a result, the BPPM shows the eliminated deformation along the gradient direction, a fine surface roughness (Sa 3.65-15.67 µm), a wide range of porosity (56-78%) and compressive strength (3.44-22.3 MPa), a favorable permeability (3.02 × 103-3.22 × 103D), and good biocompatibility and promoted cell proliferation. This work not only demonstrates the properties of BPPM in a range of natural bones but also provides a robust way to realize it.

Conjugation of PDLA onto MgO microspheres: comparison between solution grafting and melt grafting methods

Magnesium oxide (MgO) is known for its bioactivity and osteoconductivity when incorporated into biodegradable poly(lactic acid) (PLA), whereas the weak interfacial bonding between MgO microspheres (mMPs) and PLA often leads to suboptimal composite properties with uncontrollable functionality. Conjugation of mMPs with PLA may offer a good way to enhance their compatibility. In this study, we systematically investigated two grafting techniques, solution grafting (Sol) and melt grafting (Mel), to decorate poly (D-lactic acid) (PDLA) on mMPs pre-treated by prioritized hydration to obtain Sol MPs and Mel MPs, in order to optimize the grafting efficiency and improve their controllability in the properties including the crystal structure and surface morphology. Meanwhile, the Sol method showed an improved grafting ratio (2.9 times higher) compared to the Mel method. The conjugation of mMPs with PDLA effectively neutralized the rapid pH increase during the degradation of pure mMPs, which could be used for sustainable delivery of the Mg2+ ions. Moreover, the Sol MPs exhibited the lowest degradation rate constant, which could be well fitted by the first-order dynamic model, suggesting a transformation of the mMP degradation mode from bulk degradation to surface degradation. This change in the biodegradation mode was beneficial for decreasing the over-basic effect caused by the quick degradation of pure mMPs, thus extending their application in the development of PDLA/MgO composites towards tissue engineering or regenerative medicine.

Biomimetic ECM nerve guidance conduit with dynamic 3D interconnected porous network and sustained IGF-1 delivery for enhanced peripheral nerve regeneration and immune modulation

Recent advancements in tissue engineering have promoted the development of nerve guidance conduits (NGCs) that significantly enhance peripheral nerve injury treatment, improving outcomes and recovery rates. However, utilising tailored biomimetic three-dimensional (3D) topological porous structures combined with multiple bio-effect neurotrophic factors to create environments similar to neural tissues, regulate local immune responses, and develop a supportive microenvironment to promote peripheral nerve regeneration and repair poses significant challenges. Herein, a biomimetic extracellular matrix (ECM) NGC featuring an interconnected 3D porous network and sustained delivery of insulin-like growth factor-1 (IGF-1) is designed using multi-functional gelatine microcapsules (GMs). Nerve conduits made by blending chitosan (CS) with GMs demonstrate suitable degradation rates, reduced swelling rates, increased suture tensile strength, improved elongation at break, and 50 % radial compression performance that meet clinical application requirements. In vitro cytological studies indicate that biomimetic ECM NGCs exhibit good biocompatibility, promote early survival, proliferation, and remyelination potential of Schwann cells (SCs), and support neurite outgrowth. The biomimetic ECM NGCs comprising a 3D interconnected porous network in a 10-mm sciatic nerve defect rat model sustain IGF-1 delivery, promoting early infiltration of macrophages and polarisation towards M2-type macrophages. Furthermore, observations at 12 weeks post-implantation revealed improvements in electrophysiological performance, alleviation of gastrocnemius muscle atrophy, increased peripheral nerve regeneration, and motor function restoration. Thus, biomimetic ECM NGCs offer a therapeutic strategy for peripheral nerve regeneration with promising clinical applications and transformation prospects to regulate immune microenvironments, promoting SC proliferation and differentiation with nerve axon growth.