Peripheral nerve damage results in the loss of sensorimotor and autonomic functions, which is a significant burden to patients. Furthermore, nerve injuries greater than the limiting gap length require surgical repair. Although autografts are the preferred clinical choice, their usage is impeded by their limited availability, dimensional mismatch, and the sacrifice of another functional donor nerve. Accordingly, nerve guidance conduits, which are tubular scaffolds engineered to provide a biomimetic environment for nerve regeneration, have emerged as alternatives to autografts. Consequently, a few nerve guidance conduits have received clinical approval for the repair of short-mid nerve gaps but failed to regenerate limiting gap damage, which represents the bottleneck of this technology. Thus, it is still necessary to optimize the morphology and constituent materials of conduits. This review summarizes the recent advances in nerve conduit technology. Several manufacturing techniques and conduit designs are discussed, with emphasis on the structural improvement of simple hollow tubes, additive manufacturing techniques, and decellularized grafts. The main objective of this review is to provide a critical overview of nerve guidance conduit technology to support regeneration in long nerve defects, promote future developments, and speed up its clinical translation as a reliable alternative to autografts.

Peripheral nerve repair remains a major clinical challenge, particularly in the pursuit of therapeutic approaches that ensure adequate recovery of patient’s activity of daily living. Autografts are the gold standard in clinical practice for restoring lost sensorimotor functions nowadays. However, autografts have notable drawbacks, including dimensional mismatches and the need to sacrifice one function to restore another. Engineered nerve guidance conduits have therefore emerged as promising alternatives. While these conduits show surgical potential, their clinical use is currently limited to the repair of minor injuries, as their ability to reinnervate limiting gap lesions is still unsatisfactory. Therefore, improving patient functional recovery requires a deeper understanding of the cellular mechanisms involved in peripheral nerve regeneration and the development of therapeutic strategies that can precisely modulate these processes. Interest has grown in the use of external energy sources, such as light, ultrasound, electrical, and magnetic fields, to activate cellular pathways related to proliferation, differentiation, and migration. Recent research has explored combining these energy sources with tailored nanostructured materials as nanotransducers to enhance selectivity towards the target cells. This review aims to present the recent findings on this innovative strategy, discussing its potential to support nerve regeneration and its viability as an alternative to autologous transplantation.

Peripheral neural interfaces facilitate bidirectional communication between the nervous system and external devices, enabling precise control for prosthetic limbs, sensory feedback systems, and therapeutic interventions in the field of Bioelectronic Medicine. Intraneural interfaces hold great promise since they ensure high selectivity in communicating only with the desired nerve fascicles. Despite significant advancements, challenges such as chronic immune response, signal degradation over time, and lack of long-term biocompatibility remain critical considerations in the development of such devices. Here we report on the development and benchtop characterization of a novel design of an intraneural interface based on carbon fiber bundles. Carbon fibers possess low impedance, enabling enhanced signal detection and stimulation efficacy compared to traditional metal electrodes. We provided a 3D-stabilizing structure for the carbon fiber bundles made of PEDOT:PSS hydrogel, to enhance the biocompatibility between the carbon fibers and the nervous tissue. We further coated the overall bundles with a thin layer of elastomeric material to provide electrical insulation. Taken together, our results demonstrated that our electrode possesses adequate structural and electrochemical properties to ensure proper stimulation and recording of peripheral nerve fibers and a biocompatible interface with the nervous tissue.

3D-Printed Nerve Conduits Engineered nerve conduits (NCs) efficacy in restoring limiting gap lesions is still poor, due to low biomimicry. In article 2300136, Silvestro Micera, Xavier Navarro, and co-workers present an NC design that for the first time combines 3D-printing and freeze-drying techniques to yield conduits with tunable physiochemical properties. NCs restore limiting gap lesions of rat's sciatic nerve and can be therefore considered an alternative to autologous transplant. Image credit: Dr. Alessio Tommasetti, D'Arc Studio.

Nerve conduits may represent a valuable alternative to autograft for the regeneration of long-gap damages. However, no NCs have currently reached market approval for the regeneration of limiting gap lesions, which still represents the very bottleneck of this technology. In recent years, a strong effort has been made to envision an engineered graft to tackle this issue. In our recent work, we presented a novel design of porous/3D-printed chitosan/poly-ε-caprolactone conduits, coupling freeze drying and additive manufacturing technologies to yield conduits with good structural properties. In this work, we studied genipin crosslinking as strategy to improve the physiochemical properties of our conduit. Genipin is a natural molecule with very low toxicity that has been used to crosslink chitosan porous matrix by binding the primary amino group of chitosan chains. Our characterization evidenced a stabilizing effect of genipin crosslinking towards the chitosan matrix, with reported modified porosity and ameliorated mechanical properties. Given the reported results, this method has the potential to improve the performance of our conduits for the regeneration of long-gap nerve injuries.

In recent years, a great deal of effort has been undertaken with regards to treatment of pathologies at the level of the central nervous system (CNS). Here, the presence of the blood-brain barrier acts as an obstacle to the delivery of potentially effective drugs and makes accessibility to, and treatment of, the CNS one of the most significant challenges in medicine. In this Roadmap article, we present the status of the timeliest developments in the field, and identify the outstanding challenges and opportunities that exist. The format of the Roadmap, whereby experts in each discipline share their viewpoint and present their vision, reflects the dynamic and multidisciplinary nature of this research area, and is intended to generate dialogue and collaboration across traditional subject areas. It is stressed here that this article is not intended to act as a comprehensive review article, but rather an up-to-date and forward-looking summary of research methodologies pertaining to the treatment of pathologies at the level of the CNS.

When a traumatic event causes complete denervation, muscle functional recovery is highly compromised. A possible solution to this issue is the implantation of a biodegradable polymeric tubular scaffold, providing a biomimetic environment to support the nerve regeneration process. However, in the case of consistent peripheral nerve damage, the regeneration capabilities are poor. Hence, a crucial challenge in this field is the development of biodegradable micro- nanostructured polymeric carriers for controlled and sustained release of molecules to enhance nerve regeneration. The aim of these systems is to favor the cellular processes that support nerve regeneration to increase the functional recovery outcome. Drug delivery systems (DDSs) are interesting solutions in the nerve regeneration framework, due to the possibility of specifically targeting the active principle within the site of interest, maximizing its therapeutical efficacy. The scope of this review is to highlight the recent advances regarding the study of biodegradable polymeric DDS for nerve regeneration and to discuss their potential to enhance regenerative performance in those clinical scenarios characterized by severe nerve damage.

The fabrication of neural interfaces (NIs) typically relies nowadays on the implementation of complex, expensive, and time-consuming photolithographic processes. Metals and polymers are the materials currently used to fabricate NIs. Conductive polymers could be an alternative to metals to enhance the biocompatibility of the devices. Additive manufacturing techniques provide an easier and low-cost approach to process and finely tuning the geometrical and morphological features of polymers. Here, we propose a 3D printing strategy for the fabrication of completely polymeric neural interfaces, based on extrusion printing. The materials have been chosen to enhance the biocompatibility of the devices. PDMS has been chosen as insulating substrate, while a PEDOT:PSS-based ink has been selected for the conductive component. Morphological, mechanical, and rheological analyses on the inks have been carried out and a first prototype of a neural interface has been fabricated. The PDMS has a Young Modulus of 600 kPa, in the same order of magnitude as peripheral nerves, with a thickness of 160 μm. The PEDOT:PSS inks fabricated present a shear thinning behavior, ideal for an extrusion printing process This approach could represent a valuable alternative to photolithography and an innovative method for the fabrication of NIs, due to the high degree of customization, ease of implementation, low-cost and flexibility in materials choice.

Engineered grafts constitute an alternative to autologous transplant for repairing severe peripheral nerve injuries. However, current clinically available solutions have substantial limitations and are not suited for the repair of long nerve defects. A novel design of nerve conduit is presented here, which consists of a chitosan porous matrix embedding a 3D‐printed poly‐ε‐caprolactone mesh. These materials are selected due to their high biocompatibility, safe degradability, and ability to support the nerve regeneration process. The proposed design allows high control over geometrical features, pores morphology, compression resistance, and bending stiffness, yielding tunable and easy‐to‐manipulate grafts. The conduits are tested in chronic animal experiments, aiming to repair a 15‐mm long gap in the sciatic nerve of rats, and the results are compared with an autograft. Electrophysiological and nociception tests performed monthly during a 4‐month follow‐up show that these conduits allow a good degree of muscle functional recovery. Histological analyses show abundant cellularization in the wall and in the lumen of the conduits and regenerated axons within all rats treated with these grafts. It is suggested that the proposed conduits have the potential to repair nerves over the limiting gap length and can be proposed as strategy to overcome the limitations of autograft.

Implantable flexible neural interfaces (IfNIs) are capable of directly modulating signals of the central and peripheral nervous system by stimulating or recording the action potential. Despite outstanding results in acute experiments on animals and humans, their long-term biocompatibility is hampered by the effects of foreign body reactions that worsen electrical performance and cause tissue damage. We report on the fabrication of a polysaccharide nanostructured thin film as a coating of polyimide (PI)-based IfNIs. The layer-by-layer technique was used to coat the PI surface due to its versatility and ease of manufacturing. Two different LbL deposition techniques were tested and compared: dip coating and spin coating. Morphological and physiochemical characterization showed the presence of a very smooth and nanostructured thin film coating on the PI surface that remarkably enhanced surface hydrophilicity with respect to the bare PI surface for both the deposition techniques. However, spin coating offered more control over the fabrication properties, with the possibility to tune the coating’s physiochemical and morphological properties. Overall, the proposed coating strategies allowed the deposition of a biocompatible nanostructured film onto the PI surface and could represent a valid tool to enhance long-term IfNI biocompatibility by improving tissue/electrode integration.

Wireless optoelectronic devices are fabricated by controlling the porosity of p-type silicon, enabling in vivo efficient, non-genetic optoelectronic modulation of peripheral nerve activity.

Neural interfaces are bioelectronic devices capable of stimulating a population of neurons or nerve fascicles and recording electrical signals in a specific area. Despite their success in restoring sensory-motor functions in people with disabilities, their long-term exploitation is still limited by poor biocompatibility, mechanical mismatch between the device and neural tissue and the risk of a chronic inflammatory response upon implantation. In this context, the use of nature-derived materials can help address these issues. Examples of these materials, such as extracellular matrix proteins, peptides, lipids and polysaccharides, have been employed for decades in biomedical science. Their excellent biocompatibility, biodegradability in the absence of toxic compound release, physiochemical properties that are similar to those of human tissues and reduced immunogenicity make them outstanding candidates to improve neural interface biocompatibility and long-term implantation safety. The objective of this review is to highlight progress and challenges concerning the impact of nature-derived materials on neural interface design. The use of these materials as biocompatible coatings and as building blocks of insulation materials for use in implantable neural interfaces is discussed. Moreover, future perspectives are presented to show the increasingly important uses of these materials for neural interface fabrication and their possible use for other applications in the framework of neural engineering.

The lack of efficient targeting strategies poses significant limitations on the effectiveness of chemotherapeutic treatments. This issue also affects drug-loaded nanocarriers, reducing nanoparticles cancer cell uptake. We report on the fabrication and in vitro characterization of doxorubicin-loaded magnetic liposomes for localized treatment of liver malignancies. Colloidal stability, superparamagnetic behavior and efficient drug loading of our formulation were demonstrated. The application of an external magnetic field guaranteed enhanced nanocarriers cell uptake under cell medium flow in correspondence of a specific area, as we reported through in vitro investigation. A numerical model was used to validate experimental data of magnetic targeting, proving the possibility of accurately describing the targeting strategy and predict liposomes accumulation under different environmental conditions. Finally, in vitro studies on HepG2 cancer cells confirmed the cytotoxicity of drug-loaded magnetic liposomes, with cell viability reduction of about 50% and 80% after 24 h and 72 h of incubation, respectively. Conversely, plain nanocarriers showed no anti-proliferative effects, confirming the formulation safety. Overall, these results demonstrated significant targeting efficiency and anticancer activity of our nanocarriers and superparamagnetic nanoparticles entrapment could envision the theranostic potential of the formulation. The proposed magnetic targeting study could represent a valid tool for pre-clinical investigation regarding the effectiveness of magnetic drug targeting.

Lithography on a sub-100 nm scale is beyond the diffraction limits of standard optical lithography but is nonetheless a key step in many modern technological applications. At this length scale, there are several possible approaches that require either the preliminary surface deposition of materials or the use of expensive and time-consuming techniques. In our approach, we demonstrate a simple process, easily scalable to large surfaces, where the surface patterning that controls pore formation on highly doped silicon wafers is obtained by an electrochemical process. This method joins the advantages of the low cost of an electrochemical approach with its immediate scalability to large wafers.

The organic/inorganic interface in thin nanosized porous structures has a key role in determining the final properties of the composite materials. By use of the porous silicon/eumelanin hybrids as a case study, the role of this interface was investigated by experimental and computational methods. Our results show that an increased polymer density close to the hybrid interface strongly modifies the diffusion of the chemical species within the polymer molecule, affecting then the oxidation level of the pores’ inner Si surface. We observed a greater stability induced by increased pore diameter, a behavior that with computational and chemical arguments we attributed to a modified diffusion of the hydrogen peroxide toward the Si/eumelanin interface. Our results show that the overall behavior of a polymer when inserted in a tiny nanoscale structure must be taken into account for a correct understanding and control of the hybrids properties and that the formation of the interface alone may not be sufficient.

Longitudinal and transverse relaxivities of solid lipid: nanopatticles loaded with superparamagnetic iron oxide nanoparticles (SPION-SLNs) were thoroughly investigated with the aim of understanding the main parameters regulating the potential negative contrast properties of these systems. In particular, the longitudinal relaxivity (r(1)) of water protons in the 10 kHz to 35 MHz frequency range was determined by(1)H fast field-cycling NMR, while transverse relaxivity (r(2)) was measured at 21 MHz. The reproducibility and stability of SPION-SLNs was also tested on samples arising from independent preparations and at different tines after preparation. Water diffusion in proximity of superparamagnetic nanoparticles was found to be the mechanism of proton nuclear relaxation enhancement and characteristic parameters were quantitatively determined by fitting the experimental data acquired on different samples as a function of concentration and temperature. Although a variation ascribable to the formation Of clusters with a different number of SPIONs inhomogeneously embedded in the lipid matrix was observed among different preparations, the relaxivity properties of the investigated SPION-SLNs were found to be better than those of SPION-based contrast agents commonly considered as standard in the literature, and remained stable for at least 2 months.

We report here on the fabrication of a new example of nano-object that combines magnetic and plasmonic properties. The strategy is based on the electrostatic assembly of negatively charged gold nanorods (NIR-resonant) on positively charged silica-coated iron oxide nanoparticles. Silica coating of magnetic nanoparticles prevented iron oxide nanoparticles irreversible aggregation in water environment. Finally the stability of the nanocomposite in biological medium has been improved through a protein coating (BSA, bovine serum albumin). Morphological, optical and magnetic properties of the hybrid nanomaterials have been evaluated as well as its ability to be manipulated by an external magnetic field. Furthermore, temperature characterization upon NIR laser excitation has been performed in order to assess nanocomposite capability of increasing local environmental temperature. This nanomaterial could be used as a smart tool for photothermal treatment of cancerous lesions in order to maximize precision and efficacy of tissue heating upon laser stimulation by magnetically accumulating nanoparticles nearby the cancerous lesion, avoiding dispersion of the nanomaterial.

Sorafenib-loaded magnetic solid lipid nanoparticles are highly internalized by HepG2 human hepatocarcinoma cells. As described by A. Grillone, G. Ciofani, and co-workers on page 1681, the uptake of the nanoparticles can be directed by modulating their accumulation through an external magnetic field, thus focusing the drug effects at a desired site.

Sorafenib is an anticancer drug approved by the Food and Drug Administration for the treatment of hepatocellular and advanced renal carcinoma. The clinical application of sorafenib is promising, yet limited by its severe toxic side effects. The aim of this study is to develop sorafenib-loaded magnetic nanovectors able to enhance the drug delivery to the disease site with the help of a remote magnetic field, thus enabling cancer treatment while limiting negative effects on healthy tissues. Sorafenib and superparamagnetic iron oxide nanoparticles are encapsulated in solid lipid nanoparticles by a hot homogenization technique using cetyl palmitate as lipid matrix. The obtained nanoparticles (Sor-Mag-SLNs) have a sorafenib loading efficiency of about 90% and are found to be very stable in an aqueous environment. Plain Mag-SLNs exhibit good cytocompatibility, whereas an antiproliferative effect against tumor cells (human hepatocarcinoma HepG2) is observed for drug-loaded Sor-Mag-SLNs. The obtained results show that it is possible to prepare stable Sor-Mag-SLNs able to inhibit cancer cell proliferation through the sorafenib cytotoxic action, and to enhance/localize this effect in a desired area thanks to a magnetically driven accumulation of the drug. Moreover, the relaxivity properties observed in water suspensions hold promise for Sor-Mag-SLN tracking through clinical magnetic resonance imaging.