Fabrication of Nanocomposites Complexed with Gold Nanoparticles on Polyaniline and Application to Their Nerve Regeneration

Liquid Metal-Based Conductive Nerve Guidance Conduit Combined With Electrical Stimulation Boosts Peripheral Nerve Repair

The combination of nerve guide conduits (NGCs) and electrical stimulation (ES) is an effective treatment for peripheral nerve injury (PNI). Flexible conductive materials with mechanical properties similar to those of biological tissues have been shown to have better long-term biointegration and functionality than rigid conductive materials. In this study, liquid metal (LM)-based conductive polycaprolactone/gelatin/polypyrrole/LM (PCL/Gel/PPy/LM, PGPL) NGC was combined with exogenous ES to repair PNI. PGPL membranes had good hydrophilicity, degradability, and mechanical properties, and its conductivity reached 0.66 ± 0.02 S/m. In vitro studies showed that the combination of PGPL membranes and ES (2 Hz, 100 mV/cm, 30 min/d) could significantly increase the expression of neuromarkers and had a better pro-neural differentiation effect. In vivo studies demonstrated that PGPL NGCs in combination with ES (2 Hz, 200 mV/mm, 30 min/d) could effectively promote morphological reconstruction and functional recovery of the sciatic nerve in rats. At 3 months post-surgery, PGPL NGCs combined with ES restored the nerve conduction velocity to 73.85% ± 5.45% of the normal value. The LM-based NGCs prepared in this study could effectively repair long sciatic nerve defects, which may further expand the application of LM in the field of nerve tissue engineering.

Facile and green synthesis of Au nanoparticles decorated Epigallocatechin-3-Gallate nanospheres with enhanced performance in stability, photothermal conversion and nanozymatic activity

In this study, epigallocatechin-3-gallate nanospheres (EGCG NSs) are employed as an innovative alternative to traditional reducing agents for the in-situ growth of AuNPs on the EGCG NS surface to produce the Au nanoparticles decorated EGCG nanospheres (EGCG NS@AuNPs). This eco-friendly approach avoids toxic chemicals and simplifies the synthesis process, enhancing biocompatibility and functional properties of the resulting EGCG NS@AuNPs nanocomposite. The nanocomposite exhibits remarkable stability, photothermal properties, and peroxidase-like enzymatic activity. Taking advantage of the enhanced photothermal properties, the application of EGCG NS@AuNPs in the antibacterial field was investigated, and the antibacterial activity was greatly improved against both Gram-negative and Gram-positive bacteria comparing to bare AuNPs or EGCG NS. Additionally, based on the excellent enzymatic activity, the sensing application of EGCG NS@AuNPs was explored by developing a colorimetric method for detecting ascorbic acid (AA). A remarkably low detection limit of 0.076 μM was achieved. This method has been successfully applied to measure the AA content in vitamin C tablets, demonstrating the practicality and accuracy of this approach. Therefore, the synthesis for EGCG NS@AuNPs is not only rapid, and cost-effective, but also eco-friendly and not harmful to biological systems, which is potential in biosensing, clinical diagnosis, and therapeutics. Future research could explore further applications of EGCG NS@AuNPs in biomedicine field, revealing even more of its remarkable potential.

Beyond templates: exploring uncharted territory in anisotropic gold nanostructure-oligomer composites synthesis and electrocatalytic performance towards environmental pollutants

The synthesis of polymer/oligomer-stabilized metal nanostructures (MNS) opens up a wide range of possibilities, from fundamental materials science to practical applications in domains such as medicine, catalysis, sensing, and energy. Because of the versatility of this synthetic approach, it is a dynamic and ever-changing field of study. These polymers/oligomers have precise control over the nucleation and growth kinetics, allowing the production of mono-disperse MNS with well-defined properties. The protective coating provided by polymers or oligomers increased the stability and colloidal dispersity of MNS in these oligomer-MNS composites. As a result, the current research reports the electrocatalytic reduction of nitrobenzene (NB) utilizing oligomeric aminomercaptotriazole (oligo AMTa) and oligo (AMTa-AuNS) modified glassy carbon (GC) electrodes developed via a wet chemical technique. UV-visible spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), high resolution mass spectroscopy (HR-MS), and high-resolution transmission electron microscopy (HR-TEM) approaches were used to confirm the development of oligomer and AuNS. After that, the GC electrode was directly linked to the oligo AMTa and oligo AMTa-AuNS by dipping them in the appropriate solutions. Scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and cycle voltammetry (CV) were all employed to confirm the fabrication of oligo AMTa and oligo AMTa-AuNS. Eventually, the electrochemical reduction of NB occurred using the fabricated electrodes. The catalytic activity of oligo AMTa-AuNS has been observed to be more than that of the other modified electrode. As an outcome, the film was employed to determine the sensitivity level of NB, and a limit of detection (LOD) of 2.8 nM was found. The straight-forward method's practical utility was proven by measuring NB in lake sample water.

Combining external physical stimuli and nanostructured materials for upregulating pro-regenerative cellular pathways in peripheral nerve repair

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.

Electrical stimulation and conductive materials: electrophysiology-based treatment for spinal cord injury

Spinal cord injury is a serious disease of the central nervous system. The electrophysiological properties of the spinal cord that are essential to maintaining neurotransmission can be impaired after the injury. Therefore, electrophysiological evaluation is becoming an important indicator of the injury extent or the therapeutic outcomes by reflecting the potential propagation of neural pathways. On the other hand, the repair of damaged nerves is one of the main goals of spinal cord injury treatment. Growing research interest has been concentrated on developing effective therapeutic solutions to restore the normal electrophysiological function of the injured spinal cord by using conductive materials and/or exerting the merits of electrical stimulation. Accordingly, this review introduces the current common electrophysiological evaluation in spinal cord injury. Then the cutting-edge therapeutic strategies aiming at electrophysiological improvement in spinal cord injury are summarized. Finally, the challenges and future prospects of neural restoration after spinal cord injury are presented.

Recent perspectives on the synergy of mesenchymal stem cells with micro/nano strategies in peripheral nerve regeneration-a review

Despite the intrinsic repair of peripheral nerve injury (PNI), it is important to carefully monitor the process of peripheral nerve repair, as peripheral nerve regeneration is slow and incomplete in large traumatic lesions. Hence, mesenchymal stem cells (MSCs) with protective and regenerative functions are utilized in synergy with innovative micro/nano technologies to enhance the regeneration process of peripheral nerves. Nonetheless, as MSCs are assessed using standard regenerative criteria including sensory-motor indices, structural features, and morphology, it is challenging to differentiate between the protective and regenerative impacts of MSCs on neural tissue. This study aims to analyze the process of nerve regeneration, particularly the performance of MSCs with and without synergistic approaches. It also focuses on the paracrine secretions of MSCs and their conversion into neurons with functional properties that influence nerve regeneration after PNI. Furthermore, the study explores new ideas for nerve regeneration after PNI by considering the synergistic effect of MSCs and therapeutic compounds, neuronal cell derivatives, biological or polymeric conduits, organic/inorganic nanoparticles, and electrical stimulation. Finally, the study highlights the main obstacles to developing synergy in nerve regeneration after PNI and aims to open new windows based on recent advances in neural tissue regeneration.

Oriented polyaniline/poly-l-lactic acid/gelatin nanofiber scaffolds promote outgrowth of spiral ganglion neurons

Sensorineural hearing loss (SNHL) is caused by the loss of sensory hair cells (HCs) and/or connected spiral ganglion neurons (SGNs). The current clinical conventional treatment for SNHL is cochlear implantation (CI). The principle of CI is to bypass degenerated auditory HCs and directly electrically stimulate SGNs to restore hearing. However, the effectiveness of CI is limited when SGNs are severely damaged. In the present study, oriented nanofiber scaffolds were fabricated using electrospinning technology to mimic the SGN spatial microenvironment in the inner ear. Meanwhile, different proportions of polyaniline (PANI), poly-l-lactide (PLLA), gelatin (Gel) were composited to mimic the composition and mechanical properties of auditory basement membrane. The effects of oriented PANI/PLLA/Gel biomimetic nanofiber scaffolds for neurite outgrowth were analyzed. The results showed the SGNs grew in an orientation along the fiber direction, and the length of the protrusions increased significantly on PANI/PLLA/Gel scaffold groups. The 2% PANI/PLLA/Gel group showed best effects for promoting SGN adhesion and nerve fiber extension. In conclusion, the biomimetic oriented nanofiber scaffolds can simulate the microenvironment of SGNs as well as promote neurite outgrowth in vitro, which may provide a feasible research idea for SGN regeneration and even therapeutic treatments of SNHL in future.

Neuro-bone tissue engineering: emerging mechanisms, potential strategies, and current challenges

The skeleton is a highly innervated organ in which nerve fibers interact with various skeletal cells. Peripheral nerve endings release neurogenic factors and sense skeletal signals, which mediate bone metabolism and skeletal pain. In recent years, bone tissue engineering has increasingly focused on the effects of the nervous system on bone regeneration. Simultaneous regeneration of bone and nerves through the use of materials or by the enhancement of endogenous neurogenic repair signals has been proven to promote functional bone regeneration. Additionally, emerging information on the mechanisms of skeletal interoception and the central nervous system regulation of bone homeostasis provide an opportunity for advancing biomaterials. However, comprehensive reviews of this topic are lacking. Therefore, this review provides an overview of the relationship between nerves and bone regeneration, focusing on tissue engineering applications. We discuss novel regulatory mechanisms and explore innovative approaches based on nerve-bone interactions for bone regeneration. Finally, the challenges and future prospects of this field are briefly discussed.

Nanoporous electroporation needle for localized intracellular delivery in deep tissues

The exogenous control of intracellular drug delivery has been shown to improve the overall efficacy of therapies by reducing nonspecific off-target toxicity. However, achieving a precise on-demand dosage of a drug in deep tissues with minimal damage is still a challenge. In this study, we report an electric-pulse-driven nanopore-electroporation (nEP) system for the localized intracellular delivery of a model agent in deep tissues. Compared with conventional bulk electroporation, in vitro nEP achieved better transfection efficiency (>60%) with a high cell recovery rate (>95%) under a nontoxic low electroporation condition (40 V). Furthermore, in vivo nEP using a nanopore needle electrode with a side drug-releasing compartment offered better control over the dosage release, time, and location of propidium iodide, which was used as a model agent for intracellular delivery. In a pilot study using experimental animals, the nEP system exhibited two times higher transfection efficiency of propidium iodide in the thigh muscle tissue, while minimizing tissue damage (<20%) compared to that of bulk electroporation. This tissue-penetrating nEP platform can provide localized, safe, and effective intracellular delivery of diverse therapeutics into deep tissues in a controlled manner.

Designing Electrical Stimulation Platforms for Neural Cell Cultivation Using Poly(aniline): Camphorsulfonic Acid

Electrical stimulation is a powerful strategy to improve the differentiation of neural stem cells into neurons. Such an approach can be implemented, in association with biomaterials and nanotechnology, for the development of new therapies for neurological diseases, including direct cell transplantation and the development of platforms for drug screening and disease progression evaluation. Poly(aniline):camphorsulfonic acid (PANI:CSA) is one of the most well-studied electroconductive polymers, capable of directing an externally applied electrical field to neural cells in culture. There are several examples in the literature on the development of PANI:CSA-based scaffolds and platforms for electrical stimulation, but no review has examined the fundamentals and physico-chemical determinants of PANI:CSA for the design of platforms for electrical stimulation. This review evaluates the current literature regarding the application of electrical stimulation to neural cells, specifically reviewing: (1) the fundamentals of bioelectricity and electrical stimulation; (2) the use of PANI:CSA-based systems for electrical stimulation of cell cultures; and (3) the development of scaffolds and setups to support the electrical stimulation of cells. Throughout this work, we critically evaluate the revised literature and provide a steppingstone for the clinical application of the electrical stimulation of cells using electroconductive PANI:CSA platforms/scaffolds.

Exploring the Physicochemical, Electroactive, and Biodelivery Properties of Metal Nanoparticles on Peripheral Nerve Regeneration

Despite the advances in the regeneration/rehabilitation field of damaged tissues, the functional recovery of peripheral nerves (PNs), especially in a long gap injury, is considered a great medical challenge. Recent progress in nanomedicine has provided great hope for PN regeneration through the strategy of controlling cell behavior by metal nanoparticles individually or loaded on scaffolds/conduits. Despite the confirmed toxicity of metal nanoparticles due to long-term accumulation in nontarget tissues, they play a role in the damaged PN regeneration based on the topography modification of scaffolds/conduits, enhancing neurotrophic factor secretion, the ion flow improvement, and the regulation of electrical signals. Determining the fate of neural progenitor cells would be a major achievement in PN regeneration, which seems to be achievable by metal nanoparticles through altering cell vital approaches and controlling their functions. Therefore, in this literature, an attempt was made to provide an overview of the effective activities of metal nanoparticles on the PN regeneration, until the vital clues of the PN regeneration and how they are changed by metal nanoparticles are revealed to the researcher.

Development of a highly sensitive glucose nanocomposite biosensor based on recombinant enzyme from corn

BACKGROUND

Enzymes are biocatalysts that play a vital role in the production of biomolecules. Plants can be a valuable and cost-effective source for producing well-structured recombinant enzymes. Glucose is one of the most important biological molecules, providing energy to most living systems. An electrochemical method for immobilization of enzyme is promising because it is economic, generates less component waste, improves the signal-to-noise ratio, leads to a lower limit of detection, and stabilizes and protects the enzyme structure.

RESULTS

A glucose biosensor was constructed using polyaniline (PANI) and a recombinant enzyme from corn, plant-produced manganese peroxidase (PPMP), with polymerization of aniline as a monomer in the presence of gold nanoparticles (AuNPs)-glucose oxidase (GOx), and bovine serum albumin. Using linear sweep voltammetry and cyclic voltammetry techniques, PANI-AuNPs-GOx-PPMP/Au electrode exhibited a superior sensing property with a wider linear range of 0.005-16.0 mm, and a lower detection limit of 0.001 mm compared to PANI-GOx-PPMP/Au electrode and PANI-GOx-PPMP/AuNPs/Au electrode. The biosensor selectivity was assessed by determining glucose concentrations in the presence of ascorbic acid, dopamine, aspartame, and caffeine.

CONCLUSION

We conclude that a plant-produced Mn peroxidase enzyme combined with conductive polymers and AuNPs results in a promising nanocomposite biosensor for detecting glucose. The use of such devices for quality control in the food industry can have a significant economic impact. © 2022 Society of Chemical Industry.

Gold nanorods decorated polycaprolactone/cellulose acetate hybrid scaffold for PC12 cells proliferation

Synthetic and natural polymers have recently received considerable attention due to the exclusive potential for supporting the regenerative cellular processes in peripheral nerve injuries (PNIs). Gold nanorods (GNRs) decorated polycaprolactone (PCL)/cellulose acetate (CA) nanocomposite (PCL/CA/GNR) were fabricated via electrospinning to improve PC12 cells attachment and growth or scaffold cues. Transmission electron microscopy (TEM) corroborated the GNR distribution (23 ± 2 nm length and 3/1 Aspect ratio) and suitable average dimension of 800 nm for the fibers; also, scanning electron microscopy (SEM) represented block-free and smooth fibers without perturbation. Because of gold nanorods incorporation, electrical conductivity of PCL/CA/GNR increased ~21%. Water contact angle data emphasized PCL/CA/GNR surface is more wettable that PCL/CA (<90° at 62 s). Real-time PCR technique (RT-PCR) demonstrated overexpression of β-tubulin and microtubule-associated protein 2 (MAP2) on PCL/CA/GNR compared to PCL/CA composite. Additionally, evaluated of the maturation and neurogenic differentiation of PC12 cells emphasized overexpression of nestin and β-tubulin by Immunocytochemistry staining onto PCL/CA/GNR in comparison to PCL/CA composite. Notably, these recently developed hybrid scaffolds could be considered for peripheral nerve injury (PNI) regeneration.

Gold-Polymer Nanocomposites for Future Therapeutic and Tissue Engineering Applications

Gold nanoparticles (AuNPs) have been extensively investigated for their use in various biomedical applications. Owing to their biocompatibility, simple surface modifications, and electrical and unique optical properties, AuNPs are considered promising nanomaterials for use in in vitro disease diagnosis, in vivo imaging, drug delivery, and tissue engineering applications. The functionality of AuNPs may be further expanded by producing hybrid nanocomposites with polymers that provide additional functions, responsiveness, and improved biocompatibility. Polymers may deliver large quantities of drugs or genes in therapeutic applications. A polymer alters the surface charges of AuNPs to improve or modulate cellular uptake efficiency and their biodistribution in the body. Furthermore, designing the functionality of nanocomposites to respond to an endo- or exogenous stimulus, such as pH, enzymes, or light, may facilitate the development of novel therapeutic applications. In this review, we focus on the recent progress in the use of AuNPs and Au-polymer nanocomposites in therapeutic applications such as drug or gene delivery, photothermal therapy, and tissue engineering.

Anisotropic scaffolds for peripheral nerve and spinal cord regeneration

The treatment of long-gap (>10 mm) peripheral nerve injury (PNI) and spinal cord injury (SCI) remains a continuous challenge due to limited native tissue regeneration capabilities. The current clinical strategy of using autografts for PNI suffers from a source shortage, while the pharmacological treatment for SCI presents dissatisfactory results. Tissue engineering, as an alternative, is a promising approach for regenerating peripheral nerves and spinal cords. Through providing a beneficial environment, a scaffold is the primary element in tissue engineering. In particular, scaffolds with anisotropic structures resembling the native extracellular matrix (ECM) can effectively guide neural outgrowth and reconnection. In this review, the anatomy of peripheral nerves and spinal cords, as well as current clinical treatments for PNI and SCI, is first summarized. An overview of the critical components in peripheral nerve and spinal cord tissue engineering and the current status of regeneration approaches are also discussed. Recent advances in the fabrication of anisotropic surface patterns, aligned fibrous substrates, and 3D hydrogel scaffolds, as well as their in vitro and in vivo effects are highlighted. Finally, we summarize potential mechanisms underlying the anisotropic architectures in orienting axonal and glial cell growth, along with their challenges and prospects.

Hybrid Nanosystems for Biomedical Applications

Inorganic/organic hybrid nanosystems have been increasingly developed for their versatility and efficacy at overcoming obstacles not readily surmounted by nonhybridized counterparts. Currently, hybrid nanosystems are implemented for gene therapy, drug delivery, and phototherapy in addition to tissue regeneration, vaccines, antibacterials, biomolecule detection, imaging probes, and theranostics. Though diverse, these nanosystems can be classified according to foundational inorganic/organic components, accessory moieties, and architecture of hybridization. Within this Review, we begin by providing a historical context for the development of biomedical hybrid nanosystems before describing the properties, synthesis, and characterization of their component building blocks. Afterward, we introduce the architectures of hybridization and highlight recent biomedical nanosystem developments by area of application, emphasizing hybrids of distinctive utility and innovation. Finally, we draw attention to ongoing clinical trials before recapping our discussion of hybrid nanosystems and providing a perspective on the future of the field.

In situ microsynthesis of polyaniline: synthesis–structure–conductivity correlation

The multi-analytical study of polyaniline samples obtained by in situ microsynthesis was performed.

Zero-valent iron nanoparticles containing nanofiber scaffolds for nerve tissue engineering

Regeneration of nerve tissue is a challenging issue in regenerative medicine. Especially, the peripheral nerve defects related to the accidents are one of the leading health problems. For large degeneration of peripheral nerve, nerve grafts are used in order to obtain a connection. These grafts should be biodegradable to prevent second surgical intervention. In order to make more effective nerve tissue engineering materials, nanotechnological improvements were used. Especially, the addition of electrically conductive and biocompatible metallic particles and carbon structures has essential roles in the stimulation of nerves. However, the metabolizing of these structures remains to wonder because of their nondegradable nature. In this study, biodegradable and conductive nerve tissue engineering materials containing zero-valent iron (Fe) nanoparticles were developed and investigated under in vitro conditions. By using electrospinning technique, fibrous mats composed of electrospun poly(ε-caprolactone) (PCL) nanofibers and Fe nanoparticles were obtained. Both electrical conductivity and mechanical properties increased compared with control group that does not contain nanoparticles. Conductivity of PCL/Fe5 and PCL/Fe10 increased to 0.0041 and 0.0152 from 0.0013 Scm^-1 , respectively. Cytotoxicity results indicated toxicity for composite mat containing 20% Fe nanoparticles (PCL/Fe20). SH-SY5Y cells were grown on PCL/Fe10 best, which contains 10% Fe nanoparticles. Beta III tubulin staining of dorsal root ganglion neurons seeded on mats revealed higher cell number on PCL/Fe10. This study demonstrated the impact of zero-valent Fe nanoparticles on nerve regeneration. The results showed the efficacy of the conductive nanoparticles, and the amount in the composition has essential roles in the promotion of the neurites.