Development of chitosan-crosslinked nanofibrous PHBV guide for repair of nerve defects

Review on electrically conductive smart nerve guide conduit for peripheral nerve regeneration

At present, peripheral nerve injuries (PNIs) are one of the leading causes of substantial impairment around the globe. Complete recovery of nerve function after an injury is challenging. Currently, autologous nerve grafts are being used as a treatment; however, this has several downsides, for example, donor site morbidity, shortage of donor sites, loss of sensation, inflammation, and neuroma development. The most promising alternative is the development of a nerve guide conduit (NGC) to direct the restoration and renewal of neuronal axons from the proximal to the distal end to facilitate nerve regeneration and maximize sensory and functional recovery. Alternatively, the response of nerve cells to electrical stimulation (ES) has a substantial regenerative effect. The incorporation of electrically conductive biomaterials in the fabrication of smart NGCs facilitates the function of ES throughout the active proliferation state. This article overviews the potency of the various categories of electroactive smart biomaterials, including conductive and piezoelectric nanomaterials, piezoelectric polymers, and organic conductive polymers that researchers have employed latterly to fabricate smart NGCs and their potentiality in future clinical application. It also summarizes a comprehensive analysis of the recent research and advancements in the application of ES in the field of NGC.

Biomedical Applications of the Biopolymer Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV): Drug Encapsulation and Scaffold Fabrication

Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is a biodegradable and biocompatible biopolymer that has gained popularity in the field of biomedicine. This review provides an overview of recent advances and potential applications of PHBV, with special emphasis on drug encapsulation and scaffold construction. PHBV has shown to be a versatile platform for drug delivery, offering controlled release, enhanced therapeutic efficacy, and reduced side effects. The encapsulation of various drugs, such as anticancer agents, antibiotics, and anti-inflammatory drugs, in PHBV nanoparticles or microspheres has been extensively investigated, demonstrating enhanced drug stability, prolonged release kinetics, and increased bioavailability. Additionally, PHBV has been used as a scaffold material for tissue engineering applications, such as bone, cartilage, and skin regeneration. The incorporation of PHBV into scaffolds has been shown to improve mechanical properties, biocompatibility, and cellular interactions, making them suitable for tissue engineering constructs. This review highlights the potential of PHBV in drug encapsulation and scaffold fabrication, showing its promising role in advancing biomedical applications.

Bridging potential of Taurine-loading PCL conduits transplanted with hEnSCs on resected sciatic nerves

Reconstruction of nerve conduits is a promising method for functional improvement in peripheral nerve repair. Besides choosing of a suitable polymer for conduit construction, adding factors such as Taurine improve a more advantageous microenvironment for defect nerve regeneration. Showing several major biological properties of Taurine, for example, regulation of the osmotic pressure, modulation of neurogenesis, and calcium hemostasis, makes it an appropriate option for repairing of defected nerves. To this, we examined repairing effects of Taurine-loading PCL conduits cultured with human endothelial stem cells (hEnSCs) on resected sciatic nerves. PCL/Taurine/Cell conduits transplanted to a 10-mm sciatic nerve gap. Forty-two wistar rats were randomly divided to seven groups: (1) Normal group, (2) Negative control (NC), (3) Positive control (nerve Autograft group), (4) PCL conduits group (PCL), (5) Taurine loaded PCL conduits group (PCL/Taurine), (6) hEnSCs cultured on the PCL conduits (PCL/Cell), (7) hEnSCs cultured on the PCL/Taurine conduits (PCL/Taurine/Cell). Functional recovery of motor and sensory nerves, the action potential of exciting muscle and motor distal latency has seen in PCL/Taurine/Cell conduits. Histological studies showed also remarkable nerve regeneration and obvious bridging has seen in this group. In conclusion, PCL/Taurine/Cell conduits showing suitable mechanical properties and biocompatibility may improve sciatic nerve regeneration.

Effects of Platelet-Rich Fibrin/Collagen Membrane on Sciatic Nerve Regeneration

ABSTRACT

Alternative treatment approaches to improve the regeneration ability of damaged peripheral nerves are currently under investigation. The aim of the current study was to evaluate the effects of leucocyte/platelet-rich fibrin (L-PRF) with or without a collagen membrane as a supporter on crushed sciatic nerve healing in a rat model. Recovery of motor function and electrophysiologic measurements were evaluated at 4 weeks postoperatively. The whole number of myelinated axons, peripheral nerve axon density, average nerve fiber diameter (μm), and G-ratio were analyzed and compered among the groups. Functional, electrophysiological, and histological evaluations showed no significant difference among the groups with the exception of the L-PRF with collagen membrane groups that showed relatively positive effects on the functional and histological nerve recovery. In addition, the collagen membrane with L-PRF can be effect in nerve regeneration.

Radiopaque Chitosan Ducts Fabricated by Extrusion-Based 3D Printing to Promote Healing After Pancreaticoenterostomy

Long-term placement of non-degradable silicone rubber pancreatic duct stents in the body is likely to cause inflammation and injury. Therefore, it is necessary to develop degradable and biocompatible stents to replace silicone rubber tubes as pancreatic duct stents. The purpose of our research was to verify the feasibility and biological safety of extrusion-based 3D printed radiopaque chitosan (CS) ducts for pancreaticojejunostomy. Chitosan-barium sulfate (CS-Ba) ducts with different molecular weights (low-, medium-, and high-molecular weight CS-Ba: LCS-Ba, MCS-Ba, and HCS-Ba, respectively) were soaked in vitro in simulated pancreatic juice (SPJ) (pH 8.0) with or without pancreatin for 16 weeks. Changes in their weight, water absorption rate and mechanical properties were tested regularly. The biocompatibility, degradation and radiopaque performance were verified by in vivo and in vitro experiments. The results showed that CS-Ba ducts prepared by this method had regular compact structures and good molding effects. In addition, the lower the molecular weight of the CS-Ba ducts was, the faster the degradation rate was. Extrusion-based 3D-printed CS-Ba ducts have mechanical properties that match those of soft tissue, good biocompatibility and radioopacity. In vitro studies have also shown that CS-Ba ducts can promote the growth of fibroblasts. These stents have great potential for use in pancreatic duct stent applications in the future.

Chitin/Chitosan: Versatile Ecological, Industrial, and Biomedical Applications

Chitin is a linear polysaccharide of N-acetylglucosamine, which is highly abundant in nature and mainly produced by marine crustaceans. Chitosan is obtained by hydrolytic deacetylation. Both polysaccharides are renewable resources, simply and cost-effectively extracted from waste material of fish industry, mainly crab and shrimp shells. Research over the past five decades has revealed that chitosan, in particular, possesses unique and useful characteristics such as chemical versatility, polyelectrolyte properties, gel- and film-forming ability, high adsorption capacity, antimicrobial and antioxidative properties, low toxicity, and biocompatibility and biodegradability features. A plethora of chemical chitosan derivatives have been synthesized yielding improved materials with suggested or effective applications in water treatment, biosensor engineering, agriculture, food processing and storage, textile additives, cosmetics fabrication, and in veterinary and human medicine. The number of studies in this research field has exploded particularly during the last two decades. Here, we review recent advances in utilizing chitosan and chitosan derivatives in different technical, agricultural, and biomedical fields.

Strategies to improve nerve regeneration after radical prostatectomy: a narrative review

Peripheral nerves are complex organs that spread throughout the entire human body. They are frequently affected by lesions not only as a result of trauma but also following radical tumor resection. In fact, despite the advancement in surgical techniques, such as nerve-sparing robot assisted radical prostatectomy, some degree of nerve injury may occur resulting in erectile dysfunction with significant impairment of the quality of life. The aim of this review was to provide an overview on the mechanisms of the regeneration of injured peripheral nerves and to describe the potential strategies to improve the regeneration process and the functional recovery. Yet, the recent advances in bio-engineering strategies to promote nerve regeneration in the urological field are outlined with a view on the possible future regenerative therapies which might ameliorate the functional outcome after radical prostatectomy.

Nanoscaffolds in promoting regeneration of the peripheral nervous system

The ability to surgically repair peripheral nerve injuries is urgently needed. However, traditional tissue engineering techniques, such as autologous nerve transplantation, have some limitations. Therefore, tissue engineered autologous nerve grafts have become a suitable choice for nerve repair. Novel tissue engineering techniques derived from nanostructured conduits have been shown to be superior to other successful functional neurological structures with different scaffolds in terms of providing the required structures and properties. Additionally, different biomaterials and growth factors have been added to nerve scaffolds to produce unique biological effects that promote nerve regeneration and functional recovery. This review summarizes the application of different nanoscaffolds in peripheral nerve repair and further analyzes how the nanoscaffolds promote peripheral nerve regeneration.

Use new poly (ε-caprolactone/collagen/NBG) nerve conduits along with NGF for promoting peripheral (sciatic) nerve regeneration in a rat

Regeneration of peripheral nerve defects remained a remarkable clinical challenge. Engineered nerve conduits represent a promising strategy to improve functional recovery in peripheral nerve injury repair. However, nerve conduits require additional factors such as neurotrophic factors to create a more conducive microenvironment for nerve regeneration. Neurotrophic factors have well-demonstrated abilities to improve neurite outgrowth, making them great candidates for repairing of defected nerves. To this end, we examined the beneficial effects of repairing the transected rat sciatic nerve by loading of nerve growth factor (NGF) in nerve conduits. The PCL/Collagen/NBG conduits were interposed into the 10 mm right sciatic nerve defects. Twenty-four rats were randomly allocated into four groups: 1- nerve autograft group, 2- a nongrafted group with gap 10-mm, 3- conduit group and 4- the conduits loaded with NGF. Motor and sensory functional recovery, the evoked muscle action potential, and motor distal latency showed significant improvement in rats treated with NGF. The histology and immunohistochemistry studies revealed less fibrosis and a high level of expression of CD31 and NF-200 protein at the crush site in the Conduit + NGF group. In conclusion, the PCL/Collagen/NBG conduit loaded with NGF, which exhibited nanometer-scale features, neurotrophic activity, favorable mechanical properties and biocompatibility could improve sciatic nerve regeneration in rats.

Gold nano-decorated aligned polyurethane nanofibers for enhancement of neurite outgrowth and elongation

Neurite outgrowth and elongation of neural cells is the most important subject that is considered in nerve tissue engineering. In this regard, aligned nanofibers have taken much attention in terms of providing guidance for newly outgrown neurites. The main objective of this study was to fabricate aligned polyurethane nanofibers by electrospinning process and decorate them with gold nanoparticles to further investigate the synergistic effects of nanotopography, biological nerve growth factor (NGF) and electrical stimulations on neurite outgrowth and elongation of pheochromocytoma (PC-12) model cells. In this regard, smooth and uniform aligned polyurethane nanofibers with the average diameter of 519 ± 56 nm were fabricated and decorated with the gold nanoparticles with the average diameter of ∼50 nm. PC-12 cells were cultured on the various nanofiber surfaces inside the bio-mimetic bioreactor system and exposed either to NGF alone or combination of NGF and electrical stimulation. It was found that 50 ng/mL NGF concentration is an optimal value for the stimulation of neurite outgrowth. After 4 days of culture under 100 mV, 10 ms electrical stimulation in 1 h/day period it was found that the gold nanoparticle decorated aligned polyurethane nanofibers increased the neurite outgrowth and elongation more with the combinational NGF and electrical stimulation. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1604-1613, 2018.

Nerve growth factor loaded heparin/chitosan scaffolds for accelerating peripheral nerve regeneration

Artificial chitosan scaffolds have been widely investigated for peripheral nerve regeneration. However, the effect was not as good as that of autologous grafts and therefore could not meet the clinical requirement. In the present study, the nerve growth factor (NGF) loaded heparin/chitosan scaffolds were fabricated via electrostatic interaction for further improving nerve regeneration. The physicochemical properties including morphology, wettability and composition were measured. The heparin immobilization, NGF loading and release were quantitatively and qualitatively characterized, respectively. The effect of NGF loaded heparin/chitosan scaffolds on nerve regeneration was evaluated by Schwann cells culture for different periods. The results showed that the heparin immobilization and NGF loading did not cause the change of bulk properties of chitosan scaffolds except for morphology and wettability. The pre-immobilization of heparin in chitosan scaffolds could enhance the stability of subsequently loaded NGF. The NGF loaded heparin/chitosan scaffolds could obviously improve the attachment and proliferation of Schwann cells in vitro. More importantly, the NGF loaded heparin/chitosan scaffolds could effectively promote the morphology development of Schwann cells. The study may provide a useful experimental basis to design and develop artificial implants for peripheral nerve regeneration and other tissue regeneration.

A suspended carbon fiber culture to model myelination by human Schwann cells

Understanding of myelination/remyelination process is essential to guide tissue engineering for nerve regeneration. In vitro models currently used are limited to cell population studies and cannot easily identify individual cell contribution to the process. We established a novel model to study the contribution of human Schwann cells to the myelination process. The model avoids the presence of neurons in culture; Schwann cells respond solely to the biophysical properties of an artificial axon. The model uses a single carbon fiber suspended in culture media far from the floor of the well. The fiber provides an elongated structure of defined diameter with 360-degree of surface available for human Schwann cells to wrap around. This model enabled us to spatially and temporally track the myelination by individual Schwann cells along the fiber. We observed cell attachment, elongation and wrapping over a period of 9 days. Cells remained alive and expressed Myelin Basic Protein and Myelin Associated Glycoprotein as expected. Natural and artificial molecules, and external physical factors (e.g., p atterned electrical impulses), may be tested with this model as possible regulators of myelination.

Human unrestricted somatic stem cells loaded in nanofibrous PCL scaffold and their healing effect on skin defects

Unrestricted somatic stem cells (USSCs) loaded in nanofibrous polycaprolactone (PCL) scaffolds can be used for skin regeneration when grafted onto full-thickness skin defects of rats. Nanofibrous PCL scaffolds were designed by the electrospinning method and crosslinked with laminin protein. Afterwards, the scaffolds were evaluated by scanning electron microscopy, and physical and mechanical assays. In this study, nanofibrous PCL scaffolds loaded with USSCs were grafted onto the skin defects. The wounds were subsequently investigated 21 days after grafting. Results of mechanical and physical analyses showed good resilience and compliance to movement as a skin graft. In animal models; study samples exhibited the most pronounced effect on wound closure, with statistically significant improvement in wound healing being seen at 21 days post-operatively. Histological examinations of healed wounds from all samples showed a thin epidermis plus recovered skin appendages in the dermal layer for samples with cell. Thus, the graft of nanofibrous PCL scaffolds loaded with USSC showed better results during the healing process of skin defects in rat models.