Project related news and papers

Project related news and papers (81)

Although so many innovations arose and so diverse material science approaches have been undertaken, only a very limited number of new products have been translated "from bench to bedside" into a clinical use in the last years. The reasons for this may be as manifold as the ingeneering ideas.

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Abstract

Although the gold standard for the surgical treatment of peripheral nerve injury, the autograft is associated with many drawbacks, including a second surgical procedure, donor site morbidity, mismatch of donor nerve size, and limited donor nerve length. As an alternative to the autograft, nerve guidance conduits may be used to promote neuronal growth and guide axonal extension after nerve injury. Using a blend of RGD-conjugated polyurea and polycaprolactone, a nerve guidance conduit was designed consisting of intraluminal microchannels with aligned nanofibers. A 10 mm sciatic nerve transection rat model was used to evaluate the efficacy of the conduit up to 8 weeks after nerve transection and conduit implantation. Restoration of electrophysiological activity from the nerve guidance conduit was significantly improved compared to the autograft. Functional and histological assessments indicated that the nerve guidance conduit is comparable to autograft in functional recovery and target muscle reinnervation, respectively.

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Abstract

  • A number of limitations associated with the use of hollow nerve guidance conduits (NGCs) require further discussion. Most importantly, the functional recovery outcomes after the placement of hollow NGCs are poor even after the successful bridging of peripheral nerve injuries. However, nerve regeneration scaffolds built using electric spinning have several advantages that may improve functional recovery. Thus, the present study summarizes recent developments in this area, including the key cells that are combined with the scaffold and associated with nerve regeneration, the structure and configuration of the electrospinning design (which determines the performance of the electrospinning scaffold), the materials the electrospinning fibers are composed of, and the methods used to control the morphology of a single fiber. Additionally, this study also discusses the processes underlying peripheral nerve regeneration. The primary goals of the present review were to evaluate and consolidate the findings of studies that used scaffolding biomaterials built by electrospinning used for peripheral nerve regeneration support. It is amazing that the field of peripheral nerve regeneration continues to consistently produce such a wide variety of innovative techniques and novel types of equipment, because the introduction of every new process creates an opportunity for advances in materials for nerve repair.

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  • The peripheral nervous system (PNS) may be damaged by traffic accidents and natural disasters. Nerve repair and regeneration are unique clinical challenges for surgeons. A smart nerve conduit (SNC) is designed that can significantly simplify the surgery process and achieve optimal peripheral nerve regeneration (PNR) by automatic gradual lengthening. For this purpose, five macromers with different rac-lactide to glycolide weight ratios are synthesized and the characteristics of the synthesized networks are studied. Cyclic thermomechanical measurements indicate the robustness of molecular structure for shape-memory function. Body-water-responsive shape-memory behavior is evaluated by use of angle-recovery measurements. The shape-recovery time of the polymer is adjusted by selection of comonomer ratio and the overall gradual-recovery function of a device can be realized by a suitable combination of different copolymers. Thus a trisegment smart nerve conduit is fabricated from this polymer system by electrospinning and is shown to gradually recover in an in vitro experiment under stimulated physiological conditions, that is, body-liquid environment (36 °C water). In vitro culture and qualitative immunocytochemistry of Schwann cells are used to assess the biocompatibility of the fabricated SNC.

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Abstract

  • Peripheral nerve injury is a very common medical condition with varying clinical severity but always great impact on the patients' productivity and the quality of life. Even the current 1st-choice surgical therapeutic approach or the “gold standard” as frequently called in clinical practice, is not addressing the problem efficiently and cost-effectively, increasing the mortality through the need of a second surgical intervention, while it does not take into account the several different types of nerves involved in peripheral nerve injuries. Neural tissue engineering approaches could potentially offer a very promising and attractive tool for the efficient peripheral nerve injury management, not only by mechanically building the gap, but also by inducing neuroregenerative mechanisms in a well-regulated microenvironment which would mimic the natural environment of the specific nerve type involved in the injury to obtain an optimum clinical outcome. There is still room for a lot of optimizations in regard to the conduits which have been developed with the help of neural engineering since many parameters affect the clinical outcome and the underlying mechanisms are still not well understood. Especially the intraluminal cues controlling the microenvironment of the conduits are in an infantile stage but there is profound potential in the application of the scaffolds. The aim of our review is to provide a quick reference to the recent advances in the field, focusing on the parameters that can significantly affect the clinical potentials of each approach, with suggestions for future improvements that could take the current work from bench to bedside. Thus, further research could shed light to those questions and it might hold the key to discover new more efficient and cost-effective therapies.

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Abstract

  • Background: Peripheral nerve injuries with substance loss are challenges to surgeons because direct suture repair may result in malfunction due to nerve suture tension. Autologous nerve grafts are alternatives for treating those lesions; however, harvesting grafts adds morbidity at donor sites. Synthetic substitutes are options to bridge the gaps in these situations. The caprolactone neurotubes are used to assist nerve regeneration, but the literature lacks studies that evaluate their results. Methods: This research was designed to clinically evaluate patients undergoing repair of peripheral nerves with that conduit. We described results of 12 case series consisting of operations with Neurolac®. All nerves severed were sensory and had small gaps (ie, less than 25 mm). Subjective and objective clinical evaluations were performed and registered. Results: Physical examination by monofilament testing and 2-point discrimination showed results rated as good or excellent. However, the patients had complaints regarding sensory changes. Conclusions: Synthetic bioabsorbable guides for nerve repair are promising. The caprolactone conduits were demonstrated to be a safe option treatment and with a simple technique. Although in our study there were some operative complications, they were in line with previous descriptions in the literature. This case series added information about the treatment prognosis, but a higher evidence level study is necessary for decision making.

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Nerve conduits prefilled with hydrogels are frequently explored in an attempt to promote nerve regeneration. This study examines the interplay in vivo between the porosity of the conduit wall and the level of bioactivity of the hydrogel used to fill the conduit. Nerve regeneration in porous (P) or nonporous (NP) conduits that were filled with either collagen only or collagen enhanced with a covalently attached neurite-promoting peptide mimic of the glycan human natural killer cell antigen-1 (m-HNK) were compared in a 5 mm critical size defect in the mouse femoral nerve repair model. Although collagen is a cell-friendly matrix that does not differentiate between neural and nonneural cells, the m-HNK-enhanced collagen specifically promotes axon growth and appropriate motor neuron targeting. In this study, animals treated with NP conduits filled with collagen grafted with m-HNK (CollagenHNK) had the best overall functional recovery, based on a range of histomorphometric observations and parameters of functional recovery. Our data indicate that under some conditions, the use of generally cell friendly fillers such as collagen may limit nerve regeneration. This finding is significant, considering the frequent use of collagen-based hydrogels as fillers of nerve conduits.

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Abstract

Over 200,000 Americans have peripheral nerve injuries annually that result in a loss of function and a compromised quality of life. Of these, a significant percent involves unsuccessful repair of peripheral nerve gaps that occur due to traumatic limb injury or collateral damage to peripheral nerves during tumor resection. The clinical gold standard to repair a nerve gap is to use sural nerve autografts. However, autografts are not ideal because of the need for secondary surgery to source the nerve, loss of function at the donor site, lack of source nerve in the event of diabetic neuropathies, neuroma formation, and the need for multiple grafts to bridge nerves. An alternative to autografting that has proved to have significantly less risks and sacrifices is a nerve conduit. While there are some nerve conduits approved for clinical applications (Pabari et al., 2010; Giusti et al., 2012), commercial nerve conduits for nerve repair are usually composed of type I collagen or biodegradable polymers, such that the conduit will degrade once the nerve has healed. Although possible complication from foreign materials is not negligible, nerve conduits have had success in bridging nerve gaps and restoring functionality to limbs. Unlike autografting, it does not require the sacrifice of the donor sural nerve.

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Abstract

We elucidate here process–structure–property relationships in implantable biomaterials processed by rapid prototyping approaches that are based on the principle of additive manufacturing. The conventional methods of fabrication of biomedical devices including freeze casting and sintering are limited because of difficulties in adaptation at the host site and mismatch in micro/macrostructure, mechanical and physical properties with the host tissue. Moreover, additive manufacturing has the advantage of fabricating patient-specific designs, which can be obtained from the computed tomography scan of the defect site. The discussion here comprises two parts – the first part briefly describes the evolution and underlying reasons that have led to 3D printing of scaffolds for tissue regeneration. The second part focuses on biocompatibility and mechanical properties of 3D scaffolds, fabricated by different approaches. The article concludes with a discussion on functionally graded scaffolds and vascularisation of 3D porous scaffolds that are envisaged to meet the requirements of the biomedical industry. In general, the mechanical properties of 3D printed scaffolds are governed by pore architecture, pore volume and percentage porosity. To ensure long-term endurance and the ability to withstand abrupt impact, it is important that the fabricated materials have a good combination of strength and energy absorption capability. While scaffolds with high interconnected porosity are preferred for tissue regeneration, such structures lack adequate mechanical strength and energy absorption capability. These mutually opposing requirements of high porosity and mechanical strength in conjunction with high energy absorption have hindered the application of 3D scaffolds as biomedical devices. In this regard, functionally graded 3D structures with high strength and energy absorption are potentially attractive for biomedical devices.
 

Abstract:

The use of a nerve conduit provides an opportunity to regulate cytokines, growth factors and neurotrophins in peripheral nerve regeneration and avoid autograft defects. We constructed a poly-D-L-lactide (PDLLA)-based nerve conduit that was modified using poly{(lactic acid)-co-[(glycolic acid)-alt-(L-lysine)]} and β-tricalcium phosphate. The effectiveness of this bioactive PDLLA-based nerve conduit was compared to that of PDLLA-only conduit in the nerve regeneration following a 10-mm sciatic nerve injury in rats. We observed the nerve morphology in the early period of regeneration, 35 days post injury, using hematoxylin-eosin and methylene blue staining. Compared with the PDLLA conduit, the nerve fibers in the PDLLA-based bioactive nerve conduit were thicker and more regular in size. Muscle fibers in the soleus muscle had greater diameters in the PDLLA bioactive group than in the PDLLA only group. The PDLLA-based bioactive nerve conduit is a promising strategy for repair after sciatic nerve injury.

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