Project related news and papers

Project related news and papers (83)

Novel poly-L-lactic acid (PLLA) microtube array membranes (MTAMs) with a porous wall structure were prepared by electrospinning. Porogen of polyethylene glycol (PEG) was mixed with PLLA and dissolved in a dichloromethane/dimethylformamide solvent. The solution dope was delivered to the outer layer of coaxial spinneret, while the PEG/polyethylene oxide (50/50 wt. %) aqueous solution was delivered to the core layer, to form arrays of core-shell fibers through an electrospinning process. Porogen was then washed off to produce array of microtubes with a porous wall structure. The morphology and physical properties of the MTAMs were characterized by scanning electron microscopy (SEM), a texture analyzer (TA), and a thermogravimetric analysis (TGA). With porogen content of 0~50 wt.%, pores, ranging from a few tens of nanometers to a few microns, were clearly seen in SEM micrographs for the surface of PLLA/PEG30-50 MTAMs after the washing process. However, porogen was effectively washed off only from PLLA/PEG30-50 MTAMs, thus their wall structure was transformed from a dense to porous one. PLLA/PEG MTAMs remained relatively hydrophobic. Young’s modulus of PLLA/PEG MTAMs decreased from 850 to 400 kPa, while the fracture work increased from 854 g.mm to a maximum value of 4478 g.mm for PLLA/PEG10. Permeation through MTAMs was conducted, and results revealed that only pores in the walls of PLLA/PEG30-50 MTAMs were well interconnected. Cumulative permeation increased with the PEG content. These results suggest that multifunctional porous PLLA MTAMs can potentially be used in medical applications, such as nerve regeneration conduits.

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Sterilisation is essential for any implantable medical device in order to prevent infection in patients. The selection of the most appropriate sterilisation method depends on the nature and the physical state of the material to be sterilised; the influence of the sterilisation method on the properties of the device; and the type of the potential contaminant. In this context, herein we review the influence of ethylene oxide, γ-irradiation, e-beam irradiation, gas plasma, peracetic acid and ethanol on structural, biomechanical, biochemical and biological properties of collagen-based devices. Data to-date demonstrate that chemical approaches are associated with cytotoxicity, whilst physical methods are associated with degradation, subject to the device physical characteristics. Thus, the sterilisation method of choice is device dependent.

Biomaterials should be mechanically tested at both the nanoscale and macroscale under conditions simulating their working state, either in vitro or in vivo, to confirm their applicability in tissue engineering applications. In this article, polyester-urethane-based films and porous scaffolds produced by hot pressing and thermally induced phase separation respectively, were mechanically characterized at both the macroscale and nanoscale by tensile tests and indentation-type atomic force microscopy. All tests were conducted in wet state with the final aim of simulating scaffold real operating conditions. The films showed two distinct Young Moduli populations, which can be ascribed to polyurethane hard and soft segments. In the scaffold, the application of a thermal cooling gradient during phase separation was responsible for a nanoscale polymer chain organization in a preferred direction. At the macroscale, the porous matrices showed a Young Modulus of about 1.5 MPa in dry condition and 0.3 MPa in wet state. The combination of nanoscale and macroscale values as well as the aligned structure are in accordance with stiffness and structure required for scaffolds used for the regeneration of soft tissues such as muscles. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A, 2014.

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Neural interfaces with the peripheral nervous system have been developed to provide a direct communication pathway between peripheral nerves and prosthetic limbs. This study reports a regenerated peripheral nervous system which can control the reinnervated muscles and interpret neurological signals. The acquired bioelectrical signals can be used for the interpretation of mind which will be used to monitor prosthetic limbs. Transected nerves were regenerated through PDMS scaffolds and transferred signals through embedded microwires and acquisition systems.

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In this study, the in vitro release of proteins from novel, biodegradable phase-separated poly(ε-caprolactone-PEG)-block-poly(ε-caprolactone), [PCL-PEG]-b-[PCL]) multiblock copolymers with different block ratios and with a low melting temperature (49–55 °C) was studied. The effect of block ratio and PEG content of the polymers (i.e. 22.5, 37.5 and 52.5 wt%) as well as the effect of protein molecular weight (1.2, 5.8, 14, 29 and 66 kDa being goserelin, insulin, lysozyme, carbonic anhydrase and albumin, respectively) on protein release was investigated. Proteins were spray-dried with inulin as stabilizer to obtain a powder of uniform particle size. Spray-dried inulin-stabilized proteins were incorporated into polymeric implants by hot melt extrusion. All incorporated proteins fully preserved their structural integrity as determined after extraction of these proteins from the polymeric implants. In general, it was found that the release rate of the protein increased with decreasing molecular weight of the protein and with increasing the PEG content of the polymer. Swelling and degradation rate of the copolymer increased with increasing PEG content. Hence, release of proteins of various molecular weights from [PCL-PEG]-b-[PCL] multi-block copolymers can be tailored by varying the PEG content of the polymer.

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Nerve guide scaffolds from block polyurethanes without any additional growth factors or protein were prepared using a particle leaching method. The scaffolds of block polyurethanes (abbreviated as PUCL-ran-EG) based on poly(ɛ-caprolactone) (PCL-diol) and poly(ethylene glycol) (PEG) possess highly surface-area porous for cell attachment, and can provide biochemical and topographic cues to enhance tissue regeneration. The nerve guide scaffolds have pore size 1–5 μm and porosity 88%. Mechanical tests showed that the polyurethane nerve guide scaffolds have maximum loads of 4.98 ± 0.35 N and maximum stresses of 6.372 ± 0.5 MPa. The histocompatibility efficacy of these nerve guide scaffolds was tested in a rat model for peripheral nerve injury treatment. Four types of guides including PUCL-ran-EG scaffolds, autograft, PCL scaffolds and silicone tubes were compared in the rat model. After 14 weeks, bridging of a 10 mm defect gap by the regenerated nerve was observed in all rats. The nerve regeneration was systematically characterized by sciatic function index (SFI), histological assessment including HE staining, immunohistochemistry, ammonia silver staining, Masson's trichrome staining and TEM observation. Results revealed that polyurethane nerve guide scaffolds exhibit much better regeneration behavior than PCL, silicone tube groups and comparable to autograft. Electrophysiological recovery was also seen in 36%, 76%, and 87% of rats in the PCL, PUCL-ran-EG, and autograft groups respectively, whilst 29.8% was observed in the silicone tube groups. Biodegradation in vitro and in vivo show proper degradation of the PUCL-ran-EG nerve guide scaffolds. This study has demonstrated that without further modification, plain PUCL-ran-EG nerve guide scaffolds can help peripheral nerve regeneration excellently.

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Co-polymers of lactide and glycolide, referred to as PLGA, have generated tremendous interest because of their excellent biocompatibility, biodegradability and mechanical strength. Various polymeric devices like  microspheres, micro capsules, nanoparticles, pellets, implants, and films have been fabricated using these polymers. They can be transformed by spinning into filaments for subsequent fabrication of desirable textile  structures. Spinning may be accomplished by various routes. The fibers may be fabricated into various forms and may be used for implants and other surgical applications such as sutures. They are also easy to formulate into various delivery systems for carrying a variety of drug classes. The present article presents a review on the production of PLGA fiber by various methods, along with correlations between structure and  properties of the fibers. The applications of these fibers in biomedical domains are also discussed. 
 

Nerve injuries may occur due to trauma, tumor removal, and accidental surgical resection. Rodents are the most common pre-clinical nerve defect models; however, accelerated regeneration of the damaged peripheral nerves in rodents and inability to investigate large gaps are major limitations for the rodent model, making large animal models necessary. The purpose of this project is to identify key considerations in developing a non-human primate (NHP) large-gap peripheral nerve model, as well as to provide an interim analysis of our first set of NHPs.

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Peripheral nerve regeneration can be enhanced by chemical and mechanical cues for neurite growth. Aligned and randomly oriented electrospun nanofibers of poly(ε-caprolactone) (PCL) or a blend of PCL and elastin were fabricated to test their potential to provide contact guidance to embryonic chick dorsal root ganglia for peripheral nerve regeneration. Scanning electron microscopy was used to analyze the fiber diameter. Fiber diameter was found to be significantly smaller when elastin was incorporated into the scaffold (934 ± 58 nm for PCL and 519 ± 36 nm for PCL:elastin). After 24 h in culture, there was preferential cell attachment and neurite extension along the fibers of the elastin-containing scaffolds (average neurite extension 173.4 ± 20.7 μm), indicating that the presence of elastin promotes neurite outgrowth on electrospun scaffolds.

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(Nanowerk News) Damage to the peripheral nervous system, usually caused by serious accidents, can lead to loss of motor control and sensory perception. This is a very serious injury with grave consequences for the lives of thousands of people of all ages. Peripheral nerve injuries are responsible for over a million medical consultations every year in the USA and Europe, of which over 10% end up in the operating theatre. The physical impairments resulting from this injury are caused by the lack of connections between the nerve cells owing to the severing of the nerve.

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