3D porous polyurethanes featured by different mechanical properties: Characterization and interaction with skeletal muscle cells

The fabrication of biomaterials for interaction with muscle cells has attracted significant interest in the last decades. However, 3D porous scaffolds featured by a relatively low stiffness (almost matching the natural muscle one) and highly stable in response to cyclic loadings are not available at present, in this context. This work describes 3D polyurethane-based porous scaffolds featured by different mechanical properties. Biomaterial stiffness was finely tuned by varying the cross-linking degree of the starting foam. Compression tests revealed, for the softest material formulation, stiffness values close to the ones possessed by natural skeletal muscles. The materials were also characterized in terms of local nanoindenting, rheometric properties and long-term stability through cyclic compressions, in a strain range reflecting the contraction extent of natural muscles. Preliminary in vitro tests revealed a preferential adhesion of C2C12 skeletal muscle cells over the softer, rougher and more porous structures. All the material formulations showed low cytotoxicity.

Polyurethane/58S bioglass nanofibers: synthesis, characterization, and in vitro evaluation

In this study, polyurethane nanofibers containing 5 and 10 wt% synthesized 58S bioglass were designed and fabricated by the electrospinning process.

In vitro biological and mechanical evaluation of various scaffold materials for myocardial tissue engineering

A cardiac patch is a construct devised in regenerative medicine to replace necrotic heart tissue after myocardial infarctions. The cardiac patch consists of a scaffold seeded with stem cells. To identify the best scaffold for cardiac patch construction we compared polyurethane, Collagen Cell Carriers, ePTFE, and ePTFE SSP1-RGD regarding their receptiveness to seeding with mesenchymal stem cells isolated from umbilical cord tissue. Seeding was tested at an array of cell seeding densities. The bioartificial patches were cultured for up to 35 days and evaluated by scanning electron microscopy, microscopy of histological stains, fluorescence microscopy, and mitochondrial assays. Polyurethane was the only biomaterial which resulted in an organized multilayer (seeding density: 0.750 × 10(6) cells/cm(2)). Cultured over 35 days at this seeding density the mitochondrial activity of the cells on polyurethane patches continually increased. There was no decrease in the E Modulus of polyurethane once seeded with cells. Seeding of CCC could only be realized at a low seeding density and both ePTFE and ePTFE SSP1-RGD were found to be unreceptive to seeding. Of the tested scaffolds polyurethane thus crystallized as the most appropriate for seeding with mesenchymal stem cells in the framework of myocardial tissue engineering.

Biodegradable paclitaxel-loaded microparticles prepared from novel block copolymers: influence of polymer composition on drug encapsulation and release

This study covers the preparation of microspheres for the controlled and targeted release of paclitaxel, using novel degradable polymers as carrier materials. Paclitaxel-loaded microspheres were prepared by oil-in-water single-emulsion solvent extraction/evaporation technique by using a series of polyurethanes and a block copolymer; the physicochemical properties of these polymers were modulated by changing nature and composition of their structural units. The obtained microparticles showed a regular morphology and properties (diameter: 1-100 µm; resuspension index: 18.8-100%; encapsulation efficiency: 26.6-97.2%) depending on polymer hydrophilicity and emulsifier used. In vitro release curves showed in all cases almost zero-order kinetics after an initial low burst effect (from 1 to 8.4%), which is required to minimize the drug side effects. This work also proposes a novel strategy to combine a controlled and a targeted release through the functionalization of the polymer matrix with peptide sequences. An RGD-functionalized polyurethane was used to successfully prepare paclitaxel-loaded microparticles. Studies on the preparation of polymer microspheres are reported.

Theory, fabrication and applications of microfluidic and nanofluidic biosensors

Biosensors are a broad array of devices that detect the type and amount of a biological species or biomolecule. Several different types of biosensors have been developed that rely on changes to mechanical, chemical or electrical properties of the transduction or sensing element to induce a measurable signal. Often, a biosensor will integrate several functions or unit operations such as sample extraction, manipulation and detection on a single platform. This review begins with an overview of the current state-of-the-art biosensor field. Next, the review delves into a special class of biosensors that rely on microfluidics and nanofluidics by presenting the underlying theory, fabrication and several examples and applications of microfluidic and nanofluidic sensors.

Indigenous customized sponge shunt for a recurrent brainstem cyst

BACKGROUND

Various treatment modalities are available for treatment of cystic lesions of the brainstem. However, cyst refilling and recurrences are very common. This article describes a young boy who presented with an intra-axial brainstem cyst following radiation for a pilocytic astrocytoma.

METHODS

The cyst was decompressed surgically once but it soon refilled. The use of a novel customized synthetic sponge acting as a shunt for the treatment of a cystic brainstem lesion is discussed. The sponge was fashioned like a dumbbell and inserted across the fenestration in the cyst wall.

RESULTS

The dumbbell design made it self-retaining. The characteristics of the sponge permitted continuous capillary drainage, with a low risk of occlusion. There was a dramatic decrease in the cyst size on follow-up scans, with resolution of clinical deficits.

CONCLUSIONS

A customized sponge shunt can serve as an easily available and effective internal shunt for intra-axial craniospinal cysts.

Feasibility, tailoring and properties of polyurethane/bioactive glass composite scaffolds for tissue engineering

This research work aims to propose highly porous polymer/bioactive glass composites as potential scaffolds for hard-tissue and soft-tissue engineering. The scaffolds were prepared by impregnating an open-cells polyurethane sponge with melt-derived particles of a bioactive glass belonging to the SiO(2)-P(2)O(5)-CaO-MgO-Na(2)O-K(2)O system (CEL2). Both the starting materials and the composite scaffolds were investigated from a morphological and structural viewpoint by X-ray diffraction analysis and scanning electron microscopy. Tensile mechanical tests, carried out according to international ISO and ASTM standards, were performed by using properly tailored specimens. In vitro tests by soaking the scaffolds in simulated body fluid (SBF) were also carried out to assess the bioactivity of the porous composites. It was found that the composite scaffolds were highly bioactive as after 7 days of soaking in SBF a HA layer grew on their surface. The obtained polyurethane/CEL2 composite scaffolds are promising candidates for tissue engineering applications.

A Polyurethane-Gelatin Hybrid Construct for Manufacturing Implantable Bioartificial Livers

A novel 3D hybrid construct was developed for liver manufacturing by depositing biodegradable polyurethane (PU) and a naturally derived polymer gelatin simultaneously via a double nozzle rapid prototyping (RP) technique. A grid object was produced by precisely and simultaneously dispersing the PU and gelatin to form 3D constructs with interconnected macro-channels at a low temperature (-28°C). Micro-pores were formed by freeze-drying the constructs. The PU polymer provided mechanical support while gelatin provided accommodation for implant cells. The hydrophilicity of the hybrid constructs was between the pure PU and pure gelatin structures. The interconnected channels allow nutrients and oxygen to be supplied throughout the construct as well as provide space for the attachment of cells. The design and fabrication strategies, used to create complex physical objects directly from computer aided design (CAD) models, represent a promising technique for implantable bioartificial livers. It is anticipated that these PU-gelatin hybrid constructs will serve as a useful model for bioartificial liver manufacturing.

Rapid Prototyping of Polyurethane for the Creation of Vascular Systems

A precise control over the internal architecture was essential for manufacture of complex organs. To create vascular systems that mimic human livers, we designed and fabricated complex 3D objects with an intrinsic network of interconnected channels. A new elastomeric polyurethane, mainly based on polycaprolactone and poly(ethylene glycol) with excellent biocompatibility and tunable biodegradation properties, was used to fabricate these vascular systems using a low temperature deposition system based on the layer-by-layer manufacturing principle. A specific model was selected via computer aided design (CAD), solid free form fabrication processes are conducted under computer direction. Two example object patterns were produced by precision controlled dispensing of a biodegradable polyurethane into 3D multi-micro-tunnels with multi-micro-pores at a low temperature (-28°C). The design and fabrication strategies used to create physical objects directly from CAD models represent a promising route for the establishment of complex organ vascular systems.