Biodegradable polyphosphazene-nanohydroxyapatite composite nanofibers: scaffolds for bone tissue engineering.

Bone is a natural composite comprised of hierarchically arranged collagen fibrils, hydroxyapatite and proteoglycans in the nanometer scale. This preliminary study reports the fabrication of biodegradable poly[bis(ethyl alanato)phosphazene]-nanohydroxyapatite (PNEA-nHAp) composite nanofiber matrices via electrospinning. Binary solvent compositions of THF and ethanol were used as a spinning solvent to attain better nanohydroxyapatite dispersibility in PNEA solution. These nanocomposites were characterized for morphology, nHAp distribution and content using spectroscopy and gravimetric estimations. Composite nanofibers fabricated in the diameter range of 100-310 nm could encapsulate 20-40 nm nHAp crystals. A better composite nanofiber yield was obtained for 50% (w/w) nHAp experimental loadings. Incremental experimental loading beyond 60% (w/w) hindered electrospinning due to polymer-nHAp phase separation. Composites nanofibers had a rougher surface and nodules along the length of the fibers suggesting nHAp encapsulation. Further, characterization via energy dispersive X-ray spectroscopy and X-ray mapping confirmed the nHAp encapsulation. Providing cells with a natural bone like environment with a fibrillar structure and natural hydroxyapatite can enhance bone tissue regeneration/repair.

A preliminary report on a novel electrospray technique for nanoparticle based biomedical implants coating: precision electrospraying.

The compatibility and biological efficacy of biomedical implants can be enhanced by coating their surface with appropriate agents. For predictable functioning of implants in situ, it is often desirable to obtain an extremely uniform coating thickness without effects on component dimensions or functions. Conventional coating techniques require rigorous processing conditions and often have limited adhesion and composition properties. In the present study, the authors report a novel precision electrospraying technique that allows both degradable and nondegradable coatings to be placed. Thin metallic slabs, springs, and biodegradable sintered microsphere scaffolds were coated with poly(lactide-co-glycolide) (PLAGA) using this technique. The effects of process parameters such as coating material concentration and applied voltage were studied using PLAGA and poly(ethylene glycol) coatings. Morphologies of coated surfaces were qualitatively characterized by scanning electron microscopy. Qualitative observations suggested that the coatings were composed of particles of various size/shape and agglomerates with different porous architectures. PLAGA coatings of uniform thickness were observed on all surfaces. Spherical nanoparticle poly(ethylene glycol) coatings (462-930 nm) were observed at all concentrations studied. This study found that the precision electrospraying technique is elegant, rapid, and reproducible with precise control over coating thickness (mum to mm) and is a useful alternative method for surface modification of biomedical implants.

Polymeric nanofibers as novel carriers for the delivery of therapeutic molecules.

Nanotechnology and nanoscience are relatively new technological endeavors that encompass the study, control, manipulation, and assembly of multifarious nanoscale components into materials, systems and devices to serve human interest and needs. Among the various currently used nanostructures for high technology applications polymeric nanofibers have received immense interest due to the ease of fabrication, controllable size/shape, and properties. Polymeric nanofibers have been extensively investigated for diversified applications, including filtration, barrier fabrics, wipes, personal care, biomedical, and pharmaceutical applications. This review mainly focuses on the fabrication of therapeutic agent loaded polymeric nanofibers and their controlled/sustained release behavior for the delivery of these active agents for various therapeutic applications. The nonwoven biodegradable polymeric nanofiber matrices are currently being reported as topical/local therapeutic agent delivery systems and as resorbable/biodegradable gauze for wound healing applications.

Fabrication and optimization of methylphenoxy substituted polyphosphazene nanofibers for biomedical applications.

Electrospinning has developed as a unique and versatile process to fabricate ultrathin fibers in the form of nonwoven meshes or as oriented arrays from a variety of polymers. The very small dimension of these fibers can generate a high surface area, which makes them potential candidates for various biomedical and industrial applications. The objective of the present study was to develop nanofibers from polyphosphazenes, a class of inorganic-organic polymers known for high biocompatibility, high-temperature stability, and low-temperature flexibility. Specifically, we evaluated the feasibility of developing bead-free nonwoven nanofiber mesh from poly[bis(p-methylphenoxy)phosphazene] (PNmPh) by electrospinning. The effect of process parameters such as nature of solvent, concentration of the polymer solution, effect of needle diameter, and applied potential on the diameter and morphology (beaded or bead-free) of resulting nanofibers were investigated. It was found that solution of PNmPh in chloroform at a concentration range of 7% (wt/v) to 9% (wt/v) can be readily electrospun to form bead-free fibers at room temperature. The mean diameter of the fibers obtained under optimized spinning condition was found to be approximately 1.2 microm. The bead-free, cylindrical nanofibers formed under the optimized condition showed a slightly irregular surface topography with indentations of a few nanometer scale. Further, the electrospun nanofiber mats supported the adhesion of bovine coronary artery endothelial cells (BCAEC) as well as promoted the adhesion and proliferation of osteoblast like MC3T3-E1 cells.

Development of novel tissue engineering scaffolds via electrospinning.

Electrospinning has recently been developed as an efficient technique to develop polymeric nanofibres. Various synthetic and natural biodegradable polymers have been electrospun into fibres with diameters in the nanometre range (< 1 microm). The fibre diameter, structure and physical properties of the nanofibre matrices can be effectively tuned by controlling various parameters that affect the electrospinning process. The dimension and structure of electrospun polymeric nanofibre mats resembles mostly the collagen phase of natural extracellular matrix. This, combined with excellent physical properties such as high surface area, high porosity, interconnective pores of the nanofibre matrices and appropriate mechanical properties, well-controlled degradation rates and biocompatibility of the base polymer, make biodegradable polymeric nanofibre matrices ideal candidates for developing scaffolds for tissue engineering. This article reviews the recent advances in the development of synthetic biodegradable nanofibre-based matrices as scaffolds for tissue engineering.