Preparation of polymeric nanoparticles by novel electrospray nanoprecipitation

Polymeric nanoparticles have important applications in drug delivery, biotechnology, diagnostics and energy harvesting. We report a new technique named electrospray nanoprecipitation, which combines electrospray with agitated solvent displacement. The process enables one-step formation of polymeric nanoparticles <100 nm in size that are near-monodisperse with a diameter range significantly lower than could be obtained using either electrospray or agitated solvent displacement technique alone. Both reduction of polymer solution concentration and the addition of poly(vinyl alcohol) emulsifier in the water–non-solvent medium further reduce the average particle diameter. The technique provides an effective and straightforward method to further reduce the size range of near-monodisperse nanoparticles achievable in a single step, which can be readily adapted for reducing the achievable size range of core–shell structures using popular one-step encapsulation techniques such as coaxial electrospray. © 2014 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry

Nanostructured Biomaterials for Tissue Engineered Bone Tissue Reconstruction

Bone tissue engineering strategies are emerging as attractive alternatives to autografts and allografts in bone tissue reconstruction, in particular thanks to their association with nanotechnologies. Nanostructured biomaterials, indeed, mimic the extracellular matrix (ECM) of the natural bone, creating an artificial microenvironment that promotes cell adhesion, proliferation and differentiation. At the same time, the possibility to easily isolate mesenchymal stem cells (MSCs) from different adult tissues together with their multi-lineage differentiation potential makes them an interesting tool in the field of bone tissue engineering. This review gives an overview of the most promising nanostructured biomaterials, used alone or in combination with MSCs, which could in future be employed as bone substitutes. Recent works indicate that composite scaffolds made of ceramics/metals or ceramics/polymers are undoubtedly more effective than the single counterparts in terms of osteoconductivity, osteogenicity and osteoinductivity. A better understanding of the interactions between MSCs and nanostructured biomaterials will surely contribute to the progress of bone tissue engineering

Facile ceramic micro-structure generation using electrohydrodynamic processing and pyrolysis

Electrohydrodynamic processing of a pre-ceramic polymer solution (polysiloxane) was used to fabricate various micro-components. With a single needle experimental set-up, sub-micrometer fibers and millimeter-size porous capsules were produced, while using two co-axial needles further enhanced the shaping versatility of the process, leading to the formation of micro-tubes and sub-micrometer hollow capsules. The polymeric samples were cross-linked and then pyrolyzed at 1200°C in N2 producing ceramic micro-parts that retained the morphological features present in the components in the polymeric state

Application of Electrohydrodynamic Technology for Folic Acid Encapsulation

Folates are a group of vitamins vital for the growth and development of the central nervous system. Most of these natural derivatives of folic acid are prone to oxidation and are very sensitive towards heat, temperature, oxygen, and light. Encapsulation of folic acid within inert matrices of a polymer can improve its stability and stop its degradation by light and oxygen. Electrohydrodynamic (EHD) technology is capable of generating fine droplets ranging from micrometers to nanometers in diameter from the breakup of a jet depending on the flow rate and applied electrical potential difference. The aims of this study were to generate nano-sized particles of folic acid encapsulated in sodium alginate (Na alginate) using EHD technology and to study the effect of voltage and flow rate on particle size as well as the structure of the prepared particles. It was established that 40 mg/ml (Na alginate) concentration can be used in single jet EHD technology. However, only 10 mg/ml concentration furnished stable jetting at any applied voltage and flow rate. So, this concentration was utilized and used to encapsulate higher dosages of folic acid. It was observed that the optimum flow rate for obtaining spherical particles of uniform diameter (4.2 ± 1.2 μm) was 10 μl/min at a voltage of 12 kV. Upon drying, these particles acquired a diameter in the range of 50-200 nm and became less spherical in shape. As the folic acid concentration is increased from 1 to 10 mg/ml, the percentage yield of particles at a constant Na alginate concentration increased by over 10 % and the corresponding encapsulation efficiency doubled. FTIR spectroscopic studies revealed the presence of folic acid within Na alginate matrices and also no characteristic chemical interaction between them. It can be concluded from the above research findings that, at 10 mg/ml Na alginate concentration, 10 μl/min flow rate, and 12 kV voltage, a high amount of folic acid (5 mg/ml) can be encapsulated within Na alginate matrices, with high percentage yield (70 %) and loading capacity (96 %), generating non-spherical dried beads/particles of 90-150 nm in diameter. © 2012 Springer Science+Business Media, LLC

Application of Electrohydrodynamic Technology for Folic Acid Encapsulation

Folates are a group of vitamins vital for the growth and development of the central nervous system. Most of these natural derivatives of folic acid are prone to oxidation and are very sensitive towards heat, temperature, oxygen, and light. Encapsulation of folic acid within inert matrices of a polymer can improve its stability and stop its degradation by light and oxygen. Electrohydrodynamic (EHD) technology is capable of generating fine droplets ranging from micrometers to nanometers in diameter from the breakup of a jet depending on the flow rate and applied electrical potential difference. The aims of this study were to generate nano-sized particles of folic acid encapsulated in sodium alginate (Na alginate) using EHD technology and to study the effect of voltage and flow rate on particle size as well as the structure of the prepared particles. It was established that 40 mg/ml (Na alginate) concentration can be used in single jet EHD technology. However, only 10 mg/ml concentration furnished stable jetting at any applied voltage and flow rate. So, this concentration was utilized and used to encapsulate higher dosages of folic acid. It was observed that the optimum flow rate for obtaining spherical particles of uniform diameter (4.2 ± 1.2 μm) was 10 μl/min at a voltage of 12 kV. Upon drying, these particles acquired a diameter in the range of 50-200 nm and became less spherical in shape. As the folic acid concentration is increased from 1 to 10 mg/ml, the percentage yield of particles at a constant Na alginate concentration increased by over 10 % and the corresponding encapsulation efficiency doubled. FTIR spectroscopic studies revealed the presence of folic acid within Na alginate matrices and also no characteristic chemical interaction between them. It can be concluded from the above research findings that, at 10 mg/ml Na alginate concentration, 10 μl/min flow rate, and 12 kV voltage, a high amount of folic acid (5 mg/ml) can be encapsulated within Na alginate matrices, with high percentage yield (70 %) and loading capacity (96 %), generating non-spherical dried beads/particles of 90-150 nm in diameter. © 2012 Springer Science+Business Media, LLC

Novel electrically driven direct-writing methods with managed control on in-situ shape and encapsulation polymer forming

Electrospraying and electrospinning are amongst the common methods of forming polymeric micro- and nano-scaled structures using electrically driven polymer processing. Utilising a co-axial flow of materials has been successful in enabling encapsulated structures to be generated by these techniques. However, with both of these methods, including their respective co-axial forms, there is limited control over the deposition of the resultant structures. Recently, an electrically driven direct-writing method has been developed which is based upon the same fundamental principles, but with the ability to deposit and form structures in an ordered manner, which has previously been restricted largely to single needle flow processing. In this paper, using selected polymeric materials, we demonstrate two novel methods of this direct-write system. The first method shows how the shape of formed structures can be varied in-situ using a single needle flow direct-write process. Secondly, we demonstrate how co-axial flows can be utilised to write and form encapsulated structures. We envisage that while the use of electrospinning and electrospraying methods will continue to expand, these novel areas will offer much greater control over the forming of a plethora of micro- and nano-scaled structures and will be essential for topographic studies (e. g. of living cells), novel particle preparation methods, coatings and direct writing of polymeric biomaterials. © 2011 Springer-Verlag France