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Viral infections alone are a significant cause of morbidity and mortality worldwide and have a detrimental impact on global healthcare and socioeconomic development. The discovery of novel antiviral treatments has gained tremendous attention and support with the rising number of viral outbreaks. In this work, carbonaceous materials, including graphene nanoplatelets and graphene oxide nanosheets, were investigated for antiviral properties. The materials were characterised using scanning electron microscopy and transmission electron microscopy. Analysis showed the materials to be two‐dimensional with lateral dimensions ranging between 1 – 4 µm for graphene oxide, 110 ± 0.11nm for graphene nanoplatelets. Antiviral properties were assessed against a DNA virus model microorganism at concentrations of 0.5, 1.0 and 2.0 wt/v%. Both carbonaceous nanomaterials exhibited potent antiviral properties and gave rise to a viral reduction of 100% across all concentrations tested. Graphene oxide nanosheets were then incorporated into polymeric fibres and their antiviral behaviour was examined after 3 and 24 hours. A viral reduction of ~39% was observed after 24 hours of exposure. The research presented here showcases, for the first time, the antiviral potential of several carbonaceous nanomaterials, also included in a carrier polymer. These outcomes can be translated and implemented in many fields and devices to prevent viral spread and infection.

A one step approach to prepare hybrid nanoparticle embedded polymer fibres using pressurised gyration is presented. Two types of novel antimicrobial nanoparticles and poly(methylmethacrylate) polymer were used in this work. X-ray diffraction analysis of the nanoparticles revealed Ag, Cu and W are the main elements present in them. The concentration of the polymer solution and the nanoparticle concentration had a significant influence on the fibre diameter, pore size and morphology. Fibres with a diameter in the range of 6-20μm were spun using 20wt% polymer solutions containing 0.1, 0.25 and 0.5 wt% nanoparticles under 0.3MPa working pressure and a rotational speed of 36,000rpm. Continuous, bead-free fibre morphologies were obtained for each case. The pore size in the fibres varied between 36 and 300nm. Successful incorporation of the nanoparticles in polymer fibres was confirmed by energy dispersive x-ray analysis. The fibres were also gyrospun on to metallic discs to prepare filters which were tested for their antibacterial activity on a suspension of Pseudomonas aeruginosa. Nanoparticle loaded fibres showed higher antibacterial efficacy than pure poly(methylmethacrylate) fibres.

Advanced technologies have made a significant impact on the development of drug delivery systems over the last few years and are remodeling the future of therapeutic care of patients. In particular...

In this work, a simple microfluidic junction with a T geometry and coarse (200 μm diameter) capillaries was used to generate monodisperse microbubbles with an alginate polymer shell. Subsequently, these bubbles were used to prepare porous alginate films with good control over the pore structure. The lack of pore size, shape, and surface control in scalable forming of polymeric films is a major application-limiting drawback at present. Controlling the thinning process of the shell of the bubbles to tune the surface of the resulting structures was also explored. Films were prepared with nanopatterned surfaces by controlling the thinning of the bubble shell, with the aid of surfactants, to induce efficient bursting (fragmentation) of bubbles to generate nanodroplets, which become embedded within the film surface. This novel feature greatly expands and enhances the use of hydrophilic polymers in a wide range of biomedical applications, particularly in drug delivery and tissue engineering, such as studying cellular responses to different morphological surfaces.

The application of polymer fibers has rocketed to unimaginable heights in recent years and occupies every corner of our day-to-day life, from knitted protective textile clothes to buzzing smartphone electronics. Polymer fibers could be obtained from natural and synthetic polymers at a length scale from the nanometer to micrometer range. These fibers could be formed into different configurations such as single, core–sheath, hollow, blended, or composite according to human needs. Of these several conformations of fibers, core–sheath polymer fibers are an interesting class of materials, which shows superior physical, chemical, and biological properties. In core–sheath fiber structures, one of the components called a core is fully surrounded by the second component known as a sheath. In this format, different polymers can be applied as a sheath over a solid core of another polymer, thus resulting in a variety of modified properties while maintaining the major fiber property. After a brief introduction to core–sheath fibers, this review paper focuses on the development of the electrospinning process to manufacture core–sheath fibers followed by illustrating the current methodology and approaches to form them on a larger scale, suitable for industrial manufacturing and exploitation. Finally, the paper reviews the applications of the core–sheath fibers, in particular, recent studies of core–sheath polymer fibers in tissue engineering (nerve, vascular grafts, cardiomyocytes, bone, tendons, sutures, and wound healing), growth factors and other bioactive component release, and drug delivery. Therefore, core–sheath structures are a revolutionary development in the field of science and technology, becoming a backbone to many emerging technologies and novel opportunities.

Bacterial cellulose (BC) is cellulose produced by a few limited species of bacteria in given conditions. BC has many remarkable properties such as its attractive mechanical properties, water uptake ability and biocompatibility which makes it a very desirable material to be used for wound healing. Inherently due to these important properties, the material is very resistant to easy processing and thus difficult to produce into useful entities. Additionally, being rate limited by the dependency on bacterial production, high yield is difficult to obtain and thus secondary material processing is sought after. In this review, BC is explained in terms of synthesis, structure and properties. These beneficial properties are directly related to the material's great potential in wound healing where it has also been trialled commercially but ultimately failed due to processing issues. However, more recently there has been increased frequency in scientific work relating to BC processing into hybrid polymeric fibres using common laboratory fibre forming techniques such as electrospinning and pressurised gyration. This paper summarises current progress in BC fibre manufacturing, its downfalls and also gives a future perspective on how the landscape should change to allow BC to be utilised in wound care in the current environment.

Nanofibers featuring functional nanoassemblies show great promise as enabling constituents for a diverse range of applications in areas such as tissue engineering, sensing, optoelectronics, and nanophotonics due to their controlled organization and architecture. An infusion gyration method is reported that enables the production of nanofibers with inherent biological functions by simply adjusting the flow rate of a polymer solution. Sufficient polymer chain entanglement is obtained at Berry number > 1.6 to make bead-free fibers integrated with gold nanoparticles and proteins, in the diameter range of 117-216 nm. Integration of gold nanoparticles into the nanofiber assembly is followed using a gold-binding peptide tag genetically conjugated to red fluorescence protein (DsRed). Fluorescence microscopy analysis corroborated with Fourier transform infrared spectroscopy (FTIR) data confirms the integration of the engineered red fluorescence protein with the nanofibers. The gold nanoparticle decorated nanofibers having red fluorescence protein as an integral part keep their biological functionality including copper-induced fluorescence quenching of the DsRed protein due to its selective Cu+2 binding. Thus, coupling the infusion gyration method in this way offers a simple nanoscale assembly approach to integrate a diverse repertoire of protein functionalities into nanofibers to generate biohybrid materials for imaging, sensing, and biomaterial applications.

Food grade polymeric nanoparticles have the potential to play a key role in the future of active component delivery which is an essential characteristic of functional foods. For this potential to be realized, it is important to study both the loading and release characteristics of the encapsulated material from the particle matrix as a function of particle size, material properties and processing conditions. In this study, ethylcellulose nanoparticles encapsulating ethylvanillin as a model active component were prepared by electrohydrodynamic processing. The mean particle size varied between 45 and 85 nm and the polydispersity index between 16 and 34%. The loading capacity and encapsulation efficiency ranged between 67 and 81% and 71 and 84%, respectively. It was found that the release rate was a function of both the nanoparticle size and structure, and hence of the composition and processing conditions. FT-IR analysis demonstrated that there was no degradation of the encapsulated material during processing or whilst encapsulated within the particle. It was therefore concluded that electrohydrodynamic processing was a suitable method for producing nanoparticles that can be readily tailored for the encapsulation and controlled release of specific active components to engineer the functional characteristics of food products.

Solid polymer nanospheres with contrasting size and surface roughness were prepared using a V-shaped microfluidic junction device. Polymethysilsesquioxane (PMSQ) polymer dissolved separately in either methanol, or ethanol, or propanol or butanol was used, and the nanospheres produced were collected in distilled water at two different temperatures (23°C and 100°C). Each polymer solution together with a volatile liquid, perfluorohexane, was fed into the inlet channels of the microfluidic device. The process of nanosphere generation was recorded by high-speed camera imaging. Only PMSQ solutions of ethanol and propanol generated well-defined nanospheres. The influence of the solvents and the nanosphere collection temperature on nanosphere size distribution and surface roughness was assessed using scanning electron microscopy, which showed that solvent selection was crucial in tailoring the size distribution of the nanospheres and that the nanospheres collected at 100°C had a noticeably rougher surface. The temperature also helped to vary the size distribution of the nanospheres. Nanospheres containing Evans blue dye were also prepared, and those with a rough surface exhibited a very different dye release profile compared with those having a smooth surface. In fact, the release profile changes due to a size differential can be largely compensated for by having a rough surface.

Nanotechnology has become increasingly important in advancing the frontiers of many key areas of healthcare, for example, drug delivery and tissue engineering. To fully harness the many benefits of nanotechnology in healthcare, innovative manufacturing is necessary to mass produce nanoparticles and nanofibers, the two major types of nanofeatures currently sought after and of immense utilitarian value in healthcare. For example, nanoparticles are a key drug delivery enabler, the structural and mechanical mimicry are important attributes of nanofiber which are increasingly used as biomimetic agents.

Three antimicrobial nanoparticle types (AMNP0, AMNP1, and AMNP2) produced using the TesimaTM thermal plasma technology were investigated and their compositions were determined using a combination of analytical methods. Scanning electron micrographs provided the morphology of these particles with observed sizes ranging from 10 to 50 nm, whilst FTIR spectra confirmed the absence of polar bonds and organic impurities, and strong Raman active vibrational bands at ca. 1604 and 1311 cm-1 ascribed to C-C vibrational motions were observed. Carbon signals that resonated at δC 126 ppm in the solid state NMR spectra confirmed that sp² hybridised carbons were present in high concentration in two of the nanoparticle types (AMNP1 and AMNP2). X-ray powder diffraction suggested that AMNP0 contains single phase Tungsten carbide (WC) in a high state of purity and multiple phases of WC/WC1-x were identified in both AMNP1 and AMNP2. Finally, X-ray photoelectron spectral (XPS) analyses revealed and quantified the elemental ratios in these composite formulations.

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

The encapsulation process has been studied to develop smart drug delivery systems for decades. In particular, micro-encapsulation and nano-encapsulation approaches have gained wide interest in the development of particulate drug delivery and achieved progress in specialties such as nano-medicine. Encapsulation technologies have evolved through various platforms including emulsion solvent evaporation, spray drying and polymer conjugation. Among current encapsulation methods, electrohydrodynamic and microfluidic processes stand out by enabling the making of formulations with uniform shape and nanoscale size. Pressurized gyration is a new method of combining rotation and controlled pressure to produce encapsulated structures of various morphologies. In this review we address key developments in electrohydrodynamic, microfluidic, their combined and new approaches as well as their potential to obtain combined therapies with desired drug release profiles.

Boron nitride nanoscrolls (BNSs) are open-ended, one-dimensional nanostructures made by the process of rolling boron nitride nanosheets into a scroll-like morphology. BNSs offer a high surface area to volume ratio and possess many unique properties (similar to carbon nanotubes, carbon nanoscrolls, and boron nitride nanotubes) such as high resistance to oxidation, chemical stability, increased lubrication, high-temperature resistance, electrical insulation, the ability to cap molecules inside and at the ends, and a wide bandgap regardless of chirality. Despite these attractive features and properties well suited for applications in biotechnology, energy storage, and electronics, the true potential of boron nitride and BNS as the next “miracle material” is yet to be fully explored. In this critical review, we assess, for the first time, various studies published on the formation and structural and dynamic characteristics of BNS; potential routes for BNS synthesis; and the toxicology of BNS. Finally, the future perspectives of BNS are discussed in view of its unique and exceptional candidacy for many (real-world) applications.

This work investigates the generation of monodisperse microbubbles using a microfluidic setup combined with electrohydrodynamic processing. A basic T-junction microfluidic device was modified by applying an electrical potential difference across the outlet channel. A model glycerol air system was selected for the experiments. In order to investigate the influence of the electric field strength on bubble formation, the applied voltage was increased systematically up to 21 kV. The effect of solution viscosity and electrical conductivity was also investigated. It was found that with increasing electrical potential difference, the size of the microbubbles reduced to ~25% of the capillary diameter whilst their size distribution remained narrow (polydispersity index ~1%). A critical value of 12 kV was found above which no further significant reduction in the size of the microbubbles was observed. The findings suggest that the size of the bubbles formed in the T-junction (i.e. in the absence of the electric field) is strongly influenced by the viscosity of the solution. The eventual size of bubbles produced by the composite device, however, was only weakly dependent upon viscosity. Further experiments, in which the solution electrical conductivity was varied by the addition of a salt indicated that this had a much stronger influence upon bubble size.

This study investigates the effect of print head design on the electrohydrodynamic printed resolution of silk fibroin. Needles with large orifices measuring at 800 μm were used to build five different print heads. The print heads were manufactured, tested, and optimized using four different silk fibroin solution concentrations of 10 wt.%, 15 wt.%, 20 wt.%, and 22 wt.% at applied voltages that ranged from 10 to 20 kV with two different flow rates of 1.5 μl/min and 2.0 μl/min. Each print head design behaved in a unique manner in terms of printed line characteristics as the flow rate, voltage and concentration were varied. The highest printed resolution of the order of 1 μm was achieved using the pinhole reservoir print head. Possible explanations for each of the observed behaviors and design criteria for future print heads are discussed.

Conventional fabrication techniques and structures employed in the design of silk fibroin (SF) based porous materials provide only limited control over pore size and require several processing stages. In this study, it is shown that, by utilizing electrohydrodynamic bubbling, not only can new hollow spherical structures of SF be formed in a single step by means of bubbles, but the resulting bubbles can serve as pore generators when dehydrated. The bubble characteristics can be controlled through simple adjustments to the processing parameters. Bubbles with diameters in the range of 240-1000 μm were fabricated in controlled fashion. FT-IR characterization confirmed that the rate of air infused during processing enhanced β-sheet packing in SF at higher flow rates. Dynamic mechanical analysis also demonstrated a correlation between air flow rate and film tensile strength. Results indicate that electrohydrodynamically generated SF and their composite bubbles can be employed as new tools to generate porous structures in a controlled manner with a range of potential applications in biocoatings and tissue engineering scaffolds.

Electrohydrodynamic (EHD) processing has attracted substantial interest in the technological and pharmaceutical sectors in recent years. Given the complexity of the process, exploring new ideas for EHD electrospraying and electrospinning delivery is a challenge. In this article, the design, construction and testing of a portable handheld EHD multi-needle device are described to produce multifunctional particles and fibers. Solid and encapsulated polymer particles and fibers were generated in order to study the performance of the device. The intrinsic properties of the feed solution/suspension and the processing conditions were adjusted to ensure robustness of the process and give uniform and reproducible products, with diameters ranging from the sub-micrometer scale to a few micrometers. These products have a broad range of applications in many advanced industrial sectors e.g. drug delivery systems, wound dressing patches, low calorie food products and cosmetics. © 2012 Elsevier B.V.

The preparation of capsules for medical and industrial use can be achieved via several conventional routes, yielding either hard or soft receptacles, depending on the type and the content of the material to be encapsulated. Together with tablets, capsules are amongst the most commonly used means of administering medication and this makes progress in capsule preparation technology a key area of drug delivery research. Here we uncover new technology for the preparation of capsules with porous chambers. The novelty is signified in the use of an electrohydrodynamic process engineering route and its potential is elucidated using a polymeric material; polymethylsilsesquioxane, which can be converted into an identical ceramic form by means of simple pyrolysis. Thus, both polymeric and ceramic capsules have been prepared. The effects of process control parameters such as the applied voltage and flow rate, on the characteristics of the capsules prepared are discussed.

The preparation of microbubble suspensions is an important feature of medical engineering research. Recently, co-axial electrohydrodynamic atomization was used in our laboratory for the first time to prepare microbubble suspensions. In this paper, using a model glycerol-air system, we investigate in detail the characteristics of this microbubbling process. Modes of microbubbling are elucidated with respect to applied voltage and liquid and air flow rates. Thus, a parametric plot is constructed to identify a liquid and gas flow rate regime, which allows continuous microbubbling. This map provides a basis for the selection of a suitable combination of liquid and gas flow rates particularly in relation to yield and bubble size. The mechanism of microbubbling in microfluidic systems is compared with that of microbubbling by co-axial electrohydrodynamic atomization to identify the advantages and the limiting factors of the latter. Stability of microbubbles prepared by this method in terms of variation of diameter as a function of time is compared with previous literature on the dissolution of microbubbles with an air core and suggests the need for further work to stabilize the bubbles.

Drug-delivery systems with a unique capability to respond to a given stimulus can improve therapeutic efficacy. However, development of such systems is currently heavily reliant on responsive polymeric materials and pursuing this singular strategy limits the potential for clinical translation. In this report, with a model system used for drug-release studies, we demonstrate a new strategy: how a temperature-responsive non-toxic, volatile liquid can be encapsulated and stored under ambient conditions and subsequently programmed for controlled drug release without relying on a smart polymer. When the stimulus temperature is reached, controlled encapsulation of different amounts of dye in the capsules is achieved and facilitates subsequent sustained release. With different ratios of the liquid (perfluorohexane): dye in the capsules, enhanced controlled release with real-time response is provided. Hence, our findings offer great potential for drug-delivery applications and provide new generic insights into the development of stimuli drug-release systems.

The release profile of a drug delivery system is a key factor in determining its efficacy. In the case of a polymeric particle based system, the release profile is a function of several parameters including particle diameter and porosity. The effects of these parameters are usually investigated experimentally using UV-spectroscopy. Predicting the drug release profile from particles as a result of the interaction of many parameters is desirable in order to facilitate the design of more efficient drug delivery particles. In this work, a quantitative method of determining the diffusion profile is developed which removes the need for repetitive experimentation. Particles of polymethylsilsesquioxane were prepared using coaxial electrohydrodynamic atomization and collected in solutions containing different concentrations of Evans blue dye (6, 0.6, and 0.06 mg/mL) which was used to simulate a drug. The dye release profile was calculated by solving the unsteady state diffusion equation for parameters used in the experiments. It was demonstrated that the dye release profile from particles with diameters ranging from 400 nm to 9 mum can be calculated using a simple equation without addition of a dissolution term, if the volume ratio of surrounding liquid to particle in the unsteady second order solution is substituted by the surface area of particles to liquid volume ratio. The calculated data are found to be in good agreement with the experimental, indicating that this method can be used to determine the diffusion coefficient as a function of particle diameter and material. This study represents a crucial step toward developing a full drug release model.

A method for generating poly(lactic-co-glycolic acid) and polycaprolactone biodegradable particles of different size and shape using a jet generated in an electric field is elucidated. These particles are suitable for use as drug carriers and the method can be developed into a mass production route. The effect of different parameters such as applied voltage, collecting distance, flow rate and polymer concentration on inducing size and shape differences in these particles was studied. It was found that the flow rate, polymer concentration and collecting distance have a significant impact on the size of the generated particles and by changing the collecting distance a systematic reduction in the particle size by at least an order of magnitude (10microm-100nm) can be achieved. By using a high polymer concentration (30 wt. %) the shape and surface morphology of these particles can also be controlled from spherical to fibrous, and smooth to irregular, respectively, which presently is an interesting strategy and concept in drug delivery. This method is very useful as a one-step generator of different sizes of drug carriers with morphological variations.

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.

Porous polymeric near-spherical capsules, ~ 3.6 mm in diameter, were prepared using an electrodydrodynamic process. These capsules were pyrolysed to porous ceramics, ~ 3 mm in diameter. The ceramic capsules had interconnected pores of ~ 1.3 μm in size, and large cells with a mean size of 28 μm. The larger pores resemble the cells in a typical ceramic foam and were evenly distributed throughout the structure. A large proportion of the ceramic capsules contained 65-70% porosity, and their compressive strength was 0.2-0.4 MPa. © 2008 Elsevier B.V. All rights reserved.

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.

It is a great privilege to put together a special double issue to honour Professor William Bonfield, CBE, FRS, FREng, FMedSci the founding editor of the Journal of the Royal Society Interface . Professor Bonfield is the internationally leading authority and prophet on bio- and medical materials. He

Surfactant-coated microbubbles are utilized in a wide variety of applications, from wastewater purification to contrast agents in medical ultrasound imaging. In many of these applications, the stability of the microbubbles is crucial to their effectiveness. Controlling this, however, represents a considerable challenge. In this study, the potential for stabilizing microbubbles using solid nanoparticles adsorbed onto their surfaces was explored. A new theoretical model has been developed to describe the influence of interfacially adsorbed solid particles upon the dissolution of a gas bubble in a liquid. The aim of this work was to test experimentally the prediction of the model that the presence of the nanoparticles would inhibit gas diffusion and coalescence/disproportionation, thus increasing the life span of the bubbles. Near-monodisperse microbubbles (~100 μm diameter) were prepared using a microfluidic device and coated with a surfactant, with and without the addition of a suspension of spherical gold nanoparticles (~15 nm diameter). The experimental results confirmed the theoretical predictions that as the surface concentration of gold nanoparticles increased the bubbles underwent negligible changes in their size and size distribution over a period of 30 days at the ambient temperature and pressure. Under the same conditions, bubbles coated with the same surfactant but no nanoparticles survived only a matter of hours.

In this paper we report a novel method, based on co-axial electrohydrodynamic jetting, for the preparation of microbubble suspensions containing bubbles

A novel V-junction microfluidic (VJM) device has been used to generate several types of particles from the break-up of bubbles. The flow rates of selected solutions and the gas pressure were adjusted in order to successfully generate monodisperse polymer coated microbubbles, which serve as a platform for particle generation. Uniform particles in both the nano and micro size ranges with different shapes were spontaneously generated from bubbles and have the potential to be used in several advanced technological applications. © 2012 Elsevier B.V. All rights reserved.

Poly(lactic-co-glycolic acid) (PLGA) microspheres containing celecoxib were prepared via electrospraying, and the influence of three processing parameters namely flow rate, solute concentration and drug loading, on the physico-chemical properties of the particles and the drug-release profile was studied. Microspheres with diameters between 2 and 8 μm were produced and a near-monodisperse size distribution was achieved (polydispersivity indices of 6–12%). Further, the inner structure of the particles showed that the internal porosity of the particles increased with increasing solvent concentration. X-ray powder diffraction (XRPD) analysis indicated that the drug was amorphous and remained stable after eight months of storage. Drug release was studied in USP 2 (United States Pharmacopeia Dissolution Apparatus 2) dissolution chambers, and differences in release profiles were observed depending on the parametric values. Changes in release rate were found to be directly related to the influence of the studied parameters on particle size and porosity. The results indicate that electrospraying is an attractive technique for producing drug-loaded microspheres that can be tailored towards an intended drug-delivery application. Compared with the more conventional spray-drying process, it provides better control of particle characteristics and less aggregation during particle formation. In particular, this study demonstrated its suitability for preparing capsules in which the drug is molecularly dispersed and released in a sustained manner to facilitate improved bioavailability.

In this paper we demonstrate a new synthetic method for the production of artificial magnetosomes i.e. lipid coated vesicles containing magnetic nanoparticles. Magnetosomes have considerable potential in biomedical and other nanotechnological applications but current production methods rely upon magnetotactic bacteria which limits the range of sizes and shapes that can be generated as well as the obtainable yield. Here we utilize electrohydrodynamic atomization to form nanoscale liposomes of tunable size followed by electroporation to transport iron into the nano-liposome core resulting in magnetite crystallisation. Using a combination of electron and fluorescence microscopy, dynamic light scattering, Raman spectroscopy and magnetic susceptibility measurements, we show that single-crystals of single-phase magnetite can be precipitated within each liposome, forming a near-monodisperse population of magnetic nanoparticles. For the specific conditions used in this study the mean particle size was 58 nm (±8 nm) but the system offers a high degree of flexibility in terms of both the size and composition of the final product.

It is well known that small biomaterial particles can lead to superior properties demanded by advanced applications in tissue engineering. Electrospraying has been considered as a promising approach to prepare fine particles, but reducing the particle size during such jetting process is always challenging. This is because the size of the as-sprayed particles is always limited by the device outlet diameter used. In the study we show that hydroxyapatite (HA) relics of 2 - 3 μm with low standard deviation can be deposited using a large nozzle (diameter of 1100 μm) only by reducing the nozzle tip angle from 90° to 15°. The mechanism of such phenomenon was extensively discussed, and a range of refined HA patterns were successfully prepared using the updated electrspraying configuration. We anticipate our findings to have a significant impact on the research of nanostructured biomaterials with superior properties which are realized by reducing the particle size using a greener electrically-driven processing technique.

Submicrometre size spheres prepared from biocompatible polymers are becoming increasingly popular in drug and gene delivery. This paper describes the preparation of polymeric spheres with a mean diameter of 0.4 μm with a polydispersivity index of 8%, using coaxial electrohydrodynamic atomization (CEHDA) microbubbling. An 18 wt.% solution of polymethylsilsesquioxane, a hydrophobic biocompatible polymer, was subjected to CEHDA microbubbling by passing air through the inner needle and polymer solution through the outer needle of a twin needle co-axial device, under the influence of an electric field. A parametric plot of the flow rate of air and the flow rate of polymer solution was constructed and used for systematic process control to reduce the diameter of the microspheres from micrometre size to submicrometre size. CEHDA is an excellent method for obtaining polymer microspheres. By studying the process in detail and mapping it, we can now demonstrate it can also be used to prepare submicrometre sized particles with the ability to control size and polydispersivity.

Nanometre hydroxyapatite (nHA) coated metallic materials have been successfully used for bone tissue implantation for several decades now due to its sound biological and mechanical properties. The microstructure and surface topography of the implant material are well-known to play a crucial role in influencing cellular responses to implants and bone tissue regeneration ultimately. Recently, a novel jet-based patterning technique, template-assisted electrohydrodynamic atomisation (TAEA) spraying, has been devised to prepare depositions with defined surface topography for guiding the cellular response. In this study, an improvement investigation of this patterning process was carried out to precisely control the nHA surface structure in terms of geographies and dimensions via an angular needle jetting during the patterning process. More importantly, the mechanism of such improvement of the TAEA patterning technique was also discussed and uncovered. A range of diverse nHA surface structures with high-resolution was therefore achieved, which paves the way for the research of the new generation implant materials with defined cellular response.

Air and 5 wt.-% BSA solution are used as a model system to generate protein-coated microbubbles, which are significantly smaller in diameter than the processing needle apertures. The effects of processing parameters (applied voltage and flow rate) on the bubble size distribution and stability are studied. The optimal processing conditions are also explored in terms of heating of the solutions and prepared structures. Both individual microbubbles and porous films were successfully prepared using this method which has significant potential for the preparation of microbubbles for drug delivery systems, porous coatings, thin films, scaffolds and ultrasound contrast agents. The versatile nature of the method implies that many macromolecules and other active agents can be used.

The exploration of nanocomposites has gained a strong research following over the last decade. These materials have been heavily exploited in several fields, with applications ranging from biosensors to biomedicine. Among these applications, great advances have been made in the field of microbiology, specifically as antimicrobial agents. This review aims to provide a comprehensive account of various nanocomposites that elucidate promising antimicrobial activity. The composition, physical and chemical properties, as well as the antimicrobial performance of these nanocomposites, are discussed in detail.

A recently developed electrohydrodynamic printing method is described that can be used to create ordered structures and complex patterns using coarse processing needles and two polymeric materials. The results highlight the method's potential for direct 3D writing of biomedical polymers and composites for a variety of biomedical applications.

Porous alginate films were prepared using a novel route in which alginate solutions of similar surface tensions but different viscosities were bubbled using a T-junction device to generate the films. The relationship between bubble size and bubbling conditions such as solution flow rate and air pressure was systematically investigated. The films obtained were characterized by optical microscopy, combined focused ion beam/scanning electron microscopy, and ultrasound reflection measurements. It is concluded that in a film, the thickness can be varied from 1-40 μm, where the minimum and maximum represent bubble-free and bubble-containing areas, respectively. Based on the characterization results obtained, a possible structure for the bubbles in the films is hypothesized. © 2010 Elsevier Ltd. All rights reserved.

A new deposition method is presented, based on electrospraying, that can build bioceramic structures with desirable surface properties. This technology allows nanoapatite crystals, including hydroxyapatite (nHA), carbonate-substituted HA (nCHA) and silicon-substituted HA (nSiHA), to be electrosprayed on glass substrates. Human osteoblast cells cultured on nSiHA showed enhanced cell attachment, proliferation and protein expression, namely alkaline phosphatase, type 1 collagen and osteocalcin, as compared to nHA and nCHA. The modification of nanoapatite by the addition of silicon into the HA lattice structure renders the electrosprayed surface more hydrophilic and electronegatively charged.

Template-assisted electrohydrodynamic atomisation (TAEA) spraying of nanometer-sized siliconsubstituted hydroxyapatite (nanoSiHA) was used to pattern implant surfaces for guided cell growth to improve the repair and regeneration of medical implants. A suspension of nanoSiHA was prepared and characterized. Patterns of pillars and tracks of various dimensions were prepared using the suspension. It was found that the resolution of the pattern was affected by TAEA processing parameters, such as applied voltage, flow rate, distance between needle and substrate, and spray time. Fifteen minutes spraying time provided the most clear and uniform patterned topography with a distance between nozzle and substrate of 50mm and a flow rate of 4?l/min. Therefore, well-defined nanoSiHA patterns can be achieved by TAEA deposition, it thus offers great potential for patterning the surface of medical implants.

A novel nanocomposite polymer with a polycarbonate soft segment (PCU) and polyhedral oligomeric silsesquioxanes (POSS) nanoparticle (POSS-PCU) has been selected for a synthetic heart valve due to its superior biocompatibility and in vivo biostability. However, the development of synthetic heart valves from polymeric materials requires an understanding of the basic mechanical and surface properties of the polymer. In this study, the mechanical properties of POSS-PCU, including tensile strength, tear strength and hardness, were tested and compared to control (PCU). The surface property was analyzed using contact angle measurement and the resistance to platelet adhesion was also investigated. POSS-PCU (hardness 84+/-0.8 Shore A) demonstrated significantly higher tensile strength 53.6+/-3.4 and 55.9+/-3.9Nmm(-2) at 25 and 37 degrees C, respectively) than PCU (33.8+/-2.1 and 28.8+/-3.4Nmm(-2) at 25 and 37 degrees C, respectively). Tensile strength and elongation at break of POSS-PCU was significantly higher than PCU at both 25 and 37 degrees C (P0.001). POSS-PCU showed a relatively low Young's modulus (25.9+/-1.9 and 26.2+/-2.0Nmm(-2)) which was significantly greater in comparison with control PCU (9.1+/-0.9 and 8.4+/-0.5Nmm(-2)) at 25 and 37 degrees C, respectively, with 100mum thickness. There was no significant difference (P0.05) in tear strength between POSS-PCU and PCU at 25 degrees C. However, tear strength increased significantly (P0.001) (at 37 degrees C) as the thickness increased from 100microm (51.0+/-3.3Nmm(-1)) to 200microm (63+/-1.5Nmm(-1)). The surface of POSS-PCU was significantly less hydrophilic than that of PCU.

A suspension of 15nm diameter gold nanoparti-cles has been deposited along a line on a silicon substrate with the assistance of a jet generated in an electric field. In order to control the evaporation of the solvent used to suspend the gold nanoparticles, a heating device was used to change the substrate temperature. Layer-by- layer deposition enabled the direct writing of gold tracks having an electrical resistivity of 1.8 × 10-7 Ωm, only about an order of magnitude above the electrical resistivity of bulk gold.

There is a critical clinical need for small-diameter bypass grafts, with applications involved in the coronary artery and lower limb. Commercially available materials give rise to unfavorable responses when in contact with blood and subjected to low-flow hemodynamics and, thus, are nonideal as small-diameter bypass grafts. Optimizing the mechanical properties to match both the native artery and the graft surfaces has received keen attention. Endothelialization of bypass grafts is considered a protective mechanism where the biochemicals produced from endothelial cells exert a range of favorable responses, including antithrombotic, noninflammatory responses and inhibition of intimal hyperplasia. In situ endothelialization is most desirable. Nanotechnology approaches facilitate all aspects of endothelialization, including endothelial progenitor cell mobilization, migration, adhesion, proliferation and differentiation. 'Surface nanoarchitecturing mechanisms', which mimic the natural extracellular matrix to optimize endothelial progenitor cell interaction and controlled delivery of various factors in the form of nanoparticles, which can be combined with gene therapy, are of keen interest. This article discusses the development of bypass grafts, focusing on the optimization of the biological properties of mechanically suitable grafts.

In this paper, we investigate in detail the electrohydrodynamic spraying of a nonbiodegradable nanocomposite polyhedral oligomeric silsesquioxane polymer developed in our laboratories and currently being explored for coating metallic stent materials. Different concentrations of the polymer have been dissolved to prepare, characterise, and electrohydrodynamically deposit the polymer on stainless steel. From the experiments, the solution containing 15 wt% polymer was selected for further investigation. The variation of film/ coating thickness as a function of spraying time was studied and the structural features of the film were assessed using microscopy. Films were also tensile tested. This study has identified a process and conditions which can be used in our stent coating research.

A monodisperse alcosol containing 0.1 wt. % 15 nm gold particles was subjected to controlled flow through a metal capillary exposed to an electric field at the ambient temperature to generate an electrohydrodynamic jet, which subsequently disintegrated into droplets. A silicon substrate was used to collect the droplets and prepare gold films. By varying the deposition time, we have prepared gold films in the thickness range of ∼500–∼ 2000 nm in a maximum spray time of 450 s. This is a significant achievement considering the initial concentration of gold and the spray time involved. The characteristics of the jet, droplets and films prepared were evaluated using advanced analytical techniques.

Topography of the surface plays an important role in cellular responses. A novel method, called template-assisted electrohydrodynamic atomization (TAEA) spraying, was developed to create surface topography of hydroxyapatite (HA) on metallic surfaces. In this work, by varying the core process parameters (e.g. flow rate, applied voltage and distance between substrate and needle), the optimization and development of the TAEA process with nanoHA suspension is investigated with the aim of preparing a nanostructured HA coating with patterning of high resolution for biomedical applications.

Fine nanoapatite relics were deposited on glass substrates by electrohydrodynamic atomisation, using nanohydroxyapatite (nHA), nano-carbonated hydroxyapatite (nCHA) and nanosilicon- substituted hydroxyapatite (nSiHA) suspensions. These electrosprayed nanoapatites were evaluated in-vitro using simulated body fluid (SBF) and human osteoblast (HOB) cells. The SBF study revealed that newly-formed apatite layers were observed on the surface of the relics. Furthermore, enhanced HOB cell growth was observed on each of the nanoapatites at all time points. Hence, this work demonstrated that electrosprayed nanoapatites offer considerable potential as biomaterials.

The ability to create patterns of bioactive nanomaterials particularly on metallic and other types of implant surfaces is a crucial feature in influencing cell response, adhesion and growth. In this report, we uncover and elucidate a novel method that allows the easy deposition of a wide variety of predetermined topographical geometries of nanoparticles of a bioactive material on both metallic and non-metallic surfaces. Using different mesh sizes and geometries of a gold template, hydroxyapatite nanoparticles suspended in ethanol have been electrohydrodynamically sprayed on titanium and glass substrates under carefully designed electric field conditions. Thus, different topographies, e.g. hexagonal, line and square, from hydroxyapatite nanoparticles were created on these substrates. The thickness of the topography can be controlled by varying the spraying time.