Electrohydrodynamic Atomization Research Articles

Internal and external hydrodynamics of Taylor cone under constant and alternating voltage actuation

Electrohydrodynamic atomization (EHDA) is carried out in the Taylor cone mode for generating unimodal particle distribution, which can be achieved by either constant voltage actuation (CVA) or alternating voltage actuation (AVA). The present study reports an experimental investigation of the flow field both inside and outside the Taylor cone using light sheet fluorescence imaging and time-resolved particle image velocimetry measurements. Liquid ethanol is used as the working fluid and the amplitude of both constant and alternating electric potential difference is set at the same value, i.e., VC=VA=5.2 kV with an actuation frequency of 200 Hz in the case of alternating EHDA. The hydrodynamic behavior both inside and outside the Taylor cone is presented for the first time. The flow field measurements demonstrate meridional circulation from the nozzle exit toward the apex of the Taylor cone along the generatrix followed by flow from the apex of the Taylor cone along the central axis. A symmetric toroidal vortex is observed inside the Taylor cone in the case of CVA and an asymmetric toroidal vortex is observed for AVA. The flow field shows streamline-like flow in the ambient medium from the nozzle toward the ground electrode along the interface of the Taylor cone jet for CVA. In contrast, two vortical structures are observed around the apex of the Taylor cone for AVA. The velocity profile near the liquid–air interface of the Taylor cone indicates no direct correlation between the flow field inside the Taylor cone with the flow of the ambient medium. This difference may be attributed to the corona wind generated due to asymmetric electrode configuration. The unsteady flow field generated by alternating EHDA has great potential for enhanced heat transfer using spray cooling.

Tribological properties of PTFE/PPS films deposited on the ultrasonic rolling textured substrates by electrohydrodynamic atomization under dry reciprocating sliding

The combination of texturing pretreatments and lubricant films was researched to improve the dry friction and wear performance of aluminium alloys. Three linear microtextures with different spacings were fabricated on the aluminum alloy substrates by ultrasonic surface rolling processing (USRP). The surface characteristics of different microtextures, such as micromorphologies, hardnesses, and wettability, were tested. PTFE/PPS lubricant films were prepared onto the textured surfaces by electrohydrodynamic atomization (EHDA), and micromorphologies of the films were observed. The friction and wear performance of aluminum alloy substrate and the films with texturing pretreatments were tested by ball-on disk reciprocating sliding dry friction experiments, and the countball material was 316L steel. The test data indicated that all films effectively reduced the friction coefficient of the substrate surface, and among them, the film sample URTC100 with a combination of 100 μm spacing texture and PTFE/PPS film exhibited the best effect of anti-wear while dry reciprocating sliding. Compared to the unpretreated film sample, URTC100 increased the wear life by 10% and reduced the wear track width and adhesion width by 35% and 25%, respectively.

Varicose-whipping instabilities transition of an electrified micro-jet in electrohydrodynamic cone-jet regime

A cone-jet regime in electrohydrodynamic atomization (EHDA) is widely applied into printing, electro-spinning, spray-coating, and biological mass spectrometry. Regulating different instabilities of jet is crucial for optimizing its operating parameters. In present work, an atypical, hemispherical capillary with inner diameter of 0.40 mm and cap size of 6.20 mm was employed as atomization nozzle, through which a steady cone-jet regime was confirmed versus suitable feeding liquid flow rate and electric potential. A permanent and highly charged jet emits from a Taylor cone apex and further disintegrates into fine highly charged drops in the form of varicose or whipping instabilities. The results indicate that a steady cone-jet is observed in the specific ranges of the feeding liquid flow rate, electric potential and conductivity. The typical breakup instabilities including varicose and whipping are clearly observed with an increase in liquid flow rate for a fixed electric potential for most of liquids, and the transition from varicose to whipping instability easily occurs. For a steady cone-jet, the jet breakup instabilities usually depends on the competition between interfacial forces on the electrified jet. The transition process involving a low-viscosity jet with a large flow rate is observed, and the general parameter G=Γ2δμ0.52 is calculated to account for surface charge, surface tension, and viscosity effects, where Γ is the electric force to surface tension ratio and δμ is the inertia to viscous force ratio. Finally, the varicose, transition regime, and whipping are classified with first and second critical threshold values G = 40 and G = 102, respectively. Meanwhile, as the electrified jet transforms from varicose to whipping instabilities, the jet breakup length shows a trend of increasing first and then decreasing.

Resveratrol-Loaded Levan Nanoparticles Produced by Electrohydrodynamic Atomization Technique.

Considering the significant advances in nanostructured systems in various biomedical applications and the escalating need for levan-based nanoparticles as delivery systems, this study aimed to fabricate levan nanoparticles by the electrohydrodynamic atomization (EHDA) technique. The hydrolyzed derivative of levan polysaccharide from Halomonas smyrnensis halophilic bacteria, hydrolyzed Halomonas levan (hHL), was used. Nanoparticles were obtained by optimizing the EHDA parameters and then they were characterized in terms of morphology, molecular interactions, drug release and cell culture studies. The optimized hHL and resveratrol (RS)-loaded hHL nanoparticles were monodisperse and had smooth surfaces. The particle diameter size of hHL nanoparticles was 82.06 ± 15.33 nm. Additionally, release of RS from the fabricated hHL nanoparticles at different pH conditions were found to follow the first-order release model and hHL with higher RS loading showed a more gradual release. In vitro biocompatibility assay with human dermal fibroblast cell lines was performed and cell behavior on coated surfaces was observed. Nanoparticles were found to be safe for healthy cells. Consequently, the fabricated hHL-based nanoparticle system may have potential use in drug delivery systems for wound healing and tissue engineering applications and surfaces could be coated with these electrosprayed particles to improve cellular interaction.

Nanostructured Valsartan Microparticles with Enhanced Bioavailability Produced by High-Throughput Electrohydrodynamic Room-Temperature Atomization

The high-throughput drying and encapsulation technique called electrospraying assisted by pressurized gas (EAPG) was used for the first time to produce nanostructured valsartan within microparticles of excipients. Valsartan, a poorly absorbed and lipid-soluble drug, was selected since it is considered a good model for BCS class II drugs. Two different polymeric matrices were selected as excipients, i.e., hydroxypropyl methylcellulose (HPMC) and lactose monohydrate, while Span 20 was used as a surfactant. The produced 80% valsartan loading formulations were characterized in terms of morphology, crystallinity, in vitro release, in vitro Caco-2 cells’ permeability, and in vivo pharmacokinetic study. Spherical microparticles of ca. 4 μm were obtained within which valsartan nanoparticles were seen to range from 150 to 650 nm. Wide-angle X-ray scattering and differential scanning calorimetry confirmed that valsartan had a lower and/or more ill-defined crystallinity than the commercial source, and photon correlation spectroscopy and transmission electron microscopy proved that it was dispersed and distributed in the form of nanoparticles of controlled size. In vitro dissolution tests showed that the HPMC formulation with the lowest API particle size, i.e., 150 nm, dissolved 2.5-fold faster than the commercial valsartan in the first 10 min. This formulation also showed a 4-fold faster in vitro permeability than the commercial valsartan and a 3-fold higher systemic exposure than the commercial sample. The results proved the potential of the EAPG processing technique for the production of safe-to-handle microparticles containing high quantities of a highly dispersed and distributed nanonized BCS class II model drug with enhanced bioavailability.

Assembling Hybrid Energetic Materials with Controllable Interfacial Microstructures by Electrospray.

Constructing hybrid energetic materials (HEMs) consisting of nanothermites and organic high explosives is an efficient strategy to regulate the reactivity of energetic composites. To investigate the role of interfacial microstructures in determining the reactivity of HEMs, we employ electrospray, one ramification of electrohydrodynamic atomization, to assemble Al/CuO and hexanitrohexaazaisowurtzitane (CL-20) into composites with various morphologies from different solvent systems. The morphology and compositional information of the assembled clay-like or granular HEMs, which are obtained from ketone, ester, or mixtures of alcohol and ether, are confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The phase transition of CL-20 due to the fast evaporation of charged droplets and insufficient time for recrystallization is studied by Fourier transform infrared spectroscopy (FTIR). Thermogravimetric-differential scanning calorimetry (TG-DSC) is applied to investigate the thermodynamic behaviors and synergistic effect of the nanothermite and high explosive. Enhancements in combustion performance and pressurization characteristics of the as-sprayed HEMs have been observed through open burn tests and pressure cell tests. Granular HEMs show high gas generation and high pressurization rate, while nitrocellulose (NC) fibers existing in the clay-like HEMs would weaken the reactivity to a certain extent. HEMs obtained from the mixture of n-propanol and diethyl ether, in which nano-CL-20 exists as independent particles rather than a matrix, exhibit high gas generation but low pressurization rate. The results indicate that the energy releasing performance of the prepared HEMs can be readily regulated by constructing various interfacial microstructures to satisfy the broad requirements of energy sources.

An Overview on Atomization and Its Drug Delivery and Biomedical Applications

Atomization is an intricate operation involving unstable and complex networks with rupture and fusion of liquid molecules. There are diverse details that typify the spray formation, which are the technique and configuration of the atomization process, dimension and structure of the nozzle, experimental parameters, etc. Ultimately, the process generates fine sprays from the bulk of a liquid. Some examples of atomization that we come across in our day-to-day life are antiperspirant or hair spray, shower head, garden sprinkler, or cologne mist. In this review paper we are briefly discussing the theoretical steps taking place in an atomization technique. The instabilities of the jet and sheet are explained to understand the underlying theory that breaks the jet or sheet into droplets. Different types of atomization processes based on the energy sources are also summarized to give an idea about the advantages and disadvantages of these techniques. We are also discussing the various biomedical applications of the electrohydrodynamic atomization and its potential to use as a drug delivery system. In short, this paper is trying to demonstrate the diverse applications of atomization to show its potency as a user friendly and cost-effective technique for various purposes.

Electrohydrodynamic atomisation driven design and engineering of opportunistic particulate systems for applications in drug delivery, therapeutics and pharmaceutics.

Electrohydrodynamic atomisation (EHDA) technologies have evolved significantly over the past decade; branching into several established and emerging healthcare remits through timely advances in the engineering sciences and tailored conceptual process designs. More specifically for pharmaceutical and drug delivery spheres, electrospraying (ES) has presented itself as a high value technique enabling a plethora of different particulate structures. However, when coupled with novel formulations (e.g. co-flows) and innovative device aspects (e.g., materials and dimensions), core characteristics of particulates are manipulated and engineered specifically to deliver an application driven need, which is currently lacking, ranging from imaging and targeted delivery to controlled release and sensing. This demonstrates the holistic nature of these emerging technologies; which is often overlooked. Parametric driven control during particle engineering via the ES method yields opportunistic properties when compared to conventional methods, albeit at ambient conditions (e.g., temperature and pressure), making this extremely valuable for sensitive biologics and molecules of interest. Furthermore, several processing (e.g., flow rate, applied voltage and working distance) and solution (e.g., polymer concentration, electrical conductivity and surface tension) parameters impact ES modes and greatly influence the production of resulting particles. The formation of a steady cone-jet and subsequent atomisation during ES fabricates particles demonstrating monodispersity (or near monodispersed), narrow particle size distributions and smooth or textured morphologies; all of which are successfully incorporated in a one-step process. By following a controlled ES regime, tailored particles with various intricate structures (hollow microspheres, nanocups, Janus and cell-mimicking nanoparticles) can also be engineered through process head modifications central to the ES technique (single-needle spraying, coaxial, multi-needle and needleless approaches). Thus, intricate formulation design, set-up and combinatorial engineering of the EHDA process delivers particulate structures with a multitude of applications in tissue engineering, theranostics, bioresponsive systems as well as drug dosage forms for specific delivery to diseased or target tissues. This advanced technology has great potential to be implemented commercially, particularly on the industrial scale for several unmet pharmaceutical and medical challenges and needs. This review focuses on key seminal developments, ending with future perspectives addressing obstacles that need to be addressed for future advancement.

Evaluation of cell compatibility of surfaces patterned with hydroxyapatite nanopowders on Ti surfaces

Hydroxyapatite (HA) is a widely used biomaterial for coatings on prostheses, which is used to repair, replace and restore the function of traumatized or diseased bone. In the present study, template-assisted electrohydrodynamic atomization (TAEA) was used to pattern Ti surfaces (convex, concave and flat) with different HA nanoparticles, in order to evaluate the cellular responses. A comparison of biocompatibility between surfaces coated with locally prepared (SL) and commercially available HA nanopowders was carried out. The cytotoxicity and cellular responses to these substrates (i.e., cell adhesion, morphology and proliferation) were evaluated using human osteoblast-like cells (HOS) in vitro. The results demonstrate that Ti surfaces coated with HA (SL) and commercial HA supported HOS cell attachment and proliferation without eliciting any deleterious substances. Moreover, retention of cell viability and morphology of osteoblast-like cells were observed once cells were in contact with the surfaces and were comparable to that of the tissue culture control. Interestingly, cells attached to HA (SL) elicited a better response. Proliferation of cells on convex surfaces was relatively higher in comparison to that of the concave and flat surfaces, which could be due to increased surface area of the HA (SL).

Electrospray propelled by ionic wind in a bipolar system for direct delivery of charge reduced nanoparticles

We present a conceptual design to generate and deliver nanoparticles in one unique system based on electrohydrodynamic atomisation (EHDA) without the restriction of the collector. The present EHDA bipolar configuration consists of a capillary nozzle and a pin, both act as emitters and as the reference electrodes of each other. Under an applied voltage, the capillary nozzle sprays droplets while the pin generates ion wind via corona discharge. During spraying process, droplets’ charge is significantly reduced by interacting with counter ions and propelled away from the electrodes by the momentum of ion winds accumulated from corona discharge. Thus, the present technique can yield promising applications in effective respiratory delivery of nanomedicine.

One-Step All-Aqueous Interfacial Assembly of Robust Membranes for Long-Term Encapsulation and Culture of Adherent Stem/Stromal Cells.

The therapeutic effectiveness and biological relevance of technologies based on adherent cells depend on platforms that enable long-term culture in controlled environments. Liquid-core capsules have been suggested as semipermeable moieties with spatial homogeneity due to the high mobility of all components in their core. The lack of cell-adhesive sites in liquid-core structures often hampers their use as platforms for stem cell-based technologies for long-term survival and cell-directed self-organization. Here, the one-step fast formation of robust polymeric capsules formed by interfacial complexation of oppositely charged polyelectrolytes in an all-aqueous environment, compatible with the simultaneous encapsulation of mesenchymal stem/stromal cells (MSCs) and microcarriers, is described. The adhesion of umbilical cord MSCs to polymeric microcarriers enables their aggregation and culture for more than 21 days in capsules prepared either manually by dropwise addition, or by scalable electrohydrodynamic atomization, generating robust and stable capsules. Cell aggregation and secretion overtime can be tailored by providing cells with static or dynamic (bioreactor) environments.

Visualization on electrified micro-jet instability from Taylor cone in electrohydrodynamic atomization

Abstract The cone-jet in electrohydrodynamic atomization has been widely applied into numerous industrial fields owing to micro-sized drops with narrow distribution and high charge. The electrified jet emits from a single capillary sheathed with quartz tube is visualized versus operating parameters and physical properties, and breakup instabilities are also discussed. The range of operating parameters for a steady cone-jet broadens, as well as the minimum flow rate. Taylor cone angle decreases with an increase in flow rate, while increases as electric potential increasing. The jet breakup length decreases with an increase in flow rate and conductivity, while increases as electric potential increasing. The diffusion angle increases as flow rate increasing, while decrease as electric potential and conductivity increasing. Much clearer whipping instabilities are observed with an increase in “electro-Weber” number and conductivity. The completion in disturbance or/and suppression from axial and radial stresses, drag force dominates the variation. Meanwhile, for a large flow rate, the transition from varicose instabilities to whipping instabilities is found. The whipping instabilities are clearly observed for high conductivity due to much more free ions in liquid. For much higher conductivity, an intermittent electrified jet appears and shows an umbrella plume, and breakup length sharply shortens.

Determination of the Operational Parameters for the Manufacturing of Spherical PVP Particles via Electrospray.

This work aims at bridging experimental and numerical approaches to determine the optimal operating parameters for the fabrication of well-shaped polyvinylpyrrolidone (PVP) particles via electrohydrodynamic atomization. Particular emphasis is given to the role of the PVP solution viscosity. Solutions of PVP at various concentrations dissolved in Dimethylformamide (DMF) were prepared and analyzed. Numerical simulation using a coupled electro-CFD model was used to determine the ranges of experimental flow rate and the voltage, ensuring that well-shaped spherical particles are produced. It was deduced that the optimal combination of the parameters (flow rate, voltage, and polymer concentration) can be well approximated by a scaling law. The established relationship allowed determination of a stability island that guarantees that the given polymer solution will form spherical particles. Analyzing morphology and sizes of the particles manufactured in the optimal parameters range, we show, among others, that the size of the PVP particles can be predicted as a function of the flow rate by a power scaling relationship.

Investigation of poly(lactic acid) nanocapsules containing the plant extract via coaxial electrospraying method for functional nonwoven applications

This study focuses on the development of functional nanocapsules via the coaxial electrohydrodynamic atomization (electrospraying) method. These nanocapsules can manipulate nonwoven surface functionality in terms of antibacterial characteristics for medical textile purposes. Electrosprayed nanocapsules were produced from Poly(lactic acid) (PLA) polymer and Plumbago europaea plant extract. Here, we employ optimized solution and process parameters (needle to collector distance, electrical field, application time, and needle dimension) for the coaxial electrospraying process. Different Plumbago europaea extract concentrations and co-fluids’ flow rates were investigated as part of the study. Also, the effect of these parameters on capsule morphology and dimension were investigated. After the formation of PLA nanocapsules, morphological and dimensional characteristics were analyzed through SEM, FESEM, TEM images in addition to FTIR and nanosize measurements. According to our findings, a lower co-fluids’ flow rate gives the smaller nanocapsules with narrow-sized distribution and desired spherical morphology. Antibacterial efficiency doesn’t show any significant difference except the lowest plant extract concentrations. After characterizing the nanocapsules’ structures, the core-sheath structure can be clearly identified. Consequently, the desired capsule morphology and size for nanocapsules were accomplished. The antibacterial efficiency of covered surfaces with nanocapsules is up to 80% for Staphylococcus aureus and about 31% for Escherichia coli, even with low pick-up ratios. Even for a very low amount of extract usage, good antibacterial efficiency can be achieved. The application has endless potential in terms of higher concentration and a wide range of chemical usage.

Development of Water-Soluble Electrospun Fibers for the Oral Delivery of Cannabinoids.

Cannabidiol (CBD) and cannabigerol (CBG) are two active pharmaceutical ingredients, derived from cannabis plant. In the present study, CBD and CBG were formulated with polyvinyl(pyrrolidone) (PVP) and Eudragit L-100, using electrohydrodynamic atomization (electrospinning). The produced fibers were smooth and uniform in shape, with average fiber diameters in the range of 700-900nm for PVP fibers and 1-5μm for Eudragit L-100 fibers. The encapsulation efficiency for both CB and CBG was high (over 90%) for all formulations tested. Both in vitro release and disintegration tests of the formulations in simulated gastric fluids (SGF) and simulated intestinal fluids (SIF) indicated the rapid disintegration and dissolution of the fibers and the subsequent rapid release of the drugs. The study concluded that the electrospinning process is a fast and efficient method to produce drug-loaded fibers suitable for the per os administration of cannabinoids.

A Robust Surface-Modified Separator Fabricated with Roll-to-Roll Atomic Layer Deposition and Electrohydrodynamic Deposition Techniques for High Temperature Lithium Ion Batteries

A multilayer separator is developed by the deposition of ultrathin polyvinylidene fluoride (PVDF) and aluminum oxide (Al2O3) layers on polyolefin separator using in-house designed novel roll-to-roll atmospheric atomic layer deposition (R2R-AALD) and electrohydrodynamic atomization (EHDA) methods. The conformal coatings of ultrathin PVDF (∼5 um) and Al2O3 (∼10 nm) layers form a highly uniform interconnect microporous structure, which enhances thermal stability and mechanical strength. The deposition of PVDF and Al2O3 layers also improves electrolyte wettability and electrolyte uptake (256%), which gives rise to ionic conductivity. The Al2O3/PVDF/Celgard separator shows excellent thermal stability with minimal shrinkage up to 180 °C and robust mechanical strength. The lithium cobalt oxide/graphite (LCO/graphite) cells based on as-developed multilayer separator deliver excellent discharge capacity of 130.9 mAh g−1 at 0.5 C after 150 cycles and capability of 99.6 mAh g−1 at 5 C after 100 cycles at room temperature. Moreover, the LCO/graphite cells with Al2O3/PVDF/Celgard separator also show remarkable cyclic performances at elevated temperatures. The as-developed separator proves to be a better candidate for high capacity lithium ion batteries, especially for high temperature conditions.

Fabrication of WS2/C composite coatings via electrohydrodynamic atomization and their tribology behaviours

WS2 coatings were prepared by electrohydrodynamic atomization method, and graphite was introduced in order to improve their mechanical properties and oxidation resistance. The influence of graphite on the microstructure, anti-oxidation capability, mechanical performances and tribological properties of the composite coatings were systematically analysed. The sharkskin-like biomimetic textures were fabricated on the substrates by laser machining. The results showed that the sharkskin-like biomimetic textures increased the compressive stresses and surface energies of substrates, resulting in improved adhesion strength between deposited coatings and substrates. The improved adhesion strength and oxidation resistance of the WS2/C coatings as well as the antifriction capability of micro/nano-textures aided in keeping a low stabilized friction coefficient down to 0.05 for a long sliding time. The WS2/C (4:1) composite coatings deposited on the sharkskin-like biomimetic textured substrates presented the longest wear life of ~2800 s, which was ~2.3 times longer than that of the pure WS2 coatings on the polished substrates. The wear rate of WS2/C (4: 1) coating deposited on the textured substrate was ~3.1 × 10−7 mm3/N mm, which was about three-fifths of that of the pure WS2 coating deposited on the polished substrate. The micro/nano-grooves, which acted as reservoirs for WS2 lubricating material, could support the formation of the low-friction tribo-films.

Experimental study on electrohydrodynamic atomization (EHDA) in stable cone-jet with middle viscous and low conductive liquid

The cone-jet is one of the most interesting means in electrohydrodynamic atomization (EHDA) for wide applications because of highly charged and monodisperse drops. The pulsating and stable cone-jet modes in EHDA of diethyleneglycol (DEG) are observed by means of high-speed photography technology, as well as the breakup modes transition of electrified jet from varicose to kink instability. The conductive liquid is driven to form a liquid cone at the outlet of the capillary tube, and form a permanent jet from the apex of the cone by the tangential electric stress. With an increase in electric potential, the cone angle and jet length increase. The electrified meniscus and the cone may appear convex, linear sides and concave in cone jet regime, which depends on the static equilibrium of forces exists at each point of electrified liquid surface. The jet breakup modes with multi-jet, varicose and kink instabilities are successively recorded as liquid flow rates increasing. The jet breakup transition depends on flow rate. The drops size rises proportionally with an increase in liquid flow rate or a decrease in electric potential in stable cone-jet mode. The dimensionless diameter d/d0 as a function of the dimensionless flow rate qV/qm is in good agreement with the universal scaling laws.

Novel antibiotic-loaded particles conferring eradication of deep tissue bacterial reservoirs for the treatment of chronic urinary tract infection

A significant proportion of urinary tract infection (UTI) patients experience recurrent episodes, due to deep tissue infection and treatment-resistant bacterial reservoirs. Direct bladder instillation of antibiotics has proved disappointing in treating UTI, likely due to the failure of infused antibiotics to penetrate the bladder epithelium and accumulate to high enough levels to kill intracellular bacteria. This work investigates the use of nitrofurantoin loaded poly(lactic-co-glycolic acid) (PLGA) particles to improve delivery to intracellular targets for the treatment of chronic UTI. Using electrohydrodynamic atomisation, we produced particles with an average diameter of 2.8 μm. In broth culture experiments, the biodegradable particles were effective against a number of UTI-relevant bacterial strains. Dye-loaded particles demonstrated that intracellular delivery was achieved in all cells in 2D cultures of a human bladder epithelial progenitor cell line in a dose-dependent manner, achieving far higher efficiency and concentration than equivalent quantities of free drug. Time-lapse video microscopy confirmed that delivery occurred within 30 min of administration, to 100% of cells. Moreover, the particles were able to deliver the drug to cells through multiple layers of a 3D human bladder organoid model causing minimal cell toxicity, displaying superior killing of bacterial reservoirs harboured within bladder cells compared with unencapsulated drug. The particles were also able to kill bacterial biofilms more effectively than the free drug. These results illustrate the potential for using antibiotic-loaded microparticles to effectively treat chronic UTIs. Such a delivery method could be extrapolated to other clinical indications where robust intracellular delivery is required, such as oncology and gene therapy.

Electrospinning/electrospraying coatings for metal microneedles: A design of experiments (DOE) and quality by design (QbD) approach

The research presented here shows QbD implementation for the optimisation of the key process parameters in electrohydrodynamic atomisation (EHDA). Here, the electrosprayed nanoparticles and electrospun fibers consisting of a polymeric matrix and dye. Eight formulations were assessed consisting of 5% w/v of polycaprolactone (PCL) in dichloromethane (DCM) and 5% w/v polyvinylpyrrolidone (PVP) in ethanol. A full factorial DOE was used to assess the various parameters (applied voltage, deposition distance, flow rate). Further particle and fiber analysis using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), particle/fiber size distribution. In addition to this in vitro release studied were carried out using fluorescein and Rhodamine B as model dyes and in vitro permeation studies were applied. The results show a significant difference in the morphology of resultant structures as well as a more rapid release profile for the PVP particles and fibers in comparison to the sustained release profiles found with PCL. In vitro drug release studies showed 100% drug release after 7 days for PCL particles and showed 100% drug release within 120 min for PVP particles. The release kinetics and the permeation study showed that the MN successfully pierced the membrane and the electrospun MN coating released a large amount of the loaded drug within 6 h. This study has demonstrated the capability of these robust MNs to encapsulate a diverse range drugs within a polymeric matrix giving rise to the potential of developed personalised medical devices.