A critical survey of the laboratory test methods used to measure wicking is presented, and the four main methods are compared through application to a range of knitted fabrics produced from various fiber types. Correlation of the results indicates which combination of methods provides a meaningful assessment of fabric wicking properties in the context of clothing comfort studies. Observations on the wicking properties of various fiber types shows that wicking is often not inherent to the fiber, but is in part due to surfactants, such as spin finishes, which can be removed by washing.

Complex micro- and nano-structures enable crucial developments in the healthcare remit (e.g., pharmaceutical and biomaterial sciences). In recent times, several technologies have been developed and explored to address key healthcare challenges (e.g., advanced chemotherapy, biomedical diagnostics and tissue regeneration). Electrohydrodynamic atomization (EHDA) technologies are rapidly emerging as promising candidates to address these issues. The fundamental principle driving EHDA engineering relates to the action of an electric force (field) on flowing conducting medium (formulation) giving rise to a stable Taylor cone. Through careful optimization of process parameters, material properties and selection, nozzle and needle design, and collection substrate method, complex active micro- and nano-structures are engineered. This short review focuses on key selected recent and established advances in the field of pharmaceutical and biomaterial applications.

Despite exponential growth in research relating to sustained and controlled ocular drug delivery, anatomical and chemical barriers of the eye still pose formulation challenges. Nanotechnology integration into the pharmaceutical industry has aided efforts in potential ocular drug device development. Here, the integration and in vitro effect of four different permeation enhancers (PEs) on the release of anti-glaucoma drug timolol maleate (TM) from polymeric nanofiber formulations is explored. Electrohydrodynamic (EHD) engineering, more specifically electrospinning, was used to engineer nanofibers (NFs) which coated the exterior of contact lenses. Parameters used for engineering included flow rates ranging from 8 to 15μL/min and a novel EHD deposition system was used; capable of hosting four lenses, masked template and a ground electrode to direct charged atomised structures. SEM analysis of the electrospun structures confirmed the presence of smooth nano-fibers; whilst thermal analysis confirmed the stability of all formulations. In vitro release studies demonstrated a triphasic release; initial burst release with two subsequent sustained release phases with most of the drug being released after 24h (86.7%) Biological evaluation studies confirmed the tolerability of all formulations tested with release kinetics modelling results showing drug release was via quasi-Fickian or Fickian diffusion. There were evident differences (p<0.05) in TM release dependant on permeation enhancer.

Recently, remarkable efforts have focused on research towards enhancing and delivering efficacious and advanced therapeutic agents. Even though this involves significant challenges, innovative techniques and materials have been explored to overcome these. The advantageous properties of mesoporous silica nanoparticles (MSNs), such as unique morphologies and geometries, makes then favorable for use for various drug delivery targeting purposes, particularly in cancer therapy. As we discuss here, MSNs have been utilized over the past few decades to improve the efficiency of anticancer drugs by enhancing their solubility to render them suitable for application, reducing adverse effects, and improving their anticancer cytotoxic efficiency.

Advances in nanotechnology have enabled solutions for challenging drug delivery targets. While the eye presents numerous emerging opportunities for delivery, analysis and sensing; issues persist for conventional applications. This includes liquid phase formulation localisation on the ocular surface once administered as formulated eye-drops; with the vast majority of dosage (>90%) escaping from the administered site due to tear production and various drainage mechanisms. The work presented here demonstrates a single needle electrohydrodynamic (EHD) engineering process to nano-coat (as an on demand and controllable fiber depositing method) the surface of multiple contact lenses rendering formulations to be stationary on the lens and at the bio-interface. The coating process was operational based on ejected droplet charge and glaucoma drug timolol maleate (TM) was used to demonstrate surface coating optimisation, bio-surface permeation properties (flux, using a bovine model) and various kinetic models thereafter. Polymers PVP, PNIPAM and PVP:PNIPAM (50:50%w/w) were used to encapsulate the active. Nano-fibrous and particulate samples were characterised using SEM, FTIR, DSC and TGA to confirm structural and thermal stability of surface coated formulations. More than 52% of nano-structured coatings (for all formulations) were <200nm in diameter. In vitro studies show coatings to exhibit biphasic release profiles; an initial burst release followed by sustained release; with TM-loaded PNIPAM coating releasing most drug after 24h (89.8%). Kinetic modelling (Higuchi, Korsmeyer-Peppas) was indicative of quasi-Fickian diffusion whilst biological evaluation demonstrates adequate ocular tolerability. Results from permeation studies indicate coated lenses are ideal to reduce dosing regimen, which in turn will reduce systemic drug absorption. Florescent microscopy demonstrated probe and probe embedded coating behaviour from lens surface in vitro. The multiple lens surface coating method demonstrates sustained drug release yielding promising results; suggesting both novel device and method to enhance drug activity at the eyes surface which will reduce formulation drainage.

The work presented demonstrates an unconventional approach in the preparation of smart microneedle (MN) coatings utilising electrohydrodynamic atomisation (EHDA) principles. Stainless steel (600-900 µm in height) MNs were coupled to a ground electrode (in the EHDA coating set-up) with the deposition distance and collecting methodology varied for an ethanol:methanol (50:50) vehicle system. The preparation of nano- and micrometre-scaled pharmaceutical coatings was achieved. Fluorescein dye (serving as potential drug, sensory materials or disease state markers) and polyvinylpyrrolidone (PVP, polymer matrix system) formed the remaining components of the coating formulation. Based on these excipients and by varying the coating process, particles (100 nm to 3 µm) and fibres (400 nm to 1 µm) were deposited directly on MNs in controlled and selectable fashion (flow rates variable ∼ 5-50 µL/min, applied voltage variable 6-19 kV). These demonstrated options for multiple targeting and analysis applications. The underlying EHDA process permits room temperature fabrication, controlled output and scale-up potential for emerging MN devices as drug systems or lab-chip testing devices.

This research manuscript reports on Electrohydrodynamic Atomisation (EHDA) to engineer ondemand coatings for ocular contact lenses. A formulation approach was adopted to modulate the release of timolol maleate (TM) using chitosan and borneol. Polyvinylpyrrolidone (PVP) and poly (Nisopropylacrylamide) (PNIPAM) were electrically atomised to produce optimised, stationary contact lens coatings to encapsulate TM. The particle and fibre diameter, thermal stability, compatibility of the formed coatings along with their in vitro release-modulating effect and ocular tolerability were investigated. The results demonstrated highly stable nano-matrices with advantageous morphology and size. All formulations yielded coatings with high TM encapsulation (>88%); with excellent ocular biocompatibility. The coatings presented biphasic and triphasic release; depending on composition. Kinetic modelling revealed a noticeable effect of chitosan; the higher the concentration, the more the TM release due to chitosan swelling; with the release mechanism changing from Fickian diffusion (1% w/v; n = 0.5) to non-Fickian (5% w/v, 0.45 < n < 0.89). The use of EHDA has not yet been explored in depth within the ocular research remit; engineering on demand lens coatings capable of sustaining TM release. This is likely to offer an alternative dosage form for management of glaucoma with particular emphasis on improving poor patient compliance.

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