Drug administration via the transdermal route is an evolving field that provides an alternative to oral and parenteral routes of therapy. Several microneedle (MN) based approaches have been developed. Among these, coated MNs (typically where drug is deposited on MN tips) are a minimally invasive method to deliver drugs and vaccines through the skin. In this review, we describe several processes to coat MNs. These include dip coating, gas jet drying, spray coating, electrohydrodynamic atomisation (EHDA) based processes and piezoelectric inkjet printing. Examples of process mechanisms, conditions and tested formulations are provided. As these processes are independent techniques, modifications to facilitate MN coatings are elucidated. In summary, the outcomes and potential value for each technique provides opportunities to overcome formulation or dosage form limitations. While there are significant developments in solid degradable MNs, coated MNs (through the various techniques described) have potential to be utilized in personalized drug delivery via controlled deposition onto MN templates.

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.

This study aims to explore the application of fused deposition modeling (FDM), a widely used 3D printing technique, in the fabrication of personalised hernial meshes. Eight different meshes with and without the loading of an antibiotic (ciprofloxacin HCl) were designed using two different polymers, polypropylene (PP) and polyvinyl alcohol (PVA), having different pore size, shape and thread thickness. Printed meshes were evaluated for their mechanical, drug loading and release characteristics. Among the fabricated meshes, polypropylene has shown adequate printability characteristics where polyvinyl alcohol filaments showed comparatively easy handling during 3D printing. All the printed meshes showed satisfactory mechanical properties. However, the PVA meshes showed slightly faster release as compared to PP based meshes. Moreover, in-vivo testing in rabbit models was also performed for assessing biocompatibility and adhesiogenecity. Post-implantation observations in animal models revealed no signs of implant rejection and the extent of adhesions to the visceral tissue was mild to moderate. Animals implanted with ciprofloxacin HCl loaded meshes exhibited fewer fluctuations in body temperature, and they had faster-wound healing capacity. This work demonstrated for the first time that FDM is an effective and low-cost alternative for the manufacturing of tailored mesh for the management of hernia. The method has also been successfully employed for the preparation of drug loaded 3D mesh, which may be effectively used against post-surgical infections.

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.