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.

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In this study, the ability to control the shell thickness of hollow polymeric microspheres prepared using electrohydrodynamic processing at ambient temperature was investigated. Polymethylsilsesquioxane (PMSQ) was used as a model material for the microsphere shell encapsulating a core of liquid perfluorohexane (PFH). The microspheres were characterized by Fourier transform infrared spectroscopy and optical and electron microscopy, and the effects of the processing parameters (flow-rate ratio, polymer concentration and applied voltage) on the mean microsphere diameter (D) and shell thickness (t) were determined. It was found that the mean diameters of the hollow microspheres could be controlled in the range from 310 to 1000 nm while the corresponding mean shell thickness varied from 40 to 95 nm. The results indicate that the ratio D : t varied with polymer concentration, with the largest value of approximately 10 achieved with a solution containing 18 wt% of the polymer, while the smallest value (6.6) was obtained at 36 wt%. For polymer concentrations above 63 wt%, hollow microspheres could not be generated, but instead PMSQ fibres encapsulating PFH liquid were obtained.

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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.

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Here, we introduce core-shell nanofibers based on chitosan (CS)-loaded poly (εcaprolactone) (PCL) shell and 5-fluorouracil (5-FU)-loaded Poly(N-vinyl-2pyrrolidone) (PVP) core for synergistic therapy of melanoma skin cancer. The yielded nanofibers exhibited an average diameter of 503 nm with high drug-encapsulating efficiency and good mechanical properties. Moreover, the burst release of 5-FU significantly inhibited melanoma skin cancer cells (B16F10 cells), and the sustained release of CS exhibited "remedying effects" on normal skin cells (L929 cells) after suffering adverse effects from 5-FU treatment. For the B16F10 cells, the early apoptosis cells increased from 0. 8% to 62.2% after being treated with blended films loaded with 5-FU (2 wt%) for 24 h; for the L929 cells, the vital cells increased from 68.9% to 77.0%, and the early apoptosis of stage cells decreased from 12.3% to 10.9% after being treated with blended films with CS (8 wt%) for 24 h. In conclusion, the results introduced in this work can be a promising strategy for cancer treatment and possesses synergism potential to broaden an avenue for chemotherapeutic therapy with minimum adverse effects on normal cells.