Abstract
Dissolving microneedle arrays (dMNAs) are promising devices for intradermal vaccine delivery. The aim of this study was to develop a reproducible fabrication method for dMNAs based on an automated nano-droplet dispensing system that minimizes antigen waste. First, a polymer formulation was selected to dispense sufficiently small droplets (<18 nL) that can enter the microneedle cavities (base diameter 330 µm). Besides, three linear stages were assembled to align the dispenser with the cavities, and a vacuum chamber was designed to fill the cavities with dispensed droplets without entrapped air. Lastly, the dispenser and stages were incorporated to build a fully automated system. To examine the function of dMNAs as a vaccine carrier, ovalbumin was loaded in dMNAs by dispensing a mixture of ovalbumin and polymer formulation, followed by determining the ovalbumin loading and release into the skin. The results demonstrate that functional dMNAs which can deliver antigen into the skin were successfully fabricated via the automatic fabrication system, and hardly any antigen waste was encountered. Compared to the method that centrifuges the mould, it resulted in a 98.5% volume reduction of antigen/polymer solution and a day shorter production time. This system has potential for scale-up of manufacturing to an industrial scale.
Highlights
Intradermal administration of antigens is attractive for vaccination, because the skin is accessible and contains a large population of antigen-presenting cells (Engelke et al, 2015; Skobe and Detmar, 2000)
Too high polymer concentra tions (e.g., 50% (w/v) polyvinyl alcohol (PVA)) resulted in too viscous solutions to cast onto the mould
In the fluorescence microscopic image of the fabricated dissolving microneedle array (dMNA) (Fig. 5d), the red part in the array indicates that polyvinyl pyrroli done (PVP)/poly(ethylene glycol) (PEG) with fluorescent dye is spread over the array
Summary
Intradermal administration of antigens is attractive for vaccination, because the skin is accessible and contains a large population of antigen-presenting cells (Engelke et al, 2015; Skobe and Detmar, 2000). Previous studies revealed that intradermal vaccination induces similar or higher levels of immune responses as compared to subcutaneous or intramuscular administration. The stratum corneum, the outermost layer of the skin, which acts as a barrier to protect the body from its environment, prevents vaccines from entering the skin. To overcome this barrier, specialized delivery devices have been developed, such as tattooing, ballistic guns, ultrasound-based devices, and microneedles (Kagan et al, 2012; Kwan et al, 2015; Soto et al, 2017; Yildirim et al, 2018).
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