Abstract
Microneedle technologies have been developed for dermal drug and vaccine delivery, including hollow-, solid-, coated-, and dissolving microneedles. Microneedles have been made in many different geometries and of many different materials, all of which may influence their skin-penetrating ability. To ensure reproducible and effective drug and vaccine delivery via microneedles, the optimal insertion parameters should be known. Therefore, a digitally-controlled microneedle applicator was developed to insert microneedles into the skin via impact insertion (velocity) or via pressing force insertion. Six microneedle arrays with different geometries and/or materials were applied onto ex vivo human skin with varying velocities or pressing forces. Penetration efficiency and delivered antigen dose into the skin after application of microneedles were determined. In general, microneedles pierced the skin more efficiently when applied by impact application as compared to application via pressing force. However, the angle of application of the applicator on the skin can affect the velocity of the impact, influencing the penetration efficiency of microneedles. Regarding the antigen delivery into the skin, the delivered dose was increasing by increasing the velocity or pressure, and thus, increasing the penetration efficiency. These data demonstrate that an applicator is an important tool to determine optimal application conditions with ex vivo human skin.
Highlights
Drug and vaccine delivery via the skin offers several advantages over conventional administration routes, including prevention of drug and vaccine degradation by the gastro-intestinal tract, elimination of pain and discomfort, acceptability by people with needle-phobia, avoidance of hazardous waste, needle-stick injuries, and needle re-use [1,2,3,4,5,6,7]
The MLT-475 shape is similar to conventional hypodermic needles, whereas MLT-200 consists of groups of four needles positioned in a square
We have developed an applicator that reproducibly delivers a chosen pressing force and impact velocity
Summary
Drug and vaccine delivery via the skin offers several advantages over conventional administration routes (i.e., oral and parenteral), including prevention of drug and vaccine degradation by the gastro-intestinal tract, elimination of pain and discomfort, acceptability by people with needle-phobia, avoidance of hazardous waste, needle-stick injuries, and needle re-use [1,2,3,4,5,6,7]. Different microneedle technologies have been developed for drug and vaccine delivery via the skin, including (a) hollow microneedles for injections of liquid drugs or vaccine formulations, and (b) solid microneedles classified as (i) microneedles for skin pretreatment, and (ii) porous, coated, hydrogel-forming microneedles and dissolving (polymeric) microneedles that, after insertion into the skin, release the drug or vaccine [15,16,17,18] These different microneedle types have been made with many different geometries (e.g., length, sharpness, diameter, density), and have been made of different materials (e.g., glass, silicon, stainless steel, titanium, sugar, (synthetic) polymer), which all may influence their skin penetrating ability
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