Transdermal vaccination via 3D-printed microneedles induces potent humoral and cellular immunity.

Vaccination is an essential public health measure for infectious disease prevention. The exposure of the immune system to vaccine formulations with the appropriate kinetics is critical for inducing protective immunity. In this work, faceted microneedle arrays were designed and fabricated utilizing a three-dimensional (3D)-printing technique called continuous liquid interface production (CLIP). The faceted microneedle design resulted in increased surface area as compared with the smooth square pyramidal design, ultimately leading to enhanced surface coating of model vaccine components (ovalbumin and CpG). Utilizing fluorescent tags and live-animal imaging, we evaluated in vivo cargo retention and bioavailability in mice as a function of route of delivery. Compared with subcutaneous bolus injection of the soluble components, microneedle transdermal delivery not only resulted in enhanced cargo retention in the skin but also improved immune cell activation in the draining lymph nodes. Furthermore, the microneedle vaccine induced a potent humoral immune response, with higher total IgG (Immunoglobulin G) and a more balanced IgG1/IgG2a repertoire and achieved dose sparing. Furthermore, it elicited T cell responses as characterized by functional cytotoxic CD8+ T cells and CD4+ T cells secreting Th1 (T helper type 1)-cytokines. Taken together, CLIP 3D-printed microneedles coated with vaccine components provide a useful platform for a noninvasive, self-applicable vaccination.

Spatially controlled coating of continuous liquid interface production microneedles for transdermal protein delivery.

Microneedle patches, arrays of micron-scale projections that penetrate skin in a minimally invasive manner, are a promising tool for transdermally delivering therapeutic proteins. However, current microneedle fabrication techniques are limited in their ability to fabricate microneedles rapidly and with a high degree of control over microneedle design parameters. We have previously demonstrated the ability to fabricate microneedle patches with a range of compositions and geometries using the novel additive manufacturing technique Continuous Liquid Interface Production (CLIP). Here, we establish a method for dip coating CLIP microneedles with protein cargo in a spatially controlled manner. Microneedle coating mask devices were fabricated with CLIP and utilized to coat polyethylene glycol-based CLIP microneedles with model proteins bovine serum albumin, ovalbumin, and lysozyme. The design of the coating mask device was used to control spatial deposition and loading of coated protein cargo on the microneedles. CLIP microneedles rapidly released coated protein cargo both in solution and upon insertion into porcine skin. The model enzyme lysozyme was shown to retain its activity throughout the CLIP microneedle coating process, and permeation of bovine serum albumin across full thickness porcine skin was observed after application with coated CLIP microneedles. Protein-coated CLIP microneedles were applied to live mice and showed sustained retention of protein cargo in the skin over 72 h. These results demonstrate the utility of a versatile coating platform for preparation of precisely coated microneedles for transdermal therapeutic delivery.

Single-Step Fabrication of Computationally Designed Microneedles by Continuous Liquid Interface Production.

Microneedles, arrays of micron-sized needles that painlessly puncture the skin, enable transdermal delivery of medications that are difficult to deliver using more traditional routes. Many important design parameters, such as microneedle size, shape, spacing, and composition, are known to influence efficacy, but are notoriously difficult to alter due to the complex nature of microfabrication techniques. Herein, we utilize a novel additive manufacturing ("3D printing") technique called Continuous Liquid Interface Production (CLIP) to rapidly prototype sharp microneedles with tuneable geometries (size, shape, aspect ratio, spacing). This technology allows for mold-independent, one-step manufacturing of microneedle arrays of virtually any design in less than 10 minutes per patch. Square pyramidal CLIP microneedles composed of trimethylolpropane triacrylate, polyacrylic acid and photopolymerizable derivatives of polyethylene glycol and polycaprolactone were fabricated to demonstrate the range of materials that can be utilized within this platform for encapsulating and controlling the release of therapeutics. These CLIP microneedles effectively pierced murine skin ex vivo and released the fluorescent drug surrogate rhodamine.