Harnessing Microneedles for Delivery and Preservation of Natural Killer Cell-Derived Extracellular Vesicles

Natural killer cell-derived extracellular vesicles (NK-EVs) have demonstrated anti-inflammatory properties similar to those of their parent cells. EVs have been commonly delivered via intravenous (IV) administration, which can be invasive and is not ideal for chronic treatment. Another limitation of nanotherapy is its storage requirements, as EVs are commonly stored at -80 °C to preserve EV cargo and stability. In order to address these limitations, we explored dissolvable microneedles (MNs) as a promising alternative method for the administration of EVs. MNs have been used to deliver drugs, vaccines, and biomolecules, offering a convenient, noninvasive route of administration while preserving the therapeutic efficacy of EVs for extended periods, even at room temperature. Thus, we hypothesize that MN has the potential to sustain NK-EV stability and successfully deliver NK-EVs with minimal invasion. To test our hypothesis, we first developed an optimal MN formulation composed of hyaluronic acid and trehalose, both protein-protective materials that are biocompatible and biodegradable. After preparing MNs, we evaluated their stiffness, EV release profile, and ability to puncture pig skin. Additionally, the long-term storage stability of the EVs in MNs in inflammatory models in vitro and in vivo was evaluated. The MN successfully maintained EV efficacy even after storage after six months at room temperature, reducing the pro-inflammatory cytokine IL-6 by about 70% in inflamed human fibroblast cells relative to nontreated groups. Furthermore, EV-loaded MN treatment reduced both pro-inflammatory cytokines (IL-6 and TNFα) and psoriasis markers (Ki67 and IL-17) expression in a psoriasis model of chronic inflammation by about 40% compared to nontreated groups. Herein, our MN demonstrates the potential for easy-to-administer NK-EV therapies with long-term storage capabilities that preserve the NK-EV's anti-inflammatory properties.