(720g) Comprehensive Evaluation of Biodegradable Microneedle Patches for Veterinary Drug Delivery: In Vitro and In Vivo Studies

This research addresses the pressing need for effective pain management in farm animals undergoing routine procedures, such as castration, tail docking, and dehorning. These practices, while essential for husbandry, often cause significant pain and discomfort in animals due to the lack of anesthesia. Moreover, the absence of accepted pain relief methods poses challenges in maintaining animal welfare standards and productivity. Recognizing these issues, the study focuses on developing polymeric biodegradable microneedle patches for transdermal delivery of meloxicam, an effective analgesic (Fig. 1A).By integrating advanced material science, pharmacology, and veterinary medicine, we endeavor to provide a holistic solution that enhances both animal welfare standards and productivity in agricultural settings. Through this research, we aim to fill a crucial need in the field and contribute to the ongoing efforts to improve pain management practices in farm animal husbandry (Fig. 1B).The project aligns with the growing global concern for animal welfare in food production systems, driven by consumer sensitivities and industry standards. By utilizing polyvinyl alcohol (PVA), type I collagen (COL), and chitosan (CHI) in the microneedle patch formulation, we seek to enhance drug release kinetics, duration, and mechanical properties (Fig. 1A).Our investigation aims to optimize meloxicam diffusion through comprehensive in vitro and in vivo studies, encompassing in vitro dissolution, in vitro imaging, in vivo dissolution, and transdermal drug delivery capabilities. By elucidating the efficacy and suitability of the PVA-COL-CHI-MEL microneedle patch system, our research contributes to advancing pain management practices in agriculture.The findings from this study hold significant implications for veterinary professionals, producers, and regulatory bodies involved in farm animal welfare. By providing an effective and practical pain relief solution, our research strives to enhance animal welfare standards, productivity, and consumer confidence in food production systems.

Methods:

In vitro drug diffusion studies were conducted using a ballistic gel model to simulate microneedle performance without biological variability (Fig. 1C). SEM analysis depicted the sequential dissolution of PVA-COL-CHI-MEL microneedle patches at various time points over 24 hours. In vitro imaging in pig's ear cadaver skin demonstrated effective microneedle penetration and degradation over time. In vivo studies involved attaching microneedle patches to porcine ears and assessing their dissolution and drug delivery capabilities (Fig.1D). Plasma meloxicam concentrations were analyzed using ultra-performance liquid chromatography-tandem mass spectrometry.

Results:

In vitro studies revealed a consistent degradation pattern of microneedles in ballistic gel, with SEM images depicting a gradual reduction in height over 24 hours (Fig. 1E). In vitro imaging demonstrated successful penetration and dissolution of microneedles in pig's ear cadaver skin, corroborated by histological evaluations (Fig. 1F). In vitro drug release analysis showcased sustained release kinetics of meloxicam, achieving nearly 100% release within 18 hours (Fig 1G). In vivo dissolution studies indicated over 70% microneedle dissolution after 3 days (Fig. 1G). Plasma meloxicam concentrations demonstrated successful drug delivery through microneedle patches, although with some variability attributed to placement and animal behavior (Fig. 1H).

Conclusions:

The study underscores the potential of biodegradable microneedle patches for veterinary drug delivery, evidenced by their controlled dissolution, sustained drug release, and transdermal delivery capabilities. Experimental results affirm the promising attributes of the PVA-COL-CHI-MEL microneedle patch system. The in-vitro drug diffusion experiments using ballistic gel provide valuable insights into the dissolution and drug release capabilities of the microneedle patch. This approach allows researchers to evaluate microneedle performance in a controlled environment and gain a better understanding of drug release kinetics. It also offers an efficient way to screen and optimize microneedle formulations before advancing to more complex studies involving animal models. Additionally, the release profile observed in this study represents a significant improvement over previous investigations. Unlike earlier designs that achieved a release rate of only 33.2% over 7 days, the novel microneedle patch formulation achieved nearly 100% release of the 25 mg meloxicam content from a single patch within 18 hours. This remarkable enhancement in drug release efficiency highlights the substantial efficacy of the new formulation. The in-vivo dissolution capability of the microneedle patch demonstrates its potential for effective and controlled transdermal drug delivery. The strategic placement of the patch, the clear illustration of its transdermal drug delivery mechanism, and the observed in-vivo microneedle dissolution all contribute to the understanding of the patch's efficacy and suitability for practical applications in drug delivery, offering promising prospects for future pharmaceutical advancements. Our new in vivo results further validate the efficacy of the microneedle patch system in delivering MEL for pain relief in animal subjects. The observed variations in meloxicam concentration between the plasma and ear tissue highlight the dynamic pharmacokinetics of transdermal drug delivery in vivo and emphasize the need for further investigation into factors influencing drug distribution and absorption within different tissue compartments. Moreover, our in vivo dissolution studies revealed a significant improvement in drug release efficiency compared to previous investigations, underscoring the practical effectiveness of the microneedle patch system. In summary, this work not only advances the theoretical understanding of transdermal drug delivery in veterinary medicine but also translates into practical solutions that significantly benefit animal health and welfare. It represents a pivotal step toward safer, more effective, and more accessible pain relief options for farm animals, ultimately contributing to improved production outcomes, food safety, and the overall well-being of these animals.

Figure 1. Comprehensive study and application of microneedle patch technology for transdermal drug delivery in veterinary medicine. A) Macroscopy picture of the microneedle patch and schematic illustrations of transdermal delivery of meloxicam using PVA-COL-CHI-MEL microneedle patches. B) Veterinary applications of microneedle patches. C) Microneedle insertion set up on ballistic gel (top layer: adhesive waterproof tape) and schematic microneedle dissolution. D) In-Vivo Setup: Preparing the pig's inner and outer ear surface for microneedle patch application. E) SEM micrographs demonstrating sequential microneedle patch dissolution at different time points. F) In-vitro imaging of microneedle insertion in pig's ear cadaver skin. G) Schematic of the in-vitro setup for monitoring drug delivery from the microneedles, using a Shimadzu 20A prominence High-Performance Liquid Chromatography (HPLC) system for quantification over time. In-vitro cumulative release profile of meloxicam from the microneedle patch, plotted over 18 hours. H) Plasma meloxicam concentrations using a microneedle patch for drug delivery.