(T1130-01-06) Nystatin-Loaded Microneedles via MeltPreP Vacuum Compression Molding for Prolonged Defense Against Candida albicans

Purpose: Fungal infections, including those caused by Candida albicans, pose significant health risks, prompting the need for innovative strategies to improve treatment effectiveness. Nystatin, a polyene antifungal agent, acts by disrupting fungal cell membranes via pore formation¹. Although nystatin is available in various delivery formulations such as suspensions, powders, and creams, these typically require application two to three times daily. Designing a dosage form capable of sustaining nystatin delivery could offer benefits by reducing the frequency of application. Microneedles (MN)s offer a minimally invasive delivery form, facilitating precise application and promoting enhanced and sustained drug absorption. This study demonstrates a solvent free reliable and scalable fabrication technique for MNs loaded with nystatin through novel MeltPrep vacuum compression molding (VCM)². Also, the viability of the nystatin loaded MNs for sustained treatment of Candida albicans infection was investigated.

Methods: The MNs were made using the novel MeltPrep vacuum compression molding (VCM) that uses heat and vacuum to shape the powder inserted into the desired mold (Fig. 1). The MN mold used in this study was an array of 100 needles, 8 mm x 8 mm in size, and 500 µm needle length. The strength for most nystatin formulations used in practice is 100,000 units/gram. Clove oil was included in the formulation due to the synergistic antifungal effect observed with nystatin, previously in our lab. MNs with 2.27% w/w nystatin, with and without clove oil (10% w/w) were fabricated using Soluplus^® polymer. The mixture of these ingredients was pulverized with ethanol and dried at 30°C to convert it to a powder form that could be melted using the MeltPrep VCM equipment. The powder was heated at 170°C for 15 min under a vacuum and cooled for 15 min to prepare the MNs (Fig.1, Step 1). MNs were analyzed for morphology, characterized for mechanical integrity/skin penetration efficiency. Further, the drug content in the needles was investigated using UV spectrophotometer (305 nm) after extraction and dilution with dimethyl sulfoxide. A quantitative antifungal test was done in agar plates to assess the efficacy of fabricated nystatin MNs for Candida albicans treatment.

Results: The fabricated MNs were observed to be sharp and pyramidal in shape as visualized under the microscope (Fig. 2 a &b). To test the durability and effectiveness of the MNs for puncturing the skin and delivering the drug contents, dermatomed pig skin was used to visualize channels formed by the needles. Dark blue channels were observed under the microscope with a dye binding staining confirming channel formation in skin (Fig. 2 c & d). The drug content in nystatin alone MNs was found to be 1.85 ± 0.04 mg, while that of nystatin-clove oil MNs was determined to be 1.91 ± 0.08 mg (n=3). (Fig. 2 e). In vitro Kirby Bauer Diffusion Assay with MNs revealed suppression of fungal growth as compared to the commercial cream (Fig. 2 f, g, h).

Conclusion: The study demonstrated the successful fabrication of nystatin-loaded MNs using the novel VCM method for the first time. In vitro studies show the efficacy of Nystatin loaded MNs for suppressing the growth of Candida albicans.

References: (1) Zhang, X.; Li, T.; Chen, X.; Wang, S.; Liu, Z. Nystatin Enhances the Immune Response against Candida Albicans and Protects the Ultrastructure of the Vaginal Epithelium in a Rat Model of Vulvovaginal Candidiasis. BMC Microbiol 2018, 18 (1), 1–11. https://doi.org/10.1186/s12866-018-1316-3
(2) Kshirsagar, S. M.; Kipping, T.; Banga, A. K. Fabrication of Polymeric Microneedles Using Novel Vacuum Compression Molding Technique for Transdermal Drug Delivery. Pharm Res 2022, 39 (12), 3301–3315. https://doi.org/10.1007/s11095-022-03406-8.

Acknowledgements: Dr. Ashana Puri would like to thank Dr. Daniel Treffer for supplying MeltPrep VCM Disc tool and for useful discussions pertaining to microneedle fabrication protocol.


Fig. 1. Illustration of the vacuum compression molding (VCM) process for patch fabrication using a MeltPrep VCM Tool.


Fig. 2. Optical images of (a) nystatin MNs (b) nystatin & clove oil MNs visualized under a microscope. Dye binding study showing (c) nystatin alone and (d) nystatin & clove oil. The dark blue circles indicate channels created by the microneedles in skin. The nystatin MNs, nystatin alone (e) and (f) nystatin & clove oil were inserted in agar plates inoculated with Candida albicans and antifungal effect compared to the commercially available nystatin cream (g).