(W1230-01-02) Liposome-Based Dissolving Microneedles Loaded with Rifampicin for Improved Treatment of MRSA-Induced Skin Infection

Purpose: Staphylococcus aureus (S. aureus) is a Gram-positive bacterium that can cause a range of diseases, from superficial skin infections to endocarditis. Methicillin-resistant S. aureus (MRSA) is a predominant cause of infections that are becoming increasingly complicated and recurrent, with rising hospitalizations. Rifampicin (RIF) is an effective antibiotic against systemic and local staphylococcal infections but its monotherapy use is abandoned due to the rapid rise of resistance. Nanodrugs have been proposed to eradicate MDR species as they may increase drug accumulation at the target site, decrease resistance and reduce impact on indigenous microflora. In particular, liposomal antibiotics have been investigated to target MRSA colonies on the skin, as they are biocompatible, biodegradable, and have low toxicity. However, conventional liposomes have high ruptures and drug leakage in the outermost skin layers. Microneedle array patches (MN) represent a painless and self-administrable approach for drug delivery to the skin, including antibiotics. MNs provide precise and controlled delivery of drugs, avoid first-pass metabolism and promote penetration of the skin barrier. Thus, MNs combined with liposomes could enhance targeted antibiotic delivery to MRSA-infected sites, reducing adverse effects and promoting skin function regeneration.

Methods: Liposome loaded RIF (LipoRIF) dispersion was obtained by a solvent injection method, as illustrated in Figure 1A. The tip layer was constituted by freeze-dried LipoRIF and an aqueous solution of PVA-PVP (PP2) (1:1 ratio of 40% w/w each). The blend was then poured into a 16x16 silicone mould (pyramidal needles of 850 mm height, 300 mm base width, 300 mm interspacing and 0.36 cm² patch area). All MN formulations were visualised using a digital microscope and scanning electron microscope (SEM). A Texture Analyzer was used to evaluate the mechanical properties of the MAPs when subjected to a compressive force of 32 N, analogous to manual thumb pressure⁷. The insertion capability of the MAPs into the skin simulant Parafilm® M⁷ and ex vivo full thickness neonatal porcine skin were evaluated in situ using optical coherence tomography (OCT). Dermatokinetic studies were conducted using modified Franz diffusion cells in order to quantify the amount of drug deposited into skin as well as the amount of drug that permeated through the neonatal porcine skin.

Results: The formulations of LipoRIF-DMNs were successfully able to form homogeneous MN arrays, as presented in Figure 1(D-E). The application force of 32N/array reduced needles height less than 10% in all cases (Figure 1B). For the insertion studies, DMN formulations were able to penetrate down into the dermis to a depth of 500 µm, which was confirmed by OCT analysis (Figure 1 H-K). Dermatokinetic studies revealed that the delivery efficiencies of RIF found in the skin deposition study were 40% (Figure 2A-B). Over the course of 24 h, we observed that DMN formulation resulted in an increase in drug deposited into the skin with time. The presence of the LipoRIF in the skin may enhance the interaction with MRSA strains, favouring the eradication of SSTIs.

Conclusion: The present results describe the successful development and characterization of DMNs which are loaded with LipoRIF in the tips of the needles. Furthermore, dermatokinetic studies showed that, after 24 h, most of the drug had been delivered intradermally into the skin. The proposed LipoRIF-DMNs may provide an enhanced minimally invasive strategy to treat SSTIs and superficial skin diseases caused by MRSA.

References: 1. J.R. Hindy, S.F. Haddad, S.S. Kanj, New drugs for methicillin-resistant Staphylococcus aureus skin and soft tissue infections, Curr Opin Infect Dis. 35 (2022) 112–119.
2. Z. Zheng, P.S. Stewart, Penetration of Rifampin through Staphylococcus epidermidis Biofilms, Antimicrob Agents Chemother. 46 (2002) 900.
3. G.N. Forrest, K. Tamura, Rifampin Combination Therapy for Nonmycobacterial Infections, Clin Microbiol Rev. 23 (2010) 14.
4. S.A. Coulman, A. Anstey, C. Gateley, A. Morrissey, P. McLoughlin, C. Allender, J.C. Birchall, Microneedle mediated delivery of nanoparticles into human skin, Int J Pharm. 366 (2009) 190–200.
5. Q.K. Anjani, A.H. Bin Sabri, J. Domínguez-Robles, N. Moreno-Castellanos, E. Utomo, L.A.H. Wardoyo, E. Larrañeta, R.F. Donnelly, Metronidazole nanosuspension loaded dissolving microarray patches: An engineered composite pharmaceutical system for the treatment of skin and soft tissue infection, Biomaterials Advances. 140 (2022) 213073.

Figure 1. (A) Schematic illustration of LipoRIF solid preparation. (B) Digital, SEM, and multi-photon image of MN array loaded with LipoRIF. (C) OCT photos of the skin insertion of LipoRIF-DMN. (D) Drug distribution at different times after application of LipoRIF-DMNs (Means + SD, n = 4).