(M1530-07-38) Design and Development of Rifampicin Loaded  PLGA Nanoparticles for the Prevention of Prosthetic Infections

Purpose: Infection is the most serious complication of joint replacements occurring 0.5–2% of the performed arthroplasties [1]. Antibiotic treatment is a fundamental pillar that should ideally be started before or during the operation since most infections are acquired intraoperatively. However, the ability of the main infection-causing microorganisms to adhere to the prosthetic material creating a biofilm requires doses of antimicrobial agent 200 to 1,000 times higher than those needed against planktonic forms. An increase in antimicrobial doses would not ensure efficacy at the articular level and can produce toxicity. A Locally administered prophylactic treatment to prevent the development of prosthetic infections is a potential approach to solve this problem. The current strategies of local administration of antimicrobials are based on their sprinkling on the surgical site or their incorporation in bone cements. They represent numerous limitations such as the short duration of action, the impossibility of repeating the administration after surgery, and the difficulty of standardizing the dose administered [2]. The use of nanoparticles as antimicrobial carriers may resolve these problems [3]. The aim of this work was to design, develop, and characterized poly(lactic-co-glycolic acid) loaded with rifampicin (Rif), a mainstay drug in the treatment of these infections, whose suspension can be sprayed intraoperatively over the prosthesis.

Methods: Nanoparticles were elaborated by emulsion solvent evaporation technique, using poly(lactic-co-glycolic acid) PLGA RG® 502-H as polymer, poly(vinyl alcohol) (PVA) solution as surfactant and dichloromethane as the organic solvent. Formulations with different PVA concentrations, sonication times, and rif:PLGA ratios were elaborated (Table 1). All formulations were characterized in terms of particle size, drug loading, and entrapment efficiency. The shape and morphology of selected formulations were also evaluated by scanning electron microscopy (SEM). Finally, drug release in both PBS pH 7.4 and PBS pH 7.4 with hyaluronic acid at 0.3% to simulate intra-articular fluid was also determined.

Results: All the formulations developed in this work showed a particle size, expressed as volume diameter, in the range of 260-410 nm (Table 1). The formulations prepared with a lower concentration of PVA (formulations F1 and F4) showed the largest particle sizes (greater than 340 nm). An increase in the concentration of surfactants, PVA in this case, usually triggers a decrease in particle size, which is attributed to a greater stabilization of the emulsion. In general, an increase in sonication time also implies a decrease in particle size. However, in this work, sonication time did not influence on the size of rifampicin nanoparticles. The increase in the rifampicin: polymer ratio did not affect the particle size either. In relation to the polydispersion index (PDI), all formulations showed values below or close to 0.2, indicating a moderate and acceptable polydispersion. Entrapment efficiency values above 43% were obtained in all cases. F1 formulation that showed the largest particle size, around 400 nm and it is expected to be effectively retained in the administration site, as well as one of the highest rifampicin loadings (224.16 µg rifampicin/10mg Nps) was selected for SEM and drug release studies. As displayed in Figure 1 and 2, these nanoparticles showed a spherical shape, a smooth surface, and a controlled drug release for 14 days. Similar drug release profiles were detected in both PBS and PBS+hyaluronic acid mediums. However, a higher burst effect was appreciated in this latter (28 vs 51%).

Conclusion: F1 formulation with a particle size of 409 nm, a PDI value of 0.21 and a drug loading of 224.16± 32.13 µg rifampicin/10 mg Nps could be useful in the prevention of prosthetic infections.

References: 1. Yusuf E et. al. The State of Microbiology Diagnostic of Prosthetic Joint Infection in Europe: An In-Depth Survey Among Clinical Microbiologists. Front Microbiol. 2022 Jun 20;13:906989.
2. López-Torres II et al. The tale of microencapsulated rifampicin: is it useful for the treatment of periprosthetic joint infection? Int Orthop. 2022 Apr;46(4):677-685.
3. Pelgrift RY et. al. Nanotechnology as a therapeutic tool to combat microbial resistance. Adv Drug Deliv Rev. 2013 Nov;65(13-14):1803-15.

Acknowledgments: This work is part of project (PI21/01130: Micro y Nanomedicinas para la prevención y el tratamiento de infecciones protésicas (CARRIER4PROST)) funded by "Instituto de Salud Carlos III" and "Fondo Europeo de Desarrollo Regional (FEDER)".

Table 1: Characteristics of the developed rifampicin loaded PLGA nanoparticles



Figure 1: SEM images of F1 nanoparticles.



Figure 2: Drug release profile of F1 nanoparticles in PBS and PBS+Hyaluronic acid 0.3%