Aptamer-Targeted PLGA Nanoparticles for Biofilm-Directed Intra-articular Antibiotic Delivery in Prosthetic Joint Infection

Introduction: Prosthetic joint infection (PJI) is a severe complication of orthopedic surgery, driven by biofilm-forming bacteria such as Staphylococcus aureus. Conventional antibiotics are limited in penetrating biofilms or remaining localized at the infection site. We engineered a targeted nanocarrier system by conjugating DNA aptamers specific to S. aureus biofilm components onto poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) encapsulating vancomycin. PLGA NPs were synthesized using flow-focusing microfluidics, followed by surface functionalization via EDC/NHS chemistry. Aptamer conjugation was validated using gel electrophoresis and DLS. Targeting efficiency and antimicrobial activity were evaluated through fluorescence microscopy, bacterial viability assays and in vitro biofilm models. Biodistribution and joint retention were assessed using fluorescent aptamer-conjugated NPs following intra-articular injection in rat knee joints. Results: The optimized vancomycin-loaded NPs exhibited uniform morphology, high vancomycin loading capacity (7.9 ± 2.2%), and a sustained biphasic release profile with an early high-release phase followed by slower extended release. PK modeling indicated prolonged intra-articular drug retention with concentrations maintained above the minimum inhibitory concentration (MIC) for an extended period. Aptamer conjugation preserved nanoparticle stability and enhanced binding and retention within S. aureus biofilms in vitro, supporting improved biofilm localization. In-vivo fluorescence imaging demonstrated high local retention of aptamer-conjugated NPs, supporting localized joint retention with limited off-target tissue signal. Conclusions: S. aureus-specific aptamer conjugated nanoparticles (SA Apt-P(V)) represent a targeted intra-articular delivery platform with potential for localized PJI therapy. The combined in-vitro and in-vivo findings highlight their potential to improve local therapeutic concentration, minimize systemic exposure, and enhance infection control within prosthetic joints.