Development and In-Vitro Evaluation of Gallium-68 Labelled Staphylococcus Aureus-Specific Aptamer as a Potential PET Agent for Infection Imaging

Abstract

Background: Staphylococcus aureus (S. aureus) is the most common causative pathogen associated with a wide range of infections, from mild to life-threatening conditions such as osteomyelitis, endocarditis, and pneumonia. Early detection and reliable differentiation between infection and sterile inflammation are essential for accurate diagnosis and effective treatment. However, most radiopharmaceuticals currently available fail to discriminate between these conditions, underscoring the need for infection-specific imaging agents. Materials and Methods: In this study, a Gallium-68 (Ga-68)-labeled S. aureus-specific aptamer was developed as a potential PET infection imaging probe. Aptamers were selected using the cell-systematic evolution of ligands by exponential enrichment (SELEX) method, and their specificity was verified by fluorescence-based binding assays. Radiolabeling was achieved via DOTA chelation, and radiochemical purity was determined. Additionally, in vitro binding assays were performed with S. aureus, while Escherichia coli (E. coli) served as a control. Results: The aptamer exhibited an affinity constant (Kₐ) of 2260 ± 634 CFU/ mL and a linear detection range of 250-2×10⁴ CFU/mL, with a limit of detection of 171 CFU/mL for S. aureus. The Ga-68-labeled aptamer demonstrated radiochemical purity greater than 99%. In vitro binding increased linearly with rising S. aureus concentrations (10³-2×10⁴ CFU/mL), while minimal binding to E. coli confirmed its specificity. Conclusion: These results demonstrate that the Ga-68-labeled S. aureus-specific aptamer holds promise as an infection-targeted PET imaging agent. Although currently limited to in vitro evaluation, such aptamer-based radiopharmaceuticals may contribute to improved diagnosis and imaging of infectious diseases. © 2025, Novin Medical Radiation Institute. All rights reserved.