Bacterial species-identifiable magnetic nanosystems for early sepsis diagnosis and extracorporeal photodynamic blood disinfection.

Despite the numerous bacteria detection and elimination techniques available nowadays, sensitive diagnosis and treatment of sepsis (caused by the presence of bacteria in the bloodstream), especially at the early stage, remain big challenges. Here we report a nanosystem for early sepsis diagnosis and complete extracorporeal blood disinfection, based on iron oxide magnetic nanoparticles functionalized with chlorin e6 molecules and bacterial species-identifiable aptamers (Fe ₃ O ₄ -Ce6-Apt). We demonstrate that the Fe ₃ O ₄ -Ce6-Apt nanosystem can achieve simultaneous blood bacterial species identification and enrichment in a single step, and the enriched bacteria can be easily detected with the assistance of fluorescence microscopic determination. Based on this Fe ₃ O ₄ -Ce6-Apt nanosystem, successful diagnosis of sepsis caused by a single (Staphylococcus aureus) or multiple species (Staphylococcus aureus and Escherichia coli) of bacteria in mice has been realized. Compared to the gold standard blood culture method, this Fe ₃ O ₄ -Ce6-Apt nanosystem-based strategy has a comparable detection sensitivity (around 10 colony-forming units) but a significantly shortened diagnosis turnaround time (within 1.5 h), revealing its great potential for early sepsis diagnosis in clinical settings. Moreover, benefitting from the strong photodynamic effect of the Fe ₃ O ₄ -Ce6-Apt nanosystem, complete extracorporeal blood disinfection has been achieved. Remarkably, we also demonstrate that the disinfected blood can be reused for mice transfusion application without inducing adverse reactions, indicating the fruitful potential of the Fe ₃ O ₄ -Ce6-Apt nanosystem for sepsis treatment. Apart from the sepsis-associated applications, we believe that the Fe ₃ O ₄ -Ce6-Apt nanosystem could find wide applications in the fields of health and environmental sciences that require bacteria monitoring and sterilization.