Boronic acid-functionalized Fe₃O₄ nanoparticles for activity-preserved enrichment of low-abundance bacteria from real...

Pathogenic bacterial infections represent a significant and ongoing threat to public health. The development of a sensitive, convenient, and accurate method for diagnosing pathogenic bacteria is a formidable challenge due to their low abundance in complex biological samples, especially in the early stages of diseases. In this study, a kind of phenylboronic acid-functionalized Fe₃O₄ nanoparticles (NPs), known as Fe₃O₄@poly(PEGDA-co-MAAPBA) NPs, was developed for effectively enriching low levels of pathogenic bacteria from complex samples and then diagnosing them through microbiological cultures. In this design, the resultant Fe₃O₄@poly(PEGDA-co-MAAPBA) NPs could recognize pathogenic bacteria because of the reversible reactions between the phenylboronic acid groups on the NPs and the cis-diol structures outside of the bacterial cells. By exploiting the magnetic properties of Fe₃O₄ NPs, bacteria were able to anchored onto the resulting NPs (NPs@bacteria) for easy enrichment. Utilizing microbiological culture techniques, successful cultivation of NPs@bacteria was achieved, demonstrating that bacterial activity remained unaffected during the enrichment process. The proposed method exhibited a limit of detection as low as 0.4 colony-forming units per milliliter. The Fe₃O₄@poly(PEGDA-co-MAAPBA) NPs were applied successfully for testing Staphylococcus aureus in urine samples which were typically considered to be free of bacterial contamination, indicating excellent selectivity and enrichment capability of the prepared NPs in complex samples. It suggests that the Fe₃O₄@poly(PEGDA-co-MAAPBA) NPs have the potential to become a powerful tool for early diagnosis of pathogenic bacteria in the clinic.