| Abstract
| - In this paper, we report a method for fabricating biofunctionalized nanoparticles by attaching human immunoglobulin (IgG) onto their surfaces through either electrostaticinteractions or covalent binding. We found that these IgG-presenting nanoparticles can bind selectively to the cellwalls of pathogens that contain IgG-binding sites basedon the investigation of transmission electron microscopyimages. Our results demonstrate that such Au−IgG nanoparticles may serve as useful nanoscale probes for exploring the interactions between IgG and pathogens. Furthermore, the IgG-presenting magnetic nanoparticles havebeen employed as effective affinity probes for selectivelyconcentrating traces of target bacteria from sample solutions. The trapped bacteria were then characterized byusing matrix-assisted laser desorption/ionization massspectrometry. The lowest cell concentration we detectedfor both Staphylococcus saprophyticus and Staphylococcus aureus in aqueous sample solutions (0.5 mL) was∼3 × 105 cfu/mL, while the detectable cell concentrationfor S. saprophyticus in a urine sample was ∼3 × 107cfu/mL.
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