title: A rapid SERS method for label-free bacteria detection using polyethylenimine-modified Au-coated magnetic microspheres and Au@Ag nanoparticles.
abstract: A rapid, sensitive, and label-free SERS detection method for bacteria pathogens is reported for the first time. The method, which is based on the combination of polyethylenimine (PEI)-modified Au-coated magnetic microspheres (Fe3O4@Au@PEI) and concentrated Au@Ag nanoparticles (NPs), was named the capture-enrichment-enhancement (CEE) three-step method. A novel Fe3O4@Au microsphere with monodispersity and strong magnetic responsiveness was synthesized as a magnetic SERS substrate and amino functionalized by PEI self-assembly. The negatively charged bacteria were quickly captured and enriched by the positively charged Fe3O4@Au@PEI microspheres, and the bacteria SERS signal was synergistically enhanced by using Fe3O4@Au@PEI microspheres and Au@Ag NPs in conjunction. The CEE three-step method proved useful in tap water and milk samples, and the total assay time required was only 10 min. Results further demonstrated that the CEE three-step method could be a common approach for detecting a wide range of bacteria, as verified by its detection of the Gram-positive bacterium E. coli and Gram-positive bacterium S. aureus at a detection limit of as low as 103cells per mL. Therefore, our CEE three-step method offered the significant advantages of short assay time, simple operating procedure, and higher sensitivity than previously reported methods of SERS-based bacteria detection.
authors.affiliation: College of Life Sciences & Bio-Engineering, Beijing University of Technology, Beijing 100124, PR China. sqwang@bmi.ac.cn and Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com.
authors.forename: Chongwen
authors.initials: C
authors.lastname: Wang
authors.affiliation: College of Mechatronics and Automation, National University of Defense Technology, Changsha, Hunan 410073, PR China.
authors.forename: Junfeng
authors.initials: J
authors.lastname: Wang
authors.affiliation: Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com and Henan University of Chinese Medicine, Zhengzhou, Henan 450008, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Li
authors.affiliation: Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com.
authors.forename: Xinyan
authors.initials: X
authors.lastname: Qu
authors.affiliation: Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com.
authors.forename: Kehan
authors.initials: K
authors.lastname: Zhang
authors.affiliation: Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Rong
authors.affiliation: Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com.
authors.forename: Rui
authors.initials: R
authors.lastname: Xiao
authors.affiliation: College of Life Sciences & Bio-Engineering, Beijing University of Technology, Beijing 100124, PR China. sqwang@bmi.ac.cn and Beijing Institute of Radiation Medicine, Beijing 100850, PR China. Rongzhen0525@sina.com ruixiao203@sina.com and Henan University of Chinese Medicine, Zhengzhou, Henan 450008, PR China.
authors.forename: Shengqi
authors.initials: S
authors.lastname: Wang