title: Counting bacteria using functionalized gold nanoparticles as the light-scattering reporter.
abstract: A simple and rapid bacterial counting method was developed based on dark-field light-scattering imaging of bacteria and gold nanoparticle (AuNP) reporter simultaneously. Commercially available DH5α  E. coli  strain was used as the model bacterium to demonstrate the feasibility of the proposed method. With antibody-conjugated AuNPs, the simple sample treatment and target  E. coli  strain recognition can be finished within 15-30 min, with a detection limit of 2-6 × 10(4) colony forming unit per milliliter (CFU/mL). By using 90 nm AuNPs as the light-scattering signal reporter, the bacterial recognition and counting can be easily performed with low-cost instrumentation such as an entry-level dark-field microscope setup and a common tungsten lamp as the light source. An automatic image analysis algorithm was also developed to facilitate robust and fast bacterial counting. The preliminary results of water, milk, and fruit juice sample analysis showed that this simple, fast, and cost-effective method can be easily adopted for routine bacterial detection.
authors.affiliation: Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Analytical Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Xu
authors.forename: Yang
authors.initials: Y
authors.lastname: Chen
authors.forename: Hejia
authors.initials: H
authors.lastname: Wei
authors.forename: Bin
authors.initials: B
authors.lastname: Xia
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Na
authors.initials: N
authors.lastname: Li
mesh_terms: D000465:Algorithms; D000818:Animals; D000907:Antibodies, Bacterial / Q000737:chemistry / Q000276:immunology; D058491:Bacterial Load / Q000379:methods*; D001628:Beverages / Q000382:microbiology; D003624:Darkness; D004926:Escherichia coli / Q000166:cytology / Q000276:immunology / Q000302:isolation & purification*; D005240:Feasibility Studies; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008892:Milk / Q000382:microbiology; D057054:Molecular Imaging; D012542:Scattering, Radiation; D013499:Surface Properties; D013997:Time Factors
chemical_list: D000907:Antibodies, Bacterial; D006046:Gold