Optical biosensing of Streptococcus agalactiae based on core/shell magnetic nanoparticle-quantum dot

  • Razieh Ghasemi
  • Seyede Zohreh Mirahmadi-zareEmail author
  • Mohammad Hossein Nasr-Esfahani
  • Alireza Allafchian
  • Mehrdad BehmaneshEmail author
Research Paper


An immunomagnetic optical probe based on a core/shell magnetic nanoparticle–quantum dot was fabricated for detection of Streptococcus agalactiae, the causative agent of pneumonia and meningitis in newborns. The silica-coated magnetic nanoparticles conjugated with anti-S. agalactiae monoclonal antibody provided high specificity for pre-enrichment of bacteria from biological samples with a complex matrix such as milk. Compared with conventional methods such as culture and molecular techniques, the combination of fluorescent quantum dot and magnetic nanoparticle enhanced the sensitivity and speed of bacterial identification. The bio-functionalized fluorescent-magnetic nanoparticles were characterized by TEM, SEM, VSM, XRD, DLS, and FTIR and applied to the detection of S. agalactiae with a limit of 10 and 102 CFU/mL in PBS and milk, respectively. This immunomagnetic optical probe can be used for rapid isolation, sensitive, and specific detection of targeted bacteria without any treatment in clinical and animal samples in the presence of other infectious agents.


Fluorescent magnetic nanocomposite Quantum dots Bacteria Antibody Bioconjugation Immunomagnetic optical probe 





Antibody-conjugated FMNPs


Fluorescent-magnetic nanocomposite


Magnetic nanoparticles


Quantum dots



We are grateful for the financial support from the Iran National Institute for Medical Research Development (NIMAD) (Grant No. 940990).

Compliance with ethical standards

Conflict of interest

The authors confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.


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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2019

Authors and Affiliations

  • Razieh Ghasemi
    • 1
    • 2
  • Seyede Zohreh Mirahmadi-zare
    • 2
    Email author
  • Mohammad Hossein Nasr-Esfahani
    • 2
  • Alireza Allafchian
    • 3
  • Mehrdad Behmanesh
    • 1
    • 4
    Email author
  1. 1.Department of Nanobiotechnology, Faculty of Biological SciencesTarbiat Modares UniversityTehranIran
  2. 2.Department of Molecular Biotechnology, Cell Science Research Center, Royan Institute for BiotechnologyACECRIsfahanIran
  3. 3.Research Institute for Nanotechnology and Advanced MaterialsIsfahan University of TechnologyIsfahanIran
  4. 4.Department of Genetic, Faculty of Biological SciencesTarbiat Modares UniversityTehranIran

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