Plasmonically-enhanced competitive assay for ultrasensitive and multiplexed detection of small molecules

Zheyu Wang, Qingjun Zhou, Anushree Seth, Samhitha Kolla, Jingyi Luan, Qisheng Jiang, Priya Rathi, Prashant Gupta, Jeremiah J. Morrissey, Rajesh R. Naik, Srikanth Singamaneni

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


Novel methods that enable facile, ultrasensitive and multiplexed detection of low molecular weight organic compounds such as metabolites, drugs, additives, and organic pollutants are valuable in biomedical research, clinical diagnosis, food safety and environmental monitoring. Here, we demonstrate a simple, rapid, and ultrasensitive method for detection and quantification of small molecules by implementing a competitive immunoassay with an ultrabright fluorescent nanolabel, plasmonic fluor. Plasmonic-fluor is comprised of a polymer-coated gold nanorod and bovine serum albumin conjugated with molecular fluorophores and biotin. The synthesis steps and fluorescence emission of plasmonic-fluor was characterized by UV–vis spectroscopy, transmission electron microscopy, and fluorescence microscopy. Plasmon-enhanced competitive assay can be completed within 20 min and exhibited more than 30-fold lower limit-of-detection for cortisol compared to conventional competitive ELISA. The plasmon-enhanced competitive immunoassay when implemented as partition-free digital assay enabled further improvement in sensitivity. Further, spatially multiplexed plasmon-enhanced competitive assay enabled the simultaneous detection of two analytes (cortisol and fluorescein). This simple, rapid, and ultrasensitive method can be broadly employed for multiplexed detection of various small molecules in research, in-field and clinical settings.

Original languageEnglish
Article number113918
JournalBiosensors and Bioelectronics
StatePublished - Mar 15 2022


  • Competitive assay
  • Multiplexed detection
  • Plasmonic enhanced fluorescence
  • Small molecule detection


Dive into the research topics of 'Plasmonically-enhanced competitive assay for ultrasensitive and multiplexed detection of small molecules'. Together they form a unique fingerprint.

Cite this