Characterization and quantification of nanoparticle-antibody conjugates on cells using C60 ToF SIMS in the event-by-event bombardment/detection mode

Li Jung Chen, Sunny S. Shah, Jaime Silangcruz, Michael J. Eller, Stanislav V. Verkhoturov, Alexander Revzin, Emile A. Schweikert

Research output: Contribution to journalArticlepeer-review

19 Scopus citations


Cluster C60 ToF-SIMS (time-of-flight secondary ion mass spectrometry) operated in the event-by-event bombardment-detection method has been applied to: (a) quantify the binding density of Au nanoparticles (AuNPs)-antiCD4 conjugates on the cell surface and (b) identify the binding sites between AuNPs and antibody. Briefly, our method consists of recording the secondary ions, SIs, individually emitted from a single C60 1,2+ impact. From the cumulative mass spectral data we selected events where a specific SI was detected. The selected records revealed the SIs co-ejected from the nanovolume impacted by an individual C60 with an emission area of ∼10 nm in diameter as an emission depth of 5-10 nm. The fractional coverage is obtained as the ratio of the effective number of projectile impacts on a specified sampling area (Ne) to the total number of impacts (No). In the negative ion mass spectrum, the palmitate (C16H31O2-) and oletate (C18H33O2-) fatty acid ions present signals from lipid membrane of the cells. The signals at m/z 197 (Au -) and 223 (AuCN-) originate from the AuNPs labeled antibodies (antiCD4) bound to the cell surface antigens. The characteristic amino acid ions validate the presence of antiCD4. A coincidence mass spectrum extracted with ion at m/z 223 (AuCN-) reveals the presence of cysteine at m/z 120, documenting the closeness of cysteine and the AuNP. Their proximity suggests that the binding site for AuNP on the antibody is the sulfur-terminal cysteine. The fractional coverage of membrane lipid was determined to be ∼23% of the cell surfaces while the AuNPs was found to be ∼21%. The novel method can be implemented on smaller size NPs, it should thus be applicable for studies on size dependent binding of NP-antibody conjugates.

Original languageEnglish (US)
Pages (from-to)97-102
Number of pages6
JournalInternational Journal of Mass Spectrometry
Issue number2-3
StatePublished - Jun 1 2011


  • AuNPs-antiCD4 conjugates
  • Biological surfaces
  • Cell micropatterns
  • Cluster SIMS
  • Quantification of bioconjugations

ASJC Scopus subject areas

  • Instrumentation
  • Condensed Matter Physics
  • Spectroscopy
  • Physical and Theoretical Chemistry


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