TY - JOUR
T1 - Characterization and quantification of nanoparticle-antibody conjugates on cells using C60 ToF SIMS in the event-by-event bombardment/detection mode
AU - Chen, Li Jung
AU - Shah, Sunny S.
AU - Silangcruz, Jaime
AU - Eller, Michael J.
AU - Verkhoturov, Stanislav V.
AU - Revzin, Alexander
AU - Schweikert, Emile A.
N1 - Funding Information:
This work was supported by the National Science Foundation (Grant-CHE 0750377 to EAS) and by the National Institutes of Health (Grant-EB 006519 to AR). The scanning electron microscope (SEM) images were taken in the Materials and Characterization Facility in Texas A&M University.
PY - 2011/6/1
Y1 - 2011/6/1
N2 - 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.
AB - 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.
KW - AuNPs-antiCD4 conjugates
KW - Biological surfaces
KW - Cell micropatterns
KW - Cluster SIMS
KW - Quantification of bioconjugations
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U2 - 10.1016/j.ijms.2011.01.001
DO - 10.1016/j.ijms.2011.01.001
M3 - Article
AN - SCOPUS:79955884823
SN - 1387-3806
VL - 303
SP - 97
EP - 102
JO - International Journal of Mass Spectrometry
JF - International Journal of Mass Spectrometry
IS - 2-3
ER -