Mass Spectrometric Bioanalysis Assisted by Noble Metal Nanoparticles - From Bioimaging to Biosensors: Noble Metal Nanoparticles in Biodetection - page 286

be used for microarray detection, Zhang et al . reported the detection
of multiple proteins — α-fetoprotein IgG, carcinoembryonic antigen,
and human IgG — on each spot of the immuno-microarray by laser
ablation ICP-MS. 73 Based on sandwich-type immunoreaction, three
proteins were detected using Sm 3+ -labeled α-fetoprotein antibody,
Eu 3+ -labeled carcinoembryonic antibody, and AuNP-labeled goat-
anti-human IgG as labeled antibodies; the LODs for α-fetoprotein
IgG, carcinoembryonic antigen, and human IgG were 0.20, 0.14, and
0.012 ng/mL, respectively.
12.5 Conclusions
The use of noble metal NPs has been shown to be capable of (a)
enhancing ionization eficiency in LDI-MS and SIMS, (b) suppressing
background signal of low-mass region in LDI-MS, (c) improving
detection reproducibility in LDI-MS, (d) selectively ionizing speciic
analytes in LDI-MS, and (e) extending the detectable mass range
in SIMS. The detection sensitivity of target antigen can be greatly
improved when using NP-tagged antibody as a secondary antibody
and ICP-MS as a detection and quantiication tool. In addition, before
the analysis of LDI-MS, metal NPs can act as afinity probes for the
extraction of target analytes. However, there are still several areas
in which they can be improved. Metal NP-assisted LDI-MS and metal
NP-enhanced SIMS are both typically limited to the detection of high
molecular weight analytes. If the detectable mass range could be
extended to 50,000 or 100,000 Da, these methods would be more
suitable for proteomic analysis. In our opinion, the development of
new nanomaterials with high energy transfer would be possible to
achieve this goal. Moreover, when applying metal NP-assisted LDI-MS
and metal NP-enhanced SIMS to the analysis of biological samples such
as urine, tear, serum, and cerebrospinal luids, the detection of target
analytes commonly suffer from non-speciic adsorption and complex
matrix such as high salt and abundant proteins. To circumvent these
problems, it is suggested that solid-phase extraction and liquid
separation (i.e., liquid chromatography, capillary electrophoresis,
etc.) may be required prior to MS analysis. Alternatively, conjugated
NPs with high selectivity may be straightforward to simplify analysis
procedure. For example, NPs decorated with poly(ethylene glycol)
and antibody should provide high selectivity toward target antigen.