Biomedical Engineering Reference
In-Depth Information
Nps Capping agent a Size (nm) Analyte b LOD Ref.
Pt No Nanolower Angiotensin I <0.7 fmol 49
Pt No Nanolower Insulin <5 fmol 49
Pt No Nanolower Cytochrome c <20 fmol 49
Pt No <2−5 Substance P <2.5 pmol 50
Pt No <2−5 Angiotensin I <2.5 pmol 50
a 4-ATP, 4-aminothiophenol; 4-MBA, 4-mercaptobenzoic acid; CHCA, α-cyano-4-
hydroxycinnanic acid; NG, not given.
b DDAC, dimethyldioctadecylammonium chloride; CD, cyclodextrin; ATP, adenosine
triphosphate; BSA, bovine serum albumin.
In addition to the use of inorganic materials as matrices, surface-
functionalized micro- and nanomaterials have also been widely used
as afinity probes to simultaneously enrich and isolate the target
species through Columbic interaction, hydrophobic adsorption,
and/or molecular biorecognition. Flocculated and trapped mixtures
can be either directly detected using nanomaterials or mixed
separately with organic molecules, such as sinapinic acid and 2,5-
dihydroxybenzoic acid. Thus, the type of NPs and suspended liquids
play important roles in determining the MS sensitivity and selectivity.
In the following sections, we introduce different kinds of noble metal
nanomaterials and their successful examples in LDI-MS.
12.2.1 Gold
Because the preparation of citrate-capped AuNPs (citrate-AuNPs)
is easy, low-cost, and reproducible, they are one of the most
popular materials for LDI-MS. Russell et al . examined the effect of
the size of citrate-AuNPs on the ionization eficiency of peptides. 21
It is found that small AuNPs (~2 nm) could afford high sensitivity
and low background interferences (i.e., Au-clusters species) for
peptides compared to large AuNPs (5 and 10 nm). Tseng et al . have
demonstrated that citrate-AuNPs possess high-salt tolerance for
the analysis of biomolecules by LDI-MS. 22 This observation can be
extended to the analysis of small molecules in urine samples. In
contrast to dried-droplet method, layer-by-layer self-assembled
multilayers ilms of citrate-AuNPs on a silicon wafer could increase
detection sensitivity and mass range, thus making it possible to
detect subfemtomoles angiotensin I and cytochrome c (12 kDa). 23
 
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