Silver-coated gold nanoparticles as concentrating probes and matrices for surface-assisted laser desorption/ionization mass spectrometric analysis of aminoglycosides

Abstract

A novel method for the determination of aminoglycosides by surface-assisted laser desorption/ ionization mass spectrometry (SALDI MS) with the aid of silver-coated gold nanoparticles (Au@AgNPs) has been developed. The Au@AgNPs with surface capped by anionic citrate were used as concentrating probes as well as matrices in SALDI MS. Adsorption of aminoglycosides onto the nanoparticles was mainly through electrostatic attraction. The aminoglycoside-adsorbed nanoparticles were directly characterized by SALDI MS after a simple washing. Using Au@AgNPs to preconcentrate the aminoglycosides from 500 L buffer solution, the limits of detection (LODs) at signal-to-noise ratio of 3 were 3, 25, 15, 30, and 38 nM for paromomycin, kanamycin A, neomycin, gentamicin, and apramycin, respectively. This method was successfully applied to the determination of aminoglycosides in human plasma samples. The LODs of aminoglycosides in plasma samples were 9, 130, 81, and 180 nM for paromomycin, kanamycin A, neomycin, and gentamicin, respectively. Recoveries of aminoglycosides in plasma samples were about 80%. (J Am Soc Mass Spectrom 2009, 20, 1925-1932) © 2009 American Society for Mass Spectrometry R ecently, surface-assisted laser desorption/ionization mass spectrometry (SALDI MS) has become a popular technique due to the rapid development of nanomaterials. Nanoparticles have been recognized as effective SALDI matrices because of their large surface area-to-volume ratio, ease of sample preparation, flexibility of sample deposition, and no dependence on the irradiation wavelength. Gold and Nile-red adsorbed gold nanoparticles were used as SALDI matrix for the mass spectrometric determination of aminothiols [7], and TiO 2 -coated magnetic nanoparticles [8] were also employed for the analysis of peptides and proteins. The mass range could be extended to 24 KDa with the use of nanoparticles as matrices, and the detection limit for peptide is about 20 fmol. In addition, titanium dioxide [9], silver [10], and silicon nanoparticles [11] successfully desorbed and ionized enediol compound, olefin, and small molecules, respectively. The use of nanoparticles as SALDI matrices not only eliminates matrix ion interference but also improves sample homogeneity. Sweet-spot searching is not required, therefore better shot-to-shot and sampleto-sample reproducibility is obtained.To improve the sensitivity and minimize the interferences of sample matrix, the nanoparticles were also used as concentrating probes to separate and concentrate the analytes from complex biologic samples before SALDI MS analysis. The surface of the nanoparticle was modified for the selective retention of analyte while removing interferences through simple washing. The collected analyte-adsorbed nanoparticles were either analyzed directly by SALDI/MS or mixed with conventional organic matrices, such as sinapinic acid (SA) and ␣-cyano-4-hydroxycinnamic acid (CHCA), for their matrix-assisted laser desorption/ionization (MALDI) MS analysis.

Imaging mass spectrometry with silver naeoparticles reveals the distribution of fatty acids in mouse retinal sections

“…The LOD value was determined at a signal-to-noise (S/N) ratio of 3. The value of 3 has been used to evaluate the LOD in another study [16]. The peaks at m/z 255.3 corresponding to palmitic acid are indicated by arrows.…”

“…The core metal and functional groups of the NPs can be modified to ionize analytes on the basis of specific chemical properties. The core metals gold [11], silver [12][13][14], titanium dioxide [15], and their mixture [16] have been used in SALDI-MS analysis. SALDI-MS analyses using their NPs have detected analytes that are different from those used in general matrices or to enhance the signal intensities from the molecules.…”

Influence of surface melting effects and availability of reagent ions on LDI-MS efficiency after UV laser irradiation of Pd nanostructures

“…Metal substrates are expected to exhibit a lower tolerance to laser irradiation as compared with carbon‐based materials, which, assuming the phase transition model also applies, should lead to increased LDI efficiency. Metal targets have not been popular for LDI, because other materials, such as carbon‐based substrates (including diamond NPs), have generally shown better performance in comparison to metal targets …”

Silver Oxide Based Nanoparticle Assisted Laser Desorption/Ionization Mass Spectrometry for the Detection of Low Molecular Weight Compounds

“…Gold nanoparticles can be used to modify functional thiol compounds 8) or coat a silver layer 9) and, hence, can be used as a nity probes. e use of silver nanoparticles in conjunction with LDI 10,11) has been reported to result in the selective ionization of ole nic target molecules.…”