Multifunctional Au nano-bridged nanogap probes as ICP-MS/SERS dual-signal tags and signal amplifiers for bacteria discriminating, quantitative detecting and photothermal bactericidal activity.

Ultra-sensitive detection of pathogenic bacteria is of great significance in the early stage of bacterial infections and treatment. In this work, we report a novel strategy using multifunctional Au nano-bridged nanogap nanoparticles (Au NNPs)-based sandwich nanocomposites, that made of Concanavalin A-conjugated Fe3O4@SiO2 NPs (ConA-Fe3O4@SiO2 NPs)/bacteria/aptamer-modified Au NNPs (apt-Au NNPs), for bacteria discrimination and quantitative detection by surface-enhanced Raman scattering (SERS) and inductively coupled plasma mass spectrometry (ICP-MS), and subsequently photothermal antibacterial assay. The sandwich nanocomposite consists of ConA-Fe3O4@SiO2 NPs to magnetically enrich and photothermal killing bacteria, and dual-signal tags of apt-Au NNPs for both SERS sensing and ICP-MS quantification. This strategy can specifically distinguish different kinds of pathogenic bacteria, and provided a good linear relationship of Staphylococcus aureus (S. aureus) in the range from 50 to 104 CFU/mL with a detection limit of 11 CFU/mL, as well as realized ultralow amounts of bacterial detection in serum sample with high accuracy. Based on the quantitative detection, high antibacterial efficiency was monitored by ICP-MS. Overall, the established method combines bacteria discrimination, quantitative detection, and photothermal elimination with a simple and rapid process, which provides a novel way for the early diagnosis and treatment of bacterial infection.

Triple-Function Au-Ag-Stuffed Nanopancakes for SERS Detection, Discrimination, and Inactivation of Multiple Bacteria.

New strategies combining sensitive pathogenic bacterial detection and high antimicrobial efficacy are urgently desirable. Here, we report smart triple-functional Au-Ag-stuffed nanopancakes (AAS-NPs) exhibiting (1) controllably oxidative Ag-etching thickness for simultaneously obtaining the best surface-enhanced Raman scattering (SERS) enhancement and high Ag-loading antibacterial drug delivery, (2) expressive Ag+-accelerated releasing capability under neutral phosphate-buffered saline (PBS) (pH ∼ 7.4) stimulus and robust antibacterial effectiveness involving sustainable Ag+ release, and (3) three-in-one features combining specific discrimination, sensitive detection, and inactivation of different pathogenic bacteria. Originally, AAS-NPs were synthesized by particle growth of the selective Ag-etched Au@Ag nanoparticles with K3[Fe(CN)6], followed by the formation of an unstable Prussian blue analogue for specifically binding with bacteria through the cyano group. Using specific bacterial "fingerprints" resulting from the introduction of dual-function 4-mercaptophenylboronic acid (4-MPBA, serving as both the SERS tag and internal standard) and a SERS sandwich nanostructure that was made of bacteria/SERS tags/AAS-NPs, three bacteria (E. coli, S. aureus, and P. aeruginosa) were highly sensitively discriminated and detected, with a limit of detection of 7 CFU mL-1. Meanwhile, AAS-NPs killed 99% of 1 × 105 CFU mL-1 bacteria within 60 min under PBS (pH ∼ 7.4) pretreatment. Antibacterial activities of PBS-stimulated AAS-NPs against S. aureus, E. coli, and P. aeruginosa were extraordinarily increased by 64-fold, 72-fold, and 72-fold versus PBS-untreated AAS-NPs, respectively. The multiple functions of PBS-stimulated AAS-NPs were validated by bacterial sensing, inactivation in human blood samples, and bacterial biofilm disruption. Our work exhibits an effective strategy for simultaneous bacterial sensing and inactivation.

Efficient sample clean-up and online preconcentration for sensitive determination of melamine in milk samples by capillary electrophoresis with contactless conductivity detection.

Based on an efficient sample clean-up and field-amplified sample injection online preconcentration technique in capillary electrophoresis with contactless conductivity detection, a new analytical method for the sensitive determination of melamine in milk samples was established. In order to remove the complex matrix interference, which resulted in a serious problem during field-amplified sample injection, liquid-liquid extraction was utilized. As a result, liquid-liquid extraction provides excellent sample clean-up efficiency when ethyl acetate was used as organic extraction by adjusting the pH of the sample solution to 9.5. Both inorganic salts and biological macromolecules are effectively removed by liquid-liquid extraction. The sample clean-up procedure, capillary electrophoresis separation parameters and field-amplified sample injection conditions are discussed in detail. The capillary electrophoresis separation was achieved within 5 min under the following conditions: an uncoated fused-silica capillary, 12 mM HAc + 10 mM NaAc (pH = 4.6) as running buffer, separation voltage of +13 kV, electrokinetic injection of +12 kV × 10 s. Preliminary validation of the method performance with spiked melamine provided recoveries >90%, with limits of detection and quantification of 0.015 and 0.050 mg/kg, respectively. The relative standard deviations of intra- and inter-day were below 6%. This newly developed method is sensitive and cost effective, therefore, suitable for screening of melamine contamination in milk products.

Integrin-targeted trifunctional probe for cancer cells: a "seeing and counting" approach.

We report the design and synthesis of a trifunctional probe for seeing and counting cancer cells using both fluorescence imaging (FI) and inductively coupled plasma mass spectrometry (ICPMS) for the first time. It consisted of a guiding cyclic RGD peptide unit to catch cancer cells via targeting the α(v)ß(3) integrin overexpressed on their surface, a 5-amino-fluorescein moiety for FI using confocal laser scanning microscopy (CLSM) as well as a 2-aminoethyl-monoamide-DOTA group for loading stable europium ion and subsequent ICPMS quantification of the cancer cells without the use of radioactive isotopes. In addition to FI, the LOD (3σ) of the α(v)ß(3) integrin was down to 69.2-309.4 amol per cell depending on the type of the α(v)ß(3)-positive cancer cells when using ICPMS and those of the cancer cell number reached 17-75. This probe developed enables us not only to see but also to count the α(v)ß(3)-positive cancer cells ultrasensitively, paving a new way for early diagnosis of cancer.

Europium-labeled activity-based probe through click chemistry: absolute serine protease quantification using (153)Eu isotope dilution ICP/MS.

Click and analyze: the titled probe was synthesized by conjugating a sulfonyl fluoride and azido unit using click chemistry to give SF-Eu, which can react specifically with serine (Ser) in the active site of serine protease (SP). Combination of the method with (153)Eu-isotope dilution ICP/MS enables absolute protein quantification of active SPs in biological samples using only one (153)Eu(NO(3))(3) isotopic standard.