Hui-Fen Wu

Comparison of ZnS semiconductor nanoparticles capped with various functional groups as the matrix and affinity probes for rapid analysis of cyclodextrins and proteins in surface-assisted laser desorption/ionization time-of-flight mass spectrometry.

Zinc sulfide (ZnS) semiconductor nanoparticles (NPs) capped with a variety of functional groups including bare ZnS NPs, 3-mercaptopropanoic acid (ZnS-3-MPA), sodium citrate (ZnS-citrate), cysteamine (ZnS-Cys), and 2-mercaptoethane sulfonate (ZnS-2-MES) have been investigated as the matrix and affinity probes for analysis of alpha-, beta-, and gamma-cyclodextrins (CDs), ubiquitin, and insulin in biological samples by using surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF-MS). Various parameters that would influence the ionization efficiency and sensitivity of these ZnS NPs in SALDI-TOF-MS were examined including the effect of capping agents, sample pH, ion abundance, and concentration of ZnS NPs. Among these ZnS NPs, our results have demonstrated that ZnS-3-MPA exhibited the highest efficiency toward CDs, ubiquitin, and insulin for high-sensitivity detection in SALDI-TOF-MS. The detection limits were 20-55 nM for CDs, 91 nM for ubiquitin, and 85 nM for insulin. The applicability of the present method is demonstrated by detection of ubiquitin-like proteins in oyster mushroom and also in the analysis of analytes in biological samples such as human urine and plasma. To our best knowledge, this is the first time semiconductor NPs were used as the matrix and affinity probes for high-sensitivity detection of organic and biomolecules in SALDI-TOF-MS. This approach exhibits the advantages of being simple, rapid, efficient, and straightforward for direct analysis of organic and biological samples in SALDI-TOF-MS without the need for time-consuming separation processes, tedious washing steps, or further laborious purification. In addition, it also can provide a sensitive and reliable quantitative assay for small- and large-molecule analysis with the detectable mass up to 8500 Da. We believe that this novel ZnS nanoprobe is simple, efficient, lower cost (compared with Au, Ag, and Pt NPs), fast, and with the potential for high-throughput analysis in SALDI-TOF-MS.

Applications of silver nanoparticles capped with different functional groups as the matrix and affinity probes in surface‐assisted laser desorption/ionization time‐of‐flight and atmospheric pressure matrix‐assisted laser desorption/ionization ion trap mass spectrometry for rapid analysis of sulfur drugs and biothiols in human urine

A strategy is presented for the analysis of sulfur drugs and biothiols using silver nanoparticles (AgNPs) capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) and atmospheric pressure-matrix assisted laser desorption/ionization ion trap mass spectrometry (AP-MALDI-ITMS). Biothiols adsorbed on the surface of AgNPs through covalent bonding were subjected to ultraviolet (UV) radiation that enabled desorption and ionization due to the excellent photochemical property of NPs. The proposed method has been successfully applied for the determination of cysteine and homocysteine in human urine samples using an internal standard. The limit of detection (LOD) and limit of quantification (LOQ) for cysteine and homocysteine in urine sample are 7 and 22 nM, respectively, with a relative standard deviation (RSD) of <10%. The advantages of the present method compared with the methods reported in the literature for biothiol analysis are simplicity, rapidity and sensitivity without the need for time-consuming separation and tedious preconcentration processes. Additionally, we also found that the bare AgNPs can be directly used as the matrix in MALDI-TOF MS for the analysis of sulfur drugs without the addition of an extra proton source.

Quantum dots laser desorption/ionization MS: multifunctional CdSe quantum dots as the matrix, concentrating probes and acceleration for microwave enzymatic digestion for peptide analysis and high resolution detection of proteins in a linear MALDI-TOF MS

We report the first use of functionalized cadmium selinide quantum dots (CdSe QDs) with 11‐mercaptoundecanoic acid (MUA) as the matrix for the selective ionization of proteins with high resolution and rapid analysis of amino acids and peptides by using quantum dots laser desorption/ionization mass spectrometry (QDLDI‐MS). The mercaptocarboxylic groups of CdSe QDs have been known to be an effective affinity probe to interact with the biomolecules at low abundance level. Using these QDs as the matrix, sensitivity of the method was greatly enhanced and the LOQ of peptides was found to be 100 pM with RSD <10%. The QDLDI‐MS is capable for the selective ionization of insulin, lysozyme and myoglobin with high resolution, which is not observed with sinapic acid (SA) as the matrix. The QDLDI‐MS technique offers many advantages for the analysis of amino acids, peptides and proteins with regard to simplicity, rapidity, sensitivity and the mass spectra were generated in the presence of signal suppressors such as urea and Trition X‐100. In addition, the CdSe QDs have been successfully applied as preconcentrating probes for the analysis of digested peptides in lysozyme from chicken egg white by microwave‐assisted enzymatic digestion. This indicates that the QDs are able to absorb radiation from microwave and their ability to trap peptides from microwave‐digested lysozyme. These results demonstrate that the CdSe QDs are promising candidates for the selective ionization of the analytes with an accurate platform to the rapid screening of biomolecules.

Multifunctional graphene magnetic nanosheet decorated with chitosan for highly sensitive detection of pathogenic bacteria

Multifunctional graphene magnetic nanosheet decorated with chitosan (GMCS) is demonstrated as a promising biosensor for fluorescence spectroscopy and it can be also applied for matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) for sensitive pathogenic bacteria detection. Graphene-magnetic@chitosan (GMCS) can be applied for multiple applications such as fluorescence biosensor, fluorescence background suppressor, acting as co-matrix, enriching nanoprobe, and separation by external magnets for pathogenic bacteria (Pseudomonas aeruginosa and Staphylococcus aureus) present in aqueous suspension or blood colloids. GMCS has been prepared and characterized using various techniques including TEM, UV, FTIR, XRD, Raman and fluorescence spectroscopy. Due to the non-covalent interactions among the pathogenic bacteria with the GMCS, fluorescence enhancement takes place as a function of bacterial cell number with a low number of cell detection (4.5 × 102 to 5.0 × 102 cfu mL-1) and wide linear dynamic range which indicates that the GMCS approach is an excellent quantitative methodology and highly sensitive approach for detection of bacteria cells. Graphene works intrinsically as a fluorescence quencher for blood fluorophores and cell autofluorescence as graphene typically has a long life time, which allows detection of the bacteria signals by direct fluorescence measurements. Because of the high fluorescence enhancement efficiency, and large surface area (to volume ratio) of graphene, GMCS exhibits extraordinarily high sensitivity for complex (blood) sample analysis. GMCS also can be applied as an efficient separation and preconcentration nanoprobe for surface assisted laser desorption/ionization (SALDI) and enhances the ionization of bacterial biomolecules during MALDI-MS analysis. The bacterial cell suspension was concentrated from 1 mL to 10 μL via an external magnetic field, thus it can enhance bacteria detection for MALDI-MS analysis. GMCS is an outstanding approach which is a rapid, sensitive, culture free technique and low cost biosensor for pathogenic bacteria detection.

Platinum nanoparticles for the photothermal treatment of Neuro 2A cancer cells

This study demonstrates the effective synthesis of five different sized/shaped Pt NPs, within a narrow size regime of 1-21 nm using a modified methodology and the toxicity/biocompatibility of Pt NPs on Neuro 2A cancer cells was investigated elaborately by using light microscopic observations, tryphan blue exclusion assay, MTT assay and ICP-MS. The Pt NPs-C with sizes 5-6 nm showed superior non-cytotoxic property compared to the other four Pt NPs. These non-cytotoxic Pt NPs were employed for successful photothermal treatment of Neuro 2A cell lines using near-IR 1064 nm of laser irradiation. The Pt NPs-C could generate a 9 °C increase in temperature leading to effective photothermal killing of cancer cells. The MALDI-MS was used to prove the possibility of apoptosis related triggering of cell death in the presence of the Pt NPs. The results confirm that the current approach is an effective platform for in vivo treatment of neuro cancer cells.

Quantum dot applications endowing novelty to analytical proteomics.

This review surveys all the state‐of‐art applications of quantum dots (QDs) in conventional and modern analytical methods in proteomic studies. A brief introduction of QDs and their properties is initially presented followed by outlining the application of QDs in fluorescence, MS, imaging, and cancer‐based proteomics. The in‐depth application of QDs in MALDI‐MS and surface assisted laser desorption/ionization‐MS has been elaborately discussed, summarizing the speculated mechanism behind the protein–QDs interactions during QD matrix applications leading to enhanced detection sensitivity.

Multifunctional nanoparticles composite for MALDI-MS: Cd2+-doped carbon nanotubes with CdS nanoparticles as the matrix, preconcentrating and accelerating probes of microwave enzymatic digestion of peptides and proteins for direct MALDI-MS analysis.

For the first time, we utilized multifunctional nanoparticles composite (NPs composite) for matrix-assisted laser desorption/ionization mass spectrometric (MALDI-MS) analysis of peptides and proteins. Multiwalled carbon nanotubes doped with Cd(2+) ions and modified with cadmium sulfide NPs were synthesized by a chemical reduction method at room temperature. The multifunctional NPs composite applied for the analysis of peptides and microwave-digested proteins in the atmospheric pressure matrix-assisted laser desorption/ionization ion-trap and MALDI time-of-flight (TOF) mass spectrometry (MS) was successfully demonstrated. The maximum detection sensitivity for peptides in MALDI-MS was achieved by the adsorption of negatively charged peptides onto the surfaces of NP composite through electrostatic interactions. The optimal conditions of peptide mixtures were obtained at 20 min of incubation time using 1 mg of NPs composite when the pH of the sample solution was kept higher than the pI values of peptides. The potentiality of the NP composite in the preconcentration of peptides was compared with that of the individual NP by calculating the preconcentration factors (PF) and found that the NPs composite showed a 4-6 times of PF than the other NPs. In addition, the NPs composite was also applied as heat-absorbing materials for efficient microwave tryptic digestion of cytochrome c and lysozyme from milk protein in MALDI-TOF-MS analysis. We believe that the use of NPs composite technique would be an efficient and powerful preconcentrating tool for MALDI-MS for the study of proteome research.

A method to detect metal-drug complexes and their interactions with pathogenic bacteria via graphene nanosheet assist laser desorption/ionization mass spectrometry and biosensors.

A new method was proposed to probe the interactions between transition metals of Fe(II), Fe(III), Cu(II) with a non steroidal anti-inflammatory drug (NSAID), flufenamic acid (FF) using graphene as a matrix for Graphene assisted laser desorption ionization mass spectrometry (GALDI-MS). Metal-drug complexation was confirmed via UV absorption spectroscopy, fluorescence spectroscopy, pH meter, and change in solution conductivity. The optimal molar ratios for these complexation interactions are stoichiometry 1:2 in both Cu(II) and Fe(II) complexes, and 1:3 in Fe(III) complexes at physiological pH (7.4). Metal complexation of the drug could enhance fluorescence for 20 fold which is due to the charge transfer reaction or increase rigidity of the drug. The main interaction between graphene and flufenamic acid is the П-П interaction which allows us to probe the metal-drug complexation. The GALDI-MS could sensitively detect the drug at m/z 281.0 Da (protonated molecule) with detection limit 2.5 pmol (1.0 μM) and complexation at m/z 661.0, 654.0 and 933.0 Da corresponding to [Cu(II)(FF)(2)(H(2)O)(2)+H](+), [Fe(II)(FF)(2)(H(2)O)(2)+H](+) and [Fe(III) (FF)(3)(H(2)O)(2)+H](+), respectively (with limit of detection (LOD) 2.0 pmol (10.0 μM). Matrix assisted laser desorption ionization mass spectrometry (MALDI-MS) spectra show change in the protein profile of intact pathogenic bacteria (Pseudomonas aeroginosa, Staphylococcus aureus). The change in the ionization ability (mainly proton affinity) of pathogenic bacteria may be due to the interactions between the bacteria with the drug (or its complexes). Shielding carboxylic group by metals and increase the hydrophilicity could enhance the biocompatibility of complexes toward the pathogenic bacteria which can be used as biosensors with high sensitivity and lowest detectable concentrations are in the range of 3.3×10(3)-3.9×10(4) cfu mL(-1) with large linear dynamic range.

Bare silica nanoparticles as concentrating and affinity probes for rapid analysis of aminothiols, lysozyme and peptide mixtures using atmospheric-pressure matrix-assisted laser desorption/ionization ion trap and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The analysis of peptide mixtures from urine and plasma samples using bare (uncapped) SiO2 nanoparticles (NPs) with atmospheric-pressure matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) has been reported. The method was based on the adsorption of positively charged peptides on the surface of negatively charged SiO2 NPs through the electrostatic force of attraction. The adsorption on the surface of SiO2 NPs caused enhancement of ionization efficiency of analytes and subsequently increased the signal intensity of peptides. Maximum signal intensity was obtained at optimized concentration of SiO2 NPs and pH of the aqueous solution. The limits of detection (LODs) obtained for different peptides in deionized water with and without using SiO2 NPs were in the range 4.7-360 nM and 0.1-18.0 microM, respectively. The sensitivity of the proposed method was 21-53-fold better than conventional use of AP-MALDI-MS. In addition, linearity in the range 9.5-95 nM was obtained for the peptide angiotensin-II in deionized water with a correlation of estimation of 0.992 using an internal standard. The proposed method provided a simple way to facilitate the ionization of peptides, reduce sample complexity and increase the tolerance to salts and surfactants in the analysis of biological samples. The applicability of the present method was also demonstrated in the real-world sample analysis of aminothiols and lysozyme using MALDI-time-of-flight (TOF)-MS.

Near infrared (NIR) laser mediated surface activation of graphene oxide nanoflakes for efficient antibacterial, antifungal and wound healing treatment.

Photothermal treatment of graphene oxide (GO) for antibacterial, antifungal and controlling the wound infection treatment using near infrared laser (NIR, Nd-YAG (λ=1064 nm) were reported. Various pathogenic bacteria (Pseudomonas aeruginosa, Staphylococcus aureus) and fungi (Saccharomyces cerevisiae and Candida utilis) were investigated. The cytotoxicity was measured using the proteomic analysis by matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS), optical density (OD600), standard microdilution procedures, transmission electron microscopy (TEM) and epifluorescence microscopy. The laser mediated the surface activation of GO offer high efficiency for antifungal and antibacterial. Wide broad cells with various instruments approved that graphene oxide is promising material for nanomedicine in the near future.