Yu-Chie Chen

Functional Fe3O4/TiO2 Core/Shell Magnetic Nanoparticles as Photokilling Agents for Pathogenic Bacteria

A photokilling approach for pathogenic bacteria is demonstrated using a new type of magnetic nanoprobe as the photokilling agent. In addition to their magnetic property, the nanoprobes have other features including a photocatalytic property and the capacity to target bacteria. The nanoprobes comprise iron oxide/titania (Fe(3)O(4)@TiO(2)) core/shell magnetic nanoparticles. As dopamine molecules can self-assemble onto the surface of the titania substrate, dopamine is used as the linker to immobilize succinic anhydride onto the surfaces of the Fe(3)O(4)@TiO(2) nanoparticles. This is followed by the immobilization of IgG via amide bonding. We demonstrate that the IgG-Fe(3)O(4)@TiO(2) magnetic nanoparticles not only have the capacity to target several pathogenic bacteria, but they also can effectively inhibit the cell growth of the bacteria targeted by the nanoparticles under irradiation of a low-power UV lamp within a short period. Staphylococcus saprophyticus, Streptococcus pyogenes, and antibiotic-resistant bacterial strains, such as multiantibiotic-resistant S. pyogenes and methicillin-resistant Staphylococcus aureus (MRSA), are used to demonstrate the feasibility of this approach.

Functional gold nanoparticles as photothermal agents for selective-killing of pathogenic bacteria

AIMS Our aim was to demonstrate that functional gold nanoparticles can be used as photothermal agents for the selective killing of pathogenic bacteria. MATERIALS & METHODS Gold nanoparticles with polygonal shapes, capable of absorbing near infrared (NIR) light, were generated through a photochemical reaction. Vancomycin, which can bind with the terminal D-Ala-D-Ala moieties of the peptide units of pathogen cell walls, was immobilized on the surface of the gold nanoparticles. The vancomycin-bound gold nanoparticles were used as the photothermal agents for the inhibition of pathogenic bacteria growth, under irradiation of NIR light (808 nm). RESULTS & DISCUSSION We have demonstrated that vancomycin-bound gold nanoparticles are capable of selective-binding onto the cell walls of pathogenic bacteria. A large portion (>99%) of bacteria targeted by the gold nanoparticles was destroyed under illumination by NIR light within 5 min owing to suffering from heating. CONCLUSIONS This photothermal approach is effective for the inhibition of pathogenic bacteria cell growth, including Gram-positive bacteria, Gram-negative bacteria and antibiotic-resistant bacteria.

Affinity Capture of Uropathogenic Escherichia coli Using Pigeon Ovalbumin-Bound Fe3O4@Al2O3 Magnetic Nanoparticles

Escherichia coli and Staphylococcus saprophyticus are the most common causes of urinary tract infections, with 80% of these infections caused by uropathogenic E. coli. Because the P fimbriae of E. coli have specificity toward Gal(alpha1-4)Gal beta units, pigeon ovalbumin (POA), whose structure contains terminal Gal(alpha1-4)Gal beta moieties, was used as a probe for interaction with P fimbriated E. coli. The functional affinity probes for these bacteria by immobilizing POA--a phosphoprotein--onto the surface of magnetic iron oxide nanoparticles (NPs) coated with alumina (Fe3O4@Al2O3), using the phosphate units of POA as linking groups for the formation of phosphate-alumina complexes. The immobilization process occurred within 30 s when performing the reaction under microwave heating. The magnetic POA-Fe3O4@Al2O3 NPs generated using this facile approach exhibited specificity toward P fimbriated E. coli. The bacteria targeted by the affinity probes were characterized by matrix-assisted laser desorption/ionization mass spectrometry. The detection limit toward uropathogenic bacteria when using this approach was approximately 9.60 x 10(4) cfu/mL (0.5 mL).

Glutathione-bound gold nanoclusters for selective-binding and detection of glutathione S-transferase-fusion proteins from cell lysates

A straightforward method for the rapid detection of the presence of glutathione S-transferase (GST)-tagged proteins from sample solutions using glutathione (GSH)-bound gold nanoclusters (Au@GSH NCs) with luminescence properties as the detection probes by simple observation with the naked eye was proposed in this study.

Functional gold nanoclusters as antimicrobial agents for antibiotic-resistant bacteria

AIMS Our aim was to demonstrate that lysozyme-directed generation of gold nanoclusters (Au NCs) are potential antimicrobial agents for antibiotic-resistant bacteria and broad labeling agents for pathogenic bacteria. MATERIALS & METHODS Lysozyme is an enzyme that is capable of hydrolyzing the cell walls of bacteria. In this study, we demonstrated the generation of functional Au NCs by using lysozyme as the sequester and the reducing agent for Au precursors at 40 degrees C. In addition, to shorten the reaction time, the reaction was conducted under microwave irradiation within a short period of time for the first time. RESULTS The bioactivity of the lysozyme on the Au NCs was retained. Therefore, the as-prepared lysozyme-Au NCs with desirable fluorescence feature were successfully employed to be broad-band labeling agents for pathogenic bacteria. Furthermore, we also demonstrated that the lysozyme-Au NCs can be used to effectively inhibit the cell growth of notorious antibiotic-resistant bacteria, including pan-drug-resistant Acinetobacter baumannii and vancomycin-resistant Enterococcus faecalis. CONCLUSION The potential of employing the lysozyme-Au NCs for bacterial labeling and as antimicrobial agents is expected.

Functional Nanoparticle-Based Proteomic Strategies for Characterization of Pathogenic Bacteria

Although matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) can be employed to rapidly characterize pathogenic bacteria, bacterial cultures are generally required to obtain sufficient quantities of the bacterial cells prior to MALDI MS analysis. If this time-consuming step could be eliminated, the length of time required for identification of bacterial strains would be greatly reduced. In this paper, we propose an effective means of rapidly identifying bacteria--one that does not require bacterial culturing--using functional nanoparticle-based proteomic strategies that are characterized by extremely short analysis time. In this approach, we used titania-coated magnetic iron oxide nanoparticles (Fe(3)O(4)@TiO(2) NPs) as affinity probes to concentrate the target bacteria. The magnetic properties of the Fe(3)O(4)@TiO(2) NPs allow the conjugated target species to be rapidly isolated from the sample solutions under a magnetic field. Taking advantage of the absorption of the magnetic Fe(3)O(4) NPs in the microwave region of the electromagnetic spectrum, we performed the tryptic digestion of the captured bacteria under microwave heating for only 1-1.5 min prior to MALDI MS analysis. We identified the resulting biomarker ions by combining their MS/MS analysis results with protein database searches. Using this technique, we identified potential biomarker ions representing five gram-negative bacteria: Escherichia coli O157:H7, uropathogenic E. coli, Shigella sonnei, Pseudomonas aeruginosa, and Klebsiella pneumoniae. Finally, we demonstrated the practical feasibility of using this approach to rapidly characterize bacteria in clinical samples.

Human serum albumin stabilized gold nanoclusters as selective luminescent probes for Staphylococcus aureus and methicillin-resistant Staphylococcus aureus.

In this work, human serum albumin (HSA) stabilized gold nanoclusters (HSA-AuNCs) with reddish photoluminescence were used as sensing probes for pathogenic bacteria including Enterobacter cloacae, Escherichia coli J96, Pseudomonas aeruginosa, pandrug-resistant Acinetobacter baumannii (PDRAB), Staphylococcus aureus, methicillin-resistant S. aureus (MRSA), Streptococcus pyogenes, and vancomycin-resistant Enterococcus faecalis (VRE). We discovered that HSA-AuNCs have unique affinity with S. aureus and MRSA. In addition to demonstrating the selective sensing ability of HSA-AuNCs toward S. aureus and MRSA, the binding peptide motifs identified from HSA-AuNCs were characterized by mass spectrometry. The identified binding peptides were further used as the reducing and stabilizing agents for generation of peptide-bound AuNCs (Pep-AuNCs). The generated Pep-AuNCs were demonstrated to have the binding affinities with S. aureus and MRSA.

Rapid determination of trace nitrophenolic organics in water by combining solid-phase extraction with surface-assisted laser desorption/ionization time-of-flight mass spectrometry

A rapid technique for the screening of trace compounds in water by combining solid-phase extraction (SPE) with activated carbon surface-assisted laser desorption/ionization (SALDI) time-of-flight mass spectrometry is demonstrated. Activated carbon is used both as the sorbent in SPE and as the solid in the SALDI matrix system. This eliminates the need for an SPE elution process. After the analytes have been adsorbed on the surfaces of the activated carbon during SPE extraction, the activated carbon is directly mixed with the SALDI liquid and mass spectrometric analysis is performed. Trace phenolic compounds in water were used to demonstrate the effectiveness of the method. The detection limit for these compounds is in the ppb to ppt range.

Nanomaterials for Photohyperthermia: A Review

The unique properties of nanomaterials have propelled the field of nanomedicine. Nanomaterials have been used as drug delivery, imaging, and photothermal agents for diagnosis and therapy of diseases. Recently, photohyperthermia has attracted great interest from researchers and is actively being investigated as an alternative method of therapy for cancer and even bacteria. Photohyperthermia, or photothermal therapy, is the process of a photothermal agent absorbing light and converting it into heat for the destruction of malignant cells, which is due to elevated temperatures. This technique is non-invasive, can target specific diseased cells for minimal adverse side effects, and can be used in conjunction with other cancer treatments, such as chemotherapy. In this review, we will discuss different nanomaterials that have been implemented as photothermal agents for the treatment of various cancer and bacterial cells. The review will mainly focus on gold nanoparticles, magnetic nanoparticles, and carbon nanotubes. However, other nanomaterials, such as semiconductor nanoparticles and polymer composites, will be briefly discussed. In addition, the photothermal mechanism, current developments, dual imaging and therapy, and future perspectives of nanoparticle-based photohyperthermia will be presented.

Ultrasonication-assisted spray ionization mass spectrometry for on-line monitoring of organic reactions

A straightforward on-line monitoring of organic reactions by ultrasonication-assisted spray ionization mass spectrometry (UASI MS) is demonstrated in this work.