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Carbon dots (C-dots) are fluorescent nanomaterials that possess good photostability and low toxicity. They have been used as sensing probes and bioimaging agents for a variety of ...biological species. Numerous methods are available to generate C-dots. Nevertheless, simple and straightforward synthesis methods must be explored for the synthesis of C-dots from inexpensive, natural sources. In this study, we developed a simple method to generate C-dots from inexpensive chicken egg whites through a one-step heating reaction. The size of the generated C-dots was 3.3±0.4nm, and the quantum yield of the C-dots was as high as ∼43%. The as-prepared C-dots can be used as multicolor labeling agents for bacteria such as Staphylococcus aureus and Escherichia coli. Furthermore, the generated C-dots can be used as Förster resonance energy transfer sensing probes for curcumin, which is an active ingredient of turmeric and medicinal pigment. The feasibility of using the C-dots as selective sensing probes to determine the amount of curcumin from complex turmeric powder and condensed turmeric tablets is also demonstrated.
In this study, we generated gold nanoclusters (AuNCs) using inexpensive chicken egg white proteins (AuNCs@ew) as reagents. AuNCs@ew were generated by reacting aqueous tetrachloroauric acid with ...diluted chicken egg white under microwave heating (90W) through subsequent heating cycles (5min/cycle). Within 10 cycles, red photoluminescent AuNCs@ew with maximum emission wavelength at ~640nm (λex=370nm) were obtained. The quantum yield of the as-generated AuNCs was ~6.6%. The intact and the tryptic digest of AuNCs@ew were characterized by mass spectrometry. The results showed that the AuNCs@ew were mainly derived from ovalbumin, i.e., the major protein in egg white, encapsulated AuNCs. The AuNCs@ew also has the common features found in AuNCs@protein, which is sensitive to the presence of heavy metal ions such as Cu2+. The photoluminescence of the AuNCs@ew was quenched with the addition of Cu2+. Furthermore, the photoluminescence of the quenched AuNCs@ew can be restored in the presence of the molecules containing phosphate functional groups because of the strong binding affinity between Cu2+ and phosphates. We used the AuNCs@ew-Cu2+ conjugates as switch-on sensing probes for the detection of phosphate containing metabolites such as adenosine-5′-triphosphate (ATP) and pyrophosphate (PPi). The results showed that the photoluminescence of the sensing probes increased as the concentration of the phosphate-containing molecules in the sample solution increased. The limits of detection achieved using the AuNCs@ew-Cu2+ for ATP and PPi were ~19 and ~5μM, respectively. Additionally, we also demonstrated the feasibility of using the AuNCs@ew as the sensing probes for lectins such as concanavalin A (Con A) based on the molecular recognitions between the glycan ligands on the AuNCs@ew and glycan binding sites on Con A.
•Chicken egg white (ew) protein-directed syntheses of AuNCs were demonstrated.•The generated AuNCs were mainly encapsulated by chicken egg ovalbumin.•The generated AuNCs@ew is quenched in the presence of Hg(II) and Cu(II).•The AuNCs@ew-Cu(II) conjugates are useful switch-on sensing probes for ATP and PPi.•The AuNCs@ew can be used to recognize Con A based on the molecular recognition.
Columns packed with microsized titanium dioxide particles have been used effectively as precolumns for enriching phosphopeptides from complex mixtures. Nanosized titanium dioxide particles have a ...higher specific surface area and, hence, potentially higher trapping capacities toward phosphopeptides than do microsized particles. Thus, in this study, we employed TiO2-coated magnetic (Fe3O4/TiO2 core/shell) nanoparticles to selectively concentrate phosphopeptides from protein digest products. Because of their magnetic properties, the Fe3O4/TiO2 core/shell nanoparticles that are conjugated to the target peptides can be isolated readily from the sample solutions by employing a magnetic field. In this paper, we also demonstrate that the Fe3O4/TiO2 core/shell nanoparticles behave as an effective SALDI matrix: our upper detectable mass limit was ∼24 000 Da, whereas the detection limit for peptides was in the low-femtomole range. That is to say, the target analytes trapped by the Fe3O4/TiO2 nanoparticles can be identified by introducing the particles directly into the mass spectrometer for TiO2-SALDI-MS analysis without the need for any further treatment. For example, elution steps are not necessary when using this approach. In addition, the trapping selectivity of these Fe3O4/TiO2 nanoparticles toward phosphopeptides was quite good. These properties combine to result in the low detection limits. The lowest detectable concentration of phosphopeptides that we analyzed using this approach was 500 pM for a 100-μL tryptic digest solution of β-casein; this level is much lower than that which can be obtained using any other currently available method.
Triazine herbicides are commonly used in agriculture to eliminate weeds. However, they can persist in the environment. In this study, we explored a new method for detecting triazine herbicides in ...aqueous samples. We selected two triazine herbicides, namely, prometryn and ametryn, as model herbicides. To generate magnetic probes, we mixed aqueous Gd
with aqueous sodium dodecyl sulfate (SDS), which created magnetic probes made of Gd
-SDS micelles. These probes showed a trapping capacity for the model herbicides. Results indicated that the trapping capacities of our magnetic probes for ametryn and prometryn were approximately 466 and 468 nmol mg
, respectively. The dissociation constants of our probes toward ametryn and prometryn were 2.92 × 10
and 1.27 × 10
, respectively. This is the first report that the developed magnetic probes can be used to trap triazine herbicides. For detection, we used carbon fiber ionization mass spectrometry (CFI-MS), which can be used to directly detect semi-volatiles from the samples in the condensed phase. Because of the semi-volatility of triazine herbicides, the herbicides trapped by the magnetic probes can be directly analyzed by CFI-MS without any elution steps. In addition, we also demonstrated the feasibility of using our approach for detecting triazine herbicides in lake water and drinking water.
New synthetic routes were devised for total synthesis of Fe3+‐bound (ferri−) salmycin B (Sal B) (1), glycan‐based Sal analogues 2–5 and their Fe3+‐unbound (desferri−) counterparts 1′–5′ for the ...structure to activity relationship (SAR) study. The results of SAR study reveal the effective structure of 1 and its desferri‐counterpart 1′ that are responsible for the observed inhibitory activity against Staphylococcus aureus (S. aureus). Among the analogues 2–5 and 2′–5′, glucose‐based analogue 2 and its desferri‐counterpart 2′ exhibited inhibitory potency comparable to 1 and 1′. Chemical modification of 2′ for further antibacterial study enabled us to discover desferri‐Sal analogue 7′ that endowed with a simpler pharmacophore structure but significantly higher antibacterial potency against methicillin‐sensitive and resistant S. aureus than the natural product 1′ and even the clinical vancomycin. Together with a better hydrolytic stability and shorter synthetic route, the analogue 7′ represents an attractive antibiotic lead for further exploration.
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.
The extensive use of vancomycin has given rise to vancomycin-resistant bacterial strains, such as vancomycin-resistant Enterococci (VRE). We aim to explore potent medical treatments that can inhibit ...the growth of VRE.
Vancomycin-immobilized gold nanoparticles (Au@Van NPs) with polygonal shapes from one-pot reactions were generated within approximately 7 min.
The as-prepared Au NPs exhibit not only antibacterial capability but also photothermal competence. The temperature of the sample solution containing the as-prepared Au@Van NPs can be raised by approximately 15°C under irradiation by a near-infrared laser (λ = 808 nm) within 5 min.
The required amount of vancomycin on the as-prepared Au@Van NPs combined with near-infrared irradiation for inhibiting VRE is approximately 16-fold lower than that of free-form vancomycin.
Ricin produced from the castor oil plant, Ricinus communis, is a well-known toxin. The toxin comprises A and B chains. Ricin A chain can cause toxicity by inhibiting protein synthesis, and ricin B ...can bind to the galactose ligand on the cell membrane of host cells. Inhalation or ingestion of ricin may even lead to death. Therefore, rapid and convenient sensing methods for detecting ricin in suspicious samples must be developed. In this study, we generated protein encapsulated gold nanoclusters (AuNCs@ew) with bright photoluminescence by using chicken egg white proteins as starting materials to react with aqueous tetrachloroaurate. The generated nanoclusters, which were mainly composed of chicken ovalbumin-encapsulated AuNCs, can recognize ricin B because of the presence of Galβ(1→4)GlcNAc ligands on chicken ovalbumin. The generated conjugates of AuNCs@ew and ricin B were heavy and readily settled down under centrifugation (13,000rpm, 60min). Thus, bright spots resulting from the conjugates at the bottom of the sample vials were easily visualized by the naked eye under ultraviolet light illumination. The limit of detection (LOD) was ~4.6µM. The LOD was reduced to ~400nM when fluorescence spectroscopy was used as the detection tool, while the LOD can be further improved to ~7.8nM when using matrix-assisted laser desorption/ionization mass spectrometry as the detection method. We also demonstrated the feasibility of using the proposed approach to selectively detect ricin B chain in complex samples.
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•A new sensing nanoprobe for ricin is discovered.•Chicken egg white is used as the reducing agents for generating nanoprobes.•The nanoprobes have red fluorescence and can specifically target ricin B chain.•The proposed method can be used to selectively detect ricin B from complex samples.•The limit of detection of ricin was as low as ~8 nM.
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 (Fe3O4@TiO2) 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 Fe3O4@TiO2 nanoparticles. This is followed by the immobilization of IgG via amide bonding. We demonstrate that the IgGFe3O4@TiO2 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.
Bacillus
spp. are spore-forming bacteria, and some of them, including
Bacillus cereus
and
Bacillus anthracis
, are pathogens. Dipicolinic acid (DPA) has been recognized as a biomarker for ...spore-forming bacteria. Thus, developing rapid sensing methods to spot the presence of DPA in suspicious samples is significant. In this study, we employ complexes of glutathione-capped gold nanoclusters (Au@GSH NCs) with Cu
2+
as sensing probes against DPA. Au@GSH NCs possess orange-reddish fluorescence. However, their fluorescence is significantly quenched in the presence of Cu
2+
. In the presence of DPA, the fluorescence of Au@GSH NCs can be restored because DPA can easily remove Cu
2+
on the NCs through chelation based on the high formation constant (log
K
= 7.97) between Cu
2+
and DPA. Therefore, on the basis of this fact, Au@GSH NC-Cu
2+
complexes are used as turn-on fluorescence probes against DPA. Unlike most of the existing sensing methods, the developed Au@GSH-Cu
2+
-based sensing method is not affected by the presence of phosphates, which can be commonly found in real samples. The limit of detection of using the developed sensing method toward DPA can reach as low as ∼19 nM. In addition, we also demonstrate the feasibility of using the developed sensing method for detection and quantification of DPA in soil samples and
B. cereus
spore lysates.
A switched-on fluorescence sensing probe for the detection of dipicolinic acid (DPA) is demonstrated in this study.
