Correction to "Luminescent Gold Nanocluster-Decorated Polymeric Hybrid Particles with Assembly-Induced Emission".
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ABSTRACT:
SUBMITTER: Hembury M
PROVIDER: S-EPMC6343942 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Ultrasmall gold atom clusters (<2 nm in diameter) or gold nanoclusters exhibit emergent photonic properties (near-infrared absorption and emission) compared to larger plasmonic gold particles because of the significant quantization of their conduction band. Although single gold nanocluster properties and applications are being increasingly investigated, little is still known about their behavior and properties when assembled into suprastructures, and even fewer studies are investigating their use for biomedical applications. Here, a simple synthetic pathway combines gold nanoclusters with thermosensitive diblock copolymers of poly(ethylene glycol) (PEG) and poly( N-isopropylacrylamide) (PNIPAm) to form a new class of gold-polymer, micelle-forming, hybrid nanoparticle. The nanohybrids' design is uniquely centered on enabling the temperature-dependent self-assembly of gold nanoclusters into the hydrophobic cores of micelles. This nonbulk assembly not only preserves but also enhances the attractive near-infrared photonics of the gold nanoclusters by significantly increasing their native fluorescent signal. In parallel to the fundamental insights into gold nanocluster ordering and assembly, the gold-polymer nanohybrids also demonstrated great potential as fluorescent live-imaging probes in vitro. This innovative material design based on the temperature-dependent, self-assembly of gold nanoclusters within a polymeric micelle's core shows great promise toward bioassays, nanosensors, and nanomedicine.
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Project description:A new approach to sensing and imaging hydrogen peroxide (H2O2) was developed using microcapsule-based dual-emission ratiometric luminescent biosensors. Bovine serum albumin-capped gold nanoclusters (BSA-AuNCs) sensitive to H2O2 were coencapsulated with insensitive FluoSpheres (FSs) within polymeric capsules fabricated via the layer-by-layer method. Under single-wavelength excitation, the microcapsule-based biosensors exhibited emission bands at ∼516 and ∼682 nm resulting from the FSs and BSA-AuNCs, respectively. The polyelectrolyte multilayers lining the microcapsules were effective in protecting BSA-AuNCs from the degradation catalyzed by proteases (chymotrypsin, trypsin, papain, and proteinase K) and subsequent luminescent quenching, overcoming a key limitation of prior BSA-AuNC-based sensing systems. The luminescent response of the sensors was also found to be independent of local changes in pH (5-9). Quenching of the AuNCs in the presence of H2O2 enabled the spectroscopic quantification and imaging of changes in H2O2 concentration from 0 to 1 mM. The microcapsule sensors were easily phagocytized by murine macrophage cells (RAW 264.7), were effective as intracellular H2O2 imaging probes, and were successfully used to detect local release of H2O2 in response to an external chemical stimulus.
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Project description:Size-independent emission has been widely observed for ultrasmall thiolated gold nanoparticles (AuNPs) but our understanding of the photoluminescence mechanisms of noble metals on the nanoscale has remained limited. Herein, we report how the emission wavelength of a AuNP and the local binding geometry of a thiolate ligand (glutathione) on the AuNP are correlated, as these AuNPs emit at different wavelengths in spite of their identical size (ca. 2.5 nm). By using circular dichroism, X-ray absorption, and fluorescence spectroscopy, we found that a high Au-S coordination number (CN) and a high surface coverage resulted in strong Au(I) -ligand charge transfer, a chiral conformation, and 600 nm emission, whereas a low Au-S CN and a low surface coverage led to weak charge transfer, an achiral conformation, and 810 nm emission. These two size-independent emissions can be integrated into one single 2.5 nm AuNP by fine-tuning of the surface coverage; a ratiometric pH response was then observed owing to strong energy transfer between two emission centers, opening up new possibilities for the design of ultrasmall ratiometric pH nanoindicators.
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Project description:Endo/lysosomal escape and subsequent nuclear translocation are recognized as the two major challenges for efficient gene transfection. Herein, nuclear localization signal (NLS) peptide sequences and oligomeric lysine sequences were crosslinked via disulfide bonds to obtain glutathione (GSH) reducible polypeptide (pNLS). The pNLS could condense DNA into compact positive-charged complexes with redox sensitivity, and then gold nanoclusters (AuNC) were further decorated to the surface via electrostatic interactions obtaining versatile pNLS/DNA/AuNC complexes. The AuNC could generate reactive oxygen species (ROS) under NIR-irradiation and accelerate the endo/lysosomal escape of the complexes, and then the pNLS sequence degraded by GSH in cytoplasm would release the DNA and facilitate the subsequent nuclear translocation for enhanced gene transfection.
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Project description:Bacteriophage Qbeta coat protein forms uniform virus-like particles when expressed recombinantly in a variety of organisms. We have inserted the IgG-binding Z domain at the carboxy terminus of the coat protein and coexpressed this chimeric subunit with native coat protein to create hybrid, IgG-binding virus-like particles. Extracellular osmolytes were found to have an effect on the efficiency of incorporation of fusion proteins into VLPs in Escherichia coli when a carbenicillin, but not a kanamycin, selection marker was used. The addition of sucrose to the growth medium decreased the incorporation efficiency; the osmoprotectant glycine betaine eliminated this effect. The decrease in efficiency was not observed when carbenicillin was omitted from the final expression culture. The addition of sodium chloride instead of sucrose gave rise to particles with a larger number of fusion proteins than the standard conditions. These results illustrate that cellular conditions should be taken into account even in apparently simple systems when natural or engineered protein nanoparticles are made.
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Project description:Graphene quantum dots (GQDs) possess excellent optical and electrical properties that can be used in a wide variety of application. Synthesis of hybrid nanoparticles with GQDs have been known to improve the properties further. Therefore, in this method, graphene quantum dots -gold (GQD-Au) hybrid nanoparticles were synthesized using GQDs which reduces HAuCl4.3H2O to Au nanoparticles on its surface at room temperature. The GQDs with self-passivated layers were synthesized by microwave assisted hydrothermal method using glucose as a single precursor. The synthesis process does not involve the use of harmful chemicals. The whole synthesis process of GQD and GQD-Au hybrid nanoparticles takes only five minutes. The synthesized GQDs have been extracted using citrate in order to increase the stability of the hybrid nanoparticles for up to four weeks. The size of the synthesized GQD-Au hybrid nanoparticles is in the range of 5-100 nm and were found to be luminescent under UV-A illumination. The merit of the following method over other synthesis techniques include its rapidity, ease of preparation, and no requirement of elaborate synthesis procedures and/or harmful chemicals. The GQD-Au hybrid nanoparticles can be used in several applications such as luminescent coatings for glass and windowpanes for automobiles, etc. The reducing property of GQDs can further be utilized for the reduction of various metal salts (AgNO3) and organic dyes (methylene blue and methyl orange). . It presents a method/protocol-development of the luminescent GQD-Au hybrid particles of size ~ 5-100 nm. . The GQD-Au hybrid particles find potential applications in luminescent coating applications.
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Project description:Near infrared (NIR) fluorophores like Pt-porphyrin along with analyte specific enzymes require co-encapsulation in biocompatible and biodegradable carriers in order to be transformed into implantable biosensors for efficient and continuous monitoring of analytes in patients. The main objective of this research is to develop natural, biodegradable, biocompatible and a novel co-encapsulated system of Pt-porphyrin encapsulated polymeric nanoparticle and nano-micro hybrid carriers. A sequential emulsification-solvent evaporation and an air driven atomization technique was used for developing above matrices and testing them for fluorescence based oxygen and glucose biosensing. The results indicate Pt-porphyrin can be efficiently encapsulated in Poly-lactic acid (PLA) nanoparticles and PLA-alginate nano-micro particles with sizes ~450 nm and 10 µm, respectively. Biosensing studies have showed a linear fluorescent response in oxygen concentrations ranging from of 0-6 mM (R2 = 0.992). The Oxygen sensitivity was transformed into a linear response of glucose catalytic reaction in the range of 0-10 mM (R2 = 0.968) with a response time of 4 minutes and a stability over 15 days. We believe that the investigated NIR fluorophores like Pt-Porphyrin based nano/nano-micro hybrid carrier systems are novel means of developing biocompatible biodegradable carriers for developing implantable glucose biosensors which can efficiently manage glucose levels in diabetes.
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Project description:A systematic investigation into the relationship between the solid-state luminescence and the intermolecular Au???Au interactions in a series of pyrazolate-based gold(I) trimers; tris(?2 -pyrazolato-N,N')-tri-gold(I) (1), tris(?2 -3,4,5- trimethylpyrazolato-N,N')-tri-gold(I) (2), tris(?2 -3-methyl-5-phenylpyrazolato-N,N')-tri-gold(I) (3) and tris(?2 -3,5-diphenylpyrazolato-N,N')-tri-gold(I) (4) has been carried out using variable temperature and high pressure X-ray crystallography, solid-state emission spectroscopy, Raman spectroscopy and computational techniques. Single-crystal X-ray studies show that there is a significant reduction in the intertrimer Au???Au distances both with decreasing temperature and increasing pressure. In the four complexes, the reduction in temperature from 293 to 100?K is accompanied by a reduction in the shortest intermolecular Au???Au contacts of between 0.04 and 0.08?Å. The solid-state luminescent emission spectra of 1 and 2 display a red shift with decreasing temperature or increasing pressure. Compound 3 does not emit under ambient conditions but displays increasingly red-shifted luminescence upon cooling or compression. Compound 4 remains emissionless, consistent with the absence of intermolecular Au???Au interactions. The largest pressure induced shift in emission is observed in 2 with a red shift of approximately 630?cm(-1) per GPa between ambient and 3.80?GPa. The shifts in all the complexes can be correlated with changes in Au???Au distance observed by diffraction.
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