Silica nanoparticles for micro-particle imaging velocimetry: fluorosurfactant improves nanoparticle stability and brightness of immobilized iridium(III) complexes

Chelating silica nanoparticles for efficient antibiotic delivery and particle imaging in Gram-negative bacteria

The inefficacy of antibiotics against Gram-negative bacteria is a major challenge for treatment of many clinically important bacterial infections. The complex structure of the double cell membrane of Gram-negative bacteria makes it inaccessible to many key antibiotics such as vancomycin and also presents a major challenge for drug development. In this study we design of a novel hybrid silica nanoparticle system bearing membrane targeting groups with the antibiotic encapsulated together with a ruthenium luminescent tracking agent, for optical detection of the nanoparticle delivery in the bacterial cell. The hybrid system shows delivery of vancomycin and efficacy against a library of Gram negative bacterial species. Evidence of penetration of nanoparticles in bacteria cells is achieved via luminescence of the ruthenium signal. Our studies show that nanoparticles modified with aminopolycarboxylate chelating groups are an effective delivery system in bacterial growth inhibition in species whereas the molecular antibiotic is ineffective. This design provides a new platform for delivery of antibiotics that cannot alone penetrate the bacterial membrane.

Synthesis, characterization and biological evaluation of two cyclometalated iridium(III) complexes containing a glutathione S-transferase inhibitor

The cyclometalated iridium(III) compounds have been intensively studied for health-related applications due to their outstanding luminescent properties and multiple anticancer modes of action. Herein, two iridium(III) compounds Ir-1 and Ir-3 containing glutathione S-transferase inhibitor (GSTi) were developed and studied together with two unfunctionalized compounds Ir-2 and Ir-4 as a comparison. Biological study indicated that GSTi-bearing complexes Ir-1 and Ir-3 exert a synergistic effect on the inhibition of cancer cells. The photophysical properties of Ir-1 ∼ Ir-4 were investigated by UV/vis absorption and fluorescence spectroscopy and rationalized with TD-DFT calculations. As expected, GSTi-bearing complexes Ir-1 and Ir-3 exhibited considerable cytotoxicity against both A549 and cisplatin-resistant A549/cis cancer cells, much higher than the unfunctionalized iridium compounds Ir-2 and Ir-4. Further study indicated that Ir-1 and Ir-3 mainly localize in the mitochondria of tumor cells, and exert their cytotoxicity via generating ROS and inhibiting GST activity. The flow cytometry investigations demonstrated that Ir-1 and Ir-3 can arrest the cell cycle in S phase and induce the cell death through apoptosis process. Overall, the complexation of GST inhibitors with cyclometalated iridium(III) agents provides an effective way for potentiating the cytotoxicity of iridium(III) anticancer agents and resensitizing the efficacy against cisplatin resistant cancer cells.

Electrochemiluminescence and Photoluminescence of Carbon Quantum Dots Controlled by Aggregation-Induced Emission, Aggregation-Caused Quenching, and Interfacial Reactions

Carbon quantum dots (CQDs) show promise in optoelectronics as a light emitter due to simple synthesis, biocompatibility and strong tunable light emissions. However, CQDs commonly suffer from aggregation caused quenching (ACQ), inhibiting the full potential of these light emitters. Studies into different ideal light emitters have shown enhancements when converting common ACQ effects to aggregation induced emission (AIE) effects. We report CQD synthesis using citric acid and high/low thiourea concentrations, or sample 2/1. These two CQDs exhibited AIE and ACQ PL effects, respectively. CQD characterizations and photoluminescence interrogations of CQD films and solutions revealed that these unique emission mechanisms likely arose from different S incorporations into the CQDs. Furthermore, it was discovered that sample 2 emitted electrochemiluminescence (ECL) more intensely than sample 1 in a homogenous solution with S₂O₈^2- as a coreactant, due to aggregation and interactions of CQD species in solution. Very interestingly, sample 1's CQD film|S₂O₈^2- system achieved an ECL efficiency of 26% and emitted roughly 26 times more efficiently than sample 2 in the same conditions. Predominant interfacial reactions and surface state emission produced intense white light with a correlated color temperature of 2000 K. Spooling ECL spectroscopy was utilized to investigate emission mechanisms. Sample 2's CQD film|TPrA system had four times higher ECL intensity than that of sample 1, most likely due to π-cation interactions leading to a strong CQD^•+ stability, thereby, enhancing ECL. It is anticipated that ECL enhancement of CQD films or solutions by means of AIE will lead to wide CQD optoelectronic applications.

Solution processing of two-dimensional black phosphorus

Phosphorene, or two-dimensional (2D) black phosphorus (BP) was the first synthetic 2D elemental allotrope beyond graphene to be isolated and studied. It is useful due to its high p-type carrier mobility and direct band gap that is tunable in the range ca. 0.3-2 eV thus bridging the energy gap between graphene and transition metal dichalcogenides such as molybdenum disulfide. Beyond the 'Scotch-Tape' method that was used to isolate the first samples of 2D BP for prototype studies, a range of potentially scalable solution processing techniques emerged later that can produce electronics grade material. This feature article focuses on such solution-process routes to 2D BP and highlights challenges in processing the material, mainly caused by its susceptibility to oxidation, as well as illuminating new avenues and opportunities in the area.

Tailoring iridium luminescence and gold nanoparticle size for imaging of microvascular blood flow

AIM

Imaging of blood flow in narrow channels and close to vessel walls is important in cardiovascular research for understanding pathogenesis. Our aim was to provide novel nanoprobes with visible emission and long lifetimes as trackers of flow.

MATERIALS & METHODS

Gold nanoparticles coated with an iridium complex were prepared. Luminescence imaging was used to monitor their flows in different hematocrit blood and in murine tissues.

RESULTS

The velocities are independent of hematocrit level and the nanoparticles entering blood circulation can be clearly detected in vessels in lungs, mesentery and the skeletal muscle.

CONCLUSION

The work introduces for the first time iridium-based yellow-green luminescence with nanoparticle size of 100 nm for visualizing and monitoring flows with much higher resolution than conventional alternatives.

On the stability of surfactant-stabilised few-layer black phosphorus in aqueous media

The stability of few-layer black phosphorus has been studied in aqueous media using a range of spectroscopic techniques. The material is meta-stable, degrading over time mainly to phosphoric acids.

The deposition and imaging of silica sub-micron particles in dentine

OBJECTIVES

Sub-micron particles may assist in the delivery of compounds into dentine tubules. The surface interactions of the particles with dentine may prevent them from entering the tubules. The aim of this study is to investigate whether silica particles, treated with surfactants improves dentine tubules occlusion using both artificial and human tooth models

METHODS

Spherical silica particles (size 130-810nm) bearing an encapsulated ruthenium luminescent complex were coated with the following surfactants: Zonyl(®) FSA, Triton(®) X-100 and Tween20(®). The particles were prepared as 0.004% w/v and 0.04% w/v solutions with deionized water and were applied to the surface of; (1) in vitro model of PET ThinCert™ cell culture inserts; (2) 0.1mm thick sections of human molar teeth.

RESULTS

Scanning electron and confocal fluorescence microscopy images show that particles without any coating and with TritonX-100 coating had the highest aggregation. Particles with Tween-20 are less aggregated on the surface and show inclusion in the tubules. Particles coated with fluorosurfactant Zonyl show a preference for aggregation at the tubule. With the ThinCert™ membranes high aggregation within the artificial tubules was increased by particle concentration.

CONCLUSIONS

The use of silica sub-micron particles on hard dental tissues is dependent on the modification of the surface chemistry of both the particle and the dentine and the employment of the fluorοsurfactant may improve tubule occlusion. The use of ThinCerts™ membrane is useful in vitro model to mimic dentinal tubules and observe the ability of particles to occlude small channels.

CLINICAL SIGNIFICANCE

The use of silica sub-micron particles on hard dentine tissues is dependent on the modification of the surface coating of the particles. This may influence how particles are incorporated in potential delivery vehicles applied to the dentine surface with the employment of a fluorosurfactant showing promise.

Genotoxicity of mesoporous silica nanoparticles in human embryonic kidney 293 cells

Mesoporous silica nanoparticles (MSNs) have been widely evaluated for their potential use as carriers for cancer diagnosis and therapy. Understanding the toxicity of MSNs is crucial to their biomedical applications. Although several groups have reported the cytotoxicity of MSNs, the genotoxicity (inducing genetic aberrations) of MSNs in normal human cells has not been extensively investigated. Gene amplification and mutation may initiate and promote carcinogenesis, and changes in mRNA expression can affect normal human physical functions. In this study, human embryonic kidney 293 (HEK293) cells were treated overnight with MSNs at a concentration of 120 µg/mL. The cells were assayed with fluorescent in situ hybridization to check for chromosome changes and gene amplification. Mutations in the epidermal growth factor receptor 1 (EGFR1) and KRAS genes were checked with DNA sequencing. The effects of MSNs on mRNA expression were investigated with an Agilent human mRNA microarray. No chromosomal alterations or gene mutations in EGFR or KRAS were observed in the control HEK293 cells or HEK293 cells exposed to MSNs. The microarray analysis showed that MSNs significantly altered gene expression. The expression of 579 genes was upregulated and that of 1263 genes was downregulated in HEK293 cells treated with MSNs compared with the control HEK293 cells. Our findings suggest that exposure to MSNs is genotoxic to normal human cells, leading to changes in the expression of some genes. This genotoxicity may cause cellular dysfunction and certain benign diseases. We have not shown that MSN exposure induces serious genotoxicity involving carcinogenesis.