Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Lanthanide-doped upconversion nanocrystals (UCNs) have attracted much attention in recent years based on their promising and controllable optical ...

Application of the Intelligent High-Throughput Antimicrobial Sensitivity Testing/Phage Screening System and Lar Index of Antimicrobial Resistance

To improve the efficiency of antimicrobial susceptibility testing (AST) and phage high-throughput screening for resistant bacteria and to reduce the ...

Nanyang Technological University

Key Laboratory of Livestock and Poultry Multi-omics of MARA

Graphene oxide (GO) is a promising precursor to produce graphene-family nanomaterials for various applications. Their potential health and environmental impacts need a good understanding of their cellular interactions. Many factors may influence their biological interactions with cells, and the lateral dimension of GO sheets is one of the most relevant material properties. In this study, a model bacterium, Escherichia coli ( E. coli ), was used to evaluate the antibacterial activity of well-dispersed GO sheets, whose lateral size differs by more than 100 times. Our results show that the antibacterial activity of GO sheets toward E. coli cells is lateral size dependent. Larger GO sheets show stronger antibacterial activity than do smaller ones, and they have different time- and concentration-dependent antibacterial activities. Large GO sheets lead to most cell loss after 1 h incubation, and their concentration strongly influences antibacterial activity at relative low concentration (<10 μg/mL). In contrast, when incubating with small GO sheets up to 4 h, the inactivation rate of E. coli cells continues increasing. The increase of small GO sheet concentration also results in persistent increases in their antibacterial activity. In this study, GO sheets with different lateral sizes are all well dispersed, and their oxidation capacity toward glutathione is similar, consistent with X-ray photoelectron spectroscopy and ultraviolet-visible absorption spectroscopy results. This suggests the lateral size-dependent antibacterial activity of GO sheets is caused by neither their aggregation states, nor oxidation capacity. Atomic force microscope analysis of GO sheets and cells shows that GO sheets interact strongly with cells. Large GO sheets more easily cover cells, and cells cannot proliferate once fully covered, resulting in the cell viability loss observed in the followed colony counting test. In contrast, small GO sheets adhere to the bacterial surfaces, which cannot effectively isolate cells from environment. This study highlights the importance of tailoring the lateral dimension of GO sheets to optimize the application potential with minimal risks for environmental health and safety.

Lateral dimension-dependent antibacterial activity of graphene oxide sheets.

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition).

A protocol to link alcohols with vinyl azides has been established through fluoro- or bromo-alkoxylation of vinyl azides to provide α-alkoxy-β-haloalkyl azides. A series of primary and secondary alcohols including natural products and their derivatives such as sugars and steroids were successfully anchored with vinyl azides. The as-prepared cyanine dye linked testosterones were capable of rapid cell membrane imaging in real time.

Linking of Alcohols with Vinyl Azides.

Platinum-based chemotherapy, although it has been well proven to be effective in the battle against cancer, suffers from limited specificity, severe side effects and drug resistance. The development of new alternatives with potent anticancer effects and improved specificity is therefore urgently needed. Recently, there are some new chemotherapy reagents based on photoactive Re(i) complexes which have been reported as promising alternatives to improve specificity mainly attributed to the spatial and temporal activation process by light irradiation. However, most of them respond to short-wavelength light (e.g. UV, blue or green light), which may cause unwanted photo damage to cells. Herein, we demonstrate a system for near-infrared (NIR) light controlled activation of Re(i) complex cytotoxicity by integration of photoactivatable Re(i) complexes and lanthanide-doped upconversion nanoparticles (UCNPs). Upon NIR irradiation at 980 nm, the Re(i) complex can be locally activated by upconverted UV light emitted from UCNPs and subsequently leads to enhanced cell lethality. Cytotoxicity studies showed effective inactivation of both drug susceptible human ovarian carcinoma A2780 cells and cisplatin resistant subline A2780cis cells by our UCNP based system with NIR irradiation, and there was minimum light toxicity observed in the whole process, suggesting that such a system could provide a promising strategy to control localized activation of Re(i) complexes and therefore minimize potential side effects.

Near infrared light-mediated photoactivation of cytotoxic Re(i) complexes by using lanthanide-doped upconversion nanoparticles.

Multidrug resistance (MDR) poses a major burden to cancer treatment. As one important factor contributing to MDR, overexpression of P-glycoprotein (P-gp) results in a reduced intracellular drug accumulation. Hence, the ability to effectively block the efflux protein and to accumulate the therapeutics in cancer cells is of great significance in clinical practice. In this work, we successfully developed a smart stimulus-responsive short peptide-assembled system, termed as PD/VER nanogels, which synergistically combined the acid-activatable antitumor prodrug doxorubicin (Dox) with the P-gp inhibitor verapamil (VER) for reversing MDR. Systematic studies demonstrated that such an inhibitor-encapsulated nanogel could effectively enhance the accumulation of Dox in resistant cancer cells, thereby revealing significantly higher antitumor activity compared to free Dox molecules. This work showed that the assembly of bioactive agents with a synergistic effect into nano-drugs could provide a useful strategy to overcome cancer drug resistance.

Stimulus-Responsive Short Peptide Nanogels for Controlled Intracellular Drug Release and for Overcoming Tumor Resistance.

 is an important zoonotic pathogen that poses a serious threat to the pig industry and human health. The massive use of macrolides has led to the emergence of resistance in , and  is suspected to be a reservoir of antimicrobial resistance genes. The mechanism to macrolide resistance in  is mainly due to  and . In this study, loop-mediated isothermal amplification (LAMP) methods were developed to detect  and  genes in  through turbidimetry detection. The sensitivity and specificity of the LAMP reactions were determined. All results of LAMP and polymerase chain reaction (PCR) assay were compared to determine whether LAMP method was accurate and reliable. The results showed that all 100 nonstreptococcus clinical isolates tested negative, indicating the high specificity of LAMP assays. The detection limit of LAMP assay was 1 fg per reaction, and 10-10-fold lower than those of conventional PCR methods. Evaluation of the performance of the LAMP assay in  clinical strains revealed a good consistency between LAMP and PCR assays. In conclusion, LAMP assays are specific, sensitive, and rapid methods to detect  and  in .

Ming Hu

Division of Chemistry and Biological Chemistry,
School of Physical & Mathematical Sciences,
Division of Chemistry and Biological Chemistry, School of Physical & Mathematical Sciences

Nanyang Technological University

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Application of the Intelligent High-Throughput Antimicrobial Sensitivity Testing/Phage Screening System and Lar Index of Antimicrobial Resistance

Ming Hu

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Division of Chemistry and Biological Chemistry,School of Physical & Mathematical Sciences,Division of Chemistry and Biological Chemistry, School of Physical & Mathematical Sciences

Nanyang Technological University

Synthesis of Core-shell Lanthanide-doped Upconversion Nanocrystals for Cellular Applications

Application of the Intelligent High-Throughput Antimicrobial Sensitivity Testing/Phage Screening System and Lar Index of Antimicrobial Resistance

Division of Chemistry and Biological Chemistry,
School of Physical & Mathematical Sciences,
Division of Chemistry and Biological Chemistry, School of Physical & Mathematical Sciences