Antimicrobial activity and toxicity of gold nanoparticles: research progress, challenges and prospects

Gold nanoparticles are emerging materials that exhibit characteristics distinct from those of traditional materials and that have promising potential for application in the fields of chemistry, physics, biology and medicine. During the past decades, numerous studies on the antimicrobial activity and toxicity of gold nanoparticles have been published. With respect to antimicrobial activity, gold nanoparticles conjugated with small molecules, such as antibiotics, drugs, vaccines and antibodies, are more efficient than individual nanoparticles and molecules. Regarding the toxicity effects, results are often unclear and conflicting because of the lack of a standard experimental method; various studies have used different approaches, administration routes and doses, and similar experiments may lead to different conclusions. To provide a systematic overview of and insight in the current knowledge for researchers committed to this filed, we discuss the recent research advances related to the antimicrobial activity and toxicity of gold nanoparticles, both in vitro and in vivo, and identify major issues that require further study. SIGNIFICANCE AND IMPACT OF THE STUDY: This paper discusses the recent research progress on antimicrobial activity and toxicity of gold nanoparticles and provides general insights into the field for researchers committed to this field.

Suppression of tumor cell proliferation and migration by human umbilical cord mesenchymal stem cells: A possible role for apoptosis and Wnt signaling

Human umbilical cord-derived mesenchymal stem cells (hUCMSCs) represent potential therapeutic tools for solid tumors. However, there are numerous inconsistent results regarding the effects of hUCMSCs on tumors, and the mechanisms underlying this remain poorly understood. The present study further examined this controversial issue by analyzing the molecular mechanisms of the inhibitory effects of hUCMSCs on the proliferation and migration of the human lung cancer A549 cell line and the human hepatocellular carcinoma (HCC) BEL7402 cell line in vitro. Flow cytometric analysis demonstrated that hUCMSCs arrested tumor cells in specific phases of the cell cycle and induced the apoptosis of tumor cells by using the hUCMSC-conditioned medium (hUCMSC-CM). The hUCMSC-CM also attenuated the migratory abilities of the two tumor cell types. Furthermore, the expression of B-cell lymphoma 2 (Bcl-2), the pro-form of caspase-7 (pro-caspase-7), β-catenin and c-Myc was downregulated, while that of ephrin receptor (EphA5), a biomarker of cancer cell dormancy, was slightly increased in these two tumor cell lines treated with hUCMSC-CM. Specifically, when co-cultured via direct cell-to-cell contact, hUCMSCs were able to spontaneously fuse with any of the two types of solid tumor cells. These observations suggested that hUCMSCs may be a promising candidate for the biological therapy of lung cancer and HCC. Future studies should focus on detailed evidence for cell fusion, as well as other mechanisms proposed in the present study, by introducing additional experimental approaches and models.

γδTCR immunoglobulin constant region domain exchange in human αβTCRs improves TCR pairing without altering TCR gene-modified T cell function

The adoptive genetic transfer of T cell receptors (TCRs) has been shown to be overall feasible and offer clinical potential as a treatment for different types of cancer. However, this promising clinical approach is limited by the serious potential consequence that exogenous TCR mispairing with endogenous TCR chains may lead to the risk of self-reactivity. In the present study, domain-exchange and three-dimensional modeling strategies were used to create a set of chimeric TCR variants, which were used to exchange the partial or complete constant region of αβTCR with corresponding γδTCR domains. The expression, assembly and function of the chimeric TCR variants were examined in Jurkat T cells and peripheral mononuclear blood cells (PBMCs). Genetically-encoded chimeras were fused with a pair of fluorescent proteins (ECFP/EYFP) to monitor expression and the pairing between chimeric TCRα chains and TCRβ chains. The fluorescence energy transfer based on confocal laser scanning microscopy showed that the introduction of γδTCR constant sequences into the αβTCR did not result in a global reduction of mispairing with endogenous TCR. However, the TCR harboring the immunoglobulin-like domain of the γδTCR constant region (i.e., TCR∆IgC), showed a higher expression and preferential pairing, compared with wild-type (wt)TCR. The function analysis showed that TCR∆IgC exhibited the same levels of interferon-γ production and cytotoxic activity, compared with wtTCR. Furthermore, these modified TCR-transduced T cells retained the classic human leukocyte antigen restriction of the original TCR. The other two chimeric TCRs, had either exchange of the cp+tm+ic domain or exchange of the whole C domain (Fig. 1). Ultimately, exchange of these domains demonstrated defective function in the transduced T cells. Taken together, these findings may provide further understanding of the γδTCR constant domain with implications for the improvement of TCR gene transfer therapy.

Identification of Zygosaccharomyces mellis strains in stored honey and their stress tolerance

To screen yeast with high sugar tolerance and evaluate their stress tolerance, six yeast strains were selected from 17 stored honey samples. The species were identified through 26S rRNA sequencing. Their stress tolerance was determined via the Durham fermentation method and ethanol production ability was determined via flask fermentation. The results demonstrated that all the six strains were Zygosaccharomyces mellis. Their sugar, ethanol, and acid tolerance ranges were 500-700 g/L, 10-12% (v/v), and pH 2.5-4.5, respectively. The SO₂ tolerance was 250 mg/L. Among the six strains, 6-7431 had the best stress tolerance with sugar tolerance of 700 g/L, ethanol tolerance of 12% (v/v), and acid tolerance of pH 2.5. Furthermore, the strain of 6-7431 had the highest percentage of ethanol production at the same initial sugar content as the other strains. Therefore, the selected six yeast strains would be promising fermentation yeasts for wine-making, ethanol production, or other fermentation purposes.

Managing interoperability and complexity in health systems

In recent years, we have witnessed substantial progress in the use of clinical informatics systems to support clinicians during episodes of care, manage specialised domain knowledge, perform complex clinical data analysis and improve the management of health organisations' resources. However, the vision of fully integrated health information eco-systems, which provide relevant information and useful knowledge at the point-of-care, remains elusive. This journal Focus Theme reviews some of the enduring challenges of interoperability and complexity in clinical informatics systems. Furthermore, a range of approaches are proposed in order to address, harness and resolve some of the many remaining issues towards a greater integration of health information systems and extraction of useful or new knowledge from heterogeneous electronic data repositories.

[Homology modeling and eukaryotic expression of a modified αβ TCR harboring the immunoglobulin-like domain of γδ TCR]

Objective To design, construct and express a chimeric αβ TCR harboring the immunoglobulin-like (Ig) domain of γδ TCR in Jurkat T cells. Methods The fusion sites of TCR δIg were determined by bioinformatics analysis. Then the protein structures of TCR α δIg and TCR β δIg were predicted by homology modeling. Furthermore, the structures of TCR α δIg and TCR β δIg were compared with the wild type (wt) TCR α and TCR β respectively by combinatorial extension (CE). After that, the TCR α δIg and TCR β δIg were fused to fluorescent protein ECFP and EYFP respectively via the overlap PCR, and then the fusion genes (TCR α δIg-ECFP and TCR β δIg-EYFP) were cloned into pIRES2-EGFP vector and respectively located at the upstream and downstream of an internal ribosome entry site (IRES). The recombinant prokaryotic expression vector pIRES-TCR βδIg-EYFP/TCR αδIg-ECFP was transferred into Jurkat T cells. Finally, the expression of TCR δIg in Jurkat T cells was monitored by confocal laser scanning microscopy (CLSM). Results The variable region structure of the TCR δIg did not change and the antigen recognition active regions remained stable compared to the wtTCR. The recombinant expression plasmid was successfully constructed as confirmed by PCR identification and sequencing analysis. CLSM showed that TCR δIg was expressed and located at the plasma membrane of Jurkat T cells. Conclusion The design of TCR δIg was reasonable and the TCR δIg could be expressed on Jurkat T cell surface.

14,15-epoxyeicosatrienoic acid promotes production of brain derived neurotrophic factor from astrocytes and exerts neuroprotective effects during ischaemic injury

AIMS

14,15-Epoxyeicosatrienoic acid (14,15-EET) is abundantly expressed in brain and exerts protective effects against ischaemia. 14,15-EET is hydrolysed by soluble epoxide hydrolase (sEH). sEH^-/- mice show a higher level of 14,15-EET in the brain. Astrocytes play a pivotal role in neuronal survival under ischaemic conditions. However, it is unclear whether the neuroprotective effect of 14,15-EET is associated with astrocytes.

METHODS

A mouse model of focal cerebral ischaemia was induced by middle cerebral artery occlusion. Oxygen-glucose deprivation/reoxygenation (OGD/R) was performed on cultured murine astrocytes, neurons and a human cell line. Cell viabilities were measured by 3-(4, 5-dimethyl-2-thiazolyl)-2, 5-diphenyl-2H-tetrazolium bromide (MTT) assay. The mRNA expressions were quantified by real-time PCR. Brain derived neurotrophic factor (BDNF) concentration was measured by ELISA. Protein expressions were quantified by Western blotting. BDNF and peroxisome proliferators-activated receptor gamma (PPAR-γ) expressions were analysed by confocal microscopy.

RESULTS

Decreased infarct volumes, elevated BDNF expression and increased numbers of BDNF/GFAP Glial Fibrillary Acidic Protein double-positive cells were observed in the ischaemic penumbra of sEH^-/- mice. The decreased infarct volumes of sEH^-/- mice were diminished by intracerebroventricular injection of a blocker of BDNF receptor. 14,15-EET increases BDNF expression and cell viability of murine astrocytes and U251 cells by BDNF-TrkB Tyrosine receptor kinase-B-extracellular signal-regulated kinase 1/2 signalling during OGD/R. 14,15-EET protects neurons from OGD/R by stimulating the production of astrocyte-derived BDNF. 14,15-EET stimulates the production of astrocyte-derived BDNF through PPAR-γ/p-cAMP-response element binding protein signal pathways.

CONCLUSIONS

Our study demonstrates the importance of 14,15-EET-mediated production of astrocyte-derived BDNF for enhancing viability of astrocytes and protecting neurons from the ischaemic injury and provides insights into the mechanism by which 14,15-EET is involved in neuroprotection.

Single nucleotide polymorphism in the neuroplastin locus associates with cortical thickness and intellectual ability in adolescents

Despite the recognition that cortical thickness is heritable and correlates with intellectual ability in children and adolescents, the genes contributing to individual differences in these traits remain unknown. We conducted a large-scale association study in 1583 adolescents to identify genes affecting cortical thickness. Single-nucleotide polymorphisms (SNPs; n=54,837) within genes whose expression changed between stages of growth and differentiation of a human neural stem cell line were selected for association analyses with average cortical thickness. We identified a variant, rs7171755, associating with thinner cortex in the left hemisphere (P=1.12 × 10(-)(7)), particularly in the frontal and temporal lobes. Localized effects of this SNP on cortical thickness differently affected verbal and nonverbal intellectual abilities. The rs7171755 polymorphism acted in cis to affect expression in the human brain of the synaptic cell adhesion glycoprotein-encoding gene NPTN. We also found that cortical thickness and NPTN expression were on average higher in the right hemisphere, suggesting that asymmetric NPTN expression may render the left hemisphere more sensitive to the effects of NPTN mutations, accounting for the lateralized effect of rs7171755 found in our study. Altogether, our findings support a potential role for regional synaptic dysfunctions in forms of intellectual deficits.

Differences in TCR-Vβ repertoire and effector phenotype between tumor infiltrating lymphocytes and peripheral blood lymphocytes increase with age

Tumor infiltrating lymphocytes (TIL) reflect the host's anti-tumor immune response, and can be a valuable predictor of prognosis. However, many properties of TIL are not fully understood. In the present study, TCR-Vβ repertoires of cancer patients were primarily analyzed by flow cytometry. Abnormally expressed TCR-Vβ subfamilies were generally found in both TIL and peripheral blood lymphocytes (PBL) of each patient. Of note, increased patient age was associated with increasingly biased TCR-Vβ repertoire in TIL but not in PBL, and the dispersion degree of the differences of TCR-Vβ subfamilies between TIL and PBL correlated positively with age (P = 0.007). Utilizing immunoscope analysis, we identified the age-related reduction in TCR-Vβ diversity, but polyclonal pattern was predominant in significantly expanded TCR-Vβ subfamilies. In addition, we found that older patients possessed a decreased ratio of CD8+CD62L+ non-effector cells in TIL compared to PBL, implying age-related increase of CD8+CD62L- effector cells in TIL. The colocalization analysis of CD8 and CD3, however, suggested the suppressed activity of these effector cells in tumor microenvironment. These findings further elucidate the properties of TIL, showing an increasing difference between TIL and PBL with age, which may provide insight for the development of effective immunotherapies for cancer patients of different ages.

A rapid one-step immunochromatographic test strip for rabies detection using canine serum samples

We developed an immunochromatographic test strip using colloidal gold-coated staphylococcal protein A (SPA) for the detection of rabies antibody in canine serum samples. The recombinantly expressed rabies virus phosphoprotein (RV-P) and the anti-staphylococcal protein A (anti-SPA) polyclonal antibody were coated on the test (T) and control (C) lines on a nitrocellulose membrane, respectively. This layout is designed such that the polyclonal antibody in canine serum is captured by the colloidal gold-SPA conjugates, before the rabies antibody complex is specifically selected by the RV-P deposited on the T line, forming a 'sandwich' pattern. Unbound excess colloidal SPA then proceeds to the control line where SPA specifically interacts with the anti-SPA antibody, producing a red precipitation at the C line, indicating the validity of the strip. We tested 165 canine serum samples with the strips, and the results were compared with those obtained using ELISA. The specificity and sensitivity of ICTS were found to be 93·1 and 92·2%, respectively. As a rapid technique, not demanding expensive instrumentation, the strip offers potential in disease monitoring, especially in rabies-endemic developing countries.

SIGNIFICANCE AND IMPACT OF THE STUDY

Simple and cheap techniques to detect rabies virus or monitor immunity against it are central in maintaining epidemiological control over the disease, particularly in endemic developing countries. While many techniques meet this requirement, they are confined to this usage as they are time-consuming and demand expensive instrumentation. Our immunochromatographic test strip can detect rabies antibody with high specificity and sensitivity; the output can be measured with naked eye. It allows safe and quick detection that will be of value in the surveillance of the immunization status of potential targets in rabies-endemic regions and will aid disease control.