Review on Zinc Oxide Nanoparticles: Antibacterial Activity and Toxicity Mechanism

Antibacterial activity of zinc oxide nanoparticles(Zn O-NPs) has received significant interest worldwide particularly by the implementation of nanotechnology to synthesize particles in the nanometer region. Many microorganisms exist in the range from hundreds of nanometers to tens of micrometers. Zn O-NPs exhibit attractive antibacterial properties due to increased specific surface area as the reduced particle size leading to enhanced particle surface reactivity. Zn O is a bio-safe material that possesses photo-oxidizing and photocatalysis impacts on chemical and biological species. This review covered Zn O-NPs antibacterial activity including testing methods, impact of UV illumination, Zn O particle properties(size, concentration, morphology, and defects), particle surface modification, and minimum inhibitory concentration. Particular emphasize was given to bactericidal and bacteriostatic mechanisms with focus on generation of reactive oxygen species(ROS) including hydrogen peroxide(H2O2), OH-(hydroxyl radicals), and O2-2(peroxide). ROS has been a major factor for several mechanisms including cell wall damage due to Zn O-localized interaction, enhanced membrane permeability, internalization of NPs due to loss of proton motive force and uptake of toxic dissolved zinc ions.These have led to mitochondria weakness, intracellular outflow, and release in gene expression of oxidative stress which caused eventual cell growth inhibition and cell death. In some cases, enhanced antibacterial activity can be attributed to surface defects on Zn O abrasive surface texture. One functional application of the Zn O antibacterial bioactivity was discussed in food packaging industry where Zn O-NPs are used as an antibacterial agent toward foodborne diseases. Proper incorporation of Zn O-NPs into packaging materials can cause interaction with foodborne pathogens, thereby releasing NPs onto food surface where they come in contact with bad bacteria and cause the bacterial death and/or inhibition.

Carbon nanotubes:A review on risks assessment,mechanism of toxicity and future directives to prevent health implication

Carbon nanotubes(CNTs)have tremendous applications in almost every walk of life;however,their harmful impacts on humans and the environment are not well addressed.CNTs have been used in various applications ranging from medical science to different engineering branches,to ease human life.Generally,the toxicological profile of CNTs under laboratory conditions cannot be assessed primarily in medical science due to the inconsistent availability of cytotoxic study data.CNT toxicity has been affected by many physicochemical properties(e.g.,size,type of functionalization),concentration,the extent of exposure,mode of exposure,and even the solvents/medium used to dissolve/disperse CNTs for their application.These inconsistencies arise due to the variation in synthesis methods as well as the mode of their human exposure.Besides their unlimited use in various fields,most of CNT toxicity aspects and mechanisms remain uncertain.Additionally,in-depth knowledge of CNTs toxicity is scarce,and the available literature shows dissimilarities in experimental data and exposure studies.To understand the toxicological issues,it is the need of the hour to provide insight into the published data,post-exposure studies,and various factors that may damage the cells due to CNTs toxicity.This review article analyses the hazardous potential through toxicological implications and summarizes the detailed mechanism(s)of CNTs studied on the different model organisms,including human cell lines.In this review article,we hypothesized that thorough knowledge of various aspects,as mentioned above,helps us design and develop possible strategies to reduce the toxicity of nanomaterial to make them safer and secure for humanity’s betterment.

Advances in toxicological studies of Radix Phytolaccae

Radix Phytolaccae is the dried root of Phytolacca acinosa Roxb or P.ameri-cana L,which is commonly used as a traditional Chinese medicine to treat diseases like cirrhotic ascites,hepatitis B,nephrotic syndrome,psoriasis,etc.However,there is no exact basis for its clinical application safety.In this paper,the toxic effects and mechanism of Saponin A(EsA),the main component of Radix Phytolaccae,were summarized by searching the results and reports of toxicology related to the plant from 1991 to 2023 on CNKI and pubmed,aiming to provide reference for the toxicological research and future research direction of Radix Phytolaccae,so that Radix Phytolaccae can be safely and effectively used in clinical practice.

Exosomes Derived from Hydroquinone-transformed Human Bronchial Epithelial Cells Inhibited Recipient Cell Apoptosis by transferring miR-221

Objective Although benzene is a confirmed environmental carcinogen,the mechanism of its carcinogenicity remains largely unclear.The suggested oncogene,miR-221,is elevated and plays important roles in various tumors,but its role in benzene-induced carcinogenesis remains unknown.Methods In the present study,we constructed hydroquinone(HQ,a representative metabolite of benzene with biological activity)-transformed malignant cell line(16 HBE-t)and analyzed the level of miR-221 in it with qRT-PCR.Exosomes from 16 HBE-t cells incubated with or without an miR-221 inhibitor were isolated by ultracentrifugation,characterized by transmission electron microscopy and laser scanning confocal microscope,and then transfected into 16 HBE cells.The effects of exosomal miR-221 on apoptosis induced by HQ in recipient cells were determined using flow cytometry.Results The amount of miR-221 in 16 HBE-t was significantly increased compared with controls.When recipient cells ingested exosomes derived from 16 HBE-t,miR-221 was increased,and apoptosis induced by HQ was inhibited.Blocking miR-221 in 16 HBE-t using an inhibitor did not significantly alter miR-221 or apoptosis in recipient cells.Conclusion Exosomal miR-221 secreted by 16 HBE-t inhibits apoptosis induced by HQ in normal recipient cells.

Discussions on Toxic Traditional Chinese Medicine and New Perspectives

Along with the increase in the consumption of traditional Chinese medicine(TCM), the safety of TCM has dramatically attracted the attention and concern of the public. Here, we review previous studies, which focused mainly on the toxicity of toxic TCM and the interpretations for combination, to elaborate on advances and important issues existing in the safety evaluation of TCM, aiming to provide scientific advice for the clinical use. Moreover, we emphasize the importance of a safe evaluation system for TCM based on the material basis for toxicity, which integrates new toxicity testing strategy and is launched under the guidance of TCM theories in future researches.

Pyrrolizidine alkaloids:An update on their metabolism and hepatotoxicity mechanism

Pyrrolizidine alkaloids(PAs)are among the most hepatotoxic natural compounds that are widely distributed throughout the world.Most PAs are metabolically activated to trigger toxicity.Exposure to herbal medicine containing PAs and food supplements contaminated by PAs is considered to be one of the two main causes of hepatic sinusoidal obstruction syndrome(HSOS),which is a rare hepatic vascular disease with a high mortality rate.PAs-induced HSOS cases have been reported worldwide.However,there is no clinically effective therapy for PAs-induced HSOS,which is partially because the toxic mechanism is not fully understood.This review focuses on updating the information on the metabolism and the molecular mechanisms of PAs hepatotoxicity,including oxidative stress,apoptosis,and dysfunction of bile acid metabolism,and their interactions.

A Comparative Toxicity Study of TiO2 Nanoparticles in Suspension and Adherent Culture Under the Dark Condition

The present study focused on the different acute toxicity of TiO2 nanoparticles（TiO2 NPs） towards the bacteria in suspension culture and adherent culture under the dark conditions. The study investigated the bacteria toxicity with TiO2 NPs at different concentrations（1-2000 mg/L）, sizes（10 nm, 35 nm） and specific surface areas in unit volume solution（0-224 m^2/L） characterized by the cell viability, extracellular polymeric substances（EPS） release and biofilm formation. The bacteria in adherent culture was found to be more resistant against the toxicity of TiO2 NPs compared to that in suspension culture. An NP dose and surface area dependent（rather than the size） bacterial viability was observed in suspension culture, specifically the surface area positively correlated with the toxicity of TiO2 NPs. The size of TiO2 NPs, however, played a more critical role in toxicity of TiO2 NPs in adherent culture. Therefore, the surface area dependent toxicity of TiO2 NPs is a comprehensive parameter describing the dose and size dependent toxicity of TiO2 NPs. The electron microscopic（SEM, TEM, EDX） observations suggested the EPS release and biofilm formation, during aggregation of TiO2 NPs on the bacteria after 12 h cultivation in adherent culture under the dark condition. A possible toxic mechanism could be that ＂effective surface areas＂ that directly contact with the bacterial membrane greatly contributed to the toxicity of TiO2 NPs in both suspension culture and adherent culture. Therefore, as for the possible resistance mechanism, EPS secretion and subsequent biofilm formation may protect the bacteria against the toxicity of TiO2 NPs.

The chlorination transformation characteristics of benzophenone-4 in the presence of iodide ions

Benzophenone-type UV filters are a group of compounds widely used to protect human skin from damage of UV irradiation. Benzophenone-4（BP-4） was targeted to explore its transformation behaviors during chlorination disinfection treatment in the presence of iodide ions. With the help of ultra performance liquid phase chromatograph and high-resolution quadrupole time-of-flight mass spectrometer, totally fifteen halogenated products were identified, and five out of them were iodinated products. The transformation mechanisms of BP-4 involved electrophilic substitution generating mono-or di-halogenated products,which would be oxidized into esters and further hydrolyzed into phenolic derivatives. The desulfonation and decarboxylation were observed in chlorination system either. Obeying the transformation pathways, five iodinated products formed. The p H conditions of chlorination system determined the reaction types of transformation and corresponding species of products. The more important was that, the acute toxicity had significant increase after chlorination treatment on BP-4, especially in the presence of iodide ions. When the chlorination treatment was performed on ambient water spiked with BP-4 and iodide ions,iodinated by-products could be detected.

Proteomic analysis of human umbilical vein endothelial cells exposed to PM_(2.5)

Exposure to fine ambient particulate matter(PM_(2.5)) is known to be associated with cardiovascular disease. To uncover the molecular mechanisms involved in cardiovascular toxicity of PM_(2.5), we investigated alterations in the protein profile of human umbilical vein endothelial cells(HUVECs) treated with PM_(2.5) using two-dimensional electrophoresis in conjunction with mass spectrometry(MS). A total of 31 protein spots were selected as differentially expressed proteins and identified by matrix-assisted laser desorption/ionization-time of flight(MALDI-TOF) MS. The results demonstrated that DNA damage and cell apoptosis are important factors contributing to PM_(2.5)-mediated toxicity in HUVECs. It is further proposed that PM_(2.5) can inhibit superoxide dismutase(SOD) activity and increase reactive oxygen species(ROS) and malonaldehyde(MDA) production in a concentration-dependent manner. Induction of apoptosis and DNA damage through oxidative stress pathways may be one of the key toxicological events occurring in HUVECs under PM_(2.5) stress. These results indicated that the toxic mechanisms of PM_(2.5) on cardiovascular disease are related to endothelial dysfunction.