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Groundwater contamination remains a global threat due to its toxic effects to humans and the environment. The remediation of contaminated groundwater sites can be costly, thus, identifying the priority areas of concern is important to reduce money spent on resources. In this study, we aimed to identify and rank the priority groundwater sites in a contaminated petrochemical district by combining alternative, non-animal approaches - chemical analysis, cell-based high throughput screening (HTS), and Toxicological Priority Index (ToxPi) computational toxicology tool. Groundwater samples collected from ten different sites in a contaminated district showed pollutant levels below the detection limit, however, hepatotoxic bioactivity was demonstrated in human hepatoma HepaRG cells. Integrating the pollutants information (i.e., pollutant characteristics and concentration data) with the bioactivity data of the groundwater samples, an evidence-based ranking of the groundwater sites for future remediation was established using ToxPi analysis. The currently presented combinatorial approach of screening groundwater sites for remediation purposes can further be refined by including relevant parameters, which can boost the utility of this approach for groundwater screening and future remediation.

Silica nanoparticles (SiO2 NPs) are engineered nanomaterials (ENMs) that have a wide range of application. Increased use in manufacturing has led to concerns about their environmental impact and possible adverse health effects. We conducted a comparative toxicity assessment of bare SiO2-NPs and amine-functionalized SiO2 NPs (NH2-SiO2 NPs) utilizing the Caenorhabditis elegans (C. elegans) in vivo model. L1 nematodes were exposed to exposure concentrations of 0.25, 0.5, 2.5, and 5 mg mL–1 until the worms reached the L4 stage. The chronic lethality and lifespan assays revealed a significant decrease in survival rate and lifespan at 2.5 and 5 mg mL–1 for nematodes exposed to bare SiO2 NPs (89% and 88%; 22 days, p < 0.05 and 14 days, p < 0.05) and at 5 mg mL–1 for the NH2-SiO2 NPs-exposed group (86%; 20 days, p < 0.001). Exposure to all SiO2 NP concentrations reduced progeny production to 79–60% while exposure to 2.5 and 5 mg mL–1 of NH2-SiO2 NPs significantly reduced the brood size to 64–63%. Neurobehavioral toxicity was also observed in the SiO2 NP-exposed worms, which displayed significantly decreased head thrashing for up to 92–71% and in the NH2-SiO2 NPs-exposed worms which showed significantly reduced head thrashing movement for up to 91–85% at concentrations of 0.5-5 mg mL–1. Body bending movements were also significantly reduced at 0.5–5 mg mL–1 SiO2 NPs (71–34%) and 2.5–5 mg mL–1 NH2-SiO2 NPs (94–66%). Significant shortening of body size was also observed in nematodes exposed to 0.5–5 mg mL–1 for both SiO2 NPs (93–81%) and NH2-SiO2 NPs (94–88%). Overall, bare SiO2 NPs were observed to be more toxic due to the negatively charged surface OH groups, which may have disrupted protein homeostasis, resulting in the observed toxicities. We suggest that functionality is an important indicator in nanosafety evaluations.

Determining the hotspots and deposition efficiencies (DEs) for aerosols in human airways is important for both research and medical purposes. The complexity of the human airways and the breathing process limit the application of in vitro measurements to only two consecutive branches of the human airway. Herein, in-depth information on in vitro experiments and state-of-the-art review on various computational fluid dynamics (CFD) applications and finite element methods on airflow and aerosol motion in both healthy and obstructed human airways are provided. A brief introduction of the application of one-dimensional and two-dimensional mathematical models to investigate airflow and particle motion in the lungs are further discussed. As evident in this review, aerosol deposition in the upper and central human airway regions has been extensively studied under different inhalation statuses and conditions such as humidity as well as different aerosol sizes, shapes, and properties. However, there is little literature on the lower sections of the human airways. Herein, a detailed review of the fundamentals for both in vitro experiments and numerical simulation at different sections of human airways is done. Exceptional features and essential developments in numerical methods for aerosol motion in healthy and diseased human airways are also discussed. Challenges and limitations associated with the applications of in vitro experiments and CFD methods on both human-specific and idealized models are highlighted. The possibility of airborne transmission pathways for COVID-19 has been discussed. Overall, this review provides the most useful approach for carrying out two-phase flow investigations at different sections of the human lungs and under different inhalation statuses. Additionally, new research gaps that have developed recently on the role of bioaerosols motion in COVID-19 transmission, as well as the deposition of aerosols in impaired human airways due to coronavirus (COVID-19) are underlined.

Single-walled carbon nanotubes (SWCNTs) are widely utilized for industrial, biomedical, and environmental purposes. The toxicity of Carboxylated SWCNTs (SWCNTs−COOH) in in vivo models, particularly Caenorhabditis elegans (C. elegans), and in vitro human cells is still unclear. In this study, C. elegans was used to study the effects of SWCNTs−COOH on lethality, lifespan, growth, reproduction, locomotion, reactive oxygen species (ROS) generation, and the antioxidant system. Our data show that exposure to ≥1 μg·L−1 SWCNTs−COOH could induce toxicity in nematodes that affects lifespan, growth, reproduction, and locomotion behavior. Moreover, the exposure of nematodes to SWCNTs−COOH induced ROS generation and the alteration of antioxidant gene expression. SWCNTs−COOH induced nanotoxic effects at low dose of 0.100 or 1.00 μg·L−1, particularly for the expression of antioxidants (SOD-3, CTL-2 and CYP-35A2). Similar nanotoxic effects were found in human cells. A low dose of SWCNTs−COOH induced ROS generation and increased the expression of catalase, MnSOD, CuZnSOD, and SOD-2 mRNA but decreased the expression of GPX-2 and GPX-3 mRNA in human monocytes. These findings reveal that background-level SWCNTs−COOH exerts obvious adverse effects, and C. elegans is a sensitive in vivo model that can be used for the biological evaluation of the toxicity of nanomaterials.

Single-walled carbon nanotubes (SWCNTs) are widely utilized for industrial, biomedical, and environmental purposes. The toxicity of Carboxylated SWCNTs (SWCNTs-COOH) in in vivo models, particularly

As yet, the effect of biodiesels on the emissions of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from heavy-duty diesel engines (HDDEs) has only been studied using limited fuel blend ratios. To clarify the influence of using higher fractions of biodiesel on the emissions of toxic organic pollutants from diesel engines, in this research, the emissions of PM, PAHs, and persistent organic pollutants (POPs) from EURO IV and EURO III HDDEs fueled by low to high waste cooking oil (WCO)-based biodiesel-petrodiesel fuel blends were studied, including D100 (0% biodiesel), B20 (20%), B40 (40%), B60 (60%), B80 (80%), and B100 (100%). The engines were tested according to the US FTP-75 test procedure. The results for the EURO IV diesel engine showed that the PM and toxic organic pollutant emissions were reduced with increases in the blending ratio up until the B60 scenario when compared to the D100 scenario. This is because biodiesel has higher oxygen content and no or lower aromatic content than petrodiesel. Nevertheless, during the B80 and B100 scenarios, the PM and toxic organic pollutant emissions increased due to the high viscosity property of biodiesel, which negatively affected the combustion process. The biodiesel effect on the emissions from EURO III engine was more pronounced because of its lower combustion efficiency, and therefore the improvement in combustion using biodiesel resulted in greater PCDD/F reductions.

Cooking oil fumes (CF) coming from night market stalls exhaust contain substantial amounts of air pollutants such as carbonyl compounds that may contribute to outdoor air pollution and may have adverse health effects on the Taiwanese population. Carbonyl emission characteristics depend on several factors, which include but are not limited to, the cooking style and food material being used. The current study evaluated carbonyl compound emissions from two scenarios: a standard kitchen cooking classroom with a stack gas tunnel and night market food stalls. The different cooking styles and food types cooked using a liquefied petroleum gas (LPG) stove, such as grilled chicken with (GCS) and without sauce (GC), mixed barbecue with sauce (MBS), grilled vegetables with sauce (GVS), stir-fried oyster omelet (OM), fried Taiwanese chicken nuggets (FN) in the kitchen cooking classroom, and grilled chicken with (GCS) and without sauce (GC), stir-fried oyster omelet (OM), grilled vegetables with sauce (GVS), and fried steak (FS) in the night market were evaluated for carbonyl carbon emissions. OM from the kitchen classroom and GCS from the night market showed the highest mean total carbonyl compound concentrations (1850 ± 682 ppb and 1840 ppb). Formaldehyde was found to be the most predominant carbonyl compound, with contribution percentages ranging from 70.9–99.58% of the total carbonyl emission factors in CFs. Grilled vegetables with sauce had the highest emission factor magnitude of 274 µg kg–1 wt. Factors such as the addition of sauce and grilling were also observed to increase carbonyl compound emissions. Corresponding health risks of carbonyl compounds in CFs for the night market vendors were also assessed. All values for cancer risk (R) were above the standard R value for workplace exposure, and HQ values were all greater than 1, suggesting a high risk for adverse health effects. Although our reported values were relatively high due to our sampling conditions, our study was first to be conducted in Taiwan and holds an important contribution to the global existing data of carbonyl compound emissions.

Concerns about the effects of nanoparticles (NPs) on human health are being raised by researchers because the risks of nanocosmetics like sunscreen are unknown. We explored the association between urinary oxidative stress markers and exposure of cosmetics salesclerks to 20 cosmetics that might contain titanium dioxide (TiO2)/zinc oxide (ZnO) NPs. We then recruited 40 cosmetics salesclerks and 24 clothing salesclerks and categorized them based on their exposure to ZnO and TiO2 NPs. Nineteen and 15 samples met the EU definition for TiO2 and ZnO nanomaterials, respectively. Participants with a higher co-exposure index of ZnO and TiO2 NPs had a significantly higher base level of urinary 8-hydroxy-2&prime, deoxyguanosin (8-OHdG) concentrations than the lower co-exposure group (5.82 vs. 2.85 ng/mL, p &lt, 0.001). After potential confounding factors had been adjusted for, the TiO2 and ZnO NP co-exposure index was significantly positively associated with the urinary 8-OHdG base concentration (&beta, = 0.308, 95% CI = 0.106 to 0.510) and the creatinine-adjusted concentration (&beta, = 0.486, 95% CI = 0.017 to 0.954). Current evidence suggests that the likelihood of harm from using sunscreens containing nanoparticles might result in higher urinary 8-OHdG. However, our limited number and types of sample cosmetics might underestimate the risk.

Exposure assessment is a key component in the risk assessment of engineered nanomaterials (ENMs). While direct and quantitative measurements of ENMs in complex environmental matrices remain challenging, environmental fate models (EFMs) can be used alternatively for estimating ENMs’ distributions in the environment. This review describes and assesses the development and capability of EFMs, focusing on surface waters. Our review finds that current engineered nanomaterial (ENM) exposure models can be largely classified into three types: material flow analysis models (MFAMs), multimedia compartmental models (MCMs), and spatial river/watershed models (SRWMs). MFAMs, which is already used to derive predicted environmental concentrations (PECs), can be used to estimate the releases of ENMs as inputs to EFMs. Both MCMs and SRWMs belong to EFMs. MCMs are spatially and/or temporally averaged models, which describe ENM fate processes as intermedia transfer of well-mixed environmental compartments. SRWMs are spatiotemporally resolved models, which consider the variability in watershed and/or stream hydrology, morphology, and sediment transport of river networks. As the foundation of EFMs, we also review the existing and emerging ENM fate processes and their inclusion in recent EFMs. We find that while ENM fate processes, such as heteroaggregation and dissolution, are commonly included in current EFMs, few models consider photoreaction and sulfidation, evaluation of the relative importance of fate processes, and the fate of weathered/transformed ENMs. We conclude the review by identifying the opportunities and challenges in using EFMs for ENMs.

In 2017, the seasonal variations in the wet deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in ambient air were evaluated in Taiwan. The results showed the annual wet deposition fluxes of total-PCDD/Fs-WHO2005-TEQ to be 42.5 pg WHO2005-TEQ m–2 month–1, and the seasonal distributions were 53.3, 62.9, 26.7 and 27.1 pg WHO2005-TEQ m–2 month–1 in spring, summer, autumn and winter, respectively. The average Stot of total-PCDD/Fs-WHO2005-TEQ was 12300. There were obvious seasonal variations in Stot, for which the values were 13840, 6540, 8280 and 20540 in spring, summer, autumn, and winter, respectively. The average concentration of total-PCDD/Fs-WHO2005-TEQ in the rain were 0.453, 0.176, 0.218 and 0.649 pg WHO2005-TEQ L–1 in spring, summer, autumn and winter, respectively. Atmospheric deposition is the major removal pathway for PCDD/Fs. The results of this study provide an evaluation of the adverse effects of PCDD/Fs exposure on human health, and provide a reason for the government to be concerned and to enact better control on air pollution.

Air pollution was getting worse and worse with the development of economic, and atmospheric deposition was an important mechanic for the removal of air pollutants. During 2017, the average dry deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in various areas in Taiwan range between 57 (Lienchiang County in autumn) and 589 pg WHO2005-TEQ m–2 month–1 (Keelung City in winter), with an average of 221 pg WHO2005-TEQ m–2 month–1. The average total deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in various areas in Taiwan range between 65 (Lienchiang County in autumn) and 681 pg WHO2005-TEQ m–2 month–1 (Keelung City in winter), with an average of 263 pg WHO2005-TEQ m–2 month–1. The fractions of dry deposition fluxes contribute to the total deposition fluxes range between 37.8% (Yilan County in winter) and 99.9% (Kaohsiung City in winter), with an average of 82.1%.

An integrated cobalt oxide catalyst supported on silica (Co3O4/SiO2) packed in the lumen of tubular alumina (Al2O3) membrane was designed to realize a Fenton-like oxidation coupling with ultrafiltration water treatment technology to remove persistent and hazardous pollutants. We employed a selection of SiO2 support materials with a range micro/mesostructures to immobilize the Co3O4 catalyst. These were evaluated and screened to achieve the highest pollutant decolorization rate and maximum decolorization efficiency. Then, an integrated catalyst-membrane was developed as proof-of-concept for advanced water treatment. Batch degradation results showed acid orange 7 dye (AO7) was effectively removed using Co3O4 deposited on MCM-41 silica, with 97% decolorization efficiency achieved in 15 mins owing to the large surface area and high porosity of the MCM-41 support. In contrast, humic acid (HA) was relatively difficult to degrade using this catalyst, and was however found to inhibit AO7 degradation. The integrated catalyst-membrane successfully removed both AO7 and HA with only a 10% water flux reduction from 25.0 to 22.5 kg m−2 h−1 bar−1 with excellent co-pollutant removal rate of 99% over 40 h. Furthermore, the integrated catalyst-membrane also removed a range of organic pollutants (neutral red, tetracycline hydrochloride, oxytetracycline) achieving > 90% rejection and 30 kg m−2 h−1 bar−1. These results show that the integrated catalyst-membrane can effectively purify a binary pollutant mixture containing both hazardous dye and natural organic matter and other pharmaceutical chemicals whilst producing process water for recycling and reuse.

Composite photocatalysts comprising graphitic carbon nitride (g-C3N4) and graphene materials were synthesized and evaluated in the photocatalysis of bisphenol A (BPA) with a focus on elucidating the reaction mechanism. Embedding reduced graphene oxide (rGO) to g-C3N4 significantly accelerated the photocatalysis rate of BPA by three folds under visible light irradiation at neutral pH. We showed that rGO synthesized in intimate contact with g-C3N4 increased the surface areas and electrical conductivity of the g-C3N4 composites and promoted the electron-hole pair separation. The BPA photodegradation mechanism involved selective oxidants as superoxide (O2•−) and singlet oxygen (1O2) that were formed through one-electron reduction of O2 and the unique oxidation of O2•− by photogenerated hole (h+), respectively. The synthesized photocatalyst exhibited superior visible light photoreactivity to that of N-doped P25 TiO2, good photo-stability and reuse potential, and was operative in complex wastewater. rGO embedded g-C3N4 achieved good photomineralization of BPA at 80% in 4 h compared to 40% of bare g-C3N4. This study sheds light on the photocatalysis mechanism of BPA with a metal-free, promising rGO/g-C3N4 photocatalyst.

Photocatalytic, hollow fiber membranes based on nanocomposites of titania nanoparticles and carbonaceous char were simultaneously fabricated in a single calcination step, and then optimized for the photo-degradation of pollutants and water recovery in an integrated membrane operation in this study. The physicochemical, mechanical and photocatalytic properties along with separation performance of two series of membranes were finely-tuned by systematically changing the calcination temperature (series 1: 500–1000 °C for 8 h holding time) and calcination time (series 2: 2–8 h at 600 °C). The calcined membranes were extensively characterized for morphology, thermal stability, microstructure, modulus and chemical compositions. Both constituents of titania and char are essential in deriving the desirable hollow fiber properties and membrane performance for photocatalysis and water recovery. By controlling the calcination conditions, membranes prepared at 600 °C for the 3 and 6 h duration displayed an optimal balance between enhanced mechanical strength (34 MPa) and high photo-degradation of acid orange 7 (90.4%). Membrane performance demonstrated water fluxes of 6.9 (H2O/dark), 12.9 (H2O/UV) 4.8 (AO7/dark) and 7.9 L m–2 h–1 (AO7/UV) with excellent organic dye rejection. Both membranes exhibited photo-induced super-hydrophilicity and defouling potential under the influence of UV light due to the photo-activation of exposed TiO2 nanoparticles on the membrane surface. The detailed mechanism of property correlation and separation performance for the photocatalytic hollow fibers is proposed and elucidated. This work offers an innovative material for the research avenue of photocatalytic, hollow fiber membrane reactors for advanced membrane treatment applications.\ud \ud

Silver nanoparticles (AgNPs) have shown to be toxic to freshwater cyanobacterial species, and sodium hypochlorite (NaOCl) is a common oxidant for the treatment of cyanobacterial cells. AgNPs have a high possibility of co-existing with the cyanobacterial cells in the aqueous environments leading to its exposure to NaOCl during water treatment; however, their combined effects on the cyanobacterial cells are largely undocumented. This work compares the individual and combined effect of AgNP and NaOCl on the integrity and toxin (microcystins) release of Microcystis aeruginosa at varying levels. The results show that the AgNP (0.2-0.6 mg/L) alone has negligible effects on the cell lysis, while NaOCl alone shows concentration-dependent (0.2 0.4 0.6 mg/L) rupturing of cells. In contrast, the AgNP + NaOCl (0.2-0.6 mg/L) samples show increasing loss in cell integrity at higher AgNP (0.4 and 0.6 mg/L) levels than the NaOCl only samples. NaOCl exposure results in increasing dissolution of AgNPs with time, releasing silver ions (Ag

To understand the contributions of a raw material storage site for iron ore, coal, limestone, and sinter to ambient air fine particulate matter (PM2.5), the concentrations and chemical fingerprints for resuspended and ambient air PM2.5 were compared. Investigations were done for 15 piles of raw materials, including 5 iron piles, 5 coal piles, 3 stone piles, and a single pile each for coke and sinter. Additionally, four sites, including A, B, C, and D, in the storage site surroundings were chosen to investigate the ambient air PM2.5 concentrations. The concentrations, compositions, and i and j values for PM2.5 varied significantly by season in the four sites under investigation. The chemical fingerprints of the PM2.5 showed that water-soluble ions were the most important component in all sites. Specifically, SO42– and NO3– were the predominant water-soluble ions in winter and summer, respectively. The most dominant components in the iron ore, coal, limestone, coke, and sinter piles were iron, carbon, Ca2+ and carbon, carbon and SO42–, and Fe and Ca2+, respectively. During the summer, PM2.5 concentrations ranged from 13.7–18.0 µg m–3, where the chemical composition of water-soluble ions, metals, carbon accounted for 54.2%, 5.7%, and 23.7% respectively. During winter, the concentrations ranged from 44.7–48.0 µg m–3, where the water-soluble ions, metals, carbon components accounted for 49.2%, 8.1%, and 17.4% respectively. From the chemical mass balance, the main sources of PM2.5 in sites B, C, and D were stationary sources, mobile sources, and secondary organic aerosols. To effectively address the air pollution threat associated with the surroundings of a raw material storage site, the environmental protection agency should formulate measures to effectively reduce the contribution of resuspended dust and other pollution sources to ambient air PM2.5.

Introduction Exhaled breath condensate (EBC) is an emerging and noninvasive specimen allowing the study of lung processes. EBC could be an ideal biological matrix, as it could provide information about the deposited dose. The purpose of this study is to examine whether exhaled UFP in EBC could be correlated with exposure levels or surrogate of nanoparticle exposure. Methods 18 TiO 2 -exposed nanomaterial workers and 23 non-exposed controls were recruited from nanotechnology factories. A questionnaire was used to collect personal information. EBC was collected by an ECoScreen turbo (Viasys GmbH, Hochberg, Germany) and stored at −80°C until analysis. The particle size-number distribution of ultrafine particles (PM0.1) were assessed in the EBC samples with the NanoSight LM10 HS system (Nanosight Ltd., Salisbury, UK) using the Nanoparticle Tracking Analysis (NTA) method. The results were expressed as average size(nm) mode size(nm) concentration ((x108 #particles/mL), % of UFP and particles number of UFP). Result The average size of particles (nm) in TiO2 exposed worker was smaller than non-exposed workers. The concentration of particles (x10 8 #particles/mL) in TiO2 exposed worker was higher than non-exposed workers. However, there was no significant difference between TiO 2 exposed and controls in the average size(nm), mode size(nm), concentration (x10 8 #particles/mL), % of UFP and particles number of UFP. But we found that the particles number of UFP in females was significantly higher than in males. Discussion The possible reason for no association between nanomaterial exposure and particle concentration in EBC may be due to the storage of EBC in −80°C refrigerator for a period of time which may induce aggregation or agglomeration of nanoparticles. Further study is required to clarify the use of exhaled UFP in fresh EBC as exposure matrix.

In this study, the polychlorinated dibenzo-p-dioxin/furan (PCDD/F) levels in 381 soil samples coming from different background areas (n = 238) and contaminated areas (n = 143) in Taiwan were investigated from 2011 to 2015 using high resolution gas chromatograph/high resolution mass spectrometry (HRGC/HRMS). The contaminated areas showed higher PCDD/F contamination as compared to the background areas (1230 vs 749 pg/g dry weight (dw)); 14.0 vs 6.25 pg WHO2005-TEQ/g dw). The lowest levels were recorded in the outlying islands (1.28 pg WHO2005-TEQ/g dw). PCDD/F congener distribution profiles in the background and contaminated areas as well as on the islands varied. OCDD was the dominant congener in almost all locations, including the northern background (87.7%) and central contaminated (74.2%) areas. Other dominant species included OCDF and 1,2,3,4,6,7,8-HpCDD. Levels of PCDD/F-TEQs in Taiwanese soils, including the background areas, were higher than in some developing countries and regions with global background levels due to high industrialization except for the contaminated areas. Geographic differences in dioxin-contaminated soils were also shown in this study. Higher soil dioxin-TEQs were observed in locations with high populations and population densities. Despite the limitations, the economic status of Taiwan represented by the annual averaged family income (AAFI) was positively correlated to soil dioxin-TEQs.

Carbon nanotubes (CNTs) have one of the highest production volumes among carbonaceous engineered nanoparticles (ENPs) worldwide and are have potential uses in applications including biomedicine, nanocomposites, and energy conversion. However, CNTs possible widespread usage and associated likelihood for biological exposures have driven concerns regarding their nanotoxicity and ecological impact. In this work, we probe the responses of planar suspended lipid bilayer membranes, used as model cell membranes, to functionalized multi-walled carbon nanotubes (MWCNT), CdSe/ZnS quantum dots, and a control organic compound, melittin, using an electrophysiological measurement platform. The electrophysiological measurements show that MWCNTs in a concentration range of 1.6–12 ppm disrupt lipid membranes by inducing significant transmembrane current fluxes, which suggest that MWCNTs insert and traverse the lipid bilayer membrane, forming transmembrane carbon nanotubes channels that allow the transport of ions. This paper demonstrates a direct measurement of ion migration across lipid bilayers induced by CNTs. Electrophysiological measurements can provide unique insights into the lipid bilayer–ENPs interactions and have the potential to serve as a preliminary screening tool for nanotoxicity.

Lipid bilayers are biomembranes common to cellular life and constitute a continuous barrier between cells and their environment. Understanding the interaction of engineered nanomaterials (ENMs) with lipid bilayers is an important step toward predicting subsequent biological effects. In this study, we assess the effect of varying the surface functionality and concentration of 10-nm-diameter gold (Au) and titanium dioxide (TiO(2)) ENMs on the disruption of negatively charged lipid bilayer vesicles (liposomes) using a dye-leakage assay. Our findings show that Au ENMs having both positive and negative surface charge induce leakage that reaches a steady state after several hours. Positively charged particles with identical surface functionality and different core compositions show similar leakage effects and result in faster and greater leakage than negatively charged particles, which suggests that surface functionality, not particle core composition, is a critical factor in determining the interaction between ENMs and lipid bilayers. The results suggest that particles permanently adsorb to bilayers and that only one positively charged particle is required to disrupt a liposome and trigger the leakage of its entire contents in contrast to mellitin molecules, the most widely studied membrane lytic peptide, which requires hundred of molecules to generate leakage.