Interaction of nanoplastics with simulated biological fluids and their effect on the biofilm formation

A Comparative Study on the Interaction Between Protein and PET Micro/Nanoplastics: Structural and Surface Characteristics of Particles and Impacts on Lung Carcinoma Cells (A549) and Staphylococcus aureus

The interaction between particles and proteins is a key factor determining the toxicity responses of particles. Therefore, this study aimed to examine the interaction between the emerging pollutant polyethylene terephthalate micro/nanoplastics from water bottles with bovine serum albumin. The physicochemical characteristics of micro/nanoplastics were investigated using nuclear magnetic resonance, x-ray diffraction, Fourier transform infrared, dynamic light scattering, and x-ray energy dispersive spectroscopy after exposure to various concentrations and durations of protein. Furthermore, the impact of protein-treated micro/nanoplastics on biological activities was examined using the mitochondrial activity and membrane integrity of A549 cells and the activity and biofilm production of Staphylococcus aureus. The structural characteristics of micro/nanoplastics revealed an interaction with protein. For instance, the assignment of protein-related new proton signals (e.g., CH2, methylene protons of CH2O), changes in available protons s (e.g., CH and CH3), crystallinity, functional groups, elemental ratios, zeta potentials (-11.3 ± 1.3 to -12.4 ± 1.7 to 25.5 ± 2.3 mV), and particle size (395 ± 76 to 496 ± 60 to 866 ± 82 nm) of micro/nanoplastics were significantly observed after protein treatment. In addition, the loading (0.012-0.027 mM) and releasing (0.008-0.013 mM) of protein also showed similar responses with structural characteristics. Moreover, the cell-based responses were changed regarding the structural and surface characteristics of micro/nanoplastics and the loading efficiencies of protein. For example, insignificant mitochondrial activity (2%-10%) and significant membrane integrity (12%-28%) of A549 cells increased compared with control, and reductions in bacterial activity (5%-40%) in many cases and biofilm production specifically at low dose of all treatment stages (13%-46% reduction) were observed.

Deciphering the molecular interaction of extracellular polymeric substances of a marine bacterium Pseudomonas furukawaii PPS-19 with petroleum hydrocarbons and development of bioadsorbent

Petroleum hydrocarbon contamination is a serious hazard to marine environments, affecting ecosystems and marine life. However, extracellular polymeric substances (EPS) of marine bacteria constituting various hydrophilic and hydrophobic functional groups sequester petroleum hydrocarbons (PHs). In this study, interaction of EPS of Pseudomonas furukawaii PPS-19 with PHs such as crude oil, n-dodecane, and pyrene and its impact on PHs adsorption was investigated. Protein component of EPS was increased after treatment with PHs. Red shift of UV-Vis spectra implied change in molecular structure of EPS. Functional groups of proteins (CO, NH2) and polysaccharides (C-C, C-OH, C-O-C) predominantly interacted with PHs. Interaction with PHs affected secondary structure of EPS. Change in binding energies of corresponding functionalities of C 1s, O 1s, and N 1s confirmed the interaction. Disruption of crystalline peaks led to increased pore size in EPS primarily due to the increase in surface electronegativity. Static quenching mechanism unveils formation of complex between fulvic acid of EPS and PHs. Relative expression of alg8 gene was significantly increased in the presence of n-dodecane (6.31 fold) (P < 0.05; One way ANOVA). n-dodecane and pyrene adsorption capacity of Immobilized EPS was significantly higher (356.5 and 338.2 mg g-1, respectively) (P < 0.001; One way ANOVA) than control. Adsorption rate fits into the pseudo-second-order kinetic model. This study establishes that interaction of PHs causes structural and physical changes in EPS and EPS could be used as an adsorbent material for the sequestration of PHs pollution.

Oxidative stress, biofilm-formation and activity responses of P. aeruginosa to microplastic-treated sediments: Effect of temperature and sediment type

Climate change and plastic pollution are the big environmental problems that the environment and humanity have faced in the past and will face in many decades to come. Sediments are affected by many pollutants and conditions, and the behaviors of microorganisms in environment may be influenced due to changes in sediments. Therefore, the current study aimed to explore the differential effects of various microplastics and temperature on different sediments through the metabolic and oxidative responses of gram-negative Pseudomonas aeruginosa. The sediments collected from various fields including beaches, deep-sea discharge, and marine industrial areas. Each sediment was extracted and then treated with various microplastics under different temperature (-18, +4, +20 and 35 °C) for seven days. Then microplastics were removed from the suspension and microplastic-exposed sediment samples were incubated with Pseudomonas aeruginosa to test bacterial activity, biofilm, and oxidative characteristics. The results showed that both the activity and the biofilm formation of Pseudomonas aeruginosa increased with the temperature of microplastic treatment in the experimental setups at the rates between an average of 2-39 % and 5-27 %, respectively. The highest levels of bacterial activity and biofilm formation were mainly observed in the beach area (average rate +25 %) and marine industrial (average rate +19 %) sediments with microplastic contamination, respectively. Moreover, oxidative characteristics significantly linked the bacterial activities and biofilm formation. The oxidative indicators of Pseudomonas aeruginosa showed that catalase and glutathione reductase were more influenced by microplastic contamination of various sediments than superoxide dismutase activities. For instance, catalase and glutathione reductase activities were changed between -37 and +169 % and +137 to +144 %, respectively; however, the superoxide dismutase increased at a rate between +1 and + 21 %. This study confirmed that global warming as a consequence of climate change might influence the effect of microplastic on sediments regarding bacterial biochemical responses and oxidation characteristics.

Culture dependent analysis of bacterial activity, biofilm-formation and oxidative stress of seawater with the contamination of microplastics under climate change consideration

Temperature changes due to climate change and microplastic contamination are worldwide concerns, creating various problems in the marine environment. Therefore, this study was carried out to discover the impact of different temperatures of seawater exposed to different types of plastic materials on culture dependent bacterial responses and oxidative characteristics. Seawater was exposed to microplastics obtained from various plastic materials at different temperature (-18, +4, +20, and +35 °C) for seven days. Then microplastics were removed from the suspension and microplastic-exposed seawater samples were analyzed for bacterial activity, biofilm formation and oxidative characteristics (antioxidant, catalase, glutathione, and superoxide dismutase) using Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus. The results showed that the activity and biofilm formation of Pseudomonas aeruginosa and Staphylococcus aureus were affected through oxidative stress by catalase, glutathione, and superoxide dismutase due to the microplastic deformation by temperature changes. This study confirms that temperature changes as a result of climate change might influence microplastic degradation and their contamination impact in seawater in terms of bacterial metabolic and oxidation reactions.

Continuous generation and release of microplastics and nanoplastics from polystyrene by plastic-degrading marine bacteria

Plastic waste released into the environments breaks down into microplastics due to weathering, ultraviolet (UV) radiation, mechanical abrasion, and animal grazing. However, little is known about the plastic fragmentation mediated by microbial degradation. Marine plastic-degrading bacteria may have a double-edged effect in removing plastics. In this study, two ubiquitous marine bacteria, Alcanivorax xenomutans and Halomonas titanicae, were confirmed to degrade polystyrene (PS) and lead to microplastic and nanoplastic generation. Biodegradation occurred during bacterial growth with PS as the sole energy source, and the formation of carboxyl and carboxylic acid groups, decreased heat resistance, generation of PS metabolic intermediates in cultures, and plastic weight loss were observed. The generation of microplastics was dynamic alongside PS biodegradation. The size of the released microplastics gradually changed from microsized plastics on the first day (1344 nm and 1480 nm, respectively) to nanoplastics on the 30th day (614 nm and 496 nm, respectively) by the two tested strains. The peak release from PS films reached 6.29 × 106 particles/L and 7.64 × 106 particles/L from degradation by A. xenomutans (Day 10) and H. titanicae (Day 5), respectively. Quantification revealed that 1.3% and 1.9% of PS was retained in the form of micro- and nanoplastics, while 4.5% and 1.9% were mineralized by A. xenomutans and H. titanicae at the end of incubation, respectively. This highlights the negative effects of microbial degradation, which results in the continuous release of numerous microplastics, especially nanoplastics, as a notable secondary pollution into marine ecosystems. Their fates in the vast aquatic system and their impact on marine lives are noted for further study.

Exposure to phagolysosomal simulated fluid altered the cytotoxicity of PET micro(nano)plastics to human lung epithelial cells

The occurrence of micro(nano)plastics into various environmental and biological settings influences their physicochemical and toxic behavior. Simulated body fluids are appropriate media for understanding the degradation, stability, and interaction with other substances of any material in the human body. When the particles enter the human body via inhalation, which is one of the avenues for micro(nano)plastics, they first come into contact with the lung lining fluid under neutral conditions and then are phagocytosed under acidic conditions to be removed. Therefore, it is important to examine the physicochemical transformation and toxicity characteristics after interaction with phagolysosomal simulant fluid (PSF). Here, we focused on exploring how the physicochemical differences (e.g. surface chemistry, elemental distribution, and surface charge) of micro(nano)plastics under pH 4.5 phagolysosome conditions impact cytotoxicity and the oxidative characteristics of lung epithelia cells. The cytotoxicity of lung epithelia cells to those treated with PSF and non-treated micro(nano)plastics was tested by various viability indicators including cell counting kit-8 (CCK-8), MTT, and LDH. Furthermore, the cytotoxicity background was examined through the oxidative processes (e.g. reactive oxygen species, antioxidant, superoxide dismutase (SOD), catalase, and reduced glutathione). The results showed that all tested surface physicochemical characteristics were significantly influenced by the phagolysosome conditions. The staged responses were observed with the treatment duration, and significant changes were calculated in carbonyl, carbon-nitrogen, and sulfonyl groups. Moreover, the negativity of the zeta potentials declined between exposure of 2-40 h and then increased at 80 h compared to control owing to the chemical functional groups and elemental distribution of the plastic particles. The tested viability indicators showed that the micro(nano)plastics treated with PSF were cytotoxic to the lung epithelia cells compared to non-treated micro(nano)plastics, and SOD was the dominant enzyme triggering cytotoxicity due to the particle degradation and instability.

A characterization and an exposure risk assessment of microplastics in settled house floor dust in Istanbul, Turkey

The presence of microplastics in the indoor environment presents growing environmental and human health risks because of their physicochemical and toxic characteristics. Therefore, we aimed to isolate, identify, and characterize plastic debris in settled house floor dusts. This study is a rare study which assess the risks of plastic debris in settled house dust through multiple approaches including the estimated daily intake, pollution loading index, and polymer hazard index. The results indicated that polyethylene and polypropylene were the predominate polymer type of plastic debris in settled house dust with various shapes and colors. The risk assessment results also indicated the serious impact of microplastics in terms of extremely dangerous contamination as well as the fact that they present a polymer hazard. Results indicated that humans have a higher risk of exposure to microplastics via ingestion rather than inhalation. In addition, infants had a higher risk of potential intake compared to other age groups.

Characterizing the interaction between micro(nano)plastics and simulated body fluids and their impact on human lung epithelial cells

Micro(nano)plastics are considered an emerging threat to human health because they can interact with biological systems. In fact, these materials have already been found in the human body, such as in the lungs. However, limited data are available on the behavior of these materials under biological conditions and their impact on human cells, specifically on alveolar epithelial cells. In this study, micro(nano)plastics were exposed to various simulated biological fluids (artificial lysosomal fluids and Gamble's solution) for 2-80 h. Pristine and treated plastic particles were characterized based on their surface chemistry, zeta potentials, and elemental composition. Various toxicological endpoints (mitochondrial membrane potential, lactate dehydrogenase, protein, and antioxidant levels) were examined using A549 lung carcinoma cells. The surface characteristics of the treated micro(nano)plastics and the toxicological endpoints of A549 cells were found to be influenced by the simulated biological media, specifically with high concentrations of the treated micro(nano)plastics and increasing exposure under biological conditions. Moreover, the toxicological endpoints were strongly linked to the chemistry of plastics and included multiple processes in response to the plastics; different biological pathways were obtained in artificial lysosomal fluid and Gamble's solution.

Elemental, Oxidative and Functional Group Characteristics of Sediments in the Industrial Marine area in Tuzla Aydinli Bay, Istanbul, Turkey Between 2016 and 2020

This study aimed to examine particle and surface characteristics of sediments from three sampling areas‒the industrial marine area in Aydinli Bay, the Marmara Sea, and the river tributaries of Aydinli Bay in Istanbul, Turkey‒over a period of five years (2016-2020). Since elemental composition and surface functional groups onto sediments characterize sorption of organic and inorganic substances, the study revealed that C, O, Si, and Al were common elements of sediments and Ti, S and Mg were at a relatively low level. The C = O and O-H related groups were at a higher level in the river tributaries and the Marmara Sea than Aydinli Bay. These functional groups have indicated the oxidative or weathering potential of particles. Moreover, the mineralogical nature of the Al-O, Fe-O and Si-O compounds were at a higher level in Aydinli Bay compared to the other sampling fields. Another important surface characteristic was the oxygen to carbon ratio which showed that the oxidation state was higher in the river tributaries.