Protein corona between nanoparticles and bacterial proteins in activated sludge: Characterization and effect on nanoparticle aggregation

Unraveling the protein corona formation during the surface-enhanced Raman spectroscopy detection of malachite green in fish

In surface-enhanced Raman spectroscopy (SERS) detection of drug residues, food matrices, especially the protein corona around nanomaterials, pose challenges to accurate detection. This study used sea bass, a fish product with a complex matrix, and malachite green as a target fish drug to investigate these effects. Multiple techniques were used to elucidate the interactions among proteins, malachite green, and gold nanoparticles (AuNPs). The detection limit of malachite green in fish extract (740 μg/L) was much higher than in standard solutions (0.42 μg/L). At a protein concentration of 0.5 mg/mL, a uniform protein corona formed around the AuNPs, resulting in an aggregation-sedimentation rate of 9.23 %. Malachite green adsorption by AuNPs decreased by 99 % after protein corona formation. The work reveals how protein corona affects SERS detection of fish drugs, guiding development of signal regulation strategies for enhanced SERS sensitivity in food safety.

In-situ and ex-situ EPS-corona formation on ZnO QDs mitigates their environmental toxicity in the freshwater microalgae Chlorella sp

The current work seeks to understand how the interactions between ZnO QDs and extracellular polymeric substances (EPS) may vary based on the types of EPS (loosely and tightly bound) and modes of eco-corona formation (In-situ or ex-situ). In-situ eco-corona refers to formation of an EPS layer on the QDs during the interactions with the algae whereas the ex-situ condition refers to forming the layer before the interactions. ZnO QDs were added at 0.25, 0.5, and 1.0 mg/L concentrations for pristine, in-situ, and ex-situ corona treatments with the cells. Pristine ZnO QDs induced significant oxidative stress in algal cells, as evident from increased levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase activity. This decreased the photosynthetic efficiency and caused significant growth inhibition in algae. In contrast, both the in-situ and ex-situ corona treatments with loosely bound and tightly bound EPS reduced the oxidative stress, improved the photosynthetic efficiency, and diminished growth inhibition effects. This study asserts the importance of EPS in reducing the toxicity of ZnO QDs, while maintaining the fluorescence activity. This ensures the sustainable usage of the ZnO QDs without any harm to aquatic ecosystems.

Formation of extracellular polymeric substances corona on TiO2 nanoparticles: Roles of crystalline phase and exposed facets

Nanoparticles (NPs) in the environment can interact with macromolecules in the surrounding environment to form eco-corona on their surfaces, which in turn affects the environmental fate and toxicity of nanoparticles. Wastewater treatment plants containing large amounts of microbial extracellular polymeric substances (EPS) are an important source of NPs into the environment, where the formation of EPS coronas on NPs is critical. However, it remains unclear how the crystalline phase and exposed facets, which are intrinsic properties of NPs, affect the formation of EPS coronas on NPs. This study investigated the formation of EPS corona on three TiO2 NPs (representing the most widely used engineered NPs) with different crystalline phases and exposed facets. The protein type and abundance in EPS coronas on TiO2 NPs varied depending on the crystalline phase and exposed facets. Anatase with {101} facets and {001} facets preferred to adsorb proteins with lower molecular weights and higher H-bonding relevant amino acids, respectively, while EPS corona on rutile with {110} facets had proteins with higher hydrophobicity. In addition, the selective adsorption of proteins was primarily determined by steric hindrance, hydrogen bonding, and hydrophobic interaction between TiO2 NPs and proteins, which were affected by changes in aggregation state, surface hydroxyl density, and hydrophobicity of TiO2 NPs induced by crystalline phase and exposed facets. Moreover, crystalline phase and exposed facets-induced EPS corona changes altered the aggregation state and oxidation potential of TiO2-EPS corona complexes. These findings emphasize the important role of crystalline phase and exposed facets in the environmental behavior of nanoparticles and may provide insights into the safe design of nanoparticles.

Enhanced detection of endocrine disrupting chemicals in on-chip microfluidic biosensors using aptamer-mediated bridging flocculation and upconversion luminescence

Exposure to endocrine-disrupting chemicals (EDCs) can lead to detrimental impacts on human health, making their detection a critical issue. A novel approach utilizing on-chip microfluidic biosensors was developed for the simultaneous detection of two EDCs, namely, bisphenol A (BPA) and diethylstilbestrol (DES), based on upconversion nanoparticles doped with thulium (Tm) and erbium (Er), respectively. From the perspective of single nanoparticles, the construction of an active core-inert shell structure enhanced the luminescence of nanoparticles by 2.28-fold (Tm) and 1.72-fold (Er). From the perspective of the nanoparticle population, the study exploited an aptamer-mediated bridging flocculation mechanism and effectively enhanced the upconversion luminescence of biosensors by 8.94-fold (Tm) and 7.10-fold (Er). A chip with 138 tangential semicircles or quarter-circles was designed and simulated to facilitate adequate mixing, reaction, magnetic separation, and detection conditions. The on-chip microfluidic biosensor demonstrated exceptional capabilities for the simultaneous detection of BPA and DES with ultrasensitive detection limits of 0.0076 µg L-1, and 0.0131 µg L-1, respectively. The first reported aptamer-mediated upconversion nanoparticle bridging flocculation provided enhanced luminescence and detection sensitivity for biosensors, as well as offering a new perspective to address the instability of nanobiosensors.

Pre-exposure to Fe2O3 or TiO2 Nanoparticles Inhibits Subsequent Biological Uptake of 55Fe-Labeled Fe2O3 Nanoparticles

Aquatic organisms are frequently exposed to various nanoparticles (NPs) in the natural environment. Thus, studies of NP bioaccumulation should include organisms that have been previously exposed to NPs. Our study investigated the effects of pre-exposure of Tetrahymena thermophila (T. thermophila) to Fe₂O₃ or TiO₂ NPs on the protozoan's subsequent uptake of ⁵⁵Fe-labeled Fe₂O₃ (⁵⁵Fe₂O₃) NPs. Molecular mechanisms underlying the pre-exposure effects were explored in transcriptomic and metabolomic experiments. Pre-exposure to either NPs inhibited the subsequent uptake of ⁵⁵Fe₂O₃ NPs. The results of the transcriptomic experiment indicated that NP pre-exposure influenced the expression of genes related to phagosomes and lysosomes and physiological processes such as glutathione and lipid metabolism, which are closely associated with the endocytosis of ⁵⁵Fe₂O₃ NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in T. thermophila pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of T. thermophila to Fe₂O₃ or TiO₂ NPs inhibited the protozoan's subsequent uptake of ⁵⁵Fe₂O₃ NPs, possibly by mechanisms involving the alteration of endocytosis-related organelles, the induction of oxidative stress, and a lowering of the intracellular energy supply. Thus, NP pre-exposure represents a scenario which can inform increasingly realistic estimates of NP bioaccumulation.

Transcriptome Analysis Reveals the Growth Promotion Mechanism of Enteropathogenic Escherichia coli Induced by Black Phosphorus Nanosheets

With the extensive production and application of black phosphorus (BP) nanosheets, release to the environment is inevitable, which raises concerns about the fate and effects of this two-dimensional (2D) material on sensitive receptors such as environmental microbes. Although the bacterial toxicity of BP nanosheets has been demonstrated, whether the biological response differs in pathogenic and nonpathogenic strains of a microorganism is unknown. Here, enteropathogenic Escherichia coli (EPEC) and nonpathogenic Escherichia coli DH5α (E. coli DH5α), Escherichia coli k12 (E. coli k12), and Bacillus tropicus (B. tropicus) are used to comparatively study the microbial toxicity of BP nanosheets. Upon exposure to BP nanosheets across a range of doses from 10 to 100 μg mL^-1 for 12 h, EPEC experienced enhanced growth and E. coli DH5α and E. coli k12 were not affected, whereas B. tropicus exhibited clear toxicity. By combining transcriptome sequencing, proteome analysis, and other sensitive biological techniques, the mechanism of BP-induced growth promotion for EPEC was uncovered. Briefly, BP nanosheets activate the antioxidation system to resist oxidative stress, promote protein synthesis and secretion to attenuate membrane damage, enhance the energy supply, and activate growth-related pathways. None of these impacts were evident with nonpathogenic strains. By describing the mechanism of strain-dependent microbial effects, this study not only highlights the potential risks of BP nanosheets to the environment and to human health but also calls attention to the importance of model strain selection when evaluating the hazard and toxicity of emerging nanomaterials.

A novel application of dissolved ozone flotation on sewage sludge thickening: Performance and mechanism investigation

Sludge thickening in sewage treatment plants is an essential step to reduce the sewage sludge volume and provide space for collaborative anaerobic digestion of sludge and other urban organic wastes. Dissolved ozone flotation (DOF) is a novel choice worthy of application in the field of sludge thickening. In order to investigate the effect of DOF thickening, the total solid content (TS %) was used to characterize the thickening performance under different O₃ dosage. The optimal condition was determined to be polyacrylamide (PAM) dosage = 3 ‰ TS, air floatation time = 2 h and O₃ dosage = 12 mg/g TS, under which the TS % of raw-sewage sludge (RS) increased from 0.33 ± 0.01 % to 8.03 ± 0.06 %. In this study, the relationship between the sludge thickening performance, physicochemical properties, and the changes of organic matter (content, structure and molecular weight) in extracellular polymers (EPS) was systematically clarified. The results indicated that the DOF couple with PAM could change the sludge surface properties, destroy the sludge floc structure, release intracellular organic matter, and increase moisture fluidity. The surface hydrophilicity/hydrophobicity, protein (PN) secondary structure and moisture distribution were mainly responsible for sludge thickening performance. Moreover, the change of TS % during the DOF thickening process was mainly caused by the variations of the organic matter content in EMPS layer. The identification of key influencing factors was conducive to the further regulation and upgrading of the novel application for enhanced sludge thickening in sewage treatment plants.

Formation of protein corona on interaction of pepsin with chitin nanowhiskers in simulated gastric fluid

Protein corona (PC) usually changes the physicochemical properties of nanoparticles (NPs) and determines their ultimate fate in the physiological environment. As NPs are widely used in food, it is important to obtain a deep understanding of PC formation in the gastrointestinal fluid. Herein, we explored the adsorption of pepsin to chitin nanowhiskers (CNWs) and their interactions in simulated gastric fluid. Results suggest that the binding of pepsin reduced the surface potential of CNWs from 22.4 ± 0.15 to 12.9 ± 0.51 mV and caused their aggregation. CNWs quenched the fluorescence of pepsin and induced slightly changes in its secondary structure containing a reduction in the β-sheet content (∼ 3%) and an increase in the random coils (∼ 2%). The isothermal titration calorimetry (ITC) data suggested that the interaction forces between CNWs and pepsin were mainly hydrogen bonds and van der Waals forces.

Protein interaction, monocyte toxicity and immunogenic properties of cerium oxide crystals with 5% or 14% gadolinium, cobalt oxide and iron oxide nanoparticles - an interdisciplinary approach

Metal oxide nanoparticles are widely used in both consumer products and medical applications, but the knowledge regarding exposure-related health effects is limited. However, it is challenging to investigate nanoparticle interaction processes with biological systems. The overall aim of this project was to improve the possibility to predict exposure-related health effects of metal oxide nanoparticles through interdisciplinary collaboration by combining workflows from the pharmaceutical industry, nanomaterial sciences, and occupational medicine. Specific aims were to investigate nanoparticle-protein interactions and possible adverse immune reactions. Four different metal oxide nanoparticles; CeO_x nanocrystals with 5% or 14% Gd, Co₃O₄, and Fe₂O₃, were characterized by dynamic light scattering and high-resolution transmission electron microscopy. Nanoparticle-binding proteins were identified and screened for HLA-binding peptides in silico. Monocyte interaction with nanoparticle-protein complexes was assessed in vitro. Herein, for the first time, immunogenic properties of nanoparticle-binding proteins have been characterized. The present study indicates that especially Co₃O₄-protein complexes can induce both 'danger signals', verified by the production of inflammatory cytokines and simultaneously bind autologous proteins, which can be presented as immunogenic epitopes by MHC class II. The clinical relevance of these findings should be further evaluated to investigate the role of metal oxide nanoparticles in the development of autoimmune disease. The general workflow identified experimental difficulties, such as nanoparticle aggregate formation and a lack of protein-free buffers suitable for particle characterization, protein analyses, as well as for cell studies. This confirms the importance of future interdisciplinary collaborations.

Environmental dimensions of the protein corona

The adsorption of biomolecules to the surface of engineered nanomaterials, known as corona formation, defines their biological identity by altering their surface properties and transforming the physical, chemical and biological characteristics of the particles. In the first decade since the term protein corona was coined, studies have focused primarily on biomedical applications and human toxicity. The relevance of the environmental dimensions of the protein corona is still emerging. Often referred to as the eco-corona, a biomolecular coating forms upon nanomaterials as they enter the environment and may include proteins, as well as a diverse array of other biomolecules such as metabolites from cellular activity and/or natural organic matter. Proteins remain central in studies of eco-coronas because of the ease of monitoring and structurally characterizing proteins, as well as their crucial role in receptor engagement and signalling. The proteins within the eco-corona are optimal targets to establish the biophysicochemical principles of corona formation and transformation, as well as downstream impacts on nanomaterial uptake, distribution and impacts on the environment. Moreover, proteins appear to impart a biological identity, leading to cellular or organismal recognition of nanomaterials, a unique characteristic compared with natural organic matter. We contrast insights into protein corona formation from clinical samples with those in environmentally relevant systems. Principles specific to the environment are also explored to gain insights into the dynamics of interaction with or replacement by other biomolecules, including changes during trophic transfer and ecotoxicity. With many challenges remaining, we also highlight key opportunities for method development and impactful systems on which to focus the next phase of eco-corona studies. By interrogating these environmental dimensions of the protein corona, we offer a perspective on how mechanistic insights into protein coronas in the environment can lead to more sustainable, environmentally safe nanomaterials, as well as enhancing the efficacy of nanomaterials used in remediation and in the agri-food sector.

Nanoparticles-EPS corona increases the accumulation of heavy metals and biotoxicity of nanoparticles

Microbial extracellular polymeric substances (EPS) coating nanoparticles (NPs) surface can form NPs-EPS corona, which significantly affect the adsorption of NPs to toxic substances and alter the ecotoxicological effect of NPs. In this work, the EPS coronas on TiO₂ NPs (TNPs) and CeO₂ NPs (CNPs) were characterized and the adsorption characteristics of NPs with and without EPS corona to five heavy metals were investigated in single-metal and multiple-metal systems. The results of spectral analysis showed that NPs-EPS corona exhibited new crystalline phases and abundant functional groups. Moreover, 42 and 13 proteins were identified in the TNPs-EPS and CNPs-EPS coronas, respectively. The rates of Cd²⁺, Pb²⁺, Cu²⁺, Ni²⁺ and Ag⁺ adsorption by NPs-EPS corona increased to values that were 6.7-7.6, 4.4-5.1, 4.2-5.5, 3.9-4.9 and 8.5-8.8 times those of NPs without EPS corona, respectively, in single-metal system. NPs-EPS coronas are effective in absorbing Ag⁺, Pb²⁺ and Cu²⁺ compared with Cd²⁺and Ni²⁺ in multiple metal adsorption. These results indicated that NPs-EPS corona effectively adsorb and remove heavy metals by forming NPs-EPS-metal complexes and inducing precipitation. However, NPs-EPS corona can enhance the toxicity of NPs by accumulating highly-toxic heavy metals in aquatic environments.

A new perspective on the toxicity of arsenic-contaminated soil: Tandem mass tag proteomics and metabolomics in earthworms

The toxicity of low-level arsenic (As)-contaminated soil is not well understood. An integrated proteomic and metabolomic approach combined with morphological examination was used to investigate the potential biological toxicity of As-contaminated soil based on an exposure experiment with the earthworm Eisenia fetida. The results showed that the earthworm hindgut accumulated high As concentrations resulting in injury to the intestinal epithelia, chloragogenous tissues and coelom tissues. Furthermore, As-contaminated soil induced a significant increase in betaine levels and a decrease in dimethylglycine and myo-inositol levels in the earthworms, suggesting that the osmoregulatory metabolism of the earthworms may have been disturbed. The significantly altered levels of asparagine and dimethylglycine were proposed as potential biomarkers of As-contaminated soil. The upregulation of soluble calcium-binding proteins and profilin, the downregulation of sodium/potassium-transporting ATPase, and the proteins changes identified by gene ontology enrichment analysis confirmed that the earthworms suffered from osmotic stress. In addition, the significant changes in glycine-tRNA ligase activity and coelomic tissue injury revealed that As accumulation may disturb the earthworm immune system. This work provided new insight into the proteomic and metabolic toxicity of low-level As-contaminated soil ecosystems in earthworms, extended our knowledge of dual omics and highlighted the mechanisms underlying toxicity.

New insights into the effect of sludge proteins on the hydrophilic/hydrophobic properties that improve sludge dewaterability during anaerobic digestion

Extracellular polymer proteins have been reported to play an important role in enhancing sludge dewaterability during anaerobic digestion in our previous study. However, how the proteins in sludge determine sludge dewaterability remains to be determined. In this work, proteins from digested sludge were identified using label free proteomics analysis, and its hydrophilicity/hydrophobicity properties and functional groups were analysed. We determined that the microbial community variation between the three stages during the anaerobic digestion process was responsible for enhancing sludge dewaterability; The transformation from hydrophilicity to hydrophobicity of digested sludge surface is the result of functional groups distribution variation which caused by the proteins and microbial communities. This study provides a new insight into the development of anaerobic digestion based on sludge dewaterability.

Isolation methods for particle protein corona complexes from protein-rich matrices

Background: Nanoparticles become rapidly encased by a protein layer when they are in contact with biological fluids. This protein shell is called a corona. The composition of the corona has a strong influence on the surface properties of the nanoparticles. It can affect their cellular interactions, uptake and signaling properties. For this reason, protein coronae are investigated frequently as an important part of particle characterization. Main body of the abstract: The protein corona can be analyzed by different methods, which have their individual advantages and challenges. The separation techniques to isolate corona-bound particles from the surrounding matrices include centrifugation, magnetism and chromatographic methods. Different organic matrices, such as blood, blood serum, plasma or different complex protein mixtures, are used and the approaches vary in parameters such as time, concentration and temperature. Depending on the investigated particle type, the choice of separation method can be crucial for the subsequent results. In addition, it is important to include suitable controls to avoid misinterpretation and false-positive or false-negative results, thus allowing the achievement of a valuable protein corona analysis result. Conclusion: Protein corona studies are an important part of particle characterization in biological matrices. This review gives a comparative overview about separation techniques, experimental parameters and challenges which occur during the investigation of the protein coronae of different particle types.

Recent progress in drug delivery

Drug delivery systems (DDS) are defined as methods by which drugs are delivered to desired tissues, organs, cells and subcellular organs for drug release and absorption through a variety of drug carriers. Its usual purpose to improve the pharmacological activities of therapeutic drugs and to overcome problems such as limited solubility, drug aggregation, low bioavailability, poor biodistribution, lack of selectivity, or to reduce the side effects of therapeutic drugs. During 2015-2018, significant progress in the research on drug delivery systems has been achieved along with advances in related fields, such as pharmaceutical sciences, material sciences and biomedical sciences. This review provides a concise overview of current progress in this research area through its focus on the delivery strategies, construction techniques and specific examples. It is a valuable reference for pharmaceutical scientists who want to learn more about the design of drug delivery systems.

AgNP combined with quorum sensing inhibitor increased the antibiofilm effect on Pseudomonas aeruginosa

Pseudomonas aeruginosa biofilm lifestyle exhibits multidrug resistance in chronic bacterial infections. Alternative antimicrobial compounds or combination drug therapies must be urgently developed. In this work, the antibiofilm effect of Ag nanoparticle (AgNP) combined with the quorum sensing inhibitor (QSI) 4-nitropyridine N-oxide (4NPO) on P. aeruginosa biofilms was investigated. The biofilm biomass of P. aeruginosa was considerably reduced by 1.56-50 mg/L AgNP. However, 4NPO enhanced the ability of AgNP to inhibit P. aeruginosa biofilm formation (P < 0.05). The combination of AgNP with 4NPO could continuously inhibit biofilm development after 12 h, and 50 mg/L AgNP combined with 6.25 mg/L 4NPO thoroughly suppressed biofilm growth. The expression levels of QS genes and exopolysaccharide genes of biofilm treated with the combination of AgNP with 4NPO (AgNP-4NPO combination) were lower than those treated with AgNP alone (P < 0.05). Additional extracellular proteins and polysaccharides were determined in the samples treated with AgNP-4NPO combination. Based on proteomic analysis, this result was attributed to cell rupture caused by antimicrobial agents and intracellular materials released. The combination of the two antimicrobial agents could weaken the swimming ability of bacterial cells by damaging bacterial flagella and blocking rhlA gene expression. Thus, AgNP combined with QSI showed stronger antibiofilm ability than AgNP alone. These results may contribute to the development of antimicrobial agents.

Identification and function of extracellular protein in wastewater treatment using proteomic approaches: A minireview

Microbial extracellular proteins serve as important functions in wastewater treatment process. Analysis of their compositions and properties is crucial to probe their specific functions. However, conventional analytical techniques cannot obtain interest protein information from complex proteins. Recently, the extracellular proteomics method has been applied to resolve the composition of extracellular proteins. In order to better understand the roles of extracellular protein in wastewater treatment process, this review provides the information on the proteomics methods and their application in investigating extracellular proteins involved in microbial attachment/aggregation, biodegradation of pollutants, and response to environmental stresses. Future work needs to exploit the full capability of the proteome.

Nanoparticle modification in biological media: implications for oral nanomedicines

Nanomedicine has shown potential in enabling oral administration of poorly absorbable drugs, such as biologics. As part of the process related to optimisation of the safety and efficacy of nanomedicines, it is imperative that the interaction of nanoparticles with the biological systems – including the gut – is fully characterised. In this article, we provide an overview of the major mechanisms by which nanoparticles may transform upon introduction in biological media. Specifically, the phenomena of association, dissolution and biomolecule adsorption are discussed, together with factors which influence the occurrence of each phenomenon. The implications of these phenomena within the context of therapeutic action of nanomedicines, which includes reduced targeting efficiency, are also explored. Finally, we will comment on nanoparticle modification within the gut environment, including the currently available gastrointestinal models for the study of nano-bio interactions, with implications in the area of nanomedicines for oral administration.

Nanomedicines undergo transformation in biological media, which impacts biological effects. Such transformation in the gut environment has implications in use of nanomedicines for oral administration.