Biofilms develop from bacteria bound on surfaces that grow into structured communities (microcolonies). Although surface topography is known to affect bacterial colonization, how multiple individual ...settlers develop into microcolonies simultaneously remains underexplored. Here, we use multiscale population-growth and 3D-morphometric analyses to assess the spatiotemporal development of hundreds of bacterial colonizers towards submillimeter-scale microcolony communities. Using an oral bacterium (Streptococcus mutans), we find that microbial cells settle on the surface randomly under sucrose-rich conditions, regardless of surface topography. However, only a subset of colonizers display clustering behavior and growth following a power law. These active colonizers expand three-dimensionally by amalgamating neighboring bacteria into densely populated microcolonies. Clustering and microcolony assembly are dependent on exopolysaccharides, while population growth dynamics and spatial structure are affected by cooperative or antagonistic microbes. Our work suggests that biofilm assembly resembles certain spatial-structural features of urbanization, where population growth and expansion can be influenced by type of settlers, neighboring cells, and further community merging and scaffolding occurring at various scales.
Nanotoxicity of Graphene and Graphene Oxide Seabra, Amedea B; Paula, Amauri J; de Lima, Renata ...
Chemical research in toxicology,
02/2014, Letnik:
27, Številka:
2
Journal Article
Recenzirano
Graphene and its derivatives are promising candidates for important biomedical applications because of their versatility. The prospective use of graphene-based materials in a biological context ...requires a detailed comprehension of the toxicity of these materials. Moreover, due to the expanding applications of nanotechnology, human and environmental exposures to graphene-based nanomaterials are likely to increase in the future. Because of the potential risk factors associated with the manufacture and use of graphene-related materials, the number of nanotoxicological studies of these compounds has been increasing rapidly in the past decade. These studies have researched the effects of the nanostructural/biological interactions on different organizational levels of the living system, from biomolecules to animals. This review discusses recent results based on in vitro and in vivo cytotoxicity and genotoxicity studies of graphene-related materials and critically examines the methodologies employed to evaluate their toxicities. The environmental impact from the manipulation and application of graphene materials is also reported and discussed. Finally, this review presents mechanistic aspects of graphene toxicity in biological systems. More detailed studies aiming to investigate the toxicity of graphene-based materials and to properly associate the biological phenomenon with their chemical, structural, and morphological variations that result from several synthetic and processing possibilities are needed. Knowledge about graphene-based materials could ensure the safe application of this versatile material. Consequently, the focus of this review is to provide a source of inspiration for new nanotoxicological approaches for graphene-based materials.
Nanotechnology is currently driving the dental materials industry to substantial growth, thus reflecting on improvements in materials available for oral prevention and treatment. The present review ...discusses new developments in nanotechnology applied to dentistry, focusing on the use of nanomaterials for improving the quality of oral care, the perspectives of research in this arena, and discussions on safety concerns regarding the use of dental nanomaterials. Details are provided on the cutting-edge properties (morphological, antibacterial, mechanical, fluorescence, antitumoral, and remineralization and regeneration potential) of polymeric, metallic and inorganic nano-based materials, as well as their use as nanocluster fillers, in nanocomposites, mouthwashes, medicines, and biomimetic dental materials. Nanotoxicological aspects, clinical applications, and perspectives for these nanomaterials are also discussed.
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•The surface modification of cellulose nanocrystals as drug delivery system is presented.•The nanotoxicity and Ecotoxicology of nanocellulose-based systems are discussed.•Commercial ...products and patents on cellulose nanocrystals are presented.
Cellulose nanocrystals (CNCs) are crystalline nanoparticles that present myriad applications. CNCs are produced from a variety of renewable sources, and they can be chemically modified. Although there are promising perspectives for introducing CNCs into pharmaceutical formulations, prior to achieving commercial products the influence of many parameters such as extraction and toxicity of the resulting products must be revealed. Since there is great physicochemical flexibility in the steps of obtaining and conjugating CNCs, there are uncountable and complex outcomes from the interactions of those parameters. We present a discussion that helps to unveil the whole panorama on the use of CNCs as drug delivery systems. The methods of producing CNCs are correlated to the resulting nanotoxicity from the cellular to organism level. This review points to relevant concerns that must be overcome to attain safe use of these nanostructures. We also discuss the patents and commercially available products based on CNCs.
Silver nanoparticles in dentistry Noronha, Victor T.; Paula, Amauri J.; Durán, Gabriela ...
Dental materials,
October 2017, 2017-10-00, 20171001, Letnik:
33, Številka:
10
Journal Article
Recenzirano
•AgNPs are applied in nanocomposites; implant coatings; anti-caries formulations; and in the treatment of oral cancer and local anesthesia.•In vitro results reveal the excellent antimicrobial ...activity of AgNPs when associated with acrylic resins, resin co-monomers, adhesives, intracanal medication and implant coatings.•In vivo results also confirm the potential use of AgNPs against microbial infections, especially caries.
Silver nanoparticles (AgNPs) have been extensively studied for their antimicrobial properties, which provide an extensive applicability in dentistry. Because of this increasing interest in AgNPs, the objective of this paper was to review their use in nanocomposites; implant coatings; pre-formulation with antimicrobial activity against cariogenic pathogens, periodontal biofilm, fungal pathogens and endodontic bacteria; and other applications such as treatment of oral cancer and local anesthesia. Recent achievements in the study of the mechanism of action and the most important toxicological aspects are also presented.
Systematic searches were carried out in Web of Science (ISI), Google, PubMed, SciFinder and EspaceNet databases with the keywords “silver nano* or AgNP*” and “dentist* or dental* or odontol*”.
A total of 155 peer-reviewed articles were reviewed. Most of them were published in the period of 2012–2017, demonstrating that this topic currently represents an important trend in dentistry research. In vitro studies reveal the excellent antimicrobial activity of AgNPs when associated with dental materials such as nanocomposites, acrylic resins, resin co-monomers, adhesives, intracanal medication, and implant coatings. Moreover, AgNPs were demonstrated to be interesting tools in the treatment of oral cancers due to their antitumor properties.
The literature indicates that AgNPs are a promising system with important features such as antimicrobial, anti-inflammatory and antitumor activity, and a potential carrier in sustained drug delivery. However, there are some aspects of the mechanisms of action of AgNPs, and some important toxicological aspects arising from the use of this system that must be completely elucidated.
Carbon functional materials (CFMs) such as biochar and hydrochar can be obtained from hundreds of biomass precursors varying from urban sludge to agriculture wastes. They can be produced through tens ...of synthesis methods and postsynthesis processing steps tuned at specific conditions (e.g., temperature, time, and chemical concentrations). To achieve a “rational design” platform for a system with a high dimensional parameter space such as CFMs, we processed 10,975 scientific articles (from years 2000 to 2020) related to the subject with automatic reading–interpreting–extracting computational routines (namely, the a.RIX engine). The a.RIX engine automatically recognized more than a hundred precursors, among which wheat straw, rice husk, and rice straw were the most studied for CFM synthesis and application in agriculture (e.g., as an amendment), as fuel (energy generation), and as an adsorbent. Parameters related to the CFMs’ synthesis conditions, such as carbonization temperature and time, and parameters related to CFMs’ properties, such as surface area and heavy metals adsorption capacity, can also be extracted from the articles. Correlations between the CFM precursors and synthesis conditions indicated very little statistical difference between the carbonization temperature and time used for the CFMs’ synthesis from different precursors. Essentially, precursors are carbonized at temperatures varying from 100 to 900 °C for 30 min to 6 h using pyrolysis, hydrothermal carbonization, and gasification. When focusing the analysis on just CFMs produced by pyrolysis (biochar), we observed that peanut shells can produce materials with higher surface areas than other precursors (P < 0.05). When performing correlations between biochar synthesis conditions and their properties, general trends can be confirmed: (i) the higher the carbonization temperature, the lower the H/C and O/C ratios, and (ii) the increase in the surface area can be achieved by preserving a high aromatic degree (low H/C ratio) and a low oxidation level (low O/C ratio). However, a deeper understanding of the relation between CFM synthesis/postsynthesis methods and the resulting properties can only be achieved using clustering algorithms (e.g., k-means) and complex network analysis. The a.RIX engine groups articles describing optimized synthesis conditions and CFM properties (e.g., low carbonization temperature, low carbonization time, and large surface area and adsorption capacity) and automatically recognizes the synthesis/postsynthesis steps used for these groups. The program efficiently recognized that precursors such as peanut shells can be converted into highly porous biochar by using experimental routes such as “pyrolysis” → “activation” → “drying” → “ashing” → “washing” → “filtration.” With this approach, we show that a noncomputational review of scientific articles for materials with a huge parameter space such as CFMs is largely obsolete. Finally, taken together, the results provide a powerful platform for data-oriented experimental design of CFMs produced from biomass.
The surface microchemical environment of graphene oxide (GO) has so far been oversimplified for understanding practical purposes. The amount as well as the accurate identification of each possible ...oxygenated group on the GO surface are difficult to describe not only due to the complex chemical nature of the oxidation reactions but also due to several intrinsic variables related to the production and chemical processing of GO-based materials. However, to advance toward a more realistic description of the GO chemical environment, it is necessary to distinguish the oxygenated fragments with very peculiar characteristics that have so far been treated as simply graphene oxide. In this way, small oxidized graphitic fragments adsorbed on the GO surface, named oxidation debris or carboxylated carbonaceous fragments (CCFs), have been here separated from commercially available GO. Spectroscopy and microscopy results indicated that the chemical nature of these fragments is different from that of GO. By using the decoration of GO with silver nanoparticles as a conceptual model, it was seen that the presence of oxidation debris on the GO surface greatly influences the associated kinetic processes, mainly due to the nucleation and stabilization capacity for silver nanoparticles provided by the oxidation debris fragments. Consequently, when CCFs are present, Ag nanoparticles are significantly smaller and less crystalline. Considering the GO microchemical environment pointed out here, these findings can be qualitatively extrapolated to all other covalent and noncovalent functionalizations of GO.
The environmental risks of silica nanoparticles (SiNP) reported in the literature are contradictory and bring into question its safety for use in consumer applications. Organisms are never exposed to ...NPs alone in the real environment, while studies of the combined toxicity of SiNP are limited. To address this, we compared the acute toxicity of fluorescent core-shell SiNPs alone and in mixtures with Cd2+ to Ceriodaphnia dubia in the absence and presence of NOM. We identified biodistribution and feeding behaviour in addition to the traditional endpoints. NOM increased the colloidal stability of SiNPs in reconstituted water. In immobility tests, no significant effects were observed from Cd2+ exposure with NOM and varying concentrations of SiNPs. A similar pattern of curve dose-response was observed for varying concentrations of SiNPs and increasing Cd2+ concentration and constant NOM. Fluorescence microscopy verified a dose-dependent bioaccumulation of SiNPs in C. dubia. Co-exposure to 10 mg L−1 SiNP with NOM and Cd2+ resulted in a stimulated stress feeding response at the lower Cd2+ concentrations which declined at the higher dose due to a functional impairment of the digestive tract. Alterations in feeding behaviour and the increasing bioaccumulation of SiNP indicate a potential ecological risk for Ceriodaphnia dubia from the mixture exposure.
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•No influence of NOM in SiNPs size and surface charge.•NOM reduced the settling of SiNPs in reconstituted water.•No changes were observed in acute mixture toxicity of SiNPs with NOM and Cd2+.•Exposure to SiNPs with NOM and Cd2+ caused significant changes in feeding behavior.•The accumulation of SiNPs in C. dubia gut increased with higher doses.
Although hydrochar and biochar have been used as soil conditioners, there is not a clear understanding of how their properties changes due to aging impacts their colloidal particles behavior on the ...soil system. From this premise, we produced hydrochar and biochar from the same feedstock (cashew bagasse) and aged with different chemical methods: (i) using hydrogen peroxide, (ii) a mixture of nitric and sulfuric acids, and (iii) hot water. It was analyzed the effects of aging on the stability of the carbonaceous materials (CMs) colloids in aqueous medium with different ionic strength (single systems), as well as the stability of the natural-soil colloid when interacting with biochar and hydrochar colloids (binary systems). A chemical composition (C, H, N, and O content) change in CMs due to the chemically induced aging was observed along with minor structural modifications. Chemical aging could increase the amount of oxygen functional groups for both biochar and hydrochar, though in a different level depending on the methodology applied. In this sense, hydrochar was more susceptive to chemical oxidation than biochar. The effectiveness of chemical aging treatments for biochar increased in the order of water < acid < hydrogen peroxide, whereas for hydrochar the order was water < hydrogen peroxide < acid. While the increase in surface oxidation improved the biochar colloidal stability in water medium at different ionic strengths (single systems), the stability and critical coagulation concentration (CCC) slightly changed for hydrochar. Natural-soil clay (NSC) interactions with oxidized carbonaceous material colloids (binary systems) enhanced NSC stability, which is less likely to aggregate. Therefore, the aging of carbonaceous materials modifies the interaction and dynamics of soil small particles, requiring far more attention to the environmental risks due to their application over time.
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•Chemical oxidation effect is different to hydrochar and biochar from same feedstock.•Hydrochar hydrophobicity is resistant to chemical oxidation.•The surface oxidation of biochar largely increased its colloidal stability.•Hydrochar colloids stability slightly changed with chemical oxidation.•Colloids from oxidized carbonaceous materials improved natural-soil colloid stability.
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