Current Nanoscience - Volume 16, Issue 3, 2020

Actually, many discussions on the potential risks of silver nanoparticles (AgNPs) have been reported; however, unfortunately, very few considered the great differences between the nature of silver and sources of their syntheses. All data suggested that the effects on toxicity of AgNPs are related to the combination of the specific properties of AgNPs. In this context, this review presents and discusses the recent progress in the nanotoxicity of AgNPs, obtained by different biogenic synthetic protocols, in comparison with chemical synthetic methods, driving to the formation of nanoparticles with diverse structures, and size distributions. Biogenic syntheses of AgNPs using several biological sources and other chemical agents are presented and discussed. Toxicity in different animals is also presented and discussed. By considering the actual state of the art, it can be assumed that oral, intravenous and inhalation doses of AgNPs from 0.1 to 2 mg/Kg in mice and rats are considered a safe administration. In terms of ecotoxicity, it is more concerning since many of the in vivo assays showed a very low lethal dose, i.e., 50% (LD50). Therefore, we have to be very careful with the AgNPs residues in the environment.

Background: Photoluminescent materials have been used for diverse applications in the fields of science and engineering, such as optical storage, biological labeling, noninvasive imaging, solid-state lasers, light-emitting diodes, theranostics/theragnostics, up-conversion lasers, solar cells, spectrum modifiers, photodynamic therapy remote controllers, optical waveguide amplifiers and temperature sensors. Nanosized luminescent materials could be ideal candidates in these applications. Objective: This review is to present a brief overview of photoluminescent nanofibers obtained through electrospinning and their emission characteristics. Methods: To prepare bulk-scale nanosized materials efficiently and cost-effectively, electrospinning is a widely used technique. By the electrospinning method, a sufficiently high direct-current voltage is applied to a polymer solution or melt; and at a certain critical point when the electrostatic force overcomes the surface tension, the droplet is stretched to form nanofibers. Polymer solutions or melts with a high degree of molecular cohesion due to intermolecular interactions are the feedstock. Subsequent calcination in air or specific gas may be required to remove the organic elements to obtain the desired composition. Results: The luminescent nanofibers are classified based on the composition, structure, and synthesis material. The photoluminescent emission characteristics of the nanofibers reveal intriguing features such as polarized emission, energy transfer, fluorescent quenching, and sensing. An overview of the process, controlling parameters and techniques associated with electrospinning of organic, inorganic and composite nanofibers are discussed in detail. The scope and potential applications of these luminescent fibers also conversed. Conclusion: The electrospinning process is a matured technique to produce nanofibers on a large scale. Organic nanofibers have exhibited superior fluorescent emissions for waveguides, LEDs and lasing devices, and inorganic nanofibers for high-end sensors, scintillators, and catalysts. Multifunctionalities can be achieved for photovoltaics, sensing, drug delivery, magnetism, catalysis, and so on. The potential of these nanofibers can be extended but not limited to smart clothing, tissue engineering, energy harvesting, energy storage, communication, safe data storage, etc. and it is anticipated that in the near future, luminescent nanofibers will find many more applications in diverse scientific disciplines.

Background: Due to its high toxicity and bioaccumulation, the existence of mercury in the environment is always a big threat to human beings. In order to control mercury pollution, scientists have put great efforts in the past decades. Methods: Precipitation, adsorption, membrane separation, biological treatment and ion exchange are reviewed as a remover for mercury removal. For each material type, we not only reported on the removal mechanism, but also discussed the best areas for it. The correlation method and step-to-step focusing method have been used for references. Results: For better mercury removal, the ways above are compared together. The mechanisms of removing mercury in different ways are summarized in this paper. Conclusion: With the exploration and application of research, people have mastered a variety of mature technologies for the treatment of mercury-containing wastewater. Using inexpensive adsorbents is a cost-effective method for treating low concentrations of heavy metal wastewater. Ion exchange with a fast removal rate has been widely used in the field of heavy metal removal from wastewater. The biological treatment method can effectively treat low-concentration mercurycontaining wastewater. However, there is still a need to develop novel mercury removers with high capacity, fast removal rate, and low removal limit. Nanomaterials with a high specific surface area on substrate with synergistic effects, such as high adsorption and ion exchange, are the future research points.

Background: Biodiesel, as a green and renewable biofuel, has great potential to replace fossil diesel. The development of efficient and stable heterogeneous catalysts is vital to produce biodiesel in an efficient and green way. Nanocatalysts provide a high surface-to-volume ratio as well as high active site loading and can improve mass transfer, which is beneficial to enhance their catalytic activity. Objective: The review focuses on the latest advances in the production of biodiesel using nanostructured catalysts. Methods: Biodiesel is mainly produced through esterification and transesterification reaction using acids, bases or lipases as catalysts. We mainly review the synthesis methods and physicochemical properties of various basic, acidic and lipase nanocatalysts. Meanwhile, their catalytic activities in biodiesel production are also discussed. Results: Alkali nanocatalysts are mainly suitable for transformation of oils with low acid values to biodiesel via transesterification reaction. In contrast, acidic nanocatalysts are not sensitive to water as well as free fatty acids and can avoid saponification associated with basic nanocatalysts while promote simultaneous esterification and transesterification reaction. However, acid-catalyzed transesterification usually requires harsh reaction conditions. In addition, the lipase-catalyzed process is also suitable for non-edible oils containing high contents of free fatty acids, which possess environmental and economic advantages. Conclusion: Nanocatalysts have many advantages such as good accessibility with nanostructure, high active site loading and reduction of mass transfer resistance. However, most of those materials undergo deactivation after several cycles. Therefore, the development of more efficient, stable, and low-cost nanocatalysts is desirable for producing biodiesel.

Theranostics is a recently emerging area in nanomedicine. Nanoparticles which can combine both diagnostic and therapy in one single platform serve as theranostic agents. Some of the currently explored nanoparticles are metallic nanoparticles, mesoporous silica nanoparticles, carbonbased nanoparticles, and polymer nanogels. Polymeric nanogels are receiving considerable attention due to their high biocompatibility and functional performance. The present review article briefly summarizes the scopes and challenges of the state of art of using polymeric nanogels for theranostic applications. Among the different polymer nanogels, a special emphasis is given to polymeric nanogels with innate imaging potential.

This review provides an updated vision about the recent developments in the field of drug vectorization using functional nanoparticles and other nanovectors. From a large number of these nanotechnology-based drug delivery systems that emerge nearly every week, only a tiny fraction reaches a pre-clinical or clinical phase study. In this report, we intend to provide contextual information about those nanocarriers and release methods that have shown the best outcomes at in vitro and in vivo experiments, highlighting those with proven therapeutic efficiency in humans. From silicabased porous nanoparticles to liposomes or polymeric nanoparticles, each one of these nanosystems has its advantages and drawbacks. We describe and discuss briefly those approaches that, in our criterion, have provided significant advancements over existing therapies at the in vivo level. This work also provides a general view of those commercially available nanovectors and their specific area of therapeutic action.

Nanofiltration technology to remove possible pathogenic viruses during biopharmaceutical manufacturing was introduced in the biopharmaceutical industry in 1989. The very first industrial implementation took place in the early 1990s, through commercial manufacturing processes of plasma- derived medical products. Then it was applied to recombinant protein medical products, including monoclonal antibodies. In the first review published in 2005 in this journal, the technology was already considered promising and was much welcomed by the industry, but it was still a relatively emerging technology at that time, and many questions were raised about its robustness as a reliable virus-removal tool. We conducted a review to update the published information (SCI journals and suppliers’ documentation) existing on the use of nanofiltration as an industrial process for removing viruses from various biologicals. After almost a decade from the previous review, nanofiltration has established itself as a routine production step in most biopharmaceutical manufacturing. It has become one of the essential manufacturing processes used to assure safety against viral contamination. The technology is applied to manufacturing processes of various biologicals (human plasma products and complex recombinant proteins, such as coagulation factors and monoclonal antibodies made from mammalian cells). Many biologicals that undergo nanofiltration are licensed by regulatory authorities, which illustrates that nanofiltration is recognized as a robust and safe virus-removal method. No adverse events related to the use of nanofiltration have been recorded. New trends in nanofiltration technology continue to appear. As was identified during its introduction to the market and predicted in the previous review, nanofiltration has achieved major technical breakthroughs for ensuring the safety of biologicals, particularly human plasma-derived products, against viruses.

Background: Cancer is one of most dangerous diseases that seriously threaten human health, while tumor biomarkers provide important information for clinical diagnosis and treatment of cancers. Given the low abundance of tumor biomarkers in the bodily fluids at the early stage of cancers, it is particularly important to develop bio sensing methods for accurate measurement of tumor biomarkers with high sensitivity. Objective: Nowadays, gold nanoparticles (AuNPs) that have remarkable physical and chemical properties are extensively used in the design of biosensing strategies. In this context, we mainly review the research progress of AuNPs-based biosensing methods for tumor-related biomedical applications in bodily fluids in recent years. Results: Optical, electrochemical and mass spectrometric biosensing methods using AuNPs are widely used for excellent performances in the assay of tumor biomarkers. Conclusion: The existing methods demonstrate high clinical value, while challenges and expectation of biosensing method in tumor-related biomedical application are also discussed.

This paper emphasizes on overviewing the developing progress of the state-of-the-art carbon nanomaterial-based saturable absorbers for passively mode-locked fiber lasers, including carbon nanotube (CNT), graphene, graphite and other carbon nanomaterials. With reviewing the performances of these proposed candidates, the characteristic parameters required for initiating and stabilizing the passive mode-locked fiber lasers are summarized for comparison and discussion. At first, the basic characteristics such as saturation intensity and self-amplitude-modulation (SAM) coefficients of the CNT material with different-wall types are discussed in detail. In comparison, the single-wall CNT possesses optical nonlinearity better than double-wall CNT, whereas the doublewall CNT exhibits wavelength tenability and the multi-wall CNT fails to initiate mode-locking. Subsequently, different graphene saturable absorbers with slightly changing their optical properties made by various fabrication technologies are introduced to take over the role of typical CNT saturable absorber. The detailed analyses on graphene saturable absorber for developing various types of passively mode-locked fiber lasers are overviewed. At last, other new-aspect graphite and carbon nanomaterials related saturable absorbers have emerged because they reveal similar optical nonlinearity with graphene but exhibit cost-effectiveness and easy-production. When changing saturable absorber from graphene to other carbon nanomaterials, the modulation depth is decreased but the saturation intensity is concurrently enlarged because of the disordered structure with increased interlayer spacing and reduced graphene content. At the current stage, selecting carbon nanomaterials with high nonlinear absorbance and low saturated intensity for large SAM coefficient is the golden rule for passively mode-locked the fiber lasers in future academic and industrial applications.