Multifunctional gold nanoparticles for osteoporosis: synthesis, mechanism and therapeutic applications

Osteoporosis is currently the most prevalent bone disorder worldwide and is characterized by low bone mineral density and an overall increased risk of fractures. To treat osteoporosis, a range of drugs targeting bone homeostasis have emerged in clinical practice, including anti-osteoclast agents such as bisphosphonates and denosumab, bone formation stimulating agents such as teriparatide, and selective oestrogen receptor modulators. However, traditional clinical medicine still faces challenges related to side effects and high costs of these types of treatments. Nanomaterials (particularly gold nanoparticles [AuNPs]), which have unique optical properties and excellent biocompatibility, have gained attention in the field of osteoporosis research. AuNPs have been found to promote osteoblast differentiation, inhibit osteoclast formation, and block the differentiation of adipose-derived stem cells, which thus is believed to be a novel and promising candidate for osteoporosis treatment. This review summarizes the advances and drawbacks of AuNPs in their synthesis and the mechanisms in bone formation and resorption in vitro and in vivo, with a focus on their size, shape, and chemical composition as relevant parameters for the treatment of osteoporosis. Additionally, several important and promising directions for future studies are also discussed, which is of great significance for prevention and treatment of osteoporosis.

L-Cysteine modified gold nanoparticles for tube-based fluorometric determination of mercury(II) ions

A fluorescent probe is described for detection of mercury(II) ion by using L-cysteine-modified gold nanoparticles (Cys-AuNP). These were fabricated by a tube-based redox reaction where Cys acts as both the reducing reagent and capping ligand. The Cys-AuNP display red fluorescence, with excitation/emission peaks at 373/625 nm. Owing to the high-affinity of the Hg(II)-Au(I) interaction and the Hg(II)/carboxy or amino group interaction, the presence of Hg(II) cause selective quenching the fluorescence, while other metal ions do not give such an effect. Based on these findings, a method was designed for the determination of Hg(II) that has attractive figures of merit. These include a low limit of detection (1.3 nM), a wide detection range (from 2 nM to 30µM), and excellent specificity. The method was applied to Hg(II) screening in (spiked) tap and river water, and it gave satisfactory results. Graphical abstract Schematic representation of the application of L-cysteine modified gold nanoparticles (Cys-AuNP) for qualitative and quantitative detection of mercury(II) ions. Based on the interaction between Cys-AuNP and mercury(II) ion to quench the red fluorescence of Cys-AuNP, the target mercury(II) can in turn be determined by a fluorometric method.

Particle release and control of worker exposure during laboratory-scale synthesis, handling and simulated spills of manufactured nanomaterials in fume hoods

Fume hoods are one of the most common types of equipment applied to reduce the potential of particle exposure in laboratory environments. A number of previous studies have shown particle release during work with nanomaterials under fume hoods. Here, we assessed laboratory workers' inhalation exposure during synthesis and handling of CuO, TiO₂ and ZnO in a fume hood. In addition, we tested the capacity of a fume hood to prevent particle release to laboratory air during simulated spillage of different powders (silica fume, zirconia TZ-3Y and TiO₂). Airborne particle concentrations were measured in near field, far field, and in the breathing zone of the worker. Handling CuO nanoparticles increased the concentration of small particles (< 58 nm) inside the fume hood (up to 1 × 10⁵ cm^-3). Synthesis, handling and packaging of ZnO and TiO₂ nanoparticles did not result in detectable particle release to the laboratory air. Simulated powder spills showed a systematic increase in the particle concentrations inside the fume hood with increasing amount of material and drop height. Despite powder spills were sometimes observed to eject into the laboratory room, the spill events were rarely associated with notable release of particles from the fume hood. Overall, this study shows that a fume hood generally offers sufficient exposure control during synthesis and handling of nanomaterials. An appropriate fume hood with adequate sash height and face velocity prevents 98.3% of particles release into the surrounding environment. Care should still be made to consider spills and high cleanliness to prevent exposure via resuspension and inadvertent exposure by secondary routes.

Ionic liquids for nano- and microstructures preparation. Part 1: Properties and multifunctional role

Ionic liquids (ILs) are a broad group of organic salts of varying structure and properties, used in energy conversion and storage, chemical analysis, separation processes, as well as in the preparation of particles in nano- and microscale. In material engineering, ionic liquids are applied to synthesize mainly metal nanoparticles and 3D semiconductor microparticles. They could generally serve as a structuring agent or as a reaction medium (solvent). This review deals with the resent progress in general understanding of the ILs role in particle growth and stabilization and the application of ionic liquids for nano- and microparticles synthesis. The first part of the paper is focused on the interactions between ionic liquids and growing particles. The stabilization of growing particles by steric hindrance, electrostatic interaction, solvation forces, viscous stabilization, and ability of ILs to serve as a soft template is detailed discussed. For the first time, the miscellaneous role of the ILs in nano- and microparticle preparation composed of metals as well as semiconductors is collected, and the formation mechanisms are graphically presented and discussed based on their structure and selected properties. The second part of the paper gives a comprehensive overview of recent experimental studies dealing with the applications of ionic liquids for preparation of metal and semiconductor-based nano- and microparticles. A wide spectrum of preparation routes using ionic liquids are presented, including precipitation, sol-gel technique, hydrothermal method, nanocasting, and microwave or ultrasound-mediated methods.

Sonochemistry: Science and Engineering

Sonochemistry offers a simple route to nanomaterial synthesis with the application of ultrasound. The tiny acoustic bubbles, produced by the propagating sound wave, enclose an incredible facility where matter interact among at energy as high as 13 eV to spark extraordinary chemical reactions. Within each period - formation, growth and collapse of bubbles, lies a coherent phase of material formation. This effective yet highly localized method has facilitated synthesis of various chemical and biological compounds featuring unique morphology and intrinsic property. The benign processing lends to synthesis without any discrimination towards a certain group of material, or the substrates where they are grown. As a result, new and improved applications have evolved to reach out various field of science and technology and helped engineer new and better devices. Along with the facile processing and notes on the essence of sonochemistry, in this comprehensive review, we discuss the individual and mutual effect of important input parameters on the nanomaterial synthesis process as a start to help understand the underlying mechanism. Secondly, an objective discussion of the diversely synthesized nanomaterial follows to divulge the easiness imparted by sonochemistry, which finally blends into the discussion of their applications and outreach.

Ionic liquids for nano- and microstructures preparation. Part 2: Application in synthesis

Ionic liquids (ILs) are widely applied to prepare metal nanoparticles and 3D semiconductor microparticles. Generally, they serve as a structuring agent or reaction medium (solvent), however it was also demonstrated that ILs can play a role of a co-solvent, metal precursor, reducing as well as surface modifying agent. The crucial role and possible types of interactions between ILs and growing particles have been presented in the Part 1 of this review paper. Part 2 of the paper gives a comprehensive overview of recent experimental studies dealing with application of ionic liquids for preparation of metal and semiconductor based nano- and microparticles. A wide spectrum of preparation routes using ionic liquids is presented, including precipitation, sol-gel technique, hydrothermal method, nanocasting and ray-mediated methods (microwave, ultrasound, UV-radiation and γ-radiation). It was found that ionic liquids formed of a 1-butyl-3-methylimidazolium [BMIM] combined with tetrafluoroborate [BF4], hexafluorophosphate [PF6], and bis(trifluoromethanesulfonyl)imide [Tf2N] are the most often used ILs in the synthesis of nano- and microparticles, due to their low melting temperature, low viscosity and good transportation properties. Nevertheless, examples of other IL classes with intrinsic nanoparticles stabilizing abilities such as phosphonium and ammonium derivatives are also presented. Experimental data revealed that structure of ILs (both anion and cation type) affects the size and shape of formed metal particles, and in some cases may even determine possibility of particles formation. The nature of the metal precursor determines its affinity to polar or nonpolar domains of ionic liquid, and therefore, the size of the nanoparticles depends on the size of these regions. Ability of ionic liquids to form varied extended interactions with particle precursor as well as other compounds presented in the reaction media (water, organic solvents etc.) provides nano- and microstructures with different morphologies (0D nanoparticles, 1D nanowires, rods, 2D layers, sheets, and 3D features of molecules). ILs interact efficiently with microwave irradiation, thus even small amount of IL can be employed to increase the dielectric constant of nonpolar solvents used in the synthesis. Thus, combining the advantages of ionic liquids and ray-mediated methods resulted in the development of new ionic liquid-assisted synthesis routes. One of the recently proposed approaches of semiconductor particles preparation is based on the adsorption of semiconductor precursor molecules at the surface of micelles built of ionic liquid molecules playing a role of a soft template for growing microparticles.

Release of phosphorous impurity from TiO2 anatase and rutile nanoparticles in aquatic environments and its implications

Phosphorus-bearing materials as an additive have been popularly used in nanomaterial synthesis and the residual phosphorus within the nanoparticles (NPs) can be of an environmental concern. For instance, phosphorus within pristine commercial TiO2 NPs greatly influences the surface charge and aggregation behavior of the host TiO2 in aquatic environments; however, it is unknown whether and how fast phosphorus is released. In this study, we focus on the phosphorus release kinetics from five types of TiO2 NPs (i.e., 5, 10, and 50 nm anatase and 10 × 40, 30 × 40 nm rutile) under the influence of varying solution chemistries. The 50 nm anatase has the highest quantity of P (8.05 g/kg) and most leachable P dissolves within the first 2 h (i.e., 5.01 g/kg), which presents a potential pollutant source of P. Higher pH favors the phosphorus release (release order: pH 11.2 > pH 8.2 > pH 2.4), while variations in the environmentally relevant ionic strengths (0.01 M NaCl + 0.01 M NaHCO3 and 0.04 M NaCl + 0.01 M NaHCO3) and the presence of dissolved natural organic matter (10 mg/L) do not affect release rate greatly. X-ray Absorption Near Edge Structure results suggest that phosphate adsorbed on the pristine 50 nm anatase desorbs, and some dissolved phosphate again re-sorbs as a surface precipitate. The findings from this research may have important environmental implications such as accidental release of TiO2 NPs and other nanomaterials that are synthesized using phosphorus containing chemicals as an ingredient.