Abstract Nanostructured silicon carbide (SiC) is an exceptional material with numerous applications, for example, in catalysis, biomedicine, high‐performance composites, and sensing. In this study, a fast and scalable method of producing nanostructured SiC from plant materials by magnesiothermic reduction via self‐propagating high‐temperature synthesis (SHS) route was developed. The produced biogenic material possessed a high surface area above 200 m 2 /g with a SiC crystallite size below 10 nm, which has not been done previously by SHS. This method enables affordable synthesis of the material plant‐based precursors in a reaction that only takes a few seconds, thereby paving a way for nanostructured SiC production in high volumes using renewable resources. The material was also functionalized with carboxylic acid and bisphosphonate moieties, and its use as metal adsorbent in applications such as wastewater remediation was demonstrated.
Anthropogenic activities such as mining and ore beneficiation generate large amounts of uranium-contaminated wastewater. The metal is radioactive and toxic; therefore, it needs to be removed to protect the environment and human health. Adsorption is a viable method to remove uranium from wastewater because of the low energy consumption and ability to remove even low concentrations of uranium. However, most adsorbents are not effective to selectively adsorb uranium and their stability is typically degraded in repeated adsorption/desorption cycles. Herein, we employed a novel nanostructured adsorbent to selectively remove uranium from a tailing obtained from processing of real ore sample by Knelson concentration method. The adsorbent consisted of bisphosphonate ligands grafted on highly stable carbonized surfaces of mesoporous silicon. The porous structure of the adsorbent enhanced its permeability allowing it to be used in a column setup where metal solutions were flown through the adsorbent. The adsorbent was capable of repeatedly adsorbing and desorbing uranium without significant reduction in the performance. Importantly, the adsorbent showed essentially higher selectivity towards uranium than towards other less harmful metal ions, and the material could be regenerated with an acid. Desorption was carried out with sulfuric acid resulting in 15-fold enrichment of uranium compared to the initial solution, while other metals did not concentrate efficiently. The adsorbent was capable of selectively capturing uranium from a solution with various other metals and the adsorbed uranium was rapidly desorbed and quantified with a reasonable purity, indicating the adsorbent as a potential candidate for industrial applications.
Complex experimental design is a common problem in the preparation of theranostic nanoparticles, resulting in poor reaction control, expensive production cost, and low experiment success rate. The present study aims to develop PEGylated bismuth (PEG-Bi) nanoparticles with a precisely controlled one-pot approach, which contains only methoxy[(poly(ethylene glycol)]trimethoxy-silane (PEG-silane) and bismuth oxide (Bi2O3). A targeted pyrolysis of PEG-silane was achieved to realize its roles as both the reduction and PEGylation agents. The unwanted methoxy groups of PEG-silane were selectively pyrolyzed to form reductive agents, while the useful PEG-chain was fully preserved to enhance the biocompatibility of Bi nanoparticles. Moreover, Bi2O3 not only acted as the raw material of the Bi source but also presented a self-promotion in the production of Bi nanoparticles via catalyzing the pyrolysis of PEG-silane. The reaction mechanism was systematically validated with different methods such as nuclear magnetic resonance spectroscopy. The PEG-Bi nanoparticles showed better compatibility and photothermal conversion than those prepared by the complex multiple step approaches in literature studies. In addition, the PEG-Bi nanoparticles possessed prominent performance in X-ray computed tomography imaging and photothermal cancer therapy in vivo. The present study highlights the art of precise reaction control in the synthesis of PEGylated nanoparticles for biomedical applications.
Visceral leishmaniasis is a vector-borne protozoan infection that is fatal if untreated. There is no vaccination against the disease, and the current chemotherapeutic agents are ineffective due to increased resistance and severe side effects. Buparvaquone is a potential drug against the leishmaniases, but it is highly hydrophobic resulting in poor bioavailability and low therapeutic efficacy. Herein, we loaded the drug into silicon nanoparticles produced from barley husk, which is an agricultural residue and widely available. The buparvaquone-loaded nanoparticles were several times more selective to kill the intracellular parasites being non-toxic to macrophages compared to the pure buparvaquone and other conventionally used anti-leishmanial agents. Furthermore, the in vivo results revealed that the intraperitoneally injected buparvaquone-loaded nanoparticles suppressed the parasite burden close to 100%. By contrast, pure buparvaquone suppressed the burden only by 50% with corresponding doses. As the conclusion, the biogenic silicon nanoparticles are promising carriers to significantly improve the therapeutic efficacy and selectivity of buparvaquone against resistant visceral leishmaniasis opening a new avenue for low-cost treatment against this neglected tropical disease threatening especially the poor people in developing nations.
Production of scandium (Sc) is a complicated process largely because the Sc concentration in ores is typically low in comparison to other types of metals. Therefore, typical extraction processes, such as solvent extraction and precipitation, that are used for separation and purification of leach liquors are inefficient. Adsorption/desorption is a good alternative method for extraction, but it is challenging to prepare affordable adsorbents with high stability, good selectivity, and high adsorption capacity. Most Sc sources are currently unexploited, and new, efficient, and environmentally sustainable methods for Sc extraction are needed. In the present study, bisphosphonates (BPs) immobilized on the surface of nanoporous silicon were used as metal ion chelators. Thermal carbonization was used to passivate the porous silicon surfaces with silicon carbide, on which the BP molecules were grafted. The BP grafted thermally carbonized porous silicon (BP-TCPSi) was used to extract Sc from a leach solution of Sc ore obtained from Rautalampi, Finland. First, Sc was leached from the ore using sulfuric acid. An oxidative precipitation method was employed to reduce the concentrations of the interfering metal ions; this treatment decreased the Fe, Ti, Al, and Mn concentrations by 99 ± 2%, 100 ± 14%, 35 ± 1%, and 76 ± 2%, respectively, while only 12 ± 1% of Sc was lost. The selectivity of BP-TCPSi was studied in a flow-through setup to adsorb Sc from the treated leach solution; then, in a two-step desorption process, Sc was separated from the other metal ions with a separation factor of 440 ± 13. The reusability of BP-TCPSi was examined in a flow-through setup with 10 adsorption/desorption cycles using a treated leach solution showing good stability of the adsorbent. The developed method provides a fast and convenient way to extract, purify, and enrich Sc with total recovery of 69 ± 1% in one cycle of adsorption/desorption of Sc from the leach solution with a low Sc concentration and a relatively high concentration of the other metal ions.
In spite of the advances in drug delivery, the preparation of smart nanocomposites capable of precisely controlled release of multiple drugs for sequential combination therapy is still challenging. Here, a novel drug delivery nanocomposite was prepared by coating porous silicon (PSi) nanoparticles with poly(beta-amino ester) (PAE) and Pluronic F-127, respectively. Two anticancer drugs, doxorubicin (DOX) and paclitaxel (PTX), were separately loaded into the core of PSi and the shell of F127. The nanocomposite displayed enhanced colloidal stability and good cytocompatibility. Moreover, a spatiotemporal drug release was achieved for sequential combination therapy by precisely controlling the release kinetics of the two tested drugs. The release of PTX and DOX occurred in a time-staggered manner; PTX was released much faster and earlier than DOX at pH 7.0. The grafted PAE on the external surface of PSi acted as a pH-responsive nanovalve for the site-specific release of DOX. In vitro cytotoxicity tests demonstrated that the DOX and PTX coloaded nanoparticles exhibited a better synergistic effect than the free drugs in inducing cellular apoptosis. Therefore, the present study demonstrates a promising strategy to enhance the efficiency of combination cancer therapies by precisely controlling the release kinetics of different drugs.
