'Passivated Precursor' Approach to All-Alkynyl-Protected Gold Nanoclusters and Total Structure Determination of Au130.

A 'passivated precursor' approach is developed for the efficient synthesis and isolation of all-alkynyl-protected gold nanoclusters. Direct reduction of dpa-passivated precursor Au-dpa (Hdpa=2,2'-dipyridylamine) in one-pot under ambient conditions gives a series of clusters including Au22(C≡CR)18 (R=-C6H4-2-F), Au36(C≡CR)24, Au44(C≡CR)28, Au130(C≡CR)50, and Au144(C≡CR)60. These clusters can be well separated via column chromatography. The overall isolation yield of this series of clusters is 40 % (based on gold), which is much improved in comparison with previous approaches. It is notable that the molecular structure of the giant cluster Au130(C≡CR)50 is revealed, which presents important information for understanding the structure of the mysterious Au130 nanoclusters. Theoretical calculations indicated Au130(C≡CR)50 has a smaller HOMO-LUMO gap than Au130(S-C6H4-4-CH3)50. This facile and reliable synthetic approach will greatly accelerate further studies on all-alkynyl-protected gold nanoclusters.

Functionalization of Siloxanes with Arynes Generated from o-Triazenylarylboronic Acids.

Herein, we report the functionalization of polyhedral oligosilsesquioxanes (POSS) and related siloxanes with arynes. Using o-triazenylarylboronic acids as aryne precursors and silica gel as the activator, the transformation of siloxane bearing various arynophilic moieties on the side chains was achieved with high yields without touching the siloxane core. This method was applied to the conjugation of POSS and pharmaceutical cores using an aryne derived from the synthetic intermediate of cabozantinib. Furthermore, orthogonal dual functionalization of POSS was realized by combining the aryne reaction with Huisgen cyclization.

Green synthesis of N-rich carbon dot-derived crosslinked covalent organic nanomaterial for multipurpose chromatographic applications.

Carbon dots (CDs) derived crosslinked covalent organic nanomaterials (CONs) possessing high specific surface area and abundant surface functional groups are considered to be potential candidates for multimodal chromatographic separations. Typically, the synthesis of CDs and CONs requires harsh reaction conditions and toxic organic solvents, hence, the pursuit of facile and mild preparation strategies is the goal of researchers. In this work, 3-aminopropyltriethoxysilane and D-glucose were used as nitrogen and carbon sources, respectively, to prepare amino-CDs (AmCDs) by rapid low-temperature polymerization rather than the common high-temperature and high-pressure reaction. Then, surface functionalization of the aminated silica gel was carried out in a deep eutectic solvent by using hydrophilic AmCDs and 1,3,5-triformylbenzene (TFB) as the functional monomers. Consequently, a novel N-rich CDs derived CON surface-functionalized silica gel (AmCDs-CON@SiO2) was obtained under mild reaction conditions. The combination of AmCDs and TFB created an ideal CON based chromatographic stationary phase. The incorporation of TFB not only contributed to the successful construction of a crosslinked CON, but also enhanced the interaction forces. The developed AmCDs-CON@SiO2 has a great potential for versatile applications in liquid chromatography. This study proposes a simple stationary phase preparation strategy by the surface modification of silica gel with CDs-based CON. Moreover, this study verified the application potential of CDs derived CON in chromatographic separation. This not only promotes the development of CDs in the field of liquid chromatographic stationary phase, but also provides some reference value for the wide application of cross-linked CON.

Establishment of Polydopamine-Modified HK-2 Cell Membrane Chromatography and Screening of Active Components from Plantago asiatica L.

Cell membrane chromatography (CMC) has been widely recognized as a highly efficient technique for in vitro screening of active compounds. Nevertheless, conventional CMC approaches suffer from a restricted repertoire of cell membrane proteins, making them susceptible to oversaturation. Moreover, the binding mechanism between silica gel and proteins primarily relies on intermolecular hydrogen bonding, which is inherently unstable and somewhat hampers the advancement of CMC. Consequently, this investigation aimed to establish a novel CMC column that could augment protein loading, enhance detection throughput, and bolster binding affinity through the introduction of covalent bonding with proteins. This study utilizes polydopamine (PDA)-coated silica gel, which is formed through the self-polymerization of dopamine (DA), as the carrier for the CMC column filler. The objective is to construct the HK-2/SiO2-PDA/CMC model to screen potential therapeutic drugs for gout. To compare the quantity and characteristics of Human Kidney-2 (HK-2) cell membrane proteins immobilized on SiO2-PDA and silica gel, the proteins were immobilized on both surfaces. The results indicate that SiO2-PDA has a notably greater affinity for membrane proteins compared to silica gel, resulting in a significant improvement in detection efficiency. Furthermore, a screening method utilizing HK-2/SiO2-PDA/CMC was utilized to identify seven potential anti-gout compounds derived from Plantago asiatica L. (PAL). The effectiveness of these compounds was further validated using an in vitro cell model of uric acid (UA) reabsorption. In conclusion, this study successfully developed and implemented a novel CMC filler, which has practical implications in the field.

Apolar Extracts of St. John's Wort Alleviate the Effects of ß-Amyloid Toxicity in Early Alzheimer's Disease.

Hypericum perforatum (St. John's wort) has been described to be beneficial for the treatment of Alzheimer's disease (AD). Different extractions have demonstrated efficiency in mice and humans, esp. extracts with a low hypericin and hyperforin content to reduce side effects such as phototoxicity. In order to systematically elucidate the therapeutic effects of H. perforatum extracts with different polarities, APP-transgenic mice were treated with a total ethanol extract (TE), a polar extract obtained from TE, and an apolar supercritical CO2 (scCO2) extract. The scCO2 extract was formulated with silicon dioxide (SiO2) for better oral application. APP-transgenic mice were treated with several extracts (total, polar, apolar) at different concentrations. We established an early treatment paradigm from the age of 40 days until the age of 80 days, starting before the onset of cerebral ß-amyloid (Aß) deposition at 45 days of age. Their effects on intracerebral soluble and insoluble Aß were analyzed using biochemical analyses. Our study confirms that the scCO2H. perforatum formulation shows better biological activity against Aß-related pathological effects than the TE or polar extracts. Clinically, the treatment resulted in a dose-dependent improvement in food intake with augmentation of the body weight, and, biochemically, it resulted in a significant reduction in both soluble and insoluble Aß (-27% and -25%, respectively). We therefore recommend apolar H. perforatum extracts for the early oral treatment of patients with mild cognitive impairment or early AD.

Toward "CO in a Pill": Silica-Immobilized Organic CO Prodrugs for Studying the Feasibility of Systemic Delivery of CO via In Situ Gastrointestinal CO Release.

Carbon monoxide (CO), an endogenous signaling molecule, is known to exert a range of pharmacological effects, including anti-inflammation, organ protection, and antimetastasis in various animal models. We have previously shown the ability of organic prodrugs to deliver CO systemically through oral administration. As part of our efforts for the further development of these prodrugs, we are interested in minimizing the potential negative impact of the "carrier" portion of the prodrug. Along this line, we have previously published our work on using benign "carriers" and physically trapping the "carrier" portion in the gastrointestinal (GI) tract. We herein report our feasibility studies on using immobilized organic CO prodrugs for oral CO delivery while minimizing systemic exposure to the prodrug and the "carrier portion." In doing so, we immobilize a CO prodrug to silica microparticles, which are generally recognized as safe by the US FDA and known to provide large surface areas for loading and water accessibility. The latter point is essential for the hydrophobicity-driven activation of the CO prodrug. Amidation-based conjugation with silica is shown to provide 0.2 mmol/g loading degree, effective prodrug activation in buffer with comparable kinetics as the parent prodrug, and stable tethering to prevent detachment. One representative silica conjugate, SICO-101, is shown to exhibit anti-inflammation activity in LPS-challenged RAW264.7 cells and to deliver CO systemically in mice through oral administration and GI CO release. We envision this strategy as a general approach for oral CO delivery to treat systemic and GI-specific inflammatory conditions.

High-throughput microfluidic chip with silica gel-C18 channels for cyclotide separation.

Over the past two decades, microfluidic-based separations have been used for the purification, isolation, and separation of biomolecules to overcome difficulties encountered by conventional chromatography-based methods including high cost, long processing times, sample volumes, and low separation efficiency. Cyclotides, or cyclic peptides used by some plant families as defense agents, have attracted the interest of scientists because of their biological activities varying from antimicrobial to anticancer properties. The separation process has a critical impact in terms of obtaining pure cyclotides for drug development strategies. Here, for the first time, a mimic of the high-performance liquid chromatography (HPLC) on microfluidic chip strategy was used to separate the cyclotides. In this regard, silica gel-C18 was synthesized and characterized by Fourier-transform infrared spectroscopy (FTIR) and proton nuclear magnetic resonance (1H-NMR) and then filled inside the microchannel to prepare an HPLC C18 column-like structure inside the microchannel. Cyclotide extract was obtained from Viola ignobilis by a low voltage electric field extraction method and characterized by HPLC and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). The extract that contained vigno 1, 2, 3, 4, 5, and varv A cyclotides was added to the microchannel where distilled water was used as a mobile phase with 1 µL/min flow rate and then samples were collected in 2-min intervals until 10 min. Results show that cyclotides can be successfully separated from each other and collected from the microchannel at different periods of time. These findings demonstrate that the use of microfluidic channels has a high impact on the separation of cyclotides as a rapid, cost-effective, and simple method and the device can find widespread applications in drug discovery research.

Novel strategies for extraction, purification, processing, and stability improvement of bioactive molecules.

Bioactive molecules gain significance in pharmaceutical and nutraceutical industries for showcasing various beneficial biological properties including but not limited to anticancer, antimicrobial, antioxidant, antifungal, anti-inflammatory, cardioprotective, neuroprotective, and antidiabetic. However, the practice of using traditional approaches to produce bioactive molecules is gradually declining due to various limitations such as low product quality, high toxicity, low product yield, low efficiency, and product degradation. Thus, with the escalating demand for these bioactive molecules and active agents in food and other food-related industries, it has become a dire need for the scientific world to come up with novel approaches and strategies that cannot just improve the quality of these bioactives but also prepare them in a comparatively shorter time span. This review includes the latest approaches and techniques used either independently or in combinations for the extraction, purification, processing, and stability improvement of general bioactive molecules. Different parameters of these versatile techniques have been discussed with their effectiveness and work principles.

Separation and Purification of Hydroxyl-α-Sanshool from Zanthoxylum armatum DC. by Silica Gel Column Chromatography.

Hydroxyl-α-sanshool is the main alkylamide produced by Zanthoxylum armatum DC., and it is responsible for numbness after consuming Z. armatum-flavored dishes or food products. The present study deals with the isolation, enrichment, and purification of hydroxyl-α-sanshool. The results indicated that the powder of Z. armatum was extracted with 70% ethanol and then filtrated; the supernatant was concentrated to get pasty residue. Petroleum ether (60-90 °C) and ethyl acetate at a 3:2 ratio, with an Rf value of 0.23, were chosen as the eluent. Petroleum ether extract (PEE) and ethyl acetate-petroleum ether extract (E-PEE) were used as the suitable enriched method. Afterward, the PEE and E-PEE were loaded onto silica gel for silica gel column chromatography. Preliminary identification was carried out by TLC and UV. The fractions containing mainly hydroxyl-α-sanshool were pooled and dried by rotary evaporation. Lastly, all of the samples were determined by HPLC. The yield and recovery rates of hydroxyl-α-sanshool in the p-E-PEE were 12.42% and 121.65%, respectively, and the purity was 98.34%. Additionally, compared with E-PEE, the purity of hydroxyl-α-sanshool in the purification of E-PEE (p-E-PEE) increased by 88.30%. In summary, this study provides a simple, rapid, economical, and effective approach to the separation of high-purity hydroxyl-α-sanshool.

Nanoparticle-Imprinted Silica Gel for the Size-Selective Capture of Silver Ultrafine Nanoparticles from Water.

A synthetic approach has been developed to prepare silica gel monoliths that embed well separated silver or gold spherical nanoparticles (NP), with diameters of 8, 18 and 115 nm. Fe3+, O2/cysteine and HNO3 were all successfully used to oxidize and remove silver NP from silica, while aqua regia was necessary for gold NP. In all cases, NP-imprinted silica gel materials were obtained, with spherical voids of the same dimensions of the dissolved particles. By grinding the monoliths, we prepared NP-imprinted silica powders that were able to efficiently reuptake silver ultrafine NP (Ag-ufNP, d = 8 nm) from aqueous solutions. Moreover, the NP-imprinted silica powders showed a remarkable size selectivity, based on the best match between NP radius and the curvature radius of the cavities, driven by the optimization of attractive Van der Waals forces between SiO2 and NP. Ag-ufNP are increasingly used in products, goods, medical devices, disinfectants, and their consequent diffusion in the environment is of rising concern. Although limited here to a proof-of-concept level, the materials and methods described in this paper may be an efficient solution for capturing Ag-ufNP from environmental waters and to safely dispose them.

Mechanochemical Synthesis of PdO2 Nanoparticles Immobilized over Silica Gel for Catalytic Suzuki-Miyaura Cross-Coupling Reactions Leading to the C-3 Modification of 1H-Indazole with Phenylboronic Acids.

The C-3 modification of 1H-indazole has produced active pharmaceuticals for the treatment of cancer and HIV. But, so far, this transformation has seemed less available, due to the lack of efficient C-C bond formation at the less reactive C-3 position. In this work, a series of silica gel-supported PdO2 nanoparticles of 25-66 nm size were prepared by ball milling silica gel with divalent palladium precursors, and then employed as catalysts for the Suzuki-Miyaura cross-coupling of 1H-indazole derivative with phenylboronic acid. All the synthesized catalysts showed much higher cross-coupling yields than their palladium precursors, and could also be reused three times without losing high activity and selectivity in a toluene/water/ethanol mixed solvent. Although the palladium precursors showed an order of activity of PdCl2(dppf, 1,1'-bis(diphenylphosphino)ferrocene) > PdCl2(dtbpf, 1,1'-bis(di-tert-butylphosphino)ferrocene) > Pd(OAc, acetate)2, the synthesized catalysts showed an order of C1 (from Pd(OAc)2) > C3 (from PdCl2(dtbpf)) > C2 (from PdCl2(dppf)), which conformed to the orders of BET (Brunauer-Emmett-Teller) surface areas and acidities of these catalysts. Notably, the most inexpensive Pd(OAc)2 can be used as a palladium precursor for the synthesis of the best catalyst through simple ball milling. This work provides a highly active and inexpensive series of catalysts for C-3 modification of 1H-indazole, which are significant for the large-scale production of 1H-indazole-based pharmaceuticals.

A phylotranscriptome study using silica gel-dried leaf tissues produces an updated robust phylogeny of Ranunculaceae.

The utility of transcriptome data in plant phylogenetics has gained popularity in recent years. However, because RNA degrades much more easily than DNA, the logistics of obtaining fresh tissues has become a major limiting factor for widely applying this method. Here, we used Ranunculaceae to test whether silica-dried plant tissues could be used for RNA extraction and subsequent phylogenomic studies. We sequenced 27 transcriptomes, 21 from silica gel-dried (SD-samples) and six from liquid nitrogen-preserved (LN-samples) leaf tissues, and downloaded 27 additional transcriptomes from GenBank. Our results showed that although the LN-samples produced slightly better reads than the SD-samples, there were no significant differences in RNA quality and quantity, assembled contig lengths and numbers, and BUSCO comparisons between two treatments. Using these data, we conducted phylogenomic analyses, including concatenated- and coalescent-based phylogenetic reconstruction, molecular dating, coalescent simulation, phylogenetic network estimation, and whole genome duplication (WGD) inference. The resulting phylogeny was consistent with previous studies with higher resolution and statistical support. The 11 core Ranunculaceae tribes grouped into two chromosome type clades (T- and R-types), with high support. Discordance among gene trees is likely due to hybridization and introgression, ancient genetic polymorphism and incomplete lineage sorting. Our results strongly support one ancient hybridization event within the R-type clade and three WGD events in Ranunculales. Evolution of the three Ranunculaceae chromosome types is likely not directly related to WGD events. By clearly resolving the Ranunculaceae phylogeny, we demonstrated that SD-samples can be used for RNA-seq and phylotranscriptomic studies of angiosperms.

Silica gel impregnated with deep eutectic solvent-based matrix solid-phase dispersion followed by high-performance liquid chromatography for extraction and detection of triazine herbicides in brown sugar.

A novel method was developed to determine six triazine herbicides from brown sugar samples using matrix solid-phase dispersion (MSPD) based on silica gel impregnated with deep eutectic solvent (DES) followed by high-performance liquid chromatography with photodiode array detector (HPLC/PDA). Several factors involved in the MSPD procedure such as DES type, DES content in impregnated silica gel, adsorbent-to-sample mass ratio, type and volume of washing solvent, type and volume of eluent, and grinding time were screened using single-factor experiments and then optimized using Box-Behnken design to accomplish the highest recoveries. The above method demonstrated a good linear range (20-1000 µg kg-1) with a determination coefficient exceeding 0.9962, low limits of determination (1.59-3.77 µg kg-1), acceptable limits of quantifications, and acceptable spiking recoveries (95.0-101.7%) for six triazines under optimized conditions. The proposed MSPD-HPLC/PDA method is a convenient, effective, and sensitive method for rapidly isolating and quantifying six triazines from brown sugar.

Immobilized Sulfuric Acid on Silica Gel as Highly Efficient and Heterogeneous Catalyst for the One-Pot Synthesis of Novel α-Acyloxycarboxamides in Aqueous Media.

The application of immobilized sulfuric acid on silica gel (H2SO4-SiO2) as an efficient and easily reusable solid catalyst was explored in the synthesis of novel α-acyloxycarboxamide derivatives via a Passerini reaction of benzoic acid, aldehyde/ketone, and isocyanides. The Passerini adducts were obtained in high to excellent yields within 10 min in aqueous media under catalytic conditions. The key advantages of the process include a short reaction time, high yields, the catalyst's low cost, and the catalyst's reusability.

Catalytic Performance of Immobilized Sulfuric Acid on Silica Gel for N-Formylation of Amines with Triethyl Orthoformate.

In the search for convenient, green, and practical catalytic methods for the current interest in organic synthesis, a simple, green, and highly efficient protocol for N-formylation of various amines was carried out in the presence of immobilized sulfuric acid on silica gel (H2SO4-SiO2). All reactions were performed in refluxing triethyl orthoformate (65 °C). The product formamides were obtained with high-to-excellent yields within 4 min to 2 h. The current approach is advantageous, due to its short reaction time and high yields. The catalyst is recyclable with no significant loss in catalytic efficiency.

Manipulating Reaction Energy Coordinate Landscape of Mechanochemical Diaza-Cope Rearrangement.

Chiral vicinal diamines, a unique class of optically-active building blocks, play a crucial role in material design, pharmaceutical, and catalysis. Traditionally, their syntheses are all solvent-based approaches, which make organic solvent an indispensable part of their production. As part of our program aiming to develop chemical processes with reduced carbon footprints, we recently reported a highly practical and environmentally-friendly synthetic route to chiral vicinal diamines by solvent-free mechanochemical diaza-Cope rearrangement. We herein showed that a new protocol by co-milling with common laboratory solid additives, such as silica gel, can significantly enhance the efficiency of the reaction, compared to reactions in the absence of additives. One possible explanation is the Lewis acidic nature of additives that accelerates a key Schiff base formation step. Reaction monitoring experiments tracing all the reaction species, including reactants, intermediates, and product, suggested that the reaction profile is distinctly different from ball-milling reactions without additives. Collectively, this work demonstrated that additive effect is a powerful tool to manipulate a reaction pathway in mechanochemical diazo-Cope rearrangement pathway, and this is expected to find broad interest in organic synthesis using mechanical force as an energy input.

Synthesis of Silica-Based Quaternized Adsorption Material and Study on Its Adsorption Behavior for Pu(IV).

In this research, we explored the synthesis optimization of the silica-based quaternized adsorption material (SG-VTS-VPQ) and its adsorption behavior for Pu(IV). By optimizing the synthesis process, the grafting amount of 4-vinylpyridine reached 1.25 mmol·g-1. According to the analysis of NMR and XPS, the quaternization rate of pyridine groups reached 91.13%. In the adsorption experiments, the thermodynamic experiment results show that the adsorption of Pu(IV) by SG-VTS-VPQ is more in line with the Langmuir adsorption model and the adsorption type is a typical chemical adsorption; the kinetic results show that adsorption process is more in line with the pseudo first-order kinetic model, and the larger specific surface area of SG-VTS-VPQ plays an important role in the adsorption. The results of the adsorption mechanism show that the adsorption of Pu(IV) by SG-VTS-VPQ is mainly complex anion Pu(NO3)62- and Pu(NO3)5-. This research provides in-depth and detailed ideas for the surface modification and application of porous silica gel, and at the same time provides a new way to develop the direction of the analysis of pretreatment materials in the spent fuel reprocessing field.

Gaseous environment modulates volatile emission and viability loss during seed artificial ageing.

MAIN CONCLUSION: Modulation of the gaseous environment using oxygen absorbers and/or silica gel shows potential for enhancing seed longevity through trapping toxic volatiles emitted by seeds during artificial ageing. Volatile profiling using non-invasive gas chromatography-mass spectrometry provides insight into the specific processes occurring during seed ageing. Production of alcohols, aldehydes and ketones, derived from processes such as alcoholic fermentation, lipid peroxidation and Maillard reactions, are known to be dependent on storage temperature and relative humidity, but little is known about the potential modulating role of the gaseous environment, which also affects seed lifespan, on volatile production. Seeds of Lolium perenne (Poaceae), Agrostemma githago (Caryophyllaceae) and Pisum sativum (Fabaceae) were aged under normal atmospheric oxygen conditions and in sealed vials containing either oxygen absorbers, oxygen absorbers and silica gel (equilibrated at 60% RH), or silica gel alone. Seeds of A. githago that were aged in the absence of oxygen maintained higher viability and produced fewer volatiles than seeds aged in air. In addition, seeds of A. githago and L. perenne aged in the presence of silica gel were longer lived than those aged without silica, with no effect on seed moisture content or oxygen concentration in the storage containers, but with silica gel acting as a volatile trap. These results indicate that the use of inexpensive oxygen absorbers and silica gel could improve seed longevity in storage for some species and suggests a potential, and previously unidentified, role for silica gel in ultra-dry storage.

Production, characterization, and immobilization of protease from the yeast Rhodotorula oryzicola.

The protease was produced extracellularly in submerged fermentation by the yeast Rhodotorula oryzicola using different sources of nitrogen and maximum activity (6.54 × 10-3 U/mg) was obtained in medium containing 2% casein (w/v). Purification of the protease by gel filtration chromatography resulted in a 3.07-fold increase of specific protease activity. The optimal pH and temperature for enzyme activity were 6.51 and 63.04 °C, respectively. Incubation in the presence of some salts enhanced enzyme activity, which peaked under 0.01 M BaCl2 . The enzyme retained about 90% of enzymatic activity at temperatures 50-60 °C. The commercially available enzyme carriers evaluated, silica gel, Celite 545, and chitosan effectively immobilized the protease. The enzyme immobilized in Celite 545 retained 73.53% of the initial activity after 15 reuse cycles. These results are quite promising for large-scale production and immobilization of protease from R. oryzicola, as the high operational stability of the immobilized enzyme lowers production costs in biotechnological applications that require high enzymatic activity and stability under high temperatures.

Biochemical characterization of extracellular fructosyltransferase from Aspergillus oryzae IPT-301 immobilized on silica gel for the production of fructooligosaccharides.

OBJECTIVE: Extracellular fructosyltransferase (FTase, E.C.2.4.1.9) from Aspergillus oryzae IPT-301 was immobilized on silica gel by adsorption and biochemically characterized aiming at its application in the transfructosylation reaction of sucrose for the production of fructooligossaccarides (FOS). RESULTS: The transfructosylation activity (AT) was maximized by the experimental design in function of the reaction pHs and temperatures. The AT of the immobilized enzyme showed the kinetics behavior described by the Hill model. The immobilized FTase showed reuse capacity for six consecutive reaction cycles and higher pH and thermal stability than the soluble enzyme. CONCLUSION: These results suggest a high potential of application of silica gel as support for FTase immobilization aiming at FOS production.