Surface and composition effects on the biphasic cytotoxicity of nanocomposites synthesized using leaf extracts.

The Malus sylvestris L. (LE1), Pinus sylvestris L. (LE2), and Sorbus aucuparia L. (LE3) leaves` extracts were used for the synthesis of silver (Ag) nanocomposites containing different amounts of silver chloride (AgCl), silver metal (Agmet), and silver phosphate (Ag3PO4). These nanocomposites were capped with the organic functional groups in the leaf extract. Notably, the nanocomposites caused biphasic cytotoxic response on cells; first attributed to the inhibition of cell growth and second to cell death. The nanocomposites were biocompatible with normal embryonic kidney (HEK293) cells in the cytotoxic range for cancer cells. LE2Ag1 [25(±1) °C synthesis] nanocomposites exhibited the highest cytotoxicity towards HeLa (lethal concentration- LC50 value of 11.4 µg mL-1) and A549 (LC50 value of 14.7 µg mL-1) after 24-h incubation and its efficiency was shown also for the more resistant MCF-7 and MDA-MB-231, however, their respective LC50 values were larger. For the HeLa cell line, this designed LE2Ag1 nanocomposite exhibited an LC50 value similar to the effective concentration (EC50) value of Cisplatin and about 3 times larger than Doxorubicin. LE2Ag1 nanocomposite contained Ag3PO4 in the composite and P on the surface, higher AgCl content, smaller crystallite size of all nanoparticle phases, and carbon-rich oxygen-deficient surface compared to all other nanocomposites.

Improving the Selectivity of the C-C Coupled Product Electrosynthesis by Using Molecularly Imprinted Polymer─An Enhanced Route from Phenol to Biphenol.

We developed a procedure for selective 2,4-dimethylphenol, DMPh, direct electro-oxidation to 3,3',5,5'-tetramethyl-2,2'-biphenol, TMBh, a C-C coupled product. For that, we used an electrode coated with a product-selective molecularly imprinted polymer (MIP). The procedure is reasonably selective toward TMBh without requiring harmful additives or elevated temperatures. The TMBh product itself was used as a template for imprinting. We followed the template interaction with various functional monomers (FMs) using density functional theory (DFT) simulations to select optimal FM. On this basis, we used a prepolymerization complex of TMBh with carboxyl-containing FM at a 1:2 TMBh-to-FM molar ratio for MIP fabrication. The template-FM interaction was also followed by using different spectroscopic techniques. Then, we prepared the MIP on the electrode surface in the form of a thin film by the potentiodynamic electropolymerization of the chosen complex and extracted the template. Afterward, we characterized the fabricated films by using electrochemistry, FTIR spectroscopy, and AFM, elucidating their composition and morphology. Ultimately, the DMPh electro-oxidation was performed on the MIP film-coated electrode to obtain the desired TMBh product. The electrosynthesis selectivity was much higher at the electrode coated with MIP film in comparison with the reference nonimprinted polymer (NIP) film-coated or bare electrodes, reaching 39% under optimized conditions. MIP film thickness and electrosynthesis parameters significantly affected the electrosynthesis yield and selectivity. At thicker films, the yield was higher at the expense of selectivity, while the electrosynthesis potential increase enhanced the TMBh product yield. Computer simulations of the imprinted cavity interaction with the substrate molecule demonstrated that the MIP cavity promoted direct coupling of the substrate to form the desired TMBh product.

Valorizing the Unexplored Filtration Waste of Brewing Industry for Green Silver Nanocomposite Synthesis.

The brewing industry generates a substantial amount of by-products rich in polyphenols, carbohydrates, sugars, sulfates, nitrogen compounds, organic carbon, and several elements, including chlorine, magnesium, and phosphorus. Although limited quantities of these by-products are used in fertilizers and composts, a large amount is discarded as waste. Therefore, it is crucial to identify different ways of valorizing the by-products. Research regarding the valorization of the brewery by-products is still in its nascent stage; therefore, it still has high potential. Herein, we report the valorization of the brewery by-product from the filtration stage of the brewing process (BW9) to synthesize silver nanocomposites as this waste has remained largely unexplored. The BW9 nanocomposites have been compared to those obtained from the brewery product B. The chemical composition analysis of BW9 and B revealed several organic moieties capable of reducing metal salts and capping the formed nanoparticles. Therefore, the brewery waste from stage 9 was valorized as a precursor and added to silver-based precursor at various temperatures (25, 50, and 80 °C) and for various time periods (10, 30, and 120 min) to synthesize silver nanocomposites. The nanocomposites obtained using BW9 were compared to those obtained using the main product of the brewing industry, beer (B). Synthesized nanocomposites composed of AgCl as a major phase and silver metal (Agmet) was incorporated in minor quantities. In addition, Ag3PO4 was also found in B nanocomposites in minor quantities (up to 34 wt.%). The surface morphology depicted globular nanoparticles with layered structures. Small ball-like aggregates on the layer representative of Ag3PO4 were observed in B nanocomposites. The surface of nanocomposites was capped with organic content and functional groups present in the brewery products. The nanocomposites demonstrated high antibacterial activity against Escherichia coli (E. coli), with BW9 nanocomposites exhibiting a higher activity than B nanocomposites.

Valorization of Brewery Wastes for the Synthesis of Silver Nanocomposites Containing Orthophosphate.

Brewery wastes from stage 5 (Wort precipitate: BW5) and stage 7 (Brewer's spent yeast: BW7) were valorized for the synthesis of silver phosphate nanocomposites. Nanoparticles were synthesized by converting silver salt in the presence of brewery wastes at different temperatures (25, 50, and 80 °C) and times (10, 30, and 120 min). Unexpectedly, BW7 yielded Ag3PO4 nanoparticles with minor contents of AgCl and Ag metal (Agmet). Contrastingly, BW5 produced AgCl nanoparticles with minor amounts of Ag3PO4 and Agmet. Nanocomposites with different component ratios were obtained by simply varying the synthesis temperature and time. The morphology of the nanocomposites contained ball-like structures representative of Ag3PO4 and stacked layers and fused particles representing AgCl and Agmet. The capping on the nanoparticles contained organic groups from the brewery by-products, and the surface overlayer had a rich chemical composition. The organic overlayers on BW7 nanocomposites were thinner than those on BW5 nanocomposites. Notably, the nanocomposites exhibited high antibacterial activity against Escherichia coli ATCC 25922. The antibacterial activity was higher for BW7 nanocomposites due to a larger silver phosphate content in the composition and a thin organic overlayer. The growth of Agmet in the structure adversely affected the antimicrobial property of the nanocomposites.