Interactions Between Silver Nanoparticles and Culture Medium Biomolecules with Dose and Time Dependencies

The interaction between silver nanoparticles (AgNPs) and molecules producing coronas plays a key role in cytotoxicity mechanisms. Once adsorbed coronas determine the destiny of nanomaterials in vivo, their effective deployment in the biomedical field requires a comprehensive understanding of the dynamic interactions of biomolecules with nanoparticles. In this work, we characterized 40 nm AgNPs in three different nutritional cell media at different molar concentrations and incubation times to study the binding mechanism of molecules on surface nanoparticles. In addition, their cytotoxic effects have been studied in three cell lineages used as tissue regeneration models: FN1, HUV-EC-C, RAW 264.7. According to the data, when biomolecules from DMEM medium were in contact with AgNPs, agglomeration and precipitation occurred. However, FBS medium proteins indicated the formation of coronas over the nanoparticles. Nonetheless, little adsorption of molecules around the nanoparticles was observed when compared to DMEM supplemented with 10% FBS. These findings indicate that when nanoparticles and bioproteins from supplemented media interact, inorganic salts from DMEM contribute to produce large bio-coronas, the size of which varies with the concentration and time. The static quenching mechanism was shown to be responsible for the fluorescence quenching of the bioprotein aggregates on the AgNPs surface. The calculated bioprotein-nanoparticle surface binding constants were on the order of 105 M-1 at 37 °C, with hydrophobic interactions driven by enthalpy and entropy playing a role, as confirmed by thermodynamic analysis. Cytotoxicity data showed a systematic degrowth in the viable cell population as the number of nanoparticles increased and the diameter of coronas decreased. Cytotoxic intervals associated with half decrease of cell population were established for AgNPs molar concentration of 75 µM for 24 h and 50 µM for 48 h. In summary, through the cytotoxicity mechanism of bio-coronas we are able to manipulate cells' expansion rates to promote specific processes, such inflammatory mechanisms, at different time instants.

Antibacterial effect, cytotoxicity, and bond strength of a modified dental adhesive containing silver nanoparticles

This study aimed to evaluate the antibacterial effect, cytotoxicity, and microtensile bond strength of an adhesive system containing silver nanoparticles (NAg). NAg was synthesized and incorporated (500 and 1000 ppm) into Scotchbond Multi-Purpose (SBMP) primer and bond. A microtensile bond test (μTBS) was performed after 24 h and 1 year. The adhesive interface was characterized using a confocal Raman microscope. The antibacterial activity was assessed using agar diffusion and biofilm inhibition assays (S. mutans). MTT assay was used to assess the cytotoxicity of NAg-conditioned culture media on human dental pulp stem cells (hDPSCs). The results were statistically analyzed using analysis of variance and Tukey's tests (α = .01). Incorporating 500 and 1000 ppm of NAg in the SBMP did not affect the μTBS after 24 h (p > 0.05). However, in the 1 year evaluation, 500 ppm presented the highest μTBS values (p < 0.05). The addition of NAg at 500 and 1000 ppm in the primer and bond led to larger inhibition halos and colony-forming units than the control (p < 0.05). For the unpolymerized and polymerized groups, the combination of primer and bond presented the highest cytotoxic effects on hDPSCs (p < 0.05). In conclusion, incorporating 500 or 1000 ppm of NAg into an etch-and-rinse adhesive system led to an antibacterial effect without altering the cytotoxicity. SBMP at 500 ppm presented a higher μTBS at 1 year.

Phosphotungstic acid impregnated niobium coated superparamagnetic iron oxide nanoparticles as recyclable catalyst for selective isomerization of terpenes

Conversion efficiency as high as 80-100% and 50% selectivity for camphene and limonene was achieved with low production of polymeric byproducts (18-28%), easy recovery with a magnet and reuse for up to five cycles maintaining similar activity and distribution of products, using a new magnetically recyclable catalyst based on niobium oxide coated on superparamagnetic iron oxide nanoparticles (SPION) impregnated with phosphotungstic acid (HPW). The catalyst was demonstrated to be effective in the selective conversion of alpha and beta-pinenes into valuable terpenes, under ultrasonic probe activation and with toluene as solvent. A unique synergic effect between the components generating more active and selective catalytic sites was demonstrated, indicating that the SPION covered with 30 wt% of Nb2O5 gives the best performance when impregnated with HPW as co-catalyst. The materials were fully characterized by XRD, EDX, XPS, TEM, BET, VSM and FTIR.

Superparamagnetic iron oxide nanoparticles (SPIONs) conjugated with lipase Candida antarctica A for biodiesel synthesis

Biodiesel is an alternative biodegradable and non-toxic fuel, with a low emission profile and capable of reducing significantly the level of carcinogenic pollutants released into the atmosphere. A newly designed nano-biocatalyst prepared by conjugation of lipase A on superparamagnetic iron oxide nanoparticles (SPIONs) demonstrated high efficiency for production of biodiesel by the reaction of soybean oil with anhydrous methanol. The nanomaterial was characterized by FTIR, TGA and XRD, and its enzymatic activity compared with Lipozyme 435, a commercial gold standard from Novozyme™, which presented average enzymatic activity of 4559 ± 75 only twice as large as that of the SPION-CAL-A catalyst (2283 ± 249 PLU g-1), whereas Lipozyme TLIM showed a much lower activity of 588 ± 16 PLU g-1. These results were confirmed in the transesterification reaction for production of biodiesel where a yield of 11.4% was achieved with Lipozyme 435 and 4.6 ± 0.5% with the nano-biocatalyst. Such an improved performance associated with easy magnetic recovery and reuse make the material potentially interesting for production of biodiesel from used cooking oil, adding value to this abundant resource.

Resistência de União à Dentina de um Sistema Adesivo com Diferentes Concentrações de Nanopartículas de Prata

O objetivo do estudo foi incorporar diferentes concentrações de nanopartículas de prata (NAg) em sistema adesivo e avaliar sua influência na resistência de união à dentina. Quarenta e oito terceiros molares humanos hígidos (CEP 204.601) foram distribuídos aleatoriamente em 12 grupos (n4): controle Scotchbond Multi-Purpose (SBMP), adição de 50, 100, 150, 200 e 250 ppm de NAg no primer do SBMP, avaliados após 24h e 6 meses. Os dentes foram preparados, restaurados, seccionados em palitos (0,7 ± 0,2 mm2) e ensaiados à microtração (μTBS). Os grupos NAg 200ppm e NAg 250ppm apresentaram os maiores valores de μTBS, semelhantes ao SBMP considerando os tempos de avaliação (24h ou 6m). Os grupos NAg 50ppm (6m), NAg 100ppm (24h) e NAg 150ppm (24h e 6m) apresentaram menores valores de µTBS, semelhantes entre si e estatisticamente inferiores ao SBMP (49,4MPa). As demais condições experimentais apresentaram valores semelhantes ao SBMP (24h e 6m). Concluiu-se que a incorporação de concentrações de 200 e 250 ppm de NAg não alterou a resistência de união do sistema adesivo à dentina.Palavras-chave: Adesivos Dentinários. Prata. Resistência à Tração.

Ultrasmall cationic superparamagnetic iron oxide nanoparticles as nontoxic and efficient MRI contrast agent and magnetic-targeting tool

Fully dispersible, cationic ultrasmall (7 nm diameter) superparamagnetic iron oxide nanoparticles, exhibiting high relaxivity (178 mM⁻¹s⁻¹ in 0.47 T) and no acute or subchronic toxicity in Wistar rats, were studied and their suitability as contrast agents for magnetic resonance imaging and material for development of new diagnostic and treatment tools demonstrated. After intravenous injection (10 mg/kg body weight), they circulated throughout the vascular system causing no microhemorrhage or thrombus, neither inflammatory processes at the mesentery vascular bed and hepatic sinusoids (leukocyte rolling, adhesion, or migration as evaluated by intravital microscopy), but having been spontaneously concentrated in the liver, spleen, and kidneys, they caused strong negative contrast. The nanoparticles are cleared from kidneys and bladder in few days, whereas the complete elimination from liver and spleen occurred only after 4 weeks. Ex vivo studies demonstrated that cationic ultrasmall superparamagnetic iron oxide nanoparticles caused no effects on hepatic and renal enzymes dosage as well as on leukocyte count. In addition, they were readily concentrated in rat thigh by a magnet showing its potential as magnetically targeted carriers of therapeutic and diagnostic agents. Summarizing, cationic ultrasmall superparamagnetic iron oxide nanoparticles are nontoxic and efficient magnetic resonance imaging contrast agents useful as platform for the development of new materials for application in theranostics.