BackgroundSilver nanoparticles (AgNPs) are an important class of nanomaterials used as antimicrobial agents for a wide range of medical and industrial applications. However toxicity of AgNPs and impact of their physicochemical characteristics in in vivo models still need to be comprehensively characterized. The aim of this study was to investigate the effect of size and coating on tissue distribution and toxicity of AgNPs after intravenous administration in mice, and compare the results with those obtained after silver acetate administration.MethodsMale CD-1(ICR) mice were intravenously injected with AgNPs of different sizes (10 nm, 40 nm, 100 nm), citrate-or polyvinylpyrrolidone-coated, at a single dose of 10 mg/kg bw. An equivalent dose of silver ions was administered as silver acetate. Mice were euthanized 24 h after the treatment, and silver quantification by ICP-MS and histopathology were performed on spleen, liver, lungs, kidneys, brain, and blood.ResultsFor all particle sizes, regardless of their coating, the highest silver concentrations were found in the spleen and liver, followed by lung, kidney, and brain. Silver concentrations were significantly higher in the spleen, lung, kidney, brain, and blood of mice treated with 10 nm AgNPs than those treated with larger particles. Relevant toxic effects (midzonal hepatocellular necrosis, gall bladder hemorrhage) were found in mice treated with 10 nm AgNPs, while in mice treated with 40 nm and 100 nm AgNPs lesions were milder or negligible, respectively. In mice treated with silver acetate, silver concentrations were significantly lower in the spleen and lung, and higher in the kidney than in mice treated with 10 nm AgNPs, and a different target organ of toxicity was identified (kidney).ConclusionsAdministration of the smallest (10 nm) nanoparticles resulted in enhanced silver tissue distribution and overt hepatobiliary toxicity compared to larger ones (40 and 100 nm), while coating had no relevant impact. Distinct patterns of tissue distribution and toxicity were observed after silver acetate administration. It is concluded that if AgNPs become systemically available, they behave differently from ionic silver, exerting distinct and size-dependent effects, strictly related to the nanoparticulate form.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0124-x) contains supplementary material, which is available to authorized users.

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The combination of materials that possess different properties (such as, for instance, fluorescence and magnetism) into one single object of nanoscale size represents an attractive challenge for biotechnology, especially for their potential relevance in biomedical applications. We report here the preparation of novel bifunctional conjugates based on the linkage of inorganic nanoparticles to organic oligothiophene fluorophores (OTFs). In comparison to the organic dyes commonly used in bioimaging and more similarly to colloidal quantum dots, OTFs have broad optical absorption spectra, and therefore OTF fluorophores emitting at different colors can be excited with a single excitation source, allowing for easier multiplexing analysis. In this work we show the preparation of OTF-nanoparticle conjugates based on gold and iron oxide nanoparticles and their characterization using different techniques such as gel electrophoresis, photoluminescence spectroscopy, dynamic light scattering, and so on. In addition, by performing an in vitro study on human tumor cells we show that OTF-nanoparticle conjugates emitting at different colors can be used for multiplexing detection. Also, in the case of iron oxide-OTF conjugates, once uptaken by the cells, we show that they preserve both their fluorescent and their magnetic properties.

The study of the mechanisms underlying the uptake and release of bioactive molecules from stimuli-responsive nanoparticles is the key to their application in biomedical fields. Here, we present the pH-controlled uptake and release of two chemically different solutes from newly synthesized nanogels, showing their potential as pH-controlled dual drug delivery systems. Nanogels were synthesized by emulsion copolymerization of methacrylic acid (MAA) and methyl acrylate (MA), and then characterized by FT-IR, 1 H NMR, and dynamic light scattering (DLS). To study the encapsulation and delivery properties of PMA-PMAA nanogels, a hydrophobic thiophene fluorophore (TF) and a cationic drug, doxorubicin (DX), were chosen. The uptake and release experiments were run at different pH values and monitored by absorption and both steady-state and time-resolved photoluminescence (PL) spectroscopy. Interestingly, the release of TF and DX was obtained under basic and acidic conditions, respectively, thus demonstrating a pH-controlled dual drug release by PMA-PMAA nanogels depending on the chemical nature of the tested solutes.

Nanometer-sized poly(acrylic acid) (PAA) hydrogels were synthesized by emulsion polymerization of methyl acrylate and subsequent acidic hydrolysis. The nanohydrogel was characterized by spectroscopic methods (FTIR and 1 H-NMR) and scanning probe techniques, and their pH-dependent swelling behavior was studied by dynamic light scattering. To determine the suitability of PAA nanogels as pH-sensitive carriers for biomedical applications, uptake and release of an oligothiophene fluorophore and its albumin conjugated from PAA nanogels were investigated as a function of pH by absorption and photoluminescence measurements. It was observed that uptake and release processes of both the oligothiophene and its conjugate could be controlled by changing the pH of the external solution.