Monodisperse superparamagnetic Fe3O4 nanoparticles coated with oleic acid were prepared by thermal decomposition of Fe(III) glucuronate. The shape, size, and particle size distribution were controlled by varying the reaction parameters, such as the reaction temperature, concentration of the stabilizer, and type of high-boiling-point solvents. Magnetite particles were characterized by transmission electron microscopy (TEM), as well as electron diffraction (SAED), X-ray diffraction (XRD), dynamic light scattering (DLS), and magnetometer measurements. The particle coating was analyzed by atomic absorption spectroscopy (AAS) and attenuated total reflection (ATR) Fourier transform infrared spectroscopy (FTIR) spectroscopy. To make the Fe3O4 nanoparticles dispersible in water, the particle surface was modified with α-carboxyl-ω-bis(ethane-2,1-diyl)phosphonic acid-terminated poly(3-O-methacryloyl-α-D-glucopyranose) (PMG-P). For future practical biomedical applications, nontoxicity plays a key role, and the PMG-P&Fe3O4 nanoparticles were tested on rat mesenchymal stem cells to determine the particle toxicity and their ability to label the cells. MR relaxometry confirmed that the PMG-P&Fe3O4 nanoparticles had high relaxivity but rather low cellular uptake. Nevertheless, the labeled cells still provided visible contrast enhancement in the magnetic resonance image. In addition, the cell viability was not compromised by the nanoparticles. Therefore, the PMG-P&Fe3O4 nanoparticles have the potential to be used in biomedical applications, especially as contrast agents for magnetic resonance imaging.

SummarySilver (AgNPs) and maghemite, i.e., superparamagnetic iron oxide nanoparticles (SPIONs) are promising candidates for new medical applications, which implies the need for strict information regarding their physicochemical characteristics and behavior in a biological environment. The currently developed AgNPs and SPIONs encompass a myriad of sizes and surface coatings, which affect NPs properties and may improve their biocompatibility. This study is aimed to evaluate the effects of surface coating on colloidal stability and behavior of AgNPs and SPIONs in modelled biological environments using dynamic and electrophoretic light scattering techniques, as well as transmission electron microscopy to visualize the behavior of the NP. Three dispersion media were investigated: ultrapure water (UW), biological cell culture medium without addition of protein (BM), and BM supplemented with common serum protein (BMP). The obtained results showed that different coating agents on AgNPs and SPIONs produced different stabilities in the same biological media. The combination of negative charge and high adsorption strength of coating agents proved to be important for achieving good stability of metallic NPs in electrolyte-rich fluids. Most importantly, the presence of proteins provided colloidal stabilization to metallic NPs in biological fluids regardless of their chemical composition, surface structure and surface charge. In addition, an assessment of AgNP and SPION behavior in real biological fluids, rat whole blood (WhBl) and blood plasma (BlPl), revealed that the composition of a biological medium is crucial for the colloidal stability and type of metallic NP transformation. Our results highlight the importance of physicochemical characterization and stability evaluation of metallic NPs in a variety of biological systems including as many NP properties as possible.

Experimental setup for in vitro evaluation of metallic nanoparticles where interferences depend on metal core, surface coating, and the test system. ABSTRACTScreening programs for the evaluation of nanomaterial value and safety rely on in vitro tests.The exceptional physicochemical properties of metallic nanoparticles (NPs), such as large surface area and chemically active surface, may provoke their interferences with in vitro methods and analytical techniques used for evaluation of biocompatibility or toxicity of NPs.This study aimed to determine if such interferences could be predicted on the basis of the surface characteristics of metallic NPs by investigating the effect of different surface coatings of silver (AgNPs) and maghemite NPs (-Fe 2 O 3 NPs) on common in vitro assays scoring two of the main cytotoxic endpoints: cell viability and oxidative stress response. We examined optical, adsorptive and chemically reactive types of NPs interferences with cell viability assays (MTT, MTS, and WST-8) and assays employing fluorescent dyes as markers for production of reactive oxygen species (DCFH-DA and DHE) or glutathione level (MBCl).Each type of tested NPs affected all of the six investigated assays leading to false interpretation of obtained results. The extent and type of interference were dependent on the type and surface coating of NPs as well as on their stability in biological media. The results have shown that interferences were concentration-, particle type-and assay type-dependent.This study demonstrated that common in vitro assays, without appropriate cause-and-effect analysis and adaptation or modification, are ineffective in the evaluation of biological effects of metallic NPs due to their interaction with optical readouts and assay components. A comprehensive and feasible experimental setup has been proposed to gain a reproducible and reliable in vitro evaluation as the first step in the health assessment of metallic NPs. 5 studies should ideally be designed to avoid any undesirable interactions and side effects influenced by nanospecific properties. 8,9 Unique physicochemical properties of NPs such as high adsorption capacity, hydrophobicity, surface charge, optical and magnetic properties, or catalytic activity may interfere with assay components and/or detection systems used by in vitro methods. 2,5-10 In last decade, an increasing number of studies have evidenced data artefacts resulting from NPs interferences with light absorption or fluorescence used for detection in assays, uncontrolled chemical reactions, or adsorption of assay compounds to the NP surfaces. 11-30 Simply performing in vitro toxicity assays for NPs according to the manufacturers' recommendations can lead to underestimations or overestimations of toxicity. 13-18 It has been reviewed that engineered NPs interfere with classic cytotoxicity assays in a concentration-, particle-and assay-specific manner. 7-10 Consequently, testing NPs with established and commercial assays represents a challenge requiring careful analysis and ev...

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Streptococcus salivarius is a Gram-positive bacterial commensal and pioneer colonizer of the human oral cavity. Many strains produce ribosomally synthesized proteinaceous antibiotics (bacteriocins), and some strains have been developed for use as oral probiotics. Here, we present the draft genome sequence of the bacteriocin-producing oral probiotic S. salivarius strain M18.The Gram-positive bacterium Streptococcus salivarius is a pioneer colonizer of the human oral cavity, and large populations persist at this site for the host's lifetime (12). S. salivarius is the prototype species of the S. salivarius group, which includes the important dairy species Streptococcus thermophilus (6). Many S. salivarius strains produce ribosomally synthesized proteinaceous antibiotics (bacteriocins; reviewed in reference 14), typically encoded by megaplasmid-borne loci (10). As S. salivarius is generally associated with good oral health, several bacteriocinogenic strains with proven safety records have been developed as oral probiotics (2-4, 8, 12).S. salivarius M18 (formerly strain Mia) is a megaplasmidcarrying oral probiotic exhibiting broad-spectrum inhibitory activity against several streptococcal pathogens, notably the caries-causing Streptococcus mutans (10). In order to provide a genetic basis for factors enhancing its probiotic candidature, e.g., bacteriocin repertoire and colonization-related genes, and also to establish whether the strain is free of virulence factors and antibiotic resistance determinants, the S. salivarius M18 genome was sequenced by a whole-genome shotgun strategy using a Roche GS-FLX pyrosequencer (7). Approximately 42.9 million base pairs (ϳ18-fold coverage) was assembled by Roche GS de novo assembler (versions 1.1.03.24 and 2.3) into ϳ150 contigs. All putative chromosomal contigs were ordered relative to the megaplasmid-free S. salivarius CCHSS3 genome sequence (GenBank accession number FR873481). Gap closures were achieved by direct Sanger-based sequencing of PCR amplicons generated with specific primers designed for contig termini.The high-quality draft S. salivarius M18 chromosome sequence currently comprises five supercontigs (2,142,944 bp; GC content of 39.6%). The remaining genomic gaps contain multiple copies of large (Ͼ6-kb) genes encoding putative highly repetitive serine-rich proteins homologous to the Streptococcus gordonii Hsa adhesin (9). The latter, which are conspicuously absent in S. thermophilus, may aid S. salivarius in colonizing oral surfaces. Automated annotation carried out by the rapid annotations using subsystems technology (RAST) (1) and NCBI Prokaryotic Genomes Automatic Annotation Pipeline (PGAAP) servers revealed 1,975 protein-coding sequences (CDSs), six rRNA operons, and 68 tRNA genes. A variety of insertion sequences were identified, with ISSag8 and IS1193 being the most common. In addition, the chromosome contains a locus (slm) specifying the production of a new anti-S. mutans lantibiotic bacteriocin designated salivaricin M.The S. salivarius M18 megaplasmid, pSsal-M...