We have developed a novel method to protect DNA from cleavage using bioconjugated nanoparticles. Positively charged amino-modified silica nanoparticles have been directly prepared using water-in-oil microemulsion. Plasmid DNA can be easily enriched onto the positively charged nanoparticle surface, and the DNA strands are well protected from enzymatic cleavage. When incubated with nuclease enzyme for enzymatic cleavage, free plasmid DNA strands are completely cleaved, while those on the nanoparticle surfaces are intact. Our results clearly demonstrate unique properties of nanomaterials when combined with biomolecules. Our simple bionanotechnology will be highly useful in DNA separation, manipulation, and detection, and possibly in genetic engineering and gene therapy, as plasmid DNA can be protected in cellular environments without any change in its property.

In this paper, we unveil a novel naphthalimide-porphyrin hybrid based fluorescence probe (1) for ratiometric detection of Hg(2+) in aqueous solution and living cells. The ratiometric signal change of the probe is based on a carefully predesigned molecule containing two independent Hg(2+)-sensitive fluorophores with their maximal excitation wavelengths located at the same range, which shows reversibly specific ratiometric fluorescence responses induced by Hg(2+). In the new developed sensing system, the emissions of the two fluorophores are well-resolved with a 125 nm difference between two emission maxima, which can avoid the emission spectra overlap problem generally met by spectra-shift type probes and is especially favorable for ratiometric imaging intracellular Hg(2+). It also benefits from a large range of emission ratios and thereby a high sensitivity for Hg(2+) detection. Under optimized experimental conditions, the probe exhibits a stable response for Hg(2+) over a concentration range from 1.0 x 10(-7) to 5.0 x 10(-5) M, with a detection limit of 2.0 x 10(-8) M. The response of the probe toward Hg(2+) is reversible and fast (response time less than 2 min). Most importantly, the ratiometric fluorescence changes of the probe are remarkably specific for Hg(2+) in the presence of other abundant cellular metal ions (i.e., Na(+), K(+), Mg(2+), and Ca(2+)), essential transition metal ions in cells (such as Zn(2+), Fe(3+), Fe(2+), Cu(2+), Mn(2+), Co(2+), and Ni(2+)), and environmentally relevant heavy metal ions (Ag(+), Pb(2+), Cr(3+), and Cd(2+)), which meets the selective requirements for biomedical and environmental monitoring application. The recovery test of Hg(2+) in real water samples demonstrates the feasibility of the designed sensing system for Hg(2+) assay in practical samples. It has also been used for ratiometric imaging of Hg(2+) in living cells with satisfying resolution, which indicates that our novel designed probe has effectively avoided the general emission spectra overlap problem of other ratiometric probes.

This letter described the design and synthesis of a novel fluorescein-appended rhodamine spirolactam derivative and its preliminary application as a ratiometric fluorescent cellular imaging probe for Zn(2+). The ratiometric fluorescent signal change of the probe is based on an intramolecular fluorescence resonance energy transfer (FRET) mechanism modulated by a specific metal ion induced ring-opening process of the rhodamine spirolactam (acting as a trigger). In the new developed sensing system, the emission peaks of the two fluorophores are well-resolved, which can avoid the emission spectra overlap problem generally met by spectra-shift type probes and benefits for observation of fluorescence signal change at two different emission wavelengths with high resolution. It also benefits for a large range of emission ratios, thereby a high sensitivity for Zn(2+)detection. Under optimized experimental conditions, the probe exhibits a stable response for Zn(2+) over a concentration range from 2.0 x 10(-7) to 2.0 x 10(-5) M, with a detection limit of 4.0 x 10(-8) M. Most importantly, the novel probe has well solved the problem of serious interferences from other transition metal ions generally met by previously reported typical fluorescent probes for Zn(2+) with the di(2-picolyl)amine moiety as the receptor (in this case, the fluorescence response induced by Cd(2+)is even comparable to that of Zn(2+)) and shows a reversible and fast response toward Zn(2+). All these unique features make it particularly favorable for ratiometric cellular imaging investigations. It has been preliminarily used for ratiometric imaging of Zn(2+) in living cells with satisfying resolution.

Successful amidoximation of SiO 2 / polyacrylonitrile composite (SiO 2 / PAO).• PAO/SiO 2 highly efficient for Ga (III) recovery from slightly acidic solution.• Ga(III) desorption using 0.5 M HCl solutions for sorbent recycling.• PAO/SiO 2 sorbent is selective for Ga(III) recovery from multi-metal solutions.• Ga(III) efficiently and selectively recovered from Bayer liquor using SiO 2 / PAO.

Nanobubbles have many potential applications depending on their types. The long-term stability of different gas nanobubbles is necessary to be studied considering their applications. In the present study, five kinds of nanobubbles (N2, O2, Ar + 8%H2, air and CO2) in deionized water and a salt aqueous solution were prepared by the hydrodynamic cavitation method. The mean size and zeta potential of the nanobubbles were measured by a light scattering system, while the pH and Eh of the nanobubble suspensions were measured as a function of time. The nanobubble stability was predicted and discussed by the total potential energies between two bubbles by the extended Derjaguin–Landau–Verwey–Overbeek (DLVO) theory. The nanobubbles, except CO2, in deionized water showed a long-term stability for 60 days, while they were not stable in the 1 mM (milli mol/L) salt aqueous solution. During the 60 days, the bubble size gradually increased and decreased in deionized water. This size change was discussed by the Ostwald ripening effect coupled with the bubble interaction evaluated by the extended DLVO theory. On the other hand, CO2 nanobubbles in deionized water were not stable and disappeared after 5 days, while the CO2 nanobubbles in 1 mM of NaCl and CaCl2 aqueous solution became stable for 2 weeks. The floating and disappearing phenomena of nanobubbles were estimated and discussed by calculating the relationship between the terminal velocity of the floating bubble and bubble size.

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There is increasing interest in developing bioconjugated carriers for the cellular delivery of bioactive molecules to stem cells, since they can allow modulation of stem cell differentiation. The present study reported biocompatible silica nanoparticle-insulin conjugates for rat mesenchymal stem cell (RMSC) adipogenic differentiation in vitro. A systematic study was first carried out on the biocompatibility of the SiNPs with RMSCs. The cell viability assay was performed to screen the SiNP concentration for creating little cytotoxicity on RMSCs. Furthermore, transmission electron microscopy (TEM) and adipogenesis and osteogenesis assays revealed that the pure SiNPs had no effect on cellular ultrastructures, adipogenic differentiation, and osteogenic differentiation. Under the optimized SiNP concentration with little cytotoxicity on RMSC and no effects on the RMSC phenotype, SiNP-insulin conjugates were prepared and used for RMSC adipogenic differentiation. Results showed that RMSCs had the ability to differentiate into adipocytes when cultured in the presence of insulin-conjugated SiNPs. This work demonstrated that the biological activity of insulin conjugated to the SiNPs was not affected and the SiNPs could be used as biocompatibile carriers of insulin for RMSC adipogenic differentiation, which would help to expand the new potential application of SiNPs in stem cell research.

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