A facile route to synthesize n-SnO2/p-CuFe2O4 to rapidly degrade toxic methylene blue dye under natural sunlight

In the present study, the n-SnO₂/p-CuFe₂O₄ (p-CFO) complex was prepared by a two-step process. p-CFO synthesized by the molten salt method was coated with SnO₂ synthesized by a facile in situ chemical precipitation method. The formation of n-SnO₂/p-CFO was confirmed by powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) images showed that the sharp edges of uncoated pyramid-like p-CFO particles were covered by a thick layer of n-SnO₂ on coated p-CFO particles. The complete absence of Cu and only 3 wt% Fe on the surface of the n–p complex observed in the elemental analysis using energy-dispersive X-ray spectroscopy (EDX) on the n–p complex confirmed the presence of a thick layer of SnO₂ on the p-CFO surface. Diffuse reflectance spectroscopy (DRS) was employed to elucidate the bandgap engineering. The n-SnO₂/p-CFO complex and p-CFO showed 87% and 58.7% methylene blue (MB) degradation in 120 min under sunlight, respectively. The efficiency of the n–p complex recovered after 5 cycles (73.5%) and was found to be higher than that of the uncoated p-CFO (58.7%). The magnetically separable property of the n–p complex was evaluated by using vibration sample magnetometry (VSM) measurements and it was confirmed that the prepared photocatalyst can be easily recovered using an external magnet. The study reveals that the prepared complex could be a potential candidate for efficient photodegradation of organic dyes under sunlight due to its efficient recovery and reusability owing to its magnetic properties.

The synthesis of n-SnO₂/p-CuFe₂O₄ to degrade toxic methylene blue dye under natural sunlight and its mechanism.

Interlocked Graphene Oxide Provides Narrow Channels for Effective Water Desalination through Forward Osmosis

Unique two-dimensional water channels formed by stacked graphene oxide (GO) sheets that are "nonleachable" and nonswellable can show great potential for water remediation. The interlayer spacing controls the solute or ion sieving and plays a crucial role in water transport in GO-based membranes. Herein, the sub-nano-channels adjacent to the sheets are altered by either ionic or covalent cross-linking using magnesium hydroxide (Mg(OH)₂) and graphene oxide quantum dots (GQDs) (named GOM and G-GQD), respectively. In aqueous solution, these cross-linkers prevent the GO sheets from swelling and precisely control the interlayer spacing required for water permeation. In addition, these narrowed GO sheets facilitate significant improvement in salt rejection of a divalent ion by forward osmosis and selective dye rejection and are resistive toward biofouling and bacterial growth. The cross-linked GO membranes are robust enough to withstand strong cross-flow velocity and aided in unimpeded water transport through the nanochannels. Among the membranes, the G-GQD membranes (G-GQD) show better antifouling characteristics, dye separation performance over 95-97% for various dyes, divalent ion rejection by 97%, and no cytotoxicity against HaCaT cells as compared with other GO membranes. Our findings on interlocking the domains of nanoslits of the GO structure by small ecofriendly molecules portray these materials as potential candidates for water separation applications.

Synthesis of a Block Copolymer Exhibiting Cell-Responsive Phytochemical Release for Cancer Therapy

Phytochemicals constitute a promising class of therapeutics for the treatment of various diseases, but their delivery poses significant challenges. In this work, a nanoscale polyactive emulsion was designed for smart, cell-responsive delivery of a curcumin prodrug (curcumin dicarboxylate, CDA) that was chemically conjugated to enzymatically labile oligo-peptides with polycaprolactone (PCL) as the carrier. Matrix metalloproteinase (MMP)-sensitive (PLGLYAL) or nonsensitive (GPYYPLG) peptides were used as spacers for conjugating CDA and PCL. This CDA nanoemulsion incorporating the MMP-sensitive sequence exhibited markedly higher anti-cancer activity, cell internalization, and generation of reactive oxygen species in cancer cells in vitro than the control with the nonsensitive oligopeptide. Moreover, the nanopolyactives induced minimal cytotoxicity in noncancerous cell line. This work presents a unique strategy to engineer smart nano-polyactives for efficient and targeted delivery of phytochemicals.

Selective cleavage of the polyphosphoester in crosslinked copper based nanogels: enhanced antibacterial performance through controlled release of copper

Polymeric architectures with controlled and well-defined structural features are required to render a sustainable antibacterial surface - a key requirement in the design of polymeric membranes for water purification. Herein, surface selective crosslinking of copper oxide-polyphosphoester (CuO-PPE) hybrid nanogels on to polyvinylidene fluoride-styrene maleic anhydride (PVDF/SMA) ultrafiltration membranes was developed. The hybrid nanogels, composed of PPE and CuO, with inherent antifouling and antibacterial properties, were crosslinked using a macroinitiator (polyethylene glycol, PEG) and subsequently grafted on to PVDF/SMA by alkyne-anhydride reaction. Partially hydrolysed SMA solubilizes membrane proteins and the phosphatase/phospholipase triggers the cleavage of PPE segments resulting in controlled release of Cu ions. This unique strategy renders the membrane surface antibacterial through sustained and controlled release of Cu ions thereby generating intracellular reactive oxygen species (ROS). In addition, the enhanced antibiofouling performance of these membranes is facilitated by the presence of the hydrophilic macroinitiator (PEG and PPE). The modified membranes designed in this study are durable and possess long-term stability due to strong covalent interaction between CuO-PPE and the PVDF/SMA membrane. Studies on the flux, porosity and protein adsorption of the membranes were performed. An enhanced flux recovery ratio was observed for the modified membrane due to the pendant PPE groups (from CuO-PPE) which prohibit irreversible protein adsorption on the PVDF surface. The cytotoxicity of CuO-PPE is greatly reduced because of an effective coverage of CuO by biocompatible PPEs. This study opens up new avenues of fabricating "smart" inorganic nanoparticles that can be confined in a soft hybrid polymeric gel network with controlled release of Cu ions thereby precluding ubiquitous bacterial treatment in water filtration systems.

Modulated in Vitro Biocompatibility of a Unique Cross-Linked Salicylic Acid-Poly(ε-caprolactone)-Based Biodegradable Polymer

Herein, we report the development of a unique architecture by chemically cross-linking salicylic acid (SA)-based poly(anhydride ester) onto a biodegradable amine-functionalized poly(caprolactone) (PCL), using lactic acid as a spacer. The ester and amide linkages in the SA-PCL polymer, synthesized through melt condensation, were confirmed by NMR and FT-IR spectroscopic techniques. The enzymatic and nonenzymatic hydrolytic degradation profile exhibited linear degradation kinetics over an extended time period (>5 weeks). The compatibility and growth of C2C12 myoblast cells were found to be significantly improved on the fast-degrading SA-PCL substrates compared to those over neat PCL and amine-functionalized PCL. Further, the decreased red blood cell damage, illustrated by 0.39% hemolysis activity and a minimal number of platelet adhesion on a SA-PCL polymeric surface confirmed good hemocompatibility of the as-synthesized polymer. Together with a moderate bactericidal property, the spectrum of properties of this novel polymer can be attributed to the synergistic effect of the presence of chemical moieties of SA and amine groups in PCL. In summary, it is considered that a SA-PCL-based cross-linked composite can be utilized as a new biodegradable polymer.

Facile one-pot scalable strategy to engineer biocidal silver nanocluster assembly on thiolated PVDF membranes for water purification

Biofouling, due to bacterial growth and colonization, is a significant obstacle in water treatment that severely affects the membrane performance.

Understanding the pathway of antibacterial activity of copper oxide nanoparticles

This work investigates the role of oxidation state in the antibacterial activity of copper oxide nanoparticles (NPs).

Correction: Solution based rapid synthesis of AgCuO2 at room temperature

Correction for ‘Solution based rapid synthesis of AgCuO₂ at room temperature’ by Nagarajan Padmavathy et al., RSC Adv., 2014, 4, 62746–62750.

Solution based rapid synthesis of AgCuO2 at room temperature

We report a single step synthesis of AgCuO₂ within minutes resulting in a polycrystalline, single phase product crystallizing in a monoclinic system.

Interaction of ZnO nanoparticles with microbes--a physio and biochemical assay

The antibacterial activity of ZnO nanoparticles (nano ZnO) on various microorganisms has been investigated in this study and acting mechanism is proposed for E. coli a model organism by analyzing the growth, permeability and morphology of the bacterial cells. The experimental results indicated 1 mmoL (81.4 microg) nano ZnO could completely inhibit the growth of 10(7) cfu/mL bacterial cells in liquid Luria-Betrani medium. In the biochemical study, it has been observed that, nano ZnO resulted in the leakage of proteins. Chemiluminescence assay proved the generation of the reactive oxygen species into active state. When the cells of E. coli were exposed to nano ZnO, many pits were observed in bacterial cells by TEM and Fluorescence microscopy and the cells were found to be fragmentary. Released zinc ion from has been monitored by AAS. It suggested that nano ZnO is able to destroy the permeability of the bacterial membranes. Our study demonstrated that nano ZnO damages the structure of bacterial cell membrane and depressed the activity of some membranous enzymes by ROS production which caused E. coli bacteria to die eventually.

Enhanced bioactivity of ZnO nanoparticles-an antimicrobial study

In this study, we investigate the antibacterial activity of ZnO nanoparticles with various particle sizes. ZnO was prepared by the base hydrolysis of zinc acetate in a 2-propanol medium and also by a precipitation method using Zn(NO₃)₂ and NaOH. The products were characterized by x-ray diffraction (XRD) analysis, transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy. Bacteriological tests such as minimum inhibitory concentration (MIC) and disk diffusion were performed in Luria-Bertani and nutrient agar media on solid agar plates and in liquid broth systems using different concentrations of ZnO by a standard microbial method for the first time. Our bacteriological study showed the enhanced biocidal activity of ZnO nanoparticles compared with bulk ZnO in repeated experiments. This demonstrated that the bactericidal efficacy of ZnO nanoparticles increases with decreasing particle size. It is proposed that both the abrasiveness and the surface oxygen species of ZnO nanoparticles promote the biocidal properties of ZnO nanoparticles.