Cu and CuO/titanate nanobelt based network assemblies for enhanced visible light photocatalysis.

3D network configurations of copper(II) oxide/titanate nanobelt (CuO/TiNBs) and copper/titanate nanobelt (Cu/TiNBs) were formed using a two-step polyelectrolyte-assisted synthesis and assembly approach. The photoactivity of the TiNB/CuO and Cu/TiNB composite networks is significantly enhanced as compared to the activity of 3D structures formed of pristine TiNB. An efficient, UV-vis-light-induced electron transfer at the two-component interface achieved by the intimate coupling of TiNB with p-type semiconducting CuO and plasmonic Cu nanoparticles in composite heterostructures facilitates control over the system's exciton dynamics, which results in highly efficient UV-vis photocatalytic performance of heterostructures. The superior photocatalytic activity of the metal and semiconductor/semiconductor nanocomposite structures in the visible region is discussed, highlighting the role of interfacial electron-charge transfer (IFCT) in semiconductor-semiconductor (CuO/TiNB) and surface plasmon resonance (SPR) of Cu nanoparticles in metal-semiconductor heterostructures.

Multifunctional PLGA particles containing poly(l-glutamic acid)-capped silver nanoparticles and ascorbic acid with simultaneous antioxidative and prolonged antimicrobial activity.

A water-soluble antioxidant (ascorbic acid, vitamin C) was encapsulated together with poly(l-glutamic acid)-capped silver nanoparticles (AgNpPGA) within a poly(lactide-co-glycolide) (PLGA) polymeric matrix and their synergistic effects were studied. The PLGA/AgNpPGA/ascorbic acid particles synthesized by a physicochemical method with solvent/non-solvent systems are spherical, have a mean diameter of 775 nm and a narrow size distribution with a polydispersity index of 0.158. The encapsulation efficiency of AgNpPGA/ascorbic acid within PLGA was determined to be >90%. The entire amount of encapsulated ascorbic acid was released in 68 days, and the entire amount of AgNpPGAs was released in 87 days of degradation. The influence of PLGA/AgNpPGA/ascorbic acid on cell viability, generation of reactive oxygen species (ROS) in HepG2 cells, as well as antimicrobial activity against seven different pathogens was investigated. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay indicated good biocompatibility of these PLGA/AgNpPGA/ascorbic acid particles. We measured the kinetics of ROS formation in HepG2 cells by a DCFH-DA assay, and found that PLGA/AgNpPGA/ascorbic acid caused a significant decrease in DCF fluorescence intensity, which was 2-fold lower than that in control cells after a 5h exposure. This indicates that the PLGA/AgNpPGA/ascorbic acid microspheres either act as scavengers of intracellular ROS and/or reduce their formation. Also, the results of antimicrobial activity of PLGA/AgNpPGA/ascorbic acid obtained by the broth microdilution method showed superior and extended activity of these particles. The samples were characterized using Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, transmission electron microscopy, zeta potential and particle size analysis. This paper presents a new approach to the treatment of infection that at the same time offers a very pronounced antioxidant effect.

A new, simple, green, and one-pot four-component synthesis of bare and poly(α,γ, L-glutamic acid)-capped silver nanoparticles.

A simple and green chemical method has been developed to synthesize stable bare and capped silver nanoparticles based on the reduction of silver ions by glucose and capping by poly(α,γ,L-glutamic acid) (PGA). The use of ammonia during synthesis was avoided. PGA has had a dual role in the synthesis and was used as a capping agent to make the silver nanoparticle more biocompatible and to protect the nanoparticles from agglomerating in the liquid medium. The synthesized PGA-capped silver nanoparticles in the size range 5-45 nm were stable over long periods of time, without signs of precipitation. Morphological examination has shown that the silver nanoparticles had a nearly spherical, multiply twinned structure. The effects of the reaction temperature and the reaction time during the synthesis were investigated too. The biocompatibility of the PGA-capped silver nano-particles is discussed in terms of in vitro toxicity with human intestinal Caco-2 cells. The samples were characterized by UV-Visible spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, and zeta potential measurements.

Poly(D,L-lactide-co-glycolide)/hydroxyapatite core-shell nanospheres. Part 3: properties of hydroxyapatite nano-rods and investigation of a distribution of the drug within the composite.

A step-by-step analysis of the formation and the drug loading of the poly(D,L-lactide-co-glycolide)/hydroxyapatite (PLGA/HAp) composite was carried out in a perspective of the following parameters: the structure, the morphology and the adsorption/desorption properties of the composite's bioceramic part. The authors demonstrated the importance of the material's capacity to form a fine dispersion of solid HAp particles, as an initial step, for the further loading of the drug and for the formation of the core-shell structures. The nanometer-sized rods of HAp have the capacity of ensuring a rapid adsorption and a controlled desorption of the drug from their surface, and they can act as a nucleating site for the formation of polymeric cores. Each component of this material was labeled with fluorescence dye, which enabled an insight into the distribution of the components in the core-shells that were obtained as the final outcome. Such an analysis showed a high level of uniformity among the cores enclosed within polymeric shells. From a practical perspective, the labeling of each component of the composite can be regarded as an additional functionality of the material: labeling can enable us to monitor its action during the healing process. This ability to be easily detected is expected to enhance the procedure for the controlled delivery of antibiotics after their local implantation of carriers loaded with the antibiotic and to provide more careful control over this process.

Synthetical bone-like and biological hydroxyapatites: a comparative study of crystal structure and morphology.

Phase composition, crystal structure and morphology of biological hydroxyapatite (BHAp) extracted from human mandible bone, and carbonated hydroxyapatite (CHAp), synthesized by the chemical precipitation method, were studied by x-ray powder diffraction (XRD), Fourier transform infrared (FTIR) and Raman (R) spectroscopy techniques, combined with transmission electron microscopy (TEM). Structural and microstructural parameters were determined through Rietveld refinement of recorded XRD data, performed using the FullProf computing program, and TEM. Microstructural analysis shows anisotropic extension along the [00l] crystallographic direction (i.e. elongated crystallites shape) of both investigated samples. The average crystallite sizes of 10 and 8 nm were estimated for BHAp and CHAp, respectively. The FTIR and R spectroscopy studies show that carbonate ions substitute both phosphate and hydroxyl ions in the crystal structure of BHAp as well as in CHAp, indicating that both of them are mixed AB-type of CHAp. The thermal behaviour and carbonate content were analysed using thermogravimetric and differential thermal analysis. The carbonate content of about 1 wt.% and phase transition, at near 790 °C, from HAp to ß-tricalcium phosphate were determined in both samples. The quality of synthesized CHAp powder, particularly, the particle size distribution and uniformity of morphology, was analysed by a particle size analyser based on laser diffraction and field emission scanning electron microscopy, respectively. These data were used to discuss similarity between natural and synthetic CHAp. Good correlation between the unit cell parameters, average crystallite size, morphology, carbonate content and crystallographic positions of carbonate ions in natural and synthetic HAp samples was found.

Silver nanoparticles on titanate nanobelts via the self-assembly of weak polyelectrolytes: synthesis and photocatalytic properties.

A weak-polyelectrolyte multilayer on a surface of titanate nanobelts (Ti-NBs) was utilized as a template for in situ Ag nanoparticle formation in the fabrication of Ag-loaded Ti-NBs nanocomposites. The polyelectrolyte multilayer (PEM) was fabricated using layer-by-layer self-assembly of poly(acrylic acid) (PAA) and poly(allylamine hydrochloride) (PAH) on the surface of high-surface-area titanate nanobelts (Ti-NBs) synthesized using a hydrothermal procedure. The concentration of Ag nanoparticles in the PEM was controlled by repeating the ion-loading/reduction cycle. The subsequent annealing of the Ag/Ti-NBs-PEM nanocomposites yielded nanostructured crystalline Ag/Ti-NBs. Transmission electron microscopy (TEM) techniques (HRTEM, SAED) and x-ray powder diffraction (XRD) were employed to evaluate the morphological, structural and growth characteristics of the silver nanocrystallites in the Ag/Ti-NBs nanocomposites. The UV-vis photoactivity of the as-fabricated nanocomposites was monitored by the degradation of the cationic dye methylene blue (MB). An enhanced UV photo-efficiency was observed for the Ag/Ti-NBs nanocomposites compared with pure Ti-NBs. As-fabricated Ag(x)/Ti-NBs nanocomposites also exhibited visible photoactivity assisted by the near-field amplitudes of the localized surface plasmon resonance (LSPR) of the silver nanoparticles in the 1D nanocomposite.