Fluorescent Labeling of Hyaluronic Acid-Chitosan Nanocarriers by Protein-Stabilized Gold Nanoclusters

In medical research the visualization of drug carrier accumulation and release of the loaded drugs in vivo is an important field. In this work, two protein-stabilized gold nanoclusters (Au NCs) as effective fluorescent reporters (FRs) were investigated for labeling of biocompatible chitosan-modified hyaluronic acid based nanocarriers having two different structures. The colloid stability of the labeled carriers was studied by dynamic light scattering and Zeta potential measurements, while the changes in the fluorescence of the lysozyme- (LYZ) and bovine serum albumin (BSA)-stabilized Au NCs were analyzed by spectrofluorimetry and confocal fluorescent microscopy. We found that the labeling was effective with a wide range of marker:carrier mass ratios, and the fluorescence of the NCs and the colloid stability of the complexes were retained. Labeling during preparation and subsequent labeling were compared, and based on composition (nanocluster:carrier mass ratio) and structure of the complex systems we preferred the latter method, as it left the Au NCs free for further modifications. Considering both marker:carrier mass ratios and emission intensities, the LYZ-stabilized Au NCs proved to be better labels. The core-shell type carrier formulations showed increased fluorescence with LYZ-stabilized NCs, presumably from aggregation induced emission

Vitamin E-Loaded PLA- and PLGA-Based Core-Shell Nanoparticles: Synthesis, Structure Optimization and Controlled Drug Release

The (±)-α-Tocopherol (TP) with vitamin E activity has been encapsulated into biocompatible poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) carriers, which results in the formation of well-defined nanosized (d ~200–220 nm) core-shell structured particles (NPs) with 15–19% of drug loading (DL%). The optimal ratios of the polymer carriers, the TP active drug as well as the applied Pluronic F127 (PLUR) non-ionic stabilizing surfactant, have been determined to obtain NPs with a TP core and a polymer shell with high encapsulation efficiency (EE%) (69%). The size and the structure of the prepared core-shell NPs as well as the interaction of the carriers and the PLUR with the TP molecules have been determined by transmission electron microscopy (TEM), dynamic light scattering (DLS), infrared spectroscopy (FT-IR) and turbidity studies, respectively. Moreover, the dissolution of the TP from the polymer NPs has been investigated by spectrophotometric measurements. It was clearly confirmed that increase in the EE% from ca. 70% (PLA/TP) to ca. 88% (PLGA65/TP) results in the controlled release of the hydrophobic TP molecules (7 h, PLA/TP: 34%; PLGA75/TP: 25%; PLGA65/TP: 18%). By replacing the PLA carrier to PLGA, ca. 15% more active substance can be encapsulated in the core (PLA/TP: 65%; PLGA65/TP: 80%)

Synthesis and characterization of titanium dioxide based ternary nanocomposites for photocatalytic hydrogen production

Titanium dioxide based photocatalysts of different graphene oxide (GO) and silver nanoparticle (AgNP) content were prepared and tested in catalytic methanol reformation reaction. Aqueous suspensions of the composite solids obtained by heterocoagulation of alkaline exfoliated GO suspension and slightly acidic TiO2 suspension showed enhanced sedimentation rate at pH = 6.5- 7, when they contained less than 2 wt% graphene oxide. This enables easier catalyst recovery but the suspension needs to be stirred strongly during the catalytic run in order to achieve homogeneous light distribution within the reaction vessel. The catalytic runs were performed in 6 V/V% methanol/water mixture using 500 mg/L catalyst under UV-illumination. The activity of pure titanium dioxide (Degussa P25) continuously increases and reaches a saturation plateau after 150 min with an activity of 0.12 mmol H2/(h×gcat). Incorporation of GO into the titanium dioxide matrix by heterocoagulation method results in aggregated suspensions exhibiting an enhancement of the hydrogen evolution rate to the saturation value of 0.17 mmol H2/(h×gcat). Deposition of different amounts of AgNPs of different sizes onto the surface of titanium dioxide resulted in an even higher photocatalytic activity, reaching 0.25-0.29 mmol H2/(h×gcat). The combination of AgNP’s and GO platelets to obtain ternary TiO2 based catalysts has not shown any further increase of hydrogen generation rate