Light-induced antibacterial activity of electrospun chitosan-based material containing photosensitizer.

Increasing antimicrobial resistance requires the development of novel materials and approaches for treatment of various infections. Utilization of photodynamic therapy represents an advanced alternative to antibiotics and metal-based agents. Here, we report the fabrication of electrospun material that possesses benefits of both topical antimicrobial and photodynamic therapies. This material combines chitosan, as a biocompatible polymer, and a second generation photosensitizer. The incorporation of photosensitizer doesn't affect the material morphology and its nearly uniform distribution in fibers structure was observed by confocal Raman microscopy. Owing to photosensitizer the prepared material exhibits the light-induced and spatially limited antimicrobial activity that was demonstrated against Staphylococcus aureus, an important etiological infectious agent. Such material can be potentially used in antibacterial therapy of chronic wounds, infections of diabetic ulcers, and burns, as well as rapidly spreading and intractable soft-tissue infections caused by resistant bacteria.

Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.

An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1µm. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions.

Effect of layer-by-layer electrostatic assemblies on the surface potential and current voltage characteristic of metal-insulator-semiconductor structures.

In the present Article, the Kelvin probe method for surface potential measurement is introduced to study polyelectrolyte multilayer coatings deposited on silicon plates. Metal-insulator-semiconductor (MIS) structures with polyelectrolyte layers as insulator were fabricated. The polyelectrolyte layer deposition on the surface of silicon plates led to a change of the current-voltage characteristics connected with resistance changes of the MIS structures. Poly(ethylenimine) (PEI) monolayer formation resulted in resistance decrease, and the following increase of the polyelectrolyte layer number led to MIS structure resistance increase. The results are interpreted as an interplay between accumulation of majority carriers (electrons) near the semiconductor surface and resistance increase due to insulating polyelectrolyte adsorption, and both effects can be discriminated by varying the polyelectrolyte layer thickness.

Polyelectrolyte/magnetite nanoparticle multilayers: preparation and structure characterization.

Polyelectrolyte composite planar films containing a different number of iron oxide (Fe3O4) nanoparticle layers have been prepared using the layer-by-layer adsorption technique. The nanocomposite assemblies were characterized by ellipsometry, UV-vis spectroscopy, and AFM. Linear growth of the multilayer thickness with the increase of the layer number, N, up to 12 reflects an extensive character of this parameter in this range. A more complicated behavior of the refractive index is caused by changes in the multilayer structure, especially for the thicker nanocomposites. A quantitative analysis of the nanocomposite structure is provided comparing a classical and a modified effective medium approach taking into account the influence of light absorption by the Fe3O4 nanoparticles on the complex refractive index of the nanocomposite and contributions of all components to film thickness. Dominant influence of co-adsorbed water on their properties was found to be another interesting peculiarity of the nanocomposite film. This effect, as well as possible film property modulation by light, is discussed.