Polypyrrole-coated cellulose nanofibers: influence of orientation, coverage and electrical stimulation on SH-SY5Y behavior.

In the field of tissue engineering, much research has been devoted to the surface topography of conductive materials. However, less work has been carried out on how the electrical stimulation of such materials influences nerve regeneration. Here, we investigated the effect of electrical stimulation on randomly- and uniaxially-aligned polypyrrole-coated cellulose acetate butyrate (PPy/CAB) nanofibers. First, SEM revealed that the conducting PPy coverage resulted in dramatic changes to the nanofiber morphology. In turn, these changes led to an increase in the sample wettability. Fourier transform spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed the presence of a PPy layer. Second, human neuroblastoma cells (SH-SY5Y) were seeded on the PPy/CAB nanofibers and stimulated by 100 mV mm-1 at 1 Hz pulses in vitro. We demonstrated that either with or without this electrical stimulation both nanofiber alignment and PPy coverage had a strong influence on cell morphology and attachment. Moreover, fluorescence microscopy revealed that the cells stimulated on PPy/CAB had longer neurite outgrowth. Collectively, our results shed light on the combined effect of scaffold morphology and external stimulation on neuronal cell behavior.

Porphyrin­silver nanoparticles hybrids: Synthesis, characterization and antibacterial activity.

The preparation of light-activated hybrid antibacterial agent combining the porphyrin molecules, bound to the silver nanoparticles (AgNPs) surface is reported. AgNPs were synthesized by N-methyl-2-pyrrolidone-initiated reduction without additional reducing agents. The chemical structure of protoporphyrin IX was modified with the aim to introduce thiol groups. The size distribution and shape features of AgNPs were checked using TEM and HRTEM microscopies. The introduction of thiol groups into the porphyrin was proved by IR spectroscopy. The AgNPs-porphyrin binding was performed in solution and confirmed by fluorescence quenching, Raman spectroscopy and energy-filtered transmission electron microscopy (EFTEM). The antibacterial tests were performed against S. epidermidis and E. coli upon to LED illumination and in the dark. The synergetic effect of AgNPs and porphyrin as well as light activation of the created antibacterial conjugates were observed.

Surface roughness in action - Cells in opposition.

Aim of this work is to study the interaction of krypton fluoride (KrF) excimer laser beam with a biopolymer and creation of new nanostructures with great potential for cell growth guidance. As a substrate we used biocompatible and biodegradable polymer polyhydroxybutyrate, which is frequently used in medicine and drug delivery system. Modification was carried out by KrF laser and method was also supplemented by treatment with Ar+ plasma. The changes in physico-chemical properties of surface layer were determined by goniometry, gravimetry and X-ray photoelectron spectroscopy (XPS). Morphological changes and roughness were observed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). Effect of laser treatment on the bulk material was studied by differential scanning calorimetry (DSC). Finally, the tests of mouse embryonic fibroblast (NIH 3T3) and human bone osteosarcoma (U-2 OS) cells' response was carried out on the selected samples. Modification of surface by laser with high number of pulses and fluence led to creation of surface layers with huge valleys and very high roughness. These structures were caused by extreme effect of ablation in combination with mass transfer. The results of the surface characterization will be useful for further research in the field of biopolymers structuring and modification, and may find a strong application in tissue engineering for single cell assays.

Surface characterization and antibacterial response of silver nanowire arrays supported on laser-treated polyethylene naphthalate.

Polymeric biomaterials with antibacterial effects are requisite materials in the fight against hospital-acquired infections. An effective way for constructing a second generation of antibacterials is to exploit the synergic effect of (i) patterning of polymeric materials by a laser, and (ii) deposition of noble metals in their nanostructured forms. With this approach, we prepared highly-ordered periodic structures (ripples) on polyethylene naphthalate (PEN). Subsequent deposition of Ag under the glancing angle of 70° resulted in the formation of self-organized, fully separated Ag nanowire (Ag NW) arrays homogenously distributed on PEN surface. Surface properties of these samples were characterized by AFM and XPS. Vacuum evaporation of Ag at the glancing angle geometry of 70° caused that Ag NWs were formed predominantly from one side of the ripples, near to the top of the ridges. The release of Ag+ ions into physiological solution was studied by ICP-MS. The results of antibacterial tests predetermine these novel structures as promising materials able to fight against a broad spectrum of microorganisms, however, their observed cytotoxicity warns about their applications in the contact with living tissues.

Cytotoxicity of Pd nanostructures supported on PEN: Influence of sterilization on Pd/PEN interface.

Non-conventional antimicrobial agents, such as palladium nanostructures, have been increasingly used in the medicinal technology. However, experiences uncovering their harmful and damaging effects to human health have begun to appear. In this study, we have focused on in vitro cytotoxicity assessment of Pd nanostructures supported on a biocompatible polymer. Pd nanolayers of variable thicknesses (ranging from 1.1 to 22.4nm) were sputtered on polyethylene naphthalate (PEN). These nanolayers were transformed by low-temperature post-deposition annealing into discrete nanoislands. Samples were characterized by AFM, XPS, ICP-MS and electrokinetic analysis before and after annealing. Sterilization of samples prior to cytotoxicity testing was done by UV irradiation, autoclave and/or ethanol. Among the listed sterilization techniques, we have chosen the gentlest one which had minimal impact on sample morphology, Pd dissolution and overall Pd/PEN interface quality. Cytotoxic response of Pd nanostructures was determined by WST-1 cell viability assay in vitro using three model cell lines: mouse macrophages (RAW 264.7) and two types of mouse embryonic fibroblasts (L929 and NIH 3T3). Finally, cell morphology in response to Pd/PEN was evaluated by means of fluorescence microscopy.

Antibacterial properties of modified biodegradable PHB non-woven fabric.

The antibacterial properties of poly(hydroxybutyrate) (PHB) non-woven fabric were explored in this study. The PHB was activated by plasma modification and subsequently processed with either immersion into a solution of nanoparticles or direct metallization. The wettability and surface chemistry of the PHB surface was determined. The thickness of the sputtered nanolayer on PHB fabric was characterized. It was found that plasma modification led to a formation of strongly hydrophilic surface, while the subsequent metallization by silver or gold resulted in a significantly increased water contact angle. Further, it was found that antibacterial activity may be controlled by the type of a metal and deposition method used. The immersion of plasma modified fabric into Ag nanoparticle solution led to enhanced antibacterial efficiency of PHB against Escherichia coli (E. coli). Direct silver sputtering on PHB fabric was proved to be a simple method for construction of a surface with strong antibacterial potency against both Escherichia coli (E. coli) and Staphylococcus epidermidis (S. epidermidis). We demonstrated the antibacterial activity of PHB fabric modified by plasma activation and consecutive selection of a treatment method for an effective antibacterial surface construction.

Silver Nanoparticles Stabilized Using Chitosan Films: Preparation, Properties and Antibacterial Activity.

In this work we present silver nanoparticles coated with chitosan films synthesized by a simple, environmentally friendly method. Silver nanoparticles were prepared and stabilized by reduction of silver nitrate with chitosan without addition of harmful reduction agents. The presence of silver nanoparticles in the solid films was studied by the X-ray diffraction spectroscopy and X-ray photoelectron spectroscopy. Solid films were dissolved and the solution was observed by the ultraviolet-visible spectroscopy and transmission electron microscopy. The amount of silver in the solid samples was studied by atomic absorption spectroscopy. Antibacterial activity of solid films with silver nanoparticles was tested by disc test on two bacterial strains, Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli. The presence of silver nanoparticles was confirmed both in solid film and in solution by the above mentioned methods. The films exhibited strong antibacterial activity against both bacterial strains. These films could be used as a wound dressing, antimicrobial packaging material or for long-term storage of silver nanoparticles for various applications.

Silver release and antimicrobial properties of PMMA films doped with silver ions, nano-particles and complexes.

Materials prepared on the base of bioactive silver compounds have become more and more popular due to low microbial resistance to silver. In the present work, the efficiency of polymethylmethacrylate (PMMA) thin films doped with silver ions, nanoparticles and silver-imidazole polymer complex was studied by a combination of AAS, XPS and AFM techniques. The biological activities of the proposed materials were discussed in view of the rate of silver releasing from the polymer matrix. Concentrations of Ag active form were estimated by its ability to interact with l-cysteine using electronic circular dichroism spectroscopy. Rates of the released silver were compared with the biological activity in dependence on the form of embedded silver. Antimicrobial properties of doped polymer films were studied using two bacterial strains: Staphylococcus epidermidis and Escherichia coli. It was found that PMMA films doped with Ag(+) had greater activity than those doped with nanoparticles and silver-imidazole polymeric complexes. However, the antimicrobial efficiency of Ag(+) doped films was only short-term. Contrary, the antimicrobial activity of silver-imidazole/PMMA films increased in time of sample soaking.

Striking antitumor activity of a methinium system with incorporated quinoxaline unit obtained by spontaneous cyclization.

A novel pentamethinium salt was synthesized with an unforeseen expanded conjugated quinoxaline unit directly incorporated into a pentamethinium chain. The compound exhibited high fluorescence intensity, selective mitochondrial localization, high cytotoxicity, and selectivity toward malignant cell lines, and resulted in remarkable in vivo suppression of tumor growth in mice.