Current Nanomaterials - Volume 4, Issue 1, 2019

Background: Within the healthcare industry, including the care of chronic wounds, the challenge of antimicrobial resistance continues to grow. As such, there is a need to develop new treatments that can reduce the bioburden in wounds. Objective: The present study is focused on the development of polyaniline (PANI) / chitosan (CH) nanofibrous electrospun membranes and evaluates their antibacterial properties. Methods: To this end, experimental design was used to determine the electrospinning windows of both pure chitosan and PANI/CH blends of different ratios (1:3, 3:5, 1:1). The effect of key environmental and process parameters (relative humidity and applied voltage) was determined, as well as the effect of the PANI/CH ratio in the blend and the molecular interactions between PANI and chitosan that led to jet stability. Results: The nanofibrous mats were evaluated regarding their morphology and antibacterial effect against model gram positive and gram negative bacterial strains, namely B. subtilis and E. coli. High PANI content mats show increased bactericidal activity against both bacterial strains. Conclusion: The blend fibre membranes combine the materials’ respective properties, namely electrical conductivity, biocompatibility and antibacterial activity. This study suggests that electrospun PANI/CH membranes are promising candidates for healthcare applications, such as wound dressings.

Background: Nanosystems based on PEG-PLGA copolymer have attracted increasing interest in several biomedicine fields, due to their unique properties. Commonly, PEG-PLGA copolymer was used to formulate nanoparticles (NPs) for drug delivery applications. Only recently, the engineering of polymeric nanofibrous membrane able to be use like drug nanocarrier was investigated. Objective: The goal of this work is the development of two new drug delivery systems based on PEGylated-PLGA nanofibrous scaffolds, obtained by electrospinning deposition, simultaneous loaded with: i) silibinin, a therapeutic agent, ii) Au/Ag and iii) non-toxic Fe2O3 magnetic nanoparticles. Another interest aspect of the present work regards how the morphological structure can influence the drug release which has been fine-tuned by two external stimuli: a light source and a magnetic field. Methods: Noble metal nanocolloids were prepared in water by the pulsed laser ablation technique. The PEG-PLGA@Au/Ag-SLB added with Fe2O3-PVA nanofibers were fabricated by the electrospinning deposition method. Results: The use of “Surface Plasmon Resonance”-mediated localized photothermal effect, determined by the nanoparticles resonant absorption of visible radiation, allows to these systems to be able to employ for photothermal drug delivery therapies in proximity of tumor cells. All data obtained about the fiber scaffolds are compared to NPs based on the same PEG-PLGA copolymer, loaded with silibinin, Fe2O3 and Au/Ag nanoparticles alternatively. Nanofibers respects to NPs, showed interesting sustained responsive silibinin release for at least 60 h, without the burst effect. A diffusion-based theoretical model approach allowed to precisely describe the release mechanism. Conclusion: The effective and controlled silibilin drug release, upon application of either light irradiation or magnetic field for a definite time interval, has been demonstrated. Under the light stimulus, the fiber-shaped nanosystem reached a cumulative drug release value as high as 70% in the long time. On the overall, the information obtained could be useful to design suitable “on demand” nanocomposites in view of a therapeutic treatments protocol that requires a fast pharmacological action.

Background: Polymers play a key-role in the drug delivery technology. They allow for the controlled release of therapeutic agents under an external stimulus if a sensitive segment is suitable incorporated in the polymer matrix. Actually, polymer capsules containing noble metal nanostructures are regarded as promising light-responsive drug carriers. Among polymers, poly(methacrylic acid), PMA, offers manifold advantages: i) solubility in water, ii) coordination ability for Ag-Au nanoparticles, and iii) ability to act as capping agent. However, the preparation of Ag/PMA nanocolloids involves complex procedures the use of reagents with severe environmental impact. Objective: The goal of this work is to develop Ag/PMA nanocolloids for the controlled release of the encapsulated therapeutic agent (Sorafenib Tosylate) through a simple and cost effective synthesis process and the use of biocompatible, implantable materials. The light- and heat-responsiveness of fibrous scaffolds of Ag/PMA nanocolloids produced by electrospinning is investigated and compared with that of Ag/PMA nanocolloids. Methods: The goal of this work is to develop Ag/PMA nanocolloids for the controlled release of the encapsulated therapeutic agent (Sorafenib Tosylate) through a simple and cost effective synthesis process and the use of biocompatible, implantable materials. The light- and heat-responsiveness of fibrous scaffolds of Ag/PMA nanocolloids produced by electrospinning is investigated and compared with that of Ag/PMA nanocolloids. Results: In both the investigated systems, Ag/PMA nanocolloids and electrospun scaffolds of Ag/PMA nanocolloids, the drug release is significantly favored by the considered stimuli. Upon heat stimulus, Ag/PMA nanocolloids provide greater cumulative drug release with respect to the electrospun scaffold. Conversely, upon light stimulus, the scaffold is able to release a larger amount of Sorafenib at a faster rate, thanks to the Ag-mediated laser irradiation heating effect. Conclusion: The electrospun fibrous scaffold of Ag/PMA nanocolloids is demonstrated to be an efficient system for the remotely-triggered delivery of drug in a target area. The values of its loading efficiency (60%) and drug content (5.5%) are comparable to the ones obtained from amphiphilic copolymer structures prepared via complex chemical procedures with the use of toxic solvents and surfactant to stabilize the nanocolloids.

Background: Methods for obtaining the hybrids of multi-wall carbon nanotubes (MWCNTs) and rare earths are in progress. Such composites may possess luminescent properties, which could be of interest for various areas, in particular, medicine (imaging), engineering (fluorescent polymers, LED and relative materials), among other applications. Lanthanide oxides, additionally, can serve as catalysts for MWCNTs formation and catalysts of several organic reactions. Objective: The goal of this work is to obtain the composites of MWCNTs with strontium aluminate, doped with several lanthanides (Eu, Ce, La, Nd, and Sm), via the spray pyrolysis method and to study the properties of the formed hybrids. Methods: The spray pyrolysis method in the temperature range from 780 to 850oC, starting from toluene as a carbon source and ferrocene as a catalyst precursor. SrAl12O19 doped with rare-earths were added to carbon matter in the ultrasonic field. Results: Among various structures, the forest-like nanostructures have been observed in some cases. The formed coated carbon nanotubes possess fluorescent properties due to the attachment of lanthanide- doped ceramic compound (SrAl12O19) to their surface, allowing the emission control for each dopant: yellow (Nd2O3), blue (Eu2O3 and Sm2O3), intense orange (La2O3), light orange (Ce2O3). Conclusion: MWCNTs decorated with strontium aluminate (SrAl12O19), doped with a series of lanthanide oxides (Nd2O3, Eu2O3, La2O3, Ce2O3, Sm2O3), were obtained by the spray pyrolysis technique on the surface of optical fibers. Lanthanum- and cerium-containing coatings were found to show a better deposition on the MWCNTs surface, exhibiting uniform coating. MWCNTs, coated with Nd-, Ce-, and Eu-doped SrAl12O19 were shown to reveal the best conductive properties.

Background: Metallic–dielectric plasmonic nanoparticles have recently aroused great interest in view of many and novel technological applications, based on the interaction between light and matter under intense field conditions, in nonlinear integrated photonics and opto-fluidics, thanks to the possibility of tuning their electronic and optical properties through a fine control of the synthesis parameters and their nanoparticles under a high-power laser, like the one used during z-scan measures. Objective: The goal of this work is the study of nonlinear optical properties (as nonlinear refraction, scattering, two-photon absorption, optical limiting) of colloids synthesized in different liquid media by Pulsed laser ablation in liquids (PLAL), which is a photo-assisted synthesis technique ensuring the formation of stable, contaminant-free colloids directly during the ablation process. Methods: Noble metal nanoparticles, metal oxides hybrid nanostructures and silicon-based nanomaterials, were prepared by nanosecond and picosecond PLAL technique, in different media. The third-order nonlinear optical (NLO) properties have been studied by the use of a single beam z-scan technique with Q-switched frequency doubled Nd:YAG laser (λ=532 nm) at 5 ns pulse. Results: 1) A good stability of the PLAL nanocolloids under a high laser power; 2) the limiting threshold reduction inducted by the Ag-Au nanoparticles, the increase of the NLO absorption coefficient β, the reduction of the transmittance/scattering signal and the presence of a pronounced asymmetry of the peak/valley profile of the metal decorated metal oxide nanomaterials compared to the separately produced components. Conclusion: An intriguing coupling between the nature of the optical limiting response and the nanostructures rearrangement upon intense field conditions, explaining z-scan data by a classical approach able to account for the nanoparticles asymmetry and plasmonic effects, are the main results found.

Background: Nanoheterostructures of ZnFe2O4–ZnO is a potential functional material synthesized by various complicated synthesis processes. However, most of the processes are not at all cost effective because these generally require high-temperature treatment as well as long reaction time and complicated experimental procedure. Thus, a simple, low cost and highly efficient synthesis process is still highly required. Objective: The aim of the present study is to synthesize ZnFe2O4–ZnO nanoheterostructures by a simple solution process vis-à-vis to characterize the structural and optical properties of the sample. Methods: Nanoheterostructures of ZnFe2O4 decorated on ZnO nanorods (ZFZO) have been synthesized by two-step low-temperature solution process in the presence of hydrazine hydrate. Results: X-ray diffraction study showed the presence of hexagonal ZnO and cubic ZnFe2O4 spinel. Transmission electron microscopic analysis confirmed the formation of nanoheterostructures of ZnFe2O4 decorated on ZnO nanorods. The optical property of the sample was characterized by UVVisible spectroscopy. Moreover, the oxidation states of the elements were examined by X-ray photoelectron spectral studies. A probable formation mechanism of the nanoheterostructures was drawn. Conclusion: This simple solution based synthesis process is found to be an easy and cost- effective synthesis strategy as realized from the characterizations of structural and functional properties of the synthesized samples of ZnFe2O4–ZnO nanoheterostructures.