Silver/Chitosan Antimicrobial Nanocomposites Coating for Medical Devices: Comparison of Nanofiller Effect Prepared via Chemical Reduction and Biosynthesis.

Medical devices have an essential part in healthcare system in recent years, such as usage of heart valves, several types of stents and implants devices in patients. However, bacterial infection of medical devices causes critical issues for patients due to attachment of bacteria and formation of biofilm onto the medical devices. Therefore, finding an effective antibacterial coating to prevent biofilm formation and infection is our goal. In this study, we developed silver/chitosan nanocomposites for antimicrobial coating system by chemical and green methods using sodium borohydride and linden extract, respectively. Silver is known as a strong inorganic antimicrobial agent to kill bacteria by inactivating enzymes and dysfunction bacterial cell membranes. By immobilizing silver nanoparticles on chitosan biopolymer can prevent agglomeration of nanoparticles, besides it can improve the biocompatibility. We characterized properties of our silver chitosan nanocomposites samples using particle size distribution, ultraviolet-visible spectroscopy, X-ray diffraction analysis and scanning electron microscopy. Effective antimicrobial film preventing biofilm formation on medical devices was designed. Antimicrobial testing confirmed antimicrobial properties however variable for each type of nanosilver.

Colloidal stability of phytosynthesised gold nanoparticles and their catalytic effects for nerve agent degradation.

Herein, Tilia sp. bract leachate was used as the reducing agent for Au nanoparticles (Au NPs) phytosynthesis. The colloidal properties of the prepared Au NPs were determined to confirm their stability over time, and the NPs were then used as active catalysts in soman nerve agent degradation. The Au NPs characterisation, reproducibility and stability studies were performed under transmission electron microscopy, ultraviolet visible spectroscopy and with ζ-potential measurements. The reaction kinetics was detected by gas chromatography coupled with mass spectrometry detector and solid-phase micro-extraction to confirm the Au NPs applicability in soman hydrolysis. The 'green' phytosynthetic formation of colloidal crystalline Au NPs with dominant quasi-spherical shape and 55 ± 10 nm diameter was successfully achieved, and there were no significant differences in morphology, ζ-potential or absorbance values observed during the 5-week period. This verified the prepared colloids' long-term stability. The soman nerve agent was degraded to non-toxic substances within 24 h, with 0.2156 h-1 reaction rate constant. These results confirmed bio-nanotechnology's great potential in preparation of stable and functional nanocatalysts for degradation of hazardous substances, including chemical warfare agents.

Crucial cytotoxic and antimicrobial activity changes driven by amount of doped silver in biocompatible carbon nitride nanosheets.

The use of Ag-modified nanomaterials continues to attract attention in biological contamination control, their potential cytotoxicity is often overlooked. Herein, biocompatible carbon nitride is modified with 1 and 5 wt.% Ag and effects of different nanomaterial dose and Ag content on antimicrobial activity and cytotoxicity is studied. Pure Ag nanoparticles and AgNO3 is tested for comparison, together with ten bacterial strains including pan-resistant Pseudomonas aeruginosa. Cytotoxicity is then investigated in three adherent and two suspension human cell lines, and results confirm that cancer adherent cell lines are the most immune lines and human cervical adenocarcinoma cells (HeLa) are more resilient than human lung adenocarcinoma cells (A549). The HeLa remains over 90 % viable even after 24 -h treatment with the highest concentration of 5%Ag/g-C3N4 (300 mg L-1) while A549 sustained viability only up to 100 mg L-1. Higher concentrations then induce cytotoxicity and A549 cell viability decreases. Our results show the importance of complementary testing of cytotoxicity by LIVE/DEAD assay using flow cytometry with more different human cell lines, which might be less immune to tested nanomaterials than HeLa and A549. Combined controls of new antibacterial agent activity tests then provide increased knowledge of their biocompatibility.

Phytosynthesis of Ag, ZnO and ZrO2 Nanoparticles Using Linden: Changes in Their Physical-Chemical Nature Over Time.

Bionanotechnology provides many new methods and protocols in nanomaterial preparation. One of these special new chemical methods is phytosynthesis. The application of biological processes in living organisms such as bacteria, fungi and higher plants contributes to rapid and easy formation of metallic nanoparticles. These nanoparticles present a promising future in heterogeneous catalysis and medicine, and here we focus on phytosynthesis of Ag, ZnO and ZrO2 nanoparticles using leachate from the linden plant. Nanoparticle activity in liquid is an important aspect of their behavior, and we investigated nanoparticles ζ-potential and monitored their particle size by dynamic light scattering during the period of three months. Transmission electron microscopy then determined shape and morphology, with results confirming their spherical shape and average size in tens and hundreds of nanometers. The amount of metals was estimated in tens of mg L-1 and the different nanoparticle sizes obtained by dynamic light scattering and transmission electron microscopy are discussed. The nanoparticles were tested against 4 human pathogens using minimum inhibitory concentration to investigate their antimicrobial potential. Only Ag nanoparticles provided antibacterial properties against Escherichia coli and Pseudomonas aeruginosa; with the remaining nanoparticles having no antibacterial effect on the four tested pathogens. All studied phenomena are related to nanoparticle concentration and their surface charge, and therefore ζ-potential and other physical and chemical properties are important in ascertaining positive and negative aspects of metallic nanoparticles in future applications and related research.

Ag-AgCl Nanoparticles Fixation on Electrospun PVA Fibres: Technological Concept and Progress.

Polymer-metal based material with unique 3D structure is an attractive substrate for the development of biomedical applications. A novel preparation of the composite from polymer fibres and silver nanoparticles has been designed through: (1) preparation of silver nanoparticles by phytosynthesis and (2) incorporation of these nanoparticles in a fibrous membrane prepared by electrospinning. The nanoparticle biosynthesis was performed in a pure environmental-friendly, easy, static, bottom-up in vitro regime using Tilia sp. leachate. TEM and XRD depict the formation, stabilisation and encapsulation of crystalline silver (14 ± 9 nm) nanoparticles (NPs) in one simple step with low tendency to aggregate. We achieved successful incorporation in the uniform electrospun 221 ± 24 nm poly(vinylalcohol) fibres, and this confirms the possibility of its use in the biomedical field. Both SEM with EDX and TEM analysis determined fibre uniformity with the presence of silver NPs, and ICP-AES confirmed the relatively similar metal concentration throughout the triplicate measurement of fibre structures on the 2 × 2 cm area in the following manner: 0.303 ± 0.018 wt. %, 0.282 ± 0.017 wt. %, and 0.281 ± 0.017 wt. %. Our hypothesis is based on previously verified preparation of active silver NPs and the easily prepared PVA electrospun fibres which act as a water soluble matrix. The simple methodology of incorporating biosynthetically prepared NPs in the PVA fibers highlights the effectiveness of this material, with simple release from water-soluble PVA and final activation of the prepared NPs.

From biotechnology principles to functional and low-cost metallic bionanocatalysts.

Chemical, physical and mechanical methods of nanomaterial preparation are still regarded as mainstream methods, and the scientific community continues to search for new ways of nanomaterial preparation. The major objective of this review is to highlight the advantages of using green chemistry and bionanotechnology in the preparation of functional low-cost catalysts. Bionanotechnology employs biological principles and processes connected with bio-phase participation in both design and development of nano-structures and nano-materials, and the biosynthesis of metallic nanoparticles is becoming even more popular due to; (i) economic and ecologic effectiveness, (ii) simple one-step nanoparticle formation, stabilisation and biomass support and (iii) the possibility of bio-waste valorisation. Although it is quite difficult to determine the precise mechanisms in particular biosynthesis and research is performed with some risk in all trial and error experiments, there is also the incentive of understanding the exact mechanisms involved. This enables further optimisation of bionanoparticle preparation and increases their application potential. Moreover, it is very important in bionanotechnological procedures to ensure repeatability of the methods related to the recognised reaction mechanisms. This review, therefore, summarises the current state of nanoparticle biosynthesis. It then demonstrates the application of biosynthesised metallic nanoparticles in heterogeneous catalysis by identifying the many examples where bionanocatalysts have been successfully applied in model reactions. These describe the degradation of organic dyes, the reduction of aromatic nitro compounds, dehalogenation of chlorinated aromatic compounds, reduction of Cr(VI) and the synthesis of important commercial chemicals. To ensure sustainability, it is important to focus on nanomaterials that are capable of maintaining the important green chemistry principles directly from design inception to ultimate application.