Multidrug resistance of the pathogenic microorganisms to the antimicrobial drugs has become a major impediment toward successful diagnosis and management of infectious diseases. Recent advancements in nanotechnology-based medicines have opened new horizons for combating multidrug resistance in microorganisms. In particular, the use of silver nanoparticles (AgNPs) as a potent antibacterial agent has received much attention. The most critical physico-chemical parameters that affect the antimicrobial potential of AgNPs include size, shape, surface charge, concentration and colloidal state. AgNPs exhibits their antimicrobial potential through multifaceted mechanisms. AgNPs adhesion to microbial cells, penetration inside the cells, ROS and free radical generation, and modulation of microbial signal transduction pathways have been recognized as the most prominent modes of antimicrobial action. On the other side, AgNPs exposure to human cells induces cytotoxicity, genotoxicity and inflammatory response in human cells in a cell-type dependent manner. This has raised concerns regarding use of AgNPs in therapeutics and drug delivery. We have summarized the emerging endeavors that address current challenges in relation to safe use of AgNPs in therapeutics and drug delivery platforms. Based on research done so far, we believe that AgNPs can be engineered so as to increase their efficacy, stability, specificity, biosafety and biocompatibility. In this regard, three perspectives research directions have been suggested that include 1) synthesizing AgNPs with controlled physico-chemical properties, 2) examining microbial development of resistance towards AgNPs, and 3) ascertaining the susceptibility of cytoxicity, genotoxicity, and inflammatory response to human cells upon AgNPs exposure.

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Mechanistic Basis of Antimicrobial Actions of Silver Nanoparticles.

pH-sensitive hydrogels play an important role in controlled drug release applications and have the potential to impact the management of wounds. In this study, we report the fabrication of novel carboxylated agarose/tannic acid hydrogel scaffolds cross-linked with zinc ions for the pH-controlled release of tannic acid. The resulting hydrogels exhibited negligible release of tannic acid at neutral and alkaline pH and sustained release at acidic pH, where they also displayed maximum swelling. The hydrogels also displayed favorable antibacterial and anti-inflammatory properties, and a lack of cytotoxicity toward 3T3 fibroblast cell lines. In simulated wound assays, significantly greater cell migration and proliferation was observed for cells exposed to tannic acid hydrogel extracts. In addition, the tannic acid hydrogels were able to suppress NO production in stimulated human macrophages in a concentration-dependent manner, indicating effective anti-inflammatory activity. Taken together, the cytocompatibilit...

Antibacterial and Anti-Inflammatory pH-Responsive Tannic Acid-Carboxylated Agarose Composite Hydrogels for Wound Healing.

The Guided Bone Regeneration (GBR) treatment concept advocates that regeneration of osseous defects is predictably attainable via the application of occlusive membranes, which mechanically exclude non-osteogenic cell populations from the surrounding soft tissues, thereby allowing osteogenic cell populations originating from the parent bone to inhabit the osseous wound. The present review discusses the evolution of the GBR biological rationale and therapeutic concept over the last two decades. Further, an overview of the GBR research history is provided with specific focus on the evidence available on its effectiveness and predictability in promoting the regeneration of critical size cranio-maxillo-facial defects, the neo-osteogenesis potential and the reconstruction of atrophic alveolar ridges before, or in conjunction with, the placement of dental implants. The authors conclude that future research should focus on (a) the investigation of the molecular mechanisms underlying the wound healing process following GBR application; (b) the identification of site and patient related factors which impact on the effectiveness and predictability of GBR therapy and (c) the evaluation of the pathophysiology of the GBR healing process in the presence of systemic conditions potentially affecting the skeletal system.To cite this article:Retzepi M, Donos N. Guided Bone Regeneration: biological principle and therapeutic applications.Clin. Oral Impl. Res. 21, 2010; 567-576.doi: 10.1111/j.1600-0501.2010.01922.x.

Guided Bone Regeneration: biological principle and therapeutic applications

Hydrogel wound dressings for bioactive treatment of acute and chronic wounds

Removal of colorants from wastewater: A review on sources and treatment strategies

Biocompatible and biodegradable poly(Tannic Acid) hydrogel with antimicrobial and antioxidant properties.

The salicylic acid salts of fully substituted mono(4-fluorobenzyl)spirocyclotriphosphazenes (10–15) were prepared. The structures of these phosphazenium salts (10a–15a) were determined by elemental analyses, FTIR and 1H, 13C{1H}, 31P{1H} NMR techniques. The crystal structure of 14a was verified by X-ray diffraction analysis. The thermal properties of the salts were investigated using TG/DTA and DSC instruments. The results obtained from DSC indicated that the melting temperatures and latent heats of the compounds were in the ranges of 107.76–143.04 °C and 41.64–69.73 J g−1, respectively. The thermal stabilities of the phosphazenium salts (10a–15a) are found to be different, but they have a similar decomposition mechanism. The compounds 14a and 15a exhibit noticeable cytotoxic activity against DLD-1 cancer cells, and they seem to be good candidates for being anticancer agents. All of the compounds have an antimicrobial effect on bacterial and yeast strains within the ranges of 312–625 µM (bacterial strains) and 19.5–312 µM (yeast strains). It is found that compounds 13a–15a were most effective against yeast strains. Moreover, interactions between the salts and pBR322 plasmid DNA show that 14a and 15a cleave the DNA and decrease the intensity of form I. BamHI and HindIII digestion results demonstrate that the compounds are not bound with G/G and A/A nucleotides, respectively.

Phosphorus–nitrogen compounds

Aptamer-functionalized magnetic graphene oxide nanocarrier for targeted drug delivery of paclitaxel

Synthesis, characterization and modification of Gum Arabic microgels for hemocompatibility and antimicrobial studies.

The present study was conducted to examine cytotoxic, apoptotic, and necrotic effects of silver nanoparticles (AgNPs) on MCF-7 cells. Colloidal AgNPs were fabricated in an alkaline pH environment via reduction of silver nitrate with hydroxylamine hydrochloride. The size of AgNPs was measured by atomic force microscopy (AFM), transmission electron microscopy (TEM), and dynamic light scattering. Zeta potential of AgNPs was determined by laser Doppler microelectrophoresis. After exposing MCF-7 cells to AgNPs for 24 h, cytotoxicity was measured by WST-1 assay. Apoptosis and necrosis in MCF-7 cells were detected by Annexin-V-FLUOS immunostaining and double staining of Hoechst dye with propidium iodide. In AFM and TEM analyses, the sizes of AgNPs varied from 16 nm to 20 nm. AgNPs were 80 nm in hydrodynamic diameter with a zeta potential of 38.2 mV. The WST-1 assay resulted in an IC50 value of 40 µg/mL. AgNPs caused apoptotic and necrotic effects in a dose-dependent manner. The apoptotic effect of AgNPs was marked up to a concentration of 80 µg/mL AgNPs. At higher concentrations, the apoptotic effect decreased while the necrotic effect became prominent. The results indicate that AgNPs with a zeta potential of 38.2 mV and hydrodynamic diameter of 80 nm can be used in vitro at concentrations of up to 40 µg/mL.

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Mustafa Türk

Papers

Biocompatible and biodegradable poly(Tannic Acid) hydrogel with antimicrobial and antioxidant properties.

Phosphorus–nitrogen compounds

Aptamer-functionalized magnetic graphene oxide nanocarrier for targeted drug delivery of paclitaxel

Synthesis, characterization and modification of Gum Arabic microgels for hemocompatibility and antimicrobial studies.

Silver nanoparticles: cytotoxic, apoptotic, and necrotic effects on MCF-7 cells