Rasha M. Abdel-Rahman

Green synthesis of hyaluronan fibers with silver nanoparticles

The application of green chemistry in the nano-science and technology is very important in the area of the preparation of various materials. In this work, an eco-friendly chemical method was successfully used for the preparation of hyaluronan fibers containing silver nanoparticles (AgNPs). Thus, hyaluronic acid (HA) was dissolved in an aqueous solution of sodium hydroxide to prepare a transparent solution, which was used for the preparation of fibers by a wet-spinning technique. Consequently, silver nanoparticles inside the fiber were prepared. Different parameters affecting the preparation of final product, such as concentration of silver nitrate, hyaluronan fiber concentration, time and temperature of the reaction, pH of the reaction mixture, were studied. AgNPs were confirmed by transmission electron microscopy (TEM), X-ray diffraction (XRD), two-dimensional X-ray scattering (2D SWAXS), UV/Vis spectroscopy, inductively coupled plasma optical emission spectrometry (ICP OES) and scan electron microscopy (SEM). Mechanical properties of prepared fibers were also measured.

Antibacterial activity and cell viability of hyaluronan fiber with silver nanoparticles

Silver has been used since time immemorial in different chemical form to treat burns, wounds and several different infections caused by pathogenic bacteria, advancement of biological process of nanoparticles synthesis is evolving into a key area of nanotechnology. The current study deals with the green synthesis, characterization, and evaluation of the biological activity and cell viability of hyaluronan fibers with incorporated silver nanoparticles (HA-Ag NPs). Hyaluronan fiber was prepared by the dissolving of sodium hyaluronate (HA) in aqueous alkaline solution to prepare a transparent solution, which was used for the preparation of fibers by a wet-spinning technique. Consequently, hyaluronan fiber was used as capping and stabilizing agent for the preparation of fibers with silver nanoparticles. HA-Ag NPs were confirmed by transmission electron microscopy, dynamic light scattering, UV/VIS spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, thermal analysis, nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. HA-Ag NPs showed high antibacterial activity of against Staphylococcus aureus and Escherichia coli. Cell viability tests indicated that hyaluronan, hyaluronan fibers and hyaluronan fibers with silver nanoparticles were non-toxic on the cell growth. Two different particles size of Ag NPs (10, 40 nm) had not any toxicity till the concentration limit. These tests were performed using mouse fibroblast cell line 3T3.

Antibacterial cotton fabrics treated with core-shell nanoparticles.

Multifinishing treatment of cotton fabrics was carried out using core-shell nanoparticles that consists of silver nanoparticles (Ag(0)) as core and chitosan-O-methoxy polyethylene glycol (CTS-O-MPEG) as shell. The synthesized (Ag(0)-CTS-O-MPEG) core-shell nanoparticle was applied to cotton fabrics using the conventional pad-dry-cure method. The finished fabrics were examined for their morphological features and surface characteristics by making use of scanning electron microscope (SEM-EDX), which reveals the well dispersion of (Ag(0)-CTS-O-MPEG) core-shell nanoparticles on cotton fabrics. Factors affecting the treatment such as core shell nanoparticles, citric acid (CA) concentration as well as curing temperature were studied. The treated fabrics, at optimum condition of 1% core shell nanoparticles, 5% citric acid, drying at 80°C, curing at 160°C for 2 min, showed excellent antibacterial activity against Gram-negative Escherichia coli (E. coli) and Gram-positive bacteria Staphylococcus aureus (S. aureus), even after 20 washing cycles in addition to an enhancement in crease recovery angles (CRA) along with a slight improvement in tensile strength (TS).

Chitin and chitosan from Brazilian Atlantic Coast: Isolation, characterization and antibacterial activity

Chitin and chitosan were obtained by chemical treatments of shrimp shells. Different particle sizes (50-1000 μm) of the raw material were used to study their effect on size distribution, demineralization, deproteinization and deacetylation of chitin and chitosan isolation process. The particle size in the range of 800-1000 μm was selected to isolate chitin, which was achieved by measuring nitrogen, protein, ash, and yield %. Hydrochloric acid (5%, v/v) was optimized in demineralization step to remove the minerals from the starting material. Aqueous solution of sodium hydroxide (5%, w/v) at 90 °C for (20 h) was used in deproteinization step to remove the protein. Pure chitin was consequently impregnated into high concentration of sodium hydroxide (50%) for 3.5 h at 90 °C to remove the acetyl groups in order to form high pure chitosan. The degree of deacetylation (DDA) of chitosan was controlled and evaluated by different analytical tools. The chemical structure of chitin and chitosan was confirmed by elemental analysis, ATR-FTIR, H/C NMR, XRD, SEM, UV-Vis spectroscopy, TGA, and acid-base titration. The isolated chitin and chitosan from shrimp shell showed excellent antibacterial activity against Gram (-ve) bacteria (Escherichia coli) comparing with commercial biopolymers.

Synthesis, characterization and antibacterial activity of new fluorescent chitosan derivatives

The present work aims to the development of innovative new derivatives of chitosan that can be used for medical applications. This innovation is based on the synthesis and characterization of chitosan-g-aminoanthracene derivatives. Thus, N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT) reacted with chitosan by the following steps: at first, cyanuric chloride reacted with 9-aminoanthracene to obtain N-(anthracen-9-yl)-4,6-dichloro-[1,3,5]-triazin-2-amine (AT), then the AT reacted with chitosan to obtain (CH-g-AT). The final product of CH-g-AT was separated, purified and re-crystallized by dioxane. The structure of the prepared chitosan derivatives was confirmed by FTIR-ATR, solid-NMR, TGA, X-RD, and DSC. The new chitosan derivatives showed fluorescence spectra in liquid and in solid state as well. CH-g-AT showed also high antibacterial activity against gram -ve species (Escherichia coli).

Wound Dressing based on Chitosan/hyaluronan/Nonwoven Fabrics: Preparation, Characterization and Medical Applications

Thin layers of chitosan (positively charged)/sodium hyaluronate (negatively charged)/nonwoven fabrics were constructed by polyelectrolyte multilayer pad-dry-cure technique. Pure chitosan (CS) was isolated from shrimp shell and immobilized onto nonwoven fabrics (NWFs) using citric acid (CTA) as cross linker and solvent agents through a pad-dry-cure method. The prepared thin layer of chitosan citrate/nonwoven fabrics (CSCTA/NWFs) were consequently impregnated with hyaluronan (CSCTA/HA/NWFs) in the second path through a pad-dry-cure method. Chitosan/hyaluronan/nonwoven fabrics wound dressing was characterized by different techniques such as FTIR-ATR, TGA and SEM. The antibacterial activity and the cytotoxicity of the dressing sheets were evaluated against Escherichia coli (E. coli) and Streptococcus aureus (S. aureus), mouse fibroblast (NIH-3T3) and keratinocytes (HaCaT) cell lines, respectively. The cell-fabrics interaction was also investigated using fluorescence microscope, based on live/dead staining assay of 3T3 cells. The healing properties of the new wound dressing were evaluated and compared with the control sample.

Wound healing of different molecular weight of hyaluronan; in-vivo study

Recruitment of cells and mediators is altered during impaired wound healing, thereby delaying this process. To overcome this problem, the correlation of wound healing in older rats, and the impact of different molecular weight of hyaluronan without silver nanoparticles; (low-HA1), (High-HA2), (Medium- HA3) and with silver nanoparticles (High-HA4) is investigated. The superior HA were selected to be further investigated onto diabetic wounds. Our results pointed to a marked deficiency in wounds granulation in older rats, which was accompanied with impairment of healing process. In older rats group treated with HA2 or HA4, granulation and dermal construction were improved. Furthermore, the number of pathogenic bacteria on wounds was declined throughout the first 24h by HA2 and HA4. The wound size in HA4-treated older rats was significantly smaller than that in other HA1, HA2 or HA3-treated older ones. Also, diabetes impaired the level of inflammatory cytokine, in diabetic model. On contrary, HA4 was found to normalize the level of inflammatory cytokine, in the diabetic model. Furthermore, HA4 was found to recover all oxidative and toxicity markers in diabetic models. This data confirms the critical role of HA4 to improve granulation and inflammatory mediators in impaired older and diabetic rat wound healing.