Riham R. Mohamed

Synthesis and Characterization of Carboxymethyl Chitosan Nanogels for Swelling Studies and Antimicrobial Activity

Nanogels of a binary system of carboxymethyl chitosan (CMCh) and poly- (vinyl alcohol) PVA, were successfully synthesized by a novel in situ process. They were also characterized by various analytical tools like Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and X-ray diffraction (XRD). They were studied for their unique swelling properties in water and different pH solutions. They were also investigated for their great ability to capture or isolate bacteria and fungi from aquatic environments.

Synthesis and characterization of antimicrobial crosslinked carboxymethyl chitosan nanoparticles loaded with silver.

Carboxymethyl chitosan (CMCh)-silver nanoparticle (Ag) hydrogels with high antibacterial activity against three Gram +ve bacteria (Staphylococcus aureus, Bacillus subtilis and Streptococcus faecalis), three Gram -ve bacteria (Escherichia coli, Pseudomonas aeruginosa and Neisseria gonorrhoeae) and a Candida albicans fungus were prepared. The in situ preparation reaction involved crosslinking of CMCh with epichlorohydrin in alkaline medium containing silver nitrate to yield silver nanoparticles loaded CMCh hydrogel giving pale brown or darker hydrogels when the silver content increases. FTIR spectroscopy, SEM and TEM were done for the prepared hydrogels. Silver nanoparticles hydrogels exhibited higher antimicrobial activity than virgin CMCh. TEM analysis showed the small size of the prepared hydrogels to be in the range of 9-16nm in size.

Synthesis, characterization and application of biodegradable crosslinked carboxymethyl chitosan/poly(vinyl alcohol) clay nanocomposites

Crosslinked poly(vinyl alcohol) (PVA)/carboxymethyl chitosan (CMCh) nanocomposites were synthesized using terephthaloyl diisothiocyanate crosslinker, in the presence of montmorillonite (MMT), in different ratios of the two matrices. Characterization of nanocomposites was performed using different analyses. Swelling behavior was studied in different buffered solutions. It was found that formation of crosslinked CMCh/PVA hydrogels increased the swellability. Metal ion adsorption has also been investigated. The results indicated that crosslinked CMCh adsorbs various metal ions much more than non crosslinked CMCh. Antimicrobial activity was examined against Gram positive bacteria, against Gram negative bacteria, and also against fungi. Results indicated that most of these nanocomposites exhibited good antimicrobial potency. Degradation study was carried out in Simulated Body Fluid (SBF) for different time periods in order to find out degradation index (Di). Results showed that weight loss of most of the nanocomposites increased as a function of incubation time.

Novel Antimicrobial Organic Thermal Stabilizer and Co-Stabilizer for Rigid PVC

Biologically active N-benzoyl-4-(N-maleimido)-phenylhydrazide (BMPH) was synthesized and its structure was confirmed by elemental analysis and various spectral tools. It was examined as a thermal stabilizer and co-stabilizer for rigid poly (vinyl chloride) at 180 °C in air. Blending BMPH with reference samples in different ratios greatly lengthens the thermal stability value and improves the extent of discoloration of PVC. TGA confirmed the improved stability of PVC in presence of the investigated organic stabilizer. GPC measurements were done to investigate the changes occurred in the molecular masses of the degraded samples of blank PVC and PVC in presence of the novel stabilizer. BMPH showed good antimicrobial activity towards two kinds of bacteria and two kinds of fungi.

Synthesis and characterization of some novel antimicrobial thiosemicarbazone O-carboxymethyl chitosan derivatives

Three novel thiosemicarbazone O-carboxymethyl chitosan derivatives were obtained via a condensation reaction of thiosemicarbazide O-carboxymethyl chitosan with o-hydroxybenzaldehyde, p-methoxybenzaldehyde, and p- chlorobenzaldehyde respectively. Their structures were characterized by elemental analysis, FTIR, (13)C NMR and X-ray diffraction. The antimicrobial behaviors of the prepared derivatives against three types of bacteria Staphylococcus aureus (S. aureus, RCMBA 2004), Bacillus subtilis (B. subtilis, RCMBA 6005), and Escherichia coli (E. Coli, RCMBA 5003) and three crops-threatening pathogenic fungi Aspergillus fumigatus (A. fumigatus, RCMBA 06002), Geotrichum candidum (G. candidum, RCMB 05098), and Candida albicans (C. albicans, RCMB 05035) were investigated. The results indicated that the antibacterial and antifungal activities of the investigated derivatives are much higher than those of the parent O-carboxymethyl chitosan. They were more potent in case of Gram-positive bacteria than Gram-negative bacteria. The presence of electron withdrawing chlorine atom on the aryl moiety of the aldehyde portion improved greatly antimicrobial activity to be nearly equivalent to the used standard drugs.

Synthesis, characterization and applications of N-quaternized chitosan/poly(vinyl alcohol) hydrogels

Hydrogels composed of N-quaternized chitosan (NQC) and poly(vinyl alcohol) (PVA) in different weight ratios (1:3), (1:1) and (3:1) chemically crosslinked by glutaraldehyde in different weight ratios – 1.0 and 5.0% – have been prepared. The prepared hydrogels were characterized via several analysis tools such as: Fourier transform IR (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). Different applications have been done on NQC/PVA hydrogels including; metal ions uptake, swellability in different buffer solutions (pH: 4, 7 and 9), swellability and degradation studies in simulated body fluid (SBF) solutions and antimicrobial activity towards bacteria and fungi. The results indicated that crosslinked NQC/PVA hydrogels with glutaraldehyde (GA) are more thermallystable than non crosslinked hydrogels, NQC/PVA hydrogels swell highly in different buffer solutions as PVA content increases and the antimicrobial activity of NQC/PVA hydrogels is higher than NQC itself.

Synthesis and characterization of antibacterial semi-interpenetrating carboxymethyl chitosan/poly (acrylonitrile) hydrogels

Blend hydrogels composed of carboxymethyl chitosan (CMCh) and poly (acrylonitrile) (PAN) were synthesized via crosslinking method. Several analyses were made to investigate both physical and thermal properties of CMCh/PAN hydrogels like; FTIR, scanning electron microscope, XRD and thermogravimetric analysis (TGA). TGA results showed that CMCh/PAN hydrogels are thermally more stable than CMCh and their thermal stability increases as PAN content increases in the hydrogel. Moreover, the swelling behavior of CMCh/PAN hydrogels was studied in different buffer solutions. It was found that CMCh/PAN hydrogels swell much more than PAN especially at pH 9. The hydrogels sorption for different dyestuff and various metal ions like; Cu2+, Cd2+ and Co2+ were also studied. In this work, antibacterial characteristic of hydrogels was mainly investigated towards Escherichia coli (E. coli) as a serious disease-leading bacterium. All tested hydrogels have clearly presented good antibacterial activity as CMCh content increases in the hydrogels.

Sulfamethazine copper(II) complexes as antimicrobial thermal stabilizers and co-stabilizers for rigid PVC: spectroscopic, thermal, and DFT studies

[CuL2(OH2)]·1.5H2O (1), [CuL2(bpy)]·0.66H2O (2) and [CuLQ(OH2)]·H2O (3) (HL = sulfamethazine, bpy = 2,2′-bipyridine and HQ = 8-hydroxyquinoline) complexes were prepared, characterized (elemental analysis, infrared spectroscopy, thermogravimetric analysis, ultraviolet-visible spectroscopy, magnetic and conductivity measurement), and tested for their antibacterial activity. Coordination of HL to the Cu(II) ion did not markedly change its toxicity, but the presence of a secondary ligand gave rise to lower activity. Sulfamethazine and its complexes have been investigated as thermal stabilizers and co-stabilizers for rigid poly(vinyl chloride). A synergism has been achieved when the investigated compounds were mixed in an equivalent weight ratio with the reference stabilizers. The experimental studies have been complemented by density functional theory data in terms of optimization, natural bond orbital (NBO) analysis, and molecular electrostatic potential maps. The structural-thermal stabilization relationship showed that energy of the highest occupied molecular orbital, ΔE, and softness were the most useful descriptors for the correlation with the thermal stability.

Cytotoxicity and metal ions removal using antibacterial biodegradable hydrogels based on N-quaternized chitosan/poly(acrylic acid)

Physically crosslinked hydrogels resulted from interaction between N,N,N-trimethyl chitosan chloride (N-Quaternized Chitosan) (NQC) and poly(acrylic acid) (PAA) were synthesized in different weight ratios (3:1), (1:1) and (1:3) taking the following codes Q3P1, Q1P1 and Q1P3, respectively. Characterization of the mentioned hydrogels was done using several analysis tools including; FTIR, XRD, SEM, TGA, biodegradation in simulated body fluid (SBF) and cytotoxicity against HepG-2 liver cancer cells. FTIR results proved that the prepared hydrogels were formed via electrostatic and H-bonding interactions, while XRD patterns proved that the prepared hydrogels -irrespective to their ratios- were more crystalline than both matrices NQC and PAA. TGA results, on the other hand, revealed that Q1P3 hydrogel was the most thermally stable compared to the other two hydrogels (Q3P1 and Q1P1). Biodegradation tests in SBF proved that these hydrogels were more biodegradable than the native chitosan. Examination of the prepared hydrogels for their potency in heavy metal ions removal revealed that they adsorbed Fe (III) and Cd (II) ions more than chitosan, while they adsorbed Cr (III), Ni (II) and Cu (II) ions less than chitosan. Moreover, testing the prepared hydrogels as antibacterial agents towards several Gram positive and Gram negative bacteria revealed their higher antibacterial activity as compared with NQC when used alone. Evaluating the cytotoxic effect of these hydrogels on an in vitro human liver cancer cell model (HepG-2) showed their good cytotoxic activity towards HepG-2. Moreover, the inhibition rate increased with increasing the hydrogels concentration in the culture medium.

Synthesis of novel biodegradable antibacterial grafted xanthan gum

Xanthan gum (XG) is natural polysaccharides used in food industries as stabilizers and thickener agents. The problem is that some food products are found to be contaminated by pathogenic bacteria such as Escherichia coli (E. coli) and Staphyloccus aureus (S. aureus) that reduce their shelf life. This research aims to synthesize biodegradable antibacterial XG-grafted-poly(N-vinyl imidazole) PVI and the effect of reaction parameters were studied on grafting yield (G), grafting efficiency (GE), total conversion (TC) and homopolymer (H) %. XG-g-PVI was characterized via various analysis tools. Thermal analysis showed that grafted XG was more thermally stable than unmodified XG and their stability increased with increasing PVI%. XG-g-PVI was acting as antibacterial agent against (E. coli and S. aureus) bacteria that cause food borne diseases. Their activity increases with increasing grafting yield%. Surface morphology showed change from irregular lobules shape in XG to smooth surface in its graft with PVI.