Nahed A. Abd El-Ghany

Preparation and antimicrobial activity of some carboxymethyl chitosan acyl thiourea derivatives

Acetyl, chloroacetyl and benzoyl thiourea derivatives of carboxymethyl chitosan (ATUCMCS, CATUCMCS, and BZTUCMCS) with comparable grafting degree were synthesized and their structures were characterized by FTIR spectroscopy and elemental analyses. The antimicrobial behaviors of CMCS and its derivatives against three types of bacteria [Bacillis subtilis (B. subtilis), Staphylococous aureus (S. aureus) and Escherichia coli (E. coli)] and three crop-threatening pathogenic fungi [Aspergillus fumigate (A. fumigate), Geotrichum candidum (G. candidum) and Candida albicans (C. albicans)] were investigated. The results indicated that the antibacterial and the antifungal activities of the acyl thiourea derivatives are much higher than that of the parent CMCS. The acyl thiourea derivatives were more potent in case of Gram-positive bacteria than Gram-negative bacteria. This is illustrated for example by the values of minimum inhibitory concentration (MIC) of the ATUCMCS, CATUCMCS and BZTUCMCS against B. subtilis were 3.9, 15.6 and 62.5, respectively, while the MIC values of these derivatives against E. coli were 62.5, 125 and 500. Moreover, the antifungal activity of the CATUCMCS is higher than that of the acetyl and benzoyl thiourea derivatives. This may be due to the presence of chlorine atom.

Synthesis and antimicrobial activity of some novel terephthaloyl thiourea cross-linked carboxymethyl chitosan hydrogels

Four novel hydrogels composed of carboxymethyl chitosan (CM-chitosan) cross-linked with various contents of terephthaloyl thiourea moieties (TTUCM-chitosan-1, TTUCM-chitosan-2, TTUCM-chitosan-3, TTUCM-chitosan-4) have been successfully synthesized. The hydrogels were characterized by elemental analyses, FTIR, 13C NMR, SEM, XRD, solubility and swell ability in various solvents. The antimicrobial activities of these hydrogels against three crop-threatening pathogenic fungi (Aspergillus fumigatus, Geotrichumcandidum and Candida albicans) and against three bacterial species (Bacillis subtilis, Staphylococcus aureus and Escherichia coli) were investigated. The hydrogels showed higher antibacterial activity than the parent CM-chitosan as judged by their higher inhibition zone diameter and lower minimum inhibition concentration. They are more active against Gram-positive bacteria than against Gram-negative bacteria. The results also indicated that the hydrogels have effective antifungal activity as compared with CM-chitosan. The antimicrobial activity of the hydrogels increased with increasing their cross-linking density.

Synthesis, Characterization, and Antimicrobial Activity of Carboxymethyl Chitosan-Graft-Poly(N-acryloyl,N′-cyanoacetohydrazide) Copolymers

Carboxymethyl chitosan was grafted with N-acryloyl,N′-cyanoacetohydrazide in homogenous aqueous phase using potassium persulfate initiator. The maximum grafting yield achieved was 448% at 0.03 mol/L potassium persulfate, 0.75 mol/L N-acryloyl,N′-cyanoacetohydrazide, and 60°C within 2 h. The grafted copolymers showed better thermal stability than that of carboxymethyl chitosan. The samples with percent grafting values up to 98% were soluble in water, but a higher grafting extent resulted in insoluble copolymers. The grafted copolymers are nontoxic materials and showed an inhibition effect on both Escherichia coli and Staphylococcus aureus bacteria and Aspergillus flavus and Candida albicans fungi better than those of chitosan and carboxymethyl chitosan themselves.

Synthesis, characterization, and antimicrobial activity of chitosan hydrazide derivative

ABSTRACT A series of modified chitosan derivatives 1–4 has been synthesized. Modification process of chitosan was achieved through a sequence of four reactions starting by protection of its amino group with benzaldehyde (derivative 1), followed by reaction with epichlorohydrine (derivative 2), then reaction with benzhydrazide (derivative 3), and finally restoring the free amino groups on the chitosan by removing of benzaldehyde molecules (derivative 4). These four derivatives were characterized by elemental analyses, FTIR, and X-ray. The four chitosan derivatives showed better antibacterial and antifungal activities than that of chitosan. Derivative 4 exhibited the highest antimicrobial activity relative to the other derivatives. GRAPHICAL ABSTRACT

Novel polymaleimide containing dibenzoyl hydrazine pendant group as chelating agent for antimicrobial activity

ABSTRACT Novel polymaleimide containing dibenzoyl hydrazine pendant group, poly[N-benzoyl-4-(N-maleimido)-phenyl hydrazide], and its metal complexes have been synthesized. Their antimicrobial activity against Bacillus subtilis, Streptococcus pneumoniae, Pseudomonas aeruginosa, and Escherichia coli bacteria and that against Aspergillus fumigatus, Syncephalastrum racemosum, Geotrichum candidum, and Candida albicans fungi were investigated. The polymer–metal complexes showed better antimicrobial activity than that of the parent polymer. The inhibition of the growth of the microbes remarkably depends on the type of the metal in the complexes. The polymer–Co(II) and the polymer–Cd(II) complexes are more potent in inhibition of the tested microbes growth than the rest of the prepared complexes. GRAPHICAL ABSTRACT

Green options for imparting antibacterial functionality to cotton fabrics

This study demonstrated that antibacterial cellulosic textiles can be fabricated in eco-friendly manner by grafting of monochlorotriazinyl β-cyclodextin (MCT-βCD) onto knitted and woven cotton fabrics followed by post-loading of any of the green active ingredients namely Rosemary oil, Lavender oil, Clove oil, Cinnamon oil, Aloe vera gel, Vanillin, Ag-ions, Natural Yellow 7 and Natural Red 25 dyes into the hydrophobic cavities of grafted β-CD moieties. Some of the grafted, post-loaded fabric samples were characterized by FTIR, SEM, and EDS analysis. The enhancement in the imparted antibacterial functionality as well as durability to wash are governed by type of cellulosic substrate, kind, chemistry, antibacterial activity as well as extent of inclusion and subsequent release of the hosted bioactive agent. The obtained results revealed that the antibacterial efficacy follows the deceasing orders: i) knitted fabric > woven fabric and ii) Ag-ions > Lavender oil > Natural Yellow 7 > Aloe vera > Cinnamon oil > Natural Red 25 > Vanillin > Clove oil > Rosemary oil-loaded fabric sample, keeping other parameters constant.

Novel aminohydrazide cross-linked chitosan filled with multi-walled carbon nanotubes as antimicrobial agents

Four chemically modified chitosan derivatives 1-4 were designed and synthesized via a series of four reactions; first by reaction with benzaldehyde to protect its amino groups (Derivative 1), second by reaction with epichlorohydrine (Derivative 2), third by reaction with aminobenzhydrazide (Derivative 3), and forth by removing of benzaldehyde to restore the free amino groups on the chitosan (Derivative 4). Two multi-walled carbon nanotube (MWCNT) biocomposites based on Derivative 4 were also prepared. The structure of the prepared derivatives and MWCNT composites was elucidated using elemental analyses, FTIR, XRD, SEM and TEM. The modified chitosan derivatives and MWCNT composites showed better antimicrobial activities than that of chitosan against Enterococcus faecalis, Staphylococcus epidermidis, Escherichia coli, Aspergillus niger, Cryptococcus neoformans and Candida tropicalis as judged by their higher inhibition zone diameters using the agar well diffusion technique. These derivatives and MWCNT composites are more potent against Gram-positive bacteria than against Gram-negative bacteria. The MWCNT composites displayed comparable or even better antimicrobial activities than the reference bactericides or fungicides. Thus, structural modification of chitosan through combination with functionalized moieties and MWCNTs in one system was taken as a way to achieve promising templates for antimicrobial agents and to be appropriate candidates for medical applications.

Antimicrobial activity of new carboxymethyl chitosan–carbon nanotube biocomposites and their swell ability in different pH media

ABSTRACT New carboxymethyl chitosan–carbon nanotube (CMCS-CNT) biocomposites were prepared and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and normal photography. The recorded images of the CMCS-CNT biocomposites showed homogeneous distribution of carbon nanotubes into the carboxymethyl chitosan (CMCS) matrix. Their antimicrobial activity and swell ability in different pH media have been investigated. They showed a higher antimicrobial activity against tested gram-positive and gram-negative bacteria. The inhibition zone diameters are closer to that recorded for the commonly used antibiotics. They showed an increase in the swell ability in different pH media relative to the parent CMCS. It would be expected that these nanobiocomposites are promising candidates for medical applications. GRAPHICAL ABSTRACT

Pyromellitimide benzoyl thiourea cross-linked carboxymethyl chitosan hydrogels as antimicrobial agents

ABSTRACT A series of novel hydrogels based on carboxymethyl chitosan (CMCS) has been synthesized by a cross-linking reaction between CMCS and various amounts of N,N′-bis [4-(isothiocyanate carbonyl)phenyl] pyromellitimide as a cross-linker to produce pyromellitimide benzoyl thiourea–CMCS hydrogels designated as PIBTU–CMCS (1–4). Hydrogel structures were identified by elemental analyses and FTIR and 1H-NMR spectroscopy. The prepared hydrogels were characterized for their properties to understand the influence exerted by controlled structural variations in these hydrogels. All the hydrogels showed a greater antibacterial activity on Gram-positive than Gram-negative bacteria. They also exhibited higher antifungal activities. Their antimicrobial activity improved by increasing their cross-linking degree. GRAPHICAL ABSTRACT