A comparative study on antibacterial activities of chitosan based products and their combinations with gentamicin against S. epidermidis and E. coli

Spectroscopic Analysis and Microbicidal Effect of Ag/TiO2-SiO2 Bionanocatalysts

Silver, especially nanostructured silver, has been found to exhibit antimicrobial properties by disrupting the function of bacterial cell walls. Nonetheless, strains of bacteria have been reported to resist silver nanoparticles. The highly efficient mutational mechanisms of bacteria, capable of overcoming modern antimicrobial compounds, make it critical to develop new materials that target genetic material, regardless of nucleotide sequence or protein structure, without being toxic to the patient. This work evaluates the microbicidal properties of a catalytic, nanostructured, organically functionalized, titanosilicate matrix (bionanocatalysts) impregnated with silver. The bionanocatalysts were synthesized by the sol-gel method using silver acetate as the silver precursor. The effect of the bionanocatalysts against clinically important strains of bacteria and yeasts was evaluated. In addition, the physicochemical composition and in vitro reactivity on DNA were studied. The antibiogram analysis revealed that the compound could inhibit the growth (inhibition halos of up to 15 ± 0.9 mm) of all the strains studied (bacteria and yeasts) at low concentrations of silver, thus reducing the toxicity associated with platinum. In this work, by adding silver in the catalytic TiO2-SiO2 matrix, the intrinsic microbicidal properties of the metal were enhanced: the results provided a valuable compound exhibiting reduced toxicity and antimicrobial effects that could potentially be used as a potent disinfectant against drug-resistant strains, as found in hospitals, for instance.

Microbicidal gentamicin-alginate hydrogels

Sodium alginate (Alg) reacted with antibiotic gentamicin sulfate (GS) in an aqueous-phase condition mediated by carbodiimide chemistry, in the molar ratios Alg: GS of (1:0.5), (1:1) and (1:2). The Alg-GS conjugated derivatives were characterized by elemental analysis for nitrogen content, Fourier transform infrared spectroscopy in the attenuated total reflection mode (FTIR-ATR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), thermogravimetric analyses (TGA) and water sorption measurements. XPS and FTIR-ATR analyses clearly indicated that GS molecules covalently attached to the backbone of the alginate chains by amide bond formation. The highest amount of GS bound to Alg (43.5 ± 0.4 wt%) and the highest swelling ratio (4962 ± 661%) were observed for the Alg-GS (1:2) sample. Bioluminescence assays with Pseudomonas aeruginosa PAO1/lecA:lux and colony forming counting of Staphylococcus aureus and Escherichia coli upon contact with all Alg-GS conjugates revealed microbicidal activity; however, Alg-GS (1:2) was the most efficient, due to the highest GS content.

Surface immobilization of kanamycin-chitosan nanoparticles on polyurethane ureteral stents to prevent bacterial adhesion

Bacterial adhesion is a major problem that can lead to the infection of implanted urological stents. In this study, kanamycin-chitosan nanoparticles (KMCSNPs) were immobilized on the surface of a polyurethane ureteral stent (PUS) to prevent urinary bacterial infection. KMCSNPs were synthesized using the ionic gelation method. The synthesized KMCSNPs appeared spherical with a ζ-average particle size of 225 nm. KMCSNPs were immobilized on the PUS surface by covalent immobilization techniques. The surface-modified PUS was characterized using attenuated total reflectance Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and energy dispersive X-ray spectroscopy. The surface-modified PUS showed significantly increased antibacterial activity against Escherichia coli MTCC 729 and Proteus mirabilis MTCC 425 relative to the surface of an unmodified PUS. These findings suggest that the KMCSNP-immobilized PUS has the potential to prevent bacterial infection in the human urinary tract.

The effect of substituent, degree of acetylation and positioning of the cationic charge on the antibacterial activity of quaternary chitosan derivatives

A series of water-soluble cationic chitosan derivatives were prepared by chemoselective functionalization at the amino group of five different parent chitosans having varying degrees of acetylation and molecular weight. The quaternary moieties were introduced at different alkyl spacer lengths from the polymer backbone (C-0, C-2 and C-6) with the aid of 3,6-di-O-tert-butyldimethylsilyl protection of the chitosan backbone, thus allowing full (100%) substitution of the free amino groups. All of the derivatives were characterized using ¹H-NMR, ¹H-¹H COSY and FT-IR spectroscopy, while molecular weight was determined by GPC. Antibacterial activity was investigated against Gram positive S. aureus and Gram negative E. coli. The relationship between structure and activity/toxicity was defined, considering the effect of the cationic group’s structure and its distance from the polymer backbone, as well as the degree of acetylation within a molecular weight range of 7–23 kDa for the final compounds. The N,N,N-trimethyl chitosan with 100% quaternization showed the highest antibacterial activity with moderate cytotoxicity, while increasing the spacer length reduced the activity. Trimethylammoniumyl quaternary ammonium moieties contributed more to activity than 1-pyridiniumyl moieties. In general, no trend in the antibacterial activity of the compounds with increasing molecular weight or degree of acetylation up to 34% was observed.