Gum Arabic polymer-stabilized and Gamma rays-assisted synthesis of bimetallic silver-gold nanoparticles: Powerful antimicrobial and antibiofilm activities against pathogenic microbes isolated from diabetic foot patients.

In this research, irradiation by gamma rays was employed as an eco-friendly route for the construction of bimetallic silver-gold nanoparticles (Ag-Au NPs), while Gum Arabic polymer was used as a capping agent. Ag-Au NPs were characterized through UV-Vis., XRD, EDX, HR-TEM, FTIR, SEM/mapping and EDX analysis. Antibiofilm and antimicrobial activities were examined against some bacteria and Candida sp. isolates from diabetic foot patients. Our results revealed that the synthesis of Ag-Au NPs depended on the concentrations of tetra-chloroauric acid and silver nitrate. HR-TEM analysis confirmed the spherical nature and an average diameter of 18.58 nm. FTIR results assured many functional groups in Gum Arabic which assisted in increasing the susceptibility of incorporation with Ag-Au NPs. Our results showed that, Ag-Au NPs exhibited the highest antimicrobial performance against B. subtilis (14.30 mm ZOI) followed by E. coli (12.50 mm ZOI) and C. tropicalis (11.90 mm ZOI). In addition, Ag-Au NPs were able to inhibit the biofilm formation by 99.64%, 94.15%, and 90.79% against B. subtilis, E. coli, and C. tropicalis, respectively. Consequently, based on the promising properties, they showed superior antimicrobial potential at low concentration and continued-phase durability, they can be extensively-used in many pharmaceutical and biomedical applications.

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

Gum Arabic (GA) microgels were successfully prepared via reverse micellization method with high yield (78.5±5.0%) in 5-100µm size range using divinyl sulfone (DVS) as a crosslinker. The GA microgels were degraded hydrolytically 22.8±3.5% at pH 1 in 20days, whereas no degradation was observed at pH 7.4 and pH 9 at 37°C. By using diethylenetriamine (DETA), and taurine (TA) as chemical modifying agents, GA microgels were chemically modified as GA-DETA and GA-TA, and the zeta potential values of 5.2±4.1 and -24.8±1.3mV were measured, respectively in comparison to -27.3±4.2mV for GA. Moreover, blood compatibility of GA, GA-TA, and GA-DETA microgels was tested via in vitro protein adsorption, % hemolysis ratio, and blood clotting index. All the microgels were hemocompatible with% hemolysis ratio between 0.23 to 2.05, and the GA microgels were found to be highly compatible with a blood clotting index of 81±40. The biocompatibility of GA, GA-DETA and GA-Taurine microgels against L929 fibroblast cells also revealed 84.4, 89.1, and 67.0% cell viability, respectively, at 25.0µg/mL concentration, suggesting great potential in vivo biomedical applications up to this concentration. In addition, 5 and 10mg/mL minimum inhibition concentrations of protonated GA-DETA microgels (GA-DETA-HCl) were determined against E. coli and S. aureus, respectively.

Functionalization of natural gum: an effective method to prepare iodine complex.

To overcome the drawbacks associated with iodine e.g. insolubility in water, etc., it has been complexed with polymers that have the ability to bind it. In this study, gum arabic (GA), a natural gum was functionalized to introduce new reactive groups that can easily interact with small molecules followed by iodination in ethanol solution to prepare an iodine complex. The samples were characterized by FTIR, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized iodine complex was found reddish-brown in colour and stable at room temperature. The interaction of free available iodine with functionalized GA was also studied and established by UV-vis spectrophotometer. The amount of iodine released in water was measured by iodometric titration method and its value compared with the available iodine complex, polyvinylpyrrolidone-iodine complex. The antimicrobial activity of iodine complex was tested against Escherichia coli (Gram negative bacteria) and found to be effective against it.

Composition and structure of whey protein/gum arabic coacervates.

Complex coacervation in whey protein/gum arabic (WP/GA) mixtures was studied as a function of three main key parameters: pH, initial protein to polysaccharide mixing ratio (Pr:Ps)(ini), and ionic strength. Previous studies had already revealed under which conditions a coacervate phase was obtained. This study is aimed at understanding how these parameters influence the phase separation kinetics, the coacervate composition, and the internal coacervate structure. At a defined (Pr:Ps)(ini), an optimum pH of complex coacervation was found (pH(opt)), at which the strength of electrostatic interaction was maximum. For (Pr:Ps)(ini) = 2:1, the phase separation occurred the fastest and the final coacervate volume was the largest at pH(opt) = 4.0. The composition of the coacervate phase was determined after 48 h of phase separation and revealed that, at pH(opt), the coacervate phase was the most concentrated. Varying the (Pr:Ps)(ini) shifted the pH(opt) to higher values when (Pr:Ps)(ini) was increased and to lower values when (Pr:Ps)(ini) was decreased. This phenomenon was due to the level of charge compensation of the WP/GA complexes. Finally, the structure of the coacervate phase was studied with small-angle X-ray scattering (SAXS). SAXS data confirmed that at pH(opt) the coacervate phase was dense and structured. Model calculations revealed that the structure factor of WP induced a peak at Q = 0.7 nm(-1), illustrating that the coacervate phase was more structured, inducing the stronger correlation length of WP molecules. When the pH was changed to more acidic values, the correlation peak faded away, due to a more open structure of the coacervate. A shoulder in the scattering pattern of the coacervates was visible at small Q. This peak was attributed to the presence of residual charges on the GA. The peak intensity was reduced when the strength of interaction was increased, highlighting a greater charge compensation of the polyelectrolyte. Finally, increasing the ionic strength led to a less concentrated, a more heterogeneous, and a less structured coacervate phase, induced by the screening of the electrostatic interactions.

Preparation and in vitro evaluation of primaquine-conjugated gum arabic microspheres.

Gum arabic, a branched polysaccharide, was oxidized using periodate to generate reactive aldehyde groups on the biopolymer. Primaquine, an 8-aminoquinoline, was covalently coupled onto oxidized gum arabic via an imine bond and simultaneously fabricated into microspheres of less than 2 microm in size by heat denaturation in a reverse emulsion of 1:1 light paraffin oil and toluene stabilized by sorbitan sesquioleate as the surfactant. The covalent binding of primaquine to the polysaccharide using the clinically used water-soluble form of the drug primaquine phosphate was achieved in the presence of borate buffer of pH 11. Up to 35% of the drug could be bound to the polymer backbone depending on the concentration of the drug employed initially and the degree of oxidation of the polysaccharide. Interestingly, both the aliphatic and the hindered aromatic amino groups of primaquine were found to react with the aldehyde functions through Schiff base formation leading to cross-linking of the polysaccharide with the drug itself. In vitro release of the drug from microspheres into phosphate buffered saline (PBS, pH 7.4, 0.1 M) at 37 degrees C showed that the release of primaquine from the matrix was slow, although gradually increased with time. The maximum released was below 50% of the drug payload even after 10 days. Release into simulated gastric and intestinal fluids was faster compared to the release in PBS due to rapid hydrolysis of the Schiff's linkage in the gastric fluid. A possible reason for the poor hydrolytic susceptibility of the Schiff's linkage is suggested based on the unequal reactivity of the amino groups on primaquine and its relevance in possible therapeutic application of this polymer-drug conjugate discussed.