Synthesis of poly-γ-glutamic acid-crosslinked-pectin-based nanogel and its antioxidant and antibacterial properties

The poly-γ-glutamic acid (γ-PGA, synthesized by glutamic acid isolated from snail hemolymph) was crosslinked with pectin to synthesize the nanogel composite (γ-PGA-cl-Pect), which was used to evaluate its swelling nature and the efficacy of its antibacterial and antioxidant properties. The average size of the particles' diameter was 173.67 ± 0.73 nm, which indicated the synthesis was effective. The techniques used to analyze the sample both quantitatively and qualitatively were Fourier Transform Infrared Spectroscopy (FTIR), Field Emission Scanning Electron Microscopy (FESEM), Nuclear Magnetic Resonance Spectroscopy (NMR), Dynamic Light Scattering (DLS), Electron Spin Resonance Spectroscopy (ESR), and Differential Scanning Calorimetry (DSC). Three different pH levels (4.2, 6.5, and 7.4) and two different temperatures (25 °C and 37 °C) were used to evaluate the swelling properties, which showed high absorbency that was advantageous in drug delivery applications. The antibacterial assay was performed on four different bacterial strains. The synthesized nanogel showed a strong inhibitory zone, especially against Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli. The effect of azithromycin (the positive control) was found to be less effective than the nanogel. This approach enhanced antibacterial efficacy through the cell wall-targeting antibacterial mechanism. The synthesized nanogel decreased free radical generation by up to 90.23% at a concentration of 120 µg/ml in the experiment, exhibiting its antioxidant properties. The overall phenolic content of the nanogel composite was determined using the Folin-Ciocalteu reagent, with gallic acid as the standard, yielding a value of 98.689 ± 1.099 mg GAE/g.