Optimization of pH conditions and characterization of polyelectrolyte complexes between gellan gum and cationic guar gum

The present study was aimed to investigate optimum pH conditions for polyelectrolyte complexation between gellan gum (GG) and cationic guar gum (CGG). The pKa of both the polymers was determined using potentiometric titrations. The complex formation was investigated at three pH values (based upon the pKa interval of two polymers) and at different mixing ratios (ranging from 10:90 to 90:10). Zeta potential and turbidity studies elucidated the optimum pH and mixing ratio at which maximum interaction takes place between the polymers. The studies revealed neutral zeta potential, highest turbidity, and low transmittance at mixing ratio 30:70 and 40:60 (GG:CGG; pH5.5), indicating maximum complex formation at these ratios. The percentage yield and viscosity studies of supernatant also revealed maximum interaction at these mixing ratios of polymers. The polyelectrolyte complexes (PECs) were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and for their swelling behavior in pH progression medium. The FTIR spectra confirmed formation of bonds between COOand -N+(CH3)(3) of GG and CGG, respectively. DSC studies revealed the stability, affinity, and spontaneous nature of complexation between these polymers. The morphological changes detected through SEM studies in GG-CGG PECs exposed to different pH buffers also found to exhibit pH-dependent swelling. The FTIR spectra, DSC, SEM, and swelling studies of PECs treated with buffer pH1.2 followed by buffer pH7.4 suggested that PECs comprising 40:60 ratio of GG:CGG, prepared at pH5.5, could be used to formulate a pH-sensitive drug delivery system.