In this study, polyuronide was isolated from Lallementia royleana seeds, and its carboxymethyl modification was carried out by Williamsons’ synthesis. The degree of carboxymethylation substitution was found to be 1.65. The outcomes of the characterization studies performed on carboxymethylated derivative pointed to the increased flow properties and elasticity, decreased swelling property, viscosity and anionic nature. The nanoparticulate suspension of modified polyuronide was prepared by its interaction with chitosan using ofloxacin as a model drug. The concentrations of modified polyuronide and chitosan were found to affect the particle size. The polyelectrolyte nanosuspension formulated using carboxymethylated polyuronide (0.02 %,w/v) and chitosan (0.01%,w/v) showed particle size, polydispersity index, zeta potential and entrapment efficiency of 402.3 nm, 0.315, 22.3 mV and 96.50%, respectively was selected for in vitro release study. The selected batch of nanosuspension provided a sustained release of 87.10% of ofloxacin over a time period of 12 h following first-order kinetics with mechanism of release being diffusion through the matrix.