The present invention relates to nano-resin particles that are suitable for pharmaceutical use and their use in the pharmaceutical field. The present invention provides nano-sized resin particles having a particle size distribution characterized in that D90 value is between 200 nanometers to 900 nanometer and D10 value is not less than 50 nanometers, wherein the nano-resin particles are in pure form and safe for pharmaceutical use. The present invention further relates to pharmaceutical compositions comprising these purified nano-resin particles and their use in the treatment of diseases. The present invention further provides a process for preparing purified, nano-sized resin particles that are suitable for pharmaceutical use, the process comprising steps of : (i) washing an ion exchange resin and suspending in an aqueous liquid, (ii) subjecting the suspension of (i) to wet milling for a period such that the particles have a particle size distribution characterized in that the D90 value is between 200 nanometers to 900 nanometers and D10 value is not less than 50 nanometers, (iii) subjecting the suspension of (ii) to purification to remove impurities, (iv) drying the pun fled suspension to obtain nano-resin particles in the form of dry powder.