This study investigated the interaction between polydeoxyribonucleotide (PDRN) and several ionic and nonionic isotonic agents, thickeners and a preservative that were employed as excipients in ophthalmic preparations. Interaction of each individual excipient and PDRN aqueous solution was evaluated by analyzing their rheological properties. Rheological properties of PDRN solutions were evaluated by dynamic oscillatory shear tests and values of elastic modulus (G'), viscous modulus (G″) and loss tangent (tan δ) were used to assess the relative changes in viscoelastic properties. At given concentrations, sodium chloride was found to show alteration in viscoelastic properties of PDRN solution while nonionic isotonic agents like d-glucose and d-sorbitol did not alter them. Similarly, nonionic water soluble polymers like polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) also did not interact with PDRN to alter the viscoelastic properties. However, there were changes observed when carbopol 940 was used as a thickener. Therefore, PDRN was found to interact with ionic excipients and the interactions were negligible when nonionic materials were examined, which suggests that nonionic excipients are suitable to be formulated with PDRN.
Keywords: Polydeoxyribonucleotide; ophthalmic formulation; pharmaceutical excipients; rheology; viscoelasticity.