Role of Ionic Surfactants in Constitution of Binary Micellar System for Solubilizing Telmisartan

Abstract

In this study, two binary micellar systems of Pluronic P-123 (P-123) were employed for solubilizing antihypertensive drug Telmisartan (TMS). They are, P123 with cationic surfactant, cetyl pyridinium bromide (CPB); and P123 with anionic surfactant, ammonium dodecyl sulfate (ADS).  The solubilization studies in two polymeric binary micellar mediums were investigated through conductivity, FTIR, and UV-visible spectroscopy.  The change in the particle size and charge were observed through SEM, dynamic light scattering, and zeta potential measurements.  From the conductivity studies various thermodynamic parameters such as Gibb’s free energy of micellization (ΔG_m), Enthalpy (ΔH_m), and entropy of micellization (ΔS_m) were calculated.  There was a negative value of ΔG_m for both the mixed micellar systems, -20.4 kJmol^-1 for CPB + P-123 + TMS and -25.9 kJmol^-1 for ADS + P-123 + TMS.  This is suggestive of the spontaneity of micellization of both the systems with drug TMS. UV studies demonstrated higher solubility with both the mixed micellar systems compared to solubilization in a single micelle of P-123.  The binding constant values were determined from UV absorbance values using the Benesi - Hildebrand plot. The values were 79. 36 M^-1 for TMS +P-123, 465.11 M-1 for TMS + P-123 + CPB and 1133.8 M^-1 for TMS + P-123 + ADS.  There was swelling of the micellar size from 16.23 nm to 52.02 nm for CPB group and from 3.16 nm to 32.04 nm for ADS group due to the encapsulation of TMS in the mixed micellar cavities. Size of both the ternary systems containing drug are suitable for cellular uptake.  This study offers two alternative combinations of mixed polymeric micellar systems to enhance TMS solubilization to improve bioavailability.