Physicochemical and solubilization properties of N,N-dimethyl-N-(3-dodecylcarbonyloxyproply)amineoxide: A biodegradable nonionic surfactant

The physicochemical characteristics of N,N-dimethyl-N-(3-dodecylcarbonyloxy propyl)amineoxide (DDCPNO), a biodegradable analogue of a N,N-dimethylalkyl amine-N-oxide, are compared with those of N,N-dimethyldodecylamine-N-oxide (DDNO) to establish the effect on the properties of DDNO of inserting a pro poxy linker between the hydrophobic tail and hydrophilic head region. Surfa ce tension measurements gave a critical micelle concentration of 0.33 mM fo r DDCPNO compared with a value of 1.57 mM for DDNO, suggesting that the for mer was the more hydrophobic surfactant. This result was confirmed by laser light scattering studies in which total intensity light scattering indicat ed the presence of DDCPNO micelles of aggregation number 85.0. Photon corre lation spectroscopy studies yielded a limiting hydrodynamic diameter of 4.0 nm in comparison with values of 57.5 and 3.3 nm obtained for the aggregati on number and the limiting hydrodynamic size, respectively, of DDNO micelle s. Studies demonstrated that neither a dilute aqueous solution of DDCPNO or DDNO exhibited a cloud point within the temperature range 293-373 K. Solub ilization studies showed that the capacity of DDCPNO micelles for a range o f drugs of varying size and polarity was less than that observed with DDNO micelles at an equivalent surfactant concentration. As a further measure of solubilization, the ability of DDCPNO to form oil-in-water microemulsions with a range of ethyl ester oils was investigated and found to be slightly higher than that achieved with DDNO. Together these studies suggest that th e presence of the semipolar linker significantly alters the properties of t his low molecular weight surfactant. (C) 2000 Wiley-Liss, Inc.