Development of positively charged colloidal drug carriers: Chitosan-coated polyester nanocapsules and submicron-emulsions

Three different colloidal carriers, namely, nanoparticles and nanocapsules made of poly-epsilon-caprolactone and submicron emulsions, were designed, and their capacity for increasing the comeal penetration of drugs was investigated. The three systems differed in their inner structure and composition, but they had a similar size (200-250 nm) and a negative superficial charge (-16 to -42 mV). Indomethacin, which was used as a model drug, was dispersed at a molecular level within the colloidal systems, no chemical interaction between the polymer and the drug being detected. Release of the encapsulated indomethacin occurred very rapidly upon high dilution in a buffered medium and was independent of the composition of the system. The in vitro comeal penetration of the encapsulated indomethacin was more than 3-fold that of the commercial eye drops. This increased penetration was similar for the three formulations investigated, which therefore excludes the influence of the inner structure or chemical composition of the colloidal systems on the comeal penetration of indomethacin. Thus, it could be stated that the main factor responsible for the favorable comeal transport of indomethacin is the colloidal nature of these carriers rather than their inner structure or composition. Show more

Submicron injectable emulsions have been gaining more and more attention in the last few years, mainly as a vehicle for the intravenous administration of lipophilic drugs rather than as an improved delivery system for drug targeting. Submicron emulsions are available, clinically well accepted, and successfully marketed. Novel original emulsion formulations are being extensively investigated and already exhibit improved pharmacological activity; this fact underlines the promising therapeutic properties of these colloidal drug carriers as vehicles for potent lipophilic drugs. It is therefore essential to carry out a comprehensive physicochemical characterization of these submicron emulsions. It is the objective of the present review to emphasize the need for physicochemical studies in the design of new submicron emulsion drug delivery systems and to describe the different approaches available for carrying out such a complete examination of the emulsion colloidal drug carrier system. Show more