(162k) Double-Carrier Systems as Novel Drug Delivery Vehicles

Cationic hydrogel particles were prepared as carriers in nano and micro size. It was shown that these carriers can be transported by another micro-scale delivery vehicle such as an oil-in-water (O/W) or a water-in-oil-in-water (W1/O/W2) emulsion system. The perception is that the use of a carrier inside another carrier provides the advantage of both systems. For example, while one carrier is keeping the load in perfect conditions i.e. stealth, the other carrier can afford the storage and handling for the initial shipment. The microcapillary technique developed in our laboratory was employed to closely monitor the individual multiple emulsion systems. Here, the emulsion system consists of either nanohydrogels dispersed in the internal aqueous phase (H/W1/O/W2), or microhydrogels themselves suspended in the oil phase (H/O/W). Since fluorescent dye was used as a model active substance, fluorescence microscopy images revealed that hydrogels (first carrier) prevent the fluorescent dye from spontaneously migrating into the external aqueous phase of the second carrier. Then, the fluorescent dye loaded into the hydrogels was shown to be released upon changing the pH of the medium. In this work, a novel route to improve the encapsulation and controlled release in double emulsions was proposed, which consists of forming a complex between the encapsulated species and the hydrogel particles confined either in the internal water droplets (nanohydrogels) or in the oil globule (microhydrogels). It was demonstrated that complex formation inhibits the diffusion of the encapsulated species across the oil phase and that the active-substance release from the delivery vehicles can be promoted by external stimuli, whose role is to disrupt such complex. This concept is applicable to any other chemical complexation and opens new perspectives in the field of microencapsulation.