Designing nonionic surfactant vesicles for the delivery of antigens for systemic and alternative delivery routes

Bilayer vesicles can be prepared from a range of molecules including nonionic surfactants. Vesicles built from nonionic surfactants are known as nonionic surfactant vesicles or niosomes. Whilst structurally similar to liposomes, the use of nonionic surfactants in a formulation may offer advantages in terms of chemical stability and reduced cost in some cases. In general, the ability of surfactant blends to form vesicles is dependent on their combined critical packing parameter, with cholesterol often being used to support the formation of vesicle constructs. To enhance the potency and delivery of antigens, niosomes can be designed to protect antigens against degradation in harsh in vivo environments, including the oral route, and enhance delivery of antigens to appropriate target sites. Key considerations in the design of niosomal adjuvants include the choice of surfactants, the surface properties of the vesicles, the method of preparation, the cholesterol content and the inclusion of immunostimulatory agents. Manipulation of these attributes allows vesicle constructs to be designed and built that can be used to deliver antigens via a range of delivery routes.