Barea, Matthew Ernest John (2012)
Ph.D. thesis, University of Birmingham.
Recent studies have shown the numerous advantages associated with specific drug delivery to the colon, highlighting its favourable conditions and long transit time as the main advantages. A number of in vitro studies also show that the delivery of liposomes to the colon could provide further advantages due to bonding to the colonic mucosa in both healthy and inflamed regions. Despite these apparent advantages no oral liposomal formulation has been developed for targeted delivery to the colon as yet.
Initially, experiments were conducted in which liposomes were directly coated with the pH responsive polymer Eudragit S100. Although the coating was shown to slow drug release in simple pH buffers, it was realised it could not protect the lipid membrane from the model bile salt sodium taurocholate. Development of the formulation moved onto the production of Eudragit S100 microspheres to provide a solid barrier to protect the liposomes. Due to the solvents required in the microsphere production it was essential to protect the liposomes, which was done by coating them with the enzyme controlled polymer chitosan. The final stage involved encapsulating chitosan-coated liposomes within the Eudragit microspheres to produce a novel, colon targeting liposome-in-microsphere (LIM) formulation.
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