Microparticles as delivery systems for local delivery to the oral cavity.

A number of pathologies can be treated locally in the oral cavity, such as periodontal diseases, bacterial and fungal infections, dental stomatitis and toothaches. Biodegradable polymers examined for potential oral drug delivery include poly (lactide-co-glycolide) (PLG), polyanhydrides, poly(methyl methacrylate) and poly alkylcyanoacrylates (11). These biodegradable polymers can be proposed for the production of microparticles for oral mucosa delivery. Microparticles, after direct application to the periodontal pocket, can gradually release controlled amounts of drug for long periods (up to a month). Esposito and colleagues described the production by different methods of biodegradable microparticles for the administration of tetracycline in the oral cavity. In particular, different polymers, such as poly(L-lactide) (L-PLA), poly(DL-lactide) (DL-PLA) and poly(DL-lactide-co-glycolide) 50:50 (DL-PLG) have been employed. The influence of polymer and preparation procedure were studied on microparticle characteristics (i.e. morphology and encapsulation yield). Moreover the release modalities of tetracycline from the produced microparticles were investigated. Bodmeier and Chen proposed PLG microparticles as carrier for recombinant human bone morphogenic protein-2-driven recombinant regeneration. Particularly, these microparticles were used to support the recombinant protein and then positioned in transgingival tooth of dogs. Biodegradable and bioadhesive starch microparticles (Pharmacia, Hillerod, Dk) were in addition used to deliver antigen and immunoglobulin A-enhancing cytokines to the oral mucosa. One of the main strategy to deliver antigen was the topical administration of starch microparticles at the sublingual epithelium of the oral cavity. Again antigen delivery was proposed using microparticles constituted of polylactides and their copolymers with glycolic acid by both the oral and injectable routes. PLG microparticles can release antigen by hydrolytic erosion of the polymer protecting at the same time the antigen from degradation. The biodegradation rate of these polymers allow the production of sustained release formulations able to maximize both the amplitude and the duration of the immune response to the released antigen. Oral delivery is and will likely to remain the most convenient drug administration way especially for buccal antibiotic delivery and oral vaccination. In this view,, the main conclusions of this brief monograph is that the selection of both appropriate preparation method and polymer type allowed the production of biodegradable microparticles that can provide sustained delivery of the drug to the oral mucosa.