title: An investigation into the role of mucus thickness on mucoadhesion in the gastrointestinal tract of pig.
abstract: Mucoadhesion in the gastrointestinal tract is a complex phenomenon and both formulation and physiological features need to be well understood and considered. Mucus thickness has been inferred to play a role in this process; however no definitive influence has been established. This study aimed to investigate the influence of mucus thickness on the mucoadhesion process, using a large animal (pig) as a model to closely resemble the human physiological features. The mucus thickness of different regions of the gastrointestinal tract of pig was fully measured by means of a histochemical method (hematoxilin/eosin) employing cryostat sections. Mucoadhesion was evaluated ex vivo on porcine mucosa by tensiometry using a polyacrylic acid polymer (Carbopol 974P NF) as a mucoadhesive model material, both in a dry and swollen state. Mucus was thickest in the stomach (body 67.9+/-54.7 microm) and mucus thickness increased from proximal to distal segments in both the small intestine (duodenum 25.9+/-11.8 microm, ileum 31.0+/-15.7 microm) and large intestine (caecum 19.4+/-8.7 microm, ascending colon 31.9+/-17.2 microm, descending colon 35.1+/-16.0 microm and rectum 40.8+/-12.5 microm). Swollen polymer exhibited lower mucoadhesion than the dry form in all sections analysed. Mucus thickness plays a role on the mucoadhesion, as thicker mucus provides deeper polymer chain diffusion and entanglements; however, other factors are also involved in this complex process.
authors.affiliation: Laboratory of Pharmaceutical Technology, Faculty of Pharmacy, University of Coimbra, Coimbra, Portugal.
authors.forename: Felipe J O
authors.initials: FJ
authors.lastname: Varum
authors.forename: Francisco
authors.initials: F
authors.lastname: Veiga
authors.forename: João S
authors.initials: JS
authors.lastname: Sousa
authors.forename: Abdul W
authors.initials: AW
authors.lastname: Basit
mesh_terms: D000179:Acrylates / Q000737:chemistry; D000180:Acrylic Resins / Q000737:chemistry*; D000268:Adhesiveness; D000277:Adjuvants, Pharmaceutic / Q000737:chemistry; D000818:Animals; D055598:Chemical Phenomena; D002626:Chemistry, Pharmaceutical; D016616:Cryoultramicrotomy; D005753:Gastric Mucosa / Q000502:physiology / Q000648:ultrastructure; D041981:Gastrointestinal Tract / Q000502:physiology* / Q000648:ultrastructure; D007413:Intestinal Mucosa / Q000502:physiology / Q000648:ultrastructure; D009093:Mucus / Q000737:chemistry*; D009928:Organ Specificity; D034421:Sus scrofa; D014783:Viscosity; D014867:Water / Q000032:analysis
chemical_list: D000179:Acrylates; D000180:Acrylic Resins; D000277:Adjuvants, Pharmaceutic; C117167:carbopol 974P NF; D014867:Water