CHARACTERIZATION OF BIOADHESIVES FOR PERIODONTAL AND ORAL MUCOSAL DRUG-DELIVERY

Whilst there is keen interest in developing improved drug delivery dev ices to the periodontal pocket and oral mucosa, there are few reports which have examined the physical properties of gels and semi-solid for mulations which favour retention and bioadhesion in situ, Hydration an d rheological properties appear to be of prime importance in this cont ext and this study aimed to correlate the measurement of these propert ies with observed bioadhesion, both in vitro and in vivo. Three candid ate bioadhesives were selected from previous experiments which had use d in vitro organ culture models. These were chitosan, xanthan gum and poly (ethylene oxide) aqueous formulations. Hydration rates with vario us media were determined in specially constructed cells, Rheological p roperties were measured using a controlled stress rheometer under care fully regulated conditions, These findings were also correlated with i n vivo assessments in the periodontal pocket and oral mucosa. The resu lts demonstrated that three formulations with differing bioadhesive pr operties also possessed widely different physical characteristics. Hyd ration experiments indicated a direct relationship between the rate of hydration and bioadhesion or retention, Rheological studies suggested that possession of a gel structure could be an important determinant of retention where shear displacing forces are present in Five, e.g. t he oral mucosa. Furthermore, these studies indicated that formulations which could demonstrate resistance to changes in rheological properti es on hydration would also favour retention in situ. Physical characte risation therefore appears to have an important place in screening pol ymeric formulations prior to clinical testing in the periodontal pocke t and oral mucosa.