The Effect of Acid Modification of Porcine Mucin on Its Drug Release and Skin Permeation Properties in Insulin Transdermal Films

Background: The transdermal delivery of insulin involving the use of polymers has been extensively reported. More recently, the use of mucoadhesive or bioadhesive polymers as an insulin base in its formulation is gaining attention possibly due to the penetration enhancing properties of the polymers. Objectives: This study aimed at determining the effect of acid-modified porcine mucin powder on the release and permeation of insulin in transdermal films. Methods: Various batches of insulin films were prepared by solvent casting method using polysorbate 80 as an emulsifying agent and acid-treated and untreated mucin powders as a base. The films were evaluated for their physical properties, folding endurance, moisture content and uptake, drug content, bioadhesion, in vitro release, ex vivo permeation, and in vivo glucose-lowering activity. Results: The prepared insulin films had a weight range of 0.21-0.27 g, folding endurance of 101-103, moisture content and uptake of 13.73%-18.57% and 11.70%-22.30%, respectively, and drug content of 96%-101%. The bioadhesion of the films prepared with acid-treated mucin was within the range of 0.088-0.186 Nm-1 as against 0.055 Nm-1 of the films prepared with untreated mucin. The in vitro release profiles showed a release of 95% insulin from films prepared with untreated mucin within 2 h while the films made with acid-treated mucin gave a release of about 60%-73% over the same period, indicating a slower release. Animals that received acid-treated mucin-base insulin films showed delayed but sustained blood-glucose-lowering up to 70% and for films prepared with untreated mucin 55% within 12 h.  Conclusion: Insulin transdermal films prepared with acid-modified mucin powder gave superior bioadhesive strength values. They also showed improved drug permeation enhancing ability and achieving up to 70% blood glucose lowering in diabetic rats.