Novel application of polioviral capsid: development of a potent and prolonged oral calcitonin using polioviral binding ligand and Tat peptide

Context: Poor absorption and proteolytic degradation are major obstacles of orally administered peptide drugs including calcitonin. Cell penetrating peptides (CPPs) and receptor binding ligands are interesting tools for the application in the delivery of these drugs.

Objective: To investigate the enhancements of in vitro and in vivo salmon calcitonin (sCT) activity by Tat, a trans-activating transcriptional peptide and VP1 peptide (V) from polioviral capsid.

Materials and methods: Tat/sCT, V/sCT and V/Tat/sCT mixtures at various molar ratios were prepared and investigated for in vitro and in vivo activities of sCT.

Results: Tat could increase in vitro sCT activity both in colon adenocarcinoma (HT-29) and mouth epidermal carcinoma (KB) cells. V/sCT (6:1) showed significant increase of intracellular calcium in HT-29 cells. V/Tat/sCT (6:1:1) gave highest increase of intracellular calcium in both cells. Oral administered Tat/sCT (1:1) showed comparable hypocalcemic effect to sCT injection with prolonged action. V/Tat/sCT (6:1:1) demonstrated hypocalcemic effect at 12?h after administration but no hypocalcemic effect was observed from V/sCT.

Discussion: Positive charge from Tat might facilitate sCT uptake and absorption. Increasing of intracellular calcium in HT-29 cells by V but lacking of hypocalcemic effect from V/sCT in mice indicated the ligand-receptor mediated delivery of sCT by the interaction between V and PVR.

Conclusion: Potential application of V and Tat in oral calcitonin delivery system was demonstrated. Further study in a proper PVR bearing host is still needed to provide more useful information for the application of V in the development of drug delivery systems.