title: Oral peptide drug delivery: polymer-inhibitor conjugates protecting insulin from enzymatic degradation in vitro.
abstract: A drug-carrier matrix has been developed which protects embedded insulin from degradation by the luminally secreted serine-proteases trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1) and elastase (EC 3.4.21.36) in vitro. Increasing amounts of the Bowman-Birk inhibitor (BBI) and elastatinal, respectively, were thereby covalently bound to the mucoadhesive polymer sodium carboxymethylcellulose (Na-CMC). The inhibitory efficacy of resulting polymers was evaluated. On the one hand, all polymer-BBI conjugates showed a strong inhibitory activity towards trypsin and chymotrypsin whereas it was markedly lower towards elastase. The polymer-elastatinal conjugates, on the other hand, displayed a comparatively higher inhibitory activity towards elastase. In an artificial intestinal fluid containing trypsin, chymotrypsin and elastase in physiological concentrations insulin, being incorporated in unmodified Na-CMC, was rapidly degraded at 37 degrees C. Within 1 h 98.7 +/- 0.4% (mean +/- SD, n = 3) of the peptide drug were thereby metabolized. On the contrary, the incorporation of insulin in a mixture of the two polymer-inhibitor conjugates CMC-BBI (40%; w/w) and CMC-elastatinal conjugate (60%; w/w) led to a peptide degradation of 22.3 +/- 2.5% (mean +/- SD, n = 3) within the same time period. Even after 4 h of incubation, 33.6 +/- 3.2% (mean +/- SD, n = 3) of the therapeutic agent remained stable towards enzymatic attack. Hence, the polymer-inhibitor conjugates described in this study seem to be a useful tool in overcoming the luminal enzymatic barrier in peroral insulin delivery.
authors.affiliation: Institute of Pharmaceutical Technology, Center of Pharmacy, University of Vienna, Austria.
authors.forename: M K
authors.initials: MK
authors.lastname: Marschütz
authors.forename: A
authors.initials: A
authors.lastname: Bernkop-Schnürch
mesh_terms: D000284:Administration, Oral; D000595:Amino Acid Sequence; D001672:Biocompatible Materials / Q000737:chemistry; D002266:Carboxymethylcellulose Sodium / Q000737:chemistry; D002918:Chymotrypsin / Q000378:metabolism; D004337:Drug Carriers; D007202:Indicators and Reagents; D007328:Insulin / Q000008:administration & dosage* / Q000378:metabolism; D007700:Kinetics; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000737:chemistry*; D010196:Pancreatic Elastase / Q000378:metabolism; D010455:Peptides / Q000008:administration & dosage*; D011485:Protein Binding; D011487:Protein Conformation; D015842:Serine Proteinase Inhibitors / Q000737:chemistry; D014357:Trypsin / Q000378:metabolism; D014358:Trypsin Inhibitor, Bowman-Birk Soybean / Q000737:chemistry*
chemical_list: D001672:Biocompatible Materials; D004337:Drug Carriers; D007202:Indicators and Reagents; D007328:Insulin; D009842:Oligopeptides; D010455:Peptides; D015842:Serine Proteinase Inhibitors; D014358:Trypsin Inhibitor, Bowman-Birk Soybean; D002918:Chymotrypsin; D010196:Pancreatic Elastase; D014357:Trypsin; D002266:Carboxymethylcellulose Sodium; C010718:elastatinal