Synthesis and in vitro evaluation of chitosan-EDTA-protease-inhibitor conjugates which might be useful in oral delivery of peptides and proteins.
OBJECTIVE
To develop a novel mucoadhesive polymer that protects peptide drugs from degradation by secreted as well as membrane-bound proteases in the intestine, and to evaluate this polymer in vitro.


METHODS
The serine protease inhibitors antipain, chymostatin and elastatinal were covalently linked to chitosan (poly-[1-->4]-beta-D-glucosamine). Thereafter, the complexing agent ethylenediaminetetraacetic acid (EDTA) was bound to the remaining primary amino groups of the polymer. The inhibitory effect of the resulting polymer-conjugate towards trypsin (EC 3.4.21.4), chymotrypsin (EC 3.4.21.1), elastase (3.4.21.36), carboxypeptidase A (EC 3.4.17.1), carboxypeptidase B (EC 3.4.17.2) and aminopeptidase N (EC 3.4.11.2) as well as its mucoadhesive properties were evaluated in vitro.


RESULTS
Whereas the novel polymer-conjugate exhibited excellent swelling properties, its adhesive force was under our assay conditions 42% lower than that of unmodified chitosan. However, the polymer-conjugate showed a strong inhibitory activity towards all tested serine proteases. Due to its additional high binding affinity towards bivalent metal ions, it also inhibited the Zn(2+)-dependent exopeptidases carboxypeptidase A, B and aminopeptidase N.


CONCLUSIONS
The novel mucoadhesive polymer-conjugate described in this study seems to be a useful tool in overcoming the enzymatic barrier to perorally administered therapeutic peptides and proteins.
Bernkop-Schnürch
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Center of Pharmacy, University of Vienna, Austria/Europe. andreas.bernkop-schnuerch@univie.ac.at
Scerbe-Saiko
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D000269:Adhesives / Q000138:chemical synthesis* / Q000737:chemistry; D000284:Administration, Oral; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry; D048271:Chitosan; D004337:Drug Carriers; D004341:Drug Evaluation; D004492:Edetic Acid / Q000737:chemistry*; D010455:Peptides / Q000008:administration & dosage*; D011480:Protease Inhibitors / Q000737:chemistry*; D011506:Proteins / Q000008:administration & dosage*; D013718:Tensile Strength
D000269:Adhesives; D004337:Drug Carriers; D010455:Peptides; D011480:Protease Inhibitors; D011506:Proteins; D002686:Chitin; D048271:Chitosan; D004492:Edetic Acid