Mucoadhesive polymers as platforms for peroral peptide delivery and absorption: synthesis and evaluation of different chitosan–EDTA conjugates

• Published in: Journal of controlled release Vol. 50; no. 1; pp. 215 - 223
• Main Authors: Bernkop-Schnürch, Andreas, Krajicek, Martina E
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 02.01.1998; Elsevier
• Subjects: Absorption; Adhesiveness; Administration, Oral; Biological and medical sciences; Calcium - metabolism; Chitin - administration & dosage; Chitin - analogs & derivatives; Chitin - chemical synthesis; Chitin - chemistry; Chitosan; Chitosan–EDTA conjugate; Cobalt - metabolism; Drug Delivery Systems; Edetic Acid - administration & dosage; General pharmacology; Inhibition of luminal proteases; Medical sciences; Mucins - metabolism; Mucoadhesion; Peroral administration of (poly)peptides; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Protease Inhibitors - pharmacology; Zinc - metabolism; Chitosan–EDTA conjugate; Mucoadhesion; Inhibition of luminal proteases; Peroral administration of (poly)peptides; Viscosity; Pharmaceutical technology; Control release polymer; Oral administration; Enzyme inhibitor; Drug carrier; Mucus; EDTA; Adhesion; Absorption; Binding capacity; Polypeptide; Cations; Chitosan; Conjugated compound; Chemical synthesis
• ISSN: 0168-3659; 1873-4995
• DOI: 10.1016/S0168-3659(97)00136-3

The purpose of the present study was to synthesize and evaluate mucoadhesive polymers, exhibiting a high capacity to bind bivalent cations which are essential co-factors for intestinal proteolytic enzymes. Under the formation of amide bonds, the complexing agent EDTA was covalently bound to the primary amino groups of chitosan. One gram of the resulting conjugate with the lowest amount of remaining free amino groups (0.1±0.03%; mean±SD, n=3) based on free chitosan as 1.0 was capable of binding 1.4±0.1 mM calcium, 2.0±0.1 mM zinc and 1.9±0.03 mM cobalt (mean±SD, n=3) under intestinal pH-conditions, respectively. Whereas proteolytic activity of the serine proteases trypsin (EC 3.4.21.4), α-chymotrypsin (EC 3.4.21.1) and elastase (EC 3.4.21.36) could not be inhibited, proteolytic activity of the zinc proteases carboxypeptidase A (EC 3.4.17.1) and aminopeptidase N (EC 3.4.11.2) was strongly inhibited by the chitosan–EDTA conjugate. Moreover, it displays quick swelling properties in water and basic aqueous solutions. The adhesive force of the conjugate was even higher than of chitosan HCl. However, lowering the percentage of covalently attached EDTA on the polymer, leads to a significantly reduced adhesive force. According to these results, chitosan–EDTA conjugates exhibiting the lowest amount of remaining free amino groups, seem to be a useful tool in overcoming the enzymatic barrier for perorally administered therapeutic peptides.