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Due to the obvious advantages of long-acting peptide and protein drugs, strategies to prolong plasma half life time of such compounds are highly on demand. Short plasma half life times are commonly due to fast renal clearance as well as to enzymatic degradation occurring during systemic circulation. Modifications of the peptide/protein can lead to prolonged(More)
Within the past 20 years, a considerable amount of work has been published on chitosan and its potential use in drug delivery systems. In contrast to all other polysaccharides having a monograph in a pharmacopeia, chitosan has a cationic character because of its primary amino groups. These primary amino groups are responsible for properties such as(More)
PURPOSE To improve the mucoadhesive properties of polycarbophil by the introduction of sulfhydryl groups. METHODS Mediated by a carbodiimide, cysteine was covalently bound to polycarbophil (PCP) forming amide bonds between the primary amino group of the amino acid and the carboxylic acid moieties of the polymer. The amount of covalently attached cysteine(More)
The peroral administration of peptide drugs is a major challenge to pharmaceutical science. In order to provide a sufficient bioavailability of these therapeutic agents after oral dosing, several barriers encountered with the gastrointestinal (GI) tract have to be overcome by a suitable galenic. One of these barriers is caused by proteolytic enzymes,(More)
The purpose of this study was to develop thiolated nanoparticles to enhance the bioavailability for the nasal application of leuprolide. Thiolated chitosan-thioglycolic acid (chitosan-TGA) and unmodified chitosan nanoparticles (NPs) were developed via ionic gelation with tripolyphosphate (TPP). Leuprolide was incorporated during the formulation process of(More)
It was the aim of this study to develop a sustained parenteral peptide (DALCE) delivery system by the immobilization of DALCE to thiolated carboxymethyl dextran-cysteine (CMD-Cys) via disulfide bond formation. The resulting CMD-Cys-DALCE conjugate displayed a 22.6±7.9% (m/m) of DALCE (mean±S.D.; n=3). The conjugation of DALCE with CMD-Cys was confirmed by(More)
The aim of this study was to improve the properties of chitosan as excipient in drug delivery systems by the covalent attachment of thiol moieties. This was achieved by the modification of chitosan with 2-iminothiolane. The resulting chitosan-4-thio-butyl-amidine conjugates (chitosan-TBA conjugates) displayed up to 408.9+/-49.8 micromol thiol groups per(More)
This study examined the rheological and mucoadhesive properties of a self-crosslinking anionic thiolated polymer in vitro. Mediated by a carbodiimide, L-cysteine was covalently bound to poly(acrylic acid) of 450 kDa molecular mass. The resulting thiolated polymers (conjugates I and II) contained 90.5+/-15.8 and 511.6+/-52 micromol thiol groups per gram(More)
Thiolated polymers or designated thiomers are obtained by immobilization of sulhydryl bearing ligands on the polymeric backbone of well-established polymers such as poly(acrylates) or chitosans. This functionalization leads to significantly improved mucoadhesive properties compared to the corresponding unmodified polymers, as disulfide bonds between thiol(More)
The derivatization of the primary amino groups of chitosan with coupling reagents bearing thiol functions leads to the formation of thiolated chitosans. So far, three types of thiolated chitosans have been generated: chitosan-cysteine conjugates, chitosan-thioglycolic acid conjugates and chitosan-4-thio-butyl-amidine conjugates. Various properties of(More)