title: Preactivated thiomers as mucoadhesive polymers for drug delivery.
abstract: This study was aimed to synthesize polymeric excipients with improved mucoadhesive, cohesive and in situ-gelling properties to assure a prolonged retention time of dosage forms at a given target site, thereby achieving an increased uptake and improved oral bioavailability of certain challenging therapeutic agents such as peptides and proteins. Accordingly, poly(acrylic acid)-cysteine-2-mercaptonicotinic acid (PAA-cys-2MNA) conjugates were synthesized by the oxidative S-S coupling of PAA-cys (100-, 250- and 450 kDa) with 2-mercaptonicotinic acid (2MNA). Unmodified PAAs, PAAs-cys (thiomers) and PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates were compressed into tablets to perform disintegration tests, mucoadhesion studies and rheological measurements. Moreover, cytotoxicty of the polymers was determined using Caco-2 cells. The resulting PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates displayed 113.5 ± 12.7, 122.7 ± 12.2 and 117.3 ± 4.6 μmol/g of 2-mercaptonicotinic acid, respectively. Due to the immobilization of 2MNA, the PAA-cys-2MNA (pre-activated thiomers) conjugates exhibit comparatively higher swelling properties and disintegration time to the corresponding unmodified and thiolated polymers. On the rotating cylinder, tablets based on PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates displayed 5.0-, 5.4- and 960-fold improved mucoadhesion time in comparison to the corresponding unmodified PAAs. Results achieved from tensile studies were found in good agreement with the results obtained by rotating cylinder method. The apparent viscosity of PAA-cys-2MNA (100-, 250- and 450 kDa) conjugates was improved 1.6-, 2.5- and 206.2-fold, respectively, in comparison to the corresponding unmodified PAAs. Moreover, pre-activated thiomers/mucin mixtures showed a time dependent increase in viscosity up to 24 h, leading to 7.0-, 18.9- and 2678-fold increased viscosity in comparison to unmodified PAAs (100-, 250- and 450 kDa), respectively. All polymers were found non-toxic over Caco-2 cells. Thus, on the basis of achieved results the pre-activated thiomers seem to represent a promising generation of mucoadhesive polymers which are safe to use for prolonged residence time of drug delivery systems to target various mucosa.
authors: Department of Pharmaceutical Technology, Leopold-Franzens-University Innsbruck, Innsbruck, Austria. andreas.bernkop@uibk.ac.at
authors: Javed
authors: J
authors: Iqbal
authors: Gul
authors: G
authors: Shahnaz
authors: Sarah
authors: S
authors: Dünnhaupt
authors: Christiane
authors: C
authors: Müller
authors: Fabian
authors: F
authors: Hintzen
authors: Andreas
authors: A
authors: Bernkop-Schnürch
mesh_terms: D000180:Acrylic Resins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology*; D000269:Adhesives / Q000494:pharmacology*; D000818:Animals; D001681:Biological Assay; D018938:Caco-2 Cells; D016923:Cell Death / Q000187:drug effects; D016503:Drug Delivery Systems / Q000379:methods*; D006244:Hardness / Q000187:drug effects; D006801:Humans; D009077:Mucins / Q000378:metabolism; D009092:Mucous Membrane / Q000187:drug effects*; D009539:Nicotinic Acids / Q000737:chemistry / Q000494:pharmacology*; D010078:Oxazines / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000737:chemistry / Q000494:pharmacology*; D034421:Sus scrofa; D013718:Tensile Strength / Q000187:drug effects; D014783:Viscosity / Q000187:drug effects; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000180:Acrylic Resins; D000269:Adhesives; D009077:Mucins; D009539:Nicotinic Acids; D010078:Oxazines; D013438:Sulfhydryl Compounds; D014966:Xanthenes; C005843:resazurin; C006903:carbopol 940; C083470:2-mercaptonicotinic acid