ABSTRACT
Poly(acrylic acid) (PAA) and methylcellulose (MC) are able to form hydrogen-bonded interpolymer complexes (IPCs) in aqueous solutions. In this study, the complexation between PAA and MC is explored in dilute aqueous solutions under acidic conditions. The formation of stable nanoparticles is established, whose size and colloidal stability are greatly dependent on solution pH and polymers ratio in the mixture. Poly(acrylic acid) and methylcellulose are also used to prepare polymeric films by casting from aqueous solutions. It is established that uniform films can be prepared by casting from polymer mixture solutions at pH 3.4-4.5. At lower pHs (pH < 3.0) the films have inhomogeneous morphology resulting from strong interpolymer complexation and precipitation of polycomplexes, whereas at higher pHs (pH 8.3) the polymers form fully immiscible blends because of the lack of interpolymer hydrogen-bonding. The PAA/MC films cast at pH 4 are shown to be non-irritant to mucosal surfaces. These films provide a platform for ocular formulation of riboflavin, a drug used for corneal cross-linking in the treatment of keratoconus. An in vitro release of riboflavin as well as an in vivo retention of the films on corneal surfaces can be controlled by adjusting PAA/MC ratio in the formulations.
Subject(s)
Acrylic Resins/chemistry , Drug Delivery Systems/methods , Methylcellulose/chemistry , Nanoparticles/administration & dosage , Nanoparticles/chemistry , Riboflavin/administration & dosage , Administration, Ophthalmic , Animals , Drug Evaluation, Preclinical/methods , Gastropoda/drug effects , Hydrogen Bonding , Hydrogen-Ion Concentration , Mucous Membrane/drug effects , Rabbits , Riboflavin/pharmacokinetics , SolutionsABSTRACT
It has been found that hydrogels may be formed by microwave irradiation of aqueous solutions containing appropriate combinations of polymers. This new method of hydrogel synthesis yields sterile hydrogels without the use of monomers, eliminating the need for the removal of unreacted species from the final product. Results for two particularly successful combinations, poly(vinyl alcohol) with either poly(acrylic acid) or poly(methylvinylether-alt-maleic anhydride), are presented. Irradiation using temperatures of 100-150 °C was found to yield hydrogels with large equilibrium swelling degrees of 500-1000 g g(-1) . Material leached from both types of hydrogel shows little cytotoxicity towards HT29 cells.
Subject(s)
Hydrogels/chemical synthesis , Polymers/chemistry , Biocompatible Materials/chemistry , HT29 Cells , Humans , Hydrogels/chemistry , Microwaves , Polyvinyl Alcohol/chemistry , Solutions , TemperatureABSTRACT
Free-radical copolymerization of 2-hydroxyethyl methacrylate with 2-hydroxyethyl acrylate can be successively utilized for the synthesis of water-soluble polymers and hydrogels with excellent physicochemical properties, thus showing promise for pharmaceutical and biomedical applications. In the work presented it has been demonstrated that water-soluble copolymers based on 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate exhibit lower critical solution temperature in aqueous solutions, whereas the corresponding high molecular weight homopolymers do not have this unique property. The temperature-induced transitions observed upon heating the aqueous solutions of these copolymers proceed via liquid-liquid phase separation. The hydrogels were also synthesized by copolymerizing 2-hydroxyethyl methacrylate and 2-hydroxyethyl acrylate in the absence of a bifunctional cross-linker. The cross-linking of these copolymers during copolymerization is believed to be due to the presence of bifunctional admixtures or transesterification reactions. Transparency, swelling behavior, mechanical properties, and porosity of the hydrogels are dependent upon the monomer ratio in the copolymers. Hydrogel samples containing more 2-hydroxyethyl methacrylate are less transparent, have lower swelling capacity, higher elastic moduli, and pores of smaller size. The assessment of the biocompatibility of the copolymers using the slug mucosal irritation test revealed that they are also less irritant than poly(acrylic acid).
Subject(s)
Acrylates/chemistry , Biocompatible Materials/chemical synthesis , Drug Carriers/chemical synthesis , Hydrogels/chemical synthesis , Methacrylates/chemistry , Animals , Biocompatible Materials/adverse effects , Biocompatible Materials/chemistry , Biocompatible Materials/pharmacology , Biomechanical Phenomena , Chemistry, Pharmaceutical , Drug Carriers/adverse effects , Drug Carriers/chemistry , Elasticity , Gastropoda/drug effects , Hydrogels/adverse effects , Hydrogels/chemistry , Hydrogels/pharmacology , Materials Testing , Molecular Weight , Mucous Membrane/drug effects , Porosity , Solubility , Temperature , Water/chemistryABSTRACT
Mucoadhesive polymeric films have been prepared based on blends of chitosan and hydroxyethylcellulose. The blends have been characterized by IR spectroscopy, DSC, WAXD, TGA, SEM, and mechanical testing. It is demonstrated that the mechanical properties of chitosan are improved significantly upon blending with hydroxyethylcellulose. An increase in hydroxyethylcellulose content in the blends makes the materials more elastic. The thermal treatment of the blends at 100 degrees C leads to partial cross-linking of the polymers and formation of water-insoluble but swellable materials. The adhesion of the films towards porcine buccal mucosa decreases with increasing hydroxyethylcellulose content in the blends.
