title: Polyacrylic acid polymers hydrogels intended to topical drug delivery: preparation and characterization.
abstract: BACKGROUND
  Bioadhesiviness of polyacrylic acid polymers make them promising hydrogels to design topical drug delivery systems, allowing a close contact with biological substrate as well as an enhanced local concentration gradient, both factors that may improve the biological performance of the drugs.
  
  
  OBJECTIVE
  Texture and bioadhesive properties of hydrogels were assessed by using texture analyzer and they were correlated with their rheological behavior and performance as drug delivery systems.
  
  
  METHODS
  Aqueous dispersions of both polymers were prepared at 0.5%, 1.0% and 1.5% w/v. Hardness, compressibility, adhesiveness, cohesiveness, bioadhesion, continuous flow, oscillatory dynamic test and in vitro drug release were evaluated.
  
  
  RESULTS
  Rheological and texture parameters were dependent on polymer concentration and C974P polymer built the strongest structures. Both 1.5% hydrogels presented high bioadhesion values. About 50% of the metronidazole (MTZ) was sustained released from hydrogels within 2 h with an initial burst release at early stage. After, the release rates were decreased and 10% of the MTZ was released in the next 10 h. The drug release process was driven by Fickian diffusion and complex mechanism for PP and C974P hydrogels, respectively.
  
  
  CONCLUSIONS
  The set of results demonstrated that these hydrogels are promising to be used as topical controlled drug delivery system.
authors.affiliation: Department of Drugs and Pharmaceuticals, School of Pharmaceutical Sciences, São Paulo State University - UNESP , Araraquara, SP , Brazil.
authors.forename: Giovana
authors.initials: G
authors.lastname: Calixto
authors.forename: Ana Carolina
authors.initials: AC
authors.lastname: Yoshii
authors.forename: Hilris
authors.initials: H
authors.lastname: Rocha e Silva
authors.forename: Beatriz
authors.initials: B
authors.lastname: Stringhetti Ferreira Cury
authors.forename: Marlus
authors.initials: M
authors.lastname: Chorilli
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000268:Adhesiveness; D000287:Administration, Topical; D000890:Anti-Infective Agents / Q000008:administration & dosage*; D003692:Delayed-Action Preparations / Q000737:chemistry*; D016503:Drug Delivery Systems; D006244:Hardness; D020100:Hydrogels / Q000737:chemistry*; D008795:Metronidazole / Q000008:administration & dosage*; D012212:Rheology
chemical_list: D000180:Acrylic Resins; D000890:Anti-Infective Agents; D003692:Delayed-Action Preparations; D020100:Hydrogels; D008795:Metronidazole; C006903:carbopol 940
keywords: Bioadhesion; hydrogel; metronidazole; polyacrylic acid polymers; topical drug delivery system