title: Preparation and characterization of freeze-dried chitosan-poly(ethylene oxide) hydrogels for site-specific antibiotic delivery in the stomach.
abstract: OBJECTIVE
  The purpose of this study was to develop novel drug delivery systems with pH-sensitive swelling and drug release properties for localized antibiotic delivery in the stomach.
  
  
  METHODS
  The drug delivery systems were synthesized by crosslinking chitosan and poly(ethylene oxide) (PEO) in a blend to form semi-interpenetrating polymer network (semi-IPN). Scanning electron microscopy was used to compare the surface and bulk morphology of the freeze-dried and air-dried chitosan-PEO semi-IPN. The hydrogels were allowed to swell and release the antibiotics--amoxicillin and metronidazole--in enzyme-free simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.2) at 37 degrees C.
  
  
  RESULTS
  Freeze-dried chitosan-PEO semi-IPN with a porous matrix had swollen extensively as compared to the air-dried hydrogel. The swelling ratio of freeze-dried and air-dried chitosan-PEO semi-IPN after 1 h in SGF was 16.1 and 2.30, respectively. More than 65% of the entrapped amoxicillin and 59% of metronidazole were released from the freeze-dried chitosan-PEO semi-IPN after 2 h in SGF.
  
  
  CONCLUSIONS
  The results of this study suggest that freeze-dried chitosan-PEO semi-IPN could be useful for localized delivery of antibiotics in the acidic environment of the gastric fluid.
authors.affiliation: Department of Pharmaceutical Sciences, Northeastern University, Boston, Massachusetts 02115, USA.
authors.forename: V R
authors.initials: VR
authors.lastname: Patel
authors.forename: M M
authors.initials: MM
authors.lastname: Amiji
mesh_terms: D000658:Amoxicillin / Q000008:administration & dosage* / Q000378:metabolism; D000994:Antitrichomonal Agents / Q000008:administration & dosage* / Q000378:metabolism; D001672:Biocompatible Materials; D002686:Chitin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D048271:Chitosan; D016503:Drug Delivery Systems / Q000592:standards; D005612:Freeze Drying; D005750:Gastric Juice / Q000378:metabolism; D005753:Gastric Mucosa / Q000378:metabolism; D005782:Gels; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007419:Intestinal Secretions / Q000378:metabolism; D008795:Metronidazole / Q000008:administration & dosage* / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D010406:Penicillins / Q000008:administration & dosage* / Q000378:metabolism; D011092:Polyethylene Glycols / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism*; D013501:Surface-Active Agents / Q000008:administration & dosage / Q000737:chemistry / Q000378:metabolism
chemical_list: D000994:Antitrichomonal Agents; D001672:Biocompatible Materials; D005782:Gels; D010406:Penicillins; D013501:Surface-Active Agents; D002686:Chitin; D008795:Metronidazole; D011092:Polyethylene Glycols; D000658:Amoxicillin; D048271:Chitosan