title: Self-assembled hydrogel nanoparticles responsive to tumor extracellular pH from pullulan derivative/sulfonamide conjugate: characterization, aggregation, and adriamycin release in vitro.
abstract: OBJECTIVE
  To investigate some physicochemical properties of self-assembled hydrogel nanoparticles of pullulan acetate (PA) and sulfonamide conjugates, as a potential tumor targeting drug carrier responsive to tumor extracellular pH.
  
  
  METHODS
  A new class of pH-responsive polymers was synthesized by conjugating a sulfonamide, sulfadimethoxine (SDM), to succinylated pullulan acetate (coohPA). The polymers formed self-assembled PA/SDM hydrogel nanoparticles in aqueous media, which was confirmed by fluorometry and field emission-scanning electron microscopy. The pH-dependent behavior of the nanoparticles was examined by measuring transmittance, particle size and zeta potential. Adriamycin (ADR) was tested for loading into and release from the nanoparticles at various pHs.
  
  
  RESULTS
  The mean diameters of all PA/SDM nanoparticles tested were <70 nm. with a unimodal size distribution. The critical aggregation concentrations at pH 9.0 were as low as 3.16 microg/mL. The nanoparticles showed good stability at pH 7.4, but shrank and aggregated below pH 7.0. The ADR release rate from the PA/SDM nanoparticles was pH-dependent around physiological pH and significantly enhanced below a pH of 6.8.
  
  
  CONCLUSIONS
  The pH-responsive PA/SDM nanoparticles may provide some advantages for targeted anti-cancer drug delivery due to the particle aggregation and enhanced drug release rates at tumor pH.
authors.affiliation: Department of Materials Science and Engineering, Kwangju Institute of Science and Technology, Korea.
authors.forename: Kun
authors.initials: K
authors.lastname: Na
authors.forename: You Han
authors.initials: YH
authors.lastname: Bae
mesh_terms: D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000737:chemistry; D004317:Doxorubicin / Q000008:administration & dosage / Q000737:chemistry; D004337:Drug Carriers; D005936:Glucans / Q000737:chemistry*; D020100:Hydrogels; D006863:Hydrogen-Ion Concentration; D036103:Nanotechnology; D009369:Neoplasms / Q000737:chemistry; D010316:Particle Size; D013050:Spectrometry, Fluorescence; D013412:Sulfadimethoxine / Q000737:chemistry*
chemical_list: D000970:Antineoplastic Agents; D004337:Drug Carriers; D005936:Glucans; D020100:Hydrogels; D013412:Sulfadimethoxine; D004317:Doxorubicin; C009109:pullulan