title: Development and characterization of lysine-methotrexate conjugate for enhanced brain delivery.
abstract: BACKGROUND
  Methotrexate (MTX), an anticancer drug of choice, has poor permeability across blood-brain barrier (BBB) making it unsuitable for brain tumor application. Its brain availability and scope of application was improved by preparation of reversible conjugate with lysine by capitalizing the endogenous transport system of lysine at BBB.
  
  
  METHODS
  To enhance its delivery to brain, MTX was reversibly conjugated with l-Lysine by an amide linkage. It was characterized by advanced spectroscopy techniques including IR, NMR and MS. Furthermore, conjugate was assessed for stability, toxicity and drug release ability. In vivo distribution studies were done by radioscintigraphy study using99mTc radioisotope.
  
  
  RESULTS
  The structure of prodrug was confirmed by1H-NMR,13C-NMR and Mass. The m/e (mass to charge ratio) fragment was found at [M + H] 711.32 in Mass spectra. Stability and metabolic studies suggested that conjugate was stable at physiological pH (in Phosphate buffer pH 7.4 t1/2is 70.25 ± 2.17 h and in plasma t1/2is 193.57 ± 2.03 min) and circulated adequately to release MTX slowly in brain. In vivo biodistribution study showed that prodrug significantly increased the level of MTX in brain when compared with pharmacokinetic parameter of parent drug.
  
  
  CONCLUSIONS
  The brain permeability of MTX was enhanced significantly by this conjugate.
authors.affiliation: a Columbia Institute of Pharmacy , Tekari , Raipur , Chhattisgarh , India and.
authors.forename: Vijay Kumar
authors.initials: VK
authors.lastname: Singh
authors.affiliation: b School of Pharmaceutical Sciences, Siksha O Anusandhan University , Bhubaneswar , Odisha , India.
authors.forename: Bharat Bhusan
authors.initials: BB
authors.lastname: Subudhi
mesh_terms: D001812:Blood-Brain Barrier / Q000737:chemistry / Q000378:metabolism*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D004337:Drug Carriers / Q000737:chemistry*; D065546:Drug Liberation; D004355:Drug Stability; D009682:Magnetic Resonance Spectroscopy; D008727:Methotrexate / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D011355:Prodrugs / Q000737:chemistry*; D014018:Tissue Distribution
chemical_list: D004337:Drug Carriers; D011355:Prodrugs; C034334:lysine-methotrexate; D008727:Methotrexate
keywords: Amino acid transport system; brain delivery; conjugates; lysine; methotrexate