title: The effect of molecular weight, drug load, and charge of gelatin-MTX conjugates on growth inhibition of HL-60 leukemia cells.
abstract: OBJECTIVE
  Gelatin-methotrexate conjugates (G-MTX) with known molecular weight (MW), drug load, and charge were prepared and evaluated for growth inhibition on leukemia cells.
  
  
  METHODS
  Gelatin (34 to 171 kDa) was reacted with a carbodiimide to prepare G-MTX with high (G-MTX-H) and low (G-MTX-L) drug loads. Cationic conjugates were prepared by ethylenediamine modification. MTX:gelatin molar ratios were determined spectrophotometrically. Isoelectric focusing electrophoresis (IEF) and turbidity were used to measure isoelectric points (IEP). Growth inhibition profiles and IC50 values were determined on HL-60 cells using a modified MTT assay.
  
  
  RESULTS
  IC50 values of anionic G-MTX-L (drug loads 0.5:1 to 2.2:1) increased linearly from 46 to 180 nM with MW. But, IC50 values for anionic G-MTX-H (drug loads 7.4:1 to 25:1) showed little, if any, MW dependence and were about two times higher. IC50 values for cationic G-MTX-L ranged from 770 to 2,900 nM and the relationship with MW was non-linear.
  
  
  CONCLUSIONS
  The growth inhibition ranking was MTX>anionic G-MTX-L>anionic G-MTX-H>cationic G-MTX-L. High drug load may hinder lysosomal enzyme degradation and drug release and contribute to suppression of the MW effect observed with G-MTX-L. A mechanism change is suggested as the cationic conjugates increase to the highest MW.
authors.affiliation: Department of Pharmaceutical Sciences, Philadelphia College of Pharmacy, University of the Sciences in Philadelphia, 600 South 43rd Street, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Chao-Sheng
authors.initials: CS
authors.lastname: Chen
authors.forename: Clyde M
authors.initials: CM
authors.lastname: Ofner
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000737:chemistry / Q000494:pharmacology*; D002234:Carbodiimides / Q000737:chemistry; D049109:Cell Proliferation / Q000187:drug effects*; D002626:Chemistry, Pharmaceutical; D004305:Dose-Response Relationship, Drug; D004337:Drug Carriers; D004339:Drug Compounding; D005029:Ethylenediamines / Q000737:chemistry; D005780:Gelatin / Q000737:chemistry*; D018922:HL-60 Cells; D006801:Humans; D020128:Inhibitory Concentration 50; D007525:Isoelectric Focusing; D007938:Leukemia / Q000473:pathology*; D008727:Methotrexate / Q000737:chemistry / Q000494:pharmacology*; D008970:Molecular Weight; D009391:Nephelometry and Turbidimetry; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties
chemical_list: D000964:Antimetabolites, Antineoplastic; D002234:Carbodiimides; D004337:Drug Carriers; D005029:Ethylenediamines; C031234:ethylenediamine; D005780:Gelatin; D008727:Methotrexate