title: Effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein during storage above the Tg.
abstract: OBJECTIVE
  To examine the potential of raffinose as an excipient in stabilizing protein and to study the effect of sucrose/raffinose mass ratios on the stability of co-lyophilized protein and amorphous solids during storage at an elevated temperature.
  
  
  METHODS
  Glucose-6-phosphate dehydrogenase (G6PDH) was colyophilized with sucrose and raffinose mixed at different mass ratios. The activity of dried G6PDH was monitored during storage at 44 degrees C. Thermal properties of sucrose/raffinose matrices were determined by differential scanning calorimetry (DSC).
  
  
  RESULTS
  Mass ratios of sucrose to raffinose did not affect the recovery of G6PDH activity after freeze-drying, but significantly affected the stability of freeze-dried G6PDH during storage. The sucrose-alone formulation offered the best enzyme stabilization during storage. With increasing fraction of raffinose, the G6PDH stability decreased, sugar crystallization inhibited, and crystal-melting temperature increased.
  
  
  CONCLUSIONS
  Despite the higher Tg of the formulations with higher fraction of raffinose, they provided less protection for G6PDH than did sucrose alone during storage. Our data do not support the prediction from recent thermophysical studies that raffinose should be superior to sucrose and trehalose as a potential excipient or stabilizer.
authors.affiliation: Department of Biological Sciences, National University of Singapore, Singapore.
authors.forename: P
authors.initials: P
authors.lastname: Davidson
authors.forename: W Q
authors.initials: WQ
authors.lastname: Sun
mesh_terms: D004355:Drug Stability; D004356:Drug Storage / Q000379:methods; D004795:Enzyme Stability; D005612:Freeze Drying / Q000379:methods; D005954:Glucosephosphate Dehydrogenase / Q000737:chemistry; D011506:Proteins / Q000737:chemistry*; D011887:Raffinose / Q000737:chemistry*; D013395:Sucrose / Q000737:chemistry*; D013696:Temperature
chemical_list: D011506:Proteins; D013395:Sucrose; D005954:Glucosephosphate Dehydrogenase; D011887:Raffinose