Characteristics of rhVEGF release from topical hydrogel formulations.
OBJECTIVE
To study recombinant human vascular endothelial growth factor (rhVEGF), the release characteristics from topical gel formulations, and its interaction with the gelling agents.


METHODS
The release kinetics were followed by quantifying rhVEGF that diffused into the receptor chamber of Franz cells. Analytical ultracentrifuge (AUC) was used to characterize the sedimentation velocity of rhVEGF experienced in the gel. The interactions were characterized by isothermal calorimetry (ITC), and rhVEGF conformation was assessed by circular dichroism (CD).


RESULTS
The fraction of protein released was linear with the square root of time. The release rate constants did not show significant change within a wide range of bulk viscosities created by different concentrations of hydroxypropyl methylcellulose (HPMC) or MC gels. Sedimentation velocity determined by AUC generated comparable sedimentation coefficients of protein in these gels. AUC and ITC revealed no significant interaction between rhVEGF and HPMC and some change on secondary structure of the protein by Far UV CD, which was not the case with carboxymethyl cellulose (CMC).


CONCLUSIONS
Microviscosity, not bulk viscosity, was the key factor for the release of rhVEGF from cellulosic gels such as HPMC. Interaction between rhVEGF and CMC resulted in slower, and reduced amount of, release from the gel.
Ji
Junyan A
JA
Late Stage Pharmaceutical and Processing Development, 1 DNA Way, South San Francisco, California 94080, USA. jji@gene.com
Liu
Jun
J
Shire
Steven J
SJ
Kamerzell
Tim J
TJ
Hong
Sung
S
Billeci
Karen
K
Shen
Ye
Y
Wang
Y John
YJ
D000287:Administration, Topical; D002942:Circular Dichroism; D004058:Diffusion; D016503:Drug Delivery Systems; D005782:Gels / Q000737:chemistry*; D006801:Humans; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000737:chemistry; D014461:Ultracentrifugation; D042461:Vascular Endothelial Growth Factor A / Q000008:administration & dosage* / Q000737:chemistry; D014783:Viscosity
D005782:Gels; D011994:Recombinant Proteins; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A