Structural Stability of Recombinant Human Growth Hormone (r-hGH) as a Function of Polymer Surface Properties

Despite the fact that r-hGH was first approved for use by FDA in 1995 and the conventional dosage form in the market has a limitation of daily subcutaneous injections, there remains a lack of sustained delivery system in the market. Nutropin depot, a long-acting dosage form of r-hGH was approved for marketing by FDA in 1999, however, it was discontinued in 2004. Since then, unabating efforts have been made to develop biodegradable polymer based formulations for r-hGH delivery. However, grey area is the comprehension of structural stability of r-hGH at an interface with the polymer and it is of utmost important to attain safe and efficacious sustained delivery system. The purpose of this study was to evaluate the changes in structure of r-hGH upon adsorption at biodegradable PLGA nanoparticles of different hydrophobicity as a function of pH.

DLS, fluorescence spectroscopy, and CD were collectively employed to evaluate structural changes in r-hGH.

The studies revealed that r-hGH is most stable with low to high hydrophobicity PLGA grades under pH 7.2 followed by 5.3.

Overall, the nature and magnitude of structural changes observed has a strong dependence on the pH and differences and degree of hydrophobicity of PLGA.