| Popis: |
In biopharmaceutical products for therapeutic usage, proteins represent the most important substance class. For the quality control of insulins as representatives of life saving pharmaceuticals, analytical methods are needed allowing more than a total protein quantification in vials. Chemical and physical influences such as unstable temperatures or shear rate exposure under storage lead to misfolding, nucleation and subsequent fibril forming of the insulins. The hypothesis is that these processes go parallel with a decrease in bioactivity. Infrared spectroscopy has been successfully utilized for secondary structure analysis in cases of protein folding and fibril formation. A reliable method for the quantification of the secondary structure changes has been developed by using insulin dry-film Fourier-Transform infrared spectroscopy in combination with the attenuated total reflection (ATR) technique and subsequent data analyses such as band-shift determination, spectral band deconvolution and principal component analysis. A systematic study of insulin spectra was carried out with model insulin specimens, available either as original formulations or as hormones purified by ultrafiltration, stored at 0°C, 20°C and 37 °C, respectively, for up to three months. Weekly ATR-measurements allowed the monitoring of the hormone secondary structure changes, which are supposedly negatively correlated with the insulin bioactivity. |
