Highly efficient grafting of silazanes to the inner surface of the vials under mild conditions by surface engineering to improve the chemical durability

Abstract

As the composition of drugs has become more complex, the chemical durability of glass has been challenged. In this study, two silazanes, n-n-butyl-azido-2,2-dimethoxysilazane (BADMACP) and hexamethyldisilazane (HMDS) were used separately to efficiently modify the inner surfaces of vials under mild conditions. These two silazanes were reacted with the –OH groups on the inner surface of the vials through Si-N bonds, and grafted by O-Si bonds to form a functional hydrolysis-resistant surface with excellent stability. The success of the chemical modification was confirmed by colorimetric staining experiments, Fourier transform infrared spectra, water contact angle and the morphology of the inner surface of the vials before and after modification. The water contact angle was increased from unmodified 65° to more than 100°, and improved the hydrolytic resistance of the glass by modifying the hydrophobicity of the inner surface of the glass vial. Hydrothermal aging tests were performed before and after modification defined by the pharmacopeias, and the volume of 0.01 M HCl consumed during titration decreased by 88 % and 86 %, indicating that metal ion precipitation is greatly reduced, effectively reducing the risk of glass delamination. It is worth mentioning that the surface modification engineering of the inner surface of the vials with HMDS and BADMSCP can significantly improve the barrier properties of the inner surface of the vials without affecting the appearance and the transmittance of the vials.