Crystallization and growth control of sulfathiazole using 2,2,6,6-tetramethylpiperidinooxy cellulose nanofibers gel

The influence of 2,2,6,6-Tetramethylpiperidinooxy (TEMPO) cellulose nanofibers (TCNF) on the nucleation and growth of sulfathiazole (STZ) crystals is uncovered, aiding in the precise control of drug crystal morphology. To elucidate the mechanism by which TCNF regulates the nucleation and growth of STZ crystals, cooling crystallization experiments and molecular simulations were conducted. Initially, the crystal forms of STZ in pure water were determined. Subsequently, crystallization experiments with the addition of TCNF were conducted. The experiments aimed to investigate their effects on crystal form and crystal habits. The results revealed that a pure Form III was obtained due to the hydrogen bonding interactions on the surface of TCNF. Molecular simulations helped better explain the influence on specific crystal faces. This study indicates that the influence of TCNF on the characteristics of STZ crystals is mediated through interaction with the z-axis crystal facets, leading to the formation of block-shaped crystals. In addition, the higher concentration of TCNF forms a local closed space, resulting in blocked mobility, allowing STZ molecules in the solution to grow at the defects of STZ crystallization.