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Oriented Crystallization on Organic Monolayers to Control Concomitant Polymorphism.

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Summary

Researchers controlled the crystallization of the antimicrobial drug sulfathiazole using a self-assembled monolayer (SAM). This method successfully guided the nucleation of a previously unknown sixth polymorph of the drug.

Keywords:
crystal engineeringcrystal growthmonolayerspolymorphismself-assembly

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Area of Science:

  • Materials Science
  • Crystallography
  • Pharmaceutical Science

Background:

  • Controlling crystal nucleation and growth is crucial for drug development and patent protection.
  • Sulfathiazole, a short-acting antimicrobial, exhibits complex concomitant crystallization with five known polymorphs due to its molecular flexibility.
  • Concomitant crystallization poses challenges in drug development, impacting patent litigation and intellectual property protection.

Purpose of the Study:

  • To investigate the use of functional self-assembled monolayers (SAMs) on gold surfaces for controlling the nucleation of flexible drugs.
  • To explore the potential of SAMs in guiding the formation of specific polymorphs, including novel metastable forms.
  • To address the challenges of concomitant crystallization in drug development through surface-mediated nucleation.

Main Methods:

  • Fabrication of functional self-assembled monolayers (SAMs) of organic thiols on gold substrates.
  • Controlled crystallization experiments of sulfathiazole on the designed SAM surfaces.
  • Characterization of nucleated crystal forms using spectroscopic techniques, thermal analysis, and X-ray diffraction.

Main Results:

  • The designed SAM surface effectively controlled the concomitant nucleation of sulfathiazole.
  • Crystallization on the SAM surface was primarily kinetically driven.
  • A previously unknown, sixth polymorph of sulfathiazole was successfully nucleated on the SAM surface.

Conclusions:

  • Functional SAMs provide an efficient strategy for controlling the nucleation of flexible drugs like sulfathiazole.
  • Surface-mediated crystallization can lead to the discovery of novel metastable polymorphs.
  • This approach offers potential solutions for managing drug polymorphism in pharmaceutical development and patent protection.