The Polymorphism of Drugs: New Approaches to the Synthesis of Nanostructured Polymorphs

Among the significant problems of modern pharmacology are the low solubility and bioavailability of drugs. One way to resolve this problem is to obtain new polymorphic forms of drugs with improved physicochemical properties. Various approaches have been developed with this aim, including the preparation of co-crystals, the use of nanoparticles, or the use of compounds in the form of a salt. A promising direction in pharmacology concerns the production of new stable polymorphic structures. In this mini-review, we consider certain aspects of drug polymorphism, methods for the synthesis of polymorphs, and the stability, size, and transformation of crystalline polymorphs. Moreover, we summarize our results from several studies demonstrating the problems associated with the synthesis of new polymorphous modifications based on inert gases and cryotemperatures. The results indicate that the problems specific to drug polymorphisms have only been partly resolved, are of current interest, and require further development.

New Paradigm of Glass Structure and Physicochemical Essence of Glass Transition

The new conception of the polymeric-polymorphoid structure of glass and glassforming liquid of individual chemical substances (ICS) is presented. The analysis of numerous data of X-ray diffractometry, DSC, Raman spectroscopy etc. shows that such glassforming ICS as SiO2, GeO2. H2O, Se, GeS2, GeSe2, As2S3, AsSe, BeCl2 and other are the copolymers of the structural fragments (polymorphoids) having no translation symmetry of two (or more) polymorphous modifications (PM) of these substances. The physicochemical essence of glass transition process is discussed.