Circular dichroism in functional quality evaluation of medicines.

Circular dichroism (CD) is a non-destructive and powerful technique for providing structure and ligand interaction information of small molecules as well as biotechnological medicines. While CD is a well-established technique in biomedical research, and different types and variants of CD do exist, the focus of this review is on the pharmaceutical quality control (QC) aspects of the classic electronic CD (ECD). The basic principles of the CD technique are initially described, followed by a systematic literature research on pharmaceutical aspects encompassing chiral small molecules, bio-polymers (i.e. proteins, peptides and nucleic acids), medicine-biotarget interaction (i.e. small molecule-albumin interaction, protein-receptor interaction and peptide-biotarget interaction) and medicine changes (i.e. chemical modification, biosimilar/bio-better with stability and aggregation). In addition, unstructured literature was also included covering the use of CD mainly in discovery and fundamental research, but which might shift towards the pharmaceutical QC field as well in the future.