Mass-spectrometry-based assays nowadays play an essential role in biomedical research and clinical applications. There are different types of commercial mass spectrometers on the market today, and triple quadrupole (QqQ) is one of the time-honored systems. Here, we overview the main areas of QqQ applications in biomedicine and assess the current level, evolution, and trends in the use of QqQ in these areas. Relevant data were extracted from the Scopus database using the specified terms and Boolean operators defined for each field of the QqQ application. We also discuss the recent advances in QqQ and QqQ-based analytical platforms, which promote the clinical application of these systems, and explain the indicated substantial increase in triple quadrupole use in biomedicine. The number of biomedical studies utilizing QqQ increased 2–3 times this decade. Triple quadrupole is most intensively used in the field of endocrine research and testing. On the contrary, the relative rate of immunoassay utilization—a major competitor of chromatography–mass spectrometry—decreased in this area as well as its use within Therapeutic drug monitoring (TDM) and forensic toxicology. Nowadays, the applications of high-resolution accurate mass (HRAM) mass spectrometers in the investigated areas represent only a small fraction of the total amount of research using mass spectrometry; however, their application substantially increased during the last decade in the untargeted search for new biomarkers.

Synthesis of steroid drugs is possible through biotechnological methods, however, the low efficiency of transporting steroid substrates across microbial membranes is the challenge in using microorganisms for their production. STARD1 and STARD3 proteins (members of the START domain family) work in some mammalian cells in conjunction with the steroidogenic P450scc enzyme system (cytochrome P450scc, adrenodoxin reductase, and adrenodoxin), transporting cholesterol to the mitochondria, where cytochrome P450scc converts it into pregnenolone. In this study, we investigated the effect of STARD1 and STARD3 on P450scc efficiency in E. coli expression models. The combination of the STARD3(216–444) or STARD1(53–285) protein bearing an N-terminal periplasm-targeting sequence, with the P450scc system reconstituted in E. coli, resulted in an increase of pregnenolone synthesis by 3.2- and 1.9-fold, respectively, on a laboratory scale. STARD3(216–444) showed higher levels of expression and a greater effect on the incorporation of sterols into cells and whole-cell biotransformation of cholesterol, compared to STARD1(53–285). This study proposes a fundamentally new approach to optimizing the functioning of the P450scc system in microbial cells, which uses the cholesterol transfer protein to increase the uptake efficiency of a poorly soluble steroid substrate by bacteria. The demand for steroid medications is increasing, and the use of specific carrier proteins could be a useful tool to enhance the efficiency of whole-cell biosynthesis of various steroid compounds.