Stenotrophomonas maltophilia is a Gram-negative bacterial pathogen of increasing concern to human health. Most clinical isolates of S. maltophilia efficiently form biofilms on biotic and abiotic surfaces, making this bacterium resistant to a number of antibiotic treatments and therefore difficult to eliminate. To date, very few studies have investigated the molecular and regulatory mechanisms responsible for S. maltophilia biofilm formation. Here we constructed a random transposon insertion mutant library of S. maltophilia ATCC 13637 and screened 14,028 clones. A total of 46 nonredundant genes were identified. Mutants of these genes exhibited marked changes in biofilm formation, suggesting that multiple physiological pathways, including extracellular polysaccharide production, purine synthesis, transportation, and peptide and lipid synthesis, are involved in bacterial cell aggregation. Of these genes, 20 putatively contributed to flagellar biosynthesis, indicating a critical role for cell motility in S. maltophilia biofilm formation. Genetic and biochemical evidence demonstrated that an orphan response regulator, FsnR, activated transcription of at least two flagellum-associated operons by directly binding to their promoters. This regulatory protein plays a fundamental role in controlling flagellar assembly, cell motility, and biofilm formation. These results provide a genetic basis to systematically study biofilm formation of S. maltophilia .

Progesterone injection is oily because of its poor solubility. It is necessary to develop new dosage forms or delivery methods for Progesterone. Six cocrystals of Progesterone with nitrogen heterocyclic compounds (2,6-diaminopyridine, isonicotinamide, 4-aminopyridine, aminopyrazine, picolinamide and pyrazinamide) have been designed and prepared by ethyl acetate-assisted grinding, of which four cocrystals (2,6-diaminopyridine, isonicotinamide, 4-aminopyridine and aminopyrazine) had single crystal data in 1:1 stoichiometry. Metadynamics-genetic crossing was used to search and optimize various cluster structures to explain the reason the other two cocrystals could not be obtained with suitable size for single crystal X-ray diffraction. In contrast to the carboxyl group, the amide group and amino group were good substituents in the pyridine/pyrazine ring for cocrystallization with Progesterone, which meant inductive effect played an important role in nitrogen heterocyclic compounds containing reactive hydrogen. All cocrystals were more soluble than Progesterone in water, and Progesterone–pyrazinamide cocystal featured the best water solubility performance with an approximately six-fold increase over free Progesterone. This successful attempt provides an effective route for designing and manufacturing novel solid states of Progesterone.

Aminoglutethimide (AG), a Biopharmaceutical Classification System II (BCSII) drug, is approved for treating certain patients with Cushing's syndrome and breast cancer. However, it is technically limited to clinical application due to poor aqueous solubility. The water solubility of AG can be enhanced through the utilization of the co-crystal method. To screen AG co-crystals, this work employed liquid-assisted grinding and slow solvent evaporation methods. Three novel co-crystals of AG were successfully synthesized based on NH₂–COOH supramolecular synthon theory. All co-crystals exhibited higher apparent solubility than pure AG in the dissolution experiments. The intermolecular interactions of the co-crystals were examined using single crystal X-ray diffraction along with other analytical methods to determine their crystal structures. The formation of co-crystals was dominated by N–H⋯O hydrogen bonds in molecular electrostatic potential (MEP) analysis. To further explore and visualize the intermolecular interactions that form co-crystals, Hirshfeld surface (HS) analyses and independent gradient model based on Hirshfeld partition (IGMH) analysis were applied. It was found that the van der Waals (vdW) force is another main driving force, working in conjunction with hydrogen bonds to form basic units of AG co-crystals. In addition, toxicity tests on liver and kidney organoids showed that three new co-crystals did not cause more serious toxicity than pure AG. Overall, this work has provided the structural analysis of three newly formed AG co-crystals, offering an insight into intermolecular interactions of co-crystals at the molecular level.