Synthesis of N-Difluoromethyl Carbonyl Compounds from N-Difluoromethylcarbamoyl Fluorides.

Fluorinated small molecules are commonly used in functional small-molecule chemistry, and N-difluoromethyl (N-CF2H) compounds are particularly intriguing due to their unique and unexplored physiochemical properties. However, despite limited progress, a general methodological approach to the synthesis of N-CF2H compounds remains elusive. Here, guided by computation, we present a simple and practical protocol to access N-CF2H amides and related carbonyl derivatives. The protocol involves a one-pot conversion of thioformamides through desulfurization-fluorination and acylation, providing N-difluoromethylcarbamoyl fluoride building blocks that can be further diversified to a variety of unexplored N-CF2H carbonyl compounds with rich functionality. Additionally, preliminary studies on their properties and stability showcased their potential application in pharmaceuticals and agrochemicals.

Identification and investigation of the vibrational properties of crystalline and co-amorphous drugs with Raman and terahertz spectroscopy.

Co-amorphous drugs have shown significant potential in improving the stability and bioavailability compared with single neat amorphous drugs. Here, we explored the molecular interactions of cimetidine, naproxen, indomethacin and their binary co-amorphous mixtures via Raman and terahertz (THz) spectroscopy. We used quench-cooled method to prepare the neat amorphous drugs and their binary co-amorphous mixtures and tested their thermodynamic properties through differential scanning calorimetry (DSC). Then, we found that the stability of co-amorphous drugs was stronger than their neat amorphous components. Furthermore, Raman spectroscopy was used to characterize the vibrational modes between different co-amorphous drugs. Generally, we found that the stability of co-amorphous drugs was better than their neat amorphous components for these samples we tested. Meanwhile, we complemented the detection of THz spectroscopy and found that crystalline and amorphous drugs could be better distinguished.

Label-free self-referenced sensing of living cells by terahertz metamaterial-based reflection spectroscopy.

Terahertz (THz) metamaterial-based reflection spectroscopy is proposed for label-free sensing of living cells by a self-referenced method. When sensing the living Madin-Darby canine kidney cell monolayer and phosphate buffered saline solution, self-referenced signals showed significant differences in peak intensity because of inherent discrepancy in the imaginary part of their complex refractive indices, as confirmed by 3D-FDTD simulations. The resonance peak intensity was unaffected by cell monolayer thickness variation, demonstrating feasibility for sensing various cells. Simulations and experiments showed that saponin-induced changes in cell permeability could be monitored in real-time. The self-referenced signal was linearly dependent on the adherent cell density, illustrating a label-free in situ THz metamaterial-based cell sensor.

Rapid screening of colistin-resistant Escherichia coli, Acinetobacter baumannii and Pseudomonas aeruginosa by the use of Raman spectroscopy and hierarchical cluster analysis.

Colistin is recognized as the last therapeutic option for multidrug-resistant Gram-negative bacteria infection. In addition, bacterial resistance to colistin could be transmitted between different species through plasmid-mediated mcr-1 gene transfer. Therefore, rapid screening of colistin-resistant isolates will play a key role in controlling the spread of resistance and improving patient outcomes. We developed a rapid method for the detection of colistin-resistance in Escherichia coli, Acinetobacter baumannii, and Pseudomonas aeruginosa bacteria based on Raman spectroscopy and hierarchical cluster analysis. Bacteria were incubated with and without colistin using CAMHB as the liquid culture medium. They were then centrifuged and dried on a glass slide. Five Raman spectra of each of the samples were recorded and analyzed by the hierarchical cluster analysis method to determine whether the bacteria were resistant. To evaluate this method, 123 clinical bacterial isolates (42 isolates of E. coli, 41 isolates of A. baumannii and 40 isolates of P. aeruginosa) were tested. The detection sensitivity and specificity were 90.9% and 91.1%, respectively, compared with the reference broth microdilution method. The screening is easy to perform and can be completed in 1.5 h, suggesting that it holds great potential to be an initial screening method in countries and areas where colistin becomes the last resort antibiotic.

Terahertz spectroscopy for the isothermal detection of bacterial DNA by magnetic bead-based rolling circle amplification.

The demand for rapid and sensitive bacterial detection is continuously increasing due to the significant requirements of various applications. In this study, a terahertz (THz) biosensor based on rolling circle amplification (RCA) was developed for the isothermal detection of bacterial DNA. The synthetic bacterium-specific sequence of 16S rDNA hybridized with a padlock probe (PLP) that contains a sequence fully complementary to the target sequence at the 5' and 3' ends. The linear PLP was circularized by ligation to form a circular PLP upon recognition of the target sequence; then the capture probe (CP) immobilized on magnetic beads (MBs) acted as a primer to initialize RCA. As DNA molecules are much less absorptive than water molecules in the THz range, the RCA products on the surface of the MBs cause a significant decrease in THz absorption, which can be sensitively probed by THz spectroscopy. Our results showed that 0.12 fmol of synthetic bacterial DNA and 0.05 ng µL-1 of genomic DNA could be effectively detected using this assay. In addition, the specificity of this strategy was demonstrated by its low signal response to interfering bacteria. The proposed strategy not only represents a new method for the isothermal detection of the target bacterial DNA but also provides a general methodology for sensitive and specific DNA biosensing using THz spectroscopy.