TfOH-Catalyzed Phosphinylation of 2,3-Allenols into γ-Ketophosphine Oxides.

The first facile and efficient acid-catalyzed direct coupling of a wide range of unprotected 2,3-allenols with arylphosphine oxides was developed, offering a general, one-step approach for the synthesis of structurally diverse γ-ketophosphine oxides accompanied by concurrent C-P/C═O bond formation with remarkable functional group tolerance and complete atom-economy under metal- and additive-free conditions. Mechanistic studies showed that this transformation involved a rearrangement and a phospha-Michael reaction.

A sensitive and rapid detection of glutathione based on a fluorescence-enhanced "turn-on" strategy.

Glutathione (GSH) plays important roles in the human body including protecting cells from oxidative damages and maintaining cellular redox homeostasis. Thus, developing a fast and sensitive method for detecting GSH levels in living bodies is of great importance. Many methods have been developed and used for GSH detection, such as high-performance liquid chromatography, capillary electrophoresis, and fluorescence resonance energy-based methods. However, these methods often lack sensitivity as well as efficiency. Herein, a rapid and sensitive method for glutathione detection was developed based on a fluorescence-enhanced "turn-on" strategy. In this study, a unique and versatile bifunctional linker 3-[(2-aminoethyl) dithio]propionic acid (AEDP)-modified gold nanoparticle (Au@PLL-AEDP-FITC) probe was designed for the simple, highly sensitive intracellular GSH detection, combined with the FRET technique. In the presence of GSH, the disulfide bonds of AEDP on Au@PLL-AEDP-FITC were broken through competition with GSH, and FITC was separated from gold nanoparticles, making the fluorescence signal switch to the "turn on" state. A change in the fluorescence signal intensity has a great linear positive correlation with GSH concentration, in the linear range from 10 nM to 180 nM (R2 = 0.9948), and the limit of detection (LOD) of 3.07 nM, which was lower than other reported optical nanosensor-based methods. Au@PLL-AEDP-FITC also has great selectivity for GSH, making it promising for application in complex biological systems. The Au@PLL-AEDP-FITC probe was also successfully applied in intracellular GSH imaging in HeLa cells with confocal microscopy. In short, the Au@PLL-AEDP-FITC probe-based fluorescence-enhanced "turn-on" strategy is a sensitive, fast, and effective method for GSH detection as compared with other methods. It can be applied in complex biological systems such as cell systems, with promising biological-medical applications in the future.

Nondestructive capture, release, and detection of circulating tumor cells with cystamine-mediated folic acid decorated magnetic nanospheres.

Circulating tumor cell (CTC) detection and enumeration have been considered as a noninvasive biopsy method for the diagnosis, characterization, and monitoring of various types of cancers. However, CTCs are exceptionally rare, which makes CTC detection technologically challenging. In the past few decades, much effort has been focused on highly efficient CTC capture, while the activity of CTCs has often been ignored. Here, we develop an effective method for nondestructive CTC capture, release, and detection. Folic acid (FA), as a targeting molecule, is conjugated on magnetic nanospheres through a cleavable disulfide bond-containing linker (cystamine) and a polyethylene glycol (PEG2k) linker, forming MN@Cys@PEG2k-FA nanoprobes, which can bind with folate receptor (FR) positive CTCs specifically and efficiently, leading to the capture of CTCs with an external magnetic field. When approximately 150 and 10 model CTCs were spiked in 1 mL of lysis blood, 93.1 ± 2.9% and 80.0 ± 9.7% CTCs were recovered, respectively. In total, 81.3 ± 2.6% captured CTCs can be released from MN@Cys@PEG2k-FA magnetic nanospheres by treatment with dithiothreitol. The released CTCs are easily identified from blood cells for specific detection and enumeration combined with immunofluorescence staining with a limit of detection of 10 CTC mL-1 lysed blood. Moreover, the released cells remain healthy with high viability (98.6 ± 0.78%) and can be cultured in vitro without detectable changes in morphology or behavior compared with healthy untreated cells. The high viability of the released CTCs may provide the possibility for downstream proteomics research of CTCs; therefore, cultured CTCs were collected for proteomics. As a result, 3504 proteins were identified. In conclusion, the MN@Cys@PEG2k-FA magnetic nanospheres prepared in this study may be a promising tool for early-stage cancer diagnosis and provide the possibility for downstream analysis of CTCs.