In Situ Probing the Short-Lived Intermediates in Visible-Light Heterogeneous Photocatalysis by Mass Spectrometry.

Visible-light-mediated heterogeneous photocatalysis has recently emerged as an environmentally friendly and energy-sustainable alternative for organic transformations. Despite the advancements in developing wide varieties of photocatalysts during the past decades, the accurate probing and identification of the photogenerated species, especially the short-lived radical intermediates, are still challenging. In this work, we reported a hybrid ion emitter that integrated with a pico-liter heterogeneous photocatalytic reactor, which was fabricated by depositing the photocatalyst (e.g., TiO2) into the front tip of a quartz micropipette. Benefited from the dual-function feature of the hybrid micropipette (i.e., a clog-free tip-confined pico-liter reactor for heterogeneous photocatalysis and an ion emitter for nanoelectrospray ionization), sensitized photoredox reactions at the catalyst-solution interface can be triggered upon visible-light irradiation using a cheap LED laser (453 nm), and the newly produced transient radical intermediates can be rapidly transformed into gaseous ions for mass spectrometric identification. Using this novel low-delay coupling device, photogenerated intermediates, including the cationic radicals produced during the photooxidation of anilines and the anionic radicals produced during the photoreduction of quinones, were successfully captured by mass spectrometry. We believe that our hybrid photochemical microreactor/ion emitter has provided a new and powerful tool for exploring the complicated heterogeneous photochemical processes, especially their ultrafast initial transformations.

Microfluidic Gradient Culture Arrays for Cell Pro-oxidation Analysis Using Bipolar Electrochemiluminescence.

A microfluidic gradient array is a widely used screening and analysis device, which has characteristics of high efficiency, high automation, and low consumption. Bipolar electrode electrochemiluminescence (BPE-ECL) has special value in microfluidic array chips. The combination of the microfluidic gradient and BPE arrays has potential for high-throughput screening. In this article, a microfluidic BPE array chip for gradient culture and conditional screening of cancer cells was designed. The generation of concentration gradients, continuous culture of cancer cells with high throughput, and drug screening through BPE-ECL of the Ru(bpy)32+/TPrA system can be performed in one chip. We tested gradient pro-oxidation of MCF-7 by ascorbic acid and the synergistic effect of pro-oxidation on doxorubicin. The method achieves high analysis efficiency through a BPE array while simplifying the tedious procedures required by cell culture methods.