New photoinitiating systems based on a polyoxometalate (POM) are proposed: phosphomolybdic acid in combination with silane, germane, or iodonium salt can be used to generate silyl, germyl, or phenyl radicals as well as silylium cations. The photochemical mechanisms are studied by steady‐state photolysis and electron spin resonance. The phosphomolybdic acid/silane/iodonium salt system can initiate either the radical photopolymerization of acrylates or the cationic photopolymerization of epoxides. The synthesis of interpenetrated polymer networks can also be carried out. The mechanical properties of the synthesized polymers are affected by the presence of POM in the matrix, as shown by their dynamic mechanical analysis (DMA).
The cooperative entrapment of a specified guest is only available for a well‐defined host. Here it is reported that a common host conducts cooperative entrapment of guests. Alkylation of a hyperbranched polyethylenimine (PEI) by epoxy poly(ethylene glycol) monomethyl ethers (PEG1) leads to a water‐soluble PEI@PEG1 ( H1 ). The multifunctional core of H1 is modified to result in H2 – H4, with different polarities and ionic charges. H1 – H4 exist as unimolecular micelles, and can effectively entrap dyes of rose bengal (RB) or eosin Y (EY). Experiments indicate that the guest dyes are exclusively accommodated in the cores of H1 – H4 . The encapsulation proceeds in a cooperative manner, as analysis by the Hill equation (n > 1). It is found that the cooperativity stems from the enhanced π–π stacking of the dyes upon encapsulation, and a polar and ionic environment favors the cooperativity. This is the first example of a cooperative entrapment being realized by a common host.
Encapsulation of single cells is a challenging task in droplet microfluidics due to the random compartmentalization of cells dictated by Poisson statistics. In this paper, a microfluidic device was developed to improve the single-cell encapsulation rate by integrating droplet generation with fluorescence-activated droplet sorting. After cells were loaded into aqueous droplets by hydrodynamic focusing, an on-flight fluorescence-activated sorting process was conducted to isolate droplets containing one cell. Encapsulation of fluorescent polystyrene beads was investigated to evaluate the developed method. A single-bead encapsulation rate of more than 98 % was achieved under the optimized conditions. Application to encapsulate single HeLa cells was further demonstrated with a single-cell encapsulation rate of 94.1 %, which is about 200 % higher than those obtained by random compartmentalization. We expect this new method to provide a useful platform for encapsulating single cells, facilitating the development of high-throughput cell-based assays. 相似文献
