A Fluorescein Derivative Chemosensor Combined with Triplet-Triplet Annihilation Upconversion System for Ratiometric Sensing of Cysteine

A derivative of fluorescein,fluorescein O,O-diacrylate(FODA),was utilized in a triplet-triplet annihilation upconversion(TTA-UC)system to develop a composite ratiometric chemosensor capable of detecting cysteine(Cys).FODA acted as both the probe for Cys and the energy acceptor for upconversion(UC)emission,thereby making UC a responsive signal to Cys.In addition,the phosphorescence signal of the sensitizer in the TTA-UC system remained constant and did not respond to Cys,making it an ideal internal reference signal for constructing a ratiometric sensor.Through this simple strategy,traditional fluorescent probes can be combined with TTA-UC system to establish a ratiometric sensing platform,which can be applied in more scenarios due to the longer wavelength excitation.

Colloidal Virus Particles with Hierarchical Nanomorphology and Facile Biosurface Modification

Aiming to the enormous requirement for the epidemic defense researches,we designed and constructed a spherical colloidal virus particle(CVP)to mimic nature virus in morphology,physical,chemical and biological characteristics,via coating spiky protein on col-loidal nanoparticles(CNPs)core with bulge hierarchical nanomorphology.The novel virus-like surface nanoparticles can easily be synthesized.The physical,chemical nature and the formation mechanism of the prepared CVPs were characterized and discussed.The synthesized CVPs are similar in size and envelope thickness to common natural viruses.It was demonstrated that the diameter of CVPs is about 238±12 nm,including an 8 nm thickness protein crown with bulges of 33 nm in average width.The CVPs with an isoelectric point of 4.5,meets the native virus property of negative charge under neutral condition.The protein crown enhances the roughness remarkably from 10 nm(CNPs)to 22 nm(CVPs)determined by atomic force microscopy.Thanks to the biomimetic rough morphology,the CVPs show greatly superior cellular uptake performance compared to CNPs,ovalbumin(OVA)and smoothed col-loidal particles(SCPs).The formation mechanism of protein crown with specific thickness can be attributed to the electrostatic in-teraction,protein's flexible structure and specific wettability.These results indicate that the as-prepared artificial virions mimic na-ture viruses in multi-dimension,in terms of size,surface rough morphology,surface negative charge and glycoprotein envelope composition.The synthetic colloidal virus particles pave a facile way toward engineering virus particles substitute for virus-related diseases prevention,diagnostics and cellular delivery vectors.