Liming Yao

A Cyanine-Modified Nanosystem for in Vivo Upconversion Luminescence Bioimaging of Methylmercury

Methylmercury (MeHg(+)) is a strong liposoluble ion, which can be accumulated in the organs of animals and can cause prenatal nervous system and visceral damage. Therefore, the efficient and sensitive monitoring of MeHg(+) in organisms is of great importance. Upconversion luminescence (UCL) detection based on rare-earth upconversion nanophosphors (UCNPs) as probes has been proved to exhibit a large anti-Stokes shift, no autofluorescence from biological samples, a remarkably deep penetration depth, and no photobleaching. In this study, a hydrophobic heptamethine cyanine dye (hCy7) modified by two long alkyl moieties and amphiphilic polymer (P-PEG)-modified nanophosphors (hCy7-UCNPs) was fabricated as a highly sensitive water-soluble probe for UCL monitoring and bioimaging of MeHg(+). Further application of hCy7-UCNPs for sensing MeHg(+) was confirmed by an optical titration experiment and upconversion luminescence live cell imaging. Using the ratiometric upconversion luminescence as a detection signal, which provides a built-in correction for environmental effects, the detection limit of MeHg(+) for this nanosystem was as low as 0.18 ppb. Importantly, the hCy7-UCNPs nanosystem was shown to be capable of monitoring MeHg(+)ex vivo and in vivo by upconversion luminescence bioimaging.

NIR-light-induced deformation of cross-linked liquid-crystal polymers using upconversion nanophosphors.

When upconversion nanophosphors were incorporated into an azotolane-containing cross-linked liquid-crystal polymer film, the resulting composite film generated fast bending upon exposure to continuous-wave near-IR light at 980 nm. This occurs because the upconversion luminescence of the nanophosphors leads to trans-cis photoisomerization of the azotolane units and an alignment change of the mesogens. The bent film completely reverted to the initial flat state after the light source was removed.

Yolk-shell upconversion nanocomposites for LRET sensing of cysteine/homocysteine.

The fabrication of lanthanide upconversion nanocomposites as probes has become a new research hotspot due to its special advantages via utilizing upconversion luminescence (UCL) as a detection signal. Herein, a hybrid organic dye modified upconversion nanophosphor is successfully developed as a nanoprobe for cysteine/homocysteine. Yolk-shell structured upconversion nanoparticles (YSUCNP) with lanthanide upconversion nanophosphor as moveable core and silica as mesoporous shell are synthesized, and a colorimetric chemodosimeter for cysteine/homocysteine is accommodated in the hollow cavities. Thus, cysteine/homocysteine can be quantitatively detected on the basis of luminescent resonance energy transfer (LRET) in a UCL turn-off pattern. The dye-loaded YSUCNP possess good dispersibility in aqueous solution; thus detection of the targeted molecule can be achieved in pure water. Cellular experiments carried out with laser-scanning upconversion luminescence microscopy further demonstrate that the dye-loaded YSUCNP can serve as an intracellular nanoprobe to detect cysteine/homocysteine. Moreover, this dye-loading protocol can be developed as a common approach to construct other chemodosimeter-modified UCNP hybrid nanoprobes, as proved by a UCL turn-on style sensor for cyanide.

A versatile fabrication of upconversion nanophosphors with functional-surface tunable ligands

Rare earth upconversion nanophosphors (UCNPs) have been recognized as a promising new class of biological luminescent labels for fluorescence imaging. However, little work has been reported on the successful application of UCNPs in fluorescence imaging so far. The major problem with UCNPs arises from the difficulties in obtaining water-soluble UCNPs bearing appropriate surface functional groups. To solve this problem, herein we report a general procedure for the one-pot preparation of surface-functionalized UCNPs by a modified polyol route assisted by difunctional ligands containing a carboxyl group, such as 11-aminoundecanoic acid (ADA), poly(ethylene glycol)bis(carboxymethyl)ether (PEGBA) and folic acid (FA). The success of this one-pot method was confirmed by FT-IR and 1H NMR spectroscopy. Due to the amino and carboxyl groups pointing outward, both amino-functionlized UCNPs (UCNPs-ADA) and carboxyl-functionlized UCNPs (UCNPs-PEGBA) are particularly suitable for coupling reactions with biological molecules and are potential candidates for bioimaging labels. By means of laser scanning upconversion luminescence microscopy, FA-functionlized UCNPs (UCNPs-FA) have been demonstrated to be effective in targeting folate-receptors overexpressing cancer cell lines. It is possible to design other surface-functionalized UCNPs by changing other bifunctional ligands with a carboxyl group. This strategy is general and facile for frabricating surface-functionalized UCNPs to potentially be used as bioimaging agents.

Chemodosimeter functionalized magnetic silica yolk–shell nanocomposite for sensing and removal of Hg2+

An N719 functionalized magnetic silica yolk–shell nanocomposite was synthesized, and its applications in the sensing and removal of mercury ions were evaluated by optical titration experiments and ICP. Using the ratiometric absorbance as a detection signal, the detection and removal of Hg2+ was realized in water.