Multihydroxy Dendritic Upconversion Nanoparticles with Enhanced Water Dispersibility and Surface Functionality for Bioimaging

Abstract

Upconversion nanoparticle (UCNP) as a new class of imaging agent is gaining prominence because of its unique optical properties. An ideal UCNP for bioimaging should simultaneously possess fine water dispersibility and favorable functional groups. In this paper, we present a simple but effective method to the synthesis of a UCNP-based nanohybrid bearing a multihydroxy hyperbranched polyglycerol (HPG) shell by the combination of a "grafting from" strategy with a ring-opening polymerization technique. The structure and morphology of the resulting UCNP-g-HPG nanohybrid were characterized in detail by Fourier transform infrared, (1)H NMR, thermogravimetric analysis, and transmission electron microscopy measurements. The results reveal that the amount of grafted HPG associated with the thickness of the HPG shell can be well tuned. UCNP-g-HPG shows high water dispersibility and strong and stable upconversion luminescence. On the basis of its numerous surface hydroxyl groups, UCNP-g-HPG can be tailored by a representative fluorescent dye rhodamine B to afford a UCNP-g-HPG-RB nanohybrid that simultaneously presents upconversion and downconversion luminescence. Preliminary biological studies demonstrate that UCNP-g-HPG shows low cytotoxicity, high luminescent contrast, and deep light penetration depth, posing promising potential for bioimaging applications.

Near-infrared light activated delivery platform for cancer therapy

“…Furthermore, a mesoporous silica coating with tunable pore size not only improves its solubility in aqueous solutions, but also it is capable of loading biomoleculars or therapeutic payload drugs due to its large surface area [110, 111]. Alternatively, other methods employing ligand oxidation reaction [112–115], ligand exchange [116, 117], and amphiphilic polymer coating [118, 119] are also attractive for improving aqueous solubility of UCNPs.…”

Improving thermal and mechanical properties of epoxy composites by using functionalized graphene

“…The compound PBI (0.1 g) was added to a suspension of sodium hydride (0.015 g) in DMF, and then stirred for 1 h at 70 o C. A total of 2 mL of anhydrous dioxane was added. Then mixture was heated to 100 o C and glycidol was added dropwise over a period of 12 h to the deprotonated compound PBI at 110 o C for another 12 h. 24 After reaction, the mixture was cooled to the room temperature and quenched by methanol. Subsequently the product was centrifuged and washed several times with methanol.…”

Rapid and highly-sensitive uric acid sensing based on enzymatic catalysis-induced upconversion inner filter effect

“…Upconversion nanoparticles can transform the long wavelength radiation to the short wavelength radiation via a two-photon or multiphoton mechanism (Deng et al, 2011;Han et al, 2014;Zhou et al, 2014aZhou et al, , 2014b. Comparing with organic fluorophores or other nano flurourence probe, UCNPs possess several outstanding features: (1) they can be excited by low power continuous wavelength lasers, which produce less damage to biological samples; (2) they offer narrow emission peaks, large Stokes shifts, low toxicity, high photostability, and thermal stability; (3) the NIR excitation source (typically 980 nm) offers greater tissue penetration depth than conventional ultraviolet excitation; (4) the NIR-excitation technique features nonblinking and non-autofluorescence, what's more, it provides an enlarged signal-to-background ratio and improved sensitivities .…”

“…Comparing with organic fluorophores or other nano flurourence probe, UCNPs possess several outstanding features: (1) they can be excited by low power continuous wavelength lasers, which produce less damage to biological samples; (2) they offer narrow emission peaks, large Stokes shifts, low toxicity, high photostability, and thermal stability; (3) the NIR excitation source (typically 980 nm) offers greater tissue penetration depth than conventional ultraviolet excitation; (4) the NIR-excitation technique features nonblinking and non-autofluorescence, what's more, it provides an enlarged signal-to-background ratio and improved sensitivities . To date, these excellent fluorescence properties make the UCNPs widely applied in biolabeling, biological imaging, and biosensing (Mader et al, 2010;Deng et al, 2011;Peng et al, 2011;Wang et al, 2011;Tang et al, 2013;Chen et al, 2014;Ma et al, 2014;Yao et al, 2014;Zhou et al, 2014aZhou et al, , 2014b, which have been regarded as decent substitutes for traditional organic fluorescent dyes in fluorimetry.…”