Sulfone/Carbonyl-Based Donor-Acceptor Fluorescent Dyes: Synthesis, Structures, Photophysical Properties and Cell Imaging.

Electron-accepting units play vital roles in constructing donor-acceptor (D-A) conjugated organic optoelectronic materials; the electronic structures and functions of the acceptors need to be carefully unveiled to controllably tailor the optoelectronic properties. We have synthesized two D-A conjugated organic fluorophores, TPA-SO and TPA-CO, with similar molecular skeletons based on sulfone- or carbonyl-containing polycyclic aromatic acceptors. Both TPA-SO and TPA-CO display obvious solvent polarity-dependent photophysical properties and large Stokes shift of over 100 nm for strong intramolecular charge transfer processes. Experimental evidence indicates that the sulfone group in TPA-SO merely serves as a strong electron-withdrawing unit. TPA-SO shows yellowish-green emission with a peak at 542 nm and an absolute photoluminescence quantum yield (PLQY) of 98 % in solution, whereas the carbonyl group in TPA-CO can act as both an electron-withdrawing unit and spin transition convertor, so TPA-CO displays red emission with a low absolute PLQY of 0.32 % in solution. Impressively, upon going from solution to aggregate state, TPA-SO nanoparticles keep a high PLQY of 9.5 % and moderate biocompatibility, thus they are good nano-agents for cellular fluorescence imaging. The results reveal that the inherent acceptor characteristic acts as a crucial effect in the photophysical properties and applications of the organic fluorophores.

Ratiometric fluorescence detection of superoxide anion based on AuNPs-BSA@Tb/GMP nanoscale coordination polymers.

A novel ratiometric fluorescence nanosensor for superoxide anion (O2•- ) detection was designed with gold nanoparticles-bovine serum albumin (AuNPs-BSA)@terbium/guanosine monophosphate disodium (Tb/GMP) nanoscale coordination polymers (NCPs) (AuNPs-BSA@Tb/GMP NCPs). The abundant hydroxyl and amino groups of AuNPs-BSA acted as binding points for the self-assembly of Tb3+ and GMP to form core-shell AuNPs-BSA@Tb/GMP NCP nanosensors. The obtained probe exhibited the characteristic fluorescence emission of both AuNPs-BSA and Tb/GMP NCPs. The AuNPs-BSA not only acted as a template to accelerate the growth of Tb/GMP NCPs, but also could be used as the reference fluorescence for the detection of O2•- . The resulting AuNPs-BSA@Tb/GMP NCP ratiometric fluorescence nanosensor for the detection of O2•- demonstrated high sensitivity and selectivity with a wide linear response range (14 nM-10 µM) and a low detection limit (4.7 nM).

BSA-AuNPs@Tb-AMP metal-organic frameworks for ratiometric fluorescence detection of DPA and Hg2.

An easy and effective strategy for synthesizing a ratiometric fluorescent nanosensor has been demonstrated in this work. Novel fluorescent BSA-AuNPs@Tb-AMP (BSA, bovine serum albumin; AMP, adenosine 5'-monophosphate; AuNPs, Au nanoparticles) metal-organic framework (MOF) nanostructures were synthesized by encapsulating BSA-AuNPs into Tb-AMP MOFs for the detection of 2,6-pyridinedicarboxylic acid (DPA) and Hg2+ . DPA could strongly co-ordinate with Tb3+ to replace water molecules from the Tb3+ center and accordingly enhanced the fluorescence of Tb-AMP MOFs. The fluorescence of BSA-AuNPs at 405 nm remained constant. While the fluorescence of BSA-AuNPs at 635 nm was quenched after Hg2+ was added, the fluorescence of Tb-AMP MOFs remained constant. Accordingly, a ratiometric fluorescence nanosensor was constructed for detection of DPA and Hg2+ . The ratiometric nanosensor exhibited good selectivity to DPA over other substances. The F545 /F405 linearly increased with increase of DPA concentration in the range of 50 nM to 10 µM with a detection limit as low as 17.4 nM. F635 /F405 increased linearly with increase of Hg2+ concentration ranging from 50 nM to 1 µM with a detection limit as low as 20.9 nM. Additionally, the nanosensor could be successfully applied for the determination of DPA and Hg2+ in running water.

"On-off" ratiometric fluorescent detection of Hg2+ based on N-doped carbon dots-rhodamine B@TAPT-DHTA-COF.

Covalent-organic frameworks (COFs) are new porous crystalline materials owning outstanding stability, adsorbability and hypotoxicity. The assembly of fluorescence probes into porous COF provides a good method for ratiometric fluorescence detection avoiding the toxic effects of fluorescence probes to the samples. Herein, a two-dimensional COF (TAPT-DHTA-COF) was employed as a host to encapsulate N-doped carbon dots (NCDs) and Rhodamine B (RhB) (NCDs-RhB@COF). NCDs and RhB were uniformly assembled into the pores of TAPT-DHTA- COF based on the hydrogen bond. The as-prepared NCDs-RhB@COF nanocomposites exhibited blue emission of NCDs at 440 nm and red emission of RhB at 570 nm at excitation of 340 nm. After the addition of Hg2+, the blue emission became weaker while the red emission was enhanced due to the strong coordination between NCDs-RhB@COF and Hg2+. This "on-off" fluorescence probe was applied in detection of trace Hg2+ with linear range of 0.048-10 µM and detection limit of 15.9 nM together with appropriate selectivity, acceptable sensitivity and stability. The work shreds some light for COF as platform to construct ratiometric fluorescent sensor for industrial and biological application.

Ratiometric fluorescence detection of O2•- based on dual-emission schiff base polymer/rhodamine-B nanocomposites.

A novel ratiometric fluorescent sensor for superoxide radical (O2•-) detection was developed based on Schiff base polymer (SBP)/rhodamine-B (SBP/RDB) nanocomposites. The SBP/RDB was investigated by atomic force microscopy, scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy, N2 adsorption/desorption isotherms and fluorescence spectroscopy, etc. The results showed the SBP was two-dimensional (2D) crystalline nanosheet with the thickness of 0.5 nm. RDB could be self-assembled on each of 2D SBP surface to form SBP/RDB due to the hydrogen bond between N atoms of SBP and -COOH of RDB as well as π-π interaction. The SBP/RDB exhibited the characteristic fluorescence emission of both SBP at 485 nm and RDB at 585 nm under an excitation of 270 nm. The 2D SBP was not only acted as template to assemble RDB, but also used as reference fluorescence for O2•- detection. The SBP/RDB fluorescence probe for O2•- detection demonstrated high sensitivity and selectivity with good linear range (11.1 ±â€¯0.76 nM-8.0 ±â€¯0.36 µM) and low detection limit (3.7 ±â€¯0.42 nM). Because of the low cost and simple operation, the work sheds some new light to construct ratiometric fluorescent sensors based on SBP to detect O2•- in drinking water and human blood serum for commercial applications.

Trimester-specific reference ranges for thyroid hormones in pregnant women.

The aim of this study was to determine the trimester-specific reference range of thyroid function in Nanjing.A total of 805 pregnant women in the 1st, 2nd, and 3rd trimesters were recruited in the prospective, observational study during their routine antenatal clinic visit and 282 nonpregnant subjects served as controls. A questionnaire was completed by the subjects to record their personal health history, family history of thyroid disease, and consumption of estrogen or antithyroid drugs. Thyroid palpation was performed to exclude the thyroid goiter. Thyroid function and urine iodine were measured by chemiluminescence and arsenic cerium analysis.The trimester-specific reference ranges in Nanjing were as follows: thyroid-stimulating hormone (TSH) 0.02 to 3.78 mIU/L, free thyroxine (FT4) 13.93 to 26.49 pmol/L, total thyroxine (TT4) 103.39 to 319.43 nmol/L in the 1st trimester. TSH 0.47 to 3.89 mIU/L, FT4 12.33 to 19.33 pmol/L, TT4 92.28 to 234.88 nmol/L in the 2nd trimester. TSH 0.55 to 4.91 mIU/L, FT4 11.38 to 19.21 pmol/L, TT4 83.54 to 258.12 nmol/L in the 3rd trimester. According to the TSH reference range recommended by American Thyroid Association (ATA), the prevalence of subclinical hypothyroidism, subclinical hyperthyroidism, hyperthyroidism, hypothyroxinemia, and thyroid peroxidase antibody-positive were 12.42%, 0.50%, 0.99%, 1.61%, and 11.80%, respectively, prevalence according to the trimester-specific reference range were 1.99%, 0.25%, 1.61%, 0.37%, and 1.61%, respectively, which showed elevated hypothyroxinemia incidence and declined incidence of subclinical hypothyroidism and hyperthyroidism.Trimester-specific reference range varied from that of ATA's recommendation, influencing the diagnosis, and treatment of pregnant thyroid disorders. To detect and control these disorders properly, setting up trimester-specific reference is clinically essential.