Tianrong Li

Crystal structures, DNA-binding and cytotoxic activities studies of Cu(II) complexes with 2-oxo-quinoline-3-carbaldehyde Schiff-bases

Three novel 2-oxo-quinoline-3-carbaldehyde Schiff-bases and their Cu(II) complexes were synthesized. The molecular structures of Cu(II) complexes were determined by X-ray crystal diffraction. The DNA-binding modes of the complexes were also investigated by UV-vis absorption spectrum, fluorescence spectrum, viscosity measurement and EB-DNA displacement experiment. The experimental evidences indicated that the ligands and Cu(II) complexes could interact with CT-DNA (calf-thymus DNA) through intercalation, respectively. Comparative cytotoxic activities of ligands and Cu(II) complexes were also determined by MTT [3-(4,5-dimethyl-2-thiazoyl)-2,5-diphenyl-2H-tetrazolium bromide] and SRB (sulforhodamine B) methods. The results showed that the three Cu(II) complexes exhibited more effective cytotoxic activity against HL60 cells and HeLa cells than corresponding ligands. Also, CuL(3) showed higher cytotoxic activity than CuL(1) and CuL(2).

An effective Cu(II) quenching fluorescence sensor in aqueous solution and 1D chain coordination polymer framework

In the article, a novel fluorescent probe for the copper cation based on fluorescence quenching mechanism was designed. It exhibited high selectivity for Cu(II) over other common metal ions in aqueous media. Furthermore the coordination between Cu(II) and the organic molecule sensor fabricated an interesting 1D chain coordination polymer framework.

Coupling of Luminescent Terbium Complexes to Fe3O4 Nanoparticles for Imaging Applications

Coupling optically active components to magnetic nanoparticles (NPs) is an attractive way to develop multifunctional probes for highly sensitive biological imaging and recognition. While iron oxide NPs have been explored as robust magnetic contrast and therapeutic agents, semiconducting quantum dots, fluorescent organic dyes, and metal complexes are now commonly sought after for sensitive optical imaging applications. Among all molecular optical probes studied thus far, lanthanide-based complexes have attracted particular interest due to their unique long luminescence lifetimes (microto milliseconds), sharp emission bands, and insensitivity to photobleaching. Despite numerous efforts researching magnetic NPs and lanthanide-based complexes for biomedical applications, conjugates containing both magnetic NPs and lanthanide complexes have not been synthesized and studied. Such conjugates with both magnetic and optical imaging capabilities should serve as new bifunctional probes for highly sensitive biorecognition applications. We have now designed and prepared a luminescent lanthanide nanoparticle label based on sensitization of an organic chromophore. The particle is made up of Fe3O4 NPs coated with a lanthanide complex (Scheme 1). Ligand 1b is comprised of a quinolone-based dye acting as light-absorption antenna and a polyethylene glycol 3,4-dihydroxybenzylamine (DBI-PEG-NH2) moiety, which enables binding to the surface of Fe3O4 NPs to give water-soluble NPs. These Fe3O4 NPs are strongly luminescent in aqueous solution and have a long fluorescence lifetime. Folic acid (FA) is a high-affinity ligand for folate receptor (FR), and has been widely used for targeted delivery of FAconjugated molecular probes or nanoparticles to FR-overexpressing cancer cell lines (e.g., HeLa and KB cell lines). Since salicylic acid has excellent coordination ability with rare-earth metal ions and can sensitize their luminescence, we used folate-(salicylic acidyl)-amine as cell-targeting agent for further application in bioimaging based on Tb:1b. Synthesis of the luminescent Fe3O4 NPs is presented in Scheme S1 (Supporting Information). The PEG amine 1a was prepared from 1,w-diaminopolyoxyethylene (M = 4000) and 3,4-dihydroxybenzaldehyde. 7-Amino-4-methyl-2(1H)-quinolinone (cs124) was covalently coupled with diethylenetriaminepentaacetic acid (DTPA) by means of its dianhydride, and the product was then treated with 1a to obtain 1b. Complex Tb:1b was formed by stirring 1b with TbCl3 overnight in DMF, and then treated with folate-(salicylic acidyl)-amine in DMF to give Tb:1b-FA. Monodisperse Fe3O4 NPs coated with oleylamine with a size of 12 nm were synthesized by a previously published procedure. Exchange of oleic acid and oleylamine on the surface of Fe3O4 NPs with Tb:1b or Tb:1b-FA was easily achieved by mixing Tb:1b or Tb:1b-FA and Fe3O4 NPs monodispersed in water (Figure S1, Supporting Information); the NPs showed little change in core size after surface modification. According to the Tb/Fe weight percentage (105%), about 2312 Tb units are bound to each Fe3O4 NP, corresponding to about 2312 ligands per Fe3O4 NP. Magnetization of as-synthesized Fe3O4 NPs and Tb:1 bFA-NPs was measured as a function of applied magnetic field (Figure S2, Supporting Information). Little change in magnetic properties was observed between the as-synthesized Fe3O4 NPs and Tb:1b-FA-NPs. None of the samples showed hysteresis, that is, the nanoparticles retain superparamagetism. The saturated magnetization (Ms) of as-synthesized Fe3O4 NPs and Tb:1b-NPs are 54.8 and 17.8 Am 2 kg , respectively. The dispersibility of Tb:1b-FA-NPs was tested by measuring the change of their hydrodynamic size during incubation under different conditions. Figure S3 (Supporting Information) shows that Tb:1b-FA-NPs are stable to dispersion in phosphate buffered saline (PBS) and show no change in the statistical hydrodynamic size over the incubation time, and little change in the size of Tb:1b-FA-NPs occurs with varying temperature. The measured size increase from about 129 to about 219 nm in the presence of fetal bovine serum (FBS) is attributed to adsorption of FBS onto the NP surface, as reported previously. On the other hand, at lower pH 6 (Figure S4, Supporting Information), the particles can be stabilized for only 2 h before serious aggregation occurs. After 8 h, the size of the clustered nanoparticles reaches 190 nm, due to chemical bond cleavage between iron oxide and the catechol unit of 3,4-dihydroxybenzaldehyde under low-pH incubation conditions, which destabilizes the nanoparticle dispersion. [*] B. Wang Key Laboratory of Nonferrous Metal Chemistry and Resources Utilization of Gansu Province and State Key Laboratory of Applied Organic Chemistry, Lanzhou University (P.R. China)

Self‐Assembled Fluorodendrimers Combine the Features of Lipid and Polymeric Vectors in Gene Delivery

An ideal vector in gene therapy should exhibit high serum stability, excellent biocompatibility, a desired transfection efficacy and permeability into targeted tissues. Here, we describe a class of low-molecular-weight fluorodendrimers for efficient gene delivery. These materials self-assemble into uniform nanospheres and allow for efficient transfection at low charge ratios and very low DNA doses with minimal cytotoxicity. Our results demonstrate that these vectors combine the features of synthetic gene vectors such as liposomes and cationic polymers and present promising potential for clinical gene therapy.

Palladium nanoparticles bonded to two-dimensional iron oxide graphene nanosheets: a synergistic and highly reusable catalyst for the Tsuji-Trost reaction in water and air.

Low cost, high activity and selectivity, convenient separation, and increased reusability are the main requirements for noble-metal-nanocatalyst-catalyzed reactions. Despite tremendous efforts, developing noble-metal nanocatalysts to meet the above requirements remains a significant challenge. Here we present a general strategy for the preparation of strongly coupled Fe(3)O(4) and palladium nanoparticles (PdNPs) to graphene sheets by employing polyethyleneimine as the coupling linker. Transmission electron microscopic images show that Pd and Fe(3)O(4) nanoparticles are highly dispersed on the graphene surface, and the mean particle size of Pd is around 3 nm. This nanocatalyst exhibits synergistic catalysis by Pd nanoparticles supported on reduced graphene oxide (rGO) and a tertiary amine of polyethyleneimine (Pd/Fe(3)O(4)/PEI/rGO) for the Tsuji-Trost reaction in water and air. For example, the reaction of ethyl acetoacetate with allyl ethyl carbonate afforded the allylated product in more than 99 % isolated yield, and the turnover frequency reached 2200 h(-1). The yield of allylated products was 66 % for Pd/rGO without polyethyleneimine. The catalyst could be readily recycled by a magnet and reused more than 30 times without appreciable loss of activity. In addition, only about 7.5 % of Pd species leached off after 20 cycles, thus rendering this catalyst safer for the environment.

A multifunctional nanoprobe based on Au–Fe3O4 nanoparticles for multimodal and ultrasensitive detection of cancer cells

A multifunctional nanoprobe, which can be used for dual modal imaging and the detection of cancer cells, has been reported.

Design and synthesis of a chemosensor for the detection of Al3+ based on ESIPT

In this study, a simple fluorescent sensor 2-hydroxybenzcarbaldehyde-(2-methylquinoline-4-formyl) hydrazone (HL) has been designed, synthesized and characterized by 1H-NMR, IR, ESI-MS. Upon addition of Al3+, HL shows a large fluorescence enhancement (220-fold) at 484 nm. The reasons for this phenomenon are attributed to formation of a 1:1 complex (Ka = 5.6 × 104), which inhibits the excited-state intramolecular proton transfer (ESIPT) process and photo-induced electron transfer (PET) process. Other metal ions including Ba2+, Ca2+, Cd2+, Co2+, Cr3+, Hg2+, K+, Mg2+, Mn2+, Na+, Ni2+, Pb2+ and Zn2+, have almost no influence on the fluorescence. The lowest detection limit for Al3+ is calculated to be 7.2 × 10−7 M in ethanol.

A simple route to CoFe2O4 nanoparticles with shape and size control and their tunable peroxidase-like activity

Recent studies have suggested that the physical and chemical properties of nanoparticles (NPs) strongly depend on local chemical composition, size, and shape. Here, we report a new precursor-mediated growth of monodisperse magnetic cobalt ferrite (CoFe2O4) NPs with controlled size and shape. CoFe2O4 NPs with near corner-grown cubic, near cubic and polyhedron shape can be successfully prepared by simply tuning the amount of iron and cobalt acetylacetonates in oleic acid. Interestingly, the product shape varies from near corner-grown cubic to starlike by only changing the reaction temperature from 320 °C to 330 °C. These CoFe2O4 NPs exhibit size and shape-dependent peroxidase-like activity towards 3,3′,5,5′-tetramethylbenzdine (TMB) in the presence of H2O2, and thus exhibited different levels of peroxidase-like activities, in the order of spherical > near corner-grown cubic > starlike > near cubic > polyhedron; this order was closely related to their particle size and crystal morphology. CoFe2O4NPs exhibited high stability in HAc–NaAc buffer (pH = 4.0) and high activity over a broad pH (2.5–6.0). Furthermore, the Michaelis constants Km value for the CoFe2O4 NPs (0.006 mM) with TMB as the substrate was lower than HRP (0.062 mM) and Fe3O4 NPs (0.010 mM). After further surface functionalization with folic acid (FA), the folate-conjugated CoFe2O4 nanoparticles allow discrimination of HeLa cells (folate receptor overexpression) from NIH-3T3 cells (without folate receptor expression). Such investigation is of great significance for peroxidase nanomimetics with enhanced activity and utilization.

Controlled synthesis of MnFe2O4 nanoparticles and Gd complex-based nanocomposites as tunable and enhanced T1/T2-weighted MRI contrast agents

Successful development of magnetic nanoparticles (MNPs) with optimal size, shape, and composition is very desirable because they would increase the image contrast of magnetic resonance imaging (MRI). Here, we report a new precursor-mediated growth process of monodisperse MnFe2O4 NPs with controlled size and shape. MnFe2O4 NPs with plate-like shapes, spherical, and cubic can be successfully prepared by simply tuning the amount of Fe(acac)3 and Mn(acac)2 in oleic acid. Magnetism and MR properties of the particles were found to depend on their size and shape. These MnFe2O4 NPs, when conjugated with gadolinium and folic acid (FA), showed a simultaneous bright signal enhancement on the T1-weighted images and significant signal reduction on the T2-weighted image. In vitro MR imaging experiments also show that the developed multifunctional Gd:FA-DTPA-PEG-DIB-MnFe2O4 NPs enable targeted dual-contrast T1- and T2-weighted MR imaging of tumor cells over-expresses the folate receptor in vitro, and the T1- and T2-weighted MRI has been greatly improved. Our results clearly indicate that such an approach of forming multifunctional Gd:FA-DTPA-PEG-DIB-MnFe2O4 NPs is of great significance for T1- and T2-weighted MR imaging of specific cancer cells with high accuracy.

A highly sensitive and selective Schiff base fluorescent chemodosimeter for aluminum(III)

A fluorescent probe for Al3+, 4-(1′-phenyl-3′-methyl-5′-hydroxypyrazole)-1-acetone-(2′-hydroxybenzoyl) hydrazone (L), was prepared through a simple synthetic route. The fluorescent probe can detect Al3+ ions sensitively, in ethanol solution with the detection limit of 2.5 × 10−8 M via photoinduced electron transfer progress. The presence of interfering metal ions and chelators had little influence on the selectivity of Al3+. The probe could serve as an excellent chemodosimeter for Al3+ in ethanol.