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A new polydentate tripodal ligand T2soxMe was synthesized to take advantage of the chelating effect of tridentate 8- hydroxyquinolinate subunits. Potentiometric and spectrophotometric titrations reveal seven pKa values of between 3.7 and 10.2. In water, the use of T2soxMe leads to thermodynamically stable and soluble LnIII complexes at physiological pH, with conditional stability constants in the range logb11=7.8..8.6. The chelates are resistant toward hydrolysis and show interesting photophysical properties, particularly in the near infrared (NIR) range. The emission lifetimes of the NdIII and YbIII complexes recorded in D2O and H2O suggest the absence of water molecules in the first coordination sphere of the metal ions. Moreover, the low energy of the triplet state allows efficient energy transfer from the ligand to the metal ions: in water at pH 7.4, the sensitization efficacy of the NIR luminescence reaches 75 and 100% for NdIII and YbIII, respectively, leading to overall quantum yields of 0.027 and 0.13%; ErIII luminescence is also detected. According to the WST-1 test, the YbIII podate at concentrations of up to 250 mm does not display sizeable cytotoxicity for Jurkat cells after 24 h of incubation. Finally, the same podate is shown to couple to human serum albumin, leading to an increase of 50% in the NIR- luminescence intensity.

We propose an original concept to perform a complete on-chip sandwich immunoassay on magnetic nanoparticles that are self-assembled in chains in a uniform magnetic field. The magnetic chains are retained over periodically enlarged cross sections of a microfluidic channel. Thereby they strongly interact with the flow and rapidly capture the total of a low number of target molecules from nanoliter sample volumes. As an example, we demonstrate the detection of murine monoclonal antibodies in a noncompetitive sandwich immunoassay with a detection limit of 1 ng mL-1 in nanoliters of hybridoma cell culture medium.

A new macrocyclic ligand, $L^3$, has been synthesised, based on the cyclen framework grafted with three phenacyl light-harvesting groups and a C5-alkyl chain bearing a carboxylic acid function as a potential linker for biological material. Acidity constants are determined by spectrophotometric titrations, as well as conditional stability constants for the resulting 1:1 complexes with trivalent lanthanide ions. The complexes have stabilities comparable to 1,4,7,10-tetrakis(carbamoylmethyl)- 1,4,7,10- tetraazacyclododecane (dtma) complexes, with $pLn \approx 12-13$. Photophysical properties of the ligand and of the $EuL^3$ and $TbL^3$ complexes have been determined for both microcrystalline samples and solutions in water and acetonitrile. They point to the metal ion being present in an environment with axial symmetry derived from the $C_4$ point group. The hydration number determined for $TbL^3$ decreases with increasing pH value and becomes fractional at pH 7.5, which points to an equilibrium between two differently solvated species and probably to the participation of the deprotonated carboxylic acid chain in the complexation. The quantum yields in water (1.9% for $Eu^{III}$, 3.4% for $Tb^{III}$) are smaller than those for complexes with the symmetrically substituted parent macrocycle, but efficient luminescence resonant energy transfer (LRET) was observed when Cy5 dye was added to the solutions. Finally, the influence of the $TbL^3$ complex on cell viability is tested on both malignant (5D10 mouse hybridoma, Jurkat human T leukaemia, MCF-7 human breast carcinoma) and non-malignant (Hacat human keratinocyte) cell lines. Cell viability after 24 h incubation at $37^ {\circ}C$ with $500\mu m$ $TbL^3$ was >90% for all cell lines, except Jurkat (>70%). All of these properties make $LnL^3$ complexes interesting potential probes for bioanalyses.