Luminescence Screening Assays for the Identification of Sensitizers for Lanthanides Based on the Controlled Formation of Ternary Lanthanide Complexes with DTPA-Bisamide Ligands

Chelating silica nanoparticles for efficient antibiotic delivery and particle imaging in Gram-negative bacteria

The inefficacy of antibiotics against Gram-negative bacteria is a major challenge for treatment of many clinically important bacterial infections. The complex structure of the double cell membrane of Gram-negative bacteria makes it inaccessible to many key antibiotics such as vancomycin and also presents a major challenge for drug development. In this study we design of a novel hybrid silica nanoparticle system bearing membrane targeting groups with the antibiotic encapsulated together with a ruthenium luminescent tracking agent, for optical detection of the nanoparticle delivery in the bacterial cell. The hybrid system shows delivery of vancomycin and efficacy against a library of Gram negative bacterial species. Evidence of penetration of nanoparticles in bacteria cells is achieved via luminescence of the ruthenium signal. Our studies show that nanoparticles modified with aminopolycarboxylate chelating groups are an effective delivery system in bacterial growth inhibition in species whereas the molecular antibiotic is ineffective. This design provides a new platform for delivery of antibiotics that cannot alone penetrate the bacterial membrane.

Evaluation of quinoline as a remote sensitiser for red and near-infrared emissive lanthanide(III) ions in solution and the solid state

In order to evaluate quinoline as a remote sensitiser, we have prepared a DTPA based ligand, H3L, bearing quinoline bisamide arms for the complexation of a range of lanthanide(III) ions to give the neutral complexes LnLwhere Ln(3+) = Y(3+), Eu(3+), Sm(3+), Tb(3+), Er(3+), Yb(3+), Nd(3+), Gd(3+). Detection of the phosphorescence signal exhibited by the GdLcomplex at 77 K confirmed that the triplet energy level of the sensitiser at 21,190 cm(-1) was suitable for the indirect population of a range of lanthanide luminescent states. A full photophysical analysis of the complexes reveals that SmL and EuL display red emission when excited through the ligand-based absorption band centred at 330 nm, extending the excitation to violet light around 370 nm. We demonstrate that quinoline sensitizes near-infrared emission in the YbL, ErL and NdL complexes, in powder form as well as in solution. Most importantly, the luminescence for YbL and NdL was sufficiently efficient to be detected in non-deuterated solvent.