Christine Schieber

Conjugation of Transferrin to Azide‐Modified CdSe/ZnS Core–Shell Quantum Dots using Cyclooctyne Click Chemistry

Twinkle twinkle quantum dot: Conjugation of biomolecules to azide-modified quantum dots (QDs) through a bifunctional linker, using strain-promoted azide-alkyne cycloaddition with the QD and a squaramide linkage to the biomolecule (see scheme). Transferrin-conjugated QDs were internalized by transferrin-receptor expressing HeLa cells.

PI(3,4,5)P3 Interactome

Immobilizing chemically synthesized analogues of PI(3,4,5)P3 onto Affi-10 beads and incorporating them into liposomes allowed their use as affinity absorbents in the comprehensive analysis of the phosphoinositide interactome using cytosolic cell extracts of the LIM1215 colon cancer cell line. This led to the identification of 282 proteins that either interact with PI(3,4,5)P3 or are indirectly captured as part of a complex containing a PI(3,4,5)P3 binding partner. Identification of the proteins was achieved using affinity/LC-MS/MS experiments.

Single-chain antibody conjugated to a cage amine chelator and labeled with positron-emitting copper-64 for diagnostic imaging of activated platelets

Imaging of activated platelets using an activation specific anti-GPIIb/IIIa integrin single-chain antibody (scFvanti-LIBS) conjugated to a positron emitting copper-64 complex of a cage amine sarcophagine chelator (MeCOSar) is reported. This tracer was compared in vitro to a (64)Cu(II) complex of the scFv conjugated to another commonly used macrocycle, DOTA. The scFvanti-LIBS-MeCOSar conjugate was radiolabeled with (64)Cu(II) rapidly under mild conditions and with higher specific activity than scFvanti-LIBS-DOTA. The utility of scFvanti-LIBS-MeCOSar as a diagnostic agent was assessed in vivo in a mouse model of acute thrombosis. The uptake of scFvanti-LIBS-(64)CuMeCOSar in the injured vessel was significantly higher than the noninjured vessel. Positron emission tomography (PET) was used to show accumulation of scFvanti-LIBS-(64)CuMeCOSar with high and specific uptake in the injured vessel. ScFvanti-LIBS-(64)CuMeCOSar is an excellent tool for highly sensitive in vivo detection of activated platelets in PET and has the potential to be used for early diagnosis of acute thrombotic events.

Copper and silver complexes of tris(triazole)amine and tris(benzimidazole)amine ligands: evidence that catalysis of an azide-alkyne cycloaddition ("click") reaction by a silver tris(triazole)amine complex arises from copper impurities.

The synthesis and characterization of a silver complex of the tripodal triazole ligand, tris(benzyltriazolylmethyl)amine (TBTA, L(1)), that is used as promoter to enhance Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reactions is reported. X-ray analysis of the silver(I) complex with L(1) reveals a dinuclear cation, [Ag2(L(1))2](2+), that is essentially isostructural to the copper(I) analogue. While the [Ag2(L(1))2](BF4)2 complex provides catalysis for the azide-alkyne cycloaddition process, evidence is presented that this arises from trace copper contamination. The synthesis of silver(I), copper(II), and copper(I) complexes of a second tripodal ligand, tris(2-benzimidazolymethyl)amine (L(2)), which is used to enhance the rate of CuAAC reactions, is also reported. X-ray crystallography of the Cu(I) complex [Cu(I)3(L(2))2(CH3CN)2](BF4)3 offers structural insight into previous mechanistic speculation about the role of this ligand in the CuAAC reaction.

Cellular up-regulation of Nedd4 family interacting protein 1 (Ndfip1) using low levels of bioactive cobalt complexes.

The delivery of metal ions using cell membrane-permeable metal complexes represents a method for activating cellular pathways. Here, we report the synthesis and characterization of new [CoIII(salen)(acac)] complexes capable of up-regulating the ubiquitin ligase adaptor protein Ndfip1. Ndfip1 is a neuroprotective protein that is up-regulated in the brain after injury and functions in combination with Nedd4 ligases to ubiquitinate harmful proteins for removal. We previously showed that Ndfip1 can be increased in human neurons using CoCl2 that is toxic at high concentration. Here we demonstrate a similar effect can be achieved by low concentrations of synthetic CoIII complexes that are non-toxic and designed to be activated following cellular entry. Activation is achieved by intracellular reduction of CoIII to CoII leading to release of CoII ions for Ndfip1 up-regulation. The cellular benefit of Ndfip1 up-regulation by CoIII complexes includes demonstrable protection against cell death in SH-SY5Y cells during stress. In vivo, focal delivery of CoIII complexes into the adult mouse brain was observed to up-regulate Ndfip1 in neurons. These results demonstrate that a cellular response pathway can be advantageously manipulated by chemical modification of metal complexes, and represents a significant step of harnessing low concentration metal complexes for therapeutic benefit.

Toward hypoxia-selective rhenium and technetium tricarbonyl complexes.

With the aim of preparing hypoxia-selective imaging and therapeutic agents, technetium(I) and rhenium(I) tricarbonyl complexes with pyridylhydrazone, dipyridylamine, and pyridylaminocarboxylate ligands containing nitrobenzyl or nitroimidazole functional groups have been prepared. The rhenium tricarbonyl complexes were synthesized with short reaction times using microwave irradiation. Rhenium tricarbonyl complexes with deprotonated p-nitrophenyl pyridylhydrazone ligands are luminescent, and this has been used to track their uptake in HeLa cells using confocal fluorescent microscopy. Selected rhenium tricarbonyl complexes displayed higher uptake in hypoxic cells when compared to normoxic cells. A (99m)Tc tricarbonyl complex with a dipyridylamine ligand bearing a nitroimidazole functional group is stable in human serum and was shown to localize in a human renal cell carcinoma (RCC; SK-RC-52) tumor in a mouse.

Water-soluble Bis(thiosemicarbazonato)copper(II) Complexes

The synthesis of four new water-soluble bis(thiosemicarbazone) ligands and their copper(ii) complexes is presented and their potential to be new ligands for copper radiopharmaceuticals is discussed. The ligands and complexes have been characterized by a combination of NMR spectroscopy, mass spectrometry, and X-ray crystallography. The electrochemical behaviour of two of the copper(ii) complexes was investigated by cyclic voltammetry and revealed that both complexes exhibited a quasi-reversible redox process attributed to a CuII/CuI process. Two of the new ligands were radiolabelled with positron-emitting 64Cu with a view to assessing their potential as ligands that bind radioactive copper isotopes for application in diagnostic radiopharmaceuticals. The cellular uptake of the copper complexes was investigated in SH-SY5Y cells.