New Methods for the Site-Selective Placement of Peptides on a Microelectrode Array: Probing VEGF-v107 Binding as Proof of Concept.

Cu(I)-catalyzed "click" reactions cannot be performed on a borate ester derived polymer coating on a microelectrode array because the Cu(II) precursor for the catalyst triggers background reactions between both acetylene and azide groups with the polymer surface. Fortunately, the Cu(II)-background reaction can itself be used to site-selectively add the acetylene and azide nucleophiles to the surface of the array. In this way, molecules previously functionalized for use in "click" reactions can be added directly to the array.

Cyclotron Production of High-Specific Activity 55Co and In Vivo Evaluation of the Stability of 55Co Metal-Chelate-Peptide Complexes.

This work describes the production of high-specific activity 55Co and the evaluation of the stability of 55Co-metal-chelate-peptide complexes in vivo. 55Co was produced via the 58Ni(p,α)55Co reaction and purified using anion exchange chromatography with an average recovery of 92% and an average specific activity of 1.96 GBq/μmol.

Harvesting (67)Cu from the Collection of a Secondary Beam Cocktail at the National Superconducting Cyclotron Laboratory.

Isotope harvesting is a promising new method to obtain isotopes for which there is no reliable continuous supply at present. To determine the possibility of obtaining radiochemically pure radioisotopes from an aqueous beam dump at a heavy-ion fragmentation facility, preliminary experiments were performed to chemically extract a copper isotope from a large mixture of projectile fragmentation products in an aqueous medium. In this work a 93 MeV/u secondary beam cocktail was collected in an aqueous beam stop at the National Superconducting Cyclotron Laboratory (NSCL) located on the Michigan State University (MSU) campus.

Evaluation of (89)Zr-pertuzumab in Breast cancer xenografts.

Pertuzumab is a monoclonal antibody that binds to HER2 and is used in combination with another HER2-specific monoclonal antibody, trastuzumab, for the treatment of HER2+ metastatic breast cancer. Pertuzumab binds to an HER2 binding site distinct from that of trastuzumab, and its affinity is enhanced when trastuzumab is present. We aim to exploit this enhanced affinity of pertuzumab for its HER2 binding epitope and adapt this antibody as a PET imaging agent by radiolabeling with (89)Zr to increase the sensitivity of HER2 detection in vivo.

Investigation of a vitamin B12 conjugate as a PET imaging probe.

Nutrient demand is a fundamental characteristic of rapidly proliferating cells. Vitamin B12 is vital for cell proliferation; thus neoplastic cells have an increased demand for this essential nutrient. In this study we exploited the vitamin B12 uptake pathway to probe the nutritional demand of proliferating cells with a radiolabeled B12 derivative in various preclinical tumor models.

Development of a Radiolabeled Irreversible Peptide Ligand for PET Imaging of Vascular Endothelial Growth Factor.

Unlabelled: Imaging agents based on peptide probes have desirable pharmacokinetic properties provided that they have high affinities for their target in vivo. An approach to improve a peptide ligand's affinity for its target is to make this interaction covalent and irreversible. For this purpose, we evaluated a (64)Cu-labeled affinity peptide tag, (64)Cu-L19K-(5-fluoro-2,4-dinitrobenzene) ((64)Cu-L19K-FDNB), which binds covalently and irreversibly to vascular endothelial growth factor (VEGF) as a PET imaging agent.

Imaging the L-type amino acid transporter-1 (LAT1) with Zr-89 immunoPET.

The L-type amino acid transporter-1 (LAT1, SLC7A5) is upregulated in a wide range of human cancers, positively correlated with the biological aggressiveness of tumors, and a promising target for both imaging and therapy. Radiolabeled amino acids such as O-(2-[(18)F]fluoroethyl)-L-tyrosine (FET) that are transport substrates for system L amino acid transporters including LAT1 have met limited success for oncologic imaging outside of the brain, and thus new strategies are needed for imaging LAT1 in systemic cancers. Here, we describe the development and biological evaluation of a novel zirconium-89 labeled antibody, [(89)Zr]DFO-Ab2, targeting the extracellular domain of LAT1 in a preclinical model of colorectal cancer.

Enhancing peptide ligand binding to vascular endothelial growth factor by covalent bond formation.

Formation of a stable covalent bond between a synthetic probe molecule and a specific site on a target protein has many potential applications in biomedical science. For example, the properties of probes used as receptor-imaging ligands may be improved by increasing their residence time on the targeted receptor. Among the more interesting cases are peptide ligands, the strongest of which typically bind to receptors with micromolar dissociation constants, and which may depend on processes other than simple binding to provide images.

New covalent capture probes for imaging and therapy, based on a combination of binding affinity and disulfide bond formation.

We describe the synthesis and development of new reactive DOTA-metal complexes for covalently targeting engineered receptors in vivo, which have superior tumor uptake and clearance properties for biomedical applications. These probes are found to clear efficiently through the kidneys and minimally through other routes, but bind persistently in the tumor target. We also explore the new technique of Cerenkov luminescence imaging to optically monitor radiolabeled probe distribution and kinetics in vivo.

Chemically modified antibodies as diagnostic imaging agents.

Notable new applications of antibodies for imaging involve genetically extracting the essential molecular recognition properties of an antibody, and in some cases enhancing them by mutation, before protein expression. The classic paradigm of intravenous administration of a labeled antibody to image not only its target but also its metabolism can be improved on. Protocols involving molecular targeting with an engineered unlabeled protein derived from an antibody, followed by capture of a small probe molecule that provides a signal, are being developed to a high level of utility.

Effect of structure in benzaldehyde oximes on the formation of aldehydes and nitriles under photoinduced electron-transfer conditions.

The mechanistic aspects of the photosensitized reactions of a series of benzaldehyde oximes (1a-o) were studied by steady-state (product studies) and laser flash photolysis methods. Nanosecond laser flash photolysis studies have shown that the reaction of the oxime with triplet chloranil (3CA) proceeds via an electron-transfer mechanism provided the free energy for electron transfer (DeltaG(ET)) is favorable; typically, the oxidation potential of the oxime should be below 2.0 V.