Poly(amidoamine) Dendrimer Based MRI Contrast Agents Exhibiting Enhanced Relaxivities Derived via Metal Preligation Techniques

This report presents the preparation and characterization of three [Gd-C-DOTA]−1−dendrimer assemblies by way of analysis, NMRD spectroscopy, and photon correlation spectroscopy (PCS). The metal−ligand chelates were preformed in alcohol media prior to conjugation to generation 4, 5, and 6 PAMAM dendrimers. The dendrimer-based agents were purified by Sephadex G-25 column chromatography. The combustion analysis, SE-HPLC, and UV−vis data indicated chelate to dendrimer ratios of 28:1, 61:1 and 115:1, respectively. Molar relaxivity measured at pH 7.4, 22 °C, and 3 T (29.6, 49.8, and 89.1 mM−1 s−1) indicated the viability of conjugates as MRI contrast agents. 1/T1 NMRD profiles were measured at 23 °C and indicated that at 22 MHz the 1/T1 reached a plateau at 60, 85, and 140 mM−1 s−1 for the generation 4, 5, and 6 dendrimer conjugates, respectively. The PCS data showed the respective sizes of 5.2, 6.5, and 7.8 nm for G-4, 5, and 6 conjugates

Improved Speciation Characteristics of PEGylated Indocyanine Green-Labeled Panitumumab: Revisiting the Solution and Spectroscopic Properties of a Near-Infrared Emitting anti-HER1 Antibody for Optical Imaging of Cancer

A water-soluble amine-reactive PEGylated analogue of near-infrared emitting dye indocyanine green (5) was synthesized and used to label the anti-HER1 antibody panitumumab (Vectibix) at various equivalents. These conjugates were compared with non-PEGylated analogue conjugate products and the solution speciation analyzed with UV−vis spectrophotometry, size exclusion HPLC, and SDS-PAGE. PEGylation of the bioconjugates was successful in preventing aggregation in solution, a phenomenon observed with the non-PEGylated bioconjugates presumably due to the hydrophobicity of indocyanine green. Competitive radioimmunoassay demonstrated that the targeting moiety of the PEGylated bioconjugates was conserved. Fluorescence microscopy also demonstrated membrane binding of the bioconjugate to HER1-expressing A431 cells. Hence, these bioconjugates are suitable candidates for the in vivo optical imaging of HER1-expressing tumors

Syntheses and Characterizations of Metal Complexes Derived from <i>cis,cis</i>-1,3,5-Triaminocyclohexane-<i>N</i>,<i>N</i>‘,<i>N</i>‘ ‘-triacetic Acid

A convenient six-step procedure is developed to routinely prepare the hexadentate ligand cis,cis-1,3,5-triaminocyclohexane-N,N‘,N‘ ‘-triacetic acid (H3tachta) as an HCl salt. Complexes of gallium(III) and indium(III), [Ga(tachta)] and [In(tachta)], are synthesized from the reactions of the ligand and the corresponding metal precursors. Copper(II), palladium(II), and cobalt(II) complexes, [Cu(Htachta)], [Pd(Htachta)], and [Co(Htachta)], are obtained from the reactions of H3tachta with the corresponding metal chlorides. The structures of H3tachta·3HCl·2H2O (C12H28Cl3N3O8) and [Ga(tachta)] (C12H18GaN3O6) are characterized. The crystal of H3tachta·3HCl·2H2O is monoclinic, of the space group P21/c, with a = 15.1688(4) Å, b = 8.4708(2) Å, c = 15.9408(2) Å, β = 108.058(1)°, and Z = 4; that of [Ga(tachta)] is cubic, of space group Pa3, with a = 14.0762(1) Å and Z = 8. The gallium atom of [Ga(tachta)] is six-coordinated in the solid state, and the complex assumes a pseudooctahedronal geometry with the completely deprotonated hexadentate ligand encapsulating the metal ion

Synthesis, Conjugation, and Radiolabeling of a Novel Bifunctional Chelating Agent for ²²⁵Ac Radioimmunotherapy Applications

225Ac (t1/2 = 10 days) is an alternative α-emitter that has been proposed for radioimmunotherapy (RIT) due to its many favorable properties, such as half-life and mode of decay. The factor limiting use of 225Ac in RIT is the lack of an acceptably stable chelate for in vivo applications. Herein is described the first reported bifunctional chelate for 225Ac that has been evaluated for stability for in vivo applications. The detailed synthesis of a bifunctional chelating agent 2-(4-isothiocyanatobenzyl)-1,4,7,10,13,16-hexaazacyclohexadecane- 1,4,7,10,13,16-hexaacetic acid (HEHA-NCS) is reported. This ligand was conjugated to three monoclonal antibodies, CC49, T101, and BL-3 with chelate-to-protein ratios between 1.4 and 2. The three conjugates were radiolabeled with 225Ac, and serum stability study of the [225Ac]BL-3-HEHA conjugate was performed

Synthesis of DTPA Analogues Derived from Piperidine and Azepane: Potential Contrast Enhancement Agents for Magnetic Resonance Imaging

Two DTPA derivatives (PIP-DTPA and AZEP-DTPA) as potential contrast enhancement agents in MRI are synthesized. The T1 and T2 relaxivities of their corresponding Gd(III) complexes are reported. At clinically relevant field strengths, the relaxivities of the complexes are comparable to that of the contrast agent, Gd(DTPA) which is in clinical use. The serum stability of the 153Gd-labeled complexes is assessed by measuring the release of 153Gd from the ligands. The radiolabeled Gd chelates are found to be kinetically stable in human serum for up to at least 14 days without any measurable loss of radioactivity

Syntheses and Characterizations of Metal Complexes Derived from <i>cis,cis</i>-1,3,5-Triaminocyclohexane-<i>N</i>,<i>N</i>‘,<i>N</i>‘ ‘-triacetic Acid

A convenient six-step procedure is developed to routinely prepare the hexadentate ligand cis,cis-1,3,5-triaminocyclohexane-N,N‘,N‘ ‘-triacetic acid (H3tachta) as an HCl salt. Complexes of gallium(III) and indium(III), [Ga(tachta)] and [In(tachta)], are synthesized from the reactions of the ligand and the corresponding metal precursors. Copper(II), palladium(II), and cobalt(II) complexes, [Cu(Htachta)], [Pd(Htachta)], and [Co(Htachta)], are obtained from the reactions of H3tachta with the corresponding metal chlorides. The structures of H3tachta·3HCl·2H2O (C12H28Cl3N3O8) and [Ga(tachta)] (C12H18GaN3O6) are characterized. The crystal of H3tachta·3HCl·2H2O is monoclinic, of the space group P21/c, with a = 15.1688(4) Å, b = 8.4708(2) Å, c = 15.9408(2) Å, β = 108.058(1)°, and Z = 4; that of [Ga(tachta)] is cubic, of space group Pa3, with a = 14.0762(1) Å and Z = 8. The gallium atom of [Ga(tachta)] is six-coordinated in the solid state, and the complex assumes a pseudooctahedronal geometry with the completely deprotonated hexadentate ligand encapsulating the metal ion

Differential expression of genes involved in apoptosis in LS-174T i.p. xenografts following treatment with Gemcitabine and α-treatment.

Differential expression of genes involved in apoptosis in LS-174T i.p. xenografts following treatment with Gemcitabine and α-treatment.</p

Streptavidin in Antibody Pretargeting. 5. Chemical Modification of Recombinant Streptavidin for Labeling with the α-Particle-Emitting Radionuclides ²¹³Bi and ²¹¹At

We are investigating the use of recombinant streptavidin (rSAv) as a carrier molecule for the short-lived α-particle-emitting radionuclides 213Bi (t1/2 = 45.6 min) and 211At (t1/2 = 7.21 h) in cancer therapy. To utilize rSAv as a carrier, it must be modified in a manner that permits rapid chelation or bonding with these short-lived radionuclides and also modified in a manner that diminishes its natural propensity for localization in the kidney. Modification for labeling with 213Bi was accomplished by conjugation of rSAv with the DTPA derivative p-isothiocyanato-benzyl-CHX-A′′ (CHX-A′′), 3a. Modification for direct labeling with 211At was accomplished by conjugation of rSAv with an isothiocyanatophenyl derivative of a nido-carborane (nCB), 3b, or an isothiocyanatophenyl-dPEG/decaborate(2-) derivative, 3c. After conjugation of the chelating or bonding moiety, rSAv was further modified by reaction with an excess (50–100 equivalents) of succinic anhydride. Succinylation of the lysine amines has previously been shown to greatly diminish kidney localization. rSAv modified by conjugation with 3a and succinylated rapidly radiolabeled with 213Bi (211At labeling of modified rSAv was accomplished in aqueous solution using chloramine-T as the oxidant. Astatination of rSAv conjugated with 3b and succinylated occurred very rapidly (3c and succinylated was also very rapid (2a, which did not have conjugated borane cage moieties, resulted in a much lower radiolabeling yield (18%). The 213Bi or 211At-labeled modified rSAv preparations were mixed with the corresponding 125I-labeled rSAv, and dual-label in vivo distributions were obtained in athymic mice. The in vivo data show that 213Bi-labeled succinylated rSAv [213Bi]6a has tissue concentrations similar to those of 125I-labeled modified rSAv [125I]6b, suggesting that 213Bi is quite stable toward release from the chelate in vivo. In vivo data also indicate that the 211At-labeled rSAv conjugated with 3b or 3c and succinylated are stable to in vivo deastatination, whereas succinylated rSAv lacking a boron cage moiety is subject to some deastatination. The modified rSAv conjugated with nido-carborane derivative 3b has a higher retention in many tissues than rSAv without the carborane conjugated. Interestingly, the rSAv conjugated with 3c, which also contains an m-dPEG12 moiety, has significantly decreased concentrations in blood and other tissues when compared with those of direct-labeled rSAv, suggesting that it may be a good candidate for further study. In conclusion, rSAv that has been modified with CHX-A′′ and succinylated (i.e., 5a) may be useful as a carrier of 213Bi. The encouraging results obtained with the PEGylated decaborate(2-) derivative 3c and succinylated (i.e., 5c) suggests that its further study as a carrier of 211At in pretargeting protocols is warranted

Expression of genes related to BASC (BRCA1-associated genome surveillance complex) and HRR in response to sequential treatment with Gem and ²¹²Pb-trastuzumab.

<p>Mice bearing i.p. LS-174T xenografts were pre-treated with Gem followed 24 h thereafter with ²¹²Pb-RIT. (A) Expression of <i>BRCA1</i>, <i>CHK1</i>, <i>MSH2</i> and was determined by qRT-PCR. Results represent the average of a minimum of three replications. (B) Binding abundance to E2F1 was determined by ChIP using specific primers for <i>CHK1</i> and <i>MSH2</i>. (C) Immunoblot analysis for RAD51B and XRCC2 was performed with tumor tissue collected as described. RAD51B and XRCC2 were detected at 32 kDa and 42 kDa, respectively. Equal protein loading control was GAPDH.</p

Tricationic Metal Complexes ([ML][NO₃]₃, M = Ga, In) of <i>N,N</i>‘<i>,N</i>‘‘-Tris(2-pyridylmethyl)- <i>cis</i>-1,3,5-triaminocyclohexane: Preparation and Structure

Tricationic Metal Complexes ([ML][NO3]3, M = Ga, In) of N,N‘,N‘‘-Tris(2-pyridylmethyl)- cis-1,3,5-triaminocyclohexane:  Preparation and Structur