Synthesis of N-heterocyclic ligands for use in affinity and mixed mode chromatography

A high-density 4-vinylpyridine membrane for rapid purification of antibodies

In order to further investigate the mechanism of action of rituximab in humans and its biotransformation, it is essential to obtain high purity rituximab while maintaining its structural and functional integrity. In this study, we proposed and fabricated a small-molecule 4-vinylpyridine-modified high-density membrane material (P4VP@M) using the surface-initiated atom transfer radical polymerization (SI-ATRP) method. This approach can overcome the limitations of conventional enrichment materials, such as long incubation time and low adsorption capacity. P4VP@M incorporates high-density HEMA polymer brushes to prevent non-specific protein adsorption and 4-vinylpyridine polymer brushes for high-performance rituximab enrichment under mild conditions. In addition, P4VP@M has high permeability, hydrophilicity and mechanical strength. Compared to previous methods, this novel material showed excellent rituximab binding capacity (100.3 mg g-1), shorter processing time (only 15 min), and lower cost (only $2). Notably, P4VP@M was able to purify rituximab rapidly and efficiently from the mixture samples and exhibited good selectivity, recovery (>92.6%) and purity (>94.8%). Thus, this proposed purification strategy using P4VP@M has great potential in enriching target proteins from complex samples, as well as contributing to the in-depth study of their biological functions.

Studies on the binding sites of IgG2 monoclonal antibodies recognized by terpyridine-based affinity ligands

This investigation has examined the origin of the molecular recognition associated with the interaction of monoclonal IgG2's with terpyridine-based ligands immobilized onto agarose-derived chromatographic adsorbents. Isothermal titration calorimetric (ITC) methods have been employed to acquire thermodynamic data associated with the IgG2-ligand binding. These ITC investigations have documented that different enthalpic and entropic processes are involved depending on the nature of the chemical substituents in the core structure of the terpyridinyl moiety. In addition, molecular docking studies have been carried out with IgG2 structures with the objective to identify possible ligand binding sites and key interacting amino acid residues. These molecular docking experiments with the different terpyridine-based ligands have shown that all of the examined ligands can potentially undergo favorable interactions with a site located within the Fab region of the IgG2. However, another favorable binding site was also identified from the docking poses to exist within the Fc region of the IgG2 for some, but not all, of the ligands studied. These investigations have provided a basis to elucidate the unique binding properties and chromatographic behaviors shown by several substituted terpyridine ligands in their interaction with IgGs of different isotype. Copyright © 2016 John Wiley & Sons, Ltd.

Design, synthesis and evaluation of pyridine-based chromatographic adsorbents for antibody purification

The structure-based design and synthesis of four series of adsorbents for antibody purification by affinity chromatography has been investigated. The structures of 10 ligands were based on pyridine compounds that possessed thioalkyl substituents containing a primary amine, which was required for immobilisation of the ligands onto an epoxy-activated matrix (epoxy-Sepharose Fast Flow(®)). These new adsorbents were screened in monoclonal antibody binding assays in order to determine optimal buffer conditions for capture and elution under static and dynamic adsorption conditions. From batch binding measurements, the binding affinities, KD's, were found to be in the range of 3-5μM and the maximum capacities, qm's were between 12 and 30mgmAb/mL resin, depending on the substitution pattern of the thioalkylamine in the N-heterocyclic ring structure of the ligands. The amount of monoclonal antibody bound and eluted under overload conditions was influenced by the concentration of the sample loaded, the flow rate at which the sample was applied and the loading/volume. Further, the ability of these new adsorbents to selectively capture monoclonal antibodies of the class IgG1 from supernatants derived from genetically engineered CHO cells cultured in chemically defined media was investigated, documenting efficient capture and recovery of the mAb.

A novel pyrene-2-(pyridin-2-ylmethylsulfanyl)ethylamine based turn-on dual sensor for Al3+: experimental and computational studies

A pyrene based pyrene-2-(pyridin-2-ylmethylsulfanyl)-ethylamine (PP) is found to exhibit a turn-on chemo- and fluorogenic dual sensing of Al³⁺ through PET blocking and CHEF effect.

Novel, cysteine-modified chelation strategy for the incorporation of [M(I)(CO)(3)](+) (M = Re, (99m)Tc) in an α-MSH peptide

Engineering peptide-based targeting agents with residues for site-specific and stable complexation of radionuclides is a highly desirable strategy for producing diagnostic and therapeutic agents for cancer and other diseases. In this report, a model N-S-N(Py) ligand (3) and a cysteine-derived α-melanocyte stimulating hormone (α-MSH) peptide (6) were used as novel demonstrations of a widely applicable chelation strategy for incorporation of the [M(I)(CO)(3)](+) (M = Re, (99m)Tc) core into peptide-based molecules for radiopharmaceutical applications. The structural details of the core ligand-metal complexes as model systems were demonstrated by full chemical characterization of fac-[Re(I)(CO)(3)(N,S,N(Py)-3)](+) (4) and comparative high-performance liquid chromatography (HPLC) analysis between 4 and [(99m)Tc(I)(CO)(3)(N,S,N(Py)-3)](+) (4a). The α-MSH analogue bearing the N-S-N(Py) chelate on a modified cysteine residue (6) was generated and complexed with [M(I)(CO)(3)](+) to confirm the chelation strategy's utility when applied in a peptide-based targeting agent. Characterization of the Re(I)(CO)(3)-6 peptide conjugate (7) confirmed the efficient incorporation of the metal center, and the (99m)Tc(I)(CO)(3)-6 analogue (7a) was explored as a potential single photon emission computed tomography (SPECT) compound for imaging the melanocortin 1 receptor (MC1R) in melanoma. Peptide 7a showed excellent radiolabeling yields and in vitro stability during amino acid challenge and serum stability assays. In vitro B16F10 melanoma cell uptake of 7a reached a modest value of 2.3 ± 0.08% of applied activity at 2 h at 37 °C, while this uptake was significantly reduced by coincubation with a nonlabeled α-MSH analogue, NAPamide (3.2 μM) (P < 0.05). In vivo SPECT/X-ray computed tomography (SPECT/CT) imaging and biodistribution of 7a were evaluated in a B16F10 melanoma xenografted mouse model. SPECT/CT imaging clearly visualized the tumor at 1 h post injection (p.i.) with high tumor-to-background contrast. Blocking studies with coinjected NAPamide (10 mg per kg of mouse body weight) confirmed the in vivo specificity of 7a for MC1R-positive tumors. Biodistribution results with 7a yielded a moderate tumor uptake of 1.20 ± 0.09 percentage of the injected radioactive dose per gram of tissue (% ID/g) at 1 h p.i. Relatively high uptake of 7a was also seen in the kidneys and liver at 1 h p.i. (6.55 ± 0.36% ID/g and 4.44 ± 0.17% ID/g, respectively), although reduced kidney uptake was seen at 4 h p.i. (3.20 ± 0.48% ID/g). These results demonstrate the utility of the novel [M(I)(CO)(3)](+) chelation strategy when applied in a targeting peptide.