Phosphonium-containing diblock copolymers for enhanced colloidal stability and efficient nucleic acid delivery.

RAFT polymerization successfully controlled the synthesis of phosphonium-based AB diblock copolymers for nonviral gene delivery. A stabilizing block of either oligo(ethylene glycol(9)) methyl ether methacrylate or 2-(methacryloxy)ethyl phosphorylcholine provided colloidal stability, and the phosphonium-containing cationic block of 4-vinylbenzyltributylphosphonium chloride induced electrostatic nucleic acid complexation. RAFT polymerization generated well-defined stabilizing blocks (M(n) = 25000 g/mol) and subsequent chain extension synthesized diblock copolymers with DPs of 25, 50, and 75 for the phosphonium-containing block. All diblock copolymers bound DNA efficiently at ± ratios of 1.0 in H(2)O, and polyplexes generated at ± ratios of 2.0 displayed hydrodynamic diameters between 100 and 200 nm. The resulting polyplexes exhibited excellent colloidal stability under physiological salt or serum conditions, and they maintained constant hydrodynamic diameters over 24 h. Cellular uptake studies using Cy5-labeled DNA confirmed reduced cellular uptake in COS-7 and HeLa cells and, consequently, resulted in low transfection in these cell lines. Serum transfection in HepaRG cells, which are a predictive cell line for in vivo transfection studies, showed successful transfection using all diblock copolymers with luciferase expression on the same order of magnitude as Jet-PEI. All diblock copolymers exhibited low cytotoxicity (>80% cell viability). Promising in vitro transfection and cytotoxicity results suggest future studies involving the in vivo applicability of these phosphonium-based diblock copolymer delivery vehicles.

Cationic glycopolymers for the delivery of pDNA to human dermal fibroblasts and rat mesenchymal stem cells.

Progenitor and pluripotent cell types offer promise as regenerative therapies but transfecting these sensitive cells has proven difficult. Herein, a series of linear trehalose-oligoethyleneamine "click" copolymers were synthesized and examined for their ability to deliver plasmid DNA (pDNA) to two progenitor cell types, human dermal fibroblasts (HDFn) and rat mesenchymal stem cells (RMSC). Seven polymer vehicle analogs were synthesized in which three parameters were systematically varied: the number of secondary amines (4-6) within the polymer repeat unit (Tr4(33), Tr5(30), and Tr6(32)), the end group functionalities [PEG (Tr4(128)PEG-a, Tr4(118)PEG-b), triphenyl (Tr4(107)-c), or azido (Tr4(99)-d)], and the molecular weight (degree of polymerization of about 30 or about 100) and the biological efficacy of these vehicles was compared to three controls: Lipofectamine 2000, JetPEI, and Glycofect. The trehalose polymers were all able to bind and compact pDNA polyplexes, and promote pDNA uptake and gene expression [luciferase and enhanced green fluorescent protein (EGFP)] with these primary cell types and the results varied significantly depending on the polymer structure. Interestingly, in both cell types, Tr4(33) and Tr5(30) yielded the highest luciferase gene expression. However, when comparing the number of cells transfected with a reporter plasmid encoding enhanced green fluorescent protein, Tr4(33) and Tr4(107)-c yielded the highest number of HDFn cells positive for EGFP. Interestingly, with RMSCs, all of the higher molecular weight analogs (Tr4(128)PEG-a, Tr4(118)PEG-b, Tr4(107)-c, Tr4(99)-d) yielded high percentages of cells positive for EGFP (30-40%).

Polymer beacons for luminescence and magnetic resonance imaging of DNA delivery.

The delivery of nucleic acids with polycations offers tremendous potential for developing highly specific treatments for various therapeutic targets. Although materials have been developed and studied for polynucleotide transfer, the biological mechanisms and fate of the synthetic vehicle has remained elusive due to the limitations with current labeling technologies. Here, we have developed polymer beacons that allow the delivery of nucleic acids to be visualized at different biological scales. The polycations have been designed to contain repeated oligoethyleneamines, for binding and compacting nucleic acids into nanoparticles, and lanthanide (Ln) chelates [either luminescent europium (Eu(3+)) or paramagnetic gadolinium (Gd(3+))]. The chelated Lns allow the visualization of the delivery vehicle both on the nm/microm scale via microscopy and on the sub-mm scale via MRI. We demonstrate that these delivery beacons effectively bind and compact plasmid (p)DNA into nanoparticles and protect nucleic acids from nuclease damage. These delivery beacons efficiently deliver pDNA into cultured cells and do not exhibit toxicity. Micrographs of cultured cells exposed to the nanoparticle complexes formed with fluorescein-labeled pDNA and the europium-chelated polymers reveal effective intracellular imaging of the delivery process. MRI of bulk cells exposed to the complexes formulated with pDNA and the gadolinium-chelated structures show bright image contrast, allowing visualization of effective intracellular delivery on the tissue-scale. Because of their versatility, these delivery beacons posses remarkable potential for tracking and understanding nucleic acid transfer in vitro, and have promise as in vivo theranostic agents.

A beta-cyclodextrin "click cluster" decorated with seven paramagnetic chelates containing two water exchange sites.

The development of novel macromolecular contrast agents that offer enhanced relaxivity profiles at high magnetic fields have the potential to greatly improve the diagnosis, understanding, and treatment of disease. To this end, we have designed a monodiperse paramagnetic beta-cyclodextrin click cluster decorated with seven paramagnetic arms. A novel alkyne-functionalized diethylenetriaminetetraacetic acid (DTTA) chelate (6) has been created and coupled to a per-azido-beta-cyclodextrin core (7) to yield the precursor macromolecule (8). After removal of the protecting groups and titrating with Gd (3+), the final paramagnetic click cluster, Gd10, was obtained. Luminescence measurements were carried out in H 2O and D 2O on an analogous structure, Eu10, and indicated that at each lanthanide has an average of 1.8 water exchange sites, which is important for enhancing relaxivity and MRI resolution. This discrete paramagnetic click cluster yields a high relaxivity profile (43.4 mM (-1) s (-1) per molecule and 6.2 mM (-1) s (-1) per Gd (3+) at 9.4 T) and enhanced contrast on a human MRI scanner as compared to a commercial agent, Magnevist (3.2 mM (-1) s (-1) at 9.4 T). Moreover, the useful inclusion properties exhibited by beta-cyclodextrin also make this an excellent host scaffold to functionalize via noncovalent assembly with receptor specific targeting moieties for biomolecular imaging.

Studies of selenium-containing volatiles in roasted coffee.

Coffee has been an important and heavily used beverage in many cultures over a long period of time. Although sulfur species have been found to be abundant constituents, no work to date has explored the presence of selenium analogues. Investigation of volatile selenium species from green coffee beans, roasted beans, and brewed coffee drink was performed using solid phase microextraction (SPME) sample preconcentration in conjunction with GC/ICP-MS. Several volatile selenium species at trace levels were detected from roasted coffee beans as well as in the steam from brewed coffee drinks. No detectable selenium (and sulfur) species, however, were found in the headspace of green beans, indicating that selenium-containing volatiles are formed during roasting, as is the case for the sulfur volatiles. Matching standards were prepared and used to identify the compounds found in coffee. Artificial supplementation of the green coffee beans with selenium before roasting was performed to further characterize the selenium-containing volatiles formed during the coffee-roasting process.