We describe a new method for coating superparamagnetic iron oxide nanoparticles (SPIOs) and demonstrate that, by fine-tuning the core size and PEG coating of SPIOs, the T2 relaxivity per-particle can be increased by > 200 fold. With 14 nm core and PEG1000 coating, SPIOs can have T2 relaxivity of 385 s−1mM−1, which is among the highest of all SPIOs reported. In vivo tumor imaging results demonstrated the potential of the SPIOs for clinical applications.

We coated nanoparticles including iron oxide nanoparticles and quantum dots with phospholipid-PEG using the newly developed dual solvent exchange method and demonstrated that, compared with the conventional film hydration method, the coating efficiency and quality of coated nanoparticles can be significantly improved. A better control of surface coating density and the amount of reactive groups on nanoparticle surface is achieved, allowing conjugation of different moieties with desirable surface concentrations, thus facilitating biomedical applications of nanoparticles.

A new class of high molecular weight polysulfated PEO dendrimer-like glycopolymer has been synthesized by a combination of arm-first and core-first methodologies followed by trichloroacetimidate glycosidation as a facile bioconjugation strategy. An L-selectin antagonist was identified that exhibits 103-fold greater activity than other multivalent sLex glycopolymers and 20-50 times greater potency than other linear heparinoids. A significant reduction in inflammatory cell recruitment was observed in vivo.

Star-block copolymers (PEO3-b-PAA3) and dendrimer-like copolymers (PEO3-b-PAA6) consisting of three inner poly(ethylene oxide) (PEO) arms and either three or six peripheral poly(acrylic acid) (PAA) blocks were derived by a core-first approach. To this end, the OH end groups of three-arm PEO stars prepared anionically were derivatized into either three or six bromo-ester functions that served to grow the poly(tert-butyl acrylate) (PtBA) blocks by atom transfer radical polymerization (ATRP) in a controlled fashion. This could be achieved at 80 °C in toluene in the presence of CuBr/pentamethyldiethylenetriamine (CuBr/PMDETA) as the catalyst system. Characterization by size exclusion chromatography and NMR of star-block copolymers (PEO 3-b-PtBA3) and dendrimer-like copolymers (PEO3-b-PtBA6) confirmed their well-defined character. Subsequent treatment with trifluoroacetic acid selectively hydrolyzed the PtBA blocks, leading to the targeted PEO3-b-PAA3 and PEO3-b-PAA6 compounds. Alternatively, an arm-first methodology utilizing a divinylic comonomer as the linking agent was applied to access star-block copolymers incorporating an inner PAA part and a peripheral PEO layer. To this end, preformed PEO-b-PtBA diblock copolymers were reacted with divinylbenzene in anisole in the presence of CuBr/PMDETA. Some of the factors controlling the formation of (PtBA-b-PEO) f stars were examined. These included the molar ratio of the linking agent to the diblock precursor, the molar mass of the latter species, and the reaction time. Finally, selective hydrolysis led to the expected double hydrophilic star-block copolymers noted (PAA-b-PEO) f.

This paper highlights our recent efforts to engineer polymer chains in star‐like and dendrimer‐like architectures using atom‐transfer radical polymerization (ATRP) and anionic ring‐opening polymerization (AROP) of ethylene oxide as synthetic tools. The scope and limitations of ATRP are first discussed when this method of controlled radical polymerization is applied to multifunctional initiators for the synthesis of star polymers by the core‐first approach. The switch from ATRP to AROP of ethylene oxide and vice versa allows access to branched amphiphilic block copolymers exhibiting core–shell structures. Stress is also put on the methodologies for the selective branching of polymeric chain‐ends, with a view to introducing ω‐geminal functionalities from which further polymer branches can be grown. When linear polymer precursors are used, such a strategy leads to asymmetric and mikto‐arm stars but the same can be applied to multi‐arm stars so as to generate so‐called ‘dendrimer‐like (co)polymers’ that are dendrimers with true macromolecular generations. Copyright © 2006 Society of Chemical Industry

A series of derivatized arylamine initiators were used to generate chain-end functionalized glycopolymers by cyanoxyl-mediated free-radical polymerization. Significant features of this strategy include the capacity to produce polymers of low polydispersity (PDI < 1.5) under aqueous conditions using unprotected monomers bearing a wide range of functional groups. In addition, the presence of a phenyl ring simplifies calculation of polymer saccharide content and molar mass by 1 H NMR. It is particularly noteworthy, however, that derivatized arylamine initiators in conjunction with the presence of a terminal cyanate group provide a convenient approach for synthesizing polymers with a variety of distinct functional groups at R and ω chain ends. In the process, the capacity to label glycopolymers or otherwise conjugate them to proteins or other molecules is greatly enhanced.

Mono- and disaccharide-containing glycopolymers were synthesized by cyanoxyl-mediated polymerization of acrylamide with acrylate-derivatized mono- and disaccharides. We demonstrate that a glycopolymer bearing pendant, fully sulfated lactose units effectively replaces heparin and heparan sulfate as a molecular chaperone for fibroblast growth factor-2 (FGF-2). Specifically, a compound was identified that protects FGF-2 from proteolytic, acid, and heat-induced degradation, while selectively promoting growth factor and receptor dimerization. Significantly, the capacity of this heparin-mimic to promote an FGF-2 specific proliferative cell response was confirmed and suggests potential applications for this compound and related derivatives in areas related to therapeutic angiogenesis.

Eight-arm poly(ethylene oxide) (PEO) stars were prepared by the core-first method with a newly designed octahydroxylated precursor. This compound was readily obtained in two steps from commercially available tert-butylcalix [8]arene. The choice of the proper solvent of polymerization proved crucial to obtain PEO star materials with a narrow distribution of molar masses. For instance, the use of dimethyl sulfoxide (DMSO) resulted in PEO samples of rather large polydispersities (PDI: 1.3-1.5). In this solvent, the calixarene-based precursor was only sparingly soluble, and an attempt to metalate its eight hydroxyl groups produced insoluble alkoxides. In addition, the presence of a side population of low-molar-mass species attributable to linear chains was detected because of the chain transfer of propagating alkoxides to DMSO. Polymerization experiments carried out in tetrahydrofuran (THF) as solvent afforded better control over the molar masses and PDIs. This was related to the better solubility of the octafunctional calixarene-based precursor in THF and to the small tendency of the alkoxides formed to aggregate in that solvent. Under such conditions, all eight hydroxyl functions efficiently initiated the polymerization of ethylene oxide. In this way, well-defined PEO stars (PDI Ͻ 1.2) of tunable molar masses incorporating a calixarene-based core could be obtained, as it was supported by the characterization of the samples by size exclusion chromatography, NMR, and viscometry.