Dense-shell glycodendrimers: UV/Vis and electron paramagnetic resonance study of metal ion complexation

Abstract

The development of dendritic metal ion carrier systems for use in a biological environment is a challenging task as the carrier system must possess multiple features (e.g. a protective shell for metal decomplexation, targeting functions, metal-intradendrimer complexes, etc.) to substitute for the function of metal proteins in processes such as copper metabolism. Thus, Cu(II) complexation by a series of poly(propyleneimine) glycodendrimers ranging up to the fifth generation that have either a dense maltose or maltotriose shell was investigated by UV/Vis spectroscopy and electron paramagnetic resonance (EPR). As a necessary step towards potential biological application, we elucidated the complexation capacity, location of the Cu(II)-dendrimer complexes and the Cu(II) coordination sphere in the dendritic environment. A generation-dependent Cu(II) complexation was found. Furthermore, analysis of the EPR spectra revealed that internal and external Cu(II) coordination and the symmetry (axial and rhombic) of the generated complexes depend on the oligosaccharide shell, dendrimer generation and the relative concentrations of Cu(II) and the dendrimers. Both axial and rhombic symmetries are generation dependent, but also distort with increasing generation number. External coordination of Cu(II) is supported by sugar groups and water molecules. Finally, a third-generation dendrimer with a maltose shell was used to explore the general complexation behaviour of the dendritic poly(propyleneimine) scaffold towards different metal ions [Cu(II), Ag(I), VO(IV), Ni(II), Eu(III) and UO 2 (VI)].

Differentiating Prion Strains Using Dendrimers

“…[20,37] PPIg4 and PAMAMg5 have a cationic surface charge, whilst the surface charge of 0.5mPPIg5 is also cationic, but lower in comparison to PPIg5. [19,20] In contrast to this, a neutral surface charge is present for the dense shell glycodendrimer mPPIg5.…”

Influence of Surface Functionality of Poly(propylene imine) Dendrimers on Protease Resistance and Propagation of the Scrapie Prion Protein

“…For this purpose, 3 rd to 5 th generation PPI glycodendrimers with a dense maltose shell presenting a multiple H-bonding active glycodendrimer surface as described previously 49 were employed. The molecular structure of the glycodendrimers, presented in Figure 1, is characterized by a dense oligosaccharide shell, in which the formerly peripheral amino groups preferentially possess two chemically coupled maltose 49 or maltotriose 51 units. This specific structural feature in the outer sphere of the glycodendrimers, introduces a neutral charge density in the former cationic PPI dendrimers as determined by polyelectrolyte titration experiments 49 .…”

Multi-Technique Characterization of Poly-L-lysine Dendrigrafts-Cu(II) Complexes for Biocatalysis

“…The magnetic parameters extracted from the simulation were then compared with equivalent parameters found in the literature . This allowed us to assign each spectral component to a copper coordination and identify the structure and complexing sites of the DGLs.…”

“…On the other side, the EPR technique has been found to be very useful to characterize the dendrimer interacting ability and flexibility by using Cu(II) ions as probes . In these previous studies, it was verified that Cu(II) complexation is particularly informative about the internal structure of the dendrimers in solution, and to differentiate the internal/external interacting sites in respect to their availability for ion complexation.…”