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Biomedical subjects

Guido W M Vandermeulen

Publications and source records attributed to Guido W M Vandermeulen.

6 recordsLinked to original sources
PubMed2006

Photocontrolled living polymerizations.

Living polymerizations involve the creation of polymer chains without significant irreversible chain transfer or chain termination. Such processes are widely used to access well-defined macromolecular materials with controlled architectures, such as block and star polymers. Although this concept was first realized for anionic polymerizations in the 1950s, many key recent advances have been made, most notably in the area of radical polymerization. Here, we report a living photopolymerization that involves photoexcited monomers. Exposure of metal-containing ferrocenophane monomers to Pyrex-filtered light from a mercury lamp (lambda>310 nm) or to bright sunlight in the presence of an anionic initiator leads to living polymerizations, in which the conversion and molecular weight of the resulting polymer can be controlled by the irradiation time. Photoirradiation selectively weakens the iron-cyclopentadienyl bond in the monomer, allowing the use of moderately basic and highly functional-group-tolerant initiators. The polymerization proceeds through attack of the initiator and propagating anion on the iron atom of the photoexcited monomer and, remarkably, the polymerization rate decreases with increasing temperature. Block copolymer formation is possible when the light source is alternately switched on and off in between sequential addition of different monomers, providing unprecedented, photocontrolled access to new types of functional polymers.

Journal Article↗
PubMed2006

Metallopolymer-peptide conjugates: synthesis and self-assembly of polyferrocenylsilane graft and block copolymers containing a beta-sheet forming Gly-Ala-Gly-Ala tetrapeptide segment.

We describe the synthesis and self-assembly of two beta-sheet forming metallopolymer-peptide conjugates. The ability of the oligotetrapeptide sequence Gly-Ala-Gly-Ala (GAGA) to form antiparallel beta-sheets was retained in PFS-b-AGAG (PFS = polyferrocenylsilane) and PFS-g-AGAG conjugates with block and graft architectures, respectively. In the solid state, DSC experiments suggest a phase separation between the peptide and PFS domains. In toluene, PFS-b-AGAG interestingly forms a fibrous network which consists of a core containing the self-assembled antiparallel beta-sheet peptide and a corona of organometallic PFS. The self-assembly of the peptide into antiparallel beta-sheets is the driving force for the fiber formation, whereas PFS prevents uncontrolled lateral aggregation of the fibers. The use of an oligopeptide to self-assemble an otherwise random coiled organometallic polymer may be a useful strategy to enhance nanostructure formation. In the cases described here, the conjugates may be used to create nanopatterned ceramics, and the redox properties of the resulting supramolecular aggregates are of significant interest.

Molecular Conformation↗
PubMed2005

Peptide mediated formation of hierarchically organized solution and solid state polymer nanostructures.

Biologically-inspired peptide sequences have been explored as auxiliaries to mediate self-assembly of synthetic macromolecules into hierarchically organized solution and solid state nanostructures. Peptide sequences inspired by the coiled coil motif and "switch" peptides, which can adopt both amphiphilic alpha-helical and beta-strand conformations, were conjugated to poly(ethylene glycol) (PEG). The solution and solid state self-assembly of these materials was investigated using a variety of spectroscopic, scattering and microscopic techniques. These experiments revealed that the folding and organization properties of the peptide sequences are retained upon conjugation of PEG and that they provide the driving force for the formation of the different nanoscale structures which were observed. The possibility of using defined peptide sequences to direct structure formation of synthetic polymers together with the potential of peptide sequences to induce a specific biological response offers interesting prospects for the development of novel self-assembled and biologically active materials.

Amino Acid Sequence↗
PubMed2004

Peptide/protein hybrid materials: enhanced control of structure and improved performance through conjugation of biological and synthetic polymers.

The conjugation of peptides/proteins and synthetic polymers is a useful strategy to overcome some of the limitations related to the use of the individual components. This review will highlight two aspects: enhanced structural control at the nanometer level and improved performance, in particular with respect to biomedical applications. In the former case, peptide sequences are mainly used to mediate self-assembly of synthetic polymers. In the latter case, conjugation of an appropriate synthetic polymer to a pharmaceutically active peptide/protein can, for example, prevent premature enzymatic degradation and enhance blood circulation times, which is therapeutically advantageous.

Amino Acid Sequence↗
PubMedDate not supplied

Polyphenylene dendrimers as scaffolds for shape-persistent multiple peptide conjugates.

The present work describes synthetic concepts for the coupling of peptides to polyphenylene dendrimers (PPDs). Novel functionalized cyclopentadienones have been synthesized whose Diels-Alder cycloaddition with various core molecules leads to polyphenylene dendrimers possessing (protected) amino or carboxyl groups. In addition, the resulting functionalized molecules exhibit the characteristic shape-persistence and monodispersity of PPDs. Their functions have been used for the attachment of polylysine to the dendritic scaffold. Three different methods for the decoration of dendrimers with polypeptides are presented. First, polylysine segments are grafted from the surface of the dendrimers employing alpha-amino acid N-carboxyanhydride (NCA) polymerization. Second, the C-terminal carboxyl groups of protected polypeptides are activated and then coupled to the amino groups on the surface of the PPD. Finally, cysteine terminated, unprotected peptide sequences are attached to polyphenylene dendrimers utilizing the addition of the sulfhydryl group of a cysteine to the maleimide functions on the dendrimer surface. Moreover, Diels-Alder cycloaddition of suitably functionalized cyclopentadienons to a desymmetized core molecule allows the design of a dendritic scaffold with a specific number of different anchor groups on its periphery. These approaches are important for the tailoring of new, shape-persistent, polyfunctional multiple antigen conjugates.

Antigens↗