Microscopy and optical manipulation of dendrimer-built vesicles

Abstract

A fifth-generation poly(propylene imine) dendrimer decorated with palmitoyl-and azobenzene-containing alkyl groups forms giant vesicles in aqueous solutions with diameters from 50 nm up to 20 µm and a multilaminar onion-like structure. Dense and ordered arrangement of the azobenzene chromophores in the bilayer structure leads to fluorescence with λ max = 600 nm. The fluorescence intensity can be increased by irradiation with blue light, and at low pH a distinctive blue shift of the spectrum is observed. With the aid of a single-beam optical tweezers it is possible to trap vesicles and direct them in a billiard-like fashion against each other using forces in the range of several pN. In collision experiments, the vesicles behave like hard spheres, and merging is not observed.

Precision host–guest chemistry of polyphenylene dendrimers

“…FDMS: m/z 726 (65% 1), 708 (100% 2), [M + ]; calc. : 727.11 (1), 709.09 (2). The mixture was utilized for further synthesis without purification.…”

“…2,5-Di(methylcarboxy)-3,4-bis(4-triisopropylsilylethynylphenyl)cyclopentadienone (2). The product mixture of the antecedent step (1) (6.9 g) was added at room temperature to acetic anhydride (15 ml) containing concentrated sulfuric acid (3 drops).…”

“…The properties of dendrimers to host a number of guest molecules have intensified recent research efforts in their binding and function. In particular, it has been shown that a dendritic shell generates a unique microenvironment within its iteratively branched architecture and influences the optical properties, [1][2][3] redox chemistry, [4][5][6][7] catalysis, [8][9][10][11][12] and molecular recognition [13][14][15] of the guests. Perhaps the earliest and most studied use of dendrimers as supramolecular hosts was for the solubilization of chromophores in unusual environments by dendritic encapsulation of the chromophores.…”