Stephanie Hornig

Functional Polymers Based on Dextran

Dextran, comprising a family of neutral polysaccharides consisting of an α-(1 → 6) linked d-glucose main chain with varying proportions of linkages and branches, depending on the bacteria used, is an interesting starting material for chemical modification reactions for the design of new functional polymers with promising properties. The review summarises recent results on structure characterisation of dextran including some comments on biosynthesis of this important class of biopolymers. Applications of dextran are discussed as well. Chemical modification reactions of dextran are increasingly studied for the structure and hence property design. The review highlights recent progress in esterification of dextran, both inorganic and organic polysaccharide esters, etherification reactions towards ionic and non-ionic ethers, and the huge variety of different conversions mainly developed for the binding of drugs. It summarises recent developments in the application of dextran derivatives with a focus on the chemical structures behind these materials such as prodrugs, bioactivity of inorganic dextran esters, heparin sulfate mimics, hydrogels, nanoparticles and self assembly structures for surface modification.

Synthetic polymeric nanoparticles by nanoprecipitation

Nanoprecipitation is applied for the first time as a general concept for manufacturing nanoparticles of versatile hydrophobic polymer classes. As a result, polymer molecules self-assemble into nanospheres or irregularly shaped nanoparticles during the transition from the dissolved state to the solid state while using different solvents and methods for the conversion.

Efficient Approach To Design Stable Water-Dispersible Nanoparticles of Hydrophobic Cellulose Esters

Commercially prepared cellulose acetate, cellulose acetate propionate, -butyrate, and -phthalate as well as cellulose acetates prepared in the laboratory scale with varying degree of substitution (DS) self-assemble into regular nanoparticles, ranging in size from 86 to 368 nm, by using two different techniques of nanoprecipitation. Dialysis of polymers dissolved in N,N-dimethylacetamide results in the formation of regular nanospheres whereas the preparation in acetone by successive adding of water leads to bean-shaped particles in the nanoscale. One criterion for nanoprecipitation is the existence of dilute polymer solutions. Furthermore, the formation of nanoparticles strongly depends on DS and distribution of the substituents. Concerning this issue, quantitative (13)C NMR spectroscopy was applied for detailed structure characterization of selected cellulose acetates. The stability of the nanoparticle suspensions in the physiological pH range was observed by zeta potential measurements.

Biocompatible fluorescent nanoparticles for pH-sensoring

Dialysis of a mixture of fluorescein and sulforhodamine B marked dextran derivatives yields biocompatible and tuneable nanosensors that can be used for ratiometric pH measurements.