Biomedical subjects

Albena Ivanisevic

Publications and source records attributed to Albena Ivanisevic.

3 recordsLinked to original sources

PubMed2005

Templates for DNA-templated Fe3O4 nanoparticles.

Two different strategies are reported that result in the site-specific placement of long DNA molecules, templated with Fe(3)O(4) nanoparticles, on SiO(x) surfaces. The strategies combine solution templating of inorganic nanoparticles onto biomolecules, molecular combing, the layer-by-layer method, and dip-pen nanolithography (DPN). In one methodology, the first step is to place and stretch DNA molecules via a DPN template containing features of poly(allylamine hydrochloride) (PAH). In the second step the elongated DNA is templated with Fe(3)O(4) nanoparticles allowing them to assemble onto the DNA molecules based on electrostatic interactions. In the second methodology, DPN templates composed of PSS patterns are used to comb in a site-specific manner DNA molecules that have been pre-tempated in solution with the Fe(3)O(4) nanoparticles. The templates generated by the two methods can serve as building blocks for the fabrication of future higher order assemblies.

Coated Materials, Biocompatible↗

PubMed2004

Encapsulated cells: an atomic force microscopy study.

Two types of cells--human platelets and spore cells--were encapsulated in polymer shells by adsorbing polyanions and polycations in a stepwise fashion. The encapsulated cells were attached to gold and silicon surfaces and their morphological and adhesion properties were studied in air using tapping mode atomic force microscopy (AFM). The roughness of the encapsulated cells increased upon the addition of a new polymer layer. The increase in roughness can be attributed to the formation of a shell around the cells, which is stabilized by electrostatic interactions, as well as to the drying effects associated with the immobilization and dehydration of the cells. Trigger mode was used to perform the force imaging and map out the adhesion characteristics of the cells. Systematic "maps" of the adhesion properties of the encapsulated cells to clean and amine terminated AFM tips were collected. The adhesion force data for the different tips and encapsulated cells showed dependence not only on the number and thickness of the polymer layers, but also on the interactions between these layers. The encapsulated cells' morphology and roughness characteristics remained intact over a substantial storage period. This stability and adhesion properties make them suitable building blocks for the design and construction of biomimetic templates where AFM is used as the primary tool to do the fabrication.

Adhesiveness↗

PubMed2002

Site-directed exchange studies with combinatorial libraries of nanostructures.

We describe a new combinatorial method for studying the exchange between solution adsorbates and nanoscale features within libraries generated via dip-pen nanolithography. Four different compounds, 1-octadecanethiol, 16-mercaptohexadecanoic acid, ferrocene (11-mercaptoundecyl), and ferrocene (11-mercapto-1-oxoundecyl), are studied on amorphous and single-crystal gold substrates. This series of adsorbates allows us to compare the exchange properties of patterns of nanoscale features as a function of composition, feature size, and type of underlying substrate. Moreover, these properties can be compared and contrasted with bulk SAM properties. The novel strategy provides not only a method for initiating site-specific exchange processes but also a way of extracting kinetic information about the rate of such processes in situ.

Combinatorial Chemistry Techniques↗