Biomedical subjects

Jason D Feick

Publications and source records attributed to Jason D Feick.

3 recordsLinked to original sources

PubMed2005

Nanoscale functionalization and site-specific assembly of colloids by particle lithography.

Numerous studies have demonstrated the bottom-up assembly of complex structures such as colloidal crystals, close-packed aggregates, and even rings and tetramers. In this paper we produce a simple localized and nanoscale charge distribution on the surfaces of individual colloidal microspheres using our technique of "particle lithography". In this technique parts of the microspheres are masked off, while polyelectrolytes (or other molecules) cover the remaining portions of the microspheres. The effectiveness of this process is demonstrated by the accurate and reproducible production of colloidal heterodoublets composed of oppositely charged microspheres. These "colloidal molecules" have the potential for significantly higher information content than previous attempts in the literature. The particle lithography technique is advantageous because it is not limited by the resolution of photolithography or by functionalizing chemistries, and the technique opens the door for complex site-specific functionalization of particles.

Journal Article↗

PubMed2004

Altering surface charge nonuniformity on individual colloidal particles.

Charge nonuniformity (sigmazeta) was altered on individual polystyrene latex particles and measured using the novel experimental technique of rotational electrophoresis. It has recently been shown that unaltered sulfated latices often have significant charge nonuniformity (sigmazeta = 100 mV) on individual particles. Here it is shown that anionic polyelectrolytes and surfactants reduce the native charge nonuniformity on negatively charged particles by 80% (sigmazeta = 20 mV), even while leaving the average surface charge density almost unchanged. Reduction of charge uniformity occurs as large domains of nonuniformity are minimized, giving a more random distribution of charge on individual particle surfaces. Targeted reduction of charge nonuniformity opens new opportunities for the dispersion of nanoparticles and the oriented assembly of particles.

Journal Article↗

PubMed2003

Oriented adhesion of Escherichia coli to polystyrene particles.

The adhesion of nonflagellated Escherichia coli strain K-12 to polystyrene (PS) latex spheres or glass capillaries has been observed by using several techniques. Attention was focused on the orientation of the rod-shaped bacteria as they adhered to the surfaces in 100 mM phosphate-buffered saline. Data show that PS particles adhered to the ends of the bacteria more than 90% of the time. Moreover, the PS particles adhered to one end only, never to both. Similarly, for experiments with bacteria adhering to glass, the bacteria adhered on their ends. In order to determine whether the end of a bacterium had a different charge density from that of the middle, rotational electrophoresis experiments were used. These experiments indicated no measurable charge nonuniformity. In order to examine how strongly adhered the bacteria were to the PS particles, differential electrophoresis was used. Almost always, bacteria were found to be irreversibly adhered to the PS spheres. The cause of the oriented adhesion is not likely due to surface lipopolysaccharides (LPS), since the three strains of K-12 that were used, each having a different length of LPS, showed similar behavior. The results are discussed in terms of bacterial cell polarity. The data indicate that nanodomains on the bacterial ends are important for adhesion and that the time scale for irreversible adhesion is short.

Bacterial Adhesion↗