Quasielastic light scattering was used to investigate the size and shape of sodium dodecyl benzene sulfonate (SDBS) micelles in aqueous solutions. Measurements were made as a function of temperature and NaC1 and SDBS concentrations. Light scattering data indicate that the micelles are spherocylinders with a semiminor axis of 22 A. The length of the micelles increases strongly with salt concentration and decreases with temperature. The minimum micelle has an aggregation number of n o = 28 and a hydrodynamic radius of R = 22 A. Diffusion coeificient and intensity data were analyzed using a thermodynamic theory of micellar aggregation and a model based on DLVO theory of interactions.

Ventilator-associated pneumonia (VAP) is a serious and costly clinical problem affecting pediatrics today. This devicerelated infection is thought to be directly linked to the colonization of the endotracheal tube (ETT) during long-term mechanical ventilation. Because of unspecific radiographic and clinical signs, VAP is especially difficult to diagnose in the pediatric population. Treatment with antibiotics is often ineffective, and VAP is associated with high morbidity, mortality, and medical costs. The use of nanomodified coatings on ETT may provide an effective strategy to prevent biofilm formation and ETT colonization. Nanoparticles such as selenium and iron oxide have been shown to penetrate into the biofilm reaching the protected cells antibiotics often miss. Moreover, nanoetching techniques can modify the topography of the ETT surface interfering with bacterial adhesion. This review seeks to examine the antimicrobial properties of both nanoparticles and nanomodified surfaces and to characterize their effectiveness at reducing bacterial colonization on ETT. (Pediatr Res 67: 500-504, 2010) N anotechnology is the control of matter at the atomic, molecular, and supramolecular scale. Nanomaterials, or materials (such as particles, fibers, tubes, grains, etc.) with at least one dimension in the range of 1-100 nm, can be metals, ceramics, polymers, or composites thereof. These materials exhibit unique properties because of their size and significantly greater surface areas, which can influence numerous properties including material conductivity, magnetic properties, surface energy, mechanical properties, catalytic properties, etc.An ongoing area of this research includes the interaction between synthetic nanoscale materials and living tissues. Micro-and nanoscale building blocks form the foundation for cells and tissues within the human body. It is thought that the difference in the activity of some cells on nanomodified surfaces is because of the ability of these materials to mimic the natural dimensions of constituents of biological tissues. Another important factor in this interaction is the unique surface energetics of nanomaterials because of their significantly greater surface areas compared with conventional, micron-structured materials. Such changes in surface energy undoubtedly influence initial protein interactions that are important for mediating bacteria and nonbacteria cell adhesion. Specifically, one of the first steps within the process of cell adhesion is the association of proteins adsorbed on implant surfaces to cell membrane receptors. The large surface to volume ratio characteristic of nanomaterials has been shown to affect this association to inhibit bacteria attachment and promote nonbacterial cell (such as osteoblasts, smooth muscle cells, endothelial cells, chondrocytes, etc.) adhesion (1). The type, concentration, conformation, and bioactivity of proteins adsorbed onto a material depend on its topographical (roughness), chemical, physical (charge and hydrophilicity), and mecha...

No abstract

Monodisperse populations of microspheres are desirable for a variety of research and industrial applications, but many desirable sizes and materials can be difficult to synthesize and have limited commercial availability. In this paper, we present an effective, straightforward, and low cost method for sorting polydisperse microspheres into many separate monodisperse samples. The basic approach is to use velocity sedimentation through a density gradient in a long vertical column, followed by carefully targeted extraction. We demonstrate this technique by reducing the coefficient of variation of melamine microspheres from 13% to 1%–4% and glass microspheres from 35% to 3%–8%. This simple and inexpensive method can be used to sort microspheres of many sizes and materials, and is easily scalable, opening the possibility of cheap, monodisperse microspheres.