Unique properties exist in nanofluidic channels. In this paper, we report a new phenomenon, ion enrichment/depletion, associated with nanochannel structures. As a voltage is applied across a nanochannel, ions are rapidly enriched at one end and depleted at the other end of the nanochannel. The degree of this enrichment and depletion is directly related to the extent of double-layer overlap. A simple model is presented to qualitatively interpret this phenomenon.

Capillary electrophoresis and related techniques on microchips have made great strides in recent years. This review concentrates on progress in capillary zone electrophoresis, but also covers other capillary techniques such as isoelectric focusing, isotachophoresis, free flow electrophoresis, and micellar electrokinetic chromatography. The material and technologies used to prepare microchips, microchip designs, channel geometries, sample manipulation and derivatization, detection, and applications of capillary electrophoresis to microchips are discussed. The progress in separation of nucleic acids and proteins is particularly emphasized.

DNA sequencing separations have been performed in microfabricated electrophoresis channels with the goal of determining whether high-quality sequencing is feasible with these microdevices. The separation matrix, separation temperature, channel length and depth, injector size, and injection parameters were optimized. DNA fragment sizing separations demonstrated that 50-micron-deep channels provide the best sensitivity for our detection configuration. One-color sequencing separations of single-stranded M13mp18 DNA on 3% linear polyacrylamide (LPA) were used to optimize the twin-T injector size, injection conditions, and temperature. The best one-color separations were observed with a 250-micron twin-T injector, an injection time of 60 s, and a temperature of 35 degrees C. The first 500 bases appeared in 9.2 min with a resolution of > 0.5, and the separation extended to 700 bases. The best four-color sequencing separations were performed using 4% LPA, a temperature of 40 degrees C, and a 100-micron twin-T injector. These four-color runs were complete in only 20 min, could be automatically base-called using BaseFinder to over 600 bp after the primer, and were 99.4% accurate to 500 bp. These results significantly advance the quality of microchip-based electrophoretic sequencing and indicate the feasibility of performing high-speed genomic sequencing with microfabricated electrophoretic devices.

Electroosmotic pumping is receiving increasing attention in recent years owing to the rapid development in micro total analytical systems. Compared with other micropumps, electroosmotic pumps (EOPs) offer a number of advantages such as creation of constant pulse-free flows and elimination of moving parts. The flow rates and pumping pressures of EOPs matches well with micro analysis systems. The common materials and fabrication technologies make it readily integrateable with lab-on-a-chip devices. This paper reviews the recent progress on EOP fabrications and applications in order to promote the awareness of EOPs to researchers interested in using micro-and nano-fluidic devices. The pros and cons of EOPs are also discussed, which helps these researchers in designing and constructing their micro platforms.

The search for a cell-supporting scaffold with controlled topography and surface chemistry is a constant topic within tissue engineering. Here we have employed M13 phages, which are genetically modifiable biological nanofibers (~880 nm long and ~6.6 nm wide) non-toxic to human beings, to form films for supporting the growth of mesencymal stem cells (MSCs). Films were built from nearly parallel phage bundles separated by grooves. The bundles can guide the elongation and alignment of MSCs along themselves. Phage with peptides displayed on the surface exhibited different control over the fine morphologies and differentiation of the MSCs. When an osteogenic peptide was displayed on the surface of phage, the proliferation and differentiation of MSCs into osteoblasts was significantly accelerated. The use of the grooved phage films allows us to control the proliferation and differentiation of MSCs by simply controlling the concentrations of phages as well as the peptides displayed on the surface of the phages. This work will advance our understanding on the interaction between stem cells and proteins.