Role of helicity in the nonenzymatic template-directed primer extension of DNA.

Complexing a DNA primer with an RNA template showed improved nonenzymatic template-directed primer extension, attributed to a shift in the DNA helicity from a B-type towards an A-type helix. A 2-fold (deoxyadenosine) and 4.5-fold (deoxycytidine) increase in conversion from initial DNA primer to a primer + 1 nucleotide product was observed.

Beta-cyclodextrin decorated nanostructured SERS substrates facilitate selective detection of endocrine disruptor chemicals.

We demonstrate the selective detection of endocrine disruptor chemicals (EDCs) from river water using surface enhanced Raman scattering (SERS). By means of nanosphere lithography, the SERS substrate was prepared via the initial deposition of a monolayer of silica nanospheres (with diameter of ∼330 nm) on a silicon substrate as the template. Subsequently, a 180 nm thick layer of silver followed by a 20 nm layer of gold was deposited. This surface was modified with mono-6-deoxy-6-((2-mercaptoethyl)amino)-beta-cyclodextrin (ß-CD) in order to produce a selective capture surface suitable for EDC capture and their detection by means of SERS. We show that EDC model compounds, including 3-amino-2-naphthoic acid (NAPH), potassium hydrogen phthalate (PHTH) and the EDC ß-estradiol (ESTR), were captured by the ß-CD decorated surface. This surface facilitated SERS detection with limits of detection of 3.0 µM (NAPH), 10 µM (PHTH) and 300 nM (ESTR), all 10-100 times lower than that without the surface modification with ß-CD. Individual and simultaneous detection of NAPH and PHTH from their mixture was achieved as evidenced using the bianalyte Raman technique.

Fabrication of self-supporting porous silicon membranes and tuning transport properties by surface functionalization.

This study presents a simple approach to perform selective mass transport through freestanding porous silicon (pSi) membranes. pSi membranes were fabricated by the electrochemical etching of silicon to produce membranes with controlled structure and pore sizes close to molecular dimensions (approximately 12 nm in diameter). While these membranes are capable of size-exclusion based separations, chemically specific filtration remains a great challenge especially in the biomedical field. Herein, we investigate the transport properties of chemically functionalized pSi membranes. The membranes were functionalized using silanes (heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane (PFDS) and N-(triethoxysilylpropyl)-o-polyethylene oxide urethane (PEGS) to give membranes hydrophobic (PFDS) and hydrophilic (PEGS) properties. The transport of probe dyes tris(2,2'-bipyridyl)dichlororuthenium(ii) hexahydrate (Rubpy) and Rose Bengal (RB) through these functionalized membranes was examined to determine the effect surface functionalization has on the selectivity and separation ability of pSi membranes. This study provides the basis for further investigation into more sophisticated surface functionalization and coupled with the biocompatibility of pSi will lead to new advances in membrane based bio-separations.

Recent developments in PDMS surface modification for microfluidic devices.

PDMS is enjoying continued and ever increasing popularity as the material of choice for microfluidic devices due to its low cost, ease of fabrication, oxygen permeability and optical transparency. However, PDMS's hydrophobicity and fast hydrophobic recovery after surface hydrophilization, attributed to its low glass transition temperature of less than -120 degrees C, negatively impacts on the performance of PDMS-based microfluidic device components. This issue has spawned a flurry of research to devise longer lasting surface modifications of PDMS, with particular emphasis on microfluidic applications. This review will present recent research on surface modifications of PDMS using techniques ranging from metal layer coatings and layer-by-layer depositions to dynamic surfactant treatments and the adsorption of amphipathic proteins. We will also discuss significant advances that have been made with a broad palette of gas-phase processing methods including plasma processing, sol-gel coatings and chemical vapor deposition. Finally, we will present examples of applications and future prospects of modified PDMS surfaces in microfluidics, in areas such as molecular separations, cell culture in microchannels and biomolecular detection via immunoassays.