Fatal Chimeras: Impaired DNA-methylation maintenance during early embryonic development may cause imprinting-related diseases. Lorthongpanich et al. (p. 1110 ) have devised a sensitive assay to probe multiple imprinted gene loci for their DNA-methylation state at the single-cell level. Blastomeres with defective imprinting showed complex, epigenetic chimeras developed with fatal defects. Pronuclear transfer restored normal mouse development, offering a therapeutic strategy to overcome epigenetic defects caused by maternal insufficiencies.

The authors present microfluidic logic gates based on two-phase flows at low Reynold’s number. The presence and the absence of a dispersed phase liquid (slug) in a continuous phase liquid represent 1 and 0, respectively. The working principle of these devices is based on the change in hydrodynamic resistance for a channel containing droplets. Logical operations including AND, OR, and NOT are demonstrated, and may pave the way for microfludic system automation and computation.

We developed a novel method to increase the sensitivity of standard enzyme-linked immunosorbent assay (ELISA) using a multiplexed electrokinetic concentration chip. The poly(dimethylsiloxane) (PDMS) molecular concentrator(1) was used to trap and collect charged fluorescent product of target-bound enzyme turnover reaction of ELISA that occurred in a standard 96 well plate. Detection sensitivities of both prostate specific antigen (PSA) and CA 19-9 (a human pancreatic and gastrointestinal cancer marker) ELISAs in serum are enhanced ∼100 fold with a low CV of <17%. We also integrated this method with an on-chip bead-based ELISA that lends itself toward a fully automated on-chip diagnostic device. Detection sensitivity of microfluidic bead-based CA 19-9 ELISA in serum is enhanced ∼65 fold compared to the results without the electrokinetic accumulation step. This chip can be directly applied to enhance the readout sensitivity of a wide range of existing ELISA kits at concentrations below the current detection limit.

A massively parallel nanofluidic concentration device array for multiplexed and high-throughput biomolecule detection is demonstrated. By optimizing the microchannel/nanojunction design and channel conductivity, an array of up to 128 nanofluidic concentration devices were fabricated. Operation of the entire array requires only one inlet and one outlet reservoir, with the application of a single operational voltage bias across them. Concentration efficiencies of the devices were found to be uniform within the array, within 5% error. Alternatively, concentration speed in each channel can be individually tuned by controlling the length of the inlet microchannel and thus controlling the flow rate based on change of the tangential electric field. This allows immuno-binding reactions at different concentration ranges to be performed in parallel. Using multiplexed, successive-concentration enhanced detection in the device, we have shown that the dynamic range and reliability of the immunoassay can be significantly increased.