Kelong Wang

An Autonomous and Controllable Light‐Driven DNA Walking Device

The development of nanotechnology has been largely inspired by the biological world. The complex, but well-organized, living system hosts an array of molecular-sized machines responsible for information processing, structure building and, sometimes, movement. We present here a novel light-powered DNA mechanical device, which is reminiscent of cellular protein motors in nature, especially those of green plants. This walking device, which is based on pyrene- assisted photolysis of disulfide bonds, is capable of autonomous locomotion, with light control of initiation, termination and velocity. Based on DNA sequence design and such physical conditions as temperature and ionic strength, this photon-fueled DNA walker exhibits the type of operational freedom and mechanical speed that may rival protein motors in the future.

Self-Assembly of a Bifunctional DNA Carrier for Drug Delivery

NIH; National Key Scientific Program of China[2011CB911000]; China National Grand Program on Key Infectious Disease[2009ZX10004-312]; China National Scientific Foundation of China[20805038, 20620130427]; National Basic Research Program of China[2007CB935603, 2010CB732402]

Photon-regulated DNA-enzymatic nanostructures by molecular assembly.

Future smart nanostructures will have to rely on molecular assembly for unique or advanced desired functions. For example, the evolved ribosome in nature is one example of functional self-assembly of nucleic acids and proteins employed in nature to perform specific tasks. Artificial self-assembled nanodevices have also been developed to mimic key biofunctions, and various nucleic acid- and protein-based functional nanoassemblies have been reported. However, functionally regulating these nanostructures is still a major challenge. Here we report a general approach to fine-tune the catalytic function of DNA-enzymatic nanosized assemblies by taking advantage of the trans-cis isomerization of azobenzene molecules. To the best of our knowledge, this is the first study to precisely modulate the structures and functions of an enzymatic assembly based on light-induced DNA scaffold switching. Via photocontrolled DNA conformational switching, the proximity of multiple enzyme catalytic centers can be adjusted, as well as the catalytic efficiency of cofactor-mediated DNAzymes. We expect that this approach will lead to the advancement of DNA-enzymatic functional nanostructures in future biomedical and analytical applications.

Open-Tubular Capillary Cell Affinity Chromatography: Single and Tandem Blood Cell Separation

In this paper, an open-tubular capillary cell affinity chromatography (OT-CAC) method to enrich and separate target cells is described. Open tubular capillaries coated with anti-CD4, anti-CD14, or anti-CD19 antibodies were used as affinity chromatography columns to separate target blood cells. Cells were eluted using either shear force or bubbles. Bubbles were used to elute the captured cells without diluting the captured cells appreciably, while maintaining viability (the viability of the recovered cells was 85.83 +/- 7.34%; the viability of the cells was 90.41 +/- 3.49% before separation). Several aspects of the OT-CAC method were studied, such as the affinity of one antibody between two different cell lines, the effect of shear force, and the recovery of captured cells. Single- and multicell type separations were demonstrated by isolating CD4+ cells with antiCD4 coated capillary and isolating CD4+ and CD19+ cells with two capillaries in tandem from blood samples. In the one cell type isolation test, an average of 87.7% of the recovered cells from antiCD4 capillary were lymphocytes and an average of 97.7% of those lymphocytes were CD4+ cells. In the original blood sample, only 14.2% of the leukocytes were CD4+ cells. Two capillary columns were also run in tandem, separating two blood cell types from a single sample with high purity. The use of different elution shear forces was demonstrated to selectively elute one cell type. This method is an inexpensive, rapid, and effective method to separate target cells from blood samples.

The effects of flow type on aptamer capture in differential mobility cytometry cell separations.

In this work, differential mobility cytometry (DMC) was used to monitor cell separation based on aptamer recognition for target cells. In this device, open-tubular capillaries coated with Sgc8 aptamers were used as affinity chromatography columns for separation. After cells were injected into the columns, oscillating flow was generated to allow for long-term cell adhesion studies. This process was monitored by optical microscopy, and differential imaging was used to analyze the cells as they adhered to the affinity surface. We investigated the capture time, capture efficiency, purity of target and control cells, as well as the reusability of the affinity columns. Capture time for both CCRF-CEM cells and Jurkat T cells was 0.4+/-0.2 s, which demonstrated the high separation affinity between aptamers and target cells. The capture efficiency for CCRF-CEM cells was 95% and purity was 99% in a cell mixture. With the advantage of both high cell capture efficiency and purity, DMC combined with aptamer-based separation emerges as a powerful tool for rare cell enrichment. In addition, aptamer-based DMC channels were found to be more robust than antibody based channels with respect to reuse of the separation device.

Differential Mobility Cytometry

A new cell analysis method, differential mobility cytometry (DMC), was developed to monitor cells spatially and temporally or to separate cells based on affinity interactions. DMC combines an oscillation system with open-tubular capillary cell affinity chromatography (OT-CAC), although any separation volume (capillaries, channels, etc.) can be used. This unique separation approach uses oscillating flow and differential imaging to analyze cells as they retard and adhere to an affinity surface. Three main factors of the oscillation system were studied: the pump speed, oscillation frequency, and cell velocity at different oscillation speeds. The optimized oscillation frequency and intensity were determined. Cell-surface interactions were used to estimate the number of bonds formed during cell capture. An average of 200 bonds (standard deviation of 150 bonds) were formed during cell capture. The variability was due to differences in cell-capture times (0.8 +/- 0.6 s). Cells expressing the target protein on the surface oscillated slower and were captured by the corresponding ligand on the capillary surface. Cells were detected by differential imaging of a charge-coupled device camera. DMC measurements were optimized with respect to the camera frame difference. Cells were observed to slow as they reached the surface and could be observed to sway in the oscillating flow as they were tethered to the surface by a capture antibody. With the advantage of high cell-capture efficiency and temporally monitoring cell adhesion by the differential mobility of cells, DMC has proven to be a useful tool in cell analysis for basic biological studies and biomedical research.

Rapid data analysis method for differential mobility cytometry

Differential mobility cytometry (DMC) has recently been established as a powerful method to capture cells and study adhesion processes. DMC uses an oscillation system and cell affinity chromatography to monitor cells as they adhere to a surface. In the past, differential images had to be created individually which limited the throughput of the method. A new method to create differential images is presented. The method involves the subtraction of short movies from each other to create a stack of differential images that can be easily analyzed. In the future, this method will make DMC more accessible and improve throughput.