Programmable Aggregation of Artificial Cells with DNA Signals.

Cell aggregation is a complex behavior that is closely related to the viability, differentiation, and migration of cells. An effort to create synthetic analogs could lead to considerable advances in cell physiology and biophysics. Rendering and modulating such a dynamic artificial cell system require mechanisms for receiving, transducing, and transmitting intercellular signals, yet effective tools are limited at present. Here we construct synthetic cells from engineered lipids and show their programmable aggregation behaviors using DNA oligonucleotides as signaling molecules. The artificial cells have transmembrane channels made of DNA origami that are used to recognize and process intercellular signals. We demonstrate that multiple small vesicles aggregate onto a giant vesicle after a transduction of external DNA signals by an intracellular enzyme and that the small vesicles dissociate when receiving "release" signals. This work provides new possibilities for building synthetic protocells capable of chemical communication and coordination.

Mechanistic Understanding of Surface Migration Dynamics with DNA Walkers.

Dynamic DNA walkers can move cargoes on a surface through various mechanisms including enzymatic reactions and strand displacement. While they have demonstrated high processivity and speed, their motion dynamics are not well understood. Here, we utilize an enzyme-powered DNA walker as a model system and adopt a random walk model to provide new insight into migration dynamics. Four distinct migration modes (ballistic, Lévy, self-avoiding, and diffusive motions) are identified. Each mode shows unique step time and velocity distributions, which are related to mean-squared displacement (MSD) scaling. Experimental results are in excellent agreement with the theoretical predictions. With a better understanding of the dynamics, we performed a mechanistic study, elucidating the effects of cargo types and sizes, walker sequence designs, and environmental conditions. Finally, this study provides a set of design principles for tuning the behaviors of DNA walkers. The DNA walkers from this work could serve as a versatile platform for mathematical studies and open new opportunities for bioengineering.

Mimicking Chemotactic Cell Migration with DNA Programmable Synthetic Vesicles.

Chemotactic cell motility plays a critical role in many biological functions, such as immune response and embryogenesis. Constructing synthetic cell-mimicking systems, such as a dynamic protocell, likewise requires molecular mechanisms that respond to environmental stimuli and execute programmed motility behaviors. Although various molecular components were proposed to achieve diverse functions in synthetic protocells, chemotactic motility on surfaces has not been reported thus far. Here we show directional motility in synthetic lipid vesicles capable of chasing each other by programming DNA components. We demonstrate that the "follow" vesicle recognizes and migrates along the moving trajectory of the "lead" vesicle with an enhanced speed, thus mimicking natural chemotaxis in cell migration. This work provides new possibilities for building synthetic protocells with complex functions such as programmed morphogenesis and cooperative motion. With the vast library of dynamic DNA components, we envision that this platform will enable new discoveries in fundamental sciences and novel applications in biotechnology.

Highly sensitive covalently functionalized light-addressable potentiometric sensor for determination of biomarker.

A biomarker is related to the biological status of a living organism and shows great promise for the early prediction of a related disease. Herein we presented a novel structured light-addressable potentiometric sensor (LAPS) for the determination of a model biomarker, human immunoglobulin G (hIgG). In this system, the goat anti-human immunoglobulin G antibody was used as recognition element and covalently immobilized on the surface of light-addressable potentiometric sensor chip to capture human immunoglobulin G. Due to the light addressable capability of light-addressable potentiometric sensor, human immunoglobulin G dissolved in the supporting electrolyte solution can be detected by monitoring the potential shifts of the sensor. In order to produce a stable photocurrent, the laser diode controlled by field-programmable gate array was used as the light emitter to drive the light-addressable potentiometric sensor. A linear correlation between the potential shift response and the concentration of human immunoglobulin G was achieved and the corresponding regression equation was ΔV (V)=0.00714ChIgG (µg/mL)-0.0147 with a correlation coefficient of 0.9968 over a range 0-150 µg/mL. Moreover, the light-addressable potentiometric sensor system also showed acceptable stability and reproducibility. All the results demonstrated that the system was more applicable to detection of disease biomarkers with simple operation, multiple-sample format and might hold great promise in various environmental, food, and clinical applications.