Multiplexed Detection of Molecular Interactions with DNA Origami Engineered Cells in 3D Collagen Matrices.

The interactions of cells with signaling molecules present in their local microenvironment maintain cell proliferation, differentiation, and spatial organization and mediate progression of diseases such as metabolic disorders and cancer. Real-time monitoring of the interactions between cells and their extracellular ligands in a three-dimensional (3D) microenvironment can inform detection and understanding of cell processes and the development of effective therapeutic agents. DNA origami technology allows for the design and fabrication of biocompatible and 3D functional nanodevices via molecular self-assembly for various applications including molecular sensing. Here, we report a robust method to monitor live cell interactions with molecules in their surrounding environment in a 3D tissue model using a microfluidic device. We used a DNA origami cell sensing platform (CSP) to detect two specific nucleic acid sequences on the membrane of B cells and dendritic cells. We further demonstrated real-time detection of biomolecules with the DNA sensing platform on the surface of dendritic cells in a 3D microfluidic tissue model. Our results establish the integration of live cells with membranes engineered with DNA nanodevices into microfluidic chips as a highly capable biosensor approach to investigate subcellular interactions in physiologically relevant 3D environments under controlled biomolecular transport.

Low cost and massively parallel force spectroscopy with fluid loading on a chip.

Current approaches for single molecule force spectroscopy are typically constrained by low throughput and high instrumentation cost. Herein, a low-cost, high throughput technique is demonstrated using microfluidics for multiplexed mechanical manipulation of up to ~4000 individual molecules via molecular fluid loading on-a-chip (FLO-Chip). The FLO-Chip consists of serially connected microchannels with varying width, allowing for simultaneous testing at multiple loading rates. Molecular force measurements are demonstrated by dissociating Biotin-Streptavidin and Digoxigenin-AntiDigoxigenin interactions along with unzipping of double stranded DNA of varying sequence under different dynamic loading rates and solution conditions. Rupture force results under varying loading rates and solution conditions are in good agreement with prior studies, verifying a versatile approach for single molecule biophysics and molecular mechanobiology. FLO-Chip enables straightforward, rapid, low-cost, and portable mechanical testing of single molecules that can be implemented on a wide range of microscopes to broaden access and may enable new applications of molecular force spectroscopy.

Injectable, dispersible polysulfone-polysulfone core-shell particles for optical oxygen sensing.

Injectable sensors can significantly improve the volume of critical biomedical information emerging from the human body in response to injury or disease. Optical oxygen sensors with rapid response times can be achieved by incorporating oxygen-sensitive luminescent molecules within polymeric matrices with suitably high surface area to volume ratios. In this work, electrospraying utilizes these advances to produce conveniently injectable, oxygen sensing particles made up of a core-shell polysulfone-polysulfone structure containing a phosphorescent oxygen-sensitive palladium porphyrin species within the core. Particle morphology is highly dependent on solvent identity and electrospraying parameters; DMF offers the best potential for the creation of uniform, sub-micron particles. Total internal reflection fluorescence (TIRF) microscopy confirms the existence of both core-shell structure and oxygen sensitivity. The dissolved oxygen response time is rapid (<0.30 s), ideal for continuous real-time monitoring of oxygen concentration. The incorporation of Pluronic F-127 surfactant enables efficient dispersion; selection of an appropriate electrospraying solvent (DMF) yields particles readily injected even through a <100 µm diameter needle.

Engineering Cell Surface Function with DNA Origami.

A specific and reversible method is reported to engineer cell-membrane function by embedding DNA-origami nanodevices onto the cell surface. Robust membrane functionalization across epithelial, mesenchymal, and nonadherent immune cells is achieved with DNA nanoplatforms that enable functions including the construction of higher-order DNA assemblies at the cell surface and programed cell-cell adhesion between homotypic and heterotypic cells via sequence-specific DNA hybridization. It is anticipated that integration of DNA-origami nanodevices can transform the cell membrane into an engineered material that can mimic, manipulate, and measure biophysical and biochemical function within the plasma membrane of living cells.