DNA assemblies have been used to organize inorganic nanoparticles into 3D arrays, with emergent properties arising as a result of nanoparticle spacing and geometry. We report here the use of engineered protein crystals as an alternative approach to biologically mediated assembly of inorganic nanoparticles. The protein crystal's 13 nm diameter pores result in an 80% solvent content and display hexahistidine sequences on their interior. The hexahistidine sequence captures Au25(glutathione)∼17 (nitrilotriacetic acid)∼1 nanoclusters throughout a chemically crosslinked crystal via the coordination of Ni(ii) to both the cluster and the protein. Nanoparticle loading was validated by confocal microscopy and elemental analysis. The nanoparticles may be released from the crystal by exposure to EDTA, which chelates the Ni(ii) and breaks the specific protein/nanoparticle interaction. The integrity of the protein crystals after crosslinking and nanoparticle capture was confirmed by single crystal X-ray crystallography.

Paper-based microfluidics was initially developed for use in ultra-low-cost diagnostics powered passively by liquid wicking. However, there is significant untapped potential in using paper to internally guide porous microfluidic flows...

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Paper-based microfluidics have gained widespread attention for use as low-cost microfluidic diagnostic devices in low-resource settings. However, variability in fluid transport due to evaporation and lack of reproducibility with processing real-world samples limits their commercial potential and widespread adoption. We have developed a novel fabrication method to address these challenges. This approach, known as “Microfluidic Pressure in Paper” (μPiP), combines thin laminating polydimethylsiloxane (PDMS) membranes and precision laser-cut paper microfluidic structures to produce devices that are low-cost, scalable, and exhibit controllable and reproducible fluid flow dynamics similar to conventional microfluidic devices. We present a new μPiP DNA sample preparation and processing device that reduces the number of sample preparation steps and improves sensitivity of the quantitative polymerase chain reaction (qPCR) by electrophoretically separating and concentrating nucleic acids (NAs) continuously on paper. Our device was assembled using two different microfluidic paper channels: one with a larger pore (25 microns) size for bulk fluid transport and another with a smaller pore size (11 microns) for electrophoretic sample concentration. These two paper types were aligned and laminated within PDMS sheets, and integrated with adhesive copper tape electrodes. A solution containing a custom DNA sequence was introduced into the large pore size paper channel using a low-cost pressure system and a DC voltage was applied to the copper tape to electrophoretically deflect the solution containing NAs into the paper channel with the smaller pore size. Samples were collected from both DNA enriched and depleted channels and analyzed using qPCR. Our results demonstrate the ability to use these paper devices to process and concentrate nucleic acids. Our concentration device has the potential to reduce the number of sample preparation steps and to improve qPCR sensitivity, which has immediate applications in disease diagnostics, microbial contamination, and public health monitoring.

Microfluidic PCR is one of the most common and widely used sample preparation techniques. Most heating methods for microfluidic PCR are heated in one of two ways: (1) the reaction is pumped between different boundary-heating zones, or (2) stationary reaction chamber boundaries are heated by resistive heating elements. Both heating methods are subject to limitations of boundary-driven heating, where an inherent thermal gradient exists between heater and reaction. Therefore, there is a need to develop a simple and rapid PCR heating mechanism that is not subject to limitations of boundary-driven heating.Alternating current (AC) electrokinetics has many uses in microfluidics, from dielectrophoresis, the study of induced dipoles on a particle in an electric field, to electrokinetic fluid pumping, where conductivity and thermal gradients drive fluid flow. A common side effect I would also like to thank my lab mates Steven Doria and Edwin Lavi for introducing me to the fields of microfluidics and lithography. In addition, I would like to thank my other lab mates, Md Nazibul Islam for his assistance with device photography and COMSOL simulations, and Yuncheng (Max) Yu for taking SEM images of electrode chips. A general thanks goes to all of my lab mates for their support, wisdom, and advice. My thanks also extend to my previous scientific mentors at Colorado State University & Boston Biochem, where my passion for engineering and biotechnology grew into what it is today. Finally, I would like to thank my family and friends I have made through Chemical Engineering and Club Swimming for their support, laughter, and advice during my time at Texas A&M University. I could not have achieved what I did without them. vi CONTRIBUTORS AND FUNDING SOURCES Contributors This work was supervised by a thesis committee consisting of Professor Gagnon (advisor) & Professor Ugaz of the Department of Chemical Engineering and Professor Jain of the Department of Biomedical Engineering. COMSOL simulations of electrokinetic heating were performed in collaboration with Md Nazibul Islam. Additionally, various pictures for figures & diagrams were taken by Md Nazibul Islam. Scanning electron microscope (SEM) images of electrodes were taken by Yuncheng (Max) Yu. All other work conducted for this thesis was completed by the student independently,