Aren E. Gerdon

DNA technology has enabled the creation of molecular structures with endless creativity and exceptional fidelity. These structures, including DNA origami, are on the order of tens to hundreds of nanometers in size and have previously been shown to influence solid-forming reactions like silica, calcium carbonate, and calcium phosphate mineralization related to bone and enamel formation, providing new promise for biomedical applications. In this work, we expand the dimensions of DNA technology to produce micron-sized (0.01–100 μm2) DNA origami arrays. These arrays are controllable in their assembly and enhance the mineralization of calcium phosphate within the footprint of the array. Structures that resemble sheets, webs, and fibers have been mineralized. TEM and AFM imaging has identified a range of mineral morphologies including small (10–50 nm) amorphous clusters, dense layers of mineral, and mineral forming along the length of origami fibers. This range of morphologies shows the versatility of this array design. Mineralized materials with specific micron dimensions, such as these, could prove useful in future bone repair applications.

Calcium materials, such as calcium carbonate, are produced in natural and industrial settings that range from oceanic to biomedical. An array of biological and biomimetic template molecules have been employed in controlling and understanding the mineralization reaction but have largely focused on small molecule additives or disordered polyelectrolytes. DNA aptamers are synthetic and programmable biomolecules with polyelectrolyte characteristics but with predictable and controllable secondary structure akin to native extracellular moieties. This work demonstrates for the first time the influence of DNA aptamers with known G-quadruplex structures on calcium carbonate mineralization. Aptamers demonstrate kinetic inhibition of mineral formation, sequence and pH-dependent uptake into the mineral, and morphological control of the primarily calcite material in controlled solution conditions. In reactions initiated from the complex matrix of ocean water, DNA aptamers demonstrated enhancement of mineralization kinetics and resulting amorphous material. This work provides new biomimetic tools to employ in controlled mineralization and demonstrates the influence that template secondary structure can have in material formation.

Electrochemical analysis of cobalt(III) protoporphyrin IX (CoP), synthesis and characterization of CoP nanoparticles, and signal amplification for biosensor development is presented. CoP was self‐assembled into nanoparticles and then released to produce over 1000 electrochemically‐detectable molecules for each protein target of interest, in this case monoclonal rabbit antibody. Anodic stripping voltammetry was utilized for quantitative and sensitive detection of CoP which correlated to target protein concentration. The CoP limit of detection was 4 nM and target protein was detected at 100 pM. This combination of nanoparticle and electrochemical signal amplification could allow for sensitive, inexpensive, and portable detection of protein biomarkers.

DNA aptamers previously selected as calcium phosphate mineralization templates were modified and analyzed to better understand structure-function relationships and to explore the mechanism of templated mineralization. Aptamers were created to strengthen or remove a prevalent G-quadruplex structure and were analyzed for structural stability, affinity to calcium phosphate, influence on homogenous and heterogeneous calcium phosphate mineralization, and influence on mineral crystallinity and morphology. Aptamers were found to modulate mineralization kinetics in a concentration-dependent manner. Changes to the G-quadruplex structure affected affinity to hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂, HAP) and had a substantial impact on the mineral crystallinity. We propose a model for aptamer-directed mineralization and anticipate the usefulness of these aptamer sequences in future biomimetic and biomedical applications.

The Multi-Rule Quality Control System (MRQCS) is a tool currently employed by the Centers for Disease Control and Prevention (CDC) to evaluate and compare laboratory performance. We have applied the MRQCS to a comparison of instructor-led and computer-led prelaboratory instruction for a supplemental learning experiment. Students in general chemistry and analytical chemistry from both two- and four-year institutions performed two laboratory experiments as part of their normal laboratory curriculum. The first laboratory experiment was a foundational learning experiment in which all of the students were introduced to the Beer–Lambert law and spectrophotometric light absorbance measurements. The foundational learning experiment was instructor-led only, and participant performance was evaluated against a mean characterized value. The second laboratory experiment was a supplemental learning experiment in which students were asked to build upon the methodology they learned in the foundational learning experiment and apply it to a different analyte. The instruction type was varied randomly into two delivery modes, with participants receiving either instructor-led or computer-led prelaboratory instruction. The MRQCS was applied, and it was determined that there was no statistical difference between the quality control passing rates of the participants receiving instructor-led instruction and those receiving computer-led instruction. These findings demonstrate the successful application of the MRQCS to evaluate knowledge and technology transfer.