We build off the previously described concept of a nano-flare to develop an oligonucleotide gold nanoparticle conjugate that is capable of both detecting and regulating intracellular levels of mRNA. We characterize the binding rate and specificity of these materials using survivin, a gene associated with the diagnosis and treatment of cancer, as a target. The nanoconjugate enters cells and binds mRNA, thereby decreasing the relative abundance of mRNA in a dose-and sequence-dependent manner and resulting in a fluorescent response. This represents the first demonstration of a single material capable of both mRNA regulation and detection. Further, we investigate the intracellular biochemistry of the nanoconjugate, elucidating its mechanism of gene regulation. This work is important to the study of biologically active nanomaterials such as the nano-flare and is a first step towards the development of an mRNA responsive 'theranostic'. KeywordsNanoparticle; oligonucleotide; mRNA; detection; gene regulation; theranostic Over the past decade, researchers have investigated the conjugation of biomolecules to inorganic nanomaterials, which has led to the development of hybrid materials with new activities. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] One important class of hybrid nanomaterial is composed of a gold nanoparticle functionalized with a dense monolayer of oligonucleotides. These polyvalent nanoconjugates have many interesting properties, including distance-dependent optical features, 21,22 enhanced nucleic acid binding, 23 resistance to degradation, 24 and the ability to enter cells without use of transfection agents. 25 These remarkable properties have enabled controlled assembly of materials, 26-28 molecular diagnostics, [29][30][31][32] and intracellular studies. [33][34][35] Materials with both regulation and detection capabilities are of growing interest for use in personalized medicine. 36 These 'theranostic' materials have the potential to both treat and diagnose disease and are useful for investigating intracellular events (i.e. target recognition and control of biological function). Traditionally, antisense oligonucleotides and molecular beacons have been used to regulate and detect intracellular mRNA, respectively. Antisense oligonucleotides regulate gene expression by binding target mRNA and preventing translation. 37 Molecular beacons detect nucleic acids by coupling a binding event with a signal transduction mechanism, such as the separation of a fluorophore-quencher pair. 38 Given that cell entry and mRNA binding are the first steps in both processes, it should be possible to design a single material for both regulation and detection. To the best of our knowledge, however, a material capable of both mRNA regulation and detection has not been reported. 39 Such materials must be readily taken up by cells, stable in intracellular environments, capable of binding nucleic acids, and possess a switchable signal that can be conveniently detected. NIH Public Access RES...

Numerical simulations are used in this work to investigate aspects of microstructure and microseg-regation during rapid solidification of a Ni-based superalloy in a laser powder bed fusion additive manufacturing process. Thermal modeling by finite element analysis simulates the laser melt pool, with surface temperatures in agreement with in situ thermographic measurements on Inconel 625. Geometric and thermal features of the simulated melt pools are extracted and used in subsequent mesoscale simulations. Solidification in the melt pool is simulated on two length scales. For the multicomponent alloy Inconel 625, microsegregation between dendrite arms is calculated using the Scheil-Gulliver solidification model and DICTRA software. Phase-field simulations, using Ni–Nb as a binary analogue to Inconel 625, produced microstructures with primary cellular/dendritic arm spacings in agreement with measured spacings in experimentally observed microstructures and a lesser extent of microsegregation than predicted by DICTRA simulations. The composition profiles are used to compare thermodynamic driving forces for nucleation against experimentally observed precipitates identified by electron and X-ray diffraction analyses. Our analysis lists the precipitates that may form from FCC phase of enriched interdendritic compositions and compares these against experimentally observed phases from 1 h heat treatments at two temperatures: stress relief at 1143 K (870 °C) or homogenization at 1423 K (1150 °C).

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Measurement of the high-temperature melt pool region in the laser powder bed fusion (L-PBF) process is a primary focus of researchers to further understand the dynamic physics of the heating, melting, adhesion, and cooling which define this commercially popular additive manufacturing process. This paper will detail the design, execution, and results of high speed, high magnification in-situ thermographic measurements conducted at the National Institute of Standards and Technology (NIST) focusing on the melt pool region of a commercial L-PBF process. Multiple phenomena are observed including plasma plume and hot particle ejection from the melt region. The thermographic measurement process will be detailed with emphasis on the ‘measurability’ of observed phenomena and the sources of measurement uncertainty. Further discussion will relate these thermographic results to other efforts at NIST towards L-PBF process finite element simulation and development of in-situ sensing and control methodologies.

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