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DNA functionalized gold nanoparticles (DNA-AuNPs) have shown great potential for biosensing as they combine the excellent optical properties of gold nanoparticles and the molecular recognition function of DNA. Since the DNA density determines the assay performance and the stability of the conjugate, a precise control of the surface density of DNA-AuNP is crucial for an optimized biosensor. Here we report a simple assay for quantifying multiple unlabeled DNAs on AuNPs. The assay relies on potassium cyanide (KCN) to first dissolve the AuNPs, which then releases surface bound DNA for quantification through a double-stranded DNA dye. Using this analytical quantification method, we investigated several strategies to control the surface density of DNA-AuNPs. Besides the precise control of DNA density, the stability of DNA-AuNPs after conjugation is also important in developing a biosensor with optimal performance. Without proper storing conditions, DNA-AuNPs are unstable and aggregate over time. To overcome this problem, we developed a long-term storage solution to ensure the stability and quality of DNA-AuNPs after conjugation which would benefit any DNA-AuNP-based biosensor., Competing Interests: Declaration of Competing Interest The authors declare no competing financial interests., (Copyright © 2019 Elsevier B.V. All rights reserved.)

New low-temperature inserts compatible with an existing hyperpolarizer were developed to dynamically polarize nuclei in large samples. The performance of the system was tested on 8 ml glassy frozen solutions containing 13C-labeled molecules and doped with nitroxyl free radicals. The obtained 13C low-temperature polarization was comparable to the one measured on 20 times smaller sample volume with only 3-4 times higher microwave power. By using a dissolution insert that fits to the new design, it was possible to obtain about 120 ml of room-temperature hyperpolarized solution. The polarization as well as the molecule concentration was comparable to the values obtained in standard size hyperpolarized samples. Such large samples are interesting for future studies on larger animals and possibly for potential clinical applications.