Core-Shell Assisted Bimetallic Assembly of Pt and Ru Nanoparticles by DNA Hybridization

We have discovered that the current protocols to assemble Au nanoparticles based on DNA hybridization do not work well with the small metal nanoparticles (e.g. 5 nm Au, 3.6 nm Pt and 3.2 nm Ru particles). Further investigations revealed the presence of strong interaction between the oligonucleotide backbone and the surface of the small metal nanoparticles. The oligonucleotides in this case are recumbent on the particle surface and are therefore not optimally oriented for hybridization. The nonspecific adsorption of oligonucleotides on small metal nanoparticles must be overcome before DNA hybridization can be accepted as a general assembly method. Two methods have been suggested as possible solutions to this problem. One is based on the use of stabilizer molecules which compete with the oligonucleotides for adsorption on the metal nanoparticle surface. Unfortunately, the reported success of this approach in small Au nanoparticles (using K₂BSPP) and Au films (using 6-mercapto-1-hexanol) could not be extended to the assembly of Pt and Ru nanoparticles by DNA hybridization. The second approach is to simply use larger metal particles. Indeed most reports on the DNA hybridization induced assembly of Au nanoparticles have made use of relatively large particles (>10 nm), hinting at a weaker non-specific interaction between the oligonucleotides and large Au nanoparticles. However, most current methods of nanoparticle synthesis are optimized to produce metal nanoparticles only within a narrow size range. We find that core-shell nanoparticles formed by the seeded growth method may be used to artificially enlarge the size of the metal particles to reduce the nonspecific binding of oligonucleotides. We demonstrate herein a core-shell assisted growth method to assemble Pt and Ru nanoparticles by DNA hybridization. This method involves firstly synthesizing approximately 16 nm core-shell Ag-Pt and 21 nm core-shell Au-Ru nanoparticles from 9.6 nm Ag seeds and 17.2 nm Au seeds respectively by the seed-mediated growth method. The core-shell nanoparticles were then functionalized by complementary thiolated oligonucleotides followed by aging in 0.2 M PBS buffer for 6 hours. The DNA hybridization induced bimetallic assembly of Pt and Ru nanoparticles could then be carried out in 0.3 M PBS buffer for 10 hours.

Biennial report.

No report for 1919/1920-1921/22.

Troy and Greenfield Railroad : speech of Hon. Alvah Crocker, on the bill for the more speedy completion of the Troy and Greenfield Railroad, in the Senate of Massachusetts, April 15, 1862.

At head of title: Troy and Greenfield Railroad.

Vermont legislative directory /

None issued in 1914.

Journal of the House of Representatives of the State of South-Carolina.

Vols. for 1843-1845, 1847-1851, 1854-1855, 1857 bound with the Journal of the Senate and Reports and resolutions of South Carolina to the General Assembly; extra session for 1882 with the Journal of the Senate.

Memorial addresses on the death of Gov. John W. Geary /

"Printed by order of the Senate and House of Representatives."

Journal of the proceedings of the House of Delegates of the State of Maryland.

Journals for some sessions bound with those of the Senate.

House journal.

Vols. for 3d-4th sessions, 1881-83, bound with the Senate journal; extraordinary session of 1903 includes the Senate journal.

Acts and proceedings of the General assemblies of the Kirk of Scotland, from the year M.D.LX. Collected from the most authentic manuscripts ...

Edited by Thomas Thomson.

The works of John C. Calhoun.

Published under the direction of the General Assembly of South Carolina.

Laws passed by the Legislative Council and the House of Representatives of Illinois Territory at their... session held at Kashashia.

Title page and p. 1-8 of incorporation laws of the State of Illinois, 1836, incorrectly substituted for t.p. and p. 1-8 of the laws of the 10th General Assembly.

Annual report of the Railroad and Warehouse Commissioners of the State of Missouri for the year ending ...

Vol. for 1893/94 covers the eighteen months from Jan. 1, 1893 to June 30, 1894.

Journal.

Mode of access: Internet.

Special report of the State Board of Insanity to the Massachusetts General Court as to the best method of providing for the insane. (In compliance with chapter 34, resolves of 1908) May, 1908.

At head of title: Senate document no. 358.

Journal.

Includes the called and special sessions.