Facile and efficient preparation of anisotropic DNA-functionalized gold nanoparticles and their regioselective assembly

Abstract

Anisotropic nanoparticles can provide considerable opportunities for assembly of nanomaterials with unique structures and properties. However, most reported anisotropic nanoparticles are either difficult to prepare or to functionalize. Here we report a facile one-step solution-based method to prepare anisotropic DNA-functionalized gold nanoparticles (a-DNA-AuNP) with 96% yield and with high DNA density (120 ± 20 strands on the gold hemisphere). The method is based on the competition between a thiolated hydrophilic DNA and a thiolated hydrophobic phospholipid and has been applied to prepare a-DNA-AuNPs of different sizes and with a variety of DNA sequences. In addition, DNA strands on the a-DNA-AuNPs can be exchanged with other DNA strands with a different sequence. The anisotropic nature of the a-DNA-AuNPs allows regioselective hetero- and homonuclear assembly with high monodispersity, as well as regioselective functionalization of two different DNA strands for more diverse applications.

Figure 1

(a) Schematic for the synthesis of a-DNA-AuNP where HS-A10, PSH, PSPAA and AuNP are incubated at 95°C for two hours in DMF/H₂O. TEM micrographs of (b) 15 nm a-DNA-AuNP, (c) 20 nm a-AuNP, (d) completely unencapsulated AuNP when no PSH was added, (e) fully encapsulated AuNP when no SH-A10 was added. (f) UV-vis absorption spectra of citrate-capped AuNP, the a-DNA-AuNP sample in (b), and fully encapsulated AuNP (d), inset shows the shift of plasmon peak from 525 nm to 535 nm. Scale bar = 50 nm.

Figure 2

(a) Schematic for the functionalization of a-AuNP with D1 resulting in a-(D1)-AuNP. Schematic of selective assembly of a-(D1)-AuNP (b) with 5 nm c-AuNPs and (c) 10 nm c-AuNPs with its corresponding TEM micrographs and histogram showing particle analysis. Scale bars are 50 nm.

Figure 3

(a) a-(D1)-AuNP – 30 nm c-AuNP assemblies at a ratio of 1:1 (upper) and 10:1 (lower). (b) Hetero-assembly of 20 nm and 13 nm a-(D1)-AuNP. (c) Homo – assembly of a-(D1)-AuNP using a linker strand D3. Scale bar = 100 nm; (insets) 25 nm.

Figure 4

(a) Scheme showing functionalization of D4 on the polymer side of the particle via EDC coupling. Fluorescence spectra of a-(D1+D4)-AuNP before and after incubation with (b) D5 c-AuNP and (c) D2 c-AuNP.