Probing Soft Corona Structures of DNA-Capped Nanoparticles by Small Angle Neutron Scattering

Soft corona structures of DNA-capped nanoparticles are crucial for their applications in diagnostics, gene delivery, and superlattice growth. While conventional X-ray techniques can only provide information on their inorganic cores, here we report substantial new insights of DNA corona structures within DNA-capped nanoparticles in this first study employing small angle neutron scattering (SANS). Using two 15-mer DNA strands with palindromic sequence and poly­(dT) sequence under high number density packing on gold nanoparticle surfaces, the influence of ionic strength and temperature on DNA corona structures and resultant hybridization has been investigated. Poly­(dT) sequences were found to maintain globular corona structures across a range of ionic strengths and temperatures, but the corona thickness decreased with increasing salt concentration and increased with increasing temperature. In contrast, palindromic sequenced DNA had globular corona structures in the absence of salt but quickly evolved into dimeric and multimeric structures under high ionic strength or under low annealing temperatures. The structural insights revealed by SANS can guide the design of tailor-made DNA corona structures for customizable designer materials and devices

Fabrication and Structural Characterization of Module-Assembled Amphiphilic Conetwork Gels

Structural analysis of inhomogeneity-free poly­(ethylene glycol)–poly­(dimethyl­siloxane) (PEG–PDMS) amphiphilic conetwork gels has been performed by the complementary use of small-angle X-ray and neutron scattering. Because of the hydrophobicity of PDMS units, the PEG–PDMS gels exhibit a microphase-separated structure in water. Depending on the volume fraction of PDMS, the microphase-separated structure varies from core–shell to lamellar. The obtained X-ray and neutron scattering profiles are reproduced well using a core–shell model together with a Percus–Yevick structure factor when the volume fraction of PDMS is small. The domain size is much larger than the size of individual PEG and PDMS unit, and this is explained using the theory of block copolymers. Reflecting the homogeneous dispersion conditions in the as-prepared state, scattering peaks are observed even at a very low PDMS volume fraction (0.2%). When the volume fraction of PDMS is large, the microphase-separated structure is lamellar and is demonstrated to be kinetically controlled by nonequilibrium and topological effects