Acoustic Levitation Synthesis of Ultrahigh-Density Spherical Nucleic Acid Architectures for Specific SERS Analysis.

Controllably regulating the electrostatic bilayer of nanogold colloids is a significant premise for synthesizing spherical nucleic acid (SNA) and building ordered plasmonic architectures. We develop a facile acoustic levitation reactor to universally synthesize SNAs with an ultra-high density of DNA strands, which is even higher than those of various state-of-the-art methods. Results reveal a new mechanism of DNA grafting via acoustic wave that can reconfigure the ligands on colloidal surfaces. The acoustic levitation reactor enables substrate-free three-dimentional (3D) spatial assembly of SNAs with controllable interparticle nanogaps through regulating DNA lengths. This kind of architecture may overcome the plasmonic enhancement limits by blocking electron tunneling and breaking electrostatic shielding in dried aggregations. Finite element simulations support the architecture with 3D spatial plasmonic hotspot matrix, and its ultrahigh surface-enhanced Raman scattering (SERS) capability is evidenced by in situ untargeted tracking of biomolecular events during photothermal stimulation (PTS)-induced cell death process. For biomarker diagnosis, the conjugation of adenosine triphosphate (ATP) aptamer onto SNAs enables in situ targeted tracking of ATP during PTS-induced cell death process. Particularly, the CD71 receptor and integrin α3ß1 protein on PL45 cell membrance could be well distinguished by label-free SERS fingerprints when using specific XQ-2d and DML-7 aptamers, respectively, to synthesize SNA architectures. Our current acoustic levitation reactor offers a new method for synthesizing SNAs and enables both targeted and untargeted SERS analysis for tracking molecular events in living systems. It promises great potentials in biochemical synthesis and sensing in future.

Quantified instant conjugation of peptides on a nanogold surface for tunable ice recrystallization inhibition.

The adverse effects of recrystallization limit the application of cryopreservation in many fields. Peptide-based materials play an essential role in the antifreezing area because of their excellent biocompatibility and abundant ice-binding sites. Peptide-gold nanoparticle conjugates can effectively reduce time and material costs through metal-thiol interactions, but controlled modification remains an outstanding issue, which makes it difficult to elucidate the antifreezing effects of antifreeze peptides at different densities and lengths. In this study, we developed an instant peptide capping on gold nanoparticles with butanol-assisted dehydration and provided a controllable quantitative coupling within a certain range. This chemical dehydration makes it possible to fabricate peptide-gold nanoparticle conjugates in large batches at minute levels. Based on this, the influence of the peptide density and sequence length on the antifreezing behaviors of the conjugates was investigated. The results evidenced that the antifreezing property of the flexible peptide conjugated on a rigid core is related to both the density and length of the peptide. In a certain range, the density is proportional to the antifreeze, while the length is negatively correlated with it. We proposed a rapidly controllable method for synthesizing peptide-gold nanoparticle conjugates, which may provide a universal approach for the development of subsequent recrystallization-inhibiting materials.