Decoupled Roles of DNA-Surfactant Interactions: Instant Charge Inversion, Enhanced Colloidal and Chemical Stabilities, and Fully Tunable DNA Conjugation of Shaped Plasmonic Nanocrystals

Advanced Synthesis of Spherical Nucleic Acids: A Limit-Pursuing Game with Broad Implications

Spherical nucleic acids (SNAs) consist of DNA strands arranged radially and packed densely on the surface of nanoparticles. Due to their unique properties, which are not found in naturally occurring linear or circular DNA, SNAs have gained widespread attention in fields such as sensing, nanomedicine, and colloidal assembly. The rapidly evolving applications of SNAs have driven a modernization of their syntheses to meet different needs. Recently, several advanced approaches have emerged, enabling ultrafast, quantitative, and low-cost SNA synthesis with maximal DNA grafting through "counterintuitive" processes like freezing and dehydration. This concept paper discusses these critical developments from a synthetic perspective, focusing on their underlying mechanisms and broad implications, with a goal of inspiring future research in related fields.

Multivalent Weak Protections Ultimately Enable Customizable DNA Grafting on Pristine Ag Colloids for Nanoplasmonics

Silver nanoparticles (AgNPs) have superior plasmonic properties surpassing other metals. However, a long-standing difficulty in valence/density-tunable DNA grafting of AgNPs disfavors their use in DNA-directed nanoplasmonics. Herein a close-to-ideal surface protection of pristine AgNPs against various notorious stability issues of Ag is achieved based on multidentate weak nucleobase bindings of non-programming FSDNA (fish sperm DNA). This further allows grafting of thiolated DNA with tunable valence/density on AgNPs. The end-on format of the thiolated DNA grafts and the very thin FSDNA layer benefit DNA hybridization and plasmon coupling, respectively. Significantly promoted optical coupling and Raman enhancing are achieved. The compatibility of FSDNA-capped AgNPs with Au enables DNA-bonded symmetry-broken Au-Ag heterodimers with strong near-field coupling and an easily seen Fano-induced feature. Our work provides a treasured freedom of using AgNPs in DNA-programmed, better-behaving plasmonic devices.

Multicolor-Assay-on-a-Chip Processed by Robotic Operation (MACpro) with Improved Diagnostic Accuracy for Field-Deployable Detection

The ability to deploy decentralized laboratories with autonomous and reliable disease diagnosis holds the potential to deliver accessible healthcare services for public safety. While microfluidic technologies provide precise manipulation of small fluid volumes with improved assay performance, their limited automation and versatility confine them to laboratories. Herein, we report the utility of multicolor assay-on-a-chip processed by robotic operation (MACpro), to address this unmet need. The MACpro platform comprises a robot-microfluidic interface and an eye-in-hand module that provides flexible yet stable actions to execute tasks in a programmable manner, such as the precise manipulation of the microfluidic chip along with different paths. Notably, MACpro shows improved detection performance by integrating the microbead-based antibody immobilization with enhanced target recognition and multicolor sensing via Cu2+-catalyzed plasmonic etching of gold nanorods for rapid and sensitive analyte quantification. Using interferon-gamma as an example, we demonstrate that MACpro completes a sample-to-answer immunoassay within 30 min and achieves a 10-fold broader dynamic range and a 10-fold lower detection limit compared to standard enzyme-linked immunosorbent assays (0.66 vs 5.2 pg/mL). MACpro extends the applications beyond traditional laboratories and presents an automated solution to expand diagnostic capacity in diverse settings.

Efficient Poly-Adenine-Tailed DNA Functionalization of Gold Nanorods for Tailored Nanostructure Assembly

Gold nanorods (AuNRs) with unique optical properties play a pivotal role in applications in plasmonic imaging, small molecule detection, and photothermal therapy. However, challenges in DNA functionalization of AuNRs hinder their full potential due to the presence of a dense cetyltrimethylammonium bromide (CTAB) bilayer, impeding close DNA contact. In this study, we introduced a convenient approach for the rapid assembly of polyadenine (polyA) tailed DNA on AuNRs with control of DNA density, rigidity, and valence. We explored the impact of DNA with designed properties on the construction of core-satellite structures by employing AuNRs as cores and spherical gold nanoparticles (AuNSs) as satellites. Density, rigidity, and valence are identified as crucial factors for efficient construction. Specifically, polyA-tailed DNA modulated DNA density and reduced spatial hindrance and electrostatic repulsion, thereby facilitating the construction. Enhancing the rigidity of DNA and incorporating multiple binding sites can further improve the efficiency.

Aptamer functionalized gold nanoclusters as an emerging nanoprobe in biosensing, diagnostic, catalysis and bioimaging

DNA nanostructures, with their fascinating luminescent and detecting capabilities, provide a basis that can accommodate a wide range of applications. The unique electronic configurations, and physical and chemical properties of aptamer-assembled gold nanoclusters (apt-AuNCs) as a novel type of fluorophore have gradually piqued the interest of the scientific community. Bending DNA sequences and other templates/legends as a stabilizing agent with Au metal has produced an abundance of biosensors, along with catalytic and imaging properties. This review article summarizes the synthesis, conjugation tactics, advantages, and sensing mechanisms of AuNCs aptasensor after providing a brief introduction to the topic. Moreover, the application of DNA/aptamer functionalization has been briefly discussed in the fields of food safety and quality, catalysis, clinical diagnosis, cancer cell bioimaging, detection of cancer cell indicators, and therapy. We also concluded the current obstacles and made recommendations about the future prospects of AuNCs for fundamental research and applications in line with the developments in DNA/aptamer-AuNCs.

Assembly and Healing: Capacitive and Conductive Plasmonic Interfacing via a Unified and Clean Wet Chemistry Route

Solution-based nanoparticle assembly represents a highly promising way to build functional metastructures based on a wealth of synthetic nanomaterial building blocks with well-controlled morphology and crystallinity. In particular, the involvement of DNA molecular programming in these bottom-up processes gradually helps the ambitious goal of customizable chemical nanofabrication. However, a fundamental challenge is to realize strong interunit coupling in an assembly toward emerging functions and applications. Herein, we present a unified and clean strategy to address this critical issue based on a H2O2-redox-driven "assembly and healing" process. This facile solution route is able to realize both capacitively coupled and conductively bridged colloidal boundaries, simply switchable by the reaction temperature, toward bottom-up nanoplasmonic engineering. In particular, such a "green" process does not cause surface contamination of nanoparticles by exogenous active metal ions or strongly passivating ligands, which, if it occurs, could obscure the intrinsic properties of as-formed structures. Accordingly, previously raised questions regarding the activities of strongly coupled plasmonic structures are clarified. The reported process is adaptable to DNA nanotechnology, offering molecular programmability of interparticle charge conductance. This work represents a new generation of methods to make strongly coupled nanoassemblies, offering great opportunities for functional colloidal technology and even metal self-healing.