Liquid Metal Nanocores Initiated Construction of Smart DNA-Polymer Microgels with Programmable and Regulable Functions and Near-Infrared Light-Driven Locomotion.

Due to their sequence-directed functions and excellent biocompatibility, smart DNA microgels have attracted considerable research interest, and the combination of DNA microgels with functional nanostructures can further expand their applications in biosensing and biomedicine. Gallium-based liquid metals (LMs) exhibiting both fluidic and metallic properties hold great promise for the development of smart soft materials; in particular, LM particles upon sonication can mediate radical-initiated polymerization reactions, thus allowing the combination of LMs and polymeric matrix to construct "soft-soft" materials. Herein, by forming active surfaces under sonication, LM nanoparticles (LM NPs) initiated localized radical polymerization reactions allow the combination of functional DNA units and different polymeric backbones to yield multifunctional core/shell microgels. The localized polymerization reaction allows fine control of the microgel compositions, and smart DNA microgels with tunable catalytic activities can be constructed. Moreover, due to the excellent photothermal effect of LM NPs, the resulting temperature gradient between microgels and surrounding solution upon NIR light irradiation can drive the oriented locomotion of the microgels, and remote control of the activity of these smart microgels can be achieved. These microgels may hold promise for various applications, such as the development of in vivo and in vitro biosensing and drug delivery systems.

A portable colorimetric point-of-care testing platform for MicroRNA detection based on programmable entropy-driven dynamic DNA network modulated DNA-gold nanoparticle hybrid hydrogel film.

Point-of-care testing (POCT) platforms for microRNA (miRNA) detection have attracted considerable attention in recent years, due to the increasingly important role of miRNA as biomarkers for the diagnosis of many diseases, such as cancers. However, several limitations such as the requirement of enzyme-related amplification system, expensive preservation cost, sophisticated analysis instruments and tedious operations of conventional miRNA biosensing devices severely hinder their widespread applications. In this work, a portable and smart colorimetric analysis platform was developed by employing the ultrathin DNA-gold nanoparticle (AuNP) hybrid hydrogel film as the signaling unit and the enzyme-free entropy-driven dynamic DNA network (EDN) as the signal converter and amplification unit. By programming the DNA sequences of the EDN, the EDN could respond to a specific miRNA, with miRNA-155 or miRNA-21 as the model target, and release a converter DNA with amplified concentration to further trigger the release of AuNPs from the hydrogel film as a colorimetric signal output. To avoid the use of sophisticated spectral instruments, digital analysis based on primary three-color channel (R/G/B) was further introduced by using user-friendly camera and image processing software, and a detection limit at pM level was achieved. Moreover, by introducing H2O2-mediated AuNPs enlargement procedure in the colorimetric analysis platform, the detection limit for miRNA target could further be enhanced to fM level. The POCT platform is also portable and storable with a good storage stability for at least 45 days, suggesting its great potential in practical diagnosis applications.

Smart DNA-gold nanoparticle hybrid hydrogel film based portable, cost-effective and storable biosensing system for the colorimetric detection of lead (II) and uranyl ions.

A portable, cost-effective and storable DNA-gold nanoparticle (AuNP) hybrid hydrogel film based biosensing system was developed, with AuNPs serving as both the crosslinking units of the film and the signaling units. Using a layer-by-layer assembly method, hydrogel film composed of three-dimensional hydrophilic network of densely packed AuNPs interconnected by responsive DNA structures was constructed onto a glass slide. By programming the sequence of DNA structures, target-responsive hybrid films were constructed. As a proof of concept, the sequence of a substrate DNA which can be identified and cleaved by Pb2+-dependent DNAzyme was encoded to construct Pb2+-responsive DNA-AuNP hybrid hydrogel film. The high-density packing of AuNPs as signal substances significantly improved the sensitivity of the ultrathin film biosensing system while reduced the cost of expensive DNA materials. A hydrogel film composed of 10 layers of assembled DNA-AuNP structures generated sufficient visual colorimetric signals for Pb2+ detection, with a detection limit of 2.6 nM. By introducing UO22+-dependent DNAzyme, the system could be further applied in the sensitive and selective detection of UO22+, with a detection limit of 10.3 nM. Compared with bulk-sized DNA hydrogel biosensing systems, the DNA-AuNP hydrogel film biosensing system exhibited faster response thanks to the sub-micrometer ultrathin film structures. Moreover, the protection of fragile non-covalently crosslinked DNA films with solid slides also facilitated the portable application and long-term storage of the resulting biosensing system, with 95% of the response signal retained after three months of storage. The DNA-AuNPs hydrogel film biosensing system is highly promising for future rapid on-site detection applications.