Logic Catalytic Interconversion of G-Molecular Hydrogel

DNA-amphiphilic nanostructures: synthesis, characterization and applications

DNA's extraordinary potential reaches far beyond its role as a carrier of genetic information. It serves as a remarkably adaptable structural foundation for constructing intricate nanostructures with a diverse range of functionalities. This inherent programmability sets DNA apart from other biomolecules like peptides, proteins, and small molecules. By covalently attaching DNA to synthetic hydrophobic moieties, researchers create DNA amphiphiles capable of interacting with artificial lipid bilayers and cell membranes. These hybrid structures have rapidly gained prominence due to their promising potential in the medical field. This review provides a comprehensive overview of the latest advancements in the synthesis of DNA amphiphiles and their assembly into well-defined nanostructures. It explores the diverse applications of these nanostructures across various medical domains, including targeted drug delivery, innovative immunotherapies, and gene-silencing techniques. Moreover, the review delves into the current challenges and prospects of this rapidly evolving field, highlighting the potential of DNA hybrid materials to revolutionize medical treatments and diagnostics. By addressing the limitations and exploring new avenues of research, scientists aim to unlock the full potential of DNA nanotechnology for the benefit of human health.

Fluorescence-Based Multimodal DNA Logic Gates

The use of DNA structures in creating multimodal logic gates bears high potential for building molecular devices and computation systems. However, due to the complex designs or complicated working principles, the implementation of DNA logic gates within molecular devices and circuits is still quite limited. Here, we designed simple four-way DNA logic gates that can serve as multimodal platforms for simple to complex operations. Using the proximity quenching of the fluorophore-quencher pair in combination with the toehold-mediated strand displacement (TMSD) strategy, we have successfully demonstrated that the fluorescence output, which is a result of gate opening, solely relies on the oligonucleotide(s) input. We further demonstrated that this strategy can be used to create multimodal (tunable displacement initiation sites on the four-way platform) logic gates including YES, AND, OR, and the combinations thereof. The four-way DNA logic gates developed here bear high promise for building biological computers and next-generation smart molecular circuits with biosensing capabilities.

A bioenergetically-active ploy (glycerol sebacate)-based multiblock hydrogel improved diabetic wound healing through revitalizing mitochondrial metabolism

Diabetic wounds impose significant burdens on patients' quality of life and healthcare resources due to impaired healing potential. Factors like hyperglycemia, oxidative stress, impaired angiogenesis and excessive inflammation contribute to the delayed healing trajectory. Mounting evidence indicates a close association between impaired mitochondrial function and diabetic complications, including chronic wounds. Mitochondria are critical for providing energy essential to wound healing processes. However, mitochondrial dysfunction exacerbates other pathological factors, creating detrimental cycles that hinder healing. This study conducted correlation analysis using clinical specimens, revealing a positive correlation between mitochondrial dysfunction and oxidative stress, inflammatory response and impaired angiogenesis in diabetic wounds. Restoring mitochondrial function becomes imperative for developing targeted therapies. Herein, we synthesized a biodegradable poly (glycerol sebacate)-based multiblock hydrogel, named poly (glycerol sebacate)-co-poly (ethylene glycol)-co-poly (propylene glycol) (PEPGS), which can be degraded in vivo to release glycerol, a crucial component in cellular metabolism, including mitochondrial respiration. We demonstrate the potential of PEPGS-based hydrogels to improve outcomes in diabetic wound healing by revitalizing mitochondrial metabolism. Furthermore, we investigate the underlying mechanism through proteomics analysis, unravelling the regulation of ATP and nicotinamide adenine dinucleotide metabolic processes, biosynthetic process and generation during mitochondrial metabolism. These findings highlight the therapeutic potential of PEPGS-based hydrogels as advanced wound dressings for diabetic wound healing.

Conductive and Eco-friendly Biomaterials-based Hydrogels for Noninvasive Epidermal Sensors: A Review

As noninvasive wearable electronic devices, epidermal sensors enable continuous, real-time, and remote monitoring of various human physiological parameters. Conductive biomaterials-based hydrogels as sensor matrix materials have good biocompatibility, biodegradability, and efficient stimulus response capabilities and are widely applied in motion monitoring, healthcare, and human-machine interaction. However, biomass hydrogel-based epidermal sensing devices still need excellent mechanical properties, prolonged stability, multifunctionality, and extensive practicality. Therefore, this paper reviews the common biomass hydrogel materials for epidermal sensing (proteins, polysaccharides, polyphenols, etc.) and the various types of noninvasive sensing devices (strain/pressure sensors, temperature sensors, glucose sensors, electrocardiograms, etc.). Moreover, this review focuses on the strategies of scholars to enhance sensor properties, such as strength, conductivity, stability, adhesion, and self-healing ability. This work will guide the preparation and optimization of high-performance biomaterials-based hydrogel epidermal sensors.

Smart G-quadruplex hydrogels: From preparations to comprehensive applications

In recent years, the accelerated development of G-quadruplexes and hydrogels has driven the development of intelligent biomaterials. Based on the excellent biocompatibility and special biological functions of G-quadruplexes, and the hydrophilicity, high-water retention, high water content, flexibility and excellent biodegradability of hydrogels, G-quadruplex hydrogels are widely used in various fields by combining the dual advantages of G-quadruplexes and hydrogels. Here, we provide a systematic and comprehensive classification of G-quadruplex hydrogels in terms of preparation strategies and applications. This paper reveals how G-quadruplex hydrogels skillfully utilize the special biological functions of G-quadruplexes and the skeleton structure of hydrogels, and expounds its applications in the fields of biomedicine, biocatalysis, biosensing and biomaterials. In addition, we deeply analyze the challenges in preparation, applications, stability and safety of G-quadruplex hydrogels, as well as potential future development directions.

Development of Mn2+-Specific Biosensor Using G-Quadruplex-Based DNA

Metal ions are used in various situations in living organisms and as a part of functional materials. Since the excessive intake of metal ions can cause health hazards and environmental pollution, the development of new molecules that can monitor metal ion concentrations with high sensitivity and selectivity is strongly desired. DNA can form various structures, and these structures and their properties have been used in a wide range of fields, including materials, sensors, and drugs. Guanine-rich sequences respond to metal ions and form G-quadruplex structures and G-wires, which are the self-assembling macromolecules of G-quadruplex structures. Therefore, guanine-rich DNA can be applied to a metal ion-detection sensor and functional materials. In this study, the IRDAptamer library originally designed based on G-quadruplex structures was used to screen for Mn²⁺, which is known to induce neurodegenerative diseases. Circular dichroism and fluorescence analysis using Thioflavin T showed that the identified IRDAptamer sequence designated MnG4C1 forms a non-canonical G-quadruplex structure in response to low concentrations of Mn²⁺. A serum resistance and thermostability analysis revealed that MnG4C1 acquired stability in a Mn²⁺-dependent manner. A Förster resonance energy transfer (FRET) system using fluorescent molecules attached to the termini of MnG4C1 showed that FRET was effectively induced based on Mn²⁺-dependent conformational changes, and the limit of detection (LOD) was 0.76 µM for Mn²⁺. These results suggested that MnG4C1 can be used as a novel DNA-based Mn²⁺-detecting molecule.

Fluorescent Aptaswitch for Detection of Lead Ions

Detection of metal ions has essential roles in biology, food industry, and environmental sciences. In this work, we developed a Pb²⁺ detection strategy based on a fluorophore-tagged Pb²⁺-binding aptamer. The DNA aptamer changes its conformation on binding Pb²⁺, switching from an "off" state (low fluorescence) to an "on" state (high fluorescence). This method provides a quantitative readout with a detection limit of 468 nM, is highly specific to Pb²⁺ when tested against other metal ions, and is functional in complex biofluids. Such metal sensing DNA aptamers could be coupled with other biomolecules for sense-and-actuate mechanisms in biomedical and environmental applications.

DNA-based enzymatic systems and their applications

DNA strands with unique secondary structures can catalyze various chemical reactions and mimic natural enzymes with the assistance of cofactors, which have attracted much research attention. At the same time, the emerging DNA nanotechnology provides an efficient platform to organize functional components of the enzymatic systems and regulate their catalytic performances. In this review, we summarize the recent progress of DNA-based enzymatic systems. First, DNAzymes (Dzs) are introduced, and their versatile utilities are summarized. Then, G-quadruplex/hemin (G4/hemin) Dzs with unique oxidase/peroxidase-mimicking activities and representative examples where these Dzs served as biosensors are explicitly elaborated. Next, the DNA-based enzymatic cascade systems fabricated by the structural DNA nanotechnology are depicted. In addition, the applications of catalytic DNA nanostructures in biosensing and biomedicine are included. At last, the challenges and the perspectives of the DNA-based enzymatic systems for practical applications are also discussed.

Construction of Multiple Logic Circuits Based on Allosteric DNAzymes

In DNA computing, the implementation of complex and stable logic operations in a universal system is a critical challenge. It is necessary to develop a system with complex logic functions based on a simple mechanism. Here, the strategy to control the secondary structure of assembled DNAzymes’ conserved domain is adopted to regulate the activity of DNAzymes and avoid the generation of four-way junctions, and makes it possible to implement basic logic gates and their cascade circuits in the same system. In addition, the purpose of threshold control achieved by the allosteric secondary structure implements a three-input DNA voter with one-vote veto function. The scalability of the system can be remarkably improved by adjusting the threshold to implement a DNA voter with 2n + 1 inputs. The proposed strategy provides a feasible idea for constructing more complex DNA circuits and a highly integrated computing system.

A novel self-cleaning electrochemical biosensor integrating copper porphyrin-derived metal-organic framework nanofilms, G-quadruplex, and DNA nanomotors for achieving cyclic detection of lead ions

A self-cleaning electrochemical biosensor based on two-dimensional Cu-porphyrin (Cu-TCPP) metal-organic framework nanofilms, novel super G-quadruplex (G4), and DNA nanomotors was developed for the cyclic detection of Pb²⁺ ions. The Cu-TCPP framework with inherent peroxidase activity can create an ultra-thin nanofilm that functioned as a carrier to support the metastable G4 comprising four individual DNA strands. The introduction of Pb²⁺ and the intercalation of hemin can help it to form stable G4-hemin DNAzymes, which exhibits strong catalytic H₂O₂ reduction activity, and its number will be directly related to the amount of the introduced Pb²⁺. Moreover, a DNA nanomotor system is introduced to achieve cyclic detection, and the addition of the fuel DNA strands enables G4 to perform a "complete-dissociation-complete" process for achieving self-cleaning of the electrode interface and the cycle detection of Pb²⁺. The synergistic effects of Cu-TCPP and G4-hemin DNAzymes, which exhibits efficient and catalytic H₂O₂ reduction, enhance the performance of the electrochemical sensing system. The linear range of this sensor to Pb²⁺ is 5 nM-5 μM, and the detection limit is 1.7 nM. Compared with the best system in reported studies, its linear range is five times wider and its detection limit is lower than the previously lowest one. Taking advantage of the Pb²⁺ stabilized G4, the proposed sensor can selectively detect Pb²⁺ in the presence of other metal ions. The results presented herein comprise a valuable reference for constructing DNA nanoelectronic devices and establish sensitive and cyclic detection of the target and preparing of self-cleaning electrode interfaces.

Advances in Applications of Molecular Logic Gates

Logic gates are devices that can perform Boolean logic operations and are the basic components of integrated circuits for information processing and storage. In recent years, molecular logic gates are gradually replacing traditional silicon-based electronic computers with their significant advantages and are used in research in water quality monitoring, heavy metal ion detection, disease diagnosis and treatment, food safety detection, and biological sensors. Logic gates at the molecular level have broad development prospects and huge development potential. In this review, the development and application of logic gates in various fields are used as the entry point to discuss the research progress of logic gates and logic circuits. At the same time, the application of logic gates in quite a few emerging fields is briefly summarized and predicted.

Smart and Functionalized Development of Nucleic Acid-Based Hydrogels: Assembly Strategies, Recent Advances, and Challenges

Nucleic acid-based hydrogels that integrate intrinsic biological properties of nucleic acids and mechanical behavior of their advanced assemblies are appealing bioanalysis and biomedical studies for the development of new-generation smart biomaterials. It is inseparable from development and incorporation of novel structural and functional units. This review highlights different functional units of nucleic acids, polymers, and novel nanomaterials in the order of structures, properties, and functions, and their assembly strategies for the fabrication of nucleic acid-based hydrogels. Also, recent advances in the design of multifunctional and stimuli-responsive nucleic acid-based hydrogels in bioanalysis and biomedical science are discussed, focusing on the applications of customized hydrogels for emerging directions, including 3D cell cultivation and 3D bioprinting. Finally, the key challenge and future perspectives are outlined.

An intensive and glow-type chemiluminescence of luminol-embedded, guanosine-derived hydrogel

In this paper, an intensive and glow-type chemiluminescence (CL) hydrogel was prepared by simultaneous incorporation of chemiluminescence reagent (luminol) and catalytic cofactor (hemin) into the scaffold of guanosine-derived hydrogel. The self-assembled hydrogel consisted of K⁺ stabilized hemin/G-quartet structures, showing significant enzyme-like activity to H₂O₂-mediated oxidation of luminol. After adding H₂O₂ into the hydrogel, blue light visible to naked eyes would come into being and last for over 8 h. The lasting-time CL emission of hydrogel was achieved due to a mechanism of slow-diffusion-controlled heterogeneous catalysis. Moreover, this self-assembled hydrogel performed a good response to H₂O₂ and the CL emission images could be recorded by smartphone. The hydrogel could remain excellent lifetime stability for months and the stable, enhanced and glow-type CL emission could improve the reliability and precision of CL detection, which has a promising application in cold light source and H₂O₂ detection of real biological samples.

Morphological Manipulation of DNA Gel Microbeads with Biomolecular Stimuli

Hydrogels are essential in many fields ranging from tissue engineering and drug delivery to food sciences or cosmetics. Hydrogels that respond to specific biomolecular stimuli such as DNA, mRNA, miRNA and small molecules are highly desirable from the perspective of medical applications, however interfacing classical hydrogels with nucleic acids is still challenging. Here were demonstrate the generation of microbeads of DNA hydrogels with droplet microfluidic, and their morphological actuation with DNA strands. Using strand displacement and the specificity of DNA base pairing, we selectively dissolved gel beads, and reversibly changed their size on-the-fly with controlled swelling and shrinking. Lastly, we performed a complex computing primitive-A Winner-Takes-All competition between two populations of gel beads. Overall, these results show that strand responsive DNA gels have tantalizing potentials to enhance and expand traditional hydrogels, in particular for applications in sequencing and drug delivery.

Review of recent progress on DNA-based biosensors for Pb2+ detection

Lead (Pb) is a highly toxic heavy metal of great environmental and health concerns, and interestingly Pb²⁺ has played important roles in nucleic acids chemistry. Since 2000, using DNA for selective detection of Pb²⁺ has become a rapidly growing topic in the analytical community. Pb²⁺ can serve as the most active cofactor for RNA-cleaving DNAzymes including the GR5, 17E and 8-17 DNAzymes. Recently, Pb²⁺ was found to promote a porphyrin metalation DNAzyme named T30695. In addition, Pb²⁺ can tightly bind to various G-quadruplex sequences inducing their unique folding and binding to other molecules such as dyes and hemin. The peroxidase-like activity of G-quadruplex/hemin complexes was also used for Pb²⁺ sensing. In this article, these Pb²⁺ recognition mechanisms are reviewed from fundamental chemistry to the design of fluorescent, colorimetric, and electrochemical biosensors. In addition, various signal amplification mechanisms such as rolling circle amplification, hairpin hybridization chain reaction and nuclease-assisted methods are coupled to these sensing methods to drive up sensitivity. We mainly cover recent examples published since 2015. In the end, some practical aspects of these sensors and future research opportunities are discussed.

Construction of Supramolecular Organogel with Circularly Polarized Luminescence by Self-Assembled Guanosine Octamer

Gel formation using guanosine self-assembly is an important process in supramolecular chemistry. Here, we report the stepwise construction of circularly polarized luminescent supramolecular organogels from self-assembled guanosine quadruplexes. A lipophilic guanosine derivative (aldG) is designed and synthesized for the formation of a well-defined G8-octamer. The diamine linkers are used to connect G8-octamer units by imine formation to facilitate the construction of the supramolecular gel networks. 1H NMR experiments show that the pre-assembled aldG8-octamer remains intact and is crucial for transparent and stiff organogel formation. With extended conjugation, the aldG organogels exhibit strong green fluorescence emission and circularly polarized properties without the assistance of any external fluorescent dyes, suggesting an alternative approach to construct molecular probes for biological and material applications.

Metal ions confinement defines the architecture of G-quartet, G-quadruplex fibrils and their assembly into nematic tactoids

G-quadruplex, assembled from a square array of guanine (G) molecules, is an important structure with crucial biological roles in vivo but also a versatile template for ordered functional materials. Although the understanding of G-quadruplex structures is the focus of numerous studies, little is known regarding the control of G-quartet stacking modes and the spontaneous orientation of G-quadruplex fibrils. Here, the effects of different metal ions and their concentrations on stacking modes of G-quartets are elucidated. Monovalent cations (typically K+) facilitate the formation of G-quadruplex hydrogels with both heteropolar and homopolar stacking modes, showing weak mechanical strength. In contrast, divalent metal ions (Ca2+, Sr2+, and Ba2+) at given concentrations can control G-quartet stacking modes and increase the mechanical rigidity of the resulting hydrogels through ionic bridge effects between divalent ions and borate. We show that for Ca2+ and Ba2+ at suitable concentrations, the assembly of G-quadruplexes results in the establishment of a mesoscopic chirality of the fibrils with a regular left-handed twist. Finally, we report the discovery of nematic tactoids self-assembled from G-quadruplex fibrils characterized by homeotropic fibril alignment with respect to the interface. We use the Frank-Oseen elastic energy and the Rapini-Papoular anisotropic surface energy to rationalize two different configurations of the tactoids. These results deepen our understanding of G-quadruplex structures and G-quadruplex fibrils, paving the way for their use in self-assembly and biomaterials.

Engineered Dynamic Boronate Ester-Mediated Self-Healable Biocompatible G-Quadruplex Hydrogels for Sustained Release of Vitamins

Injectable, self-healable, and biocompatible dynamic hydrogels prepared from the molecular self-assembly and reversible covalent bond formation of low-molecular-weight hydrogelators are increasing in the field of drug delivery. Herein, we report the formation of G-quadruplex hydrogels via the multicomponent self-assembly and reversible bond formation between guanosine (G) and 1-naphthaleneboronic acid in the presence of the monovalent cation K⁺. The cation-templated stacking interaction of G4 quartets and the formation of dynamic cyclic boronate esters are responsible for the construction of dynamic G-quadruplex assembly. The in situ-synthesized dynamic cyclic boronate esters are well characterized by ¹¹B nuclear magnetic resonance and Fourier transform infrared spectroscopy methods. The formation and morphology of the G-quadruplex hydrogel are well supported by several spectroscopic and microscopic techniques. The injectability and self-healing ability of the G-quadruplex hydrogel are also investigated. The in vivo cytotoxicity of the G-quadruplex hydrogel is extensively evaluated over different cell lines (HeLa, MCF-7, and HEK293) to observe the biostability and broad-spectrum biocompatibility of the hydrogel. Further, this injectable, biocompatible G-quadruplex hydrogel has been used for encapsulation and sustained release of two important vitamins (B₂ and B₁₂) over 40 h at physiological pH (7.46) and temperature (37 °C) without the influence of any external stimuli.

Transforming sustained release into on-demand release: self-healing guanosine–borate supramolecular hydrogels with multiple responsiveness for Acyclovir delivery

Supramolecular hydrogels derived from natural nucleoside have promising applications for on-demand drug release with controlled on/off switch and adjustable release kinetics in response to various stimuli.

Self-Assembly of Metallo-Nucleoside Hydrogels for Injectable Materials That Promote Wound Closure

Injectable hydrogels are increasingly being used as scaffolds for in situ tissue engineering and wound healing. Most of these injectable hydrogels are made from polymers, and there are fewer examples of such soft materials made via self-assembly of low-molecular weight gelators. We report the room-temperature synthesis of a functional hydrogel formed by mixing cytidine (C) with 0.5 equiv each of B(OH)₃ and AgNO₃. The structural basis for this supramolecular hydrogel (C-B-C·Ag⁺) involves orthogonal formation of cytidine borate diesters (C-B-C) and Ag⁺-stabilized C-C base pairs, namely, the C·Ag⁺·C dimer. The C-B-C·Ag⁺ hydrogels, which can have high water content (at least 99.6%), are stable (no degradation after 1 year in the light), stimuli-responsive, and self-supporting, with elastic moduli of up to 10⁴ Pa. Incorporation of Ag⁺ ions into the gel matrix endows the C-B-C·Ag⁺ hydrogel with significant antibacterial capability. Importantly, the rapid switching between the sol and gel states for this supramolecular hydrogel, as a response to shear stress, enables 3D printing of a flexible medical patch made from the C-B-C·Ag⁺ hydrogel. The C-B-C·Ag⁺ hydrogel was used to promote the closure of burn wounds in a mouse model.

MIL-61 and Eu3+@MIL-61 as Signal Transducers To Construct an Intelligent Boolean Logical Library Based on Visualized Luminescent Metal-Organic Frameworks

MIL-61 and its postsynthesis product (Eu³⁺@MIL-61) are employed as signal transducers to construct a series of basic logic gates (NOT, NAND, INHIBIT, and XNOR) on account of their simple synthetic process and fascinating luminescent properties. Also, a two-output combinational logic gate and a cascaded logic gate can be constructed on these two signal transducers by changing the inputs. In this logic gate library system, the fluorescence of MIL-61 (λ_395nm) or Eu³⁺@MIL-61 (λ_615nm) is used as outputs with a threshold of 0.5. The advantage of this boolean logical library is that the two signal transducers are readily available and cost effective. In addition, the luminescence change is visible to the naked eye under a UV lamp, which is more convenient in application. More importantly, it presents a new route for the design of a molecular logic gate library based on luminescent metal-organic frameworks. And for further application, we experimentally construct two logic devices (a 4-to-2 encoder and a parity checker) based on Eu³⁺@MIL-61 to perform nonarithmetic information.

DNAzyme Catalyzed Tyramide Depositing Reaction for In Situ Imaging of Protein Status on the Cell Surface

Effective characterization of protein biomarkers status on the cell surface has important value in the diagnosis and treatment of diseases. Traditional immunohistochemistry can only assess the protein expression level rather than accurately reflect their interaction and oligomerization, resulting in inevitable problems for personalized therapy.

Methods: Herein, we developed a novel DNAzyme-catalyzed tyramide depositing reaction (DCTDR) for in situ amplified imaging of membrane protein status. By using human epidermal growth factor receptor 2 (HER2) as model, the binding of HER2 proteins with specific aptamers induced the formation of activated hemin/G-quadruplex (G4) DNAzyme on the cell surface to catalyze the covalent deposition of fluorescent tyramide on the membrane proteins for fluorescence imaging.

Results: The DCTDR-based imaging can conveniently characterize total HER2 expression and HER2 dimerization on the breast cancer cell surface with the application of aptamer-G4 probes and proximity aptamer-split G4 probes, respectively. The designed DCTDR strategy was successfully applied to quantitatively estimate total HER2 expression and HER2 homodimer on clinical breast cancer tissue sections with high specificity and accuracy.

Conclusion: The DCTDR strategy provides a simple, pragmatic and enzyme-free toolbox to conveniently and sensitively analyze protein status in clinical samples for improving clinical research, cancer diagnostics and personalized treatment.

Engineering Nanozymes Using DNA for Catalytic Regulation

DNA treatment of metal nanoparticles provides a potent tool for tuning their native properties and constructing advanced materials. However, there have been limited studies on interactions between DNA and nanomaterial-based artificial enzymes (nanozymes) to influence their intrinsic peroxidase-like properties. Here, we present the utilization of DNA as a capping ligand to engineer various bio-nanointerfaces for high-precise and adjustable regulation of catalytic behaviors of nanozymes toward the oxidation of substrates. The treatment of stiff double-stranded DNA only induced a negligible enhancement of the catalytic activity of nanozymes, and both coil-like single-stranded DNA and hairpin DNA-capped nanoparticles produced a medium signal increase. Interestingly, hybridization chain reaction (HCR) product-treated nanoparticles showed the highest peroxidase-like activities among four DNA structures. Furthermore, significant parameters that influence HCR process and the modulation of catalysis, such as the concentration of the hairpin DNA, the ionic strength, and the amount of nanozyme, were also systematically investigated. On the basis of HCR amplification and iron oxide (Fe₃O₄) nanoparticles, we develop a simple, fast, label-free, and sensitive colorimetric strategy for sensing of a Yersinia pestis-relevant DNA sequence with a detection limit as low as 100 pM as well as single nucleotide polymorphism discrimination. These results highlight DNA engineering as a facile strategy to regulate the catalytic activities of nanozymes and understand the interactions between metallic nanoparticles and nucleic acids for biosensing applications.

Hydrodynamic Layer-by-Layer Assembly of Transferable Enzymatic Conductive Nanonetworks for Enzyme-Sticker-Based Contact Printing of Electrochemical Biosensors

Realizing high-performance electrochemical biosensors in a simple contact-printing-based approach significantly increases the applicability of integrated flexible biosensors. Herein, an enzyme-sticker-based approach that enables flexible and multielectrochemical sensors via simple contact-transfer printing is reported. The enzyme sticker consists of an enzymatic conductive network film and a polymeric support. The enzyme-incorporated nanostructured conductive network showing an efficient electrical coupling was assembled via the hydrodynamic layer-by-layer assembly of redox enzymes, polyelectrolytes, single-walled carbon nanotubes, and a biological glue material, M13 phage. The enzymatic conductive network on a polymeric membrane support was facilely wet contact-transfer printed onto integrated electrode systems by exploiting varying degrees of hydrophilicity displayed by the enzymatic electronic film, polymeric support, and receiving electrodes of the sensor system. The glucose sensors fabricated using the enzyme sticker detected glucose at a concentration of as low as 35 μM and showed high selectivity and stability. Furthermore, a flexible dual-sensor array capable of detecting both glucose and lactate was demonstrated using the versatile enzyme sticker concept. This work presents a new route toward assembling and integrating hybrid nanomaterials with efficient electrochemical coupling for high-performance biosensors and health-monitoring devices as well as for emerging bioelectronics and electrochemical devices.

Nanogel-Incorporated Injectable Hydrogel for Synergistic Therapy Based on Sequential Local Delivery of Combretastatin-A4 Phosphate (CA4P) and Doxorubicin (DOX)

Drug combination therapies employing dual-drug delivery systems offer an effective approach to reduce disadvantages of single-drug therapy, such as high dose and easy generation of drug resistance. Herein, a dual-drug delivery system based on nanogel-incorporated injectable hydrogel (NHG) was designed for sequential local delivery of combretastatin-A4 phosphate (CA4P) and doxorubicin (DOX) for antiangiogenesis and anticancer combination therapy. The injectable hydrogel was prepared for loading and quick release of hydrophilic drug CA4P, while the pH and redox stimuli-responsive nanohydrogels were incorporated into the injectable hydrogel by pH-responsive boronate ester bond for sustained long-term DOX delivery. The dual-drug-loaded NHG system released CA4P and DOX sequentially and exhibited high inhibitory activities on the cancer cell proliferation in vitro. It displayed superior therapeutic efficacy in vivo with only one single injection. Immunohistochemistry analyses suggested a synergistic therapeutic effect through tumor vascular collapse caused by CA4P and tumor cell apoptosis induced by DOX. The combination therapy of antiangiogenic and cytotoxic drugs using NHG delivery system offers a promising approach for improved cancer therapeutic efficacy. The nanogel-embedded injectable hydrogel can be employed as a universal drug carrier for local dual-drug delivery with sequential release behaviors by simple injection.

Framework-Nucleic-Acid-Enabled Biosensor Development

Nucleic acids have been actively exploited to develop various exquisite nanostructures due to their unparalleled programmability. Especially, framework nucleic acids (FNAs) with tailorable functionality and precise addressability hold great promise for biomedical applications. In this review, we summarize recent progress of FNA-enabled biosensing in homogeneous solutions, on heterogeneous surfaces, and inside cells. We describe the strategies to translate the structural order and rigidity of FNAs to interfacial engineering with high controllability, and approaches to realize multiplexing for highly parallel in vitro detection. We also envision the marriage of the currently available FNA tool sets with other emerging technologies to develop a new generation of biosensors for precision diagnosis and bioimaging.

Guanosine-Derived Supramolecular Hydrogels: Recent Developments and Future Opportunities

Hydrogels are attractive materials for designing sensors, catalysts, scaffolds for tissue engineering, stimuli responsive soft materials, and controlled-release drug delivery systems. In recent years, self-assembly of guanosine and its derivatives has received immense interests for devising programmable supramolecular biomaterials including hydrogels. This perspective highlights some of the history and the recent developments of guanosine-based supramolecular hydrogels and their applications. Future prospects and scope of the guanosine-based hydrogels have also been discussed.

A G4·K+ hydrogel made from 5′-hydrazinoguanosine for remediation of α,β-unsaturated carbonyls

A G₄·KCl hydrogel with a nucleophilic 5′ sidechain absorbs α,β-unsaturated carbonyls via formation of cyclic adducts.