Hydrogels Based on Ag+ -Modulated Assembly of 5'-Adenosine Monophosphate for Enriching Biomolecules

Cobalt-Adenosine Monophosphate Supramolecular Hydrogel with pH-Responsive Multi-Nanozymatic Activity

Self-assembled metal-ion cross-linked multifunctional hydrogels are gaining a lot of attention in the fields of biomedical and biocatalysis. Herein, we report a heat-triggered metallogel that was spontaneously formed by the self-assembly of adenosine 5'-monophosphate (AMP) and cobalt chloride, accompanied by a color transition depicting an octahedral to tetrahedral transition at high temperature. The hydrogel shows excellent stability in a wide pH window from 1 to 12. The metallogel is being exploited as a multienzyme mimic, exhibiting pH-responsive catalase and peroxidase activity. Whereas catalase mimicking activity was demonstrated by the hydrogel under neutral and basic conditions, it shows peroxidase mimicking activity in an acidic medium. The multifunctionality of the synthesized metallogel was further demonstrated by phenoxazinone synthase-like activities. Owing to its catalase-mimicking activity, the metallogel could effectively reduce the oxidative stress produced in cells due to excess hydrogen peroxide by degrading H2O2 to O2 and H2O under physiological conditions. The biocompatible metallogel could prevent cell apoptosis by scavenging reactive oxygen species. A green and simple synthetic strategy utilizing commonly available biomolecules makes this metallogel highly attractive for catalytic and biomedical applications.

Optimization of guanosine-based hydrogels with boric acid derivatives for enhanced long-term stability and cell survival

Tissue defects can lead to serious health problems and often require grafts or transplants to repair damaged soft tissues. However, these procedures can be complex and may not always be feasible due to a lack of available tissue. Hydrogels have shown potential as a replacement for tissue grafts due to their ability to support cell survival and encapsulate biomolecules such as growth factors. In particular, guanosine-based hydrogels have been explored as a potential solution, but they often exhibit limited stability which hampers their use in the biofabrication of complex grafts. To address this issue, we explored the use of borate ester chemistry and more complex boric acid derivatives to improve the stability and properties of guanosine-based hydrogels. We hypothesized that the aromatic rings in these derivatives would enhance the stability and printability of the hydrogels through added π-π stack interactions. After optimization, 13 compositions containing either 2-naphthylboronic acid or boric acid were selected. Morphology studies shows a well-defined nanofibrilar structure with good printable properties (thixotropic behaviour, print fidelity and printability). Moreover, the pH of all tested hydrogels was within the range suitable for cell viability (7.4–8.3). Nevertheless, only the boric acid-based formulations were stable for at least 7 days. Thus, our results clearly demonstrated that the presence of additional aromatic rings did actually impair the hydrogel properties. We speculate that this is due to steric hindrance caused by adjacent groups, which disrupt the correct orientation of the aromatic groups required for effective π-π stack interactions of the guanosine building block. Despite this drawback, the developed guanosine-boric acid hydrogel exhibited good thixotropic properties and was able to support cell survival, proliferation, and migration. For instance, SaOS-2 cells planted on these printed structures readily migrated into the hydrogel and showed nearly 100% cell viability after 7 days. In conclusion, our findings highlight the potential of guanosine-boric acid hydrogels as tissue engineering scaffolds that can be readily enhanced with living cells and bioactive molecules. Thus, our work represents a significant advancement towards the development of functionalized guanosine-based hydrogels.

Nucleoside-Based Supramolecular Hydrogels: From Synthesis and Structural Properties to Biomedical and Tissue Engineering Applications

Supramolecular hydrogels are of great interest in tissue scaffolding, diagnostics, and drug delivery due to their biocompatibility and stimuli-responsive properties. In particular, nucleosides are promising candidates as building blocks due to their manifold noncovalent interactions and ease of chemical modification. Significant progress in the field has been made over recent years to allow the use of nucleoside-based supramolecular hydrogels in the biomedical field, namely drug delivery and 3D bioprinting. For example, their long-term stability, printability, functionality, and bioactivity have been greatly improved by employing more than one gelator, incorporating different cations, including silver for antibacterial activity, or using additives such as boric acid or even biomolecules. This now permits their use as bioinks for 3D printing to produce cell-laden scaffolds with specified geometries and pore sizes as well as a homogeneous distribution of living cells and bioactive molecules. We have summarized the latest advances in nucleoside-based supramolecular hydrogels. Additionally, we discuss their synthesis, structural properties, and potential applications in tissue engineering and provide an outlook and future perspective on ongoing developments in the field.

Regenerative antibacterial hydrogels from medicinal molecule for diabetic wound repair

Hydrogel products for chronic diabetic wounds, a serious and prevalent complication of diabetes, show limited effects on disability and remain nonspecific. Thus, improvements in the usage of pharmaceutical molecule in the hydrogels are highly desirable to increase the therapeutic effect of hydrogels. In this study, thioctic acid (a common medicine molecule in diabetes treatment) is used for preparing regenerative antibacterial hydrogels (RAH) which contains in situ synthesized silver nanoparticles (AgNPs). The RAH shows regenerative, self-healing and injectable ability, because of the reversible hydrogen and coordination bonds. With good regenerative capacity, RAH can be stored as powder to avoid the water loss and facilitate storage availability. Owing to the antioxidant properties of thioctic acid, the RAH can decrease the oxidative damage and retain cell proliferation efficiency. Due to the in situ synthesized AgNPs, the RAH also exhibits extraordinary antimicrobial capacities against MDR bacteria. All of these superiorities enable RAH to be a promising therapy for chronic diabetic wounds.

Electrostatically Directed Long-Range Self-Assembly of Nucleotides with Cationic Nanoparticles To Form Multifunctional Bioplasmonic Networks

Precise control over interparticle interactions is essential to retain the functions of individual components in a self-assembled superstructure. Here, we report the design of a multifunctional bioplasmonic network via an electrostatically directed self-assembly process involving adenosine 5'-triphosphate (ATP). The present study unveils the ability of ATP to undergo a long-range self-assembly in the presence of cations and gold nanoparticles (AuNP). Modelling and NMR studies gave a qualitative insight into the major interactions driving the bioplasmonic network formation. ATP-Ca²⁺ coordination helps in regulating the electrostatic interaction, which is crucial in transforming an uncontrolled precipitation into a kinetically controlled aggregation process. Remarkably, ATP and AuNP retained their inherent properties in the multifunctional bioplasmonic network. The generality of electrostatically directed self-assembly process was extended to different nucleotide-nanoparticle systems.

A portable visual coffee ring based on carbon dot sensitized lanthanide complex coordination to detect bisphenol A in water

In this work, a ratiometric fluorescence sensor along with a portable coffee ring visualized detection method for bisphenol A (BPA) was developed based on carbon dots. The probe was formed by the coordination polymerization of Eu3+ and 5'-adenosine monophosphate on the surface of carbon dots containing a large number of hydroxyl and carbonyl groups. The results showed that the fluorescence intensity ratio and the concentration of BPA had a good linear relationship in a wide range of 0.1-100 μM with a detection limit of 20 nM (S/N = 3). The recoveries of the added standard BPA in water samples ranged from 91.80 to 102.7% with relative standard deviation values no more than 1.84% (n = 3). In addition, the changes of the fluorescence color of the CDs@Eu-AMP suspension with different BPA concentrations can be easily visualized under a UV lamp by the naked eye, which highlights the great potential of the coffee ring detection method for the fast and convenient monitoring of BPA in real water samples.

Development, Preparation, and Biomedical Applications of DNA-Based Hydrogels

Hydrogels have outstanding research and application prospects in the biomedical field. Among them, the design and preparation of biomedical hydrogels with deoxyribonucleic acid (DNA) as building blocks have attracted increasing research interest. DNA-based hydrogel not only has the skeleton function of hydrogel, but also retains its biological functions, including its excellent selection specificity, structural designability, precise molecular recognition ability, outstanding biocompatibility, and so on. It has shown important application prospects in the biomedical field, such as drug delivery, biosensing, and tissue engineering. In recent years, researchers have made full use of the characteristics of DNA molecules and constructed various pure DNA-based hydrogels with excellent properties through various crosslinking methods. Moreover, via introducing functional molecules or elements, or combining with other functional materials, a variety of multifunctional DNA-based hybrid hydrogels have also been constructed, which expand the breadth and depth of their applications. Here, we described the recent development trend in the area of DNA-based hydrogels and highlighted various preparation methods of DNA-based hydrogels. Representative biomedical applications are also exemplified to show the high performance of DNA-based hydrogels. Meanwhile, the existing problems and prospects are also summarized. This review provided references for the further development of DNA-based hydrogels.

Smart soft supramolecular hybrid hydrogels modulated by Zn2+/Ag NPs with unique multifunctional properties and applications

The development of low molecular weight molecule-mediated biocompatible soft supramolecular hydrogels, considered to be next-generation materials for biomedical applications, is a challenging task. In this context, the present work reports the synthesis of the hybrid hydrogel (CISZ2H) comprising ternary nanohybrids (Zn2+-Ag NPs@β-FeOOH@5'-CMP), consisting of greener components as a building block with hydrophobic tail (containing Zn2+ ions, Ag NPs, and β-FeOOH) and hydrophilic head (5'-cytidine monophosphate (5'-CMP)). The presence of Zn2+ ions and Ag NPs in the nanohybrids introduces new coordination sites and induces the puckering of the ribose sugar in 5'-CMP to generate the solid-like network in the self-assembly via micellar formation involving building blocks. Extensive cross-linking among organic and inorganic moieties provide these hydrogels with unique physicochemical features of improved mechanical strength (∼71 000 Pa), large water retention capability (600%), self-healing, and injectability as arrived at by thixotropic measurements, low toxicity, and enhanced drug/dye loading capabilities. Thus, the co-doped Zn2+ ions and Ag NPs in CISZ2H impart it with enhanced mechanical stability, shear thinning, external stimuli-responsiveness (pH and temperature), sustained slow drug release, surface enhanced Raman scattering (SERS) activity, and antibacterial features, thereby making this hydrogel safer for drug delivery, wound healing, sensing, and tissue engineering. The excellent features of the as-synthesized hydrogels make it a smart soft material for advanced applications with enormous future potential.

Hybrid Hydrogel Electrolyte Based on Metal-Organic Supermolecular Self-Assembly and Polymer Chemical Cross-Linking for Rechargeable Aqueous Zn-MnO2 Batteries

Multifunctional metal-organic supramolecular hydrogels have achieved great progress nowadays. However, their applications in aqueous batteries for flexible energy storage devices remain limited due to their unsatisfactory mechanical properties. Here, we report a rapid formation of supramolecular hydrogel by adenosine 5'-monophosphate (AMP) and manganese ions (Mn²⁺). Additionally, the AMP-Mn hydrogel is combined with chemical cross-linking poly(vinyl alcohol) (PVA) polymer networks to form an AMP-Mn/PVA hybrid hydrogel, which effectively solves the problems with regard to the mechanical properties and stability of metal-organic supramolecular hydrogels as well as self-healing of tough chemical cross-linking polymer networks. The AMP-Mn/PVA hybrid hydrogel served as the hydrogel electrolyte to fabricate flexible Zn-MnO₂ batteries, which exhibit fast ion conductivity, excellent electrochemical stability, and robust mechanical strength, indicating feasible practical application prospects. This investigation provides a promising opportunity for the application of metal-organic supramolecular hydrogels in the field of energy storage.

Multistimulus-Responsive Supramolecular Hydrogels Derived by in situ Coating of Ag Nanoparticles on 5'-CMP-Capped β-FeOOH Binary Nanohybrids with Multifunctional Features and Applications

The present manuscript reports the synthesis of multistimulus-responsive smart supramolecular hydrogels derived by in situ coating of silver nanoparticles (Ag NPs) on colloidal cytidine-5'-monophosphate-capped β-FeOOH nanohybrids (β-FeOOH@5'-CMP) under physiological conditions forming a polycrystalline building block (Ag-coated β-FeOOH@5'-CMP). The presence of Ag in the binary nanohybrids induces the puckering of ribose sugar, bringing a change in its conformation from C2'-endo to C3'-endo, which enhanced the supramolecular interactions among different moieties of other building blocks to construct a porous network of hydrogels in the self-assembly via the formation of a micellar structure. Such a supramolecular network in hydrogel is also evidenced by the reversible sol⇌gel transformation under multistimulus-responsiveness in a narrow range of pH, temperature, and sonication, as well as by the manifestation of rapid self-healing and injectability features. As-synthesized hydrogels exhibiting shear-thinning behavior under higher strain and converting back into the sol under low strain, suggests their potential for localized drug delivery. The presence of Ag NPs in the hydrogel enhanced its viscoelastic properties, % swelling (580) and loading capabilities (590 mg g^-1) for methylene blue (MB), and its controlled release over days (∼2-30) as a function of pH. It displayed excellent surface-enhanced Raman spectroscopy activity allowing to detect MB-like drug molecules at ≤10^-12 M. Thus, the as-synthesized hydrogels represent a unique superparamagnetic nanosystem consisting of all greener components (5'-CMP/β-FeOOH/Ag) with superior viscoelastic, sensing, and antimicrobial properties, displaying multistimulus-responsiveness (pH/temperature/sonication), thereby suggesting their vast potential for biomedical and environmental applications.

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.

Can the solvent enhance the rate of chemical reactions through C-H/π interactions? insights from theory

The current computational study with density functional theory (DFT) shows that the rate of chemical reactions can be influenced through non-covalent C-H/π interactions between substrates and the solvent. It is shown that intramolecular carbon-carbon interaction and CO2 activation by a low valent silicon complex are both favourably affected by the explicit presence of the solvent toluene, due to C-H/π interactions between toluene and the silicon complex. Furthermore, ab initio molecular dynamics (AIMD) simulations demonstrate that even if the C-H/π interacting solvent molecule is displaced from the complex, another would quickly take its place, thus maintaining the interaction. Hence, the current work shows how non-covalent interactions between solvent and substrate can enhance the rate of the reaction and expands our understanding of the role and influence of the solvent in effecting important chemical transformations.

In-situ generation of nanozymes by natural nucleotides: a biocatalytic label for quantitative determination of hydrogen peroxide and glucose

Four natural nucleotides including 5'-cytidine monophosphate (CMP), 5'-thymidine monophosphate (TMP), guanosine monophosphate (GMP) and 5'-adenosine monophosphate (AMP) were employed to modulate the coordination environment and the valence state of PtCl₄^2-. This is the first report that natural nucleotides have the ability to produce highly active Pt nanoclusters. The latter are shown to act as peroxidase mimetics. Both the size distribution and the charge state of Pt-nucleotide nanozymes vary with the chemical structures of nucleotides, thereby contributing to distinct enzyme-like activities. By adopting Pt-CMP as a signal amplifier, a photometric assay was well-established for quantitative determination of glucose. The assay is based on the oxidation of glucose by glucose oxidase. The oxidation product (H₂O₂) is detected at 652 nm via the Pt-CMP-catalyzed oxidation of 3,3',5,5'-tetramethylbenzidine with H₂O₂. Response is linear in the 5 to 100 μM glucose concentration range, and the limit of detection is 0.12 μM (at S/N= 3). The method excels by a low signal background, high sensitivity, and low consumption of energy and materials. Graphical abstract Peroxidase mimicking Pt nanoclusters were synthesized by employing natural nucleotides as both the reducing agent and the stabilization template.

Environmentally benign pH-responsive cytidine-5′-monophosphate molecule-mediated akaganeite (5′-CMP-β-FeOOH) soft supramolecular hydrogels induced by the puckering of ribose sugar with efficient loading/release capabilities

A novel synthetic protocol for environmentally benign 5′-CMP-β-FeOOH soft hydrogels exhibiting a rapid pH-responsive reversible sol–gel transition, efficient adsorption and slow release capabilities is reported.

Balancing ionic and H-bonding interactions for the formation of Au(i) hydrometallogels

Complex [Au(⁹N-adenine)(PMe₃)](CF₃CO₂) displays a supramolecular structure built up through ionic, π-stacking, C–H⋯O, C–H⋯N and C–H⋯Au interactions. This complex forms a stable hydrometallogel consisting of straight molecular nanowires.

Magnetic networks of carbon quantum dots and Ag particles

Self-assembly exploits a facile non-covalent way to couple structurally different building blocks for creating soft materials with synergetic novel properties and functions. Taking advantage of magneto-properties from magnetic surfactants as well as versatile functional ligand formed by carbon quantum dots with cysteine (cys-CQDs), the magnetic network materials were firstly constructed by using magnetic surfactants and cys-CQDs as self-assembly building blocks. Counterions of Br^-, [GdCl₃Br]^-, [HoCl₃Br]^- in surfactants could control the morphology of magnetic network structures, and the concentration of magnetic surfactants manoeuvres a versatile scenario of self-assembly behavior. Self-assembly of cys-CQDs and CTAHo brought out a 10-fold increase in magnetic moment of CTAHo. The fluorescent property of carbon quantum dots firstly served as an effective indicator element to dissect the collective effect in self-assembly process. For the sake of capturing the target sequence-specific DNA molecules, in situ growth of Ag nanoparticles (AgNPs) upon the magnetic network structures was realized by synergetically electrostatic and coordinated interaction of carboxyl groups and Ag ions. The magnetic Ag self-assemblies anchored thiol-containing DNA, serving as a magnetic separation booster for the target sequence-specific DNA molecules under an applied magnetic field, which will bring light on designing magneto-functional self-assembly materials according to practical application requirements.

Discotic Organic Gelators in Ion Sensing, Metallogel Formation, and Bioinspired Catalysis

Two organogelators G2 and G3 with a carboxamide group have been synthesized and characterized with different spectroscopic tools. Dimethylformamide or dimethyl sulfoxide solutions of both the compounds upon the addition of a minute quantity of water show the tendency to form gels. Supramolecular self-assembly for gel formation paves the way for aggregation-induced emission enhancement (AIEE) phenomena for both the gelator molecules. Introduction of metal ions in organogels strengthens the gel property without much affecting the fluorescence behavior. However, the introduction of Ag⁺, Fe²⁺, and Fe³⁺ ions in the G2 organogel separately results in total quenching of AIEE, making it possible to sense that particular cation in the gel state. The G3 organogel shows a similar behavior with the Fe²⁺ ion. Remarkably, other metallogels such as Ni(II)G2 and Co(II)G2 can sense sulfide ion and Cu(II)G2 can sense iodide ion by switching off the fluorescence even in multianalyte conditions. Furthermore, the copper-based metallogel Cu(II)G2 can be utilized as a catalyst and reaction medium for aerobic oxidation of catechol to quinone. To the best of our knowledge, this is the first attempt known so far to utilize a metallogel material for bioinspired catalysis such as catechol oxidation.