Robust Hydrogels from Lanthanide Nucleotide Coordination with Evolving Nanostructures for a Highly Stable Protein Encapsulation

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.

Colorimetric immunoassay of carcinoembryonic antigen based on the glucose oxidase/MnO2 nanosheet cascade reaction with self-supplying oxygen

The detection of carcinoembryonic antigen (CEA) has profound implications in cancer diagnostics and therapeutic monitoring. In this work, we developed a colorimetric immunoassay for the detection of CEA. This assay involves the utilization of zinc(II)-based coordination polymers (ZnCPs) as a host for integrating glucose oxidase (GOx) and anti-carcinoembryonic antigen antibody (anti-CEA), which results in the formation of a detection antibody (anti-CEA/GOx@ZnCPs). The adaptable inclusion properties of ZnCPs enable the preservation of the original catalytic behavior of GOx and antigen capture ability of anti-CEA. Consequently, the anti-CEA/GOx@ZnCPs can act as a detection antibody to facilitate the development of an immunoassay. The combination of anti-CEA/GOx@ZnCPs in the immunoassay triggers a cascade reaction involving GOx and MnO2 nanosheets, leading to the generation of an amplified colorimetric signal through self-supplying oxygen. This colorimetric immunoassay exhibits a linear response ranging from 2 to 180 ng mL-1 CEA and has a detection limit of 50 pg mL-1. The practicality of this colorimetric immunoassay in biological matrices was demonstrated by the successful determination of CEA in serum samples with good recovery and precision. We believe that this study will pave the way to rationally design multifunctional CP-based composites for a wide range of applications in bioanalysis.

Iron-doped cerium/nucleotide coordination polymer as highly efficient peroxidase mimic for colorimetric detection of fluoride ion

A new coordination polymer (Ce-Fe-GMP) with excellent catalytic activity was prepared by a facile route, which was further applied to the detection of F^- with high sensitivity and selectivity. The simple doping of Fe³⁺ into the coordination network can easily modulate the mixing ratio of Ce³⁺ and Ce⁴⁺ in the presence of H₂O₂, which can extremely improve the catalytic ability of Ce-Fe-GMP. Based on the synergistic effect, the Ce-Fe-GMP with dual-active sites shows better peroxidase activity than that of Ce-GMP. In addition, we found that F^- can inhibit the peroxidase activity of Ce-Fe-GMP because of the coordination structure fragmentation and the regulation of Ce³⁺/Ce⁴⁺ ratio. Therefore, different concentrations of F^- can be detected by the colorimetric reaction based on this mechanism. The absorption at 652 nm displays a good linear relationship versus the concentration of F^- over the range 2.0 to 100.0 μM. Furthermore, F^- in real mineral-mixed samples can be measured with satisfactory results. The colorimetric strategy based on the peroxidase activity of Ce-Fe-GMP is simple and low-cost, which shows the potential applications in the field of on-site environment measurement.

Encapsulation of lipases by nucleotide/metal ion coordination polymers: enzymatic properties and their applications in glycerolysis and esterification studies

BACKGROUND

In the present study, lipases of TLL (lipase from Thermomyces lanuginosus), AOL (lipase from Aspergillus oryzae), RML (lipase from Rhizomucor miehei), BCL (lipase from Burkholderia cepacia), CALA (Candida antarctica lipase A) and LU (Lecitase® Ultra) were encapsulated into nucleotide-hybrid metal coordination polymers (CPs). Enzyme concentration was optimized for encapsulation and the enzymatic properties of the obtained lipases were investigated. In addition, their performance in glycerolysis and esterification was evaluated, and glycerolysis conditions (water content, temperature and time) were optimized.

RESULTS

Hydrolysis activity over 10 000 U g^-1 and activity recovery over 90% were observed from AOL@GMP/Tb, TLL@GMP/Tb and RML@GMP/Tb. GMP/Tb encapsulation (of AOL, TLL, RML and LU) improved their thermostability when incubated in air. The encapsulated lipases exhibited moderate [triacylglycerols (TAG) conversion 30-50%] and considerable glycerolysis activity (TAG conversion over 60%). TAG conversions from 69.37% to 82.35% and diacylglycerols (DAG) contents from 58.62% to 64.88% were obtained from CALA@GMP/metal samples (except for CALA@GMP/Cu). Interestingly, none of the encapsulated lipases initiated the esterification reaction. AOL@GMP/Tb, TLL@GMP/Tb, RML@GMP/Tb and CALA@GMP/Tb showed good reusability in glycerolysis, with 88.80%, 94.67%, 89.85% and 78.16% of their initial glycerolysis activity, respectively, remaining after five cycles of reuse. The relationships between temperature and TAG conversion were LnV₀  = 6.5364-3.7943/T and LnV₀  = 13.8820-6.4684/T for AOL@GMP/Tb and CALA@GMP/Tb, respectively; in addition, their activation energies were 31.55 and 53.78 kJ mol^-1 , respectively.

CONCLUSION

Most of the present encapsulated lipases exhibited moderate and considerable glycerolysis activity. In addition, AOL@GMP/Tb, TLL@GMP/Tb, RML@GMP/Tb and CALA@GMP/Tb exhibited good reusability in glycerolysis reactions and potential in practical applications. © 2022 Society of Chemical Industry.

Metal-Organic Enzyme Nanogels as Nanointegrated Self-Reporting Chemobiosensors

A fluorometric glucose biosensor based on fine-tuned chemoenzymatic nanohybrids is herein proposed. The successful integration of an engineered glucose oxidase enzyme and an optically responsive polymeric nanogel in a single entity has led to the fabrication of a highly efficient glucose chemobiosensor. The optical responsiveness has been achieved by the loading of preactivated polymeric hydrogel with fluorescent lanthanide, i.e., cerium (III), cations. A comprehensive investigation of the responsiveness of the biomaterial revealed the interplay between the oxidation state of the cerium lanthanide and the fluorescence emission of the polymer. Finally, a full structural, chemical, and biochemical characterization of the reported system supports the chemobiosensors as robust, specific, and sensitive materials that could be utilized to faithfully quantify the amount of glucose in tear fluids.

Encapsulation of CALB by nucleotide/metal ions coordination nanoparticles: highly selective catalysis of esterification while poor performance in glycerolysis reaction

BACKGROUND

Enzymatic esterification is attracting for particular high-acid oil deacidification. In this study, Candida antarctica lipase B (CALB) was encapsulated into a series of nucleotide-hybrid metal coordination polymers (CPs), which were constructed by guanosine 5'-monophosphate (GMP) and various metals.

RESULTS

We here found that, most of the present CPs encapsulated CALB (CALB@CPs) samples were highly selective for esterification while poor in glycerolysis reaction. They exhibited quite poor performance in glycerolysis, with triacylglycerols (TAGs) conversion lower than 5%, despite this considerable enzymatic hydrolysis activities were observed. However, they (most of them) showed good performance in esterification of fatty acids and glycerol for TAG synthesis. In addition, the GMP/Tb (CPs constructed by GMP and Tb³⁺ ) encapsulated CALB (CALB@GMP/Tb) transformed over 98% of oleic acid into glycerides in the high-acid oil deacidification process, and TAG content from 87 to 89% was obtained. Moreover, the CALB@GMP/Tb showed good reusability in the esterification system.

CONCLUSION

The present CALB@CPs samples are selective for esterification and suitable for high-acid oils deacidification. This work provides a new system for enzymatic selectivity improvement study. © 2021 Society of Chemical Industry.

Tumor-Microenvironment-Responsive Biodegradable Nanoagents Based on Lanthanide Nucleotide Self-Assemblies toward Precise Cancer Therapy

Stimuli-responsive nanoagents, which simultaneously satisfy normal tissue clearance and tumor-specific responsive treatment, are highly attractive for precise cancer theranostics. Herein, we develop a unique template-induced self-assembly strategy for the exquisitely controlled synthesis of self-assembled lanthanide (Ln³⁺ ) nucleotide nanoparticles (LNNPs) with amorphous structure and tunable size from sub-5 nm to 105 nm. By virtue of the low-temperature (10 K) and high-resolution spectroscopy, the local site symmetry of Ln³⁺ in LNNPs is unraveled for the first time. The proposed LNNPs are further demonstrated to possess the ability for highly efficient loading and tumor-microenvironment-responsive release of doxorubicin. Particularly, sub-5 nm LNNPs not only exhibit excellent biocompatibility and predominant renal-clearance performance, but also enable efficient tumor retention. These findings reveal the great potential of LNNPs as a new generation of therapeutic platform to overcome the dilemma between efficient therapy and long-term toxicity of nanoagents for future clinical applications.

Bifunctional heterogeneous catalysts derived from the coordination of adenosine monophosphate to Sn(iv) for effective conversion of sucrose to 5-hydroxymethylfurfural

Adenosine 5′-monophosphate (AMP) with multiple functional groups was used for the synthesis of Sn-AMPs. The Sn-AMPs have both Brønsted acid and Lewis acid sites. The Sn-AMPs demonstrated a superior capability for catalyzing sugars into HMF.

Nucleotide-Tackified Organohydrogel Electrolyte for Environmentally Self-Adaptive Flexible Supercapacitor with Robust Electrolyte/Electrode Interface

Hydrogel electrolytes have attracted enormous attention in flexible and safe supercapacitors. However, the interfacial contact problem between hydrogel electrolyte and electrodes, and the environmental instability are the key factors restricting the development of hydrogel-based supercapacitors. Here, a nucleotide-tackified adhesive organohydrogel electrolyte is successfully constructed and exhibits freezing resistance and water-holding ability based on the water/glycerol binary solvent system. Adenosine monophosphate enables the organohydrogels to possess outstanding adhesion and mechanical robustness. The robust adhesion can ensure close contact between the organohydrogel electrolyte and electrodes for constructing an all-in-one supercapacitor with low interfacial contact resistance. Impressively, the integrated organohydrogel-based supercapacitors display an areal specific capacitance of 163.6 mF cm^-2 . Besides, the supercapacitors feature prominent environmental stability with capacitance retention of 90.6% after 5000 charging/discharging cycles at -20 °C. Furthermore, based on the strong interfacial adhesion, the supercapacitors present excellent electrochemical stability without delamination/displacement between electrolyte and electrodes even under severe deformations such as bending and twisting. It is anticipated that this work will provide an encouraging way for developing flexible energy storage devices with electrochemical stability and environmental adaptability.

Advances and Novel Perspectives on Colloids, Hydrogels, and Aerogels Based on Coordination Bonds with Biological Interest Ligands

This perspective article shows new advances in the synthesis of colloids, gels, and aerogels generated by combining metal ions and ligands of biological interest, such as nucleobases, nucleotides, peptides, or amino acids, among other derivatives. The characteristic dynamism of coordination bonds between metal center and biocompatible-type ligands, together with molecular recognition capability of these ligands, are crucial to form colloids and gels. These supramolecular structures are generated by forming weak van der Waals bonds such as hydrogen bonds or π–π stacking between the aromatic rings. Most gels are made up of nano-sized fibrillar networks, although their morphologies can be tuned depending on the synthetic conditions. These new materials respond to different stimuli such as pH, stirring, pressure, temperature, the presence of solvents, among others. For these reasons, they can trap and release molecules or metal ions in a controlled way allowing their application in drug delivery as antimicrobial and self-healable materials or sensors. In addition, the correct selection of the metal ion enables to build catalytic or luminescent metal–organic gels. Even recently, the use of these colloids as 3D-dimensional printable inks has been published. The elimination of the solvent trapped in the gels allows the transformation of these into metal–organic aerogels (MOAs) and metal–organic xerogels (MOXs), increasing the number of possible applications by generating new porous materials and composites useful in adsorption, conversion, and energy storage. The examples shown in this work allow us to visualize the current interest in this new type of material and their perspectives in the short-medium term. Furthermore, these investigations show that there is still a lot of work to be done, opening the door to new and interesting applications.

Controllable synthesis of two adenosine 5'-monophosphate nucleotide coordination polymers via pH regulation: crystal structure and chirality

Two types of Cu(ii)-AMP-4,4'-bipy coordination polymers, {[Cu(AMP)(4,4'-bipy)(H₂O)₃]·5H₂O}n (1) and {[Cu₂(HAMP)₂(4,4'-bipy)₂(H₂O)₄]·2NO₃·11H₂O}n (2) (Na₂AMP = adenosine 5'-monophosphate disodium salt), were synthesised through pH control. X-ray single-crystal diffraction analysis revealed that 1 and 2 are one-dimensional (1D) coordinating coordination polymers. The nucleotide in 1 was not protonated whereas that in 2 was protonated. With the protonated NO₃^- in 2 entering the crystal lattice, it plays a role in balancing the charge. The chirality was studied using solid-state circular dichroism (CD) spectroscopy based on the analysis of crystal structures.

In vitro selection and application of lanthanide-dependent DNAzymes

Highly sensitive and selective detection of lanthanide ions is a major analytical challenge. In recent years, the use of DNA for this purpose has been pursued. For such highly charged cations, it is difficult to select their aptamers due to strong nonspecific binding. On the other hand, the use of catalytic DNA or DNAzymes has an advantage to overcome this problem, especially DNAzymes with RNA-cleaving activity. In this chapter, a few such DNAzymes are introduced and methods for in vitro selection of lanthanide-dependent RNA-cleaving DNAzymes are described in detail, including the selection protocols, the DNA sequences used, the characterization of selected DNAzymes and their conversion into biosensors. All of the experiments use only fluorophore-labeled DNA, and radioisotope labeling is completely avoided. The resulting DNAzymes can distinguish lanthanides from non-lanthanide metals, tell the difference between light and heavy lanthanides, and can be used together to discriminate individual lanthanides.

Zr-based acid-stable nucleotide coordination polymers: An excellent platform for acidophilic enzymes immobilization

Acidophilic enzymes play an important role in special industrial catalytic reactions. In this work, we reported Zr-based acid-stable nucleotide coordination polymers (CPs) for efficiently improving acidophilic enzymes immobilization. Among all tested metal ions, the Zr⁴⁺/AMP CPs exhibited the highest acid stability and enzyme affinity. As a typical acidophilic enzyme, the immobilized Chloroperoxidase by Zr⁴⁺/AMP CPs displayed robust reusability in the asymmetric synthesis of modafinil, remained 95.7% of conversion rate and 99.1% enantiomeric excess (e.e.) value. This work displayed a novel acid-stable bioorganic and inorganic hybrid nanomaterial for acidophilic enzymes immobilization.

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.

Time-Resolved Fluorescence Detection of Superoxide Anions Based on an Enzyme-Integrated Lanthanide Coordination Polymer Composite

In this work, we proposed a new strategy of fabricating time-resolved fluorescent nanoprobes by using an enzyme-integrated lanthanide coordination polymer (CP) composite for the detection of superoxide anions (O₂^•-). This CP composite was constructed with terbium ions (Tb³⁺) as a metal node, adenosine triphosphate (ATP) as a bridge ligand, and carboxyphenylboronic acid (CPBA) as a sensitizer in which superoxide dismutase (SOD) was encapsulated by a self-adaptive inclusion process. The as-prepared SOD@ATP/Tb-CPBA displays both catalytic and fluorescence properties. Benefiting from the shielding effect of ATP/Tb CP, greatly enhanced catalytic activity and stability against harsh environments can be obtained in the loaded SOD. Meanwhile, the loaded SOD can remove the water molecules on the coordination sphere of Tb³⁺, leading to a significant increase in the fluorescence intensity and lifetime of SOD@ATP/Tb-CPBA. However, upon the addition of O₂^•-, the fluorescence of SOD@ATP/Tb-CPBA was quenched significantly. This is because SOD can convert O₂^•- into H₂O₂ to induce the deboronation of CPBA, resulting in an intramolecular charge transfer process. On this basis, by taking advantage of Tb³⁺ in long lifetime emission, a time-resolved fluorescence method was developed for the detection of O₂^•-, and satisfactory results have been achieved in both buffered aqueous solutions and serum samples. We believe that the presented study will open up a new avenue to develop enzyme-involved fluorescent nanoprobes.

Nanoscale Copper(II)-Diethyldithiocarbamate Coordination Polymer as a Drug Self-Delivery System for Highly Robust and Specific Cancer Therapy

Disulfiram (DSF), an old alcohol-aversion drug, has been repurposed for cancer therapy, and mechanistic studies reveal that it needs to be metabolized to diethyldithiocarbamate (DTC) and subsequently coordinates with copper(II) to form the DTC-copper complex (CuET) for anticancer activation. Here, we utilized this mechanism to construct a CuET self-delivery nanosystem based on the metal coordination polymer for highly robust and selective cancer therapy. In our design, the nanoparticles were facilely prepared under mild conditions by virtue of the strong coordination between Cu²⁺ and DTC, yielding 100% CuET loading capacity and allowing for further hyaluronic acid (HA) modification (CuET@HA NPs). The CuET@HA NPs could selectively deliver into cancer cells and release the active component of CuET in response to both endo/lysosome acidic pH and intracellular abundant GSH, which induces strong cytotoxicity toward cancer cells over normal cells taking advantage of the p97 pathway interference mechanism. Upon intravenous injection, the self-assembled system could passively accumulate into a tumor and elicit potent tumor growth inhibition at a dose of 1 mg/kg without any noticeable side effects. Given the cost-effective and easily scaled-up preparation, our designed nanosystem provides a promising strategy to pave the way for clinical translation of DSF-based cancer chemotherapy.

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.

A high local DNA concentration for nucleating a DNA/Fe coordination shell on gold nanoparticles

Preparing DNA/Fe coordination nanoparticles in solution requires a high concentration of DNA. Herein we grew a DNA/Fe shell on DNA-functionalized gold nanoparticles. Taking advantage of the high local DNA density, the required DNA concentration decreased 60-fold, and the size can be controlled. This hybrid material allowed drug loading and colorimetric sensing.

Multiresponsive Supramolecular Luminescent Hydrogels Based on a Nucleoside/Lanthanide Complex

Supramolecular luminescent hydrogels based on natural molecules have shown high potential for a variety of applications because of unique optical properties and biocompatibility, particularly serving as advanced biomaterials for bioimaging, biosensing, cell engineering, and so forth. A lanthanide complex-based system provides a promising way to prepare supramolecular luminescent hydrogels. Herein, we realize the creation of a luminescent hydrogel assembled from lanthanides and nucleosides. Nucleosides, the essential components of nucleic acids, functioning as the ligands, successfully chelate with lanthanides and form complexes in water. The complexes subsequently serve as building-blocks to form supramolecular hydrogels, which exhibit characteristic luminescent emission of lanthanides. The coordination modes and forming mechanism are studied by electrospray ionization time-of-flight mass spectrometry, matrix-assisted laser desorption/ionization time of flight mass spectrometry, ¹H NMR spectroscopy, and Fourier transform infrared spectroscopy; the corresponding molecular simulations are presented, and macro-/micro-morphologies, mechanical properties, and luminescent performances of hydrogels are systemically studied. Remarkably, these luminescent hydrogels show fluorochromic properties in response to external stimuli, including pH, temperature, anions, and cations, which are thus adopted to design smart luminescent switches and detect specific species such as Cu²⁺. Our work provides a feasible strategy to prepare stimuli-responsive luminescent hydrogels, reveals the diverse potential of nucleoside-based hydrogels, and exhibits a novel pathway for the preparation of smart optical materials.

One-step synthesis of Cu(II) metal-organic gel as recyclable material for rapid, efficient and size selective cationic dyes adsorption

Efficient removal of non-biodegradable and hazardous dyes from wastewater remains a hot research topic. Herein, a rationally designed a Cu(II)-based metal-organic gel (Cu-MOG) with a nanoporous 3D network structure prepared via a simple one-step mixing method was successfully employed for the removal of cationic dyes. The Cu-MOG exhibited high efficiency, with an adsorption capacity of up to 650.32 mg/g, and rapid adsorption efficiency, with the ability to adsorb 80% of Neutral Red within 1 min. The high adsorption efficiency was attributed to its large specific surface area, which enabled it to massively bind cationic dyes through electrostatic interaction, and a nanoporous structure that promoted intra-pore diffusion. Remarkably, the Cu-MOG displayed size-selective adsorption, based on adsorption studies concerning dyes of different sizes as calculated by density functional theory. Additionally, the adsorption performance of the Cu-MOG still maintained removal efficiency of 100% after three regeneration cycles. These results suggested that the Cu-MOG could be expected to be a promising and competitive candidate to conveniently process wastewater.

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.

Continuously Tunable Nucleotide/Lanthanide Coordination Nanoparticles for DNA Adsorption and Sensing

Metal-organic coordination polymers (CPs) have attracted great research interest because they are easy to prepare, porous, flexible in composition, and designable in structure. Their applications in biosensor development, drug delivery, and catalysis have been explored. Lanthanides and nucleotides can form interesting CPs, although most previous works have focused on a single type of metal ligand. In this work, we explored mixed nucleotides and studied their DNA adsorption properties using fluorescently labeled oligonucleotides. Adenosine monophosphate (AMP) and guanosine monophosphate (GMP) formed negatively charged CP nanoparticles with most lanthanides, and thus a salt was required to adsorb negatively charged DNA. DNA adsorption was faster and reached a higher capacity with lighter lanthanides. Desorption of pre-adsorbed DNA by inorganic phosphates, urea, proteins, surfactants, and competing DNA was successively carried out. The results suggested the importance of the DNA phosphate backbone, although hydrogen bonding and DNA bases also contributed to adsorption. The AMP CPs adsorbed DNA more strongly than the GMP ones, and using mixtures of AMP and GMP, continuous tuning of DNA adsorption affinity was achieved. Such CPs were also used as a sensor for DNA detection based on the different affinities of single- and double-stranded DNA, and a detection limit of 0.9 nM target DNA was achieved. Instead of tuning DNA adsorption by varying the length and sequence of DNA, the composition of CPs can also be controlled to achieve this goal.