Confining molecules within aqueous coordination nanoparticles by adaptive molecular self-assembly

A Nanoscale Trans-Platinum(II)-Based Supramolecular Coordination Self-Assembly with a Distinct Anticancer Mechanism

Drug resistance significantly hampers the clinical application of existing platinum-based anticancer drugs. New platinum medications that possess distinct mechanisms of action are highly desired for the treatment of Pt-resistant cancers. Herein, a nanoscale trans-platinum(II)-based supramolecular coordination self-assembly (Pt-TCPP-BA) is prepared via using trans-[PtCl2(pyridine)(NH3)] (transpyroplatin), tetracarboxylporphyrin (TCPP), and benzoic acid (BA) as building blocks to combat drug resistance in platinum-based chemotherapy. Mechanistic studies indicate that Pt-TCPP-BA shows a hydrogen-peroxide-responsive dissociation behavior along with the generation of bioactive trans-Pt(II) and TCPP-Pt species. Different from cisplatin, these degradation products interact with DNA via interstrand cross-links and small groove binding, and induce significant upregulation of cell-death-related proteins such as p53, cleaved caspase 3, p21, and phosphorylated H2A histone family member X in cisplatin-resistant cancer cells. As a result, Pt-TCPP-BA exhibits potent killing effects against Pt-resistant tumors both in vitro and in vivo. Overall, this work not only provides a new platinum drug for combating drug-resistant cancer but also offers a new paradigm for the development of platinum-based supramolecular anticancer drugs.

A ternary nucleotide-lanthanide coordination nanoprobe for ratiometric fluorescence detection of ciprofloxacin

Ciprofloxacin (CIP) is a widely used broad-spectrum antibiotic and has been associated with various side effects, making its accurate detection crucial for patient safety, drug quality compliance, and environmental and food safety. This study presents the development of a ternary nucleotide-lanthanide coordination nanoprobe, GMP-Tb-BDC (GMP: guanosine 5'-monophosphate, BDC: 2-amino-1,4-benzenedicarboxylic acid), for the sensitive and ratiometric detection of CIP. The GMP-Tb-BDC nanoprobe was constructed by incorporating the blue-emissive ligand BDC into the Tb/GMP coordination polymers. Upon the addition of CIP, the fluorescence of terbium ion (Tb3+ ) was significantly enhanced due to the coordination and fluorescence sensitization properties of CIP, while the emission of the BDC ligand remained unchanged. The nanoprobe demonstrated good linearity in the concentration range of 0-10 μM CIP. By leveraging mobile phone software to analyze the color signals, rapid on-site analysis of CIP was achieved. Furthermore, the nanoprobe exhibited accurate analysis of CIP in actual drug and milk samples. This study showcases the potential of the GMP-Tb-BDC nanoprobe for practical applications in CIP detection.

Direct synthesis of amorphous coordination polymers and metal–organic frameworks

Coordination polymers (CPs) and their subset, metal-organic frameworks (MOFs), can have porous structures and hybrid physicochemical properties that are useful for diverse applications. Although crystalline CPs and MOFs have received the most attention to date, their amorphous states are of growing interest as they can be directly synthesized under mild conditions. Directly synthesized amorphous CPs (aCPs) can be constructed from a wider range of metals and ligands than their crystalline and crystal-derived counterparts and demonstrate numerous unique material properties, such as higher mechanical robustness, increased stability and greater processability. This Review examines methods for the direct synthesis of aCPs and amorphous MOFs, as well as their properties and characterization routes, and offers a perspective on the opportunities for the widespread adoption of directly synthesized aCPs.

Universal "Three-in-One" Matrix to Maximize Reactive Oxygen Species Generation from Food and Drug Administration-Approved Photosensitizers for Photodynamic Inactivation of Biofilms

Biofilms, an accumulation of microorganisms, cause persistent bacterial infection and low cure rate due to the remarkable drug resistance. Photodynamic inactivation (PDI) is a promising treatment modality for bacterial infections, but the formation of biofilms raises new challenges for photosensitizers (PSs), particularly the reactive oxygen species (ROS) generation efficiency. Herein, through targeting the Jablonski energy diagram, we proposed a universal "three-in-one" matrix of Gd³⁺-ADP assembly for encapsulation and fixing of PSs to inhibit non-radiative transitions and promoting intersystem crossing (ISC) by the heavy atom and paramagnetic effects of Gd³⁺, eventually resulted in boosted ROS generation from the existing PSs (1.5-9.0-fold). Particularly, photophysical studies indicated that the matrix resulted in simultaneous ISC promotion and triplet-state lifetime lengthening, which is essential for ROS boosting. The PDI performance of the matrix was confirmed through fast and effective elimination of bacterial biofilms in 10-30 min. Moreover, successful therapy of a Pseudomonas aeruginosa biofilm-infected all-thickness third-degree burn wound was achieved within 11 days with Ce 6@CNs (matrix) but not feasible for matrix-free PSs (Ce 6 only), which highlighted the role of "three-in-one" matrix in ROS boosting.

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.

An Aqueous Room-Temperature Phosphorescent Probe for Gd3+

An aqueous room-temperature phosphorescent (RTP) probe for Gd3+ is reported, based on Gd3+-induced intersystem promoting and the oxygen-shielding property of the Gd3+/AMP/fluorescein coordination polymer nanoparticles (CPNs). Besides selective Gd3+ detection,...

Highlights of the development and application of luminescent lanthanide based coordination polymers, MOFs and functional nanomaterials

The development of lanthanide based coordination polymer and metal-organic framework (CPs and MOFs) nanomaterials as novel functional (e.g. luminescent and magnetic) materials has attracted significant attention in recent times. This is in part due to the wide, but yet unique coordination requirements that the f-metal ions possess, as well as their attractive physical properties, which are often transferred to the bulk material. Hence, there is no surprise, that the design, synthesis and characterisation of lanthanide based CP/MOF materials (featuring either 'pure' lanthanides, or a mixture of both f- and d-metal ions) for applications in gas and small molecule absorption, storage, conversion/catalysis, chemical sensing, bio-imaging, drug delivery, etc. has been a prominent feature in the scientific literature. In this review, we give a selected overview of some of the recent developments in the area of Ln CP/MOF based nanomaterials for sensing, optical materials and bio-medicine research, as well as making reference to some more established examples, with the view of introducing, particularly to new researchers to the field, the powerful and attractive features of lanthanide based materials.

Dual lanthanide-probe based on coordination polymer networks for ratiometric detection of glyphosate in food samples

Herein, a new type of coordination polymer networks (CPNs), where both of 2,6-Pyridinedicarboxylic acid (DPA) and guanylate monophosphate (GMP) chelate with Eu3+, are firstly synthesized (GMP/Eu/DPA). After mixing with GMP/Tb CPNs, a novel ratiometric dual lanthanide nanoprobe is constructed. Alkaline phosphohydrolase (ALP) specifically induces the cleavage of phosphate ester group in GMP. Therefore, the addition of ALP causes the fluorescence quenching of GMP/Tb, and then the emissions of GMP/Eu/DPA enhance as the result of the formation of Eu/DPA complexes. Glyphosate, as an organophosphorus pesticide, can vehemently inhibit the catalytic activity of ALP, so a ratiometric detection of glyphosate can be achieved with a linear range from 0.015 to 8.45 μg/mL. The present strategy also shows good recoveries for measuring glyphosate in rice, millet, soybean, milk, tap water, and mountain spring water, suggesting a great potential for applications in foods.

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.

Functional Systems Derived from Nucleobase Self-assembly

Dynamic and reversible non-covalent interactions endow synthetic systems and materials with smart adaptive functions that allow them to response to diverse stimuli, interact with external agents, or repair structural defects. Inspired by the outstanding performance and selectivity of DNA in living systems, scientists are increasingly employing Watson-Crick nucleobase pairing to control the structure and properties of self-assembled materials. Two sets of complementary purine-pyrimidine pairs (guanine:cytosine and adenine:thymine(uracil)) are available that provide selective and directional H-bonding interactions, present multiple metal-coordination sites, and exhibit rich redox chemistry. In this review, we highlight several recent examples that profit from these features and employ nucleobase interactions in functional systems and materials, covering the fields of energy/electron transfer, charge transport, adaptive nanoparticles, porous materials, macromolecule self-assembly, or polymeric materials with adhesive or self-healing ability.

A label-free luminescent assay for tyrosinase activity monitoring and inhibitor screening with responsive lanthanide coordination polymer nanoparticles

In this work, a label-free, selective, and sensitive luminescent sensing platform was established for tyrosinase (TYR) activity monitoring and its inhibitor screening using one kind of lanthanide coordination polymer nanoparticles AMP-Tb/Ag⁺. By taking advantage of the specific binding and redox properties of Ag⁺ incorporated into the AMP-Tb network and dopamine (DA) as the product of the model substrate tyramine, the enzymatic reaction and the signal change of the sensing platform was effectively linked. The cooperative effect of a weakened energy transfer from AMP to Tb³⁺ by altering the electronic structure of Ag⁺ and an efficient photoinduced election transfer (PET) process caused by dopaquinone facilitated the luminescence quenching of Tb³⁺. Thus, this luminescent sensing platform could be employed for quantitative evaluation of TYR activity. There was a good linear range for TYR activity from 0.08 to 0.20 U mL^-1 with a low detection limit of 0.004 U mL^-1. Furthermore, this assay was successfully applied to accurate determination of TYR activity in human serum samples and efficient screening of TYR inhibitors. Considering unique spectral characteristics of lanthanides along with operation simplicity and superior analytical performance, this sensing platform is very promising in clinical diagnosis and drugs screening for TYR-associated diseases.

A signal amplification strategy for prostate specific antigen detection via releasing oxidase-mimics from coordination nanoparticles by alkaline phosphatase

A novel signal amplification method for prostate specific antigen (PSA) is developed by freeing fluorescein with photoinduced oxidase-like activity from coordination nanoparticles (CNPs) in the presence of alkaline phosphatase (ALP). CNPs loaded with fluorescein (F@CNPs) are obtained in aqueous solution by self-assembly using Tb³⁺ as metal ion, guanosine monophosphate (5'-GMP) as ligand, and fluorescein as signal molecule. The F@CNPs display outstanding properties of simple synthesis, low cost, good water solubility, negligible leakage and satisfactory load capacity. Fluorescein is quantitatively encapsulated in CNPs with a binding ratio of 92.72%. Meanwhile, ALP can specifically hydrolyze the phosphate group of 5'-GMP ligand, triggering the destruction of F@CNPs and leakage of fluorescein. Fluorescein, a photoinduced oxidase mimic, can catalyze the oxidation of non-fluorescent Amplex UltraRed (AUR) into fluorescent resorufin under LED lamp. This strategy exhibits good sensitivity for ALP detection. In addition, a new immunoassay for PSA is validated by labelling ALP on PSA antibody. The low detection limit of 0.04 ng mL^-1 in detecting PSA is appropriate for PSA detection in real samples. Therefore, the work not only establishes a new strategy for ALP and PSA determination, but also provides a new conception for putting photoinduced oxidase-like fluorescein in practical application.

Boronate sol-gel method for one-step fabrication of polyvinyl alcohol hydrogel coatings by simple cast- and dip-coating techniques

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities. A mixture of PVA and DBA in aqueous ethanol is prepared as a coating agent. The long pot life of the mixture allows for the coating of a wide range of materials with hydrogel films by simple cast- and dip-coating techniques. The resultant films show negligible dissolution in water and the intrinsic hydrophilicity of PVA provides the films with functional properties, such as improved antifogging property and resistance to protein and cell fouling. The self-assembling process shows adaptive inclusion properties toward nanoscale materials, such as metal–organic coordination polymers and inorganic nanoparticles, affording composite films. Furthermore, the coating film exhibits a unique secondary functionalization reactivity toward boronic acid-appended fluorescent dyes, through which a variety of materials are converted into fluorescent materials.

The self-assembly of polyvinyl alcohol (PVA) and benzene-1,4-diboronic acid (DBA) is employed as a sol–gel method for one-step fabrication of hydrogel coatings with versatile functionalities.

Energy-Transfer Metal-Organic Nanoprobe for Ratiometric Sensing with Dual Response to Peroxynitrite and Hypochlorite

An energy-transfer metal-organic nanoprobe is designed for ratiometric sensing with dual response to both peroxynitrite (ONOO-) and hypochlorite (ClO-). Here, a nanoscale metal-organic framework (NMOF) acts as the energy donor and molecular probe as the acceptor to construct a Förster resonance energy transfer (FRET) nanosystem. Biocompatible dextran conveniently binds to the NMOF surface through multiple weak coordination interactions to improve water dispersibility and cell uptake. Dextran can also coordinate with the molecular probe with arylboronic acid group, which enables the convenient grafting of molecular probes to the NMOF surface to construct energy-transfer nanoprobes. Because of efficient FRET, the bright blue fluorescence of NMOF is quenched, whereas red emission from the acceptor is enhanced. Upon reacting with ONOO-, the probe departs from NMOF and the fluorescence of NMOF is recovered because of the interruption of FRET. When reacting with ClO-, the phenothiazine moiety in the molecular probe is oxidized into phenothiazine-5-oxide, which leads to more efficient energy transfer and the fluorescence shifts from red to orange. The nanoprobes are also successfully applied to the detection of ONOO- and ClO- in living cells.

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.

Simple and Versatile Platform for Air-Tolerant Photon Upconverting Hydrogels by Biopolymer-Surfactant-Chromophore Co-assembly

Exploration of triplet-triplet annihilation based photon upconversion (TTA-UC) in aqueous environments faces difficulty such as chromophores insolubility and deactivation of excited triplets by dissolved oxygen molecules. We propose a new strategy of biopolymer-surfactant-chromophore coassembly to overcome these issues. Air-stable TTA-UC with a high upconversion efficiency of 13.5% was achieved in hydrogel coassembled from gelatin, Triton X-100 and upconverting chromophores (triplet sensitizer and emitter). This is comparable to the highest UC efficiency observed to date for air-saturated aqueous UC systems. Moreover, this is the first example of air-stable TTA-UC in the form of hydrogels, widening the applicability of TTA-UC in biological applications. The keys are two-fold. First, gelatin and the surfactant self-assemble in water to give a developed hierarchical structure with hydrophobic domains which accommodate chromophores up to high concentrations. Second, thick hydrogen-bonding networks of gelatin backbone prevent O₂ inflow to the hydrophobic interior, as evidenced by long acceptor triplet lifetime of 4.9 ms. Air-stable TTA-UC was also achieved for gelatin with other nonionic surfactants (Tween 80 and Pluronic f127) and Triton X-100 with other gelling biopolymers (sodium alginate and agarose), demonstrating the versatility of current strategy.

Integrated Antibody with Catalytic Metal-Organic Framework for Colorimetric Immunoassay

Enzyme-linked immunosorbent assay has been widely used as a gold standard in biomedical field, but some inevitable drawbacks still exist in its practical applications, especially the laborious preparation of enzyme-antibody conjugates by a covalent linkage. In this work, we proposed a new strategy to prepare enzyme-antibody conjugate by integrating antibody with catalytic metal-organic framework (MOF) to form dual-functional MOF/antibody composite. As models, rabbit antimouse immunoglobulin G antibody (RIgG) and Cu-MOF with peroxidase-like activity were used to fabricate RIgG@Cu-MOF composite for colorimetric immunoassay. It was found that Cu-MOF as a host not only has no influence on the original capture ability of RIgG to its corresponding antigen (mIgG), but also can shield RIgG against long-term storage, high temperature, and biological degradation. More importantly, upon the formation of sandwiched immunocomplex between RIgG@Cu-MOF and capture antibody, Cu-MOF can serve as a signal amplification unit to perform colorimetric immunoassay. The detection limit of RIgG@Cu-MOF toward mIgG was obtained at 0.34 ng/mL, which is 3-fold lower than that of horseradish peroxidase labeled RIgG. Furthermore, the successful determination of mIgG in serum sample demonstrates the applicability of RIgG@Cu-MOF in detecting real sample. Therefore, it is highly anticipated that this study can offer a new way to prepare enzyme-antibody conjugates, facilitating the exploration of MOF composites in biomedical field.

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

Metal coordination with organic ligands often produce crystalline metal-organic frameworks and sometimes amorphous nanoparticles. In this work, we explore a different type of material from the same chemistry: hydrogels. Lanthanides are chosen as the metal component because of their important technological applications and continuously tunable properties. Adenosine monophosphate (AMP) and lanthanides form two types of coordination materials: the lighter lanthanides from La³⁺ to Tb³⁺ form nanoparticles, whereas the rest heavier ones initially form nanoparticles but later spontaneously transform to hydrogels. This slow sol-to-gel transition is accompanied by heat release, as indicated by isothermal titration calorimetry. The transition is also accompanied by a morphology change from nanoparticles to nanofibers, as indicated by transmission electron microscopy. These gels are insensitive to ionic strength or temperature with excellent stability. Gelation is unique to AMP because other nucleotides or other adenine derivatives only yield nanoparticles or soluble products. Entrapment of guest molecules such as glucose oxidase is also explored, where the hydrogels allow a better enzyme activity and stability compared to nanoparticles. Further applications of lanthanide coordinated hydrogels might include biosensors, imaging agents, and drug delivery.

Nucleobases, nucleosides, and nucleotides: versatile biomolecules for generating functional nanomaterials

The incorporation of biomolecules into nanomaterials generates functional nanosystems with novel and advanced properties, presenting great potential for applications in various fields. Nucleobases, nucleosides and nucleotides, as building blocks of nucleic acids and biological coenzymes, constitute necessary components of the foundation of life. In recent years, as versatile biomolecules for the construction or regulation of functional nanomaterials, they have stimulated interest in researchers, due to their unique properties such as structural diversity, multiplex binding sites, self-assembly ability, stability, biocompatibility, and chirality. In this review, strategies for the synthesis of nanomaterials and the regulation of their morphologies and functions using nucleobases, nucleosides, and nucleotides as building blocks, templates or modulators are summarized alongside selected applications. The diverse applications range from sensing, bioimaging, and drug delivery to mimicking light-harvesting antenna, the construction of logic gates, and beyond. Furthermore, some perspectives and challenges in this emerging field are proposed. This review is directed toward the broader scientific community interested in biomolecule-based functional nanomaterials.

Coordination polymer nanoparticles from nucleotide and lanthanide ions as a versatile platform for color-tunable luminescence and integrating Boolean logic operations

Novel supramolecular coordination polymer nanoparticles (CPNs) were synthesized via the self-assembly of guanosine monophosphate (GMP) and lanthanide ions (Ln³⁺, including Tb³⁺, Eu³⁺ and Ce³⁺) in aqueous solution. These CPNs (GMP/Tb³⁺, GMP/Eu³⁺ and GMP/Ce³⁺) have an identical coordination environment but exhibit completely different luminescence properties responding to external stimuli such as dipicolinic acid (DPA), ethylene diamine tetraacetic acid (EDTA), pH and metal ions, which has inspired us to tune the emission color of the CPNs and perform multiple logic operations. Firstly, color-tunable luminescence from red to green can be easily achieved by modulating the doping ratio of Tb³⁺ and Eu³⁺ into GMP. Notably, trichromatic white light emitting CPNs can be successfully realized by simultaneously doping Tb³⁺, Eu³⁺ and Ce³⁺ into the host or just adjusting the pH of the solution. What's more, by employing GMP/Tb³⁺ CPNs as a logic operator, we have achieved the implementation of multilayered gate cascades (INH-INH, NOR-OR). When GMP/Eu³⁺ CPNs served as a logic operator, the logic elements can be integrated as another combinatorial gate (AND-INH). Moreover, by employing the red emission of Eu³⁺ and blue emission of GMP as the dual-output signal transducer, a set of parallel logic gates was established successfully. These results help elucidate the design rules by which simple logic can be integrated to construct cascaded logic gates and expand the applications of CPNs in light-emitting diode (LED) lamps and biological systems.

Self-assembly of Gd3+/SDS/HEPES complex and curcumin entrapment for enhanced stability, fluorescence image in cellular system

At present, strategies to disperse hydrophobic molecules in water without altering their chemical structures include conventional surfactant-based micellar and vesicular systems, encapsulation into water dispersible polymeric nanoparticles, and loading onto the surface of various metal nanoparticles. Here, we report a simple and low cost platform to incorporate hydrophobic molecules into a stable water dispersible nanostructure that can significantly increase the stability of the encapsulated materials. The platform is based on the incorporation of hydrophobic molecules into the self-assembled complex of gadolinium ion (Gd³⁺), sodium dodecyl sulfate (SDS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) called GdSH. After being incorporated, the two model hydrophobic dyes, curcumin and curcumin borondifluoride show approximately 50% and 30% improved stability, respectively. Investigation of the self-assembled 10-14 multilayered 60nm spheres with inter-layer distances of 4.25nm indicates coordination of SDS and HEPES with Gd³⁺. Incorporation of the hydrophobic molecules into the multilayered spheres results in reduction of the interlayer distance of the multilayer spheres to 4.17nm, suggesting enhanced packing of the hydrophobic chain of SDS and HEPES around the Gd³⁺. The incorporation of the two curcuminoids into the self-assembled complex also causes an increase in fluorescence quantum yield of the two dyes, thus suggesting spatial confinement of the packed dye molecules. The better cellular uptake of the nanoparticles is responsible for the expected enhancement in fluorescence image of the encapsulated materials.

Cytosine-Cytosine Base-Pair Mismatch and Chirality in Nucleotide Supramolecular Coordination Complexes

The base-pair sequences are the foundation for the biological processes of DNA or RNA, and base-pair mismatch is very important to reveal genetic diseases and DNA rearrangements. However, the lack of well-defined structural information about base-pair mismatch is obstructing the investigation of this issue. The challenge is to crystallize the materials containing the base-pair mismatch. Engineering the small-molecule mimics or model is an effective strategy to solve this issue. Here, six cytidine-5'-monophosphate (CMP) and 2'-deoxycytidine-5'-monophosphate (dCMP) coordination polymers were reported containing cytosine-cytosine base-pair mismatch (i-motif), and their single-crystal structures and chiralities were studied. The precise control over the formation of the i-motif was demonstrated, in which the regulating of supramolecular interactions was achieved based on molecular design. In addition, the chiralities of these coordination polymers were investigated according to their crystal structures and solution- and solid-state circular dichroism spectroscopy.

Photon Upconversion and Molecular Solar Energy Storage by Maximizing the Potential of Molecular Self-Assembly

The self-assembly of functional molecules into ordered molecular assemblies and the fulfillment of potentials unique to their nanotomesoscopic structures have been one of the central challenges in chemistry. This Feature Article provides an overview of recent progress in the field of molecular self-assembly with the focus on the triplet-triplet annihilation-based photon upconversion (TTA-UC) and supramolecular storage of photon energy. On the basis of the integration of molecular self-assembly and photon energy harvesting, triplet energy migration-based TTA-UC has been achieved in varied molecular systems. Interestingly, some molecular self-assemblies dispersed in solution or organogels revealed oxygen barrier properties, which allowed TTA-UC even under aerated conditions. The elements of molecular self-assembly were also introduced to the field of molecular solar thermal fuel, where reversible photoliquefaction of ionic crystals to ionic liquids was found to double the molecular storage capacity with the simultaneous pursuit of switching ionic conductivity. A future prospect in terms of innovating molecular self-assembly toward molecular systems chemistry is also discussed.

Hierarchical Self-Assembly of Luminescent Tartrate-Bridged Chiral Binuclear Tb(III) Complexes in Ethanol

A new family of supramolecular metalloamphiphiles carrying two metal centers is developed. They are formed by bridging two coordinatively unsaturated lipophilic Tb³⁺ complexes (TbL⁺) with chiral dicarboxylate anions. The formation of bridging coordination bonds is confirmed using UV spectroscopy, induced circular dichroism (ICD), increased luminescence intensity of TbL⁺, and electrospray ionization mass spectrometry (ESIMS) analysis. These supramolecular metalloamphiphiles hierarchically self-assemble in ethanol to give luminescent nanospheres, as observed using transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The two hydroxyl groups introduced in the bridging ligands of [TbL]₂(d-/l-tartrate) significantly promote self-assembly by increasing coherent forces via intermolecular hydrogen bonding. The observed self-assembly in ethanol also merits mention because such polar alcoholic media have been unfavorable for conventional molecular self-assemblies. The present approach offers a new molecular design strategy for composable metalloamphiphiles.

Lanthanide Coordination Polymer Nanoparticles as an Excellent Artificial Peroxidase for Hydrogen Peroxide Detection

Lanthanide coordination polymer nanoparticles (Ln-CPNs) have been recently demonstrated as excellent platforms for biomolecule detection. In this work, we synthesized novel cerium coordination polymer nanoparticles ATP-Ce-Tris CPNs in a simple and quick way using ATP molecules as the biocompatible ligands to Ce(3+) ions in tris(hydroxymethyl)aminomethane hydrochloric (Tris-HCl) solution. In view of the excellent free radical scavenging property of cerium compounds, which is ascribed to the mixed valence state (Ce(3+), Ce(4+)) and the reversible switch from Ce(3+) to Ce(4+), the synthesized ATP-Ce-Tris CPNs was used as artificial peroxidase to selectively and sensitively detect H2O2. The sensing mechanism depends on the oxidation of the fluorescent ATP-Ce(III)-Tris CPNs to nonfluorescent ATP-Ce(IV)-Tris CPNs by H2O2. Compared with those inorganic cerium oxide sensors, this kind of fluoresence ATP-Ce-Tris CPNs sensor needs no additional organic redox dye, such as ABTS (2,20-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid), TMB (3,3,5,5-tetramethylbenzidine), or fluorescein as signal molecules. Moreover, such ATP-Ce-Tris CPNs sensor exhibited a more sensitive response to H2O2 with a detection limit down to 0.6 nM, which is 2 orders of magnitude lower than those of cerium oxide sensors. This sensing platform was further extended to the detection of glucose in combination with the specific catalytic effect of glucose oxidase (GOx) for the oxidation of glucose and formation of H2O2.

Triplet energy migration-based photon upconversion by amphiphilic molecular assemblies in aerated water

A molecular self-assembly approach is developed to resolve an outstanding issue in triplet energy migration-based photon upconversion (TEM-UC), that is, air-stable TEM-UC in water. Amphiphilic cationic acceptor (emitter) molecules self-assemble in water via hydrophobic and hydrogen bonding interactions, with which anionic donor (sensitizer) molecules are integrated through electrostatic interactions. Triplet energy is quantitatively transferred from the excited donor to the acceptor, which is followed by effective triplet energy migration among the pre-organized acceptors. It leads to TTA and concomitant UC emission in water. The dense acceptor chromophore arrays with extended hydrogen bonding networks show efficient barrier properties against molecular oxygen, as demonstrated by the stable UC emission even in air-saturated water.

A visual and reversible assay for temperature using thioflavin T-doped lanthanide/nucleotide coordination polymers

In this work, we prepared a type of thioflavin T (ThT)-doped lanthanide/nucleotide coordination polymer by the self-assembly of ThT, europium ions (Eu(3+)) and nucleotides (guanosine monophosphate, GMP) in aqueous solution (i.e. ThT/Eu/GMP). The Eu/GMP coordination polymers show excellent adaptive inclusion properties for ThT in a convenient one-step approach, which can readily enhance the fluorescence of ThT via the restricted effect. Moreover, the as-prepared hydrophilic ThT/Eu/GMP coordination polymers have the capability to act as a temperature-sensitive, visual and reversible sensor in aqueous solution under the irradiation of visible light. Our proposed design is cost-effective and simple to prepare without chemical modification or fluorescence labeling.

Stimulus Response of Au-NPs@GMP-Tb Core-Shell Nanoparticles: Toward Colorimetric and Fluorescent Dual-Mode Sensing of Alkaline Phosphatase Activity in Algal Blooms of a Freshwater Lake

In this study, we demonstrate a colorimetric and fluorescent dual-mode method for alkaline phosphatase activity (APA) sensing in freshwater lake with stimuli-responsive gold nanoparticles@terbium-guanosine monophosphate (Au-NPs@GMP-Tb) core-shell nanoparticles. Initially, the core-shell nanoparticles were fabricated based on Au-NPs decorated with a fluorescent GMP-Tb shell. Upon being excited at 290 nm, the as-formed Au-NPs@GMP-Tb core-shell nanoparticles emit green fluorescence, and the decorated GMP-Tb shell causes the aggregation of Au-NPs. However, the addition of ALP destroys GMP-Tb shell, resulting in the release of Au-NPs from the shell into the solvent. As a consequence, the aggregated Au-NPs solubilizes with the changes in the UV-vis spectrum of the dispersion, and in the meantime, the fluorescence of GMP-Tb shell turns off, which constitutes a new mechanism for colorimetric and fluorescent dual-mode sensing of APA. With the method developed here, we could monitor the dynamic change of APA during an algal bloom of a freshwater lake, both by the naked eye and further confirmed by fluorometric determination. This study not only offers a new method for on-site visible detection of APA but also provides a strategy for dual-mode sensing mechanisms by the rational design of the excellent optical properties of Au-NPs and the adaptive inclusion properties of the luminescent infinite coordination polymers.

Recent emergence of photon upconversion based on triplet energy migration in molecular assemblies

This Feature Article reviews an emerging field of triplet energy migration-based photon upconversion (TEM-UC) that allows highly efficient photon upconversion at low excitation power.

Metal-Organic Framework-Based Nanomedicine Platforms for Drug Delivery and Molecular Imaging

Metal-organic frameworks (MOFs), which are a unique class of hybrid porous materials built from metal ions and organic linkers, have attracted significant research interest in recent years. Compared with conventional porous materials, MOFs exhibit a variety of advantages, including a large surface area, a tunable pore size and shape, an adjustable composition and structure, biodegradability, and versatile functionalities, which enable MOFs to perform as promising platforms for drug delivery, molecular imaging, and theranostic applications. In this article, the recent research progress related to nanoscale metal-organic frameworks (NMOFs) is summarized with a focus on synthesis strategies and drug delivery, molecular imaging, and theranostic applications. The future challenges and opportunities of NMOFs are also discussed in the context of translational medical research. More effort is warranted to develop clinically translatable NMOFs for various applications in nanomedicine.

Boronate-Phenolic Network Capsules with Dual Response to Acidic pH and cis-Diols

Dual-responsive boronate-phenolic network (BPN) capsules are fabricated by the complexation of phenylborate and phenolic materials. The BPN capsules are stable in the presence of competing carbohydrates, but dissociate at acidic pH or in the presence of competing cis-diols at physiological pH. This engineered capsule system provides a platform for a wide range of biological and biomedical applications.