Nanomedicine Applications of Hybrid Nanomaterials Built from Metal-Ligand Coordination Bonds: Nanoscale Metal-Organic Frameworks and Nanoscale Coordination Polymers

Core-shell gold nanorod@mesoporous-MOF heterostructures for combinational phototherapy

Despite the increasing usage of porphyrinic metal-organic frameworks (MOFs) for combination therapy, the controlled encapsulation of inorganic nanoparticle-based therapeutics into such MOFs with specific structures has remained a major obstacle for improved tumor therapy. Here, we report the synthesis of a mesoporous MOF shell on the surface of gold nanorods (AuNRs), wherein a single AuNR is captured individually in single-crystalline MOFs with a controlled crystallographic orientation, for combinational phototherapy against solid tumors. The core-shell heterostructures have the benefits of a mesoporous structure and photoinduced singlet oxygen generation behavior characterized by the porphyrinic MOF shell, together with the plasmonic photothermal conversion characteristic of AuNRs. We demonstrated that the AuNR@MOF nanoplatform enables an efficient tumor treatment strategy by combining photodynamic therapy and photothermal therapy. We should emphasize that such systems could have applications beyond the field of cancer therapy, like plasmonic harvesting of light energy to induce and accelerate catalytic reactions within MOFs and multifunctional nanocarriers for agricultural formulations.

Recent advances in phase change material based nanoplatforms for cancer therapy

Cancer has become a severe threat to human life due to its high mortality and metastatic rate. Effective inhibition and killing of cancer cells using chemotherapeutic drugs have been a promising means in clinical cancer therapy. However, the low selectivity, drug-resistance, uncontrollability and serious side effects of chemotherapy significantly limit its further development. There is an urgent need for new treatment strategies to compensate for deficiencies inherent in chemotherapy alone. A growing body of research shows that combined treatment strategies have the potential to overcome this dilemma by achieving significantly enhanced synergistic effects and reduced side effects. Emerging phase change materials (PCMs) create an ideal nanoplatform for cancer combination therapy due to their universal loading properties, stable and temperature-responsive phase transition capability, and excellent natural biocompatibility/biodegradability. The release of therapeutic agents can be precisely controlled through external, non-intrusive stimuli (such as NIR light and ultrasound), avoiding systemic toxicity associated with conventional chemotherapy. Herein, the construction methods and design principles of PCM-based nanoplatforms serving as strict gatekeeper and smart payload delivery systems are discussed in detail. Moreover, the advantages and disadvantages of these nanoplatforms are provided. A suitable discussion and perspective of the remaining challenges and future opportunities for PCM-based nanoplatforms in cancer treatment are also given in conclusion.

Cu2+-Regulated reversible coordination interaction of GQD@Tb/GMP ICP nanoparticles: towards directly monitoring cerebrospinal acetylcholinesterase as a biomarker for cholinic brain dysfunction

This work demonstrates a new strategy for sensing cerebrospinal acetylcholinesterase (AChE) as a cholinergic biomarker for brain dysfunction based on graphene quantum dot (GQD)-functionalized lanthanide infinite coordination polymer (Ln-ICP) nanoparticles. The ICPs used in this work were comprised of two components, i.e. a supramolecular Ln-ICP host formed by the coordination between the GMP ligand and central metal ion Tb3+, and guest GQDs with abundant functional groups, which were utilized as antenna ligands to further sensitize the fluorescence of Tb/GMP. Upon excitation at 300 nm, the obtained GQD@Tb/GMP ICP nanoparticles exhibited enhanced green fluorescence from Tb/GMP. With the addition of Cu2+, the competitive coordination between Cu2+ and GQDs weakened the antenna effect, leading to a decrease in the fluorescence of GQD@Tb/GMP ICPs. However, in the presence of thiocholine (TCh), a thiol-containing compound hydrolyzed from acetylthiocholine (ATCh) by AChE, a stronger coordination interaction between Cu2+ and TCh occurred, resulting in the restoration of the fluorescence of GQD@Tb/GMP ICPs. Using the method established herein, the cerebrospinal AChE fluctuation of rats with acute organophosphorus pesticide (OP) poisoning or chronic Alzheimer's disease (AD) could be monitored. This study essentially provides a novel approach to realize the direct monitoring of a biomarker for brain dysfunction by regulating the competitive coordination interaction reversibly, which is critical in the early diagnosis and therapy of brain diseases.

Green facile synthesis to develop nanoscale coordination polymers as lysosome-targetable luminescent bioprobes

Three new coordination polymers (CPs), namely [{M(HL)(L)(H2O)}(ClO4)(H2O)]∞ (M = Zn for CP 1, Mn for CP 2, Cu for CP 3) were synthesized to explore their efficacy as lysosome-targetable luminescent bioprobes. The synthesized CPs were characterized by techniques including single-crystal X-ray analysis, FTIR spectroscopy and elemental analysis. Single-crystal analysis revealed the formation of iso-structural CPs displaying distorted adamantoid topology developed by bridging ligands and H-bonds connections and metals at the nodes. A green hand-grinding technique with a mortar and pestle resulted in nanoscale coordination polymers (NCPs) suitable for cell permeability and was further confirmed by SEM and DLS analyses. Two of these hand-ground nanoscale coordination polymers NCP 1 and NCP 2 showed excellent green luminescence and were explored as potential and selective long-time biotrackers towards lysosome using the human lung carcinoma cell line (A549). Strikingly, the developed bioprobe displayed excellent bio-availability, photostability and excellent selectivity towards lysosomes sustained by various in vitro cell imaging experiments. Moreover, the long-term probing ability of these NCPs turned out to be better than the commercially available lysosome tracker i.e. LysoTracker Red, indicating their potential real-life application in bio-imaging. To the best ofour knowledge, this is the first example of nonexpensive and less toxic essential transition metal-based nanoscale coordination polymers that can behave as effective lysosome-targetable luminescent bioprobes.

Dynamic effects in crystalline coordination polymers

Dynamic macroscopic behaviour of single crystals of coordination polymers when subjected to light, heat, and mechanical force.

Recent progress in the design and synthesis of zeolite-like metal–organic frameworks (ZMOFs)

ZMOFs are a subset of MOFs that exhibit zeolite-like topologies. Using molecular building block strategy, many ZMOFs with high stability and excellent performance can be rationally designed and synthesized using different secondary building units.

Recent insight into functional crystalline porous frameworks for cancer photodynamic therapy

We summarize and illustrate the recent developments of MOF- and COF-based nanomedicines for PDT and its combined antitumor treatments. Furthermore, major challenges and future development prospects in this field are also discussed.

Bone cements for therapy and regeneration for minimally invasive treatment of neoplastic bone defects

Although calcium phosphate cements (CPCs) have been clinically used to repair bone defects caused by bone tumor resection, traditional CPCs cannot kill the remaining tumor cells after surgery and prevent cancer recurrence. In this study, a multifunctional injectable metal-organic framework (MOF) cobalt coordinated tetrakis(4-carboxyphenyl)porphyrin (Co-TCPP)-modified calcium phosphate cement (Co-TCPP/CPC) was prepared for the minimally invasive treatment of neoplastic bone defects. The incorporation of Co-TCPP not only retained the good injectability of bone cements, but also shortened the setting time, improved the compressive strength, and endowed them with excellent photothermal properties. The hyperthermia effect induced by the presence of Co-TCPP well induced the therapeutic effect against bone tumors both in vitro and in vivo. Moreover, Co-TCPP/CPC exhibited desirable osteogenesis and angiogenesis by promoting bone and vascular regeneration in vivo. Therefore, the Co-TCPP composite bone cement demonstrated its great potential for bone tumor therapy and tissue regeneration, representing a multifunctional biomaterial for the treatment of neoplastic bone defects.

Porphyrin-based metal coordination polymers with self-assembly pathway-dependent properties for photodynamic and photothermal therapy

During the self-assembly process of porphyrin-based metal coordination polymers, two different nanoaggregates were discovered. The nanoaggregates exhibited pathway-dependent properties and showed different applications in phototherapy.

Two cluster-based metal–organic frameworks with selective detection of Hg2+ ion and magnetic properties

Two cluster-based metal–organic frameworks have been synthesized—one exhibits highly selective fluorescent detection of trace Hg2+ and the other shows antiferromagnetic interactions between Mn3+ ions.

Selective dual adsorption performance of hexagonal porous metal–organic framework rods towards CO2 gas and organic dye

The designed porous hexagonal MOF platform confirms a dual selective adsorption of the environmental pollutants CO2 gas and water-soluble organic dye under ambient atmospheric conditions.

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.

Rational design of metal-organic frameworks to deliver methotrexate for targeted rheumatoid arthritis therapy

Methotrexate (MTX) has been used as an anchor drug for the treatment of rheumatoid arthritis (RA), while the patients with chronic MTX administration suffer from severe side-effects. To this end, targeted delivery of MTX by nanomedicine has attracted great interest. In this work, we aimed to employ metal-organic frameworks (MOFs) as nanocarrier to deliver MTX by virtue of its facile and green preparation and exceptionally high drug loading. While MTX could be easily and effectively loaded via different MOF construction strategies, such as direct coordination, physical encapsulation, and covalent conjugation, we found that most of the MTX loading MOFs showed premature and burst drug release, attributable to the unstable coordination between MTX and metals. To address this issue, we rationally designed the MOFs by conjugating MTX with tannic acid (TA) at 2:1 M ratio and then coordinating with ferric ion (Fe³⁺), followed by surface modification of hyaluronic acid (HA). The resulting MOFs achieved ultra-high drug loading (45%) and sustained drug release, and could selectively recognize the diseased cells for anti-inflammatory effect. The in vivo therapeutic evaluation suggested that the MOFs could enhance the anti-rheumatic activity of MTX while minimizing its toxic effects by targeted drug delivery, resulting in improved therapeutic index. This work provides a biocompatible nano-platform to deliver MTX for RA treatment, and importantly, calls for special attention to the gap between MOFs design and their biological applications, and the gap needs to be filled by careful evaluation of in vivo stability and burst drug release.

Bone-seeking nanoplatform co-delivering cisplatin and zoledronate for synergistic therapy of breast cancer bone metastasis and bone resorption

The "vicious cycle" established between tumor growth and osteolysis aggravates the process of breast cancer bone metastasis, leading to life-threatening skeletal-related events that severely reduce survival and quality of life. To effectively interrupt the "vicious cycle", innovative therapeutic strategies that not only reduce osteolysis but also relieve tumor burden are urgently needed. Herein, a bone-seeking moiety, alendronate (ALN), functionalized coordination polymer nanoparticles (DZ@ALN) co-delivering cisplatin prodrug (DSP) and antiresorptive agent zoledronate (ZOL) via Zn²⁺ crosslinking for combination therapy was reported. The versatile DZ@ALN with a diameter of about 40 nm can cross the fissure in the bone marrow sinus capillaries, and possesses an excellent bone-seeking ability both in vitro and in vivo. Additionally, DZ@ALN could synergistically inhibit the proliferation of cancer cells, suppress the formation of osteoclast-like cells and induce the apoptosis of osteoclasts in vitro. Importantly, it could preferentially accumulate in bone affected site, remarkably inhibit the proliferation of tumor cells, relieving bone pain, and significantly inhibit the activation of osteoclasts, protecting the bone from destruction in vivo, eventually leading to the breakdown of "vicious cycle" without inducing obvious systemic toxicity. This innovative nanoagent combines chemotherapy and osteolysis inhibition, exhibiting an inspiring strategy for effective treatment of bone metastasis.

A versatile and multifunctional metal-organic framework nanocomposite toward chemo-photodynamic therapy

Previously most of the applications of targeting components have been based on the enhanced permeability and retention effect achieved using folic acid, which consider the side effects of the targeting components to some extent. Herein, we report a new strategy to decorate the surface of MOFs using a pemetrexed (MTA) targeting molecule, affording a new drug delivery system of ALA@UIO-66-NH-FAM/MTA (ALA = 5-amino-levulinic acid and FAM = 5-carboxyfluorescein). The confocal microscopy and flow cytometry results showed that ALA@UIO-66-NH-FAM/MTA presented a better targeting effect compared to ALA@UIO-66-NH-FAM/FA (FA = folic acid) and indicated a gradually increasing tendency of the targeting effect with the increasing expression of folate receptors on the tumor cell cytomembrane. Furthermore, the cytotoxicity experiment indicates that the combination of chemotherapy and photodynamic therapy is a more effective therapy model than single chemotherapy and photodynamic therapy. This work demonstrates the first attempt at folic acid antagonist (MTA) modification for NMOFs, providing a new concept for the design of MOFs with folate receptor targeting capacity for clinical applications.

Nanomaterials for Cardiac Tissue Engineering

End stage heart failure is a major cause of death in the US. At present, organ transplant and left-ventricular assist devices remain the only viable treatments for these patients. Cardiac tissue engineering presents the possibility of a new option. Nanomaterials such as gold nanorods (AuNRs) and carbon nanotubes (CNTs) present unique properties that are beneficial for cardiac tissue engineering approaches. In particular, these nanomaterials can modulate electrical conductivity, hardness, and roughness of bulk materials to improve tissue functionality. Moreover, they can deliver bioactive cargo to affect cell phenotypes. This review covers recent advances in the use of nanomaterials for cardiac tissue engineering.

Two-dimensional metal organic frameworks for biomedical applications

Two-dimensional (2D) metal organic frameworks (MOFs), are an emerging class of layered nanomaterials with well-defined structure and modular composition. The unique pore structure, high flexibility, tunability, and ability to introduce desired functionality within the structural framework, have led to potential use of MOFs in biomedical applications. This article critically reviews the application of 2D MOFs for therapeutic delivery, tissue engineering, bioimaging, and biosensing. Further, discussion on the challenges and strategies in next generation of 2D MOFs are also included. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Metal-Organic Framework (MOF)-Based Drug Delivery

Background:

Developing a controllable drug delivery system is imperative and important to reduce side effects and enhance the therapeutic efficacy of drugs. Metal-organic frameworks (MOFs) an emerging class of hybrid porous materials built from metal ions or clusters bridged by organic linkers have attracted increasing attention in the recent years owing to the unique physical structures possessed, and the potential for vast applications. The superior properties of MOFs, such as well-defined pore aperture, tailorable composition and structure, tunable size, versatile functionality, high agent loading, and improved biocompatibility, have made them promising candidates as drug delivery hosts. MOFs for drug delivery is of great interest and many very promising results have been found, indicating that these porous solids exhibit several advantages over existing systems.

Objective:

This review highlights the latest advances in the synthesis, functionalization, and applications of MOFs in drug delivery, and has classified them using drug loading strategies. Finally, challenges and future perspectives in this research area are also outlined.

Recent development of amorphous metal coordination polymers for cancer therapy

Nanoscale metal coordination polymers (NCPs), built from metal ions and organic ligands, have attracted tremendous interest in biomedical applications. This is mainly due to their mesoporous structure, tunable size and morphology and versatile functionality. NCPs can be further divided into nanoscale metal-organic frameworks (NMOFs) and amorphous coordination polymer particles (ACPPs) depending on their structural crystallinity. NMOFs as nanocarriers have been extensively reviewed. However, the highlights of ACPPs as theranostic nanoplatforms are still limited. In this review, the recent progress of ACPPs as theranostic nanoplatforms is summarized based on what types of organic linkers used. The ACPPs are divided into three main parts: photosensitizers-based ACPPs, chemical drugs-based ACPPs, and biomolecules-based ACPPs. Finally, the prospects and challenges of the ACPPs for enhanced biomedical applications are also discussed. STATEMENT OF SIGNIFICANCE: Over the last decades, amorphous metal coordination polymers (ACPPs), constructed by metal ions and organic linkers, have attracted enormous interest in cancer treatment owing to their high drug loading capability, facile synthetic procedures, low long-term toxicity, and mild preparation conditions. In this review, we highlight the recent progress of ACPPs for biomedical application based on different types of organic building blocks including photosensitizers, chemical drugs, and biomolecules. Moreover, the prospects and challenges of ACPPs for clinical application are also discussed. We hope this review entitled "Recent development of amorphous metal coordination polymers for cancer therapy" would arise the researchers' interest in this field to accelerate their clinical application in cancer therapy.

Development of a Tau-Targeted Drug Delivery System Using a Multifunctional Nanoscale Metal-Organic Framework for Alzheimer's Disease Therapy

Alzheimer's disease (AD) is a widespread and burdensome neurodegenerative disease; effective diagnostic methods are lacking, and it remains incurable. The clinical applications of nanoscale metal-organic frameworks (NMOFs) have mainly focused on disease diagnosis and treatment of cancer. A multifunctional NMOF-based nanoplatform was successfully developed for the application in AD diagnosis and therapy. The magnetic nanomaterial Fe-MIL-88B-NH₂ was selected to encapsulate methylene blue (MB, a tau aggregation inhibitor) and used as a magnetic resonance contrast material. Subsequently, the targeting reagent 5-amino-3-(pyrrolo[2,3-c]pyridin-1-yl)isoquinoline (defluorinated MK6240, DMK6240) was connected to the surface of Fe-MIL-88B-NH₂ via 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) to enhance hyperphosphorylated tau targeting, resulting in the formation of an advanced drug delivery system, Fe-MIL-88B-NH₂-NOTA-DMK6240/MB. The surface properties of Fe-MIL-88B-NH₂-NOTA-DMK6240/MB enable outstanding magnetic resonance imaging capability, as well as amelioration of AD symptoms in vitro and in vivo via the inhibition of hyperphosphorylated tau aggregation and impediment of neuronal death. In conclusion, a tau-targeted drug delivery platform with both disease diagnostics and treatment functions was developed in order to promote new applications of MOFs in the fields of AD and has potential applications in other neurodegenerative diseases.

Development of biological metal-organic frameworks designed for biomedical applications: from bio-sensing/bio-imaging to disease treatment

Metal-organic frameworks (MOFs) are built using various organic ligands and metal ions (or clusters). With properties of high porosity, tunable chemical composition, and potential for post-synthetic modification, they have been applied in biomedicine, especially in bio-sensing, bio-imaging, and drug delivery. Since organic ligands and metal centers (ions or clusters) in the structure of MOFs can directly influence the property, function, and performance of MOFs, strict screening of organic ligands and metal centers is necessary. Especially, to improve the application of MOFs in the field of biomedicine, biocompatible organic ligands with low toxicity are desirable. In recent years, biological metal-organic frameworks (bio-MOFs) with ideal biocompatibility and diverse functionality have attracted wide attention. Endogenous biomolecules, including nucleobases, amino acids, peptides, proteins, porphyrins and saccharides, are employed as frameworks for MOF construction. These biological ligands coordinate with diverse metal centers in different ways, leading to the structural diversity of bio-MOFs. In this review, we summarize the organic ligand selectivity in constructing different types of bio-MOFs and their influence in biomedical applications with attractive new functions.

Drug-Loaded Lipid-Coated Hybrid Organic-Inorganic "Stealth" Nanoparticles for Cancer Therapy

Hybrid porous nanoscale metal organic frameworks (nanoMOFs) made of iron trimesate are attracting increasing interest as drug carriers, due to their high drug loading capacity, biodegradability, and biocompatibility. NanoMOF surface modification to prevent clearance by the innate immune system remains still challenging in reason of their high porosity and biodegradable character. Herein, FDA-approved lipids and poly(ethylene glycol) (PEG)-lipid conjugates were used to engineer the surface of nanoMOFs by a rapid and convenient solvent-exchange deposition method. The resulting lipid-coated nanoMOFs were extensively characterized. For the first time, we show that nanoMOF surface modification with lipids affords a better control over drug release and their degradation in biological media. Moreover, when loaded with the anticancer drug Gem-MP (Gemcitabine-monophosphate), iron trimesate nanoMOFs acted as “Trojan horses” carrying the drug inside cancer cells to eradicate them. Most interestingly, the PEG-coated nanoMOFs escaped the capture by macrophages. In a nutshell, versatile PEG-based lipid shells control cell interactions and open perspectives for drug targeting.

A Nanomedicine Fabricated from Gold Nanoparticles-Decorated Metal-Organic Framework for Cascade Chemo/Chemodynamic Cancer Therapy

The incorporation of new modalities into chemotherapy greatly enhances the anticancer efficacy combining the merits of each treatment, showing promising potentials in clinical translations. Herein, a hybrid nanomedicine (Au/FeMOF@CPT NPs) is fabricated using metal-organic framework (MOF) nanoparticles and gold nanoparticles (Au NPs) as building blocks for cancer chemo/chemodynamic therapy. MOF NPs are used as vehicles to encapsulate camptothecin (CPT), and the hybridization by Au NPs greatly improves the stability of the nanomedicine in a physiological environment. Triggered by the high concentration of phosphate inside the cancer cells, Au/FeMOF@CPT NPs effectively collapse after internalization, resulting in the complete drug release and activation of the cascade catalytic reactions. The intracellular glucose can be oxidized by Au NPs to produce hydrogen dioxide, which is further utilized as chemical fuel for the Fenton reaction, thus realizing the synergistic anticancer efficacy. Benefitting from the enhanced permeability and retention effect and sophisticated fabrications, the blood circulation time and tumor accumulation of Au/FeMOF@CPT NPs are significantly increased. In vivo results demonstrate that the combination of chemotherapy and chemodynamic therapy effectively suppresses the tumor growth, meantime the systemic toxicity of this nanomedicine is greatly avoided.

ZnO/Nanocarbons-Modified Fibrous Scaffolds for Stem Cell-Based Osteogenic Differentiation

Currently, mesenchymal stem cells (MSCs)-based therapies for bone regeneration and treatments have gained significant attention in clinical research. Though many chemical and physical cues which influence the osteogenic differentiation of MSCs have been explored, scaffolds combining the benefits of Zn²⁺ ions and unique nanostructures may become an ideal interface to enhance osteogenic and anti-infective capabilities simultaneously. In this work, motivated by the enormous advantages of Zn-based metal-organic framework-derived nanocarbons, C-ZnO nanocarbons-modified fibrous scaffolds for stem cell-based osteogenic differentiation are constructed. The modified scaffolds show enhanced expression of alkaline phosphatase, bone sialoprotein, vinculin, and a larger cell spreading area. Meanwhile, the caging of ZnO nanoparticles can allow the slow release of Zn²⁺ ions, which not only activate various signaling pathways to guide osteogenic differentiation but also prevent the potential bacterial infection of implantable scaffolds. Overall, this study may provide new insight for designing stem cell-based nanostructured fibrous scaffolds with simultaneously enhanced osteogenic and anti-infective capabilities.

Microscopic and Mesoscopic Dual Postsynthetic Modifications of Metal-Organic Frameworks

We report the dual postsynthetic modification (PSM) of a metal-organic framework (MOF) involving the microscopic conversion of C-H bonds into C-C bonds and the mesoscopic introduction of hierarchical porosity. MOF crystals underwent single-crystal-to-single-crystal transformations during the electrophilic aromatic substitution of Co₂ (m-DOBDC) (m-DOBDC^4- =4,6-dioxo-1,3-benzenedicarboxylate) with alkyl halides and formaldehyde. The steric hindrance caused by the proximity of the introduced functional groups to the coordination bonds reduced bond stability and facilitated the transformation into hierarchically porous mesostructures by etching with in situ generated protons (hydroniums) and halides. The numerous defect sites in the mesostructural MOFs are potential water-sorption sites. However, since the introduced functional groups are close to the main adsorption sites, even methyl groups are able to considerably decrease water adsorption, whereas hydroxy groups increase adsorption at low vapor pressures.

Multifunctional Hypoxia-Involved Gene Silencing Nanoplatform for Sensitizing Photochemotherapy

The integration of combinational photochemotherapy could achieve a promoted therapeutic performance by eliminating the frustrating side effects of each constitute, yet it is still confronted with severe therapeutic resistances that are associated with tumor hypoxia. Herein, we designed a multifunctional gene-therapy-promoted photochemotherapy strategy for specifically alleviating the hypoxia-associated therapeutic resistance. The pH-responsive zeolitic imidazolate framework-8 (ZIF-8) nanoparticles (CDHNs) facilitated the effective delivery of therapeutic agents (chlorin e6 (Ce6), doxorubicin (DOX), and HIF-1α siRNA) into the tumor for relieving specifically photochemotherapy resistance via sequential activation manners under the guidance of fluorescence imaging. The present all-in-one compact CDHNs system provides a smart and versatile multiply gained therapeutic strategy to activate the specific cellular pathways and is anticipated to boost future cancer diagnosis and post-treatment.

Inclusion and release of ant alarm pheromones from metal-organic frameworks

Zinc(ii) and zirconium(iv) metal-organic frameworks show uptake and slow release of the ant alarm pheromones 3-octanone and 4-methyl-3-heptanone. Inclusion of N-propyl groups on the MOFs allows for enhanced uptake and release over several months. In preliminary field trials, leaf cutting ants show normal behavioural responses to the released pheromones.

Review of the Biomolecular Modification of the Metal-Organ-Framework

Metal-organ frameworks (MOFs), as a kind of novel artificial material, have been widely studied in the field of chemistry. MOFs are capable of high loading capacities, controlled release, plasticity, and biosafety because of their porous structure and have been gradually functionalized as a drug carrier. Recently, a completely new strategy of combining biomolecules, such as oligonucleotides, polypeptides, and nucleic acids, with MOF nanoparticles was proposed. The synthetic bio-MOFs conferred strong protection and endowed the MOFs with particular biological functions. Biomolecular modification of MOFs to form bridges for communication between different subjects has received increased attention. This review will focus on bio-MOFs modification methods and discuss the advantages, applications, prospects, and challenges of using MOFs in the field of biomolecule delivery.

Luminescent lanthanide metal-organic framework nanoprobes: from fundamentals to bioapplications

Metal-organic frameworks (MOFs), a unique type of porous material characterized by high porosity, large internal surface area and remarkable structural tunability, have emerged as very attractive functional materials for a variety of applications. As a promising subclass of MOFs, lanthanide metal-organic frameworks (Ln-MOFs) integrate the unique advantages of MOFs and the intrinsic features of lanthanide ions, such as sharp emission bands, long luminescent lifetimes, large Stokes shifts, high color purity and high resistance to photobleaching. In this minireview, we provide a brief overview of the most recent advances in luminescent Ln-MOF nanoprobes, which covers from their chemical and physical fundamentals to bioapplications, including their synthetic strategies, optical properties and promising bioapplications in biodetection, bioimaging and therapy. Finally, some of the most important emerging trends and future efforts toward this rapidly evolving field are also envisioned.

Dual-Mode Avocado-like All-Iron Nanoplatform for Enhanced T1/T2 MRI-Guided Cancer Theranostic Therapy

Development of T₁/T₂ dual-mode MRI contrast agents that can also treat cancer is an attractive prospect for personalized precision medicine. Unfortunately, conventional contrast agents can suffer from toxicity and lack any ability to treat cancer. An all-iron T₁/T₂ MR imaging agent with photothermal and drug delivery capability would overcome these issues. Here, an avocado-like Fe³⁺/Fe₂O₃ composed T₁-T₂ dual-mode contrast agent based on Fe-TA coordination network (CNMN) is developed. This material possesses suitable longitudinal and transverse relaxation coefficients. Moreover, the strong heat generation property of Fe-TA endows CNMN with the capability to act as a potent photothermal agent. Furthermore, CNMN can also act as an effective delivery platform for the chemotherapeutic drug doxorubicin (DOX) to achieve high effective chemo-photothermal combination therapy. The work demonstrates reliable T₁-T₂ MRI-guided chemo-photothermal therapy for safe and effective clinical application.

Inorganic Porous Nanoparticles for Drug Delivery in Antitumoral Therapy

The use of nanoparticles in oncology to deliver chemotherapeutic agents has received considerable attention in the last decades due to their tendency to be passively accumulated in solid tumors. Besides this remarkable property, the surface of these nanocarriers can be decorated with targeting moieties capable to recognize malignant cells which lead to selective nanoparticle uptake mainly in the diseased cells, without affecting the healthy ones. Among the different nanocarriers which have been developed with this purpose, inorganic porous nanomaterials constitute some of the most interesting due to their unique properties such as excellent cargo capacity, high biocompatibility and chemical, thermal and mechanical robustness, among others. Additionally, these materials can be engineered to present an exquisite control in the drug release behavior placing stimuli-responsive pore-blockers or sensitive hybrid coats on their surface. Herein, the recent advances developed in the use of porous inorganic nanomedicines will be described in order to provide an overview of their huge potential in the look out of an efficient and safe therapy against this complex disease. Porous inorganic nanoparticles have been designed to be accumulated in tumoral tissues; once there to recognize the target cell and finally, to release their payload in a controlled manner.

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.

Reprogrammable fluorescence logic sensing for biomolecules via RNA-like coenzyme A-based coordination polymer

In this study, coenzyme A (CoA)-based coordination polymers (CPs) have been generated in situ by exploiting the reaction of thiols with metal ion (Au(III) or Ag(I)), which are dependent on both thiol-metal and aurophilic metal∙metal interaction. It is interesting to note that CPs-related biosensing capabilities toward some biomolecules including ascorbic acid (AA), cysteine (Cys) and glutathione (GSH) are also investigated via SYBR Green II (SGII)-derived fluorescence switchable mechanisms. The synthesized CPs display especial RNA-like structure and are capable of initiating the fluorescence of SGII. Conversely, AA, Cys or GSH can give rise to the structural destruction of RNA-like CPs, thus inhibiting the fluorescence signal, and quantitative detection of these biomolecules are achieved favorably with a detection limit of 7.2, 0.55 and 0.48 nM, respectively. Meanwhile, the fascinating fluorescence on-off property and simple synthetic process are employed to build a series of basic logic gates (YES, NOT, OR, AND, INHIBIT and NOR) and multiple configurable logic gates (OR-AND and OR-OR-INHIBIT) along with different logic inputs. In view of these, developing CoA-based CPs as a new material to execute logic operations provides a valuable platform to establish the next generation of advanced molecular devices for clinic diagnostic and biomedical research.

Nanoscale Metal-Organic Frameworks Generate Reactive Oxygen Species for Cancer Therapy

In the past 15 years, enormous progress has been made in cancer nanotechnology, and a several nanoparticles have entered clinical testing for cancer treatment. Among these nanoparticles are nanoscale metal-organic frameworks (nMOFs), a class of organic-inorganic hybrid nanomaterials constructed from metal binding sites and bridging ligands, which have attracted significant attention for their ability to integrate porosity, crystallinity, compositional and structural tunability, multifunctionality, and biocompatibility into a singular nanomaterial for cancer therapies. This Outlook article summarizes the progress on the design of nMOFs as nanosensitizers for photodynamic therapy (PDT), radiotherapy (RT), radiotherapy-radiodynamic therapy (RT-RDT), and chemodynamic therapy (CDT) via nMOF-mediated reactive oxygen species (ROS) generated under external energy stimuli or in the presence of endogenous chemical triggers. Inflammatory responses induced by nMOF-mediated ROS generation activate tumor microenvironments to potentiate cancer immunotherapy, extending the local treatment effects of nMOF-based ROS therapy to distant tumors via abscopal effects. Future research directions in nMOF-mediated ROS therapies and the prospect of clinical applications of nMOFs as cancer therapeutics are also discussed.

Carbonization of single polyacrylonitrile chains in coordination nanospaces

It has been over half a century since polyacrylonitrile (PAN)-based carbon fibers were first developed. However, the mechanism of the carbonization reaction remains largely unknown. Structural evolution of PAN during the preoxidation reaction, a stabilization reaction, is one of the most complicated stages because many chemical reactions, including cyclization, dehydration, and cross-linking reactions, simultaneously take place. Here, we report the stabilization reaction of single PAN chains within the one-dimensional nanochannels of metal–organic frameworks (MOFs) to study an effect of interchain interactions on the stabilization process as well as the structure of the resulting ladder polymer (LP). The stabilization reaction of PAN within the MOFs could suppress the rapid generation of heat that initiates the self-catalyzed reaction and inevitably provokes many side-reactions and scission of PAN chains in the bulk state. Consequently, LP prepared within the MOFs had a more extended conjugated backbone than the bulk condition.

Accommodation of polyacrylonitrile in MOFs facilitated and regulated the transformation to ladder polymer in the carbonization process.

Designing Stimuli-Responsive Upconversion Nanoparticles that Exploit the Tumor Microenvironment

Tailoring personalized cancer nanomedicines demands detailed understanding of the tumor microenvironment. In recent years, smart upconversion nanoparticles with the ability to exploit the unique characteristics of the tumor microenvironment for precise targeting have been designed. To activate upconversion nanoparticles, various bio-physicochemical characteristics of the tumor microenvironment, namely, acidic pH, redox reactants, and hypoxia, are exploited. Stimuli-responsive upconversion nanoparticles also utilize the excessive presence of adenosine triphosphate (ATP), riboflavin, and Zn²⁺ in tumors. An overview of the design of stimulus-responsive upconversion nanoparticles that precisely target and respond to tumors via targeting the tumor microenvironment and intracellular signals is provided. Detailed understanding of the tumor microenvironment and the personalized design of upconversion nanoparticles will result in more effective clinical translation.

Recent Progress in Metal-Free Covalent Organic Frameworks as Heterogeneous Catalysts

Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with conventional porous materials such as inorganic zeolite, active carbon, and metal-organic frameworks, COFs are a new type of porous materials with well-designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal-free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF-based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.

The Progress and Prospect of Zeolitic Imidazolate Frameworks in Cancer Therapy, Antibacterial Activity, and Biomineralization

The progressive development of zeolitic imidazolate frameworks (ZIFs), as a subfamily of metal-organic frameworks (MOFs), and their unique features, including tunable pore size, large surface area, high thermal stability, and biodegradability/biocompatibility, have made them attractive in the field of biomedicine, especially for drug delivery and biomineralization applications. The high porosity of ZIFs gives them the opportunity for encapsulating a high amount of therapeutic drugs, proteins, imaging cargos, or a combination of them to construct advanced multifunctional drug delivery systems (DDSs) with combined therapeutic and imaging capabilities. This review summarizes recent strategies on the design and fabrication of ZIF-based nansystems and their exploration in the biomedical field. First, recent developments for the adjustment of particle size, functionality, and morphology of ZIFs are discussed, which are important for achieving optimized therapeutic/theranostic nanosystems. Second, recent trends on the application of ZIF nanocarriers for the loading of diverse cargos, including anticancer medicines, antibiotic drugs, enzymes, proteins, photosensitizers, as well as imaging and photothermal agents, are investigated in order to understand how multifunctional DDSs can be designed based on the ZIF nanoparticles to treat different diseases, such as cancer and infection. Finally, prospects on the future research direction and applications of ZIF-based nanomedicines are discussed.

Biomedical Applications of Metal Organic Polygons and Polyhedra (MOPs)

Since the discovery and structural characterization of metal organic polygons and polyhedra (MOPs), scientists have explored their potential in various applications like catalysis, separation, storage, and sensing. In recent years, scientists have explored the potential of supramolecular MOPs in biomedical application. Pioneering works by Ehrlich, Rosenberg, Lippard, Stang and others have demonstrated that MOPs have great potential as a novel class of metallo-therapeutics that can deliver cargoes (drugs and dyes) selectively. In this article, we document the progress made over the past two decades on the biomedical applications of MOPs and discuss the future prospects of this emerging field.