Multifunctional Metal-Organic Framework Nanoprobe for Cathepsin B-Activated Cancer Cell Imaging and Chemo-Photodynamic Therapy

Enzyme-responsive design combined with photodynamic therapy for cancer treatment

Photodynamic therapy (PDT) is a noninvasive cancer treatment that has garnered significant attention in recent years. However, its application is still hampered by certain limitations, such as the hydrophobicity and low targeting of photosensitizers (PSs) and the hypoxia of the tumor microenvironment. Nevertheless, the fusion of enzyme-responsive drugs with PDT offers novel solutions to overcome these challenges. Utilizing the attributes of enzyme-responsive drugs, PDT can deliver PSs to the target site and selectively release them, thereby enhancing therapeutic outcomes. In this review, we spotlight recent advances in enzyme-responsive materials for cancer treatment and primarily delineate their application in combination with PDT.

Oxaliplatin-Loaded Mil-100(Fe) for Chemotherapy-Ferroptosis Combined Therapy for Gastric Cancer

Oxaliplatin (Oxa) is a commonly used chemotherapy drug in the treatment of gastric cancer, but its toxic side effects and drug resistance after long-term use have seriously limited its efficacy. Loading chemotherapy drugs with nanomaterials and delivering them to the tumor site are common ways to overcome the above problems. However, nanomaterials as carriers do not have therapeutic functions on their own, and the effect of single chemotherapy is relatively limited, so there is still room for progress in related research. Herein, we construct Oxa@Mil-100(Fe) nanocomposites by loading Oxa with a metal-organic framework (MOF) Mil-100(Fe) with high biocompatibility and a large specific surface area. The pore structure of Mil-100(Fe) is conducive to a large amount of Oxa loading with a drug-loading rate of up to 27.2%. Oxa@Mil-100(Fe) is responsive to the tumor microenvironment (TME) and can release Oxa and Fe3+ under external stimulation. On the one hand, Oxa can inhibit the synthesis of DNA and induce the apoptosis of gastric cancer cells. On the other hand, Fe3+ can clear overexpressed glutathione (GSH) in TME and be reduced to Fe2+, inhibiting the activity of glutathione peroxidase 4 (GPX4), leading to the accumulation of intracellular lipid peroxides (LPO), and at the same time releasing a large number of reactive oxygen species (ROS) through the Fenton reaction, inducing ferroptosis in gastric cancer cells. With the combination of apoptosis and ferroptosis, Oxa@Mil-100(Fe) shows a good therapeutic effect, and the killing effect on gastric cancer cells is obvious. In a nude mouse model of subcutaneous tumor transplantation, Oxa@Mil-100(Fe) shows a significant inhibitory effect on tumor growth, with an inhibition rate of nearly 60%. In addition to its excellent antitumor activity, Oxa@Mil-100(Fe) has no obvious toxic or side effects. This study provides a new idea and method for the combined treatment of gastric cancer.

Biomedical application of metal-organic frameworks (MOFs) in cancer therapy: Stimuli-responsive and biomimetic nanocomposites in targeted delivery, phototherapy and diagnosis

The nanotechnology is an interdisciplinary field that has become a hot topic in cancer therapy. Metal-organic frameworks (MOFs) are porous materials and hybrid composites consisted of organic linkers and metal cations. Despite the wide application of MOFs in other fields, the potential of MOFs for purpose of cancer therapy has been revealed by the recent studies. High surface area and porosity, significant drug loading and encapsulation efficiency are among the benefits of using MOFs in drug delivery. MOFs can deliver genes/drugs with selective targeting of tumor cells that can be achieved through functionalization with ligands. The photosensitizers and photo-responsive nanostructures including carbon dots and gold nanoparticles can be loaded in/on MOFs to cause phototherapy-mediated tumor ablation. The immunogenic cell death induction and increased infiltration of cytotoxic CD8+ and CD4+ T cells can be accelerated by MOF platforms in providing immunotherapy of tumor cells. The stimuli-responsive MOF platforms responsive to pH, redox, enzyme and ion can accelerate release of therapeutics in tumor site. Moreover, MOF nanocomposites can be modified ligands and green polymers to improve their selectivity and biocompatibility for cancer therapy. The application of MOFs for the detection of cancer-related biomarkers can participate in the early diagnosis of patients.

Recent Progress on Tumor Microenvironment-Activated NIR-II Phototheranostic Agents with Simultaneous Activation for Diagnosis and Treatment

Malignant tumors seriously threaten human life and well-being. Emerging Near-infrared II (NIR-II, 1000-1700 nm) phototheranostic nanotechnology integrates diagnostic and treatment modalities, offering merits including improved tissue penetration and enhanced spatiotemporal resolution. This remarkable progress has opened promising avenues for advancing tumor theranostic research. The tumor microenvironment (TME) differs from normal tissues, exhibiting distinct attributes such as hypoxia, acidosis, overexpressed hydrogen peroxide, excess glutathione, and other factors. Capitalizing on these attributes, researchers have developed TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic attributes concurrently. Therefore, developing TME-activatable NIR-II phototheranostic agents with diagnostic and therapeutic activation holds significant research importance. Currently, research on TME-activatable NIR-II phototheranostic agents is still in its preliminary stages. This review examines the recent advances in developing dual-functional NIR-II activatable phototheranostic agents over the past years. It systematically presents NIR-II phototheranostic agents activated by various TME factors such as acidity (pH), hydrogen peroxide (H2 O2 ), glutathione (GSH), hydrogen sulfide (H2 S), enzymes, and their hybrid. This encompasses NIR-II fluorescence and photoacoustic imaging diagnostics, along with therapeutic modalities, including photothermal, photodynamic, chemodynamic, and gas therapies triggered by these TME factors. Lastly, the difficulties and opportunities confronting NIR-II activatable phototheranostic agents in the simultaneous diagnosis and treatment field are highlighted.

A covalent organic framework-derived M1 macrophage mimic nanozyme for precise tumor-targeted imaging and NIR-II photothermal catalytic chemotherapy

Nanoprobes for efficient tumor-targeted imaging and therapy are urgently needed for clinical tumor theranostics. Herein, inspired by the heterogeneity of the tumor microenvironment, we report a covalent organic framework (COF)-derived biomimetic nanozyme for precise tumor-targeted imaging and NIR-II photothermal-catalysis-enhanced chemotherapy (PTCEC). Using a crystalline nanoscale COF as the precursor, a peroxidase-like porous N-doped carbonous nanozyme (PNC) was obtained, which was cloaked with an M1 macrophage cell membrane (M1m) to create a multifunctional biomimetic nanoprobe for tumor-targeted imaging and therapy. The M1m coating enabled the nanoprobe to target cancer cells and tumor tissues for highly efficient tumor imaging and drug delivery. The peroxidase-like activity of the PNC allowed for the conversion of intratumoral H2O2 into toxic ˙OH that synergized with its NIR-II photothermal effect to strengthen the chemotherapy. Therefore, highly efficient tumor-targeted imaging and NIR-II PTCEC were realized with an M1 macrophage mimic nanoprobe. This work provides a feasible tactic for a biomimetic theranostic nanoprobe and will inspire the development of new bioactive nanomaterials for clinical tumor theranostic applications.

Three Strategies in Engineering Nanomedicines for Tumor Microenvironment-Enabled Phototherapy

Canonical phototherapeutics have several limitations, including a lack of tumor selectivity, nondiscriminatory phototoxicity, and tumor hypoxia aggravation. The tumor microenvironment (TME) is characterized by hypoxia, acidic pH, and high levels of H2 O2 , GSH, and proteases. To overcome the shortcomings of canonical phototherapy and achieve optimal theranostic effects with minimal side effects, unique TME characteristics are employed in the development of phototherapeutic nanomedicines. In this review, the effectiveness of three strategies for developing advanced phototherapeutics based on various TME characteristics is examined. The first strategy involves targeted delivery of phototherapeutics to tumors with the assistance of TME-induced nanoparticle disassembly or surface modification. The second strategy involves near-infrared absorption increase-induced phototherapy activation triggered by TME factors. The third strategy involves enhancing therapeutic efficacy by ameliorating TME. The functionalities, working principles, and significance of the three strategies for various applications are highlighted. Finally, possible challenges and future perspectives for further development are discussed.

Multifunctional fluorescent mesoporous carbon nanoprobe for MMP-2-activated cancer cell imaging and targeted photothermal therapy

The integration of cancer imaging with therapy in a simple system is warranted for precise cancer therapy. In this study, carboxyl-functionalized mesoporous carbon nanospheres (MCN) which are efficient photothermal agents and excellent fluorescence quenchers, were used for cancer cell imaging and selective photothermal therapy (PTT) applications. Using MCN, a matrix metalloproteinase-2 (MMP-2)- responsive theranostic nanoprobe was generated by functionalizing an MMP-2-specific fluorescent-labeled PLGVR sequence on the surface of MCN. The nanoprobe not only can be used to detect MMP-2 with a low detection limit of 0.3 pg mL^-1, but also can achieve the sensitive intracellular MMP-2 imaging in living cells, validating the differentiation of cancer cells from healthy cells based on the recovered fluorescence intensity. More importantly, selective cancer PTT was achieved using MMP-2-triggered cancer cell imaging. Our in vitro studies showed that by regulating the power density and irradiation time, the nanoprobe can effectively kill cancer cells via PTT. Our strategy opens new avenues for precision medicine, especially phototherapy.

Fe-Based Metal Organic Frameworks (Fe-MOFs) for Bio-Related Applications

Metal-organic frameworks (MOFs) are porous materials composed of metal ions and organic ligands. Due to their large surface area, easy modification, and good biocompatibility, MOFs are often used in bio-related fields. Fe-based metal-organic frameworks (Fe-MOFs), as important types of MOF, are favored by biomedical researchers for their advantages, such as low toxicity, good stability, high drug-loading capacity, and flexible structure. Fe-MOFs are diverse and widely used. Many new Fe-MOFs have appeared in recent years, with new modification methods and innovative design ideas, leading to the transformation of Fe-MOFs from single-mode therapy to multi-mode therapy. In this paper, the therapeutic principles, classification, characteristics, preparation methods, surface modification, and applications of Fe-MOFs in recent years are reviewed to understand the development trends and existing problems in Fe-MOFs, with the view to provide new ideas and directions for future research.

Metal-organic framework decorated with glycyrrhetinic acid conjugated chitosan as a pH-responsive nanocarrier for targeted drug delivery

Stimulus-responsive nanomaterials have become a hot spot in controllable drug delivery systems researches owing to their spatiotemporal controllable properties based on the differences between tumor microenvironment and normal tissue. Herein, iron (III) carboxylate metal-organic framework nanoparticles coated with glycyrrhetinic acid-chitosan conjugate (MIL-101/GA-CS) were successfully fabricated and acted as the pH-responsive and target-selective system to deliver doxorubicin (DOX) for hepatocellular carcinoma (HCC) therapy. The prepared nanocarrier possess the advantages of uniform size, comparable drug loading efficiency (28.89 %), and superior pH-dependent controlled drug release (DOX release of 2.74 % and 89.18 % within 72 h at pH 7.4 and 5.5, respectively). In vitro cytotoxicity assays showed that the drug-loaded nanocarriers exhibited excellent inhibitory effects on HepG2 cells due to the sustained release of DOX, while the nanocarriers showed no significant toxicity. Furthermore, cell uptake experiments demonstrated that MIL-101-DOX/GA-CS could target HepG2 cells based on receptor-dependent internalization of glycyrrhetinic acid-receptors-mediated (GA-receptors). In vitro 3D hepatoma cell microspheres experiments showed that MIL-101-DOX/GA-CS had excellent penetration and tumor killing ability. Therefore, MIL-101-DOX/GA-CS nanoparticles have a prospective application in cancer therapy as a pH-responsive controlled drug delivery system.

Targeting telomerase utilizing zeolitic imidazole frameworks as non-viral gene delivery agents across different cancer cell types

Telomerase, a ribonucleoprotein coded by the hTERT gene, plays an important role in cellular immortalization and carcinogenesis. hTERT is a suitable target for cancer therapeutics as its activity is highly upregulated in most of cancer cells but absent in normal somatic cells. Here, by employing the two Metal-Organic Frameworks (MOFs), viz. ZIF-C and ZIF-8, based biomineralization we encapsulate Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR)/Cas9 plasmid system that targets hTERT gene (CrhTERT) in cancer cells. When comparing the two biocomposites, ZIF-C shows the better loading capacity and cell viability. The loaded plasmid in ZIF-C is highly protected against enzymatic degradation. CrhTERT@ZIF-C is efficiently endocytosed by cancer cells and the subcellular release of CrhTERT leads to telomerase knockdown. The resultant inhibition of hTERT expression decreases cellular proliferation and causing cancer cell death. Furthermore, hTERT knockdown shows a significant reduction in tumour metastasis and alters protein expression. Collectively we show the high potential of ZIF-C-based biocomposites as a promising general tool for gene therapy of different types of cancers.

Metal-Organic Frameworks Applications in Synergistic Cancer Photo-Immunotherapy

Conventional cancer therapies, such as radiotherapy and chemotherapy, can have long-term side effects. Phototherapy has significant potential as a non-invasive alternative treatment with excellent selectivity. Nevertheless, its applicability is restricted by the availability of effective photosensitizers and photothermal agents, and its low efficacy when it comes to avoiding metastasis and tumor recurrence. Immunotherapy can promote systemic antitumoral immune responses, acting against metastasis and recurrence; however, it lacks the selectivity displayed by phototherapy, sometimes leading to adverse immune events. The use of metal-organic frameworks (MOFs) in the biomedical field has grown significantly in recent years. Due to their distinct properties, including their porous structure, large surface area, and inherent photo-responsive properties, MOFs can be particularly useful in the fields of cancer phototherapy and immunotherapy. MOF nanoplatforms have successfully demonstrated their ability to address several drawbacks associated with cancer phototherapy and immunotherapy, enabling an effective and low-side-effect combinatorial synergistical treatment for cancer. In the coming years, new advancements in MOFs, particularly regarding the development of highly stable multi-function MOF nanocomposites, may revolutionize the field of oncology.

Metal-Organic Frameworks as Potential Agents for Extraction and Delivery of Pesticides and Agrochemicals

Pesticide contamination is a global issue, affecting nearly 44% of the global farming population, and disproportionately affecting farmers and agricultural workers in developing countries. Despite this, global pesticide usage is on the rise, with the growing demand of global food production with increasing population. Different types of porous materials, such as carbon and zeolites, have been explored for the remediation of pesticides from the environment. However, there are some limitations with these materials, especially due to lack of functional groups and relatively modest surface areas. In this regard, metal-organic frameworks (MOFs) provide us with a better alternative to conventionally used porous materials due to their versatile and highly porous structure. Recently, a number of MOFs have been studied for the extraction of pesticides from the environment as well as for targeted and controlled release of agrochemicals. Different types of pesticides and conditions have been investigated, and MOFs have proved their potential in agricultural applications. In this review, the latest studies on delivery and extraction of pesticides using MOFs are systematically reviewed, along with some recent studies on greener ways of pest control through the slow release of chemical compounds from MOF composites. Finally, we present our insights into the key issues concerning the development and translational applications of using MOFs for targeted delivery and pesticide control.

Recent advances of the core-shell MOFs in tumour therapy

Coordination chemistry has always been vital to explore the material prominence of metal-organic systems. The metal-organic chemistry plays a fundamental role in decisive structural features, which are accountable for tuning the properties of materials. Tumour therapy has become an important research field of medical treatment in the world. Metal-organic frameworks (MOFs) have attracted extensive interest in medical science research due to their large effective surface area, clear pore network, and critical catalytic performance. Compared with traditional MOF materials, MOF materials with core-shell structures have a higher loading rate and better stability, which can overcome a single function. They have been successfully used in tumour medical research and have excellent prospects for diagnosing and treating various tumours. The current review article thoroughly describes the various synthetic approaches for engineering core-shell MOF materials, the structural types, and the potential functional applications. We also discussed core-shell MOF materials for the various treatment of tumours, such as tumour chemotherapy, tumour phototherapy and tumour microenvironment anti-hypoxia therapy. In this paper, the synthesized procedures of core-shell MOFs and their applications for tumour treatment have been discussed, and their future research has prospected. The current improved strategies, challenges, and prospects are also presented because of the metal-organic chemistry governing the structural modification of core-shell MOFs for tumour therapy applications. Therefore, the present review article opens a new door for medicinal chemists to tune the structural features of the core-shell MOF materials to modulate tumour therapy with simple, low-cost materials for better human lives.

Nanoarchitectonics horizons: materials for life sciences

Nanoarchitectonics relies on the fabrication of materials at the atomic/molecular level to achieve the desired shape and function. Significant advances have been made in understanding the characteristics and spatial assemblies that contribute to material performance. Biomaterials undergo several changes when presented with various environmental cues. The ability to overcome such challenges, maintaining the integrity and effective functioning of native properties, can be regarded as a characteristic of a successful biomaterial. Control over the shape and efficacy of target materials can be tailored via various processes, like self-assembly, supramolecular chemistry, atomic/molecular manipulation, etc. Interplay between the physicochemical properties of materials and biomolecule recognition sites defines the structural rigidity in hierarchical structures. Materials including polymers, metal nanoparticles, nucleic acid systems, metal-organic frameworks, and carbon-based nanostructures can be viewed as promising prospects for developing biocompatible systems. This review discusses recent advances relating to such biomaterials for life science applications, where nanoarchitectonics plays a decisive role either directly or indirectly.

Integrating Au and ZnO nanoparticles onto graphene nanosheet for enhanced sonodynamic therapy

Sonodynamic therapy has attracted widespread attention for cancer treatment because of its noninvasiveness and high tissue-penetration ability. Generally, ultrasound irradiation of sonosensitizers produces separated electrons (e^-) and holes (h⁺), which inhibits cancer by producing reactive oxygen species (ROS). However, the separated electrons (e^-) and holes (h⁺) could easily recombine, lowering the yield of ROS and hindering the application of sonodynamic therapy (SDT). Herein, we present a highly efficient sonosensitizer system for enhanced sonodynamic therapy built on reduced graphene oxide (rGO) nanosheets, bridged ZnO and Au nanoparticles, coated with polyvinyl pyrrolidone (PVP). The ultrasound irradiation activates ZnO nanoparticles to generate separated electron-hole (e^--h⁺) pairs, and the rGO nanosheets facilitate electron transfer from ZnO to Au nanoparticles because of the narrow band gap of rGO, which could efficiently restrain the recombination of the e^--h⁺ pairs, thereby significantly augmenting the production of ROS to kill cancer cells, such as U373MG, HeLa, and CT26 cells. Moreover, rGO nanosheets integrated with Au nanoparticles could catalyze the endogenous decomposition of H₂O₂ into O₂, which can alleviate hypoxic tumor microenvironment (TME). Therefore, the rational design of Au-rGO-ZnO@PVP nanomaterials can not only improve the efficiency of sonodynamic therapy, but also mitigate the hypoxic tumor microenvironment, which would provide a new perspective in the development of efficient sonosensitizers.

ELECTRONIC SUPPLEMENTARY MATERIAL

Supplementary material (the UV-vis-NIR absorption spectra of the DPBF and the RhB, biological effect assessment of the Au-rGO-ZnO@PVP, and the inhibition rate of tumor under different treatments during the animal study) is available in the online version of this article at 10.1007/s12274-022-4599-5.

Hybrid liposome/metal-organic framework as a promising dual-responsive nanocarriers for anticancer drug delivery

In this work, liposome-coated iron (III) benzene-1,3,5-tricarboxylate (Fe-BTC) metal-organic framework is examined as a promising pH/Ultrasound dual-responsive nanocarriers for doxorubicin (DOX) delivery. The successful coating of the MOF particles (Lip-Fe-BTC) with the phospholipid bilayer (PBL) was established by direct fusion into the synthesized liposomes. The liposome coating was verified using several techniques, including dynamic light scattering (DLS) and transmission electron microscopy (TEM). The DLS measurements showed an increase in the average particle diameter of liposomes from 150 nm to 163.1 nm for Lip-Fe-BTC particles. The Fe-BTC particles had the highest average particle diameter (287.3 nm). These results demonstrated that the PBL reduced the aggregation of the particles and improved their dispersity in the release medium. The TGA results demonstrated the MOF's excellent thermal stability. Furthermore, the nanocarrier's loading efficiency and capacity were determined to be ~90% and ~13.5 wt%, respectively. The in-vitro DOX release experiments demonstrated that the DOX-loaded Fe-BTC and liposome-coated Fe-BTC particles showed good pH and US dual-responsive capability, making them promising nanocarriers for drug delivery. The application of US enhanced DOX release from both Fe-BTC and liposome-coated Fe-BTC. In the case of Fe-BTC-DOX particles, the application of US enhanced the DOX release to around 38% and 67%, at pH levels of 7.4 and 5.3, respectively. Similarly, DOX release from the Lip-Fe-BTC-DOX particles reached ~35% and ~53%, at pH levels of 7.4 and 5.3, respectively. The MTT assay showed the biocompatibility and low cytotoxicity of these nanocarriers below 100 µg/ml.

A Potent Strategy of Combinational Blow Toward Enhanced Cancer Chemo-Photodynamic Therapy via Sustainable GSH Elimination

Excessive glutathione (GSH), which is produced owing to abnormal metabolism of tumor cells, scavenges photo-induced reactive oxygen species (ROS) and consumes chemotherapeutic drugs, thereby attenuating the efficacy of photodynamic therapy and chemotherapy, respectively. Predominant strategies for GSH inhibition involve its chemical depletion, which only leads to a temporary therapeutic effect because GSH is replenished via various compensatory routes in tumor cells. Here, a versatile GSH-inhibiting nanosystem (termed PCNPs) for persistent synergistic therapy of cancer is reported. The porous skeleton of PCNPs allows easy encapsulation of buthionine sulfoximine (BSO) to sustainably suppress the biosynthesis of GSH. Thus, PCNPs not only demonstrate a prolonged release of BSO and improve drug utilization for efficient chemotherapy, but also act as an efficient photo-induced singlet oxygen radical generator that prevents the loss of ROS, thereby enhancing photodynamic therapy. In addition, the liposomal coating prevents cargo release in the blood, improves the accumulation of PCNPs at the tumor site, and promotes the cellular uptake of oxaliplatin and BSO. This strategy is applicable to ROS-based therapy and chemotherapy, which are suppressed by GSH, and may further enhance the synergistic effect of GSH-restrained therapy.

Encapsulation, Release, and Cytotoxicity of Doxorubicin Loaded in Liposomes, Micelles, and Metal-Organic Frameworks: A Review

Doxorubicin (DOX) is one of the most widely used anthracycline anticancer drugs due to its high efficacy and evident antitumoral activity on several cancer types. However, its effective utilization is hindered by the adverse side effects associated with its administration, the detriment to the patients’ quality of life, and general toxicity to healthy fast-dividing cells. Thus, delivering DOX to the tumor site encapsulated inside nanocarrier-based systems is an area of research that has garnered colossal interest in targeted medicine. Nanoparticles can be used as vehicles for the localized delivery and release of DOX, decreasing the effects on neighboring healthy cells and providing more control over the drug’s release and distribution. This review presents an overview of DOX-based nanocarrier delivery systems, covering loading methods, release rate, and the cytotoxicity of liposomal, micellar, and metal organic frameworks (MOFs) platforms.

Metal-Organic Frameworks for Bioimaging: Strategies and Challenges

Metal-organic frameworks (MOFs), composited with metal ions and organic linkers, have become promising candidates in the biomedical field own to their unique properties, such as high surface area, pore-volume, tunable pore size, and versatile functionalities. In this review, we introduce and summarize the synthesis and characterization methods of MOFs, and their bioimaging applications, including optical bioimaging, magnetic resonance imaging (MRI), computed tomography (CT), and multi-mode. Furthermore, their bioimaging strategies, remaining challenges and future directions are discussed and proposed. This review provides valuable references for the designing of molecular bioimaging probes based on MOFs.

Current status and future prospects of nanoscale metal–organic frameworks in bioimaging

The importance of diagnosis and in situ monitoring of lesion regions and transportation of bioactive molecules has a pivotal effect on successful treatment, reducing side effects, and increasing the chances of survival in the case of diseases.

Intracellular Enzyme-Responsive Profluorophore and Prodrug Nanoparticles for Tumor-Specific Imaging and Precise Chemotherapy

Responsive drug delivery systems possess great potential in disease diagnosis and treatment. Herein, we develop an activatable prodrug and fluorescence imaging material by engineering the endogenous NAD(P)H:quinone oxidoreductase-1 (NQO1) responsive linker. The as-prepared nanomaterials possess the NQO1-switched drug release and fluorescence enablement, which realizes the tumor-specific chemotherapy and imaging in living mice. The enzyme-sensitive prodrug nanoparticles exhibit selectively potent anticancer performance to NQO1-positive cancer and ignorable off-target toxicity. This work provides an alternative strategy for constructing smart prodrug nanoplatforms with precision, selectivity, and practicability for advanced cancer imaging and therapy.

Inorganic Nanomaterials with Intrinsic Singlet Oxygen Generation for Photodynamic Therapy

Inorganic nanomaterials with intrinsic singlet oxygen (1 O2 ) generation capacity, are emerged yet dynamically developing materials as nano-photosensitizers (NPSs) for photodynamic therapy (PDT). Compared to previously reported nanomaterials that have been used as either carriers to load organic PSs or energy donors to excite the attached organic PSs through a Foster resonance energy transfer process, these NPSs possess intrinsic 1 O2 generation capacity with extremely high 1 O2 quantum yield (e.g., 1.56, 1.3, 1.26, and 1.09) than any classical organic PS reported to date, and thus are facilitating to make a revolution in PDT. In this review, the recent advances in the development of various inorganic nanomaterials as NPSs, including metal-based (gold, silver, and tungsten), metal oxide-based (titanium dioxide, tungsten oxide, and bismuth oxyhalide), metal sulfide-based (copper and molybdenum sulfide), carbon-based (graphene, fullerene, and graphitic carbon nitride), phosphorus-based, and others (hybrids and MXenes-based NPSs) are summarized, with an emphasis on the design principle and 1 O2 generation mechanism, and the photodynamic therapeutic performance against different types of cancers. Finally, the current challenges and an outlook of future research are also discussed. This review may provide a comprehensive account capable of explaining recent progress as well as future research of this emerging paradigm.

Microneedle-mediated delivery of MIL-100(Fe) as a tumor microenvironment-responsive biodegradable nanoplatform for O2-evolving chemophototherapy

The low oxygen level in tumors significantly reduces the antitumor efficacy of photodynamic therapy (PDT). The provision of O₂ and monomeric hydrophobic photosensitizers (PSs) under physiological conditions would greatly help to shrink malignant tumors. We take advantage of the high porosity and multifunctionality of metal-organic frameworks (MOFs) to fabricate a simple all-in-one nanoplatform mediated by microneedle delivery to achieve synergistic O₂ evolution and chemophototherapy. An iron(III)-based MOF (MIL-100(Fe)) acted not only as a vehicle for the concurrent delivery of zinc phthalocyanine (ZnPc) and doxorubicin hydrochloride (Dox), but also to supply O₂ by decomposing hydrogen peroxide (H₂O₂) in the tumor microenvironment via a Fenton-like reaction. In vitro and in vivo experiments indicated that the nanoplatform had excellent biocompatibility and exerted enhanced anticancer effects. The encapsulated drug was sustainably released from the nanoplatform skeleton in response to acidic tumor microenvironments. Moreover, upon 660 nm light irradiation, ZnPc effectively produced reactive oxygen species (ROS) due to the reduction of hypoxia by MIL-100(Fe). A microneedle technique was adopted to directly deliver the nanoplatform into superficial tumors rather than via systemic circulation. Hence, this study provides a new strategy for more efficient chemophototherapy of hypoxic superficial tumors.

Highly Efficient Encapsulation of Doxorubicin Hydrochloride in Metal-Organic Frameworks for Synergistic Chemotherapy and Chemodynamic Therapy

Iron-based metal-organic frameworks (MOFs) have been reported to have great potential for encapsulating doxorubicin hydrochloride (DOX), which is a frequently used anthracycline anticancer drug. However, developing a facile approach to realize high loading capacity and efficiency as well as controlled release of DOX in MOFs remains a huge challenge. Herein, we synthesized water-stable MIL-101(Fe)-C₄H₄ through a microwave-assisted method. It was found the nano-MOFs acted as nanosponges when soaked in a DOX alkaline aqueous solution with a loading capacity experimentally up to 24.5 wt %, while maintaininga loading efficiency as high as 98%. The mechanism of the interaction between DOX and nanoMOFs was investigated by absorption spectra and density functional theory (DFT) calculations, which revealed that the deprotonated DOX was electrostatically adsorbed to the unsaturated Fe₃OCl(COO)₆·H₂O (named Fe₃ trimers). In addition, the as-designed poly(ethylene glycol-co-propylene glycol) (F127) modified nanoparticles (F127-DOX-MIL) could be decomposed under the stimulation of glutathione (GSH) and ATP. As a result, DOX and Fe(III) ions were released, and they could undergo a Fenton-like reaction with the endogenous H₂O₂ to generate the highly toxic hydroxyl radical (·OH). The in vitro experiments indicated that F127-DOX-MIL could cause remarkable Hela cells inhibition through chemotherapy and chemodynamic therapy. Our study provides a new strategy to design a GSH/ATP-responsive drug-delivery nanosystem for chemo/chemodynamic therapy.

Metal-Organic Framework-Based Nanoagents for Effective Tumor Therapy by Dual Dynamics-Amplified Oxidative Stress

Overproduction of reactive oxygen species (ROS) within tumors can cause oxidative stress on tumor cells to induce death, which has motivated us to develop ROS-mediated tumor therapies, such as typical photodynamic therapy (PDT) and Fenton reaction-mediated chemodynamic therapy (CDT). However, these therapeutic modalities suffer from compromised treatment efficacy owing to their limited generation of highly reactive ROS in a tumor microenvironment (TME). In this work, a nanoscale iron-based metal-organic framework, MIL-101(Fe), is synthesized as a Fenton nanocatalyst to perform the catalytic conversion of hydroxyl radicals (·OH) from hydrogen peroxide (H₂O₂) under the acidic environment and as a biocompatible and biodegradable nanocarrier to deliver a 5,10,15,20-tetrakis(4-carboxyphenyl)porphyrin (TCPP) photosensitizer for light-activated singlet oxygen (¹O₂) generation. By coupling such chemodynamic/photodynamic effects, the photosensitizer-integrated nanoagents (MIL-101(Fe)@TCPP) could enable more ROS production within tumors to induce amplified oxidative damage for tumor-specific synergistic therapy. In vitro results show that MIL-101(Fe)@TCPP nanoagents achieve the acid-responsive CDT and effective PDT, and synergistic CDT/PDT provides an enhanced therapeutic effect. Ultimately, based on such synergistic therapy, MIL-101(Fe)@TCPP nanoagents cause a significant tumor growth inhibition in vivo without severe side effects, showing great potential for anti-tumor application.

Nanoscale metal-organic frameworks for tumor phototherapy

Metal-Organic Frameworks (MOFs) are constructed from metal ions/cluster nodes and functional organic ligands through coordination bonds. Owing to the advantages of diverse synthetic methods, easy modification after synthesis, large adsorption capacity for heavy metals, and short equilibrium time, considerable attention has recently been paid to MOFs for tumor phototherapy. Through rational tuning of metal ions and ligands, MOFs present abundant properties for various applications. Light-triggered phototherapy, including photodynamic therapy (PDT) and photothermal therapy (PTT), is an emerging cancer treatment approach. Nanosized MOFs can be applied as phototherapeutic agents to accomplish phototherapy with excellent phototherapeutic efficacy. This review outlines the latest advances in the field of phototherapy with various metal ion-based MOFs.

The recent progress on metal-organic frameworks for phototherapy

Some infectious or malignant diseases such as cancers are seriously threatening the health of human beings all over the world. The commonly used antibiotic therapy cannot effectively treat these diseases within a short time, and also bring about adverse effects such as drug resistance and immune system damage during long-term systemic treatment. Phototherapy is an emerging antibiotic-free strategy to treat these diseases. Upon light irradiation, phototherapeutic agents can generate cytotoxic reactive oxygen species (ROS) or induce a temperature increase, which leads to the death of targeted cells. These two kinds of killing strategies are referred to as photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. So far, many photo-responsive agents have been developed. Among them, the metal-organic framework (MOF) is becoming one of the most promising photo-responsive materials because its structure and chemical compositions can be easily modulated to achieve specific functions. MOFs can have intrinsic photodynamic or photothermal ability under the rational design of MOF construction, or serve as the carrier of therapeutic agents, owing to its tunable porosity. MOFs also provide feasibility for various combined therapies and targeting methods, which improves the efficiency of phototherapy. In this review, we firstly investigated the principles of phototherapy, and comprehensively summarized recent advances of MOF in PDT, PTT and synergistic therapy, from construction to modification. We expect that our demonstration will shed light on the future development of this field, and bring it one step closer to clinical trials.

A MnO2-coated multivariate porphyrinic metal-organic framework for oxygen self-sufficient chemo-photodynamic synergistic therapy

Lately, chemotherapy and photodynamic therapy (PDT) synergistic therapy has become a promising anti-cancer treatment mean. However, the hypoxia in tumor leads to huge impediments to the oxygen-dependentPDT effects. In this work, a multifunctional nanoplatform (TUDMP) based on a multivariable porphyrin-nMOFs core and a manganese dioxide (MnO₂) shell was prepared for relieving tumor hypoxia and enhancing chemo-photodynamic synergistic therapy performance. The obtained TUDMP nanoplatform could effectively catalyze the hydrolysis of hydrogen peroxide to generate oxygen and also lead to consumption of antioxidant GSH, thereby facilitating the production of cytotoxic reactive oxygen species (ROS) by photosensitizer under laser irradiation. More importantly, the decomposition of the MnO₂ shell would further promote the release of the loaded doxorubicin (DOX), and thus an efficient chemo-PDT synergistic therapy was realized. Both in vitro and in vivo experimental results demonstrated the oxygen self-sufficient multifunctional nanoplatform could exhibit significantly enhanced anticancer efficiencies compared with chemotherapy or PDT alone.

Delivery of oxaliplatin to colorectal cancer cells by folate-targeted UiO-66-NH2

Oxaliplatin is being used in different malignancies and several side effects are reported for patients taking Oxaliplatin, including peripheral neuropathy, nausea and vomiting, diarrhea, mouth sores, low blood counts, fatigue, loss of appetite, etc. Here we have developed a targeted anticancer drug delivery system based on folate-conjugated amine-functionalized UiO-66 for the delivery of oxaliplatin (OX). UiO-66-NH₂ (U) and UiO-66-NH₂-FA(FU) were pre-functionalized by the incorporation of folic acid (FA) into the structure via coordination of the carboxylate group of FA. The FTIR spectra of drug-loaded U and FU showed the presence of new carboxylic and aliphatic groups of OX and FA. Powder X-ray diffraction (PXRD) patterns were matched accordingly with the reference pattern and FESEM results showed semi-spherical particles (115-128 nm). The evaluated amounts of OX in U and FU were calculated 304.5 and 293 mg/g_, respectively. The initial burst release of OX was 15.7% per hour for U(OX) and 10.8% per hour for FU(OX). The final release plateau gives 62.9% and 52.3% for U(OX) and FU(OX). To evaluate the application of the prepared delivery platform, they were tested on colorectal cancer cells (CT-26) via MTT assay, cell migration assay, and spheroid model. IC₅₀ values obtained from MTT assay were 21.38, 95.50, and 18.20 μg/mL for OX, U(OX), and FU(OX), respectively. After three days of treatment, the CT26 spheroids at two doses of 500 and 50 μg/mL of U(OX) and FU(OX) showed volume reduction. Moreover, the oxidative behavior of the prepared systems within the cell was assessed by total thiol, malondialdehyde, and superoxide dismutase activity. The results showed that FU(OX) had higher efficacy in preventing the growth of CT-26 spheroid, and was more effective than oxaliplation in cell migration inhibition, and induced higher oxidative stress and apoptosis.

Current Status and Emerging Trend of Nanoshuttle in Biological Applications

Nanoshuttles are unique structures that resemble double-headed arrows or a nanorod with sharp tips for better penetration into the tumor cells, reduction of toxicity and minimization of off-targeting effect. These biologically- inspired multimetallic or bimetallic nano swimmers are capable of transporting cargoes from one end to another via self-propulsion in an efficient manner. Encapsulation with pH- and heat-sensitive polymers allows nanoshuttles to release cargos at the targeted site in a controlled fashion. This review article focuses on the methods of preparation and characterization of nanoshuttles with applications in the field of antineoplastic, antibacterial, erectile dysfunction, electrochemical biosensing, anticounterfeiting, on-demand and targeted delivery system for imaging as well as cell ablation therapy. Magnetic nanoshuttles exhibit modified optical properties for utilization in diagnostic imaging for sensitive and early diagnosis of diseases. Smart drug delivery is achieved when nanoshuttles are combined with nanomotors to exhibit distinctive, rapid and unidirectional movement in the bloodstream. Cost-effective synthesis of nanoshuttles will extend their applications in the commercial sectors by overcoming the limitations like scale-up and regulatory approval. In the near future, nanoshuttles will diversify in the fields of energy conversion, energy storage, 3D printing, stem cell fabrication and theranostics.

Applications of nanoscale metal-organic frameworks as imaging agents in biology and medicine

Nanoscale metal-organic frameworks (NMOFs) are an interesting and unique class of hybrid porous materials constructed by the self-assembly of metal ions/clusters with organic linkers. The high storage capacities, facile synthesis, easy surface functionalization, diverse compositions and excellent biocompatibilities of NMOFs have made them promising agents for theranostic applications. By combination of a large variety of metal ions and organic ligands, and incorporation of desired molecular functionalities including imaging modalities and therapeutic molecules, diverse MOF structures with versatile functionalities can be obtained and utilized in biomedical imaging and drug delivery. In recent years, NMOFs have attracted great interest as imaging agents in optical imaging (OI), magnetic resonance imaging (MRI), computed tomography (CT), positron emission tomography (PET) and photoacoustic imaging (PAI). Furthermore, the significant porosity of MOFs allows them to be loaded with multiple imaging agents and therapeutics simultaneously and applied for multimodal imaging and therapy as a single entity. In this review, which is intended as an introduction to the use of MOFs in biomedical imaging for a reader entering the subject, we summarize the up-to-date progress of NMOFs as bioimaging agents, giving (i) a broad perspective of the varying imaging techniques that MOFs can enable, (ii) the different routes to manufacturing functionalised MOF nanoparticles and hybrids, and (iii) the integration of imaging with differing therapeutic techniques. The current challenges and perspectives of NMOFs for their further clinical translation are also highlighted and discussed.

Hybrid nanoparticle composites applied to photodynamic therapy: strategies and applications

Photodynamic therapy (PDT), as a robust strategy, has long been applied to cancer treatment owing to the meaningful breakthroughs and unique advantages, including ignorable invasiveness and spatio-temporal selectivity. Numerous PDT agents, especially hybrid nanoparticle composite (hybrid)-based sensitizers consisting of an organic polymer and inorganic nanoparticles (NPs), feature the synergetic pros of the components, which have unlocked the additional potentials of PDT. Although reviews relating to the applications of hybrids to PDT have been previously reported, most of them only focus on the designs of smart hybrids integrating multimodal imaging-guided multiple treatment modalities. Traditional PDT treatment has several limitations, such as inadequate PDT agents accumulating in cancer tissues, inferior PDT effect due to the devastating cancer hypoxia environment, relevant systemic toxicity in non-intelligent stimulation response treatment systems, and serious dependence of PDT on external light sources. Many strategies have been developed for overcoming these limitations, including improvement of cancer-homing ability by introducing active targeting groups, remodeling of the cancer hypoxia environment through oxygen regulators, intratumor release of ROS through activatable molecules, and replacement of laser light by X-rays or self-luminescence. This review aims to summarize the most recent advances in designing hybrids for improving the therapeutic efficacy of PDT.

Supramolecular cancer nanotheranostics

Among the many challenges in medicine, the treatment and cure of cancer remains an outstanding goal given the complexity and diversity of the disease. Nanotheranostics, the integration of therapy and diagnosis in nanoformulations, is the next generation of personalized medicine to meet the challenges in precise cancer diagnosis, rational management and effective therapy, aiming to significantly increase the survival rate and improve the life quality of cancer patients. Different from most conventional platforms with unsatisfactory theranostic capabilities, supramolecular cancer nanotheranostics have unparalleled advantages in early-stage diagnosis and personal therapy, showing promising potential in clinical translations and applications. In this review, we summarize the progress of supramolecular cancer nanotheranostics and provide guidance for designing new targeted supramolecular theranostic agents. Based on extensive state-of-the-art research, our review will provide the existing and new researchers a foundation from which to advance supramolecular cancer nanotheranostics and promote translationally clinical applications.

Expanding the Limits of Photodynamic Therapy: The Design of Organelles and Hypoxia-Targeting Nanomaterials for Enhanced Photokilling of Cancer

Photodynamic therapy (PDT) is a minimally invasive clinical protocol that combines a nontoxic photosensitizer (PS), appropriate visible light, and molecular oxygen for cancer treatment. This triad generates reactive oxygen species (ROS) in situ, leading to different cell death pathways and limiting the arrival of nutrients by irreversible destruction of the tumor vascular system. Despite the number of formulations and applications available, the advancement of therapy is hindered by some characteristics such as the hypoxic condition of solid tumors and the limited energy density (light fluence) that reaches the target. As a result, the use of PDT as a definitive monotherapy for cancer is generally restricted to pretumor lesions or neoplastic tissue of approximately 1 cm in size. To expand this limitation, researchers have synthesized functional nanoparticles (NPs) capable of carrying classical photosensitizers with self-supplying oxygen as well as targeting specific organelles such as mitochondria and lysosomes. This has improved outcomes in vitro and in vivo. This review highlights the basis of PDT, many of the most commonly used strategies of functionalization of smart NPs, and their potential to break the current limits of the classical protocol of PDT against cancer. The application and future perspectives of the multifunctional nanoparticles in PDT are also discussed in some detail.

Recent advances in nanosized metal organic frameworks for drug delivery and tumor therapy

Metal organic-frameworks (MOFs) are novel materials that have attracted increasing attention for applications in a wide range of research, owing to their unique advantages including their small particle size, porous framework structure and high specific surface area. Because of their adjustable size, nanoscale MOFs (nano-MOFs) can be prepared as carriers of biotherapy drugs, thus enabling biotherapeutic applications. Nano-MOFs' metal ion catalytic activity and organic group functional characteristics can be exploited in biological treatments. Furthermore, the applications of nano-MOFs can be broadened by hybridization with other materials to form composites. This review focuses on the preparation and recent advances in nano-MOFs as drug carriers, therapeutic materials and functionalized materials in drug delivery and tumor therapy based on the single/multiple stimulus response of drug release to achieve the targeted therapy, offering a comprehensive reference for drug carrier design. At the end, the current challenges and prospects are discussed to provide significant insight into the design and applications of nano-MOFs in drug delivery and tumor therapy.

Smart metal organic frameworks: focus on cancer treatment

Metal–organic frameworks (MOFs), as a prominent category of hybrid porous materials, have been broadly employed as controlled systems of drug delivery due to their inherent interesting properties.

Recent Progress in the Development of Multifunctional Nanoplatform for Precise Tumor Phototherapy

Phototherapy, including photodynamic therapy and photothermal therapy, mainly relies on phototherapeutic agents (PAs) to produce heat or toxic reactive oxygen species (ROS) to kill tumors. It has attracted wide attention due to its merits of noninvasive properties and negligible drug resistance. However, the phototoxicity of conventional PAs is one of the main challenges for its potential clinical application. This is mainly caused by the uncontrolled distribution of PA in vivo, as well as the inevitable damage to healthy cells along the light path. Ensuring the generation of ROS or heat specific at tumor site is the key for precise tumor phototherapy. In this review, the progress of targeted delivery of PA and activatable phototherapy strategies based on nanocarriers for precise tumor therapy is summarized. The research progress of passive targeting, active targeting, and activatable targeting strategies in the delivery of PA is also described. Then, the switchable nanosystems for tumor precise phototherapy in response to tumor microenvironment, including pH, glutathione (GSH), protein, and nucleic acid, are highlighted. Finally, the challenges and opportunities of nanocarrier-based precise phototherapy are discussed for clinical application in the future.

Multifunctional metal-organic framework heterostructures for enhanced cancer therapy

Metal-organic frameworks (MOFs) are an emerging class of molecular crystalline materials built from metal ions or clusters bridged by organic linkers. By taking advantage of their synthetic tunability and structural regularity, MOFs can hierarchically integrate nanoparticles and/or biomolecules into a single framework to enable multifunctions. The MOF-protected heterostructures not only enhance the catalytic capacity of nanoparticle components but also retain the biological activity of biomolecules in an intracellular microenvironment. Therefore, the multifunctional MOF heterostructures have great advantages over single components in cancer therapy. In this review, we comprehensively summarize the general principle of the design and functional modulation of nanoscaled MOF heterostructures, and biomedical applications in enhanced therapy within the last five years. The functions of MOF heterostructures with a controlled size can be regulated by designing various functional ligands and in situ growth/postmodification of nanoparticles and/or biomolecules. The advances in the application of multifunctional MOF heterostructures are also explored for enhanced cancer therapies involving photodynamic therapy, photothermal therapy, chemotherapy, radiotherapy, immunotherapy, and theranostics. The remaining challenges and future opportunities in this field, in terms of precisely localized assembly, maximizing composite properties, and processing new techniques, are also presented. The introduction of multiple components into one crystalline MOF provides a promising approach to design all-in-one theranostics in clinical treatments.

Modified nanoscale metal organic framework-based nanoplatforms in photodynamic therapy and further applications

Photodynamic therapy (PDT) has emerged as a modality in cancer treatment because it is less invasive and highly selective compared with conventional chemotherapy and radiation therapy. Nanoscale metal organic frameworks (nMOFs) have exhibited great potential for use in constructing nanoplatforms for improved PDT because of their unique structural advantages such as large surface areas, high porosities, tunable compositions and various other modifications. The large majority of current nMOF-based systems employ specific modifying groups to overcome the deficiencies previously observed when using older nMOFs in PDT. In this review, we summarize modifications to these systems such as enhancing singlet oxygen generation by introducing photoactive agents, alleviating tumor hypoxia and engineering active targeting abilities. The applications of MOF-based nanoparticles in synergistic cancer therapies that include PDT, as well as in theranostics are also discussed. Finally, we discuss some of the challenges faced in this field and the future prospects for the use of nMOFs in PDT.

Oxygen Self-Sufficient Core-Shell Metal-Organic Framework-Based Smart Nanoplatform for Enhanced Synergistic Chemotherapy and Photodynamic Therapy

The abnormal angiogenesis and insufficient oxygen supply in solid tumors lead to intratumoral hypoxia, which severely limits the efficacy of traditional photodynamic therapy (PDT). Here, a multifunctional nanoplatform (ZDZP@PP) based on a zeolitic imidazolate framework-67 (ZIF-67) core as a hydrogen peroxide catalyst, a zeolitic imidazolate framework-8 (ZIF-8) shell with a pH-responsive property, and a polydopamine-poly(ethylene glycol) (PDA-PEG) layer for improving the biocompatibility is fabricated for not only relieving tumor hypoxia but also enhancing the efficacy of combination chemo-photodynamic therapy. The chemotherapy drug doxorubicin (DOX) and photosensitizer protoporphyrin IX (PpIX) are encapsulated in different layers independently; thus, a unique two-stage stepwise release becomes possible. Moreover, the nanoplatform can effectively decompose hydrogen peroxide to produce oxygen and thus relieve tumor hypoxia, which further facilitates the production of cytotoxic reactive oxygen species (ROS) by PpIX under laser irradiation. Both in vitro and in vivo experimental results confirm that the combination chemo-photodynamic therapy with the ZDZP@PP nanoplatform can provide more effective cancer treatment than chemotherapy or PDT alone. Consequently, the oxygen self-sufficient multifunctional nanoplatform holds promising potential to overcome hypoxia and treat solid tumors in the future.

Tracking Osteoarthritis Progress through Cationic Nanoprobe-Enhanced Photoacoustic Imaging of Cartilage

A major obstacle in osteoarthritis (OA) theranostics is the lack of a timely and accurate monitoring method. It is hypothesized that the loss of anionic glycosaminoglycans (GAGs) in articular cartilage reflects the progression of OA. Thus, this study investigated the feasibility of photoacoustic imaging (PAI) applied for monitoring the in vivo course of OA progression via GAG-targeted cationic nanoprobes. The nanoprobes were synthesized through electrostatic attraction between poly-l-Lysine and melanin (PLL-MNPs). Cartilage explants with different concentrations of GAGs incubated with PLL-MNPs to test the relationship between GAGs content and PA signal intensity. GAG activity was then evaluated in vivo in destabilization of the medial meniscus (DMM) surgically-induced mouse model. To track OA progression over time, mice were imaged consistently for 10 weeks after OA-inducing surgery. X-ray was used to verify the superiority of PAI in detecting OA. The correlation between PAI data and histologic results was also analyzed. In vitro study demonstrated the ability of PLL-MNPs in sensitively detecting different GAGs concentrations. In vivo PAI exhibited significantly lower signal intensity from OA knees compared to normal knees. More importantly, PA signal intensity showed serial reduction over the course of OA, while X-ray showed visible joint destruction until 6 weeks. A decrease in GAGs content was confirmed by histologic examinations; moreover, histologic findings were well correlated with PAI results. Therefore, using cationic nanoprobe-enhanced PAI to detect the changes in GAG contents provides sensitive and consistent visualization of OA development. This approach will further facilitate OA theranostics and clinical translation. STATEMENT OF SIGNIFICANCE: The study of in vivo monitoring osteoarthritis (OA) is of high significance to tracking the trajectory of OA development and therapeutic monitoring. Here, we developed a cartilage-targeted cationic nanoprobe, poly-l-Lysine-melanin nanoparticles (PLL-MNPs), enhancing photoacoustic imaging (PAI) to monitor the progression of OA. The in vitro study demonstrated the ability of PLL-MNPs to detect different concentrations of GAGs with high sensitivity. We found that the contents of GAGs in vivo steadily decreased from the development of OA initial-stage to the end-point of our investigation via PAI; it reflected the course of OA in living subjects with high sensitivity. These results allow for further development in various aspects of OA research. It has potential for clinical translation and has a great impact on personalized medicine.

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.

Interactions Between Tumor Biology and Targeted Nanoplatforms for Imaging Applications

Although considerable efforts have been conducted to diagnose, improve, and treat cancer in the past few decades, existing therapeutic options are insufficient, as mortality and morbidity rates remain high. Perhaps the best hope for substantial improvement lies in early detection. Recent advances in nanotechnology are expected to increase the current understanding of tumor biology, and will allow nanomaterials to be used for targeting and imaging both in vitro and in vivo experimental models. Owing to their intrinsic physicochemical characteristics, nanostructures (NSs) are valuable tools that have received much attention in nanoimaging. Consequently, rationally designed NSs have been successfully employed in cancer imaging for targeting cancer-specific or cancer-associated molecules and pathways. This review categorizes imaging and targeting approaches according to cancer type, and also highlights some new safe approaches involving membrane-coated nanoparticles, tumor cell-derived extracellular vesicles, circulating tumor cells, cell-free DNAs, and cancer stem cells in the hope of developing more precise targeting and multifunctional nanotechnology-based imaging probes in the future.