Dual ATP and pH responsive ZIF-90 nanosystem with favorable biocompatibility and facile post-modification improves therapeutic outcomes of triple negative breast cancer in vivo

Zeolitic imidazole frameworks (ZIFs) are becoming a notable nanosystem in biomedicine field, due to their unique properties of favorable biocompatibility, pH-responsive degradable structure and high drug loading. Compared with the increasing attention on ZIF-8 in cancer diagnosis and treatment, there is limited research about the bio-application of ZIF-90, especially its in vivo therapeutic efficacy and related toxicity. Here, we synthesize nano ZIF-90 through a fast self-assembling process, and the synthesized nano ZIF-90 is about 75 nm with a negative zeta potential, providing better mitochondria targetability, cell biocompatibility and in vivo survival rate comparing to nano ZIF-8. To further explore the applicability of ZIF-90 in cancer treatment, a facile post-modification is used to conjugate Y₁ receptor ligand [Asn⁶, Pro³⁴]-NPY (AP) on the surface of doxorubicin (DOX)-encapsulated nano ZIF-90. AP-ZIF-90 significantly reduces premature DOX release at physiological pH level, and triggers more effective and faster DOX release inside the tumor cells with dual responsive to high adenosine triphosphate (ATP) and low pH condition. Combining targeted delivery and dual responsive release of DOX significantly improves the therapeutic efficacy of AP-ZIF-90@DOX in MDA-MB-231 tumor bearing mouse, and results in 80% survival rate over 40 days of treatment. At the given dosage, nano ZIF-90 is with excellent biocompatibility in vivo, inducing minimal side effect on the liver and renal functions. Therefore, nano ZIF-90 combines with Y₁ receptor ligand with favorable biocompatibility and dual responsiveness can be used as a promising nanosystem for targeted triple negative breast cancer treatment in vivo.

New insights on the supramolecular structure of highly porous core–shell drug nanocarriers using solid-state NMR spectroscopy

Nano-sized metal–organic frameworks (nanoMOFs), with engineered surfaces to enhance the targeting of the drug delivery, have proven efficient as drug nanocarriers.

Drug nanoclusters formed in confined nano-cages of CD-MOF: dramatic enhancement of solubility and bioavailability of azilsartan

Tremendous efforts have been devoted to the enhancement of drug solubility using nanotechnologies, but few of them are capable to produce drug particles with sizes less than a few nanometers. This challenge has been addressed here by using biocompatible versatile γ-cyclodextrin (γ-CD) metal-organic framework (CD-MOF) large molecular cages in which azilsartan (AZL) was successfully confined producing clusters in the nanometer range. This strategy allowed to improve the bioavailability of AZL in Sprague-Dawley rats by 9.7-fold after loading into CD-MOF. The apparent solubility of AZL/CD-MOF was enhanced by 340-fold when compared to the pure drug. Based on molecular modeling, a dual molecular mechanism of nanoclusterization and complexation of AZL inside the CD-MOF cages was proposed, which was confirmed by small angle X-ray scattering (SAXS) and synchrotron radiation-Fourier transform infrared spectroscopy (SR-FTIR) techniques. In a typical cage-like unit of CD-MOF, three molecules of AZL were included by the γ-CD pairs, whilst other three AZL molecules formed a nanocluster inside the 1.7 nm sized cavity surrounded by six γ-CDs. This research demonstrates a dual molecular mechanism of complexation and nanoclusterization in CD-MOF leading to significant improvement in the bioavailability of insoluble drugs.

Bio-related applications of porous organic frameworks (POFs)

Porous organic frameworks (POFs) are promising candidates for bio-related applications. This review highlights the recent progress in POF-based bioapplications, including drug delivery, bioimaging, biosensing, therapeutics, and artificial shells. These encouraging performances suggest that POFs used for bioapplications deserve more attention in the future.

Recent Trends in Covalent and Metal Organic Frameworks for Biomedical Applications

Materials science has seen a great deal of advancement and development. The discovery of new types of materials sparked the study of their properties followed by applications ranging from separation, catalysis, optoelectronics, sensing, drug delivery and biomedicine, and many other uses in different fields of science. Metal organic frameworks (MOFs) and covalent organic frameworks (COFs) are a relatively new type of materials with high surface areas and permanent porosity that show great promise for such applications. The current study aims at presenting the recent work achieved in COFs and MOFs for biomedical applications, and to examine some challenges and future directions which the field may take. The paper herein surveys their synthesis, and their use as Drug Delivery Systems (DDS), in non-drug delivery therapeutics and for biosensing and diagnostics.

GraftFast Surface Engineering to Improve MOF Nanoparticles Furtiveness

Controlling the outer surface of nanometric metal-organic frameworks (nanoMOFs) and further understanding the in vivo effect of the coated material are crucial for the convenient biomedical applications of MOFs. However, in most studies, the surface modification protocol is often associated with significant toxicity and/or lack of selectivity. As an alternative, how the highly selective and general grafting GraftFast method leads, through a green and simple process, to the successful attachment of multifunctional biopolymers (polyethylene glycol (PEG) and hyaluronic acid) on the external surface of nanoMOFs is reported. In particular, effectively PEGylated iron trimesate MIL-100(Fe) nanoparticles (NPs) exhibit suitable grafting stability and superior chemical and colloidal stability in different biofluids, while conserving full porosity and allowing the adsorption of bioactive molecules (cosmetic and antitumor agents). Furthermore, the nature of the MOF-PEG interaction is deeply investigated using high-resolution soft X-ray spectroscopy. Finally, a cell penetration study using the radio-labeled antitumor agent gemcitabine monophosphate (³ H-GMP)-loaded MIL-100(Fe)@PEG NPs shows reduced macrophage phagocytosis, confirming a significant in vitro PEG furtiveness.

Nanoscale Metal-Organic Frameworks for Therapeutic, Imaging, and Sensing Applications

Nanotechnology has played an important role in drug delivery and biomedical imaging over the past two decades. In particular, nanoscale metal-organic frameworks (nMOFs) are emerging as an important class of biomedically relevant nanomaterials due to their high porosity, multifunctionality, and biocompatibility. The high porosity of nMOFs allows for the encapsulation of exceptionally high payloads of therapeutic and/or imaging cargoes while the building blocks-both ligands and the secondary building units (SBUs)-can be utilized to load drugs and/or imaging agents via covalent attachment. The ligands and SBUs of nMOFs can also be functionalized for surface passivation or active targeting at overexpressed biomarkers. The metal ions or metal clusters on nMOFs also render them viable candidates as contrast agents for magnetic resonance imaging, computed tomography, or other imaging modalities. This review article summarizes recent progress on nMOF designs and their exploration in biomedical areas. First, the therapeutic applications of nMOFs, based on four distinct drug loading strategies, are discussed, followed by a summary of nMOF designs for imaging and biosensing. The review is concluded by exploring the fundamental challenges facing nMOF-based therapeutic, imaging, and biosensing agents. This review hopefully can stimulate interdisciplinary research at the intersection of MOFs and biomedicine.

Nanoparticles of Metal-Organic Frameworks: On the Road to In Vivo Efficacy in Biomedicine

In the past few years, numerous studies have demonstrated the great potential of nano particles of metal-organic frameworks (nanoMOFs) at the preclinical level for biomedical applications. Many of them were reported very recently based on their bioactive composition, anticancer application, or from a general drug delivery/theranostic perspective. In this review, the authors aim at providing a global view of the studies that evaluated MOFs' biomedical applications at the preclinical stage, when in vivo tests are described either for pharmacological applications or for toxicity evaluation. The authors first describe the current surface engineering approaches that are crucial to understand the in vivo behavior of the nanoMOFs. Finally, after a detailed and comprehensive analysis of the in vivo studies reported with MOFs so far, and considering the general evolution of the drug delivery science, the authors suggest new directions for future research in the use of nanoMOFs for biomedical applications.

Biocompatible porous metal-organic framework nanoparticles based on Fe or Zr for gentamicin vectorization

Due to their high porosity and versatile composition and structure, nanoscaled Metal-Organic Frameworks (nanoMOFs) have been recently proposed as novel drug delivery systems, and have been demonstrated to have important capacities and potential for controlled release of different active ingredients. Gentamicin (GM; a broad spectrum aminoglycoside antibiotic indicated in bacterial septicemia therapy) has great therapeutic interest, but the associated bioavailability and toxicity drawbacks accompanying high doses and repeated administration of this free drug make its encapsulation inside new nanocarriers necessary. GM encapsulation within two different porous biofriendly Fe and Zr-carboxylates nanoMOFs was performed by a simple impregnation method, with full characterization of the resulting GM-containing solid using a large panel of techniques (X ray powder diffraction-XRPD, Fourier transform infrared spectroscopy-FTIR, thermogravimetric analysis-TGA, N₂ sorption, scanning electron microscopy-SEM, dynamic light scattering-DLS, ζ-potential, fluorescence spectroscopy and molecular simulations). High reproducible encapsulation rates, reaching 600 µg of GM per·mg of formulation, were obtained using the biocompatible mesoporous iron(III) trimesate nanoparticles (NPs) MIL-100(Fe) (MIL: Materials from Institut Lavoisier). In vitro GM delivery studies were also carried out using different oral and intravenous simulated physiological conditions, with complete antibiotic release within 8 h when using protein free media, but lower release rates in the presence of proteins. Furthermore, in vitro toxicity of GM-containing MIL-100(Fe) NPs was investigated on two different cell lines: a monocyte from leukemia (THP-1) and adherent fibroblastoid cells (NIH/3T3). These nanoMOFs had a low cytotoxic profile with IC₅₀ values up to 1 mg·mL^-1, ensuring adequate cell proliferation after 24 h. Finally, antibacterial activity studies were carried out on two Gram-positive bacteria and one Gram-negative bacterium: S. aureus, S. epidermidis and P. aeruginosa, respectively. GM-loaded MIL-100(Fe) NPs exhibited the same activity as free GM, confirming that the antibiotic activity of the released GM was conserved.

Flow field-flow fractionation and multi-angle light scattering as a powerful tool for the characterization and stability evaluation of drug-loaded metal-organic framework nanoparticles

Asymmetric flow field-flow fractionation (AF4) coupled with UV-Vis spectroscopy, multi-angle light scattering (MALS) and refractive index (RI) detection has been applied for the characterization of MIL-100(Fe) nanoMOFs (metal-organic frameworks) loaded with nucleoside reverse transcriptase inhibitor (NRTI) drugs for the first time. Empty nanoMOFs and nanoMOFs loaded with azidothymidine derivatives with three different degrees of phosphorylation were examined: azidothymidine (AZT, native drug), azidothymidine monophosphate (AZT-MP), and azidothymidine triphosphate (AZT-TP). The particle size distribution and the stability of the nanoparticles when interacting with drugs have been determined in a time frame of 24 h. Main achievements include detection of aggregate formation in an early stage and monitoring nanoMOF morphological changes as indicators of their interaction with guest molecules. AF4-MALS proved to be a useful methodology to analyze nanoparticles engineered for drug delivery applications and gave fundamental data on their size distribution and stability. Graphical abstract ᅟ.

Iron-Based Metal-Organic Frameworks as a Theranostic Carrier for Local Tuberculosis Therapy

PURPOSE

The purpose of the study was initial evaluation of applicability of metal organic framework (MOF) Fe-MIL-101-NH2 as a theranostic carrier of antituberculous drug in terms of its functionality, i.e. drug loading, drug dissolution, magnetic resonance imaging (MRI) contrast and cytotoxic safety.

METHODS

Fe-MIL-101-NH2 was characterized using X-ray powder diffraction, FTIR spectrometry and scanning electron microscopy. The particle size analysis was determined using laser diffraction. Magnetic resonance relaxometry and MRI were carried out on phantoms of the MOF system suspended in polymer solution. Drug dissolution studies were conducted using Franz cells. For MOF cytotoxicity, commercially available fibroblasts L929 were cultured in Eagle's Minimum Essential Medium supplemented with 10% fetal bovine serum.

RESULTS

MOF particles were loaded with 12% of isoniazid. The particle size (3.37-6.45 μm) depended on the micronization method used. The proposed drug delivery system can also serve as the MRI contrast agent. The drug dissolution showed extended release of isoniazid. MOF particles accumulated in the L929 fibroblast cytoplasmic area, suggesting MOF release the drug inside the cells. The cytotoxicity confirmed safety of MOF system.

CONCLUSIONS

The application of MOF for extended release inhalable system proposes the novel strategy for delivery of standard antimycobacterial agents combined with monitoring of their distribution within the lung tissue.

Nanoscaled Metal-Organic Frameworks for Biosensing, Imaging, and Cancer Therapy

Owing to the progressive development of metal-organic frameworks (MOFs) synthetic processes and their unique characters associated with the excellent performance-selectable composition, tunable pore scale, large surface area, and good thermal stability, MOFs have captured the interest and the imagination of an increasing number of scientists working in different fields. In the area of biomedical applications, MOFs are especially involved in sensing, molecular imaging, and drug delivery, with strong contributions to the whole nanomedicine area. Recently, these materials have been scaled down to nanometer sizes with the advancement of chemical synthesis gradually reaching an adjustable level. This review mainly discusses and summarizes the general synthesis, properties, and biomedical applications of nanoscaled MOFs and their composites in biosensing, imaging, and cancer therapy within the latest three years. The remaining challenges and future opportunities in this field, in terms of processing techniques, maximizing composite properties, and prospects for clinical applications, are also indicated.

Nanoscale metal–organic frameworks for drug delivery: a conventional platform with new promise

This review highlights recent advances made using nanoscale metal–organic frameworks (NMOFs) for designing cargo-delivery systems.

Synthesis, functionalization, and applications of metal–organic frameworks in biomedicine

Metal–organic frameworks (MOFs), also known as coordination polymers, have attracted extensive research interest in the past few decades due to their unique physical structures and potentially vast applications.

(Fe)MIL-100-Met@alginate: a hybrid polymer–MOF for enhancement of metformin's bioavailability and pH-controlled release

Metformin hydrochloride (Met) was combined with iron(iii) chloride and trimesic acid (1,3,5-benzene tricarboxylic acid, BTC) as an organic linker in a short and simple method, providing a MOF in which the drug is a part of the constituent.

High efficiency and long-term intracellular activity of an enzymatic nanofactory based on metal-organic frameworks

Enhancing or restoring enzymatic function in cells is highly desirable in applications ranging from ex vivo cellular manipulations to enzyme replacement therapies in humans. However, because enzymes degrade in biological milieus, achieving long-term enzymatic activities can be challenging. Herein we report on the in cellulo properties of nanofactories that consist of antioxidative enzymes encapsulated in metal-organic frameworks (MOFs). We demonstrate that, while free enzymes display weak activities for only a short duration, these efficient nanofactories protect human cells from toxic reactive oxygen species for up to a week. Remarkably, these results are obtained in spite of the nanofactories being localized in lysosomes, acidic organelles that contain a variety of proteases. The long-term persistence of the nanofactories is attributed to the chemical stability of MOF in low pH environment and to the protease resistance provided by the protective cage formed by the MOF around the encapsulated enzymes.

New insights into the degradation mechanism of metal-organic frameworks drug carriers

A versatile method based on Raman microscopy was developed to follow the degradation of iron carboxylate Metal Organic Framework (MOF) nano- or micro-particles in simulated body fluid (phosphate buffer). The analysis of both the morphology and chemical composition of individual particles, including observation at different regions on the same particle, evidenced the formation of a sharp erosion front during particle degradation. Interestingly, this front separated an intact non eroded crystalline core from an amorphous shell made of an inorganic network. According to Mössbauer spectrometry investigations, the shell consists essentially of iron phosphates. Noteworthy, neither drug loading nor surface modification affected the integrity of the tridimensional MOF network. These findings could be of interest in the further development of next generations of MOF drug carriers.

Far infrared micro-spectroscopy: an innovative method to detect individual metal-organic framework particles

The purpose of this study is to extend the spectral range of a differential method of infrared micro-spectroscopy in order to allow the accurate detection of nanoparticles of interest for biomedical applications. Among these, metal-organic framework (MOF) nanoparticles have attracted increasing interest due to their capacity to incorporate high drug payloads, biodegradability, and possibility of tailoring their surfaces by grafting specific ligands. However, MOF particle detection in biological media without grafting or incorporating fluorescent molecules is challenging. We took advantage here of the presence of the specific absorption bands of nanoscale MOFs in far infrared in order to individually discriminate them. Here we show that single MOF nanoparticles can be imaged with a spatial resolution of a few tens of nanometers.

Integration of Biomolecules with Metal-Organic Frameworks

Owing to the progressive development of metal-organic-frameworks (MOFs) synthetic processes and considerable potential applications in last decade, integrating biomolecules into MOFs has recently gain considerable attention. Biomolecules, including lipids, oligopeptides, nucleic acids, and proteins have been readily incorporated into MOF systems via versatile formulation methods. The formed biomolecule-MOF hybrid structures have shown promising prospects in various fields, such as antitumor treatment, gene delivery, biomolecular sensing, and nanomotor device. By optimizing biomolecule integration methods while overcoming existing challenges, biomolecule-integrated MOF platforms are very promising to generate more practical applications.

Chemical and biological assessment of metal organic frameworks (MOFs) in pulmonary cells and in an acute in vivo model: relevance to pulmonary arterial hypertension therapy

Pulmonary arterial hypertension (PAH) is a progressive and debilitating condition. Despite promoting vasodilation, current drugs have a therapeutic window within which they are limited by systemic side effects. Nanomedicine uses nanoparticles to improve drug delivery and/or reduce side effects. We hypothesize that this approach could be used to deliver PAH drugs avoiding the systemic circulation. Here we report the use of iron metal organic framework (MOF) MIL-89 and PEGylated MIL-89 (MIL-89 PEG) as suitable carriers for PAH drugs. We assessed their effects on viability and inflammatory responses in a wide range of lung cells including endothelial cells grown from blood of donors with/without PAH. Both MOFs conformed to the predicted structures with MIL-89 PEG being more stable at room temperature. At concentrations up to 10 or 30 µg/mL, toxicity was only seen in pulmonary artery smooth muscle cells where both MOFs reduced cell viability and CXCL8 release. In endothelial cells from both control donors and PAH patients, both preparations inhibited the release of CXCL8 and endothelin-1 and in macrophages inhibited inducible nitric oxide synthase activity. Finally, MIL-89 was well-tolerated and accumulated in the rat lungs when given in vivo. Thus, the prototypes MIL-89 and MIL-89 PEG with core capacity suitable to accommodate PAH drugs are relatively non-toxic and may have the added advantage of being anti-inflammatory and reducing the release of endothelin-1. These data are consistent with the idea that these materials may not only be useful as drug carriers in PAH but also offer some therapeutic benefit in their own right.

Composite CD-MOF nanocrystals-containing microspheres for sustained drug delivery

Metal-organic frameworks (MOFs), which are typically embedded in polymer matrices as composites, are emerging as a new class of carriers for sustained drug delivery. Most of the MOFs and the polymers used so far in these composites, however, are not pharmaceutically acceptable. In the investigation reported herein, composites of γ-cyclodextrin (γ-CD)-based MOFs (CD-MOFs) and polyacrylic acid (PAA) were prepared by a solid in oil-in-oil (s/o/o) emulsifying solvent evaporation method. A modified hydrothermal protocol has been established which produces efficiently at 50 °C in 6 h micron (5-10 μm) and nanometer (500-700 nm) diameter CD-MOF particles of uniform size with smooth surfaces and powder X-ray diffraction patterns that are identical with those reported in the literature. Ibuprofen (IBU) and Lansoprazole (LPZ), both insoluble in water and lacking in stability, were entrapped with high drug loading in nanometer-sized CD-MOFs by co-crystallisation (that is more effective than impregnation) without causing MOF crystal degradation during the loading process. On account of the good dispersion of drug-loaded CD-MOF nanocrystals inside polyacrylic acid (PAA) matrices and the homogeneous distribution of the drug molecules within these crystals, the composite microspheres exhibit not only spherical shapes and sustained drug release over a prolonged period of time, but they also demonstrate reduced cell toxicity. The cumulative release rate for IBU (and LPZ) follows the trend: IBU-γ-CD complex microspheres (ca. 80% in 2 h) > IBU microspheres > IBU-CD-MOF/PAA composite microspheres (ca. 50% in 24 h). Importantly, no burst release of IBU (and LPZ) was observed from the CD-MOF/PAA composite microspheres, suggesting an even distribution of the drug as well as strong drug carrier interactions inside the CD-MOF. In summary, these composite microspheres, composed of CD-MOF nanocrystals embedded in a biocompatible polymer (PAA) matrix, constitute an efficient and pharmaceutically acceptable MOF-based carrier for sustained drug release.

Metal-Organic Framework (MOF)-Based Drug/Cargo Delivery and Cancer Therapy

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 recent years. 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, make them promising candidates as drug delivery hosts. Furthermore, scientists have made remarkable achievements in the field of nanomedical applications of MOFs, owing to their facile synthesis on the nanoscale and alternative functionalization via inclusion and surface chemistry. A brief introduction to the applications of MOFs in controlled drug/cargo delivery and cancer therapy that have been reported in recent years is provided here.

Chitosan-coated mesoporous MIL-100(Fe) nanoparticles as improved bio-compatible oral nanocarriers

Nanometric biocompatible Metal-Organic Frameworks (nanoMOFs) are promising candidates for drug delivery. Up to now, most studies have targeted the intravenous route, related to pain and severe complications; whereas nanoMOFs for oral administration, a commonly used non-invasive and simpler route, remains however unexplored. We propose here the biofriendly preparation of a suitable oral nanocarrier based on the benchmarked biocompatible mesoporous iron(III) trimesate nanoparticles coated with the bioadhesive polysaccharide chitosan (CS). This method does not hamper the textural/structural properties and the sorption/release abilities of the nanoMOFs upon surface engineering. The interaction between the CS and the nanoparticles has been characterized through a combination of high resolution soft X-ray absorption and computing simulation, while the positive impact of the coating on the colloidal and chemical stability under oral simulated conditions is here demonstrated. Finally, the intestinal barrier bypass capability and biocompatibility of CS-coated nanoMOF have been assessed in vitro, leading to an increased intestinal permeability with respect to the non-coated material, maintaining an optimal biocompatibility. In conclusion, the preservation of the interesting physicochemical features of the CS-coated nanoMOF and their adapted colloidal stability and progressive biodegradation, together with their improved intestinal barrier bypass, make these nanoparticles a promising oral nanocarrier.

A non-covalent "click chemistry" strategy to efficiently coat highly porous MOF nanoparticles with a stable polymeric shell

BACKGROUND

Metal-organic framework nanoparticles (nanoMOFs) are biodegradable highly porous materials with a remarkable ability to load therapeutic agents with a wide range of physico-chemical properties. Engineering the nanoMOFs surface may provide nanoparticles with higher stability, controlled release, and targeting abilities. Designing postsynthetic, non-covalent self-assembling shells for nanoMOFs is especially appealing due to their simplicity, versatility, absence of toxic byproducts and minimum impact on the original host-guest ability.

METHODS

In this study, several β-cyclodextrin-based monomers and polymers appended with mannose or rhodamine were randomly phosphorylated, and tested as self-assembling coating building blocks for iron trimesate MIL-100(Fe) nanoMOFs. The shell formation and stability were studied by isothermal titration calorimetry (ITC), spectrofluorometry and confocal imaging. The effect of the coating on tritium-labeled AZT-PT drug release was estimated by scintillation counting.

RESULTS

Shell formation was conveniently achieved by soaking the nanoparticles in self-assembling agent aqueous solutions. The grafted phosphate moieties enabled a firm anchorage of the coating to the nanoMOFs. Coating stability was directly related to the density of grafted phosphate groups, and did not alter nanoMOFs morphology or drug release kinetics.

CONCLUSION

An easy, fast and reproducible non-covalent functionalization of MIL-100(Fe) nanoMOFs surface based on the interaction between phosphate groups appended to β-cyclodextrin derivatives and iron(III) atoms is presented.

GENERAL SIGNIFICANCE

This study proved that discrete and polymeric phosphate β-cyclodextrin derivatives can conform non-covalent shells on iron(III)-based nanoMOFs. The flexibility of the β-cyclodextrin to be decorated with different motifs open the way towards nanoMOFs modifications for drug delivery, catalysis, separation, imaging and sensing. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editors: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader.

Engineering Phototheranostic Nanoscale Metal-Organic Frameworks for Multimodal Imaging-Guided Cancer Therapy

Many photoresponsive dyes have been utilized as imaging and photodynamic/photothermal therapy agents. Indocyanine green (ICG) is the only near-infrared region (NIR) organic dye for clinical applications approved by the United States Food and Drug Administration; however, the clinical application of ICG is limited by its poor aqueous solubility, low cancer specificity, and low sensitivity in cancer theranostics. To overcome these issues, a multifunctional nanoplatform based on hyaluronic acid (HA) and ICG-engineered metal-organic framework MIL-100(Fe) nanoparticles (MOF@HA@ICG NPs) was successfully developed for imaging-guided, anticancer photothermal therapy (PTT). The synthesized NPs showed a high loading content of ICG (40%), strong NIR absorbance, and photostability. The in vitro and in vivo imaging showed that the MOF@HA@ICG NPs exhibited greater cellular uptake in CD44-positive MCF-7 cells and enhanced tumor accumulation in xenograft tumors due to their targeting capability, compared to MOF@ICG NPs (non-HA-targeted) and free ICG. The in vitro photothermal toxicity and in vivo PTT treatments demonstrated that MOF@HA@ICG NPs could effectively inhibit the growth of MCF-7 cells/xenograft tumors. These results suggest that MOF@HA@ICG NPs could be served as a new promising theranostic nanoplatform for improved anticancer PTT through cancer-specific and image-guided drug delivery.

Validating Metal-Organic Framework Nanoparticles for Their Nanosafety in Diverse Biomedical Applications

Metal-organic frameworks (MOFs) are promising platforms for the synthesis of nanoparticles for diverse medical applications. Their fundamental design principles allow for significant control of the framework architecture and pore chemistry, enabling directed functionalization for nanomedical applications. However, before applying novel nanomaterials to patients, it is imperative to understand their potential health risks. In this study, the nanosafety of different MOF nanoparticles is analyzed comprehensively for diverse medical applications. The authors first evaluate the effects of MOFs on human endothelial and mouse lung cells, which constitute a first line of defense upon systemic blood-mediated and local lung-specific applications of nanoparticles. Second, we validated these MOFs for multifunctional surface coatings of dental implants using human gingiva fibroblasts. Moreover, biocompatibility of MOFs is assessed for surface coating of nerve guidance tubes using human Schwann cells and rat dorsal root ganglion cultures. The main finding of this study is that the nanosafety and principal suitability of our MOF nanoparticles as novel agents for drug delivery and implant coatings strongly varies with the effector cell type. We conclude that it is therefore necessary to carefully evaluate the nanosafety of MOF nanomaterials with respect to their particular medical application and their interacting primary cell types, respectively.

BODIPY-containing nanoscale metal–organic frameworks as contrast agents for computed tomography

A new computed tomography (CT) imaging agent is developed based on the BODIPY-containing nanoscale metal–organic frameworks (NMOFs). The bio-safety and CT imaging of such NMOFs have been well investigated both in vitro and in vivo.

Ultrabright organic fluorescent microparticles for in vivo tracing applications

We report the in vivo distribution, toxicity and metabolism of micro-sized fluorescent organic particles and their applications in cerebral blood flow tracing. The fluorescent microparticles exhibit bright fluorescence, good photo-stability and low toxicity; therefore, they are ideal for long-term non-invasive in vivo tracing. In contrast to conventional fluorescent labeling agents, which stain the entire blood vessel, the tracer microparticles can be easily tracked individually and provide vital information about blood flow behavior. Furthermore, we observed stimulated emission from these microparticles in living animals. These microparticles can provide unprecedented contrast for simultaneous observation of the distribution of blood vessels and the dynamics of microcirculation. Pathological examination revealed that the injected microparticles eventually collected in the spleen and liver. We found no observable toxicity of the microparticles to cells or mouse organs. We demonstrate that these fluorescent microparticles are suitable for applications in the field of non-intrusive blood flow tracing and could play a complementary role to traditional imaging agents.

Metal-Organic Frameworks for CO2 Chemical Transformations

Carbon dioxide (CO₂ ), as the primary greenhouse gas in the atmosphere, triggers a series of environmental and energy related problems in the world. Therefore, there is an urgent need to develop multiple methods to capture and convert CO₂ into useful chemical products, which can significantly improve the environment and promote sustainable development. Over the past several decades, metal-organic frameworks (MOFs) have shown outstanding heterogeneous catalytic activity due in part to their high internal surface area and chemical functionalities. These properties and the ability to synthesize MOF platforms allow experiments to test structure-function relationships for transforming CO₂ into useful chemicals. Herein, recent developments are highlighted for MOFs participating as catalysts for the chemical fixation and photochemical reduction of CO₂ . Finally, opportunities and challenges facing MOF catalysts are discussed in this ongoing research area.

Accumulation of biosynthesized gold nanoparticles and its impact on various organs of Sprague Dawley rats: a systematic study

Background: Many in vivo studies have revealed that the cytotoxic potential of gold nanoparticles results in controversial conclusions. The aim of this study is to establish a systematic method for determining the biological effects of gold nanoparticles in rats. Methods: In the present investigation AuNPs were prepared using Helianthus tuberosus extract as a reducing agent. The synthesized AuNPs were characterized using various techniques, such as Bio-TEM, SEM-EDS, X-ray diffraction and FT-IR. Cytotoxicity of the synthesized AuNPs was assessed using the rat as an animal model. Subchronic oral administration of AuNPs (5 and 10 mg kg-1) and its effect on major organs (liver, kidney, lungs, and spleen) and its accumulation were analyzed using haematoxylin & eosin staining and ICP-MS respectively. The extent of apoptosis in the liver cells was determined using western blotting. Results: The results of the current study revealed that the synthesized AuNPs at a mild concentration of 5 mg kg-1 have been found to cause a hypoglycemic state and an increase in the HDL cholesterol level in normal rats. Nevertheless, histopathological results revealed that AuNPs could cause inflammation in the lungs at increasing concentrations. Conclusion: The biologically synthesized AuNPs were evaluated in this study showed a hypoglycemic effect at a concentration of 5 mg kg-1 AuNPs. A systemic study on the accumulation of AuNPs revealed that the lung is the major target organ and further suggests that enduring administration could lead to organ damage as majorly observed in lung tissue. This study highlights the necessity of complete in vivo toxicity analysis, prior to introducing nanoparticles in any application field. Further, this study warrants the application of the synthesized AuNPs in drug delivery related to lung disorders.

Water-Stable Metal-Organic Framework/Polymer Composites Compatible with Human Hepatocytes

Metal-organic frameworks (MOFs) have demonstrated promise in biomedical applications as vehicles for drug delivery, as well as for the ability of copper-based MOFs to generate nitric oxide (NO) from endogenous S-nitrosothiols (RSNOs). Because NO is a participant in biological processes where it exhibits anti-inflammatory, antibacterial, and antiplatelet activation properties, it has received significant attention for therapeutic purposes. Previous work has shown that the water-stable MOF H3[(Cu4Cl)3-(BTTri)8] (H3BTTri = 1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene), or CuBTTri, produces NO from RSNOs and can be included within a polymeric matrix to form NO-generating materials. While such materials demonstrate potential, the possibility of MOF degradation leading to copper-related toxicity is a concern that must be addressed prior to adapting these materials for biomedical applications. Herein, we present the first cytotoxicity evaluation of an NO-generating CuBTTri/polymer composite material using 3T3-J2 murine embryonic fibroblasts and primary human hepatocytes (PHHs). CuBTTri/polymer films were prepared from plasticized poly(vinyl chloride) (PVC) and characterized via PXRD, ATR-FTIR, and SEM-EDX. Additionally, the ability of the CuBTTri/polymer films to enhance NO generation from S-nitroso-N-acetylpenicillamine (SNAP) was evaluated. Enhanced NO generation in the presence of the CuBTTri/polymer films was observed, with an average NO flux (0.90 ± 0.13 nmol cm(-2) min(-1)) within the range associated with antithrombogenic surfaces. The CuBTTri/polymer films were analyzed for stability in phosphate buffered saline (PBS) and cell culture media under physiological conditions for a 4 week duration. Cumulative copper release in both cell media (0.84 ± 0.21%) and PBS (0.18 ± 0.01%) accounted for less than 1% of theoretical copper present in the films. In vitro cell studies performed with 3T3-J2 fibroblasts and PHHs did not indicate significant toxicity, providing further support for the potential implementation of CuBTTri-based materials in biomedical applications.

Efficient "green" encapsulation of a highly hydrophilic anticancer drug in metal-organic framework nanoparticles

Metal-organic frameworks (MOFs) are coordination polymers of interest for biomedical applications. Of particular importance, nanoparticles made of iron(III) trimesate (MIL-100, MIL standing for Material Institut Lavoisier) (nanoMOFs) can be conveniently synthesised under mild and green conditions. They were shown to be biodegradable, biocompatible and efficient to encapsulate a variety of active molecules. We have addressed here the challenges to encapsulate a highly hydrophilic anticancer prodrug, phosphated gemcitabin (Gem-MP) known for its instability and inability to bypass cell membranes. MIL-100 nanoMOFs acted as efficient "nanosponges", soaking Gem-MP from its aqueous solution with almost perfect efficiency (>98%). Maximal loadings reached ∼30 wt% reflecting the strong interaction between the drug and the iron trimesate matrices. Neither degradation nor loss of crystalline structure was observed after the loading process. Storage of the loaded nanoMOFs in water did not result in drug release over three days. However, Gem-MP was released in media containing phosphates, as a consequence to particle degradation. Drug-loaded nanoMOFs were effective against pancreatic PANC-1 cells, in contrast to free drug and empty nanoMOFs. However, an efflux phenomenon could contribute to reduce the efficacy of the nanocarriers. Size optimization and surface modification of the nanoMOFs are expected to further improve these findings.

Fe-MIL-101 exhibits selective cytotoxicity and inhibition of angiogenesis in ovarian cancer cells via downregulation of MMP

Though metal-organic frameworks (MOFs) have inspired potential applications in biomedicine, cytotoxicity studies of MOFs have been relatively rare. Here we demonstrate for the first time that an easily available MOF, Fe-MIL-101, possesses intrinsic activity against human SKOV3 ovarian cancer cells and suppress the proliferation of SKOV3 cells (IC50 = 23.6 μg mL(-1)) and normal mouse embryonic fibroblasts (BABL-3T3, IC50 = 78.3 μg mL(-1)) cells. It was more effective against SKOV3 cells than typical anticancer drugs such as artesunate (ART, IC50 = 96.9 μg mL(-1)) and oxaliplatin (OXA, IC50 = 64.4 μg mL(-1)), but had less effect on normal BABL-3T3 cells compared with ART (IC50 = 36.6 μg mL(-1)) and OXA (IC50 = 13.8 μg mL(-1)). Fe-MIL-101 induced apoptosis of human umbilical vein endothelial cells (HUVECs) via G0/G1 cell cycle arrest and decreased the mitochondrial membrane potential in HUVECs and induced apoptosis. Furthermore, Fe-MIL-101 exhibited stronger antiangiogenic effects in HUVEC cells than antiangiogenic inhibitor (SU5416) via downregulation the expression of MMP-2/9. Our results reveal a new role of Fe-MIL-101 as a novel, non-toxic anti-angiogenic agent that restricted ovarian tumour growth. These findings could open a new avenue of using MOFs as potential therapeutics in angiogenesis-dependent diseases, including ovarian cancer.

Ultrapure laser-synthesized Si-based nanomaterials for biomedical applications: in vivo assessment of safety and biodistribution

Si/SiOx nanoparticles (NPs) produced by laser ablation in deionized water or aqueous biocompatible solutions present a novel extremely promising object for biomedical applications, but the interaction of these NPs with biological systems has not yet been systematically examined. Here, we present the first comprehensive study of biodistribution, biodegradability and toxicity of laser-synthesized Si-SiOx nanoparticles using a small animal model. Despite a relatively high dose of Si-NPs (20 mg/kg) administered intravenously in mice, all controlled parameters (serum, enzymatic, histological etc.) were found to be within safe limits 3 h, 24 h, 48 h and 7 days after the administration. We also determined that the nanoparticles are rapidly sequestered by the liver and spleen, then further biodegraded and directly eliminated in urine without any toxicity effects. Finally, we found that intracellular accumulation of Si-NPs does not induce any oxidative stress damage. Our results evidence a huge potential in using these safe and biodegradable NPs in biomedical applications, in particular as vectors, contrast agents and sensitizers in cancer therapy and diagnostics (theranostics).

Metal-organic frameworks: mechanisms of antibacterial action and potential applications

The growing resistance of pathogens to conventional antibiotics has become a public health problem and raises the need to seek new effective solutions. Metal-organic frameworks (MOFs) are porous, hybrid materials comprising metal ions linked by organic binding ligands. The possibility of using a variety of chemical building components in MOFs enables the formation of structures with desired properties. They can act as a reservoir of metal ions, providing their gradual release and resulting in a sustained antibacterial action analogous to that proposed for metal/metal oxide nanoparticles (NPs) but different to that of antibiotics. These features make MOFs promising candidates for pharmaceutical and biomedical applications, as illustrated by examples discussed in this review.