Novel trypsin-FITC@MOF bioreactor efficiently catalyzes protein digestion

Biodiesel Production Using Palm Oil with a MOF-Lipase B Biocatalyst from Candida Antarctica: A Kinetic and Thermodynamic Study

This research presents the results of the immobilization of Candida Antarctica Lipase B (CALB) on MOF-199 and ZIF-8 and its use in the production of biodiesel through the transesterification reaction using African Palm Oil (APO). The results show that the highest adsorption capacity, the 26.9 mg·g^-1 Lipase, was achieved using ZIF-8 at 45 °C and an initial protein concentration of 1.20 mg·mL^-1. The results obtained for the adsorption equilibrium studies allow us to infer that CALB was physically adsorbed on ZIF-8 while chemically adsorbed with MOF-199. It was determined that the adsorption between Lipase and the MOFs under study better fit the Sips isotherm model. The results of the kinetic studies show that adsorption kinetics follow the Elovich model for the two synthesized biocatalysts. This research shows that under the experimental conditions in which the studies were carried out, the adsorption processes are a function of the intraparticle and film diffusion models. According to the results, the prepared biocatalysts showed a high efficiency in the transesterification reaction to produce biodiesel, with methanol as a co-solvent medium. In this work, the catalytic studies for the imidazolate, ZIF-8, presented more catalytic activity when used with CALB. This system presented 95% biodiesel conversion, while the biocatalyst formed by MOF-199 and CALB generated a catalytic conversion percentage of 90%. Although both percentages are high, it should be noted that CALB-MOF-199 presented better reusability, which is due to chemical interactions.

Advances in surface-modified nanometal-organic frameworks for drug delivery

Nanometal-organic frameworks (NMOFs) are porous network structures composed of metal ions or metal clusters through self-assembly. NMOFs have been considered as a promising nano-drug delivery system due to their unique properties such as pore and flexible structures, large specific surface areas, surface modifiability, non-toxic and degradable properties. However, NMOFs face a series complex environment during in vivo delivery. Therefore, surface functionalization of NMOFs is vital to ensure that the structure of NMOFs remain stable during delivery, and can overcome physiological barriers to deliver drugs more accurately to specific sites, and achieve controllable release. In this review, the first part summarizes the physiological barriers that NMOFs faced during drug delivery after intravenous injection and oral administration. The second part summarizes the current main ways to load drugs into NMOFs, mainly including pore adsorption, surface attachment, formation of covalent/coordination bonds between drug molecules and NMOFs, and in situ encapsulation. The third part is the main review part of this paper, which summarizes the surface modification methods of NMOFs used in recent years to overcome the physiological barriers and achieve effective drug delivery and disease therapy, which are mainly divided into physical modifications and chemical modifications. Finally, the full text is summarized and prospected, with the hope to provide ideas for the future development of NMOFs as drug delivery.

Bioinspired Framework Catalysts: From Enzyme Immobilization to Biomimetic Catalysis

Enzymatic catalysis has fueled considerable interest from chemists due to its high efficiency and selectivity. However, the structural complexity and vulnerability hamper the application potentials of enzymes. Driven by the practical demand for chemical conversion, there is a long-sought quest for bioinspired catalysts reproducing and even surpassing the functions of natural enzymes. As nanoporous materials with high surface areas and crystallinity, metal-organic frameworks (MOFs) represent an exquisite case of how natural enzymes and their active sites are integrated into porous solids, affording bioinspired heterogeneous catalysts with superior stability and customizable structures. In this review, we comprehensively summarize the advances of bioinspired MOFs for catalysis, discuss the design principle of various MOF-based catalysts, such as MOF-enzyme composites and MOFs embedded with active sites, and explore the utility of these catalysts in different reactions. The advantages of MOFs as enzyme mimetics are also highlighted, including confinement, templating effects, and functionality, in comparison with homogeneous supramolecular catalysts. A perspective is provided to discuss potential solutions addressing current challenges in MOF catalysis.

Post-Synthetic Surface Modification of Metal-Organic Frameworks and Their Potential Applications

Metal-organic frameworks (MOFs) are porous hybrid materials with countless potential applications. Most of these rely on their porous structure, tunable composition, and the possibility of incorporating and expanding their functions. Although functionalization of the inner surface of MOF crystals has received considerable attention in recent years, methods to functionalize selectively the outer crystal surface of MOFs are developed to a lesser extent, despite their importance. This article summarizes different types of post-synthetic modifications and possible applications of modified materials such as: catalysis, adsorption, drug delivery, mixed matrix membranes, and stabilization of porous liquids.

Nanoscale MOFs in nanomedicine applications: from drug delivery to therapeutic agents

Metal-organic frameworks (MOFs) hold great promise for widespread applications in biomedicine and nanomedicine. MOFs are one of the most fascinating nanocarriers for drug delivery, benefiting from their high porosity and facile modification. Furthermore, the tailored components of MOFs can be therapeutic agents for various treatments, including drugs as organic ligands of MOFs, active metal as central metal ions of MOFs, and their combinations as carrier-free MOF-based nanodrug. In this review, the advances in delivery systems and applications as therapeutic agents for nanoscale MOF-based materials are summarized. The challenges of MOFs in clinical translation and the future directions in the field of MOFs therapy are also discussed. We hope that more researchers will focus their attention on advancing and translating MOF-based nanodrugs into pre-clinical and clinical applications.

Enzyme-Linked Metal Organic Frameworks for Biocatalytic Degradation of Antibiotics

Metal organic frameworks (MOFs) are multi-dimensional network of crystalline material held together by bonding of metal atoms and organic ligands. Owing to unique structural, chemical, and physical properties, MOFs has been used for enzyme immobilization to be employed in different catalytic process, including catalytic degradation of antibiotics. Immobilization process other than providing large surface provides enzyme with enhanced stability, catalytic activity, reusability, and selectivity. There are various approaches of enzyme immobilization over MOFs including physical adsorption, chemical bonding, diffusion and in situ encapsulation. In situ encapsulation is one the best approach that provides extra stability from unfolding and denaturation in harsh industrial conditions. Presence of antibiotic in environment is highly damaging for human in particular and ecosystem in general. Different methods such as ozonation, oxidation, chlorination and catalysis are available for degradation or removal of antibiotics from environment, however these are associated with several issues. Contrary to these, enzyme immobilized MOFs are novel system to be used in catalytic degradation of antibiotics. Enzyme@MOFs are more stable, reusable and more efficient owing to additional support of MOFs to natural enzymes in well-established process of photocatalysis for degradation of antibiotics aimed at environmental remediation. Prime focus of this review is to present catalytic degradation of antibiotics by enzyme@MOFs while outlining their synthetics approaches, characterization, and mechanism of degradation. Furthermore, this review highlights the significance of enzyme@MOFs system for antibiotics degradation in particular and environmental remediation in general. Current challenges and future perspective of research in this field are also outlined along with concluding comments.

Graphical Abstract

A comprehensive review on bio-mimicked multimolecular frameworks and supramolecules as scaffolds for enzyme immobilization

Immobilization depicts a propitious route to optimize the catalytic performances, efficient recovery, minimizing autocatalysis, and also augment the stabilities of enzymes, particularly in unnatural environments. In this opinion, supramolecules and multimolecular frameworks have captivated immense attention to achieve profound controllable interactions between enzyme molecules and well-defined natural or synthetic architectures to yield protein bioconjugates with high accessibility for substrate binding and enhanced enantioselectivities. This scholastic review emphasizes the possibilities of associating multimolecular complexes with biological entities via several types of interactions, namely covalent interactions, host-guest complexation, π - π ${\rm{\pi }}-{\rm{\pi }}$ interactions, intra/inter hydrogen bondings, electrostatic interactions, and so forth offers remarkable applications for the modulations of enzymes. The potential synergies between artificial supramolecular structures and biological systems are the primary concern of this pedagogical review. The majority of the research primarily focused on the dynamic biomolecule-responsive supramolecular assemblages and multimolecular architectures as ideal platforms for the recognition and modulation of proteins and cells. Embracing sustainable green demeanors of enzyme immobilizations in a quest to reinforce site-selectivity, catalytic efficiency, and structural integrality of enzymes are the contemporary requirements of the biotechnological sectors that instigate the development of novel biocatalytic systems.

Synthesis and Biomedical Applications of Highly Porous Metal-Organic Frameworks

In this review, aspects of the synthesis, framework topologies, and biomedical applications of highly porous metal-organic frameworks are discussed. The term "highly porous metal-organic frameworks" (HPMOFs) is used to denote MOFs with a surface area larger than 4000 m² g^-1. Such compounds are suitable for the encapsulation of a variety of large guest molecules, ranging from organic dyes to drugs and proteins, and hence they can address major contemporary challenges in the environmental and biomedical field. Numerous synthetic approaches towards HPMOFs have been developed and discussed herein. Attempts are made to categorise the most successful synthetic strategies; however, these are often not independent from each other, and a combination of different parameters is required to be thoroughly considered for the synthesis of stable HPMOFs. The majority of the HPMOFs in this review are of special interest not only because of their high porosity and fascinating structures, but also due to their capability to encapsulate and deliver drugs, proteins, enzymes, genes, or cells; hence, they are excellent candidates in biomedical applications that involve drug delivery, enzyme immobilisation, gene targeting, etc. The encapsulation strategies are described, and the MOFs are categorised according to the type of biomolecule they are able to encapsulate. The research field of HPMOFs has witnessed tremendous development recently. Their intriguing features and potential applications attract researchers' interest and promise an auspicious future for this class of highly porous materials.

Enzyme-immobilized metal-organic frameworks: From preparation to application

As a class of widely used biocatalysts, enzymes possess advantages including high catalytic efficiency, strong specificity and mild reaction condition. However, most free enzymes have high requirements on the reaction environment and are easy to deactivate. Immobilization of enzymes on nanomaterial-based substrates is a good way to solve this problem. Metal-organic framework (MOFs), with ultra-high specific surface area and adjustable porosity, can provide a large space to carry enzymes. And the tightly surrounded protective layer of MOFs can stabilize the enzyme structure to a great extent. In addition, the unique porous network structure enables selective mass transfer of substrates and facilitates catalytic processes. Therefore, these enzyme-immobilized MOFs have been widely used in various research fields, such as molecule/biomolecule sensing and imaging, disease treatment, energy and environment protection. In this review, the preparation strategies and applications of enzymes-immobilized MOFs are illustrated and the prospects and current challenges are discussed.

The Chemistry and Applications of Metal-Organic Frameworks (MOFs) as Industrial Enzyme Immobilization Systems

Enzymatic biocatalysis is a sustainable technology. Enzymes are versatile and highly efficient biocatalysts, and have been widely employed due to their biodegradable nature. However, because the three-dimensional structure of these enzymes is predominantly maintained by weaker non-covalent interactions, external conditions, such as temperature and pH variations, as well as the presence of chemical compounds, can modify or even neutralize their biological activity. The enablement of this category of processes is the result of the several advances in the areas of molecular biology and biotechnology achieved over the past two decades. In this scenario, metal–organic frameworks (MOFs) are highlighted as efficient supports for enzyme immobilization. They can be used to ‘house’ a specific enzyme, providing it with protection from environmental influences. This review discusses MOFs as structures; emphasizes their synthesis strategies, properties, and applications; explores the existing methods of using immobilization processes of various enzymes; and lists their possible chemical modifications and combinations with other compounds to formulate the ideal supports for a given application.

A Comprehensive Review on the Use of Metal–Organic Frameworks (MOFs) Coupled with Enzymes as Biosensors

Several studies have shown the development of electrochemical biosensors based on enzymes immobilized in metal–organic frameworks (MOFs). Although enzymes have unique properties, such as efficiency, selectivity, and environmental sustainability, when immobilized, these properties are improved, presenting significant potential for several biotechnological applications. Using MOFs as matrices for enzyme immobilization has been considered a promising strategy due to their many advantages compared to other supporting materials, such as larger surface areas, higher porosity rates, and better stability. Biosensors are analytical tools that use a bioactive element and a transducer for the detection/quantification of biochemical substances in the most varied applications and areas, in particular, food, agriculture, pharmaceutical, and medical. This review will present novel insights on the construction of biosensors with materials based on MOFs. Herein, we have been highlighted the use of MOF for biosensing for biomedical, food safety, and environmental monitoring areas. Additionally, different methods by which immobilizations are performed in MOFs and their main advantages and disadvantages are presented.

Zinc-Based Metal-Organic Frameworks in Drug Delivery, Cell Imaging, and Sensing

The design and structural frameworks for targeted drug delivery of medicinal compounds and improved cell imaging have been developed with several advantages. However, metal-organic frameworks (MOFs) are supplemented tremendously for medical uses with efficient efficacy. These MOFs are considered as an absolutely new class of porous materials, extensively used in drug delivery systems, cell imaging, and detecting the analytes, especially for cancer biomarkers, due to their excellent biocompatibility, easy functionalization, high storage capacity, and excellent biodegradability. While Zn-metal centers in MOFs have been found by enhanced efficient detection and improved drug delivery, these Zn-based MOFs have appeared to be safe as elucidated by different cytotoxicity assays for targeted drug delivery. On the other hand, the MOF-based heterogeneous catalyst is durable and can regenerate multiple times without losing activity. Therefore, as functional carriers for drug delivery, cell imaging, and chemosensory, MOFs' chemical composition and flexible porous structure allowed engineering to improve their medical formulation and functionality. This review summarizes the methodology for fabricating ultrasensitive and selective Zn-MOF-based sensors, as well as their application in early cancer diagnosis and therapy. This review also offers a systematic approach to understanding the development of MOFs as efficient drug carriers and provides new insights on their applications and limitations in utility with possible solutions.

Influence of the Synthesis and Storage Conditions on the Activity of Candida antarctica Lipase B ZIF-8 Biocomposites

The biomimetic mineralization of zeolitic imidazolate framework-8 (ZIF-8) has been reported as a strategy for enzyme immobilization, enabling the heterogenization and protection of biomacromolecules. Here, we report the preparation of different Candida antarctica lipase B biocomposites (CALB@ZIF-8) formed by altering the concentrations of Zn2+ and 2-methylimidazole (2-mIM). The influence of synthetic conditions on the catalytic activity of the lipase CALB was examined by hydrolysis and transesterification assays in aqueous and organic media, respectively. We demonstrated that for both reactions, activity was retained for the biocomposites formed at low Zn2+/2-mIM ratios but notably almost entirely lost when the ligand concentration used to form the biocomposites was increased. Additionally, phosphate buffer could regenerate the activity of larger particles by degrading the crystal surfaces and releasing encapsulated CALB into solution. Transesterification reactions using CALB@ZIF-8 biocomposites were undertaken in 100% hexane, giving rise to enhanced CALB activity relative to the free enzyme. These observations highlight the fundamental importance of synthetic protocols and operating parameters for developing enzyme@MOF biocomposites with improved activity in challenging conditions.

Smart chemistry of enzyme immobilization using various support matrices - A review

The surface chemistry, pendent functional entities, and ease in tunability of various materials play a central role in properly coordinating with enzymes for immobilization purposes. Due to the interplay between the new wave of support matrices and enzymes, the development of robust biocatalytic constructs via protein engineering expands the practical scope and tunable catalysis functions. The concept of stabilization via functional entities manipulation, the surface that comprises functional groups, such as thiol, aldehyde, carboxylic, amine, and epoxy have been the important driving force for immobilizing purposes. Enzyme immobilization using multi-functional supports has become a powerful norm and presents noteworthy characteristics, such as selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness. There is a plethora of literature on traditional immobilization approaches, e.g., intramolecular chemical (covalent) attachment, adsorption, encapsulation, entrapment, and cross-linking. However, the existing literature is lacking state-of-the-art smart chemistry of immobilization. This review is a focused attempt to cover the literature gap of surface functional entities that interplay between support materials at large and enzyme of interest, in particular, to tailor robust biocatalysts to fulfill the growing and contemporary needs of several industrial sectors.

Sustainable One-Pot Immobilization of Enzymes in/on Metal-Organic Framework Materials

The industrial use of enzymes generally necessitates their immobilization onto solid supports. The well-known high affinity of enzymes for metal-organic framework (MOF) materials, together with the great versatility of MOFs in terms of structure, composition, functionalization and synthetic approaches, has led the scientific community to develop very different strategies for the immobilization of enzymes in/on MOFs. This review focuses on one of these strategies, namely, the one-pot enzyme immobilization within sustainable MOFs, which is particularly enticing as the resultant biocomposite Enzyme@MOFs have the potential to be: (i) prepared in situ, that is, in just one step; (ii) may be synthesized under sustainable conditions: with water as the sole solvent at room temperature with moderate pHs, etc.; (iii) are able to retain high enzyme loading; (iv) have negligible protein leaching; and (v) give enzymatic activities approaching that given by the corresponding free enzymes. Moreover, this methodology seems to be near-universal, as success has been achieved with different MOFs, with different enzymes and for different applications. So far, the metal ions forming the MOF materials have been chosen according to their low price, low toxicity and, of course, their possibility for generating MOFs at room temperature in water, in order to close the cycle of economic, environmental and energy sustainability in the synthesis, application and disposal life cycle.

Lipozyme 435-Mediated Synthesis of Xylose Oleate in Methyl Ethyl Ketone

In this paper, we have performed the Lipozyme 435-catalyzed synthesis of xylose oleate in methyl ethyl ketone (MEK) from xylose and oleic acid. The effects of substrates’ molar ratios, reaction temperature, reaction time on esterification rates, and Lipozyme 435 reuse were studied. Results showed that an excess of oleic acid (xylose: oleic acid molar ratio of 1:5) significantly favored the reaction, yielding 98% of xylose conversion and 31% oleic acid conversion after 24 h-reaction (mainly to xylose mono- and dioleate, as confirmed by mass spectrometry). The highest Lipozyme 435 activities occurred between 55 and 70 °C. The predicted Ping Pong Bi Bi kinetic model fitted very well to the experimental data and there was no evidence of inhibitions in the range assessed. The reaction product was purified and presented an emulsion capacity close to that of a commercial sugar ester detergent. Finally, the repeated use of Lipozyme 435 showed a reduction in the reaction yields (by 48 and 19% in the xylose and oleic acid conversions, respectively), after ten 12 h-cycles.

Controllable Microporous Framework Isomerism within Continuous Mesoporous Channels: Hierarchically Porous Structure for Capture of Bulky Molecules

To date, some attempts have been made to synthesize hierarchically porous metal-organic frameworks (HPMOFs), and in most cases, mesopores are formed in microporous frameworks. However, mass transfer and diffusion are still limited in such HPMOFs since micropores connect mesopores and mesopores are noncontinuous. Here, we fabricate a new hierarchical structure through the formation of microporous MOFs within continuous mesoporous channels. Confined space in the as-prepared mesoporous silica-containing template was used to prepare well-dispersed metal precursor of ZnO. The strategy of ligand vapor-induced crystallization was then designed to construct MOFs inside mesoporous channels, in which vapored ligand at elevated temperature diffuses and reacts with metal precursor. Our results indicate that framework isomerism is controllable by adjusting the crystallization conditions. In comparison to their microporous and mesoporous counterparts, the hierarchically porous materials show obviously enhanced adsorption performance on a series of bulky molecules including dye, enzyme, and metal-organic polyhedron.

Fragmented α-Amylase into Microporous Metal-Organic Frameworks as Bioreactors

This work presents an efficient and facile strategy to prepare an α-amylase bioreactor. As enzymes are quite large to be immobilized inside metal-organic frameworks (MOFs), the tertiary and quaternary structures of α-amylase were first disrupted using a combination of urea, dithiothreitol (DTT), and iodoacetamide (IAA). After losing its tertiary structure, the unfolded proteins can now penetrate into the microporous MOFs, affording fragmented α-amylase@MOF bioreactors. Among the different MOFs evaluated, UiO-66 gave the most promising potential due to the size-matching effect of the α-helix of the fragmented α-amylase with the pore size of UiO-66. The prepared bioreactor exhibited high yields of small carbohydrate (maltose) even when reused up to 15 times (>80% conversion).

Fast multipoint immobilization of lipase through chiral L-proline on a MOF as a chiral bioreactor

In this paper, we describe the facile preparation of a chiral catalyst by the combination of the amino acid, l-proline (Pro), and the enzyme, porcine pancreas lipase (PPL), immobilized on a microporous metal-organic framework (PPL-Pro@MOF). The multipoint immobilization of PPL onto the MOF is made possible with the aid of Pro, which also provided a chiral environment for enhanced enantioselectivity. The application of the microporous MOF is pivotal in maintaining the catalytic activity of PPL, wherein it prevented the leaching of Pro during the catalytic reaction, leading to the enhanced activity of PPL. The prepared biocatalyst was applied in asymmetric carbon-carbon bond formation, demonstrating the potential of this simple approach for chemical transformations.

Silicon-rhodamine isothiocyanate for fluorescent labelling

An efficient synthesis for silicon-rhodamines was developed, enabling the preparation and evaluation of silicon-rhodamine isothiocyanate (SITC) as a novel tool for facile fluorescent labeling. Ease of use in conjugation to amino groups, high stability and excellent photophysical properties are demonstrated. SITC-actin was found to be neutral to F-actin polymerization induction and well suited for high resolution fluorescence microscopy.

Lipase Immobilization on Macroporous ZIF-8 for Enhanced Enzymatic Biodiesel Production

Immobilization of enzyme on metal-organic frameworks (MOFs) has drawn increasing interest owing to their many well-recognized characteristics. However, the pore sizes of MOFs (mostly micropores and mesopores) limit their application for enzyme immobilization to a great extent owing to the large size of enzyme molecules. Synthesis of MOFs with macropores would therefore solve this problem, typically encountered with conventional MOFs. In this work, macroporous zeolitic imidazolate frameworks (ZIF-8), referred to as M-ZIF-8, were synthesized and used for immobilization of Aspergillus niger lipase (ANL). Immobilization efficiency using M-ZIF-8 and enzymatic catalytic performance for biodiesel preparation were investigated. The immobilized ANL on M-ZIF-8 (ANL@M-ZIF-8) showed higher enzymatic activity (6.5-fold), activity recovery (3.8-fold), thermal stability (1.4- and 3.4-fold at 80 and 100 °C, respectively), reusability (after five cycles, 68% of initial activity was maintained), and porosity than ANL on conventional ZIF-8 (ANL/ZIF-8). In addition, by using ANL@M-ZIF-8 for catalyzing a biodiesel production reaction, a higher fatty acid methyl ester yield was achieved.

Label-Free Electrochemical Immunosensor for Ultrasensitive Detection of Carbohydrate Antigen 125 Based on Antibody-Immobilized Biocompatible MOF-808/CNT

In this work, a nanocomposite of Zr-trimesic acid MOF (MOF-808) with carbon nanotube (CNT) was synthesized through an in situ formation of MOF-808 on the activated CNT. The synthesized materials were characterized by powder X-ray diffraction, transmission electron microscopy, X-ray photoluminescence spectroscopy, Brunauer-Emmett-Teller, Fourier transform infrared spectroscopy, and Raman spectroscopy. The protein compatible nature with high surface area and electrocatalytic ability of MOF-808 was utilized to construct an immunosensor for ultra low-level detection of the ovarian cancer biomarker, carbohydrate antigen 125 (CA 125). The mutual benefit of each constituent of the MOF-808/CNT composite was capable of producing highly enhanced electrochemical properties. A glassy carbon electrode modified with MOF-808/CNT was used as a platform to fabricate a label-free electrochemical immunosensor. The antibody binding sites of MOF-808/CNT were enriched by functionalization with streptavidin. The immunosensor exhibited two linear determination ranges of 0.001-0.1 and 0.1-30 ng·mL^-1, and the calculated limit of detection was 0.5 pg·mL^-1 (S/N 3). The immunosensor showed excellent reproducibility and selectivity. The patient serum sample analysis was cross-verified with the electrochemiluminescence method with a relative error of 105-110%.

Intracellular Metal-Organic Frameworks: Integrating an All-In-One Semiconductor Electrode Chip for Therapy, Capture, and Quantification of Circulating Tumor Cells

Capture, analysis, and inactivation of circulating tumor cells (CTCs) have emerged as important issues for the early diagnosis and therapy of cancer. In this study, an all-in-one sensing device was developed by integrating magnetic metal-organic framework (magMOF) nanoparticles (NPs) and TiO₂ nanotube arrays (TiNTs). The magMOF NPs are composed of a magnetic Fe₃O₄ core and a MIL-100(Fe) shell, which is loaded with glucose oxidase (GOD) and provides an intensive starvation therapy by catalyzing the consumption of cellular nutrients, thus accelerating the generation of intracellular iron ions by MIL-100(Fe) dissolution. Importantly, these iron ions not only lead to an intensive Fenton-like reaction but also establish an excellent correlation of electrochemical intensities with cancer cell numbers. Owing to the intracellular magMOF NPs, the CTCs were magnetically collected onto TiNTs. The exogenous ·OH radicals generated by TiNT photocatalysis trigger iron ions to be rapidly released out and subsequently detected via differential pulse voltammetry using TiNTs as the electrode. An excellent correlation of differential pulse voltammetry intensities with CTC numbers is obtained from 2 to 5000 cell mL^-1. This nanoplatform not only paves a way to combine starvation therapy agents with Fenton-like reaction for chemodynamic therapy but also opens up new insights into the construction of all-in-one chips for CTC capture and diagnosis.

Facile Synthesis of Enzyme-Embedded Metal-Organic Frameworks for Size-Selective Biocatalysis in Organic Solvent

In situ immobilization of enzyme into metal-organic frameworks (MOFs) is performed through a one-step and facile method. Candida antarctica lipase B (CalB) is directly embedded in zeolitic imidazolate framework (ZIF)-8 by simply mixing an aqueous solution of 2-methylimidazole and zinc nitrate hexahydrate [Zn(NO₃)₂⋅6H₂O] containing CalB at room temperature. Due to the intrinsic micropores of ZIF-8, the obtained CalB@ZIF composite is successfully applied in size-selective transesterification reaction in organic solvent. CalB@ZIF not only shows much higher catalytic activity but also exhibits higher thermal stability than free CalB. Besides, the robust ZIF-8 shell also offers the hybrid composites excellent reusability.

Metal-Organic Frameworks: A Potential Platform for Enzyme Immobilization and Related Applications

Enzymes, as natural catalysts with remarkable catalytic activity and high region-selectivities, hold great promise in industrial catalysis. However, applications of enzymatic transformation are hampered by the fragility of enzymes in harsh conditions. Recently, metal-organic frameworks (MOFs), due to their high stability and available structural properties, have emerged as a promising platform for enzyme immobilization. Synthetic strategies of enzyme-MOF composites mainly including surface immobilization, covalent linkage, pore entrapment and in situ synthesis. Compared with free enzymes, most immobilized enzymes exhibit enhanced resistance against solvents and high temperatures. Besides, MOFs serving as matrixes for enzyme immobilization show extraordinary superiority in many aspects compared with other supporting materials. The advantages of using MOFs to support enzymes are discussed. To obtain a high enzyme loading capacity and to reduce the diffusion resistance of reactants and products during the reaction, the mesoporous MOFs have been designed and constructed. This review also covers the applications of enzyme-MOF composites in bio-sensing and detection, bio-catalysis, and cancer therapy, which is concerned with interdisciplinary nano-chemistry, material science and medical chemistry. Finally, some perspectives on reservation or enhancement of bio-catalytic activity of enzyme-MOF composites and the future of enzyme immobilization strategies are discussed.

One-pot synthesis of trypsin-based magnetic metal-organic frameworks for highly efficient proteolysis

Immobilization of enzymes onto metal-organic frameworks (MOFs) through a biomimetic mineralization approach can preserve biological functionality in harsh environments. Despite the success of this approach, the alkaline environment of the reaction system, which is caused by the organic monomers of MOFs, makes it unsuitable for some pH-sensitive enzymes, especially for trypsin. Herein, we reported a facile approach for the one-pot synthesis of trypsin-immobilized magnetic zeolite imidazolate framework-8 (iron oxide@ZIF-8@trypsin), where the growth of ZIF-8 around the citric acid-modified iron oxide and immobilization of trypsin occurred simultaneously when the pH of the reaction system was changed to some extent. With a large specific surface area and a high enzyme loading capacity, the resultant iron oxide@ZIF-8@trypsin exhibited 2.6 times higher enzymatic activity than free trypsin. Moreover, it showed a favourable magnetic response (43 emu g^-1) which made the operation and recycling easy and convenient. In addition, iron oxide@ZIF-8@trypsin could be applied as an immobilized enzyme microreactor (IMER) to rapidly and efficiently digest proteins and complex human serum samples with satisfactory results, showing great promise for application in proteomic analysis.

Metal-Organic Framework Nanocarriers for Drug Delivery in Biomedical Applications

Investigation of metal-organic frameworks (MOFs) for biomedical applications has attracted much attention in recent years. MOFs are regarded as a promising class of nanocarriers for drug delivery owing to well-defined structure, ultrahigh surface area and porosity, tunable pore size, and easy chemical functionalization. In this review, the unique properties of MOFs and their advantages as nanocarriers for drug delivery in biomedical applications were discussed in the first section. Then, state-of-the-art strategies to functionalize MOFs with therapeutic agents were summarized, including surface adsorption, pore encapsulation, covalent binding, and functional molecules as building blocks. In the third section, the most recent biological applications of MOFs for intracellular delivery of drugs, proteins, and nucleic acids, especially aptamers, were presented. Finally, challenges and prospects were comprehensively discussed to provide context for future development of MOFs as efficient drug delivery systems.

Porous Inorganic and Hybrid Systems for Drug Delivery: Future Promise in Combatting Drug Resistance and Translation to Botanical Applications

BACKGROUND

Porous micro- and nanoparticles have the capacity to encapsulate a large quantity of therapeutics, making them promising delivery vehicles for a variety of applications. This review aims to highlight the latest development of inorganic and hybrid (inorganic/ organic) particles for drug delivery with an additional emphasis on combatting drug resistant cancer. We go one step further and discuss delivery applications beyond medicinal delivery, as there is generally a translation from medicinal delivery to botanic delivery after a short lag time.

METHODS

We undertook a search of relevant peer-reviewed publications. The quality of the relevant papers was appraised using standard tools. The characteristics of the papers are described herein, and the relevant material and therapeutic properties are discussed.

RESULTS

We discuss 4 classes of porous particles in terms of drug delivery and theranostics. We specifically focus on silica, calcium carbonate, metal-phenolic network, and metalorganic framework particles. Other relevant biomedically relevant applications are discussed and we highlight outstanding therapeutic results in the relevant literature.

CONCLUSION

The findings of this review confirm the importance of studying and utilizing porous particles for therapeutic delivery. Moreover, we show that the properties of porous particles that make them promising for medicinal drug delivery also make them promising candidates for agro-industrial applications.

Rational Design of Nanocarriers for Intracellular Protein Delivery

Protein/antibody therapeutics have exhibited the advantages of high specificity and activity even at an extremely low concentration compared to small molecule drugs. However, they are accompanied by unfavorable physicochemical properties such as fragile tertiary structure, large molecular size, and poor penetration of the membrane, and thus the clinical use of protein drugs is hindered by inefficient delivery of proteins into the host cells. To overcome the challenges associated with protein therapeutics and enhance their biopharmaceutical applications, various protein-loaded nanocarriers with desired functions, such as lipid nanocapsules, polymeric nanoparticles, inorganic nanoparticles, and peptides, are developed. In this review, the different strategies for intracellular delivery of proteins are comprehensively summarized. Their designed routes, mechanisms of action, and potential therapeutics in live cells or in vivo are discussed in detail. Furthermore, the perspective on the new generation of delivery systems toward the emerging area of protein-based therapeutics is presented as well.

Metal-Organic Frameworks in Polymer Science: Polymerization Catalysis, Polymerization Environment, and Hybrid Materials

The development of metal-organic frameworks (MOFs) has had a significant impact on various fields of chemistry and materials science. Naturally, polymer science also exploited this novel type of material for various purposes, which is due to the defined porosity, high surface area, and catalytic activity of MOFs. The present review covers various topics of MOF/polymer research beginning with MOF-based polymerization catalysis. Furthermore, polymerization inside MOF pores as well as polymerization of MOF ligands is described, which have a significant effect on polymer structures. Finally, MOF/polymer hybrid and composite materials are highlighted, encompassing a range of material classes, like bulk materials, membranes, and dispersed materials. In the course of the review, various applications of MOF/polymer combinations are discussed (e.g., adsorption, gas separation, drug delivery, catalysis, organic electronics, and stimuli-responsive materials). Finally, past research is concluded and an outlook toward future development is provided.

Zinc-based metal-organic frameworks as nontoxic and biodegradable platforms for biomedical applications: review study

Development of biomedical systems for controllable drug delivery systems and construction of biosensors is imperative to reduce side effects of common treatment techniques and enhance the therapeutic efficacy. To address this issue, metal-organic frameworks (MOFs) as hybrid porous polymeric structures have attracted worldwide attention due to their unprecedented opportunities in vast range of applications in diverse fields including chemistry, biological, and medicinal science as gas storage/separation, sensing, and drug delivery systems. Recently, biomedical application has become an interesting and promising issue for development and usage of multi-functional MOFs. Flexible chemical composition and versatile porous structure of MOFs enable the engineering and enhancement of their medical formulation and functionality as practical carriers for whether therapeutic or imaging agents. One important point in this domain is the efficient delivery of drugs in the body using nontoxic and biodegradable carriers. This review brings together the literatures that addressing the biomedical applications of Zinc-based MOFs (i.e. as drug delivery systems or nontoxic agent in matter of therapeutic applications) to present recent achievements in this interesting field.