Synthesis of patterned enzyme–metal–organic framework composites by ink-jet printing

3D-Printed MOF Monoliths: Fabrication Strategies and Environmental Applications

Metal-organic frameworks (MOFs) have been extensively considered as one of the most promising types of porous and crystalline organic-inorganic materials, thanks to their large specific surface area, high porosity, tailorable structures and compositions, diverse functionalities, and well-controlled pore/size distribution. However, most developed MOFs are in powder forms, which still have some technical challenges, including abrasion, dustiness, low packing densities, clogging, mass/heat transfer limitation, environmental pollution, and mechanical instability during the packing process, that restrict their applicability in industrial applications. Therefore, in recent years, attention has focused on techniques to convert MOF powders into macroscopic materials like beads, membranes, monoliths, gel/sponges, and nanofibers to overcome these challenges.Three-dimensional (3D) printing technology has achieved much interest because it can produce many high-resolution macroscopic frameworks with complex shapes and geometries from digital models. Therefore, this review summarizes the combination of different 3D printing strategies with MOFs and MOF-based materials for fabricating 3D-printed MOF monoliths and their environmental applications, emphasizing water treatment and gas adsorption/separation applications. Herein, the various strategies for the fabrication of 3D-printed MOF monoliths, such as direct ink writing, seed-assisted in-situ growth, coordination replication from solid precursors, matrix incorporation, selective laser sintering, and digital light processing, are described with the relevant examples. Finally, future directions and challenges of 3D-printed MOF monoliths are also presented to better plan future trajectories in the shaping of MOF materials with improved control over the structure, composition, and textural properties of 3D-printed MOF monoliths.

A review of synthesis, fabrication, and emerging biomedical applications of metal-organic frameworks

The overwhelming potential of porous coordination polymers (PCP), also known as Metal-Organic Frameworks (MOFs), especially their nanostructures for various biomedical applications, have made these materials worth investigating for more applications and uses. MOFs unique structure has enabled them for most applications, particularly in biomedical and healthcare. A number of very informative review papers are available on the biomedical applications of MOFs for the reader's convenience. However, many of those reviews focus mainly on drug delivery applications, and no significant work has been reported on other MOFs for biomedical applications. This review aims to present a compact and highly informative global assessment of the recent developments in biomedical applications (excluding drug-delivery) of MOFs along with critical analysis. Researchers have recently adopted both synthetic and post-synthetic routes for the fabrication and modification of MOFs that have been discussed and analyzed. A critical review of the latest reports on the significant and exotic area of bio-sensing capabilities and applications of MOFs has been given in this study. In addition, other essential applications of MOFs, including photothermal therapy, photodynamic therapy, and antimicrobial activities, are also included. These recently grown emergent techniques and cancer treatment options have gained attention and require further investigations to achieve fruitful outcomes. MOF's role in these applications has been thoroughly discussed, along with future challenges and valuable suggestions for the research community that will help meet future demands.

Challenges, Prospects, and Emerging Applications of Inkjet-Printed Electronics: A Chemist's Point of View

Driven by the development of new functional inks, inkjet-printed electronics has achieved several milestones upon moving from the integration of simple electronic elements (e.g., temperature and pressure sensors, RFID antennas, etc.) to high-tech applications (e.g. in optoelectronics, energy storage and harvesting, medical diagnosis). Currently, inkjet printing techniques are limited by spatial resolution higher than several micrometers, which sets a redhibitorythreshold for miniaturization and for many applications that require the controlled organization of constituents at the nanometer scale. In this Review, we present the physico-chemical concepts and the equipment constraints underpinning the resolution limit of inkjet printing and describe the contributions from molecular, supramolecular, and nanomaterials-based approaches for their circumvention. Based on these considerations, we propose future trajectories for improving inkjet-printing resolution that will be driven and supported by breakthroughs coming from chemistry. Please check all text carefully as extensive language polishing was necessary. Title ok? Yes.

De Novo Engineering of Metal-Organic Framework-Printed In Vitro Diagnostic Devices for Specific Capture and Release of Tumor Cells

Herein, a paper-based in vitro diagnostic device (IVD) is developed via inkjet printing of de novo engineered, boronic acid-rich metal-organic frameworks (BMOFs). The newly developed BMOFs simultaneously possess crystalline and amorphous structure, mesopore size, large surface area, and retain a high level of boronic acid integration. After printing the BMOFs on the filter paper, the BMOF-printed paper IVD shows a rapid response time (40 min) towards cancer cell capture and its maximum cell capture capacity reaches approximately (4.5 ±1.1) ×10⁴ cells cm^-2 . Furthermore, the BMOF-printed IVD shows nine times higher capture ability of cancer cells than non-cancerous cells, suggesting its excellent selectivity. Importantly, the pH-tunable affinity of BMOF to glucose enables its dual-responsive behavior without affecting cell viability. In addition, a desired cell pattern could be achieved by directly drawing BMOFs onto a silicon substrate, highlighting its capacity as a miniaturized device for tumor cell capture and analysis. This simple and label-free nanoplatform enables new opportunities for designing MOF-based smart devices for diverse biomedical applications such as a cost-effective IVD technologies for cancer diagnosis, genotyping, and prognosis.

Advancement in functionalized luminescent frameworks and their prospective applications as inkjet-printed sensors and anti-counterfeit materials

Supramolecular luminescent frameworks with conjugated architectures exhibits interesting photophysical properties with phenomenal chemical and thermal stability. This has instigated global researchers towards its extensive application in toxic analyte detection and the formulation of anti-counterfeit materials. In correlation with this present scenario, luminescent metal-organic frameworks (LMOFs), possessing tailorable structural and functional properties and exceptional physicochemical features, have been categorized as emerging 'smart materials'. Interestingly, LMOFs have assisted in the rapid development of an effectual sensing platform and swift fabrication of anti-counterfeit materials on desirable substrates with the aid of 'Inkjet Printing', which is a viable, low-cost, and high-resolution technology. Inkjet printing is an excellent material deposition technique in the modern era owing to its easy settling over flexible substrates, simplistic emergence of large area image patterns with improved throughput, minimal cost, explicit resolution, and least waste generation. The present review provides state-of-the-art progress on LMOFs based (i) luminescent security ink fabrication with static and dynamic multinodal luminescent materials and (ii) sensory device formulation for the easy and instantaneous recognition of hazardous analytes through the 'Inkjet Printing' technology. This techno-chemical integration will be certainly beneficial to prevent the growth of counterfeit materials and monitor the bioaccumulation of hazardous analytes in our ecological system.

Enzyme embedded microfluidic paper-based analytic device (μPAD): a comprehensive review

Low-cost paper-based analytical devices are the latest generation of portable lab-on-chip designs that offers an innovative platform for the on/off-site analysis (biosensing) of target analytes, especially in rural and remote areas. Recently, microfluidic paper-based analytical devices (μPADs) have attained significant recognition owing to their exciting fundamental features such as: ease of fabrication, rapid operation, and precise interpretations. The incorporation of enzymes with paper-based analytical devices significantly improves analytical performance while exhibiting excellent chemical and storage stability. In addition to that, these devices are highly compact, portable, easy-to-use, and do not require any additional sophisticated equipment for the detection and quantification of target analytes. This review provides a holistic insight into design, fabrication, and enzyme immobilization strategies for the development of enzyme-μPADs, which enables them to be widely implemented for in-field analysis. It also highlights the recent application of enzyme-μPADs in the area of: biomedical, food safety, and environmental monitoring while exploring the mechanisms of detection involved. Further, in order to improve the accuracy of analysis, researchers have designed a smartphone-based scanning tool for multi-variant point-of-care devices, which is summarized in the latter part of the review. Finally, the future perspectives and outlook of major challenges associated with enzyme-μPADs are discussed with their possible solutions. The development of enzyme integrated μPADs will open a new avenue as an exceptional analytical tool to explore various applications.HIGHLIGHTSEnzyme embedded paper-based analytical devices are a revolution in the field of biosensing.The design, fabrication, and enzyme immobilization on μPADs have been comprehensively discussed.The application of enzyme-μPADs food safety, environmental monitoring, and clinical diagnostic have been reviewed.Smartphones can be used as an on-site, user-friendly, and compact next-gen scanning tool for biosensing.

Calix[4]arene tetracarboxylic acid-treated lipase immobilized onto metal-organic framework: Biocatalyst for ester hydrolysis and kinetic resolution

Metal organic frameworks (MOFs) are hybrid organic inorganic materials with unique properties such as well-defined pore structure, extremely high surface area, excellent chemical-thermal stability. MOFs-based constructs have been extensively engineered and used for applications, such as enzyme immobilization for bio-catalysis. To obtained a zeolitic imidazole framework-8 (ZIF-8) for enzyme immobilization, Candida rugosa lipase (CRL) was pretreated with calix [4]arene tetracarboxylic acid (Calix) and reacted with Zn and imidazole by co-precipitation method. The prepared biocomposite was characterized by SEM, EDX, FT-IR, and XRD. The prepared CRL@Calix-ZIF-8 with high encapsulation efficiency showed improved resistance to alkali and thermal conditions. The CRL@Calix-ZIF-8 with the biocatalytic activity was 2-folds higher than that of the CRL@ZIF-8 (without Calix). The free lipase lost its catalytic activity completely at 60 °C after 100 min, while the CRL@Calix-ZIF-8 and CRL@ZIF-8 retained about 84% and 73%. It was found that CRL@Calix-ZIF-8 and CRL@ZIF-8 still retained ~83 and 67% of catalytic activity after its 6th use, respectively. The kinetic resolution of the immobilized lipases was examined for enantioselective hydrolysis of racemic naproxen methyl ester. CRL@Calix-ZIF-8 showed enantioselectivity against the racemic naproxen methyl ester, with E = 183 and 131 compared to the CRL@ZIF-8.

Rising Up: Hierarchical Metal-Organic Frameworks in Experiments and Simulations

Controlled synthesis across several length scales, ranging from discrete molecular building blocks to size- and morphology-controlled nanoparticles to 2D sheets and thin films and finally to 3D architectures, is an advanced and highly active research field within both the metal-organic framework (MOF) domain and the overall material science community. Along with synthetic progress, theoretical simulations of MOF structures and properties have shown tremendous progress in both accuracy and system size. Further advancements in the field of hierarchically structured MOF materials will allow the optimization of their performance; however, this optimization requires a deep understanding of the different synthesis and processing techniques and an enhanced implementation of material modeling. Such modeling approaches will allow us to select and synthesize the highest-performing structures in a targeted rational manner. Here, recent progress in the synthesis of hierarchically structured MOFs and multiscale modeling and associated simulation techniques is presented, along with a brief overview of the challenges and future perspectives associated with a simulation-based approach toward the development of advanced hierarchically structured MOF materials.

Metal-Organic-Framework-Based Enzymatic Microfluidic Biosensor via Surface Patterning and Biomineralization

Recently, the biomineralization of enzyme in metal-organic-framework (enzyme-MOF) composite have shown a great potential to increase enzymes stability without compromising their activity; hence, it is desirable for its applications in biosensing devices. Nonetheless, most of the enzyme-MOF research has been focusing on enzyme encapsulation in particle form, which limits its synthesis flexibility for practical applications because of its requirement for postsynthesis immobilization onto solid support. Therefore, to develop a diagnostic device out of the biomineralized enzyme, surface patterning and integration of microfluidic system offers many advantages. In this work, mussel-inspired polydopamine/polyethyleneimine (PDA/PEI) coating is employed to pattern enzyme-MOF in microfluidic channels and exploit the wettability gradient for "pumpless transportation" effect. As a proof of concept, we combine a cascade reaction of glucose oxidase (GOx) and horseradish peroxidase (HRP) enzymes to detect glucose into a patterned zeolitic imidazole framework-8 (ZIF-8) thin film on a flexible polymeric substrate. The results show that the ZIF-8/GOx&HRP in situ composites on PDA/PEI patterns have good acid and thermal stability compared with samples without ZIF-8. ZIF-8/GOx&HRP in situ shows high selectivity toward glucose, linear sensitivity of 0.00303 Abs/μM, and the limit of detection of 8 μM glucose concentration. An unexpected benefit of this approach is the ability of the ZIF-8 thin-film structure to provide a diffusion limiting effect for substrate influx, thus, producing high range of linear response range (8 μM to 5 mM of glucose). This work provides insights into the spatial location of the enzymes in MOF thin films and the potential of such patterning techniques for MOF-based biosensors using other types of biological elements such as antibodies and aptamers.

Metal-Organic Frameworks for the Development of Biosensors: A Current Overview

This review focuses on the fabrication of biosensors using metal-organic frameworks (MOFs) as recognition and/or transducer elements. A brief introduction discussing the importance of the development of new biosensor schemes is presented, describing these coordination polymers, their properties, applications, and the main advantages and drawbacks for the final goal. The increasing number of publications regarding the characteristics of these materials and the new micro- and nanofabrication techniques allowing the preparation of more accurate, robust, and sensitive biosensors are also discussed. This work aims to offer a new perspective from the point of view of materials science compared to other reviews focusing on the transduction mechanism or the nature of the analyte. A few examples are discussed depending on the starting materials, the integration of the MOF as a part of the biosensor and, in a deep detail, the fabrication procedure.

Investigation of Controlled Growth of Metal-Organic Frameworks on Anisotropic Virus Particles

Biomimetic mineralization with metal-organic frameworks (MOF), typically zeolitic imidazolate framework-8 (ZIF-8), is an emerging strategy to protect sensitive biological substances against denaturing environmental stressors such as heat and proteolytic agents. Additionally, this same biomimetic mineralization process has the potential of being used to create distinct core-shell architectures using genetically or chemically modified viral nanoparticles. Despite the proliferation of examples for ZIF-8 growth on biological or proteinaceous substrates, systematic studies of these processes are few and far between. Herein, we employed the tobacco mosaic virus (TMV) as a model biological template to investigate the biomimetic mineralization of ZIF-8, which has been proven to be a robust MOF for encasing and protecting inlaid biological substances. Our study shows a systematic dependence upon ZIF-8 crystallization parameters, e.g., ligand to metal molar ratio and metal concentration, which can yield several distinct morphologies of TMV@ZIF-8 composites and phases of ZIF-8. Further investigation using charged synthetic conjugates, time dependent growth analysis, and calorimetric analysis has shown that the TMV-Zn interaction plays a pivotal role in the final morphology of the TMV@ZIF-8, which can take the form of either core-shell bionanoparticles or large crystals of ZIF-8 with entrapped TMV located exclusively on the outer facets. The design rules outlined here, it is hoped, will provide guidance in biomimetic mineralization of MOFs on proteinaceous materials using ZIF-8.