Zirconium-Based Metal-Organic Frameworks for the Removal of Protein-Bound Uremic Toxin from Human Serum Albumin

Nanocellulose/Graphene Oxide Composite Beads as a Novel Hemoperfusion Adsorbent for Efficient Removal of Bilirubin Plasma

Conventional hemoperfusion adsorbents suffer from inefficiency and poor biocompatibility. Cellulose, a natural polysaccharide with biocompatible, biodegradable, and nontoxic properties, was combined with graphene oxide (GO) to fabricate composite beads (TGO) for blood purification. GO synthesized via a modified Hummers method was complexed with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibrils (TOCNs). Increasing GO content (2-20 wt %) enhanced TGO's specific surface area (256.4-289.0 m2 g-1) while retaining an ∼10 nm pore size. TGO demonstrated exceptional adsorption capacities: bilirubin (418.4 mg g-1), creatinine (23.5 mg g-1), uric acid (146.6 mg g-1), and Cu2+ (171.9 mg g-1). The beads exhibited excellent hemocompatibility (hemolysis rate <5%) and prolonged recalcification time (585 ± 5.2 s). Notably, TGO restored blood bilirubin levels to normal within 30 min, highlighting its potential for blood purification.

Efficient uremic toxins adsorption from simulated blood by immobilization of metal organic frameworks anchored Sephadex beads

The current study outlines the removal of Creatinine, p-Cresol sulfate, and Hippuric acid from simulated blood using three new granules: Fe-BTC@Sephadex, Cu-BTC@Sephadex, and Co-BTC@Sephadex. Beads were used to adsorbed toxic chemicals, and the effects of various experimental parameters were examined in the adsorption optimization process. The framework's adsorption isotherms were explained by the application of the Freundlich and Langmuir models. The kinetics of adsorption is represented by a pseudo-first and second-order equation. The morphology and structure of the Fe-BTC@ Sephadex, Co-BTC@ Sephadex, and Cu-BTC@Sephadex beads were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The adsorption capacities for creatinine were 545.69, 339.76, and 189.88 mg/g for Fe-BTC@ Sephadex, Cu-BTC@ Sephadex, and Co-BTC@ Sephadex, respectively, according to the results; the corresponding adsorption capacities for hippuric acid were 323.78, 206.79, and 68.059 mg/g, and the maximum adsorption capacities for p-Cresol sulfate were 122.65, 71.268, and 40.347 mg/g, respectively. These were, in fact, promising findings that have implications for an industrial-scale transportable artificial kidney.

Adsorption Dynamics of Uremic Toxins to Cyclodextrin-Coated Magnetic Nano-Adsorbents

Chronic kidney disease entails a progressive decline in kidney function, hindering the kidneys' ability to excrete fluid, electrolytes, and metabolites. This dysfunction leads to metabolite accumulation in the bloodstream, which can reach toxic concentrations. Hemodialysis is an effective means of treating patients with kidney failure, but it does not clear all toxins effectively. Engineered nano-adsorbents can potentially improve the removal of retained toxins, particularly protein-bound types. Magnetic nanoparticles coated with α-, β-, and γ-cyclodextrin were synthesized, and physicochemical properties were characterized using thermogravimetric analysis, transmission electron microscopy, dynamic light scattering, and ζ-potential for their physiochemical properties. The effect of surface chemistry and incubation time on toxin adsorption was investigated using quantitative mass spectrometry techniques. All particle types demonstrated toxin adsorption to some level. Overall, the adsorption process was independent of metabolite concentration, suggesting a dynamic interplay between surface properties and solution composition. This insight will contribute to developing innovative adsorbent films designed to remove uremic toxins effectively.

Clearance of Protein-Bound Uremic Toxins Using Anion Nanotraps with Record High Uptake

Traditional hemodialysis often fails to remove protein-bound uremic toxins (PBUTs) like p-cresyl sulfate (pCS) and indoxyl sulfate (IS) due to their strong binding to human serum albumin, which is linked to adverse cardiovascular outcomes. Herein, a class of cationic polymeric networks, denoted as CPN-X6-CPN-X9, are reported for the efficient removal of PBUTs. The abundant imidazole-based nanotraps in these cationic polymeric networks confer a highly positive charge density, resulting in CPN-X7 achieving a maximum sorption capacity of 1000.8 mg/g for pCS and CPN-X6 offering a maximum sorption capacity of 1028.4 mg/g for IS, surpassing all previously reported sorbents. Furthermore, CPN-X9, which is relatively hydrophobic, exhibits remarkable selectivity in competitive experiments involving large amount of chloride ions and serum albumin, attaining removal rates of up to 74% for pCS and 93% for IS in the recycling in vitro dialysis mode. Meanwhile, CPN-X9 demonstrates excellent recyclability over five cycles, and the cationic polymeric network materials exhibit satisfactory hemocompatibility. The sorption mechanism of the anion exchange process is fully elucidated and verified by density functional theory (DFT) calculations. This study provides valuable insights into enhancing the removal efficiency of PBUTs and presents broad prospects in the field of clinical blood purification.

Recent advances in cell membrane-coated porphyrin-based nanoscale MOFs for enhanced photodynamic therapy

Porphyrins-based nanoscale metal-organic frameworks (nMOFs) has been widely utilized to kills tumor cells by generating cytotoxic reactive oxygen species (ROS). However, porphyrin based nMOFs (por-nMOFs) still face challenges such as rapid immune clearance and weak tumor targeting. Researchers have discovered that using a top-down biomimetic strategy, where nMOFs are coated with cell membranes, can promote long blood circulation, evade the reticuloendothelial system, and improve cancer cell targeting, thereby significantly enhancing the photodynamic therapy (PDT) effect of nMOFs. This review summarizes the recent work on different cell membranes-coated por-nMOFs for enhanced tumor PDT. This review details the changes in physicochemical properties, enhanced homotypic cancer cell-selective endocytosis, improved tumor tissue targeting, and increased cytotoxicity and effective in vivo tumor suppression after the nMOFs are wrapped with cell membranes. Additionally, this review compares the biological functions of various types of cell membranes, including cancer cell membranes, red blood cell membranes, aptamer-modified red blood cell membranes, and hybrid membranes from the fusion of cancer and immune cells. The review highlights the enhanced immunogenic cell death function when using hybrid membranes derived from the fusion of cancer and immune cell membranes. By summarizing the augmented PDT effects and the combined antitumor outcomes with other therapeutic modalities, this review aims to provide new insights into the biomedical applications of por-nMOFs and offer more references for the preclinical application of porphyrin-based photosensitizers.

Biomedical Metal-Organic Framework Materials: Perspectives and Challenges

Metal-organic framework (MOF) materials are gaining significant interest in biomedical research, owing to their high porosity, crystallinity, and structural and compositional diversity. Their versatile hybrid organic/inorganic chemistry endows MOFs with the capacity to retain organic (drug) molecules, metals, and gases, to effectively channel electrons and photons, to survive harsh physiological conditions such as low pH, and even to protect sensitive biomolecules. Extensive preclinical research has been carried out with MOFs to treat several pathologies and, recently, their integration with other biomedical materials such as stents and implants has demonstrated promising performance in regenerative medicine. However, there remains a significant gap between MOF preclinical research and translation into clinically and societally relevant medicinal products. Here, we outline the intrinsic features of MOFs and discuss how these are suited to specific biomedical applications like detoxification, drug and gas delivery, or as (combination) therapy platforms. We furthermore describe relevant examples of how MOFs have been engineered and evaluated in different medical indications, including cancer, microbial, and inflammatory diseases. Finally, we critically examine the challenges facing their translation into the clinic, with the goal of establishing promising research directions and more realistic approaches that can bridge the translational gap of MOFs and MOF-containing (nano)materials.

Understanding the Adsorption and Diffusion Behaviors of PBUT in Biocompatible MOFs

With the increasing incidence of chronic kidney disease, the effective control of protein-bound uremic toxins (PBUTs), which are difficult to remove through dialysis, has become a priority. In this study, the adsorption and diffusion behaviors of several metal-organic frameworks (MOFs) for PBUTs (indoxyl sulfate and p-cresyl sulfate) were studied by molecular dynamics (MD) simulations and umbrella sampling. For the NU series of MOFs, good correlations between the Gibbs free energy (ΔG) and the experimental clearance rates of PBUTs are found. For the adsorption behaviors, in terms of ΔG, DAJWET exhibits the best adsorption effect for indoxyl sulfate (IS), whereas NU-1000 shows the best effect for p-cresyl sulfate (pCS). Similar trends observed in the radial distribution function and mean square displacement results suggest that the π-π stacking interactions play a crucial role in the adsorption and diffusion of PBUTs by MOFs. Furthermore, it can be concluded that MOFs with highly conjugated groups (porphyrin rings and pyrene groups) tend to generate more PBUT attraction, and provide design principles for potential MOF candidates in the removal of PBUTs.

Computer-aided nanodrug discovery: recent progress and future prospects

Nanodrugs, which utilise nanomaterials in disease prevention and therapy, have attracted considerable interest since their initial conceptualisation in the 1990s. Substantial efforts have been made to develop nanodrugs for overcoming the limitations of conventional drugs, such as low targeting efficacy, high dosage and toxicity, and potential drug resistance. Despite the significant progress that has been made in nanodrug discovery, the precise design or screening of nanomaterials with desired biomedical functions prior to experimentation remains a significant challenge. This is particularly the case with regard to personalised precision nanodrugs, which require the simultaneous optimisation of the structures, compositions, and surface functionalities of nanodrugs. The development of powerful computer clusters and algorithms has made it possible to overcome this challenge through in silico methods, which provide a comprehensive understanding of the medical functions of nanodrugs in relation to their physicochemical properties. In addition, machine learning techniques have been widely employed in nanodrug research, significantly accelerating the understanding of bio-nano interactions and the development of nanodrugs. This review will present a summary of the computational advances in nanodrug discovery, focusing on the understanding of how the key interfacial interactions, namely, surface adsorption, supramolecular recognition, surface catalysis, and chemical conversion, affect the therapeutic efficacy of nanodrugs. Furthermore, this review will discuss the challenges and opportunities in computer-aided nanodrug discovery, with particular emphasis on the integrated "computation + machine learning + experimentation" strategy that can potentially accelerate the discovery of precision nanodrugs.

Bioinspired Dual Hemin-Bonded G-Quadruplex and Histidine-Functionalized Metal-Organic Framework for Sensitive Biosensing

Biomimetic enzymes have emerged as ideal alternatives to natural enzymes, and there is considerable interest in designing biomimetic enzymes with enhanced catalytic performance to address the low activity of the current biomimetic enzymes. In this study, we proposed a meaningful strategy for constructing an efficient peroxidase-mimicking catalyst, called HhG-MOF, by anchoring histidine (H) and dual hemin-G-quadruplex DNAzyme (double hemin covalently linked to 3' and 5' terminals of G-quadruplex DNA, short as hG) to a mesoporous metal-organic framework (MOF). This design aims to mimic the microenvironment of natural peroxidase. Remarkably, taking a terbium MOF as a typical model, the initial rate of the resulting catalyst was found to be 21.1 and 4.3 times higher than that of Hh-MOF and hG-MOF, respectively. The exceptional catalytic properties of HhG-MOF can be attributed to its strong affinity for substrates. Based on the inhibitory effect of thiocholine (TCh) produced by the reaction between acetylcholinesterase (AChE) and acetylthiocholine, a facile, cost-effective, and sensitive colorimetric method was designed based on HhG-MOF for the measurement of AChE, a marker of several neurological diseases, and its inhibitor. This allowed a linear response in the 0.002 to 1 U L-1 range, with a detection limit of 0.001 U L-1. Furthermore, the prepared sensor demonstrated great selectivity and performed well in real blood samples, suggesting that it holds promise for applications in the clinical field.

MOF-Based Platform for Kidney Diseases: Advances, Challenges, and Prospects

Kidney diseases are important diseases that affect human health worldwide. According to the 2020 World Health Organization (WHO) report, kidney diseases have become the top 10 causes of death. Strengthening the prevention, primary diagnosis, and action of kidney-related diseases is of great significance in maintaining human health and improving the quality of life. It is increasingly challenging to address clinical needs with the present technologies for diagnosing and treating renal illness. Fortunately, metal-organic frameworks (MOFs) have shown great promise in the diagnosis and treatment of kidney diseases. This review summarizes the research progress of MOFs in the diagnosis and treatment of renal disease in recent years. Firstly, we introduce the basic structure and properties of MOFs. Secondly, we focus on the utilization of MOFs in the diagnosis and treatment of kidney diseases. In the diagnosis of kidney disease, MOFs are usually designed as biosensors to detect biomarkers related to kidney disease. In the treatment of kidney disease, MOFs can not only be used as an effective adsorbent for uremic toxins during hemodialysis but also as a precise treatment of intelligent drug delivery carriers. They can also be combined with nano-chelation technology to solve the problem of the imbalance of trace elements in kidney disease. Finally, we describe the current challenges and prospects of MOFs in the diagnosis and treatment of kidney diseases.

Metal-organic framework-based adsorbents for blood purification: progress, challenges, and prospects

Blood purification, such as hemodialysis (HD), plasma exchange (PE), and hemoperfusion (HP), is widely applied in patients with organ failure (such as kidney and liver failure). Among them, HP mainly relies on porous adsorbents to efficiently adsorb accumulated metabolic wastes and toxins, thus improving purification efficiency. Metal-organic frameworks (MOFs), with a high porosity, large surface area, high loading capacity, and tailorable topology, are emerging as some of the most promising materials for HP. Compared with non-metal framework counterparts, the self-built metal centers of MOFs feature the intrinsic advantages of coordination with toxin molecules. However, research on MOFs in blood purification is insufficient, particularly in contrast to materials applied in other biomedical applications. Thus, to broaden this area, this review first discusses the essential characteristics, potential mechanisms, and structure-function relationship between MOFs and toxin adsorption based on porosity, topology, ligand functionalization, metal centers, and toxin types. Moreover, the stability, utilization safety, and hemocompatibility of MOFs are illustrated for adsorbent selection. The current development and progress in MOF composites for HD, HP, and extracorporeal membrane oxygenation (ECMO) are also summarized to highlight their practicability. Finally, we propose future opportunities and challenges from materials design and manufacture to the computational prediction of MOFs in blood purification. It is anticipated that our review will expand the interest of researchers for more impact in this area.

Design and Advanced Manufacturing of NU-1000 Metal-Organic Frameworks with Future Perspectives for Environmental and Renewable Energy Applications

Metal-organic frameworks (MOFs) represent a relatively new family of materials that attract lots of attention thanks to their unique features such as hierarchical porosity, active metal centers, versatility of linkers/metal nodes, and large surface area. Among the extended list of MOFs, Zr-based-MOFs demonstrate comparably superior chemical and thermal stabilities, making them ideal candidates for energy and environmental applications. As a Zr-MOF, NU-1000 is first synthesized at Northwestern University. A comprehensive review of various approaches to the synthesis of NU-1000 MOFs for obtaining unique surface properties (e.g., diverse surface morphologies, large surface area, and particular pore size distribution) and their applications in the catalysis (electro-, and photo-catalysis), CO2 reduction, batteries, hydrogen storage, gas storage/separation, and other environmental fields are presented. The review further outlines the current challenges in the development of NU-1000 MOFs and their derivatives in practical applications, revealing areas for future investigation.

MOF magic: zirconium-based frameworks in theranostic and bio-imaging applications

Over the past two decades, metal-organic frameworks (MOFs) have garnered substantial scientific interest across diverse fields, spanning gas storage, catalysis, biotechnology, and more. Zirconium, abundant in nature and biologically relevant, offers an appealing combination of high content and low toxicity. Consequently, Zr-based MOFs have emerged as promising materials with significant potential in biomedical applications. These MOFs serve as effective nanocarriers for controlled drug delivery, particularly for challenging antitumor and retroviral drugs in cancer and AIDS treatment. Additionally, they exhibit prowess in bio-imaging applications. Beyond drug delivery, Zr-MOFs are notable for their mechanical, thermal, and chemical stability, making them increasingly relevant in engineering. The rising demand for stable, non-toxic Zr-MOFs facilitating facile nanoparticle formation, especially in drug delivery and imaging, is noteworthy. This review focuses on biocompatible zirconium-based metal-organic frameworks (Zr-MOFs) for controlled delivery in treating diseases like cancer and AIDS. These MOFs play a key role in theranostic approaches, integrating diagnostics and therapy. Additionally, their utility in bio-imaging underscores their versatility in advancing medical applications.

Metal-organic framework (UiO-66 and UiO-66-NH2)-based adsorbents for bilirubin removal used in hemoperfusion

Excessive accumulation of bilirubin in patients with hyperbilirubinemia can lead to tissue and organ damage and neurological diseases, and is even life-threatening in severe cases. Hemoperfusion is an effective method for removing bilirubin, but clinically used hemoperfusion adsorbents have unsatisfactory adsorption capacity and kinetics. In order to obtain a safe and efficient bilirubin adsorbent, Zr-based Metal-Organic Framework (MOF) material UiO-66 with high specific surface area and aqueous medium stability was prepared and modified with varying degrees of amination to improve its adsorption capacity. According to adsorption experiments in aqueous solution and simulated plasma, it was confirmed that the unsaturated coordinated zirconium in UiO-66 can effectively induce the aggregation and precipitation of free bilirubin unbound to albumin and the amino group on UiO-66-NH2 has a strong affinity for albumin bound bilirubin. The adsorption effect of UiO-66-NH2 with a high degree of amino modification is significantly stronger than that of UiO-66-NH2 with a low degree of modification. In simulated plasma with a bilirubin concentration of 40 mg dL-1, the adsorption capacities of UiO-66 and UiO-66-NH2-1.9 can reach 69.08 mg g-1 and 81.13 mg g-1. The adsorption isotherm fitting and adsorption kinetics fitting results also show that UiO-66 and UiO-66-NH2 are good adsorbents for bilirubin. In dynamic adsorption, the adsorbents also showed good performance and did not affect the protein in the plasma. The hemolysis test, coagulation time test, and cytotoxicity test confirmed that the bilirubin adsorbents based on UiO-66 and UiO-66-NH2 have good blood compatibility and biocompatibility. This study provides new ideas for the development of a novel bilirubin adsorbent and a theoretical basis for the study of bilirubin adsorption mechanisms.

Self-Aggregated Nanoscale Metal-Organic Framework for Targeted Pulmonary Decorporation of Uranium

The limited availability of effective agents for removing actinides from the lungs significantly restricts the effectiveness of medical treatments for nuclear emergencies. Inhalation is the primary route of internal contamination in 44.3% of actinide-related accidents, leading to the accumulation of radionuclides in the lungs and resulting in infections and potential tumor formation (tumorigenesis). This study focuses on the synthesis of a nanometal-organic framework (nMOF) material called ZIF-71-COOH, which is achieved by post-synthetic carboxyl functionalization of ZIF-71. The material demonstrates high and selective adsorption of uranyl, while also exhibiting increased particle size (≈2100 nm) when it aggregates in the blood, enabling passive targeting of the lungs through mechanical filtration. This unique property facilitates the rapid enrichment and selective recognition of uranyl, making nano ZIF-71-COOH highly effective in removing uranyl from the lungs. The findings of this study highlight the potential of self-aggregated nMOFs as a promising drug delivery system for targeted uranium decorporation in the lungs.

Efficient selective removal of uremic toxin precursor by olefin-linked covalent organic frameworks for nephropathy treatment

Indoxyl sulfate is a protein-bound uremic toxin synthesized from indole that cannot be efficiently removed by the hemodialysis method and thus becomes a key risk factor for the progression of chronic kidney disease. Here, we develop a non-dialysis treatment strategy to fabricate an ultramicroporous olefin-linked covalent organic framework with high crystallinity in a green and scalable fashion for selectively removing the indoxyl sulfate precursor (i.e., indole) from the intestine. Various analyses show that the resulting material exhibits excellent gastrointestinal fluid stability, high adsorption efficiency, and good biocompatibility. Notably, it realizes the efficient and selective removal of indole from the intestine and significantly attenuates serum indoxyl sulfate level in vivo. More importantly, the selective removal efficacy of indole is substantially higher than that of the commercial adsorbent AST-120 used in the clinic. The present study opens up a new avenue to eliminate indoxyl sulfate by a non-dialysis strategy and further expands the in vivo applications of covalent organic frameworks.

MOFs-alginate/polyacrylic acid/poly (ethylene imine) heparin-mimicking beads as a novel hemoadsorbent for bilirubin removal in vitro and vivo models

Metal-organic frameworks (MOFs) have a potential application in blood purification, but their microcrystalline nature has hampered their industrial application. Here, novel MOFs-polymer beads based on UiO, sodium alginate, polyacrylic acid, and poly (ethylene imine) were prepared and applied as a whole blood hemoadsorbent for the first time. The amidation among polymers immobilized UiO66-NH₂ into the network of the optimal product (SAP-3), and the NH₂ of UiO66-NH₂ significantly increased the removal rate (70 % within 5 min) of SAP-3 on bilirubin. The adsorption of SAP-3 on bilirubin mainly obeyed the pseudo-second-order kinetic, Langmuir isotherm and Thomas models with a maximum adsorption capacity (q_m) of 63.97 mg·g^-1. Experimental and density functional theory simulation results show that bilirubin was mainly adsorbed by UiO66-NH₂via electrostatic force, hydrogen bonding, and π-π interactions. Notably, the adsorption in vivo show that the total bilirubin removal rate in the whole blood of the rabbit model was up to 42 % after 1 h of adsorption. Given its excellent stability, cytotoxicity, and hemocompatibility, SAP-3 has a great potential in hemoperfusion therapy. This study proposes an effective strategy for settling the powder property of MOFs and could provide experimental and theoretical references for application of MOFs in blood purification.

Assembly of chemically modified protein nanocages into 3D materials for the adsorption of uremic toxins

Hemodialysis fails to remove protein-bound uremic toxins that are attributed with high cardiovascular risk. Application of adsorption materials is a viable strategy, but suitable biocompatible adsorbents are still not available. Here, we demonstrate that adsorbents based on the bottom-up assembly of the intrinsically biocompatible protein cage ferritin are applicable for toxin adsorption. Due to the size-exclusion effect of its pores, only small molecules such as uremic toxins can enter the protein cage. Protein redesign techniques that target selectively the inner surface were used to introduce anchor sites for chemical modification. Porous crystalline adsorbents were fabricated by bottom-up assembly of the protein cage. Linkage of up to 96 phenylic or aliphatic molecules per container was verified by ESI-MS. Materials based on unmodified ferritin cages can already adsorb the uremic toxins. The adsorption capacity could be increased by about 50% through functionalization with hydrophobic molecules reaching 458 μg g^-1 for indoxyl sulfate. The biohybrid materials show no contamination with endotoxins and do not activate blood platelets. These findings demonstrate the great potential of protein-based adsorbents for the clearance of uremic toxins: modifications enhance toxin adsorption without diminishing the biocompatibility of the final protein-based material.

Effectively Decontaminating Protein-Bound Uremic Toxins in Human Serum Albumin Using Cationic Metal-Organic Frameworks

In the field of replacement of conventional dialysis treatment, searching superior materials for removal of protein-bound uremic toxins is a challenge on account of strong interactions between proteins and uremic toxins. Herein, we first adopted cationic metal-organic frameworks (MOFs), ZJU-X6 and ZJU-X7, as sorbents to decontaminate uremic toxins (p-cresyl sulfate and indoxyl sulfate). ZJU-X6 and ZJU-X7 exhibited innate advantage for sequestration of uremic toxins by utilizing a positive charge framework with exchangeable anions. Especially, ZJU-X6 showed a higher sorption capacity and faster sorption kinetics than those of most reported materials. Moreover, the cationic MOF materials could selectively remove uremic toxins even if in the presence of competitive chloride ions and proteins. Meanwhile, pair distribution function (PDF) and density functional theory (DFT) were employed to elucidate the sorption mechanism between uremic toxins and sorbents. This work suggests an attractive avenue for constructing new types of sorbents to eliminate uremic toxins for uremia treatment.

Incorporating zeolitic-imidazolate framework-8 nanoparticles into kidney scaffolds: a first step towards innovative renal therapies

We demonstrate for the first time the potential of zeolitic-imidazolate framework-8 nanoparticles to be incorporated within a renal scaffold while retaining their ability to remove uremic toxins (mainly hydrophobic toxins like p-cresol) under flow conditions. This work may pave the way for the future development of novel adsorbents for dialysis and/or artificial kidneys.

Microfluidic electrospray generation of porous magnetic Janus reduced graphene oxide/carbon composite microspheres for versatile adsorption

HYPOTHESIS

Graphene-based microparticles materials are broadly utilized in all sorts of fields owing to their outstanding properties. Despite great progress, the present graphene microparticles still face challenges in the aspects of size uniformity, motion flexibility, and tailorable surface chemistry, which limit their application in some specific fields, such as versatile adsorption. Hence, the development of novel graphene microparticles with the aforementioned characteristics is urgently required.

EXPERIMENTS

We presented a simple microfluidic electrospray strategy to generate magnetic Janus reduced graphene oxide/carbon (rGO/C) composite microspheres with a variety of unique features. Specifically, the microfluidic electrospray method endowed the obtaiend microspheres with sufficient size uniformity as well as magnetic responsive motion ability. Additionally, magnetic-mediated surface assembly of phase transition lysozyme (PTL) nanofilm on the microspheres rendered the deposited area hydrophilic while non-deposited area hydrophobic.

FINDINGS

Such magnetic Janus rGO/C composite microspheres with regionalized wettability characteristics not only showed prominent performance in adsorbing organic liquids with high adsorption capacity and remarkable reusability but also displayed satisfying biocompatibility for the efficient uptake of bilirubin. More encouragingly, the microspheres could serve as adsorbents in a simulative hemoperfusion setup, which further demonstrated the clinical application potential of the magnetic Janus rGO/C microspheres. Thus, we anticipate that the obtained magnetic Janus rGO/C composite microspheres could show multifunctional properties toward water treatment and blood molecule cleaning.

Effects of microsize on the biocompatibility of UiO67 from protein-adsorption behavior, hemocompatibility, and histological toxicity

The biocompatibility of metal-organic frameworks (MOFs) is necessary to humans but is far from being sufficiently addressed. This study focused on the effects of microsize on the biocompatibility of MOFs by selecting UiO67 with micron and submicron size as the MOFs models. Under the dose metric of surface area, the binding constant between UiO67 and human serum albumin (HSA) gradually increased with increased UiO67 size. Submicron UiO67 induced stronger conformational transformation and more greatly affected the protein surface hydrophobicity than micron UiO67. Micron UiO67 also inhibited the esterase-like activity of HSA through competitive inhibition mechanism, whereas submicron UiO67 inhibited it through noncompetitive inhibition mechanism. The size of UiO67 had little effect on hemocompatibility. A smaller size of UiO67, corresponded with a higher IC50 value for 293 T and LO2 cells, and the adsorption of HSA can effectively improve cytotoxicity. In vivo toxicity evaluations revealed that all UiO67 did not cause obvious distortion of organs, and they were metabolized primarily in the kidney. These results provided useful information about the toxicity of MOFs and experimental references for the development of MOFs-based engineering materials.

Nano-remediation technologies for the sustainable mitigation of persistent organic pollutants

The absence of novel and efficient methods for the elimination of persistent organic pollutants (POPs) from the environment is a serious concern in the society. The pollutants release into the atmosphere by means of industrialization and urbanization is a massive global hazard. Although, the eco-toxicity associated with nanotechnology is still being debated, nano-remediation is a potentially developing tool for dealing with contamination of the environment, particularly POPs. Nano-remediation is a novel strategy to the safe and long-term removal of POPs. This detailed review article presents an important perspective on latest innovations and future views of nano-remediation methods used for environmental decontamination, like nano-photocatalysis and nanosensing. Different kinds of nanomaterials including nanoscale zero-valent iron (nZVI), carbon nanotubes (CNTs), magnetic and metallic nanoparticles, silica (SiO2) nanoparticles, graphene oxide, covalent organic frameworks (COFs), and metal organic frameworks (MOFs) have been summarized for the mitigation of POPs. Furthermore, the long-term viability of nano-remediation strategies for dealing with legacy contamination was considered, with a particular emphasis on environmental and health implications. The assessment goes on to discuss the environmental consequences of nanotechnology and offers consensual recommendations on how to employ nanotechnology for a greater present and a more prosperous future.

Nanoscale bioconjugates: A review of the structural attributes of drug-loaded nanocarrier conjugates for selective cancer therapy

Nanobioconjugates are nanoscale drug delivery vehicles that have been conjugated to or decorated with biologically active targeting ligands. These targeting ligands can be antibodies, peptides, aptamers, or small molecules such as vitamins or hormones. Most research studies in this field have been devoted to targeting cancer. Moreover, the nanostructures can be designed with an additional level of targeting by being designed to be stimulus-responsive or "smart" by a judicious choice of materials to be incorporated into the hybrid nanostructures. This stimulus could be an acidic pH, raised temperature, enzyme, ultrasound, redox potential, an externally applied magnetic field, or laser irradiation. In this case, the smart capability can increase the accumulation at the tumor site or the on-demand drug release, while the ligand ensures selective binding to the tumor cells. The present review highlights some interesting studies classified according to the nanostructure material. These materials include natural substances (polysaccharides), multi-walled carbon nanotubes (and halloysite nanotubes), metal-organic frameworks and covalent-organic frameworks, metal nanoparticles (gold and silver), and polymeric micelles.

Leveraging Isothermal Titration Calorimetry to Obtain Thermodynamic Insights into the Binding Behavior and Formation of Metal-Organic Frameworks

Isothermal titration calorimetry (ITC) is a technique which directly measures the thermodynamic parameters of binding events. Although historically it has been used to investigate interactions in biological macromolecules and the kinetics of enzyme-catalyzed reactions, ITC has also been demonstrated to provide relevant thermodynamic information about interactions in synthetic systems, such as those in metal-organic frameworks (MOFs). MOFs are a family of crystalline porous materials that have been widely studied as supports for molecules ranging from gases to biomolecules through physisorption and chemisorption. Herein, we offer a perspective on the current applications of ITC in MOFs, including the mechanism of small molecule adsorption and the formation of MOF-based composite materials through noncovalent interactions. Experimental considerations specific to running ITC experiments in MOF systems are reviewed on the basis of existing reports. We conclude by discussing underexplored, but promising, MOF-related research directions which could be elucidated by ITC.

Strategies for optimizing urea removal to enable portable kidney dialysis: A reappraisal

BACKGROUND

Portable hemodialysis has the potential to improve health outcomes and quality of life for patients with kidney failure at reduced costs. Urea removal, required for dialysate regeneration, is a central function of any existing/potential portable dialysis device. Urea in the spent dialysate coexists with non-urea uremic toxins, nutrients, and electrolytes, all of which will interfere with the urea removal efficiency, regardless of whether the underlying urea removal mechanism is based on urease conversion, direct urea adsorption, or oxidation. The aim of the current review is to identify the amount of the most prevalent chemicals being removed during a single dialysis session and evaluate the potential benefits of an urea-selective membrane for portable dialysis.

METHODS

We have performed a literature search using Web of Science and PubMed databases to find available articles reporting (or be able to calculate from blood plasma concentration) > 5 mg of individually quantified solutes removed during thrice-weekly hemodialysis sessions. If multiple reports of the same solute were available, the reported values were averaged, and the geometric mean of standard deviations was taken. Further critical literature analysis of reported dialysate regeneration methods was performed using Web of Science and PubMed databases.

RESULTS

On average, 46.0 g uremic retention solutes are removed in a single conventional dialysis session, out of which urea is only 23.6 g. For both urease- and sorbent-based urea removal mechanisms, amino acids, with 7.7 g removal per session, could potentially interfere with urea removal efficiency. Additionally for the oxidation-based urea removal system, plentiful nutrients such as glucose (24.0 g) will interfere with urea removal by competition. Using a nanofiltration membrane between dialysate and oxidation unit with a molecular weight cutoff (MWCO) of ~200 Da, 67.6 g of non-electrolyte species will be removed in a single dialysis session, out of which 44.0 g are non-urea molecules. If the membrane MWCO is further decreased to 120 Da, the mass of non-electrolyte non-urea species will drop to 9.3 g. Reverse osmosis membranes have been shown to be both effective at blocking the transport of non-urea species (creatinine for example with ~90% rejection ratio), and permissive for urea transport (~20% rejection ratio), making them a promising urea selective membrane to increase the efficiency of the oxidative urea removal system.

CONCLUSIONS

Compiled are quantified solute removal amounts greater than 5 mg per session during conventional hemodialysis treatments, to act as a guide for portable dialysis system design. Analysis shows that multiple chemical species in the dialysate interfere with all proposed portable urea removal systems. This suggests the need for an additional protective dialysate loop coupled to urea removal system and an urea-selective membrane.

Evaluation of the Adsorption-Accessible Surface Area of MIL-53(Al) using Cannabinoids in a Closed System

Cannabinoids are important industrial analytes commonly assayed with high-pressure liquid chromatography (HPLC). In this study, we evaluate the suitability of MIL-53(Al), a commercially available metal-organic framework (MOF), as a stationary phase for cannabinoid separations. The suitability of an MOF for a given separation is hypothesized to be limited by the ability of a given molecule to enter the pore of the MOF. To evaluate the extent of possible adsorptive interactions between cannabinoids and the interior surface area of MIL-53(Al), the radii of gyration (R_g) and solvent-accessible surface areas were calculated for three cannabinoids, namely, cannabidiol, cannabinol, and Δ9-tetrahydrocannabinol, as well as the MOF. These values were used to calculate the theoretical adsorption capacity of the MOF, using four competing adsorption models. The R_g of cannabinoids (4.1 Å) is larger than one MOF pore aperture dimension (4.0 × 5.0 Å). The adsorption capacity was measured by relating a decrease in the cannabinoid concentration in acetonitrile when exposed to 100 mg of MOF. The cannabinoid uptake by the MOF was estimated using the relative standard deviation (RSD) of the soaking solution assay, as the decomposition-corrected RSD as uptake (DCRU). The DCRU was calculated as 0.007 ± 0.004 μg_cannabinoids/mg_MOF. These findings indicate that most of the MOF surface area was inaccessible for adsorption by cannabinoids due to size-exclusion effects. The implication of this work is that the suitability of an MOF for adsorptive separations, such as liquid chromatography, must have an upper limit for the size of the analyte. Additionally, MOFs may generally be more suitable for separations in the gas phase, where adsorbates are not hindered by the presence of a solvation shell.

Recent trends in therapeutic application of engineered blood purification materials for kidney disease

Blood purification is a commonly used method to remove excess metabolic waste in the blood in renal replacement therapy. The sufficient removal of these toxins from blood can reduce complications and improve survival lifetime in dialysis patients. However, the current biological blood purification materials in clinical practice are not ideal, where there is an unmet need for producing novel materials that have better biocompatibility, reduced toxicity, and, in particular, more efficient toxin clearance rates and a lower cost of production. Given this, this review has carefully summarized newly developed engineered different structural biomedical materials for blood purification in terms of types and structure characteristics of blood purification materials, the production process, as well as interfacial chemical adsorption properties or mechanisms. This study may provide a valuable reference for fabricating a user-friendly purification device that is more suitable for clinical blood purification applications in dialysis patients.

Nanoscale Metal−Organic Frameworks and Their Nanomedicine Applications

Abundant connectivity among organic ligands and inorganic metal ions makes the physical and chemical characters of metal-organic frameworks (MOFs) could be precisely devised and modulated for specific applications. Especially nanoscale MOFs (NMOFs), a unique family of hybrid nanomaterials, with merits of holding the nature as the mainstay MOFs and demonstrating particle size in nanoscale range which enable them prospect platform in clinic. Adjustability of composition and structure allows NMOFs with different constituents, shapes, and characteristics. Oriented frameworks and highly porous provide enough space for packing therapeutic cargoes and various imaging agents efficiently. Moreover, the relatively labile metal-ligand bonds make NMOFs biodegradable in nature. So far, as a significant class of biomedically relevant nanomaterials, NMOFs have been explored as drug carriers, therapeutic preparation, and biosensing and imaging preparation owing to their high porosity, multifunctionality, and biocompatibility. This review provides up-to-date developments of NMOFs in biomedical applications with emphasis on size control, synthetic approaches, and surfaces functionalization as well as stability, degradation, and toxicity. The outlooks and several crucial issues of this area are also discussed, with the expectation that it may help arouse widespread attention on exploring NMOFs in potential clinical applications.

Remarkable Uptake of Deoxynivalenol in Stable Metal-Organic Frameworks

Deoxynivalenol (DON), which is known as one of the most harmful mycotoxins, has contaminated food and feed and attracted concerns worldwide. However, the effective adsorptive removal of DON to ensure food safety still is a challenge, which is ascribed to the poor planarity and larger steric hindrance of DON molecules. Here, a new Zr(IV)-based metal-organic framework, entitled BUT-16 with one-dimensional channels and N-atom-decorated pore surface, is designed, prepared, and utilized for the adsorptive removal of DON. It exhibits excellent adsorption ability with an adsorption capacity of 46 mg/g higher than all reported adsorbents until now and a rapid adsorption rate of 0.031 g mg^-1 min^-1. DFT calculation and X-ray photoelectron spectroscopy results of the guest-loaded phase suggest that the record-breaking adsorption could be due to the cooperation of hydrogen bonding and Zr···O interaction between DON molecules and BUT-16 host. Most importantly, BUT-16 can effectively adsorb and remove DON in the simulated gastric fluid, but DON adsorbed on BUT-16 is hardly desorbed in the simulated intestinal fluid. The results demonstrate that BUT-16 has great promising application for the control of DON in foods and feeds.

Insights into Paraben Adsorption by Metal-Organic Frameworks for Analytical Applications

Metal-organic frameworks (MOFs) are attractive materials used as sorbents in analytical microextraction applications for contaminants of emerging concern (CECs) from environmental liquid matrices. The demanding specs for a sorbent in the analytical application can be comprehensively studied by considering the interactions of the target analytes with the frameworks by the use of single-crystal X-ray diffraction, computational analysis, and adsorption studies, including the kinetic ones. The current study intends a better understanding of the interactions of target CECs (particularly, propylparaben (PPB) as a model) and three Zn-based layered pillared MOFs: CIM-81 [Zn₂(tz)₂(bdc)] (Htz = 1,2,4-triazole and H₂bdc = 1,4-benzenedicarboxylic acid) and their amino derivatives [Zn₂(NH₂-tz)₂(bdc)] CIM-82 and [Zn₂(tz)₂(NH₂-bdc)] CIM-83 (NH₂-Htz = 3-amino-1,2,4-triazole and NH₂-H₂bdc = 2-amino-1,4-benzenedicarboxylic acid). The crystal structures of the two solvate compounds (dma@CIM-81 (dma = dimethylacetamide) and acetone@CIM-81) were solved by single-crystal X-ray diffraction to determine the points of interaction between the framework and the guest molecules. They also served as a starting point for the computational modeling of the PPB@CIM-81 compound, showing that up to two PPB molecules can be hosted in one of the pores, while only one can be trapped in the second pore type, leading to a maximum theoretical capacity of 291.9 mg g^-1. This value is close to the value obtained by the adsorption isotherm experiment for CIM-81 (283 mg g^-1). This value is, by far, higher than those previously reported for other materials for the removal of PPB from water, and also higher than the experimental values obtained for CIM-82 (54 mg g^-1) and CIM-83 (153 mg g^-1). The kinetics of adsorption is not very fast, with uptake of about 40% in 3 h, although a 70% release in methanol is achieved in 1 h. In addition, a further comparison of performance in analytical microextraction (requiring only 10 mg of CIM-81) was carried out together with chromatographic analysis to support all insights attained, with the method being able to monitor CECs as low as μg L^-1 levels in complex environmental water samples, thus performing successfully for water monitoring even in multicomponent scenarios.

In Search of Effective UiO-66 Metal-Organic Frameworks for Artificial Kidney Application

The removal of uremic toxins from patients with acute kidney injury is a key issue in improving the quality of life for people requiring peritoneal dialysis. The currently utilized method for the removal of uremic toxins from the human organism is hemodialysis, performed on semipermeable membranes where the uremic toxins, along with small molecules, are separated from proteins and blood cells. In this study, we describe a mixed-linker modulated synthesis of zirconium-based metal-organic frameworks for efficient removal of uremic toxins. We determined that the efficient adsorption of uremic toxins is achieved by optimizing the ratio between -amino functionalization of the UiO-66 structure with 75% of -NH2 groups within organic linker structure. The maximum adsorption of hippuric acid and 3-indoloacetic acid was achieved by UiO-66-NH2 (75%) and by UiO-66-NH2 (75%) 12.5% HCl prepared by modulated synthesis. Furthermore, UiO-66-NH2 (75%) almost completely adsorbs 3-indoloacetic acid bound to bovine serum albumin, which was used as a model protein to which uremic toxins bind in the human body. The high adsorption capacity was confirmed in recyclability test, which showed almost 80% removal of 3-indoloacetic acid after the third adsorption cycle. Furthermore, in vitro cytotoxicity tests as well as hemolytic activity assay have proven that the UiO-66-based materials can be considered as potentially safe for hemodialytic purposes in living organisms.

Reduction of protein-bound uraemic toxins in plasma of chronic renal failure patients: A systematic review

BACKGROUND

Protein-bound uraemic toxins (PBUTs) accumulate in patients with chronic kidney disease and impose detrimental effects on the vascular system. However, a unanimous consensus on the most optimum approach for the reduction of plasma PBUTs is still lacking.

METHODS

In this systematic review, we aimed to identify the most efficient clinically available plasma PBUT reduction method reported in the literature between 1980 and 2020. The literature was screened for clinical studies describing approaches to reduce the plasma concentration of known uraemic toxins. There were no limits on the number of patients studied or on the duration or design of the studies.

RESULTS

Out of 1274 identified publications, 101 studies describing therapeutic options aiming at the reduction of PBUTs in CKD patients were included in this review. We stratified the studies by the PBUTs and the duration of the analysis into acute (data from a single procedure) and longitudinal (several treatment interventions) trials. Reduction ratio (RR) was used as the measure of plasma PBUTs lowering efficiency. For indoxyl sulphate and p-cresyl sulphate, the highest RR in the acute studies was demonstrated for fractionated plasma separation, adsorption and dialysis system. In the longitudinal trials, supplementation of haemodialysis patients with AST-120 (Kremezin®) adsorbent showed the highest RR. However, no superior method for the reduction of all types of PBUTs was identified based on the published studies.

CONCLUSIONS

Our study shows that there is presently no technique universally suitable for optimum reduction of all PBUTs. There is a clear need for further research in this field.