Tunable Size Research Articles

Multifunctional metal–organic frameworks as promising nanomaterials for antimicrobial strategies

Abstract Bacterial infections pose a serious threat to human health. While antibiotics have been effective in treating bacterial infectious diseases, antibiotic resistance significantly reduces their effectiveness. Therefore, it is crucial to develop new and effective antimicrobial strategies. Metal–organic frameworks (MOFs) have become ideal nanomaterials for various antimicrobial applications due to their crystalline porous structure, tunable size, good mechanical stability, large surface area, and chemical stability. Importantly, the performance of MOFs can be adjusted by changing the synthesis steps and conditions. Pure MOFs can release metal ions to modulate cellular behaviors and kill various microorganisms. Additionally, MOFs can act as carriers for delivering antimicrobial agents in a desired manner. Importantly, the performance of MOFs can be adjusted by changing the synthesis steps and conditions. Furthermore, certain types of MOFs can be combined with traditional photothermal or other physical stimuli to achieve broad-spectrum antimicrobial activity. Recently an increasing number of researchers have conducted many studies on applying various MOFs for diseases caused by bacterial infections. Based on this, we perform this study to report the current status of MOFs-based antimicrobial strategy. In addition, we also discussed some challenges that MOFs currently face in biomedical applications, such as biocompatibility and controlled release capabilities. Although these challenges currently limit their widespread use, we believe that with further research and development, new MOFs with higher biocompatibility and targeting capabilities can provide diversified treatment strategies for various diseases caused by bacterial infections.

Macromolecular interactions and geometrical confinement determine the 3D diffusion of ribosome-sized particles in live Escherichia coli cells

The crowded bacterial cytoplasm is composed of biomolecules that span several orders of magnitude in size and electrical charge. This complexity has been proposed as the source of the rich spatial organization and apparent anomalous diffusion of intracellular components, although this has not been tested directly. Here, we use biplane microscopy to track the 3D motion of self-assembled bacterial genetically encoded multimeric nanoparticles (bGEMs) with tunable size (20 to 50 nm) and charge (-3,240 to +2,700 e) in live Escherichia coli cells. To probe intermolecular details at spatial and temporal resolutions beyond experimental limits, we also developed a colloidal whole-cell model that explicitly represents the size and charge of cytoplasmic macromolecules and the porous structure of the bacterial nucleoid. Combining these techniques, we show that bGEMs spatially segregate by size, with small 20-nm particles enriched inside the nucleoid, and larger and/or positively charged particles excluded from this region. Localization is driven by entropic and electrostatic forces arising from cytoplasmic polydispersity, nucleoid structure, geometrical confinement, and interactions with other biomolecules including ribosomes and DNA. We observe that at the timescales of traditional single molecule tracking experiments, motion appears subdiffusive for all particle sizes and charges. However, using computer simulations with higher temporal resolution, we find that the apparent anomalous exponents are governed by the region of the cell in which bGEMs are located. Molecular motion does not display anomalous diffusion on short time scales and the apparent subdiffusion arises from geometrical confinement within the nucleoid and by the cell boundary.

Colored Cellulose Nanoparticles with High Stability and Easily Modified Surface for Accurate and Sensitive Multiplex Lateral Flow Assay.

Decentralized testing using multiplex lateral flow assays (mLFAs) to simultaneously detect multiple analytes can significantly enhance detection efficiency, reduce cost and time, and improve analytic accuracy. However, the challenges, including the monochromatic color of probe particles, interference between different test lines, and reduced specificity and sensitivity, severely hinder mLFAs from wide use. In this study, we prepared polydopamine (PDA)-coated dyed cellulose nanoparticles (dCNPs@P) with tunable colors as the probe for mLFAs. Cellulose nanoparticles (CNPs) were synthesized with uniform spheric shapes and tunable sizes. Dye molecules were loaded on CNPs via a mature industrial dyeing method. The PDA shell provided a reactive surface for facile receptor conjugation and protected the dye from leaking. dCNPs@P displayed a higher signal intensity than gold nanoparticles. They also had higher stability to tolerate salt and varied pH. The dCNP@P-based mLFAs were successfully applied to detect multiple mycotoxins in cereals and determine the levels of inflammatory biomarkers to differentiate between viral and bacterial infections. The tests represented high specificity and accuracy and were more sensitive than the tests using gold nanoparticles. The quantified detection was accessible by measuring the intensities of the colorimetric or photothermal signals. Overall, this study provides a practical system solution for mLFAs based on colored dCNPs@P.

Covalent organic frameworks as superior adsorbents for the removal of toxic substances.

Developing new materials capable of the safe and efficient removal of toxic substances has become a research hotspot in the field of materials science, as these toxic substances pose a serious threat to human health, both directly and indirectly. Covalent organic frameworks (COFs), as an emerging class of crystalline porous materials, have advantages such as large specific surface area, tunable pore size, designable structure, and good biocompatibility, which have been proven to be a superior adsorbent design platform for toxic substances capture. This review will summarize the synthesis methods of COFs and the properties and characteristics of typical toxicants, discuss the design strategies of COF-based adsorbents for the removal of toxic substances, and highlight the recent advancements in COF-based adsorbents as robust candidates for the efficient removal of various types of toxicants, such as animal toxins, microbial toxins, phytotoxins, environmental toxins, etc. The adsorption performance and related mechanisms of COF-based adsorbents for different types of toxic substances will be discussed. The complex host-guest interactions mainly include electrostatic, π-π interactions, hydrogen bonding, hydrophobic interactions, and molecular sieving effects. In addition, the adsorption performance of various COF-based adsorbents will be compared, and strategies such as reasonable adjustment of pore size, introduction of functionalities, and preparation of composite materials can effectively improve the adsorption efficiency of toxins. Finally, we also point out the challenges and future development directions that COFs may face in the field of toxicant removal. It is expected that this review will provide valuable insights into the application of COF-based adsorbents in the removal of toxicants and the development of new materials.

Transcriptomic modifications across the genome and potential hazards of pulmonary fibrosis caused by metal-organic frameworks.

Metal-Organic Frameworks (MOFs) have shown great promise in environmental protection, owing to their exceptional properties including ultrahigh surface area and porosity, tunable pore size, and easy chemical functionalization. However, emerging evidence from experimental studies indicates that MOFs have side effects on human health due to metal ions doping, resulting in excessive reactive oxygen species (ROS) production, pro-inflammatory responses, and liver fibrosis. In this study, we investigated the impact of MOF-199 on human bronchial epithelial (HBE) cells by using transcriptome sequencing analysis. The results indicated that the stimulation of MOF-199 enhanced ROS generation, upregulated cytoplasmic Ca2+ levels, then activated the Grb2/SOS/Ras/Raf pathway, induced cell apoptosis, and ultimately resulted in lung fibroblasts through TGF-β secretion. The results were validated in vitro and in vivo. Therefore, it is necessary to carefully evaluate the nanosafety of MOF-199 in environment treatments.

Microwave-Assisted Green Synthesis of Fluorescent Graphene Quantum Dots: Metal Sensing, Antioxidant Properties, and Biocompatibility Insights.

Graphene quantum dots (GQDs) are highly valued for their chemical stability, tunable size, and biocompatibility. Utilizing green chemistry, a microwave-assisted synthesis method was employed to produce water-soluble GQDs from Mangifera Indica leaf extract. This approach is efficient, cost-effective, and environmentally friendly, offering reduced reaction times, energy consumption, and uniform particle sizes, and has proven advantageous over other methods. Water-soluble GQDs were synthesized using Mangifera Indica leaf extract, which ranged less than 15nm in diameter, confirmed by high-resolution transmission electron microscopy with a lattice spacing of 0.34nm. The GQDs exhibited strong photoluminescence with bright red fluorescence under UV light and excitation-independent emission at 662nm with excitation wavelengths ranging from 300 to 500nm, achieving a quantum yield of 10.3%. A peak at 27.2˚ was recorded corresponding to the graphite's (002) plane diffraction peak. Raman spectroscopy confirmed their graphitic nature and sp2 crystallinity, with an intensity ratio of D and G peak ID/IG ratio of 1.12. Biocompatibility assays (MTT and live/dead) showed better results at lower concentrations (1mg/ml) while higher concentrations (2mg/ml) showed reduced efficacy. Antioxidant tests revealed increased DPPH scavenging activity with higher GQD concentrations and longer incubation times. The GQDs demonstrated excellent performance as fluorescent biosensors for Ni2⁺ (0.15ppm) and Fe3⁺ (0.20ppm), with high selectivity in river water samples, highlighting their potential for environmental and health applications.

Sprayed Aqueous Microdroplets for Spontaneous Synthesis of Functional Microgels.

The development of sustainable synthesis route to produce functional and bioactive polymer colloids has attracted much attention. Most strategies are based on the polymerization of monomers or crosslinking of prepolymers by enzyme- or cell-mediated reactions or specific catalysts in confined emulsions. Herein, a facile solution spray method was developed for spontaneous synthesis of microgels without use of confined emulsion, additional initiators/catalysts and deoxygenation, which addresses the challenges in traditional microgel synthesis. The polarization of air-water interface of the microdroplets can spontaneously split hydroxide ions in water to produce hydroxyl radicals, thereby initiating polymerization and crosslinking in air environment. This synthesis strategy is applicable to a variety of monomers and enables the fabrication of microgels with tunable chemical structures and variable sizes. Importantly, the synthesis route also allows for the preparation of enzyme- or drug-loaded microgels via the in-situ encapsulation, which also display high enzymatic activity and stimuli-triggered drug release. Therefore, this work not only is of great significance to macromolecular science and microdroplet chemistry, but also may bring new insights into cellular biochemistry and even prebiotic chemistry due to the prevalence of microdroplets in the environment.

An analytical review of the therapeutic application of recent trends in MIL-based delivery systems in cancer therapy.

MILs (Materials Institute Lavoisier), as nanocarriers based on metal-organic frameworks (MOFs), are one of the most advanced drug delivery vehicles that are now a major part of cancer treatment research. This review article highlights the key features and components of MIL nanocarriers for the development and improvement of these nanocarriers for drug delivery. Surface coatings are one of the key components of MIL nanocarriers, which play the role of stabilizing the nanocarrier, pH-dependent drug release, increasing the half-life of the drug, and targeting the carrier. MIL nanocarriers have been synthesized mainly by thermal and hydrothermal methods due to their single-step nature and the ability to produce individual crystals with tunable sizes. According to the data available in the literature, MIL-53 and MIL-101 are the best MILs for drug delivery. These MILs have a high ability to release drugs under acidic conditions, indicating their high efficiency compared to other MILs. In addition to drugs, these nanocarriers can also carry fluorescent, photothermal, and photodynamic agents. These agents allow the MIL nanocarriers to benefit from the therapeutic potential of photothermal and photodynamic agents in addition to the therapeutic capacity of the drug. Furthermore, the fluorescent active ingredient gives these nanocarriers a further tracking capability in addition to the inherent tracking capability of MRI. Therefore, MIL nanocarriers as theranostic carriers have the potential to revolutionize both drug delivery and imaging.

Colloidal Germanium Quantum Dots with Broadly Tunable Size and Light Emission.

Germanium (Ge) colloidal quantum dots (CQDs) were synthesized by thermal decomposition of GeI2 using capping ligand mixtures of oleylamine (OAm), octadecene (ODE), and trioctylphosphine (TOP). Average diameters could be tuned across a wide range, from 3 to 18 nm, by adjusting reactant concentrations, heating rates, and reaction temperatures. OAm promotes decomposition of GeI2 to Ge and serves as a weakly bound capping ligand. ODE displaces OAm during the reaction to terminate particle growth and prevent surface oxidation. TOP is necessary for obtaining nanocrystals larger than 11 nm. The Ge CQDs have relatively narrow size distributions and exhibit size-dependent, band-edge photoluminescence (PL), with peak energies from 0.8 to 1.34 eV, across a wide spectral range in the infrared (IR).

Coordination Bond‐Based Nanosystems for Manipulating Niche Framework in Biomedical Applications

ABSTRACTThe extensive connectivity between organic ligands and inorganic metal ions enables precise design and physicochemical modification of metal–organic frameworks (MOFs) for various applications. The metal‐based counterparts, nanoscale metal–organic frameworks (nMOFs), are among advanced classes of hybrid nanoparticles, with the fundamental characteristics of pristine MOFs and nanoscale dimensions that enhance their potential for clinical applications. The distinct structure, pore size tunability, easy surface functionalization, large surface area, and porosity enable loading of various therapeutic and imaging agents. In addition, nMOFs demonstrate biocompatibility, multifunctionality, and the relatively labile metal–ligand bonds impart biodegradability. Owing to such excellent properties, nMOFs exhibits biomedically relevant applications as therapeutic cargoes, bioimaging, biosensing and biocatalysts agents. This article elucidates the advantages of nMOFs over other existing nanocarriers (e.g., organic and inorganic) and focuses on new insights of synthesis, design strategies with surface modification techniques for hybrid material development. The biomedical applications with futuristic approach are discussed with relevant examples in detail to inspire further exploration of nMOFs as biomedically relevant agents with great market potential in biomedical sciences.

Self-Assembly of Amorphous 2D Polymer Nanodiscs with Tuneable Size, pH-Responsive Degradation and Controlled Drug Release.

Amphiphilic bottlebrush block copolymers (BBCs) with tadpole-like, coil-rod architecture can be used to self-assemble into functional polymer nanodiscs directly in water. The hydrophobic segments of the BBC were tuned via the ratio of ethoxy-ethyl glycidyl ether (EE) to tetrahydropyranyl glycidyl ether (TP) within the grafted polymer sidechains. In turn, this variation controlled the sizes, pH-responsiveness, and drug loading capacity of the self-assembled nanodiscs. Notably, as EE exhibited faster hydrolysis than TP, the nanodiscs featured variable degradation rates under mild acidic conditions, aiding small molecule release and time-dependent and complete degradation of discs into fully water-soluble copolymers. The nanodiscs demonstrated biocompatibility and cellular uptake by breast cancer cells, underscoring their potential development into drug delivery systems.

Covalent organic frameworks for metal ion separation: Nanoarchitectonics, mechanisms, applications, and future perspectives.

Covalent organic frameworks (COFs) are a class of porous crystalline materials with high surface areas, tunable pore sizes, and customizable surface chemistry, making them ideal for selective metal ion separation. This review explores the nanoarchitectonics, mechanisms, and applications of COFs in metal ion separation. We highlight the diverse bonding types (e.g., imine, boronic ester) and topologies (2D and 3D) that enable precise separation for alkali, alkaline earth, transition, and precious metals. The influence of COFs' pore characteristics, such as surface area, pore size, and distribution, on their adsorption capacity and selectivity is discussed. Additionally, surface functionalization enhances ion adsorption through electrostatic, coordination, and polarity interactions. Despite significant progress, challenges remain, including optimizing functional design for complex metal systems, improving material stability, and developing cost-effective synthesis methods. COFs also show promise in energy material recovery, biomedical diagnostics, and environmental remediation. Combining COFs with other separation technologies can enhance performance, and integrating AI and robotics in COF design may address current limitations, enabling broader industrial and environmental applications.

Environmental applications of metal-organic framework-based three-dimensional macrostructures: a review.

Metal-organic frameworks (MOFs) hold considerable promise for environmental remediation owing to their exceptional performance and distinctive structure. Nonetheless, the practical implementation of MOFs encounters persistent technical hurdles, notably susceptibility to loss, challenging recovery, and potential environmental toxicity arising from the fragility, insolubility, and poor processability of MOFs. MOF-based three-dimensional macrostructures (3DMs) inherit the advantageous attributes of the original MOFs, such as ultra-high specific surface area, tunable pore size, and customizable structure, while also incorporating the intriguing characteristics of bulk materials, including hierarchical structure, facile manipulation, and structural flexibility. Consequently, they exhibit rapid mass transfer and exceptional practicality, offering extensive potential applications in environmental remediation. This review presents a comprehensive overview of recent advancements in utilizing MOF-based 3DMs for environmental remediation, encompassing their fascinating characteristics, preparation strategies, and characterization methods, and highlighting their exceptional performance in pollutant adsorption, catalysis, and detection. Furthermore, existing challenges and prospects are presented to advance the utilization of MOF-based materials across various domains, particularly in environmental remediation.

Intelligent Optimization Design Framework for Alternating Current Pulse Modulation Electrohydrodynamic Printing Process Parameters.

To achieve efficient size tuning of printed microstructures on insulating substrates, an integrated process parameter intelligent optimization design framework for alternating current pulse modulation electrohydrodynamic (AC-EHD) printing is proposed for the first time. The framework is comprised of two stages: the construction of a prediction model and the acquisition of process parameters. The first stage employs the elk herd optimizer(EHO)-artificial neural network(ANN) to establish a mapping relationship between printing process parameters and the size of deposited droplets. The analysis of the prediction performance of the EHO-ANN model across various datasets reveals that the model exhibits commendable accuracy and robustness in predicting printed droplet size. In the second stage, the process parameters of AC-EHD printing are intelligently determined by utilizing the error between the model output and the desired droplet size as the fitness value for EHO. By comparing three sets of experimental cases with varying droplet sizes, it is observed that the actual printed droplet sizes closely align with the desired values, thus validating the effectiveness of this framework. The framework proposed in this paper mitigates the time and material wastage caused by adjusting AC-EHD printing process parameters on insulating substrates, thereby significantly enhancing the usability of the technology.

Enhanced performance of UiO-66 for supercapacitor applications through oxidation via the Hummers' method.

Supercapacitors (SCs) are gaining attention in energy storage due to their high-power density, rapid charge/discharge ability, and long life cycle. Improving these features relies on developing advanced electrode materials with better energy storage properties. This study explores UiO-66, a zirconium-based metal-organic framework (MOF), which offers advantages like a large surface area, tunable pore sizes, and stability. However, its poor electrical conductivity limits its use in supercapacitors. Herein, we applied the Hummers' method to oxidize UiO-66, creating an oxidized form, H-UiO-66, with enhanced conductivity. This material was characterized by various techniques, including SEM-EDX, XRD, XPS, FTIR, and BET analysis, while electrochemical tests (GCD, CV, and EIS) confirmed a significant improvement in specific capacitance-82.8 F g-1 for H-UiO-66 versus 0.18 F g-1 for pristine UiO-66 at 1 mA. These improvements stem from increased conductivity and electrochemical activity due to UiO-66 graphitization, highlighting the Hummers' method's effectiveness in transforming UiO-66 into a viable supercapacitor material.

Uniform single-crystal mesoporous metal-organic frameworks.

The synthesis of mesoporous metal-organic frameworks (meso-MOFs) is desirable as these materials can be used in various applications. However, owing to the imbalance in structural tension at the micro-scale (MOF crystallization) and the meso-scales (assembly of micelles with MOF subunits), the formation of single-crystal meso-MOFs is challenging. Here we report the preparation of uniform single-crystal meso-MOF nanoparticles with ordered mesopore channels in microporous frameworks with definite arrangements, through a cooperative assembly method co-mediated by strong and weak acids. These nanoparticles feature a truncated octahedron shape with variable size and well-defined two-dimensional hexagonally structured (p6mm) columnar mesopores. Notably, the match between the crystallization kinetics of MOFs and the assembly kinetics of micelles is critical for forming the single-crystal meso-MOFs. On the basis of this strategy, we have constructed a library of meso-MOFs with tunable large pore sizes, controllable mesophases, various morphologies and multivariate components.

Tunable Bicontinuous Macroporous Cell Culture Scaffolds via Kinetically Controlled Phase Separation.

3D scaffolds enable biological investigations with a more natural cell conformation. However, the porosity of synthetic hydrogels is often limited to the nanometer scale, which confines the movement of 3D encapsulated cells and restricts dynamic cell processes. Precise control of hydrogel porosity across length scales remains a challenge and the development of porous materials that allow cell infiltration, spreading, and migration in a manner more similar to natural ECM environments is desirable. Here, a straightforward and reliable method is presented for generating kinetically-controlled macroporous biomaterials using liquid-liquid phase separation between poly(ethylene glycol) (PEG) and dextran. Photopolymerization-induced phase separation resulted in macroporous hydrogels with tunable pore size. Varying light intensity and hydrogel composition controlled polymerization kinetics, time to percolation, and complete gelation, which defined the average pore diameter (Ø = 1-200 µm) and final gel stiffness of the formed hydrogels. Critically, for biological applications, macroporous hydrogels are prepared from aqueous polymer solutions at physiological pH and temperature using visible light, allowing for direct cell encapsulation. Human dermal fibroblasts in a range of macroporous gels are encapsulated with different pore sizes. Porosity improved cell spreading with respect to bulk gels and allowed migration in the porous biomaterials.

Synthesis of shape-tunable PbZrTiO3 nanocrystals with lattice variations for piezoelectric energy harvesting and human motion detection.

PbZr0.7Ti0.3O3 cubes with tunable sizes and cuboids have been hydrothermally synthesized. PbZrTiO3 cubes with three different Zr : Ti atomic percentages were also prepared. Analysis of synchrotron X-ray diffraction (XRD) patterns reveals the presence of two lattice components for these samples. Fast Fourier Transform (FFT) processing of high-resolution transmission electron microscopy (HR-TEM) images shows discernible lattice spot differences between the inner bulk and surface layer region for a PbZr0.7Ti0.3O3 cube, while a cuboid has distinct lattice spot deviations. The lattice variations yield different dielectric constant numbers for these two samples, despite being bound by the same crystal faces. The PbZrTiO3 crystals give size- and composition-dependent band gaps. Cuboids show notably larger piezoelectric and ferroelectric responses than cubes. Piezoelectric nanogenerators (PENGs) containing 30 wt% cuboids produce the highest open-circuit voltage of 20.36 V and short-circuit current of 2300 nA. The PENGs harvest energy through bending/releasing cycles to power devices and show photothermal pyroelectric activity. Moreover, a single 30 wt% cuboid PENG device integrated into a shoe insole can deliver an impressive 96.8% accuracy for human motion detection using a machine learning approach. This work illustrates that considerable lattice variation through crystal shape control is effective in enhancing material properties.

Self-assembly processes of 2D Au(I)-S(CH2)2COOH lamellae.

Solving the assembled structure of Au(I)-thiolate linear coordination polymers has been a challenging task as they generally lack good crystallinity. This has prevented the elucidation of their assembly processes at the molecular level. In this paper, selected area electron diffraction (SAED) patterns of two-dimensional (2D) Au(I)-S(CH2)2COOH (Au(I)-MPA) lamellae are obtained by applying cryogenic transmission electron microscopy. The SAED patterns allow to propose a packing mode of Au(I)-MPA chains in the 2D structure by comparison with the crystal structure of Ag(I)-MPA solved from powder X-ray diffraction. Then, multi-step self-assembly processes to 2D lamellae via the aggregation and crystallization of an intermediate of 1D pre-assemblies are disclosed, which explains the difficulty in synthesize their large single crystals. Based on these results, 2D Au(I)-MPA lamellae with tunable sizes and degrees of crystallinity are synthesized by kinetic control of solvent composition and temperature.

Size-controlled antimicrobial peptide drug delivery vehicles through complex coacervation.

Due to the escalating threat of the pathogens' capability of quick adaptation to antibiotics, finding new alternatives is crucial. Although antimicrobial peptides (AMPs) are highly potent and effective, their therapeutic use is limited' as they are prone to enzymatic degradation, are cytotoxic and have low retention. To overcome these challenges, we investigate the complexation of the cationic AMP colistin with diblock copolymers poly(ethylene oxide)-b-poly(methacrylic acid) (PEO-b-PMAA) forming colistin-complex coacervate core micelles (colistin-C3Ms). We present long-term stable kinetically controlled colistin-C3Ms that can be prepared from several block lengths of PEO-b-PMAA polymers, where the polymerisation degree governs the overall micellar size. To achieve precise control over size and polydispersity, which are crucial for drug delivery applications, we investigate the hybridisation of PEO-b-PMAA polymers with varying chain lengths or PMAA homopolymers in ternary complex coacervation systems with colistin. This results in size-tunable colistin-C3Ms, ranging, depending on the mixing ratios, from micellar sizes of 26 nm to 100 nm. With size tunability at rather narrow size distributions and high stability, ternary colistin-C3Ms offer potential advancements in C3M drug delivery, paving the way for more effective and targeted treatments for bacterial infections in precision medicine.