Nanogels and Microgels: From Model Colloids to Applications, Recent Developments, and Future Trends

Design of enzyme immobilized zwitterionic copolymer nanogels and its size effect on electrochemical reaction

For enzyme-based electrochemical devices, an improvement in electron transfer between the enzyme and electrode is important. Thus, we developed a nano-scaled hydrogel that includes an electron mediator and enzyme to realize nano-sized effects that enhance the functions. Three different chain lengths (short, medium, and long) of copolymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and methacrylic acid N-hydroxysuccinimide ester (MNHS; poly(MPC-co-MNHS), PMS) were synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. The PMS nanogels can bind to the amino ferrocene (AFc) of the electron mediator and glucose oxidase (GOD) as a catalyst. The mono-dispersive PMS nanogels approximately 200-250 nm in size bound with AFc were prepared with different polymer chain lengths and amounts of AFc (PMMFcX_Y%, X= 'degree of polymerization, 50, 75, 100' and Y= 'AFc feeding ratio against the amount of NHS group in the polymer chain, 50 %, 100 %'). The size of PMMFcX_Y% could be controlled by changing degree of polymerization or AFc feeding ratio. After the modification of GOD to PMMFcX_Y%, their size increased slightly from the original size (ca. 200-250 nm) to approximately 250-300 nm. The catalytic activity of nanogel in dispersed system was higher than that of microgel, indicating that nanogels could improve glucose transport in hydrogel layer. Compared to the catalytic reaction of the PMMFc 75_50 %-GOD nanogel-modified electrodes with that of microgel modified electrode, the current response was improved by decreasing the nanogel size, as evaluated by electrochemical measurements. These results revealed that the smaller nanogels could improve both glucose transport and electron transfer via mediator by smaller size, resulting higher efficiency of enzyme immobilized electrode.

Dual cryoprotection of gelatin-tea polyphenol microgels on surimi by targeting for ice inhibition and component stabilization

In this study, the gelatine-polyphenol microgels with dual cryoprotective roles were constructed by regulating the ratio of gelatin to tea polyphenols (1:50-1:250). The physicochemical attributes, ice recrystallization inhibition ability of microgels, and their dosage effects (1 %, 2.5 % and 4 %, w/w) on surimi were investigated. The results indicated that increased gelatin caused the reduced size and enhanced viscosity of microgels. Except for high viscosity and antioxidant activity, the GP-5 group also showed great IRI ability with minimum size distribution (125-214 μm2) of ice crystals. Furthermore, 2.5 G group and S group had a comparable TVB-N (3.81, 4.34 mg/100 g), TBARS (1.18, 1.32 mg/kg), sulfhydryl contents (29.52, 25.48 μmol/g) and Ca2+-ATPase activity (0.44, 0.36 μmolPi/gprot/h). Compared to uneven free water distribution of control group, S and 2.5 G group show more even immobilized-water distribution. Thereafter, the dual cryoprotective functions of microgels in surimi offer valuable insights for the development of effective antifreeze agents.

Optimizing the charge transport in redox-active gels: a computational study

Redox-active polymer gels are promising materials for various applications, such as energy conversion and storage systems, organic electronics, soft-robotics, sensors and others. This is in part due to the remarkable structural tunability of these materials. The gel may adopt different conformations depending on the crosslinking density, solvent temperature and other conditions. These parameters affect its behavior, including the dynamics of the charge transport between the redox groups grafted to the polymer subchains, which is of utmost importance for electrochemical applications. Here, we employed coarse-grained molecular dynamics simulation to investigate the impact of crosslinking, redox group content and solvent quality on both subchain mobility and charge transport speed. In particular, unexpected behavior of the system under the theta-solvent condition was found and analyzed. The obtained results provide useful guidelines to facilitate the best conditions for enhanced "redox induced" conductivity in polymer gels, which would help the development of redox-flow batteries and other electrochemical devices.

FLIM nanoscopy resolves the structure and preferential adsorption in the co-nonsolvency of PNIPAM microgels in methanol-water

Polymer microgels are swollen macromolecular networks with a typical size of hundred of nanometers to several microns that show an extraordinary open and responsive architecture to different external stimuli, being therefore important candidates for nanobiotechnology and nanomedical applications such as biocatalysis, sensing and drug delivery. It is therefore crucial to understand the delicate balance of physical-chemical interactions between the polymer backbone and solvent molecules that to a high extent determine their responsivity. In particular, the co-nonsolvency effect of poly(N-isopropylacrylamide) in aqueous alcohols is highly discussed, and there is a disagreement between molecular dynamics (MD) simulations (from literature) of the preferential adsorption of alcohol on the polymer chains and the values obtained by several empirical methods that mostly probe the bulk solvent properties. It is our contention that the most efficacious method for addressing this problem requires a nanoscopic method that can be combined with spectroscopy and record fluorescence spectra and super-resolved fluorescence lifetime images of microgels labeled covalently with the solvatochromic dye Nile Red. By employing this approach, we could simultaneously resolve the structure of sub-micron size objects in the swollen and in the collapsed state and estimate the solvent composition inside of them in - mixtures for two very different polymer architectures. We found an outstanding agreement between the MD simulations and our results that estimate a co-solvent molar fraction excess of approximately 3 with a very flat profile in the lateral direction of the microgel.

A novel strategy for addressing post-surgical abdominal adhesions: Janus hydrogel

Abdominal adhesions are a frequent complication after abdominal surgery, which can cause significant pain and burden to patients. Despite various treatment options, including surgical intervention and pharmacotherapy, these often fail to consistently and effectively prevent postoperative abdominal adhesions. Janus hydrogel is famous for its asymmetric characteristics, which shows great prospects in the prevention and treatment of abdominal adhesion. This review outlines the preparation methods, mechanisms of action, and key applications of Janus hydrogel in the prevention of postoperative abdominal adhesions. Furthermore, we examine the current limitations of the Janus hydrogel anti-adhesion barrier and explore potential future directions for its development.

Effect of Polymer Network Architecture on Adsorption Kinetics at Liquid-Liquid Interfaces: A Comparison Between Poly(NIPAM-co-AA) Copolymer Microgels and Interpenetrating Network Microgels

Understanding the adsorption features of polymer microgels with different chemical compositions and structures is crucial in studying the mechanisms of respective emulsion stabilization. Specifically, the use of stimuli-responsive particles can introduce new properties and broaden the application range of such complex systems. Recently, we demonstrated that emulsions stabilized by microgels composed of interpenetrating networks (IPNs) of poly-N-isopropylacrylamide (PNIPAM) and polyacrylic acid (PAA) exhibit higher colloidal stability upon heating compared to PNIPAM homopolymer and other relevant PNIPAM-based copolymer counterparts. In the present work, using pendant drop tensiometry, we studied the evolution of water-tetradecane interfacial tension during the adsorption of PNIPAM-PAA IPN particles, comparing them with single-network P-(NIPAM-co-AA) and PNIPAM microgels. The results showed that, despite having the same chemical composition, copolymer particles exhibit completely different adsorption behavior in comparison to other microgel architectures. The observed disparity can be attributed to the nonuniform distribution of charged acrylic acid groups within the P-(NIPAM-co-AA) network obtained through precipitation polymerization. Oppositely, the presence of IPN architecture provides a uniform distribution of different monomers inside respective microgels. Additionally, hydrogen bonding between PNIPAM and PAA subchains appears to reduce the electrostatic energy barrier, enhancing the ability of IPN particles to successfully cover the liquid interface. Overall, our findings confirm the efficiency of using PNIPAM-PAA IPN microgels for the preparation of oil-in-water emulsions and their stability, even when the temperature rises above the lower critical solution temperature of PNIPAM.

Polymer Nano-Carrier-Mediated Gene Delivery: Visualizing and Quantifying DNA Encapsulation Using dSTORM

The success of gene therapy hinges on the effective encapsulation, protection, and compression of genes. These processes deliver therapeutic genes into designated cells for genetic repair, cellular behavior modification, or therapeutic effect induction. However, quantifying the encapsulation efficiency of small molecules of interest like DNA or RNA into delivery carriers remains challenging. This work shows how super-resolution microscopy, specifically direct stochastic optical reconstruction microscopy (dSTORM), can be employed to visualize and measure the quantity of DNA entering a single carrier. Utilizing pNIPAM/bPEI microgels as model nano-carriers to form polyplexes, DNA entry into the carrier is revealed across different charge ratios at temperatures below and above the volume phase transition of the microgel core. The encapsulation efficiency also depends on DNA length and shape. This work demonstrates the uptake of the carrier entity by primary derived macro-phages and showcases the cell viability of the polyplexes. The study shows that dSTORM is a potent tool for fine-tuning and creating polyplex microgel carrier systems with precise size, shape, and loading capacity at the individual particle level. This advancement shall contribute significantly to optimizing gene delivery systems.

Soft and Deformable Thermoresponsive Hollow Rod-Shaped Microgels

Depending on their aspect ratio, rod-shaped particles exhibit a much richer 2D and 3D phase behavior than their spherical counterparts, with additional nematic and smectic phases accompanied by defined orientational ordering. While the phase diagram of colloidal hard rods is extensively explored, little is known about the influence of softness in such systems, partly due to the absence of appropriate model systems. Additionally, investigating higher volume fractions for long rods is usually complicated because non-equilibrium dynamical arrest is likely to precede the formation of more defined states. This has motivated us to develop micrometric rod-like microgels with limited sedimentation that can respond to temperature and reversibly reorganize into defined phases via annealing and seeding procedures. A detailed procedure is presented for synthesizing rod-shaped hollow poly(N-isopropylacrylamide) microgels using micrometric silica rods as sacrificial templates. Their morphological characterization is conducted through a combination of microscopy and light scattering techniques, evidencing the unconstrained swelling of rod-shaped hollow microgels compared to core-shell microgel rods. Different aspects of their assembly in dispersion and at interfaces are further tested to illustrate the opportunities and challenges offered by such systems that combine softness, anisotropy, and thermoresponsivity.

Expression profiling of antimicrobial peptides and immune-related genes in Nile tilapia following Pseudomonas putida infection and nano-titanium dioxide gel exposure

Pseudomonas putida is a virulent bacterium that prompts major losses in fish. Recently, there has been a noticeable direction for utilizing nanomaterials in the aquaculture industry for sustaining fish health and performance. Hence, the present study is the first trial to investigate the antibacterial influence of nano titanium dioxide gel (NTG) as a watery addition for combating P. putida infection in Nile tilapia (Oreochromis niloticus). Further, antioxidant-immune capacity, and gene expression in the spleen including antimicrobial peptides and immune-related genes are assessed. Fish (n = 200; 47.50 ± 1.32 g of body weight) were assigned into four groups for 10 days [control, NTG (0.9 mg/L), P. putida, and NTG + P. putida]. Findings demonstrated that the infection by P. putida induced a decline in antioxidant immune indicators including catalase, glutathione peroxidase, and nitric oxide. Furthermore, a noteworthy rise in lipid peroxide (malondialdehyde), tumor necrosis factor-alpha (TNF-α), and stress indicator (glucose) levels was noticed. P. putida infection induced remarkable alterations in the expression of antimicrobial peptides genes [tilapia piscidin (TP3 and TP4), colony-stimulating factor 1 receptor, hepcidin-2, beta-defensin1, and neutrophil cytosolic factor 4] and immune-relevant genes [transforming growth factor beta, tumor necrosis factor receptor-associated factor 6, TNF-α, interleukins (IL-10 and IL-11)]. Notably, applying NTG regenerated all the negative consequences of P. putida infection. Inclusive, this study underscores the crucial role of NTG as a potent antibacterial and immune-antioxidant agent, highlighting its potential in protecting O. niloticus from P. putida infection and improving immune-antioxidant response.

Capillary-driven self-assembly of soft ellipsoidal microgels at the air-water interface

The adsorption of ellipsoidal colloidal particles on liquid interfaces induces interfacial deformation, resulting in anisotropic interface-mediated interactions and the formation of superstructures. Soft prolate-shaped microgels at the air-water interface offer an ideal model for studying spontaneous capillary-driven self-assembly due to their tunable aspect ratio, controlled functionality, and softness. These microgels consist of a polystyrene core surrounded by a cross-linked, fluorescently labeled poly([Formula: see text]-isopropylmethylacrylamide) shell. By uniaxially stretching the particles embedded in polyvinyl alcohol films, the aspect ratio [Formula: see text] can be finely adjusted. [Formula: see text] was found to vary from 1 to 8.8 as estimated in their swollen conformation at 20 °C from confocal laser scanning microscopy. The spontaneous interfacial self-assembly at the air-water interface is investigated through fluorescence microscopy, theoretical calculations, and computer simulations. A structural transition occurs from a seemingly random assembly for small aspect ratios to compact clusters, which transform into a side-to-side assembly forming long chains for high aspect ratios. The influence of the poly([Formula: see text]-isopropylmethacrylamide) shell on the assembly indicates a significant [Formula: see text]-dependent microgel deformation. This deformation, in turn, determines the average distance between the particles. Consequently, capillary-driven self-assembly of soft anisotropic colloids becomes a powerful mechanism for structuring interfaces and designing microstructured materials.

Nanogels with tailored hydrophobicity and their behavior at air/water interfaces

The interfacial behavior of micro-/nanogels is governed to a large extent by the hydrophobicity of their polymeric network. Prevailing studies to examine this influence mostly rely on external stimuli like temperature or pH to modulate the particle hydrophobicity. Here, a sudden transition between hydrophilic and hydrophobic state prevents systematic and gradual modulation of hydrophobicity. This limits detailed correlations between interfacial behavior and network hydrophobicity. To address this challenge, we introduce a nanogel platform that allows accurate tuning of hydrophobicity on a molecular level. For this, via post-functionalization of active ester-based particles, we prepare poly(N-(2-hydroxypropyl)methacrylamide) (PHPMA) nanogels as a hydrophilic benchmark and introduce gradually varied amounts of hydrophobic propyl or dodecyl moieties to increase the nanogel hydrophobicity. We study the deformation and arrangement of these particles at an air/water interface and correlate the results with quantitative measures for nanogel hydrophobicity. We observe that increasing hydrophobicity of nanogels, either by increasing the hydrophobic moiety ratio or the alkyl chain length, leads to decreased particle deformability and aggregation of an interfacially-adsorbed monolayer. Contrary to what may be intuitively assumed, these changes are not gradual, but rather occur suddenly above a threshold in hydrophobicity. Our study further shows that the effect of hydrophobicity affects the nanogel properties differently in bulk and when adsorbed at liquid interfaces. Thus, this study establishes the transition of interfacial behavior between soft gel-like particles to a solid spherical morphology triggered by the increase in hydrophobicity.

NIPAm Microgels Synthesised in Water: Tailored Control of Particles' Size and Thermoresponsive Properties

Microgels, combining the properties of hydrogels and microparticles, are emerging as versatile materials for varied applications such as drug delivery and sensing, although the precise control of particle size remains a challenge. Advances in synthetic methodologies have provided new tools for tailoring of properties, however costs and scalability of the processes remains a limitation. We report here the water-based synthesis of a library of N-isopropylacrylamide-based microgels covalently crosslinked with varying contents of N,N'-methylenebisacrylamide. The results highlight the versatility of water as a synthetic medium, which yields large and monodisperse microgels, with excellent control over size. Dynamic light scattering data demonstrate that by increasing the total monomer concentration from 1 to 3 wt%, the particle size is increased by up to 4.9-fold. Crosslinker content allows fine-tuning of microgel size, with greater relevance for functionalised microgels. Functional co-monomers such as N-(3-aminopropyl)methacrylamide hydrochloride and N-(hydroxymethyl)acrylamide are shown to influence size and thermoresponsive behaviour, with hydrogen-bonding monomers reducing particle size and increasing the volume phase transition temperature by 2 °C. Positively charged monomers show a size reduction upon heating but provide colloidal stability at temperatures up to 60 °C. These findings emphasize the importance of tailoring synthetic conditions and formulations to optimize microgel properties for specific applications.

Strong self-association of chitosan microgels at interface mediated high stabilities in Pickering emulsion

The spontaneous self-organization of naturally-occurring polysaccharide particles into a thick and robust gel network at interface in Pickering emulsion is challenging. Inspired by the phenomenon that chitosan microgels (CSMs) with a certain size could self-associate into a solidified gel phase upon freezing, here we tentatively used CSMs to construct a highly-stable Pickering emulsion. CSMs can form a stable Langmuir's layer at the water/oil interface through the network deformation and re-arrangement of dangling chains, while the subsequent negative polymer coating can avoid the bridging resulting from the cross-association for CSMs on different emulsion droplets upon freezing. The experimental results indicated that the emulsion showed excellent features, including the wide pH range stability (3-12), long-term storage stability (> 3 months), thermal stability (121 °C, 30 min). Moreover, CSMs could self-associate into a reliable gel layer around the oil droplet in freezing, leading to the better freeze-thaw stability (1-3 cycles). The negative coating not only facilitates the formation of interfacial gel network around each emulsion droplet, but also produces huge steric hindrance and electrostatic repulsion to suppress the coalescence. This work provides a different way to modulate the interfacial structure, thus developing a more stable polysaccharide-based Pickering emulsion.

Microgels with controlled network topologies by photocrosslinking-assisted continuous precipitation polymerization

In this study, we present a new synthesis methodology based on photo-crosslinking-assisted continuous precipitation polymerization which allows controlling the distribution of crosslinks in microgels. In our approach we substituted conventional crosslinking agent by a comonomer carrying photo-crosslinkable 4-oxocyclopent-2-en-1-yl group. Microgel size, morphology, distribution of crosslinks and packing density of the polymer chains are studied as a function of retention time (Rt) in the flow reactor. Dynamic and static light scattering (DLS and SLS) as well as small angle X-ray scattering (SAXS) proved an excellent level of control over the distribution of crosslinks in microgels during the polymerization process. These results were confirmed by atomic force microscopy (AFM), indicating a difference in microgel stiffness and arrangement of the polymer network as resulting from increased Rt.

Drying of Soft Colloidal Films

Thin films made of deformable micro- and nano-units, such as biological membranes, polymer interfaces, and particle-laden liquid surfaces, exhibit a complex behavior during drying, with consequences for various applications like wound healing, coating technologies, and additive manufacturing. Studying the drying dynamics and structural changes of soft colloidal films thus holds the potential to yield valuable insights to achieve improvements for applications. In this study, interfacial monolayers of core-shell (CS) microgels with varying degrees of softness are employed as model systems and to investigate their drying behavior on differently modified solid substrates (hydrophobic vs hydrophilic). By leveraging video microscopy, particle tracking, and thin film interference, this study shed light on the interplay between microgel adhesion to solid surfaces and the immersion capillary forces that arise in the thin liquid film. It is discovered that a dried replica of the interfacial microstructure can be more accurately achieved on a hydrophobic substrate relative to a hydrophilic one, particularly when employing softer colloids as opposed to harder counterparts. These observations are qualitatively supported by experiments with a thin film pressure balance which allows mimicking and controlling the drying process and by computer simulations with coarse-grained models.

Fighting fibrin with fibrin: Vancomycin delivery into coagulase-mediated Staphylococcus aureus biofilms via fibrin-based nanoparticle binding

Staphylococcus aureus skin and soft tissue infection is a common ailment placing a large burden upon global healthcare infrastructure. These bacteria are growing increasingly recalcitrant to frontline antimicrobial therapeutics like vancomycin due to the prevalence of variant populations such as methicillin-resistant and vancomycin-resistant strains, and there is currently a dearth of novel antibiotics in production. Additionally, S. aureus has the capacity to hijack the host clotting machinery to generate fibrin-based biofilms that confer protection from host antimicrobial mechanisms and antibiotic-based therapies, enabling immune system evasion and significantly reducing antimicrobial efficacy. Emphasis is being placed on improving the effectiveness of therapeutics that are already commercially available through various means. Fibrin-based nanoparticles (FBNs) were developed and found to interact with S. aureus through the clumping factor A (ClfA) fibrinogen receptor and directly integrate into the biofilm matrix. FBNs loaded with antimicrobials such as vancomycin enabled a targeted and sustained release of antibiotic that increased drug contact time and reduced the therapeutic dose required for eradicating the bacteria, both in vitro and in vivo. Collectively, these findings suggest that FBN-antibiotic delivery may be a novel and potent therapeutic tool for the treatment of S. aureus biofilm infections.

Machine-learning-assisted prediction of the size of microgels prepared by aqueous precipitation polymerization

The size of soft colloids (microgels) is essential; however, control over their size has typically been established empirically. Herein, we report a linear-regression model that can predict microgel size using a machine learning method, sparse modeling for small data, which enables the determination of the synthesis conditions for target-sized microgels.

Nanoscopic visualization of microgel-immobilized cytochrome P450 enzymes and their local activity

Microgels provide a controlled microenvironment for enzymes, protecting them from degradation while enhancing stability and activity. Their customizable and biocompatible structure allows for targeted delivery and controlled release, making them ideal for transporting and preserving enzyme function in various applications. For such applications, detailed knowledge of the distribution of enzymes and their activity within the microgels is essential. We present a combination of different localization-based super-resolution fluorescence microscopy measurements to localise single Cytochrome P450 BM3 enzymes and compare their local catalytic activity.

Computer Simulations of Responsive Nanogels at Lipid Membrane

The swelling and collapse of responsive nanogels on a planar lipid bilayer are studied by means of mesoscopic computer simulations. The effects of molecular weight, cross-linking density, and adhesion strength are examined. The conditions for collapse-mediated engulfing by the bilayer are found. In particular, the results show that at low hydrophobicity level the increase in the nanogel softness decreases the engulfing rate. On the contrary, for stronger hydrophobicity level the trend changes to the opposite one. At the same time, when the cross-linking density is too low or the adhesion strength is too high the nanogel deformation at the membrane suppresses the engulfing regardless of the network swelling ratio. Finally, for comparative reasons, the behavior of the nanogels is also studied at the solid surface. These results may be useful in the design of soft particles capable of tuning of their elasticity and porosity for successful intracellular drug delivery.

Design of multi-responsive and actuating microgels toward on-demand drug release

Multifunctional colloidal microgels that exhibit stimuli-responsive behaviour and excellent biocompatibility have attracted particular attention for developing functional compartmentalized networks. Herein, a series of stimuli-responsive microgels (M0, M1, and M2) were designed through the copolymerization of di(ethylene glycol) methyl ether methacrylate (DEGMA) and methacrylic acid (MAA) monomers using hydroxy ethyl methacrylate-coupled azobenzene (HEMA-Az) and ethylene glycol dimetharylate (EGDMA) as crosslinkers. The behaviour of the microgels in response to temperature, pH, and light was thoroughly investigated using spectroscopic, microscopic, and light-scattering techniques. Interestingly, the microgels deswelled with an increase in temperature, decrease in pH, and under the irradiation of UV light. Such a reversible swelling/deswelling behaviour was exploited for microgel M2, which showed better photoactuation at pH 5 with a higher fluid pumping velocity. The actuating microgel M2 was optimized for loading the drug ciprofloxacin (Cf) to study its release at different temperature, pH, and light conditions. Microgel M2 exhibited photoresponsive Cf release at pH 5 and 37 °C, demonstrating its potential for application in on-demand drug release.

Crosslinked polymeric networks of TiO2-polymer composites: a comprehensive review

The crosslinked network of TiO2-organic polymer composites has gained considerable attention over the past few years. The low band gap of TiO2 particles and the stimuli-responsive behavior of organic polymers make these composites suitable for a wide range of applications in biomedicine, environmental fields, and catalysis. Diverse morphologies and structures of TiO2-polymer composites (TPCs) are documented in the available literature, where the specific architecture of these composites intensely influences their efficiency in various applications. Consequently, a particular shaped TPC is carefully designed to suit specific purposes. This comprehensive review describes the classifications, synthetic approaches, characterizations, and applications of TiO2 nanoparticles decorated in crosslinked organic polymers. It delves into the biomedical, catalytic, adsorption, and environmental applications of these TiO2-polymer composites. The review takes a tutorial approach, systematically exploring and clarifying the applications of TiO2-polymer composites, offering a comprehensive understanding of their different capabilities and uses.

Revisiting the density profile of the fuzzy sphere model for microgel colloids

Common neutral polymer microgels exhibit an inhomogeneous density profile with a gradual decay that is commonly described using the fuzzy sphere model. The model is based on the idea of convolving the collapsed solid sphere profile with a Gaussian to describe inhomogeneous swelling of the microgel in a good solvent. Here we show that the corresponding density profile in real space used in several recent works - such as in super-resolution microscopy - is different from the fuzzy sphere model, and we explain how to correctly transition between reciprocal space modelling to real space. Our work aims to clarify the application of the model so that errors can be avoided in the future. Our discussion is also crucial when comparing alternative real-space models for the density profile with the established fuzzy sphere model.

Remarkable Stability of Glutathione-Based Supramolecular Gel in the Presence of Oxidative Stress from Hydrogen Peroxide

Low molecular weight 7-methoxy-3-(p-nitrophenyl)iminocoumarin (MNI) with donor and acceptor groups has been synthesized. The molecule shows typical π-stacking geometry in the crystal structure. In this study, MNI, an achiral small organic molecule, forms a nanostructured supramolecular gel along with a short peptide sequence glutathione (GSH). The self-assembly of the achiral organic coumarin component and chiral biomolecule produces a chiral gel with helical fiber structures. Interestingly, the helicities of chiral gels are controlled by the solvent ratio, where MNI in DMSO and GSH in water has been used. Variation of the solvent ratio from 6:4 to 1:9 for DMSO:H2O results in six gels (4, 5, 6, 7, 8 and 9), where the gel numbers signify the water content ratio. FE-SEM analysis shows gel fibers with right-handed helical structures, which have been further confirmed by circular dichroism (CD) with notable helicity in 4 to 6. This is the first report of controlled chiral helical nanostructured supramolecular gel formation by a solvent mixture with an organic small molecule and biomolecule. Interestingly, storage modulus (G') initially decreases from 4 to 6 and further increases up to 9. An opposite strain (%) trend was observed among these six gels. These unusual solvent-dependent gel properties have been further applied to monitor the stability of the gels in the presence of hydrogen peroxide (H2O2), which converts GSH to oxidized glutathione (GSSG) in general. The oxidative stress from H2O2 disrupts 4 to 6 gels, and precipitation occurs. It is noteworthy to mention that GSSG alone cannot form a gel with the MNI molecule and forms a precipitate. Remarkably, on the other hand, 7 to 9 remain as strong gels even after H2O2 treatment. Among all six gels, 9 shows extraordinary stability of gels even after H2O2 treatment.

Phase behavior of binary mixtures of hollow and regular microgels

Soft colloids are widely used to study glass transition, aging and jamming. A high size polydispersity is typically introduced in these systems to avoid crystal formation. Here, we use binary mixtures of hollow and regular microgels with comparable sizes to inhibit crystallization. The phase behavior of the mixture is probed as a function of the number fraction of hollow microgels and characterized by small-angle X-ray scattering. Molecular dynamic simulations are used to extract the particle-particle pair potential and obtain insight on their deformation. The results suggest that the high deformability of the hollow microgels offers an alternative route to maximize the entropy without crystal formation.

Modulating the conformation of microgels by complexation with inorganic nanoparticles

HYPOTHESIS

The complexation of microgels with rigid nanoparticles is an effective way to impart novel properties and functions to the resulting hybrid particles for applications such as in optics, catalysis, or for the stabilization of foams/emulsions. The nanoparticles affect the conformation of the polymer network, both in bulk aqueous environments and when the microgels are adsorbed at a fluid interface, in a non-trivial manner by modulating the microgel size, stiffness and apparent contact angle.

EXPERIMENTS

Here, we provide a detailed investigation, using light scattering, in-situ atomic force microscopy and nano-indentation experiments, of the interaction between poly(N-isopropylacrylamide) microgels and hydrophobized silica nanoparticles after mixing in aqueous suspension to shed light on the network reorganization upon nanoparticle incorporation.

FINDINGS

The addition of nanoparticles decreases the microgels' bulk swelling and thermal response. When adsorbed at an oil-water interface, a higher ratio of nanoparticles influences the microgel's stiffness as well as their hydrophobic/hydrophilic character by increasing their effective contact angle, consequently modulating the monolayer response upon interfacial compression. Overall, these results provide fundamental understanding on the complex conformation of hybrid microgels in different environments and give inspiration to design new materials where the combination of a soft polymer network and nanoparticles might result in additional functionalities.

Advances in the Development of Granular Microporous Injectable Hydrogels with Non-spherical Microgels and Their Applications in Tissue Regeneration

Granular microporous hydrogels are emerging as effective biomaterial scaffolds for tissue engineering due to their improved characteristics compared to traditional nanoporous hydrogels, which better promote cell viability, cell migration, cellular/tissue infiltration, and tissue regeneration. Recent advances have resulted in the development of granular hydrogels made of non-spherical microgels, which compared to those made of spherical microgels have higher macroporosity, more stable mechanical properties, and better ability to guide the alignment and differentiation of cells in anisotropic tissue. The development of these hydrogels as an emerging research area is attracting increasing interest in regenerative medicine. This review first summarizes the fabrication techniques available for non-spherical microgels with different aspect-ratios. Then, it introduces the development of granular microporous hydrogels made of non-spherical microgels, their physicochemical characteristics, and their applications in tissue regeneration. The limitations and future outlook of research on microporous granular hydrogels are also critically discussed.

Rational Designing Microenvironment of Gas-Diffusion Electrodes via Microgel-Augmented CO2 Availability for High-Rate and Selective CO2 Electroreduction to Ethylene

Efficient electrochemical CO2 reduction reaction (CO2RR) requires advanced gas-diffusion electrodes (GDEs) with tunned microenvironment to overcome low CO2 availability in the vicinity of catalyst layer. Herein, for the first time, pyridine-containing microgels-augmented CO2 availability is presented in Cu2O-based GDE for high-rate CO2 reduction to ethylene, owing to the presence of CO2-phil microgels with amine moieties. Microgels as three-dimensional polymer networks act as CO2 micro-reservoirs to engineer the GDE microenvironment and boost local CO2 availability. The superior ethylene production performance of the GDE modified by 4-vinyl pyridine microgels, as compared with the GDE with diethylaminoethyl methacrylate microgels, indicates the bifunctional effect of pyridine-based microgels to enhance CO2 availability, and electrocatalytic CO2 reduction. While the Faradaic efficiency (FE) of ethylene without microgels was capped at 43% at 300 mA cm-2, GDE with the pyridine microgels showed 56% FE of ethylene at 700 mA cm-2. A similar trend was observed in zero-gap design, and GDEs showed 58% FE of ethylene at -4.0 cell voltage (>350 mA cm-2 current density), resulting in over 2-fold improvement in ethylene production. This study showcases the use of CO2-phil microgels for a higher rate of CO2RR-to-C2+, opening an avenue for several other microgels for more selective and efficient CO2 electrolysis.

Measurable structure factors of dense dispersions containing polydisperse optically inhomogeneous particles

Here, it is investigated how optical properties of single scatterers in interacting multi-particle systems influence measurable structure factors. Both particles with linear gradients of their scattering length density and core-shell structures evoke characteristic deviations between the weighted sum 〈S(Q)〉 of partial structure factors in a multi-component system and experimentally accessible measurable structure factors S M(Q). While 〈S(Q)〉 contains only the structural information of self-organizing systems, S M(Q) is additionally influenced by the optical properties of their constituents, resulting in features such as changing amplitudes, additional peaks in the low-wavevector region or splitting of higher-order maxima, which are not related to structural reasons. It is shown that these effects can be systematically categorized according to the qualitative behaviour of the form factor in the Guinier region, which enables assessing the suitability of experimentally obtained structure factors to genuinely represent the microstructure of complex systems free from any particular model assumption. Hence, a careful data analysis regarding size distribution and optical properties of single scatterers is mandatory to avoid a misinterpretation of measurable structure factors.

A Novel Approach for the Synthesis of Responsive Core-Shell Nanogels with a Poly(N-Isopropylacrylamide) Core and a Controlled Polyamine Shell

Microgel particles can play a key role, e.g., in drug delivery systems, tissue engineering, advanced (bio)sensors or (bio)catalysis. Amine-functionalized microgels are particularly interesting in many applications since they can provide pH responsiveness, chemical functionalities for, e.g., bioconjugation, unique binding characteristics for pollutants and interactions with cell surfaces. Since the incorporation of amine functionalities in controlled amounts with predefined architectures is still a challenge, here, we present a novel method for the synthesis of responsive core-shell nanogels (dh < 100 nm) with a poly(N-isopropylacrylamide) (pNIPAm) core and a polyamine shell. To achieve this goal, a surface-functionalized pNIPAm nanogel was first prepared in a semi-batch precipitation polymerization reaction. Surface functionalization was achieved by adding acrylic acid to the reaction mixture in the final stage of the precipitation polymerization. Under these conditions, the carboxyl functionalities were confined to the outer shell of the nanogel particles, preserving the core's temperature-responsive behavior and providing reactive functionalities on the nanogel surface. The polyamine shell was prepared by the chemical coupling of polyethyleneimine to the nanogel's carboxyl functionalities using a water-soluble carbodiimide (EDC) to facilitate the coupling reaction. The efficiency of the coupling was assessed by varying the EDC concentration and reaction temperature. The molecular weight of PEI was also varied in a wide range (Mw = 0.6 to 750 kDa), and we found that it had a profound effect on how many polyamine repeat units could be immobilized in the nanogel shell. The swelling and the electrophoretic mobility of the prepared core-shell nanogels were also studied as a function of pH and temperature, demonstrating the successful formation of the polyamine shell on the nanogel core and its effect on the nanogel characteristics. This study provides a general framework for the controlled synthesis of core-shell nanogels with tunable surface properties, which can be applied in many potential applications.

Moisture changes inside hydrogel particles during their drying process investigated with fluorescence lifetime imaging

The properties of hydrogels and microgels, i.e. hydrogel particles, depend strongly on their water content. Based on our previously developed method to access the local water content in microgels, we performed fluorescence lifetime microscopy measurements at different stages of drying poly(N-isopropylacrylamide) (PNIPAM) microgels under ambient conditions. For this purpose, the red-emitting dye ATTO 655 was covalently attached to the microgels. Its emission is quenched by water molecules due to an energy transfer from the first excited state of the dye to a vibrational level of the water molecules. The quenching constant or, equivalently, the fluorescence lifetime, gives direct access to the local water concentration. We measured the fluorescence lifetime after spin-coating, reswelling and at different times of subsequent drying to follow the changes of water content during this process. We found that the microgels are not totally dry after spin coating, but drying them to their equilibrium moisture under ambient temperature and humidity conditions requires several hours. Additionally, we determined the moisture inside microgels in equilibrium at different air humidities. In summary, the method allows for a detailed investigation of the moisture inside hydrogels and gives straight-forward access to in situ and operando measurements of hydrogel systems.

Nonequilibrium relaxation of soft responsive colloids

Stimuli-responsive macromolecules display large conformational changes during their dynamics, sometimes switching between states. Such a multi-stability is useful for the development of soft functional materials. Here, we introduce a mean-field dynamical density functional theory for a model of responsive colloids to study the nonequilibrium dynamics of a colloidal dispersion in time-dependent external fields, with a focus on the coupling of translational and conformational dynamics during their relaxation. Specifically, we consider soft Gaussian particles with a bimodal size distribution between two confining walls with time-dependent (switching-on and off) external gravitational and osmotic fields. We find a rich relaxation behavior of the systems in excellent agreement with particle-based Brownian dynamics computer simulations. In particular, we find time-asymmetric relaxations of integrated observables (wall pressures, mean size, and liquid center-of-mass) for activation/deactivation of external potentials, respectively, which are tunable by the ratio of translational and conformational diffusion time scales. Our work thus paves the way for studying the nonequilibrium relaxation dynamics of complex soft matter with multiple degrees of freedom and hierarchical relaxations.

Nitrilotriacetic Acid Functionalized Microgels for Efficient Immobilization of Hyaluronan Synthase

Enzymes play a vital role in synthesizing complex biological molecules like hyaluronic acid (HA). Immobilizing enzymes on support materials is essential for their efficient use and reuse in multiple cycles. Microgels, composed of cross-linked, highly swollen polymer networks, are ideal for enzyme uptake owing to their high porosity. This study demonstrates the immobilization of His6-tagged hyaluronan synthase from Pasteurella multocida (PmHAS) onto nitrilotriacetic acid functionalized microgels using different bivalent ions (Ni2+, Co2+, Mn2+, Mg2+, and Fe2+) via metal affinity binding. The results indicate that using Ni2+ yields the microgels with the highest enzyme uptake and HA formation. The immobilized PmHAS enables repetitive enzymatic production, producing high molecular weight HAs with decreasing dispersities in each step. Furthermore, the highest reported yield of HA with high molecular weight for immobilized PmHAS is achieved. This system establishes a foundation for continuous HA formation, with future works potentially enhancing PmHAS stability through protein engineering.

3D visualization reveals the cooling rate dependent crystallization near a wall in dense microgel systems

Controlled crystallization, melting and vitrification are important fundamental processes in nature and technology. However, the microscopic details of these fundamental phenomena still lack understanding, in particular how the cooling rate and presence of a wall influence the crystal nucleation and glass formation. Thermoresponsive microgels provide the possibility to study phase transitions at the single-particle level, owing to the ability to tune the particle size with temperature. In this study, we employ composite microgels consisting of a hard core and a crosslinked poly(N-isopropyl acrylamide-co-methacrylic acid) shell to study the crystallization of dense suspensions of soft colloids near a wall using confocal microscopy. We investigate the effect of the cooling rate on the fluid-to-solid transition close to the sample wall. The structures formed during cooling range from glassy in the case of a rapid temperature quench to crystalline when a slow cooling rate is used. Detailed analysis of the final structure reveals that the cooling rate also sets the degree of alignment of the crystal domains with the wall as a result of a balance between homogeneous and heterogeneous crystal nucleation. The results presented here yield valuable insight into the microscopic details of temperature-controlled crystallization near a wall. This understanding will help pave the way towards optimal crystallization conditions for microgel applications.

Nanoliposomes a future based delivery vehicle of cyanidin-3-O-glucoside against major chronic disease

BACKGROUND

Cyanidin-3-O-glucoside (C3G), is an anthocyanin mainly found in berries, and can also be produced by microorganisms. It has been traditionally used as a natural coloring agent for decades. Recently, it has been investigated for its high antioxidant activity and anti-cancer attributes. C3G has low bioavailability and is sensitive to oxidation and gastric pH; therefore, it is encapsulated in nanoliposomes to enhance its bio-availability, targeted delivery- and efficacy against chronic disease.

SCOPE AND APPROACH

In this review, the role of C3G nanoliposomes against major chronic diseases has been discussed. The focus was on research findings and the mechanism of action to affect the proliferation of cancer, neuro disease and cardiovascular problems. It also discussed the formulation of nanoliposomes, their role in nutraceutical delivery and enhancement in C3G bioavailability.

KEY FINDINGS AND CONCLUSIONS

Data suggested that nanoliposomes safeguard C3G, enhance bioavailability, and ensure safe, adequate and targeted delivery. It can reduce the impact of cancer and inflammation by inhibiting the ß-catenin/O6-methylguanine-DNA methyltransferase (MGMT) pathway and upregulating miR-214-5p. Formation of C3G nanoliposomes significantly enhances the nutraceutical efficacy of C3G against major chronic disease therefore, C3G nanoliposomes might be a future-based nutraceutical to treat major chronic diseases, including cancer, neuro problems and CVD, but challenges remain in finding correct dose and techniques to maximize its efficacy.

A comprehensive review on crosslinked network systems of zinc oxide-organic polymer composites

In recent years, the synergistic crosslinked networks formed by zinc oxide (ZnO) particles and organic polymers have gained significant attention. This importance is ascribed due to the valuable combination of low band gap containing ZnO particles with responsive behavior containing organic polymers. These properties of both ZnO and organic polymers make a suitable system of crosslinked ZnO-organic polymer composite (CZOPC) for various applications in the fields of biomedicine, catalysis, and environmental perspectives. The literature extensively provided the diverse morphologies and structures of CZOPC, and these architectural structures play a crucial role in determining their efficiency across various applications. Consequently, the careful design of CZOPC shapes tailored to specific purposes has become a focal point. This comprehensive review provides insights into the classifications, synthetic approaches, characterizations, and applications of ZnO particles decorated in organic polymers with crosslinked network. The exploration extends to the adsorption, environmental, catalytic, and biomedical applications of ZnO-organic polymer composites. Adopting a tutorial approach, the review systematically investigates and elucidates the applications of CZOPC with a comprehensive understanding of their diverse capabilities and uses.

Relationship between π-A isotherms and single microgel/microgel array structures revealed via the direct visualization of microgels at the air/water interface

The structures of single microgels and microgel arrays formed at the air/water interface were visualized directly, and their structures correlated with π-A isotherms in order to understand the compression behavior of soft and deformable microgels at this interface. Large microgels (ca. 4 μm) were synthesized so that these can be clearly visualized at the air/water interface, even under high compression, and a series of microgel compression experiments were directly evaluated using a Langmuir trough equipped with a fluorescence microscope. The experiments revealed that upon compressing the microgel arrays at the interface voids disappeared and colloidal crystallinity increased. However, the colloidal crystallinity decreased when the microgel arrays were strongly compressed. In addition, when the structures were observed at higher magnification, it became clear that the single microgel structures, when visualized from above, changed from circular to polygonal upon compressing the microgel array. The results of this study can be expected to improve the understanding of the compression behavior of microgel arrays adsorbed at the air/water interface and will thus be useful for the creation of new functional microgel stabilizers with potential applications in e.g., bubbles and emulsions.

Influence of a Solid Surface on PNIPAM Microgel Films

Stimuli-responsive microgels have attracted great interest in recent years as building blocks for fabricating smart surfaces with many technological applications. In particular, PNIPAM microgels are promising candidates for creating thermo-responsive scaffolds to control cell growth and detachment via temperature stimuli. In this framework, understanding the influence of the solid substrate is critical for tailoring microgel coatings to specific applications. The surface modification of the substrate is a winning strategy used to manage microgel-substrate interactions. To control the spreading of microgel particles on a solid surface, glass substrates are coated with a PEI or an APTES layer to improve surface hydrophobicity and add positive charges on the interface. A systematic investigation of PNIPAM microgels spin-coated through a double-step deposition protocol on pristine glass and on functionalised glasses was performed by combining wettability measurements and Atomic Force Microscopy. The greater flattening of microgel particles on less hydrophilic substrates can be explained as a consequence of the reduced shielding of the water-substrate interactions that favors electrostatic interactions between microgels and the substrate. This approach allows the yielding of effective control on microgel coatings that will help to unlock new possibilities for their application in biomedical devices, sensors, or responsive surfaces.

Organic nanoparticles with tunable size and rigidity by hyperbranching and cross-linking using microemulsion ATRP

Unlike inorganic nanoparticles, organic nanoparticles (oNPs) offer the advantage of "interior tailorability," thereby enabling the controlled variation of physicochemical characteristics and functionalities, for example, by incorporation of diverse functional small molecules. In this study, a unique inimer-based microemulsion approach is presented to realize oNPs with enhanced control of chemical and mechanical properties by deliberate variation of the degree of hyperbranching or cross-linking. The use of anionic cosurfactants led to oNPs with superior uniformity. Benefitting from the high initiator concentration from inimer and preserved chain-end functionality during atom transfer radical polymerization (ATRP), the capability of oNPs as a multifunctional macroinitiator for the subsequent surface-initiated ATRP was demonstrated. This facilitated the synthesis of densely tethered poly(methyl methacrylate) brush oNPs. Detailed analysis revealed that exceptionally high grafting densities (~1 nm-2) were attributable to multilayer surface grafting from oNPs due to the hyperbranched macromolecular architecture. The ability to control functional attributes along with elastic properties renders this "bottom-up" synthetic strategy of macroinitiator-type oNPs a unique platform for realizing functional materials with a broad spectrum of applications.

Volume Phase Transition of Thermoresponsive Microgels Scrutinized by Dynamic Light Scattering and Turbidity: Correlations Depend on Microgel Homogeneity

Thermoresponsive microgels experience a volume phase transition triggered by temperature changes, a phenomenon often analyzed using dynamic light scattering to observe overall size alterations via the diffusion coefficient. However, local structural changes are typically assessed using more intricate and expensive techniques like small-angle neutron or X-ray scattering. In our research, we investigate the volume phase transition of poly-N-isopropylacrylamide (PNIPAM)-based microgels by employing a combination of temperature-dependent dynamic light scattering and simpler, faster, and more efficient attenuation measurements. We utilize attenuation at a fixed wavelength as a direct measure of dispersion turbidity, linking the absolute changes in hydrodynamic radius to the absolute changes in turbidity. This approach allows us to compare "classical" PNIPAM microgels from precipitation polymerization, charged copolymer microgels from precipitation copolymerization, and core-shell microgels from seeded precipitation polymerization. Our study includes a systematic analysis and comparison of 30 different microgels. By directly comparing data from dynamic light scattering and attenuation spectroscopy, we gain insights into structural heterogeneity and deviations from the established fuzzy sphere morphology. Furthermore, we demonstrate how turbidity data can be converted to swelling curves.

Facilitating Seed Iron Uptake through Amine-Epoxide Microgels: A Novel Approach to Enhance Cucumber (Cucumis sativus) Germination

Enhancing the initial stages of plant growth by using polymeric gels for seed priming presents a significant challenge. This study aimed to investigate a microgel derived from polyetheramine-poly(propylene oxide) (PPO) and a bisepoxide (referred to as micro-PPO) as a promising alternative to optimize the seed germination process. The micro-PPO integrated with an iron micronutrient showed a positive impact on seed germination compared with control (Fe solutions) in which the root length yield improved up to 39%. Therefore, the element map by synchrotron-based X-ray fluorescence shows that the Fe intensities in the seed primers with the micro-PPO-Fe gel are about 3-fold higher than those in the control group, leading to a gradual distribution of Fe species through most internal embryo tissues. The use of micro-PPO for seed priming underscores their potential for industrial applications due to the nontoxicity results in zebrafish assays and environmentally friendly synthesis of the water-dispersible monomers employed.

Real and In Silico Microgels Show Comparable Bulk Moduli Below and Above the Volume Phase Transition

The compressibility of soft colloids influences their phase behavior and flow properties, especially in concentrated suspensions. Particle compressibility, which is proportional to the reciprocal of the bulk modulus K, is a key parameter for soft polymer-based particles that can be compressed in crowded environments. Here, microgels with different degrees of cross-linking, i.e., softness, are investigated below and above their volume phase transition temperature (VPTT). By combining molecular dynamics simulations with small-angle neutron scattering with contrast variation, a change in the particle bulk moduli of two orders of magnitude is observed. The degree of cross-linking has a significant impact on the bulk modulus of the swollen microgel, while above the VPTT the values of K are almost independent of the cross-linking density. The excellent agreement between experimental results and simulations also highlight that the model microgels from computer simulations possess both the internal architecture and the elastic properties of real polymeric networks. This paves the way to a systematic use of simulations to investigate the behavior of dense microgel suspensions below and above their VPTT.

Keratin-PNIPAM Hybrid Microgels: Preparation, Morphology and Swelling Properties

Combinations of synthetic polymers, such as poly(N-isopropylacrylamide) (PNIPAM), with natural biomolecules, such as keratin, show potential in the field of biomedicine, since these hybrids merge the thermoresponsive properties of PNIPAM with the bioactive characteristics of keratin. This synergy aims to produce hybrids that can respond to environmental stimuli while maintaining biocompatibility and functionality, making them suitable for various medical and biotechnological uses. In this study, we exploit keratin derived from wool waste in the textile industry, extracted via sulfitolysis, to synthesize hybrids with PNIPAM microgel. Utilizing two distinct methods-polymerization of NIPAM with keratin (HYB-P) and mixing preformed PNIPAM microgels with keratin (HYB-M)-resulted in hybrids with 20% and 25% keratin content, respectively. Dynamic light scattering (DLS) and transmission electron microscopic (TEM) analyses indicated the formation of colloidal systems with particle sizes of around 110 nm for HYB-P and 518 nm for HYB-M. The presence of keratin in both systems, 20% and 25%, respectively, was confirmed by spectroscopic (FTIR and NMR) and elemental analyses. Distinct structural differences were observed between HYB-P and HYB-M, suggesting a graft copolymer configuration for the former hybrid and a complexation for the latter one. Furthermore, these hybrids demonstrated temperature responsiveness akin to PNIPAM microgels and pH responsiveness, underscoring their potential for diverse biomedical applications.

Core-softened colloid under extreme geometrical confinement

Geometrical constraints offer a promising strategy for assembling colloidal crystal structures that are not typically observed in bulk or under 2D conditions. Core-softened colloids, in particular, have emerged as versatile chemical building blocks with applications across various scientific and technological areas. In this study, we investigate the behavior of a core-softened model confined between two parallel walls. Employing molecular dynamics simulations, we analyze the system's response under extreme confinement, where only one or two layers of colloids are permitted. The system comprises particles modeled by a ramp-like potential confined within slit nanoslits created by two flat, purely repulsive walls with a lateral side L separated by a distance Lz. Through a systematic analysis of the phase behavior as Lz increases, or as the system undergoes decompression, for different values of L, we identified a mono-to-bilayer transition associated with changes in the colloidal structure. In the monolayer regime, we observed solid phases at lower densities than those observed in the 2D case. Importantly, we demonstrated that confinement at specific Lz values, allowing particle arrangement into two layers, can lead to the emergence of the square phase, which was not observed under monolayer or 2D conditions. By correlating thermodynamic, translational, and orientational ordering, as well as the dynamics of this confined colloidal system, our findings offer valuable insights into the utilization of geometrical constraints to induce and manipulate structural changes.

Sensitize Tumor Immunotherapy: Immunogenic Cell Death Inducing Nanosystems

Low immunogenicity of tumors poses a challenge in the development of effective tumor immunotherapy. However, emerging evidence suggests that certain therapeutic approaches, such as chemotherapy, radiotherapy, and phototherapy, can induce varying degrees of immunogenic cell death (ICD). This ICD phenomenon leads to the release of tumor antigens and the maturation of dendritic cells (DCs), thereby enhancing tumor immunogenicity and promoting immune responses. However, the use of a single conventional ICD inducer often fails to achieve in situ tumor ablation and establish long-term anti-tumor immune responses. Furthermore, the induction of ICD induction varies among different approaches, and the distribution of the therapeutic agent within the body influences the level of ICD and the occurrence of toxic side effects. To address these challenges and further boost tumor immunity, researchers have explored nanosystems as inducers of ICD in combination with tumor immunotherapy. This review examines the mechanisms of ICD and different induction methods, with a specific focus on the relationship between ICD and tumor immunity. The aim is to explore the research advancements utilizing various nanomaterials to enhance the body's anti-tumor effects by inducing ICD. This paper aims to contribute to the development and clinical application of nanomaterial-based ICD inducers in the field of cancer immunotherapy by providing important theoretical guidance and practical references.

Charged hollow microgel capsules

Responsive hollow microgels are a fascinating class of soft model systems at the crossover between polymer capsules and microgels. The presence of the cavity makes them promising materials for encapsulation and controlled release applications but also confers them an additional softness that is reflected by their peculiar behaviour in bulk and at interfaces. Their responsivity to external stimuli, such as temperature, pH, and ionic strength, can be designed from their synthesis conditions and the choice of functional moieties. So far most studies have focused on "small" hollow microgels that were mostly studied with scattering or atomic force microscopy techniques. In our previous study, we have shown that large fluorescent hollow poly(N-isopropylacrylamide) (PNIPAM) microgels could be synthesized using micrometer-sized silica particles as sacrificial templates allowing their investigation in situ via confocal microscopy. In this work, we extend this approach to charged large hollow microgels based on poly(N-isopropylacrylamide-co-itaconic acid) (P(NIPAM-co-IA)). Hereby, we compare the structure and responsivity of "neutral" (PNIPAM) and "charged" (P(NIPAM-co-IA)) hollow microgel systems synthesized under similar conditions with the same sacrificial template using confocal and atomic force microscopy and light scattering techniques. In particular, we could demonstrate the extremely soft character of the swollen charged hollow microgels and their responsivity to pH, ionic strength, and temperature. To conclude this study, the buckling behavior of the different capsules was investigated illustrating the potential of such systems to change its conformation by varying the osmotic pressure and pH conditions.

A review on Ag nanoparticles fabricated in microgels

In recent years, there has been growing interest in the composites of multi-responsive microgels and silver nanoparticles. This innovative hybrid system harnesses the responsive qualities of microgels while capitalizing on the optical and electronic attributes of silver nanoparticles. This combined system demonstrates a rapid response to minor changes in pH, temperature, ionic strength of the medium, and the concentration of specific biological substances. This review article presents an overview of the recent advancements in the synthesis, classification, characterization methods, and properties of microgels loaded with silver nanoparticles. Furthermore, it explores the diverse applications of these responsive microgels containing silver nanoparticles in catalysis, the biomedical field, nanotechnology, and the mitigation of harmful environmental pollutants.

Nanocrystal Assemblies: Current Advances and Open Problems

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.

Nanogels with Metal-Organic Cages as Functional Crosslinks

A dinuclear metal-organic cage with four acrylate side chains was prepared by self-assembly. Precipitation polymerization of the cage with N-isopropylacrylamide yielded a thermoresponsive nanogel. The host properties of the cage were retained within the gel matrix, endowing the nanogel with the capability to serve as a sorbent for chloride ions in water. Moreover, a heteroleptic cage with the drug abiraterone as co-ligand was integrated into a nanogel. The addition of chloride ions induced a structural rearrangement of the metal-ligand assembly, resulting in the gradual release of abiraterone.

Biopolymer-based beads for the adsorptive removal of organic pollutants from wastewater: Current state and future perspectives

Among biopolymer-based adsorbents, composites in the form of beads have shown promising results in terms of high adsorption capacity and ease of separation from the effluents. This review addresses the potential of biopolymer-based beads to remediate wastewaters polluted with emerging organic contaminants, for instance dyes, active pharmaceutical ingredients, pesticides, phenols, oils, polyaromatic hydrocarbons, and polychlorinated biphenyls. High adsorption capacities up to 2541.76 mg g-1 for dyes, 392 mg g-1 for pesticides and phenols, 1890.3 mg g-1 for pharmaceuticals, and 537 g g-1 for oils and organic solvents have been reported. The review also attempted to convey to its readers the significance of wastewater treatment through adsorption by providing an overview on decontamination technologies of organic water contaminants. Various preparation methods of biopolymer-based gel beads and adsorption mechanisms involved in the process of decontamination have been summarized and analyzed. Therefore, we believe there is an urge to discuss the current state of the application of biopolymer-based gel beads for the adsorption of organic pollutants from wastewater and future perspectives in this regard since it is imperative to treat wastewater before releasing into freshwater bodies.

Controlled creation of point defects in three-dimensional colloidal crystals

Crystal defects crucially influence the properties of crystalline materials and have been extensively studied. Even for the simplest type of defect-the point defect-however, basic properties such as their diffusive behavior, and their interactions, remain elusive on the atomic scale. Here, we demonstrate in situ control over the creation of isolated point defects in a three-dimensional (3D) colloidal crystal allowing insight on a single-particle level. Our system consists of thermoresponsive microgel particles embedded in a crystal of nonresponsive colloids. Heating this mixed-particle system triggers the shrinking of the embedded microgels, which then vacate their lattice positions, creating vacancy-interstitial pairs. We use temperature-controlled confocal laser scanning microscopy to verify and visualize the formation of the point defects. In addition, by reswelling the microgels we quantify the local lattice distortion around an interstitial defect. Our experimental model system provides a unique opportunity to shed light on the interplay between point defects, on the mechanisms of their diffusion, on their interactions, and on collective dynamics.