Stimuli-responsive LbL capsules and nanoshells for drug delivery

Frontier in gellan gum-based microcapsules obtained by emulsification: Core-shell structure, interaction mechanism, intervention strategies

As a translucent functional gel with biodegradability, non-toxicity and acid resistance, gellan gum has been widely used in probiotic packaging, drug delivery, wound dressing, metal ion adsorption and other fields in recent years. Because of its remarkable gelation characteristics, gellan gum is suitable as the shell material of microcapsules to encapsulate functional substances, by which the functional components can improve stability and achieve delayed release. In recent years, many academically or commercially reliable products have rapidly emerged, but there is still a lack of relevant reports on in-depth research and systematic summaries regarding the process of microcapsule formation and its corresponding mechanisms. To address this challenge, this review focuses on the formation process and applications of gellan gum-based microcapsules, and details the commonly used preparation methods in microcapsule production. Additionally, it explores the impact of factors such as ion types, ion strength, temperature, pH, and others present in the solution on the performance of the microcapsules. On this basis, it summarizes and analyzes the prospects of gellan gum-based microcapsule products. The comprehensive insights from this review are expected to provide inspiration and design ideas for researchers.

Core-shell nanofibers based on microalgae proteins/alginate complexes for enhancing survivability of probiotics

In this study, a novel one-step coaxial electrospinning process is employed to fabricate shell-core structure fibers choosing Chlorella pyrenoidosa proteins (CP) as the core material. These nanofibers, serving as the wall material for probiotic encapsulation, aimed to enhance the stability and antioxidant activity of probiotics in food processing, storage, and gastrointestinal environments under sensitive conditions. Morphological analysis was used to explore the beads-on-a-string morphology and core-shell structure of the electrospun fibers. Probiotics were successfully encapsulated within the fibers (7.97 log CFU/g), exhibiting a well-oriented structure along the distributed fibers. Compared to free probiotics and uniaxial fibers loaded with probiotics, encapsulation within microalgae proteins/alginate core-shell structure nanofibers significantly enhanced the probiotic cells' tolerance to simulated gastrointestinal conditions (p < 0.05). Thermal analysis indicated that microalgae proteins/alginate core-shell structure nanofibers displayed superior thermal stability compared to uniaxial fibers. The introduction of CP resulted in a 50 % increase in the antioxidant capacity of probiotics-loaded microalgae proteins/alginate nanofibers compared to uniaxial alginate nanofibers, with minimal loss of viability (0.8 log CFU/g) after 28 days of storage at 4 °C. In summary, this dual-layer carrier holds immense potential in probiotic encapsulation and enhancing their resistance to harsh conditions.

Reversible Binding Interfaces Made of Microstructured Polymer Brushes

The polymer brush architecture of the end-tethered polymer molecules is one of the most widely used efficient methods to regulate interfacial interactions in colloidal systems found in live matter and manufactured materials. Emerging applications of polymer brush structures require solutions to new tasks in the control of interfacial interactions. The rapid development of live cell manufacturing relies on scalable and efficient cell harvesting methods. Stimuli-responsive surfaces made of surface-grafted poly(N-isopropylacrylamide) (PNIPAM) can bind and detach the adherent cell upon changes in temperature and have been used for cell growth and harvesting. The applications are limited by the requirement to satisfy a range of PNIPAM coating characteristics that depend on the dimensions of the integrin complex in the cell membrane and the basal surface. The analysis of the microstructured surfaces, when adhesive and disjoining functions of the microdomains are decoupled, shows that many limitations of PNIPAM one-component coatings can be avoided by using a much broader range of structural characteristics of the microstructured interfaces composed of alternating disjoining PNIPAM domains and adhesive polymeric domains with cell-affinity functional groups. Temperature-controlled reversible adhesion to such microstructured interfaces is studied here experimentally with model systems of solid spherical particles and by employing simulations for solid and soft membranes interacting with the microstructured surfaces to mimic interactions with soft and solid disk-like particles.

Layer-by-layer designer nanoarchitectonics for physical and chemical communications in functional materials

Nanoarchitectonics, as a post-nanotechnology concept, constructs functional materials and structures using nanounits of atoms, molecules, and nanomaterials as materials. With the concept of nanoarchitectonics, asymmetric structures, and hierarchical organization, rather than mere assembly and organization of structures, can be produced, where rational physical and chemical communications will lead to the development of more advanced functional materials. Layer-by-layer assembly can be a powerful tool for this purpose, as exemplified in this feature paper. This feature article explores the possibility of constructing advanced functional systems based on recent examples of layer-by-layer assembly. We will illustrate both the development of more basic methods and more advanced nanoarchitectonics systems aiming towards practical applications. Specifically, the following sections will provide examples of (i) advancement in basics and methods, (ii) physico-chemical aspects and applications, (iii) bio-chemical aspects and applications, and (iv) bio-medical applications. It can be concluded that materials nanoarchitectonics based on layer-by-layer assembly is a useful method for assembling asymmetric structures and hierarchical organization, and is a powerful technique for developing functions through physical and chemical communication.

Radioprotective Potency of Nanoceria

Cancer presents a significant medical challenge that requires effective management. Current cancer treatment options, such as chemotherapy, targeted therapy, radiotherapy, and immunotherapy, have limitations in terms of their efficacy and the potential harm they can cause to normal tissues. In response, researchers have been focusing on developing adjuvants that can enhance tumor responses while minimizing damage to healthy tissues. Among the promising options, nanoceria (NC), a type of nanoparticle composed of cerium oxide, has garnered attention for its potential to improve various cancer treatment regimens. Nanoceria has demonstrated its ability to exhibit toxicity towards cancer cells, inhibit invasion, and sensitize cancer cells to both radiation therapy and chemotherapy. The remarkable aspect is that nanoceria show minimal toxicity to normal tissues while protecting against various forms of reactive oxygen species generation. Its capability to enhance the sensitivity of cancer cells to chemotherapy and radiotherapy has also been observed. This paper thoroughly reviews the current literature on nanoceria's applications within different cancer treatment modalities, with a specific focus on radiotherapy. The emphasis is on nanoceria's unique role in enhancing tumor radiosensitization and safeguarding normal tissues from radiation damage.

Recent Progress in Stimuli-Responsive Antimicrobial Electrospun Nanofibers

Electrospun nanofibrous membranes have garnered significant attention in antimicrobial applications, owing to their intricate three-dimensional network that confers an interconnected porous structure, high specific surface area, and tunable physicochemical properties, as well as their notable capacity for loading and sustained release of antimicrobial agents. Tailoring polymer or hybrid-based nanofibrous membranes with stimuli-responsive characteristics further enhances their versatility, enabling them to exhibit broad-spectrum or specific activity against diverse microorganisms. In this review, we elucidate the pivotal advancements achieved in the realm of stimuli-responsive antimicrobial electrospun nanofibers operating by light, temperature, pH, humidity, and electric field, among others. We provide a concise introduction to the strategies employed to design smart electrospun nanofibers with antimicrobial properties. The core section of our review spotlights recent progress in electrospun nanofiber-based systems triggered by single- and multi-stimuli. Within each stimulus category, we explore recent examples of nanofibers based on different polymers and antimicrobial agents. Finally, we delve into the constraints and future directions of stimuli-responsive nanofibrous materials, paving the way for their wider application spectrum and catalyzing progress toward industrial utilization.

Mechanobiology of Ferroptotic Cancer Cells as a Novel "Eat-Me" Signal: Regulating Efferocytosis through Layer-by-Layer Coating

The importance of the clearance of dead cells is shown to have a regulatory role for normal tissue homeostasis and for the modulation of immune responses. However, how mechanobiological properties of dead cells affect efferocytosis remains largely unknown. Here, it is reported that the Young's modulus of cancer cells undergoing ferroptosis is reduced. To modulate their Young's modulus a layer-by-layer (LbL) nanocoating is developed. Scanning electron and fluorescence microscopy confirm coating efficiency of ferroptotic cells while atomic force microscopy reveals encapsulation of the dead cells increases their Young's modulus dependent on the number of applied LbL layers which increases their efferocytosis by primary macrophages. This work demonstrates the crucial role of mechanobiology of dead cells in regulating their efferocytosis by macrophages which can be exploited for the development of novel therapeutic strategies for diseases where modulation of efferocytosis can be potentially beneficial and for the design of drug delivery systems for cancer therapy.

Room temperature bio-engineered multifunctional carbonates for CO2 sequestration and valorization

This contribution reports, for the first time, on an entirely green bio-engineering approach for the biosynthesis of single phase crystalline 1-D nano-scaled calcite CaCO3. This was validated using H2O as the universal solvent and natural extract of Hyphaene thebaica fruit as an effective chelating agent. In this room temperature green process, CaCl2 and CO2 are used as the unique source of Ca and CO3 respectively in view of forming nano-scaled CaCO3 with a significant shape anisotropy and an elevated surface to volume ratio. In terms of novelty, and relatively to the reported scientific and patented literature in relation to the fabrication of CaCO3 by green nano-chemistry, the current cost effective room temperature green process can be singled out as per the following specificities: only water as universal solvent is used, No additional base or acid chemicals for pH control, No additional catalyst, No critical or supercritical CO2 usage conditions, Only natural extract of thebaica as a green effective chelating agent through its phytochemicals and proper enzematic compounds, room Temperature processing, atmospheric pressure processing, Nanoscaled size particles, and Nanoparticles with a significant shape anisotropy (1-D like nanoparticles). Beyond and in addition to the validation of the 1-D synthesis aspect, the bio-engineered CaCO3 exhibited a wide-ranging functionalities in terms of highly reflecting pigment, an effective nanofertilizer as well as a potential binder in cement industry.

Liquid-Liquid Encapsulation: Penetration vs. Trapping at a Liquid Interfacial Layer

Encapsulation protects vulnerable cores in an aggressive environment and imparts desirable functionalities to the overall encapsulated cargo, including control of mechanical properties, release kinetics, and targeted delivery. Liquid-liquid encapsulation to create such capsules, where a liquid layer (shell) is used to wrap another liquid (core), is an attractive value proposition for ultrafast encapsulation (∼100 ms). Here, we demonstrate a robust framework for stable liquid-liquid encapsulation. Wrapping is achieved by simple impingement of a target core (in liquid form) on top of an interfacial layer of another shell-forming liquid floating on a host liquid bath. Poly(dimethylsiloxane) (PDMS) is chosen as the shell-forming liquid due to its biocompatibility, physicochemical stability, heat curability, and acceptability as both a drug excipient and food additive. Depending on the kinetic energy of the impinging core droplet, encapsulation is accomplished by either of the two pathways─necking-driven complete interfacial penetration and subsequent generation of encapsulated droplets inside the host bath or trapping inside the interfacial layer. Combining thermodynamic argument with experimental demonstration, we show that the interfacially trapped state, which results in a low kinetic energy of impact, is also an encapsulated state where the core droplet is wholly enclosed inside the floating interfacial layer. Therefore, despite being impact-driven, our method remains kinetic energy independent and minimally restrictive. We describe the underlying interfacial evolution behind encapsulation and experimentally identify a nondimensional regime of occurrence for the two pathways mentioned above. Successful encapsulation by either path offers efficient long-term protection of the encased cores in aggressive surroundings (e.g., protection of honey/maple syrup inside a water bath despite their miscibility). We enable the generation of multifunctional compound droplets via interfacial trapping, where multiple core droplets with different compositions are encapsulated within the same wrapping shell. Further, we demonstrate the practical utility of the interfacially trapped state by showing successful heat-curing of the shell and subsequent extraction of the capsule. The cured capsules are sufficiently robust and remain stable under normal handling.

Effect of Poly(Vinyl Alcohol) Concentration and Chain Length on Polymer Nanogel Formation in Aqueous Dispersion Polymerization

Nanotechnology has attracted increasing interest in various research fields for fabricating functional nanomaterials. In this study, we investigated the effect of poly(vinyl alcohol) (PVA) addition on the formation and thermoresponsive properties of poly(N-isopropyl acrylamide)-based nanogels in aqueous dispersion polymerizations. During dispersion polymerization, PVA appears to play three roles: (i) it bridges the generated polymer chains during polymerization, (ii) it stabilizes the formed polymer nanogels, and (iii) it regulates the thermoresponsive properties of the polymer nanogels. By regulating the bridging effect of PVA via changing the PVA concentration and chain length, the size of the obtained polymer gel particles was maintained in the nanometer range. Furthermore, we found that the clouding-point temperature increased when using low-molecular weight PVA. We believe that the knowledge gained in this study regarding the effect of PVA concentration and chain length on nanogel formation will aid in the future fabrication of functional polymer nanogels.

Influence of Ionic Strength and Specific Ion Effects on Polyelectrolyte Multilayer Films with pH-Responsive Behavior

Layer-by-layer assembled multilayer films have shown great potential for different applications owing to their responsive behavior. Herein, we systematically investigated the effects of composition, salt concentration, and ion specificity on the pH responsiveness of covalently crosslinked chitosan and alginate dialdehyde multilayer films. The changes in film swelling were measured using ellipsometry from low (0.01 mM) to high (3 M) salt (NaCl or NaSCN) concentrations at pH 3, 6, and 9. The swelling responses to increasing ionic strength matched the swelling responses observed for polyzwitterionic and weak monocomponent polyelectrolyte films and depended on the multilayer composition, pH, and ion specificity. Finally, we used the ellipsometric data to demonstrate that the pH responsiveness of such multilayer films, as measured using a quartz crystal microbalance with dissipation monitoring, strongly depends on the ionic condition under which the responses were measured. We thus show that erroneous conclusions about the pH responsiveness of polyelectrolyte multilayer films can be easily obtained if the ionic environment of the application does not closely resemble the ionic condition under which the pH responsiveness is tested.

Spontaneous shrinkage drives macromolecule encapsulation into layer-by-layer assembled biopolymer microgels

HYPOTHESIS

Recently, the anomalous shrinkage of surface-supported hyaluronate/poly-l-lysine (HA/PLL) microgels (µ-gels), which exceeds that reported for any other multilayer-based systems, has been reported [1]. The current study investigates the capability of these unique µ-gels for the encapsulation and retention of macromolecules, and proposes the shrinkage-driven assembly of biopolymer-based µ-gels as a novel tool for one-step surface biofunctionalization.

EXPERIMENTS

A set of dextrans (DEX) and their charged derivatives - carboxymethyl (CM)-DEX and diethylaminoethyl (DEAE)-DEX - has been utilized to evaluate the effects of macromolecular mass and net charge on µ-gel shrinkage and macromolecule entrapment. µ-gels formation on the surface of silicone catheters exemplifies their potential to tailor biointerfaces.

FINDINGS

Shrinkage-driven µ-gel formation strongly depends on the net charge and mass content of encapsulated macromolecules. Inclusion of neutral DEX decreases the degree of shrinkage several times, whilst charged DEXs adopt to the backbone of oppositely charged polyelectrolytes, resulting in shrinkage comparable to that of non-loaded µ-gels. Retention of CM-DEX in µ-gels is significantly higher compared to DEAE-DEX. These insights into the mechanisms of macromolecular entrapment into biopolymer-based µ-gels promotes fundamental understanding of molecular dynamics within the multilayer assemblies. Organization of biodegradable µ-gels at biomaterial surfaces opens avenues for their further exploitation in a diverse array of bioapplications.

Probing the effect of the capping polyelectrolyte on the internal structure of Layer-by-Layer decorated nanoliposomes

HYPOTHESIS

The internal organization of polyelectrolyte layers deposited on colloidal templates plays a very important role for the potential applications of these systems as capsules for drug delivery purposes.

EXPERIMENTS

The mutual arrangement of oppositely charged polyelectrolyte layers upon their deposition on positively charged liposomes has been studied by combining up three different scattering techniques and Electronic Spin Resonance, which has provided information about the inter-layer interactions and their effect on the final structure of the capsules.

FINDINGS

The sequential deposition of oppositely charged polyelectrolytes on the external leaflet of positively charged liposomes allows modulating the organization of the obtained supramolecular structures, impacting the packing and rigidity of the obtained capsules due to the change of the ionic cross-linking of the multi-layered film as a result of the specific charge of the last deposited layer. The possibility to modulate the properties of the LbL capsules by tuning the characteristics of the last deposited layers offers a very interesting route for the design of materials for encapsulation purposes with their properties controlled almost at will by changing the number of deposited layers and their chemistry.

Spectro-kinetic investigations on the release mechanism of lysozyme from layer-by-layer reservoirs

The investigations of protein adsorption and release on interfaces aid in the elucidation of the protein-surface interaction mechanism, which has several applications in the biomedical area. The spectro-kinetic and morphological analysis of the release of lysozyme (Lyz) from chitosan/polystyrene sulphonate (CHI/PSS) multilayer immobilized at pHs 10.6, 8.8 and 5.0 shows that the extent of release strongly depends on the pH of Lyz loading and the ionic strength of the desorbing solution. When compared to pH 8.8, the release for pH 10.6 achieves equilibrium more rapidly. At loading pH 10.6, the release is surface-mediated, at pH 8.8, it is both surface- and bulk-mediated, while at pH 5.0 it is bulk mediated with minimal release. Lyz released for loading pH 10.6 retains its native secondary structure. Kinetic fitting suggests that high loading pH 8.8-10.6 and high release ionic strength (0.5-1.0 M NaCl) lead to burst release of Lyz from CHI/PSS multilayer. Surface morphology changes of multilayer interface upon Lyz loading and release are highlighted by SEM topography and AFM height distribution analysis. The present work indicates that CHI/PSS multilayer system can function as a reservoir for burst as well as controlled release of lysozyme by selecting the loading pH and ionic strength.

A decade of developing applications exploiting the properties of polyelectrolyte multilayer capsules

Transferring the layer-by-layer (LbL) coating approach from planar surfaces to spherical templates and subsequently dissolving these templates leads to the fabrication of polyelectrolyte multilayer capsules. The versatility of the coatings of capsules and their flexibility upon bringing in virtually any material into the coatings has quickly drawn substantial attention. Here, we provide an overview of the main developments in this field, highlighting the trends in the last decade. In the beginning, various methods of encapsulation and release are discussed followed by a broad range of applications, which were developed and explored. We also outline the current trends, where the range of applications is continuing to grow, including addition of whole new and different application areas.

Effects of Feed Solution pH on Polyelectrolyte Multilayer Nanofiltration Membranes

Over the past decade polyelectrolyte multilayer (PEM)-based membranes have gained a lot of interest in the field of nanofiltration (NF) as an alternative to conventional polyamide-based thin film composite membranes. With great variety in fabrication conditions, these membranes can achieve superior properties such as high chemical resistance and excellent filtration performance. Some of the most common polyelectrolytes used to prepare NF membranes are weak, meaning that their charge density depends on pH within the normal window of operation relevant for potential applications (pH 0-14). This might cause a dependency of membrane properties on the pH of filtered solutions, as indicated by other applications of PEMs. In this work, the susceptibility of membrane structure (swelling and surface charge) and performance (permeability, molecular weight cutoff, and salt retention) toward the pH of the filtration solution was studied for four fundamentally different PEM systems: poly(diallyldimethylammonium chloride) (PDADMAC)/poly(sodium-4-styrenesulfonate) (PSS) (strong/strong), poly(allylamine hydrochloric acid) (PAH)/poly(acrylic acid) (PAA) (weak/weak), and PAH/PSS (weak/strong) and PAH/PSS+PAH/PAA (asymmetric). Slight variations in structure and performance of the PDADMAC/PSS-based membranes were observed. On the contrary, structure and performance of PAH/PAA-based membranes are very susceptible to feed solution pH. A continuous change in charge density with variation in pH significantly affects salt retention. An increased swelling at pH 9 translates to variation in permeability and molecular weight cutoff of the membrane. The susceptibility of PAH/PSS-based membranes to pH is less pronounced compared to the PAH/PAA-based membranes since only one of the polyelectrolytes involved is weak. No structural changes were observed, indicating additional specific interactions between the polyelectrolytes other than electrostatic forces that stabilize film structure. A combination of the PAH/PSS and PAH/PAA system (8 + 2 bilayers) also displays a clear dependency of both membrane structure and performance on solution pH, where PAH/PSS is dominating due to a higher bilayer number.

Uricase Crowding via Polyelectrolyte Layers Coacervation for Carbon Fiber-Based Electrochemical Detection of Uric Acid

Urate oxidase (UOx) surrounded by synthetic macromolecules, such as polyethyleneimine (PEI), poly(allylamine hydrochloride) (PAH), and poly(sodium 4-styrenesulfonate) (PSS) is a convenient model of redox-active biomacromolecules in a crowded environment and could display high enzymatic activity towards uric acid, an important marker of COVID-19 patients. In this work, the carbon fiber electrode was modified with Prussian blue (PB) redox mediator, UOx layer, and a layer-by-layer assembled polyelectrolyte film, which forms a complex coacervate consisting of a weakly charged polyelectrolyte (PEI or PAH) and a highly charged one (PSS). The film deposition process was controlled by cyclic voltammetry and scanning electron microscopy coupled with energy-dispersive X-ray analysis (at the stage of PB deposition) and through quartz crystal microbalance technique (at latter stages) revealed uniform distribution of the polyelectrolyte layers. Variation of the polyelectrolyte film composition derived the following statements. (1) There is a linear correlation between electrochemical signal and concentration of uric acid in the range of 10^-4-10^-6 M. (2) An increase in the number of polyelectrolyte layers provides more reproducible values for uric acid concentration in real urine samples of SARS-CoV-2 patients measured by electrochemical enzyme assay, which are comparable to those of spectrophotometric assay. (3) The PAH/UOx/PSS/(PAH/PSS)₂-coated carbon fiber electrode displays the highest sensitivity towards uric acid. (4) There is a high enzyme activity of UOx immobilized into the hydrogel nanolayer (values of the Michaelis-Menten constant are up to 2 μM) and, consequently, high affinity to uric acid.

Nanoarchitectonics beyond perfect order - not quite perfect but quite useful

Nanoarchitectonics, like architectonics, allows the design and building of structures, but at the nanoscale. Unlike those in architectonics, and even macro-, micro-, and atomic-scale architectonics, the assembled structures at the nanoscale do not always follow the projected design. In fact, they do follow the projected design but only for self-assembly processes producing structures with perfect order. Here, we look at nanoarchitectonics allowing the building of nanostructures without a perfect arrangement of building blocks. Here, fabrication of structures from molecules, polymers, nanoparticles, and nanosheets to polymer brushes, layer-by-layer assembly structures, and hydrogels through self-assembly processes is discussed, where perfect order is not necessarily the aim to be achieved. Both planar substrate and spherical template-based assemblies are discussed, showing the challenging nature of research in this field and the usefulness of such structures for numerous applications, which are also discussed here.

Stimulus responsive microcapsules and their aromatic applications

Fragrances and essential oils are promising for a wide range of applications due to their pleasant odors and diverse effects. However, direct addition to consumer products has the disadvantages of short retention time and easy deterioration of odor. At the same time, releasing a large amount of odor in a short time may be an unpleasant experience, which severely limits the practical application of aromatic substances. Microencapsulation perfectly solves these problems. Stimuli-responsive microcapsules, which combine environmental stimulation with microencapsulation, can not only effectively prevent the rapid decomposition and evaporation of aroma components, but also realize the "on-off" intelligent release of aroma substances to environmental changes, which have great promise in the field of fragrances. In this review, the application of stimuli-responsive microcapsules in fragrances is highlighted. Firstly, various encapsulation materials used to prepare stimuli-responsive aromatic microcapsules are described, mainly including some natural polymers, synthetic polymers, and inorganic materials. Subsequently, there is a detailed description of the common release mechanisms of stimuli-responsive aromatic microcapsules are described in detail. Finally, the application and future research directions are given for stimuli-responsive aromatic microcapsules in new textiles, food, paper, and leather.

Advances in polysaccharide-based nano/microcapsules for biomedical applications: A review

Biocompatible and biodegradable polysaccharides are abundant and renewable natural materials. Polysaccharides and their derivatives are developed into various carrier materials for biomedical applications. In particular, advanced polysaccharide-based nano/microcapsules have received extensive attention in biomedical applications due to their good encapsulation ability and tunability. In recent years, polysaccharide-based nano/microcapsules have been widely used in drug carriers, gene carriers, antigen carriers, wound dressings, bioimaging and biosensors. Numerous research results have confirmed the feasibility, safety, and effectiveness of polysaccharide-based nano/microcapsules in the above-mentioned biomedical applications. This review discussed and analyzed the latest research strategies and design considerations for these applications in detail. The preparation methods, application strategies, and design considerations of polysaccharide-based nano/microcapsules are summarized and analyzed, and their challenges and future research prospects in biomedicine are further discussed. It is expected to provide researchers with inspiration and design ideas.

Facile Construction of a Two-in-One Injectable Micelleplex-Loaded Thermogel System for the Prolonged Delivery of Plasmid DNA

Nanoparticle-hydrogel systems have recently emerged as a class of interesting hybrid materials with immense potential for several biomedical applications. Remarkably, the incorporation of nanoparticles into a hydrogel may yield synergistic benefits lacking in a singular system. However, most synthetic strategies require laborious steps to achieve the system, severely restricting the process of translational research. Herein, a facile strategy to access a two-in-one system comprising two distinct polyurethane (PU)-based micellar systems is demonstrated and applied as a novel sustained gene delivery platform, where the two PUs are synthesized similarly but with slightly different compositions. One PU forms cationic micelles that complex with plasmid DNA (pDNA), which are loaded into a thermogel formed by another PU micellar system for the prolonged release of pDNA micelleplexes. Specifically, a thermogelling multiblock PU copolymer (denoted as EPH) was synthesized via the step-growth polymerization of poly(ethylene glycol), poly(propylene glycol), and poly(3-hydroxybutyrate). By further introducing a cationic extender, 3-(dimethylamino)-1,2-propanediol, into the reaction feed, a series of cationic PUs (denoted as EPHD) with varying compositions were obtained. The EPHDs formed positively charged micelles in aqueous solutions, efficiently condensed pDNA into nano-sized micelleplexes (<200 nm) at optimized w/w ratios, and mediated transient green fluorescence protein expression in HEK293T cells at 48 h post-transfection. On the other hand, aqueous EPH solution (4 wt %) was injectable at 4 °C and rapidly gelled upon heating to 37 °C to form a stable hydrogel depot. EPHD/pDNA micelleplexes were easily loaded into EPH by mixing the solutions at 4 °C, before heating to 37 °C, leading to the resultant hydrogel system. The in vitro release study revealed that while free pDNA loaded in the thermogel was completely released in 2 weeks, the release of EPHD/pDNA micelleplexes was prolonged to at least 28 days, suggesting substantial micelleplex-hydrogel interactions. Intact, bioactive, and noncytotoxic EPHD/pDNA micelleplexes in the release media were proved by gel retardation, in vitro gene transfection, and CCK-8 cytotoxicity assay results, respectively. Collectively, this work presents a simple approach to achieving and optimizing a novel two-in-one nanoparticle-hydrogel system for the prolonged delivery of pDNA and may be promising for long-term gene delivery applications.

Designing anisotropic inorganic nanocapsules via self-assembly of polymer-like ultrathin Au nanowires

Anisotropic assembly of nanomaterials into hollow structures is an attractive technique in biomedicine and biosensing. Commonly used polymer materials are easy to assemble yet it is hard to form anisotropic morphologies. Here in this work, we successfully prepared a novel gold nanocapsule with an anisotropic ellipsoidal shape and cavity structure by the self-assembly of ultrathin Au nanowires. The assembly mechanism is further studied by tuning the assembly conditions such as nanowire concentration, solvent composition, and temperature. It is found that the controlling forces of the nanowire assembly process are mainly the symmetric interfacial tension and the asymmetric nanowire deformation potential, which contribute together to result in anisotropic nanocapsules. Finally, the obtained Au nanocapsules were used as nanocarriers to load pyrene as a model drug, showing great drug loading ability and pH-responsive drug release behavior. We believe that this unique anisotropic assembly product will bring new insights into nanostructure design and soft matter research.

Fire-Shaped Nozzles to Produce a Stress Peak for Deformability Studies

Fire-shaped nozzles can be used to study the deformability of microcapsules, particles, or cells traveling in a flow. Though their geometry depends on the dimensions of the original glass capillary and the heating conditions, they all produce a strain rate peak approximately at the section where the diameter is 1.5 times the minimum. The intensity of this peak and the time from its position to the neck can be easily estimated from the flow rate and three geometrical parameters, without the need for any simulation. In the convergent region of these nozzles, it is possible to observe the evolution of the deformation. It is necessary to use a sufficiently long nozzle to produce the maximum deformation before the neck.

Immunogenic Cell Death and Role of Nanomaterials Serving as Therapeutic Vaccine for Personalized Cancer Immunotherapy

Immunogenic cell death (ICD) is a rapidly growing research area representing one of the emerging therapeutic strategies of cancer immunotherapy. ICD is an umbrella term covering several cell death modalities including apoptosis, necroptosis, ferroptosis and pyroptosis, and is the product of a balanced combination of adjuvanticity (damage-associated molecular patterns and chemokines/cytokines) and antigenicity (tumor associated antigens). Only a limited number of anti-cancer therapies are available to induce ICD in experimental cancer therapies and even much less is available for clinical use. To overcome this limitation, nanomaterials can be used to increase the immunogenicity of cancer cells killed by anti-cancer therapy, which in themselves are not necessarily immunogenic. In this review, we outline the current state of knowledge of ICD modalities and discuss achievements in using nanomaterials to increase the immunogenicity of dying cancer cells. The emerging trends in modulating the immunogenicity of dying cancer cells in experimental and translational cancer therapies and the challenges facing them are described. In conclusion, nanomaterials are expected to drive further progress in their use to increase efficacy of anti-cancer therapy based on ICD induction and in the future, it is necessary to validate these strategies in clinical settings, which will be a challenging research area.

Modified Poisson–Boltzmann theory for polyelectrolytes in monovalent salt solutions with finite-size ions

We present a soft-potential-enhanced Poisson–Boltzmann (SPB) theory to efficiently capture ion distributions and electrostatic potential around rodlike charged macromolecules. The SPB model is calibrated with a coarse-grained particle-based model for polyelectrolytes (PEs) in monovalent salt solutions as well as compared to a full atomistic molecular dynamics simulation with the explicit solvent. We demonstrate that our modification enables the SPB theory to accurately predict monovalent ion distributions around a rodlike PE in a wide range of ion and charge distribution conditions in the weak-coupling regime. These include excess salt concentrations up to 1M and ion sizes ranging from small ions, such as Na+ or Cl−, to softer and larger ions with a size comparable to the PE diameter. The work provides a simple way to implement an enhancement that effectively captures the influence of ion size and species into the PB theory in the context of PEs in aqueous salt solutions.

Micro/Nanosystems for Magnetic Targeted Delivery of Bioagents

Targeted delivery of pharmaceuticals is promising for efficient disease treatment and reduction in adverse effects. Nano or microstructured magnetic materials with strong magnetic momentum can be noninvasively controlled via magnetic forces within living beings. These magnetic carriers open perspectives in controlling the delivery of different types of bioagents in humans, including small molecules, nucleic acids, and cells. In the present review, we describe different types of magnetic carriers that can serve as drug delivery platforms, and we show different ways to apply them to magnetic targeted delivery of bioagents. We discuss the magnetic guidance of nano/microsystems or labeled cells upon injection into the systemic circulation or in the tissue; we then highlight emergent applications in tissue engineering, and finally, we show how magnetic targeting can integrate with imaging technologies that serve to assist drug delivery.

Adsorption of soft NIPAM nanogels at hydrophobic and hydrophilic interfaces: Conformation of the interfacial layers determined by neutron reflectivity

The application of stimuli-responsive microgels and nanogels in drug delivery, catalysis, sensing, and coatings is restricted currently by the limited understanding of the factors influencing their adsorption dynamics and structural changes at interfaces. We have used neutron reflectivity to resolve, on the Ångström scale, the structure of 5% crosslinked N-isopropylacrylamide nanogels at both hydrophobic and hydrophilic interfaces in situ, as a function of temperature and bulk nanogel concentration. Our results show that the higher flexibility given by the low crosslinker content allows for a more ordered structure and packing. The adsorption of the thermoresponsive nanogels is primarily driven by temperature, more specifically its proximity to its volume phase transition temperature, while concentration plays a secondary role. Hydrophobic interactions drive the conformation of the first layer at the interface, which plays a key role in influencing the overall nanogel structure. The mobility of the first layer at the air-water interface as opposed to the interfacial confinement at the solid (SiC8)-liquid interface, results in a different conformation, a more compact and less deformed packing structure, which ultimately drives the structure of the subsequent layers. The evidence for the different structural conformations determined by the degree of hydrophobicity of the interface provides new knowledge, which is essential for the development of further applications. The key role of hydrophobic interactions in driving adsorption and interfacial behavior was also confirmed by fluid AFM experiments which visualized adherence of the nanogels to SiC8 modified surfaces.

Hard, Soft, and Hard-and-Soft Drug Delivery Carriers Based on CaCO3 and Alginate Biomaterials: Synthesis, Properties, Pharmaceutical Applications

Because free therapeutic drug molecules often have adverse effects on normal tissues, deliver scanty drug concentrations and exhibit a potentially low efficacy at pathological sites, various drug carriers have been developed for preclinical and clinical trials. Their physicochemical and toxicological properties are the subject of extensive research. Inorganic calcium carbonate particles are promising candidates as drug delivery carriers owning to their hardness, porous internal structure, high surface area, distinctive pH-sensitivity, low degradability, etc, while soft organic alginate hydrogels are also widely used because of their special advantages such as a high hydration, bio-adhesiveness, and non-antigenicity. Here, we review these two distinct substances as well as hybrid structures encompassing both types of carriers. Methods of their synthesis, fundamental properties and mechanisms of formation, and their respective applications are described. Furthermore, we summarize and compare similarities versus differences taking into account unique advantages and disadvantages of these drug delivery carriers. Moreover, rational combination of both carrier types due to their performance complementarity (yin-&yang properties: in general, yin is referred to for definiteness as hard, and yang is broadly taken as soft) is proposed to be used in the so-called hybrid carriers endowing them with even more advanced properties envisioned to be attractive for designing new drug delivery systems.

Modification of Surfaces with Vaterite CaCO3 Particles

Former studies have demonstrated a strong interest toward the crystallization of CaCO₃ polymorphs in solution. Nowadays, CaCO₃ crystallization on solid surfaces is extensively being studied using biomolecules as substrates for the control of the growth aiming at various applications of CaCO₃. Calcium carbonate exists in an amorphous state, as three anhydrous polymorphs (aragonite, calcite and vaterite), and as two hydrated polymorphs (monohydrocalcite and ikaite). The vaterite polymorph is considered as one of the most attractive forms due to its large surface area, biocompatibility, mesoporous nature, and other features. Based on physical or chemical immobilization approaches, vaterite can be grown directly on solid surfaces using various (bio)molecules, including synthetic polymers, biomacromolecules such as proteins and peptides, carbohydrates, fibers, extracellular matrix components, and even biological cells such as bacteria. Herein, the progress on the modification of solid surfaces by vaterite CaCO₃ crystals is reviewed, focusing on main findings and the mechanism of vaterite growth initiated by various substances mentioned above, as well as the discussion of the applications of such modified surfaces.

All-in-One Theranostic Platform Based on Hollow Microcapsules for Intragastric-Targeting Antiulcer Drug Delivery, CT Imaging, and Synergistically Healing Gastric Ulcer

Bismuth-containing therapies are suggested as first-line and rescue alternatives for gastric ulcer (GU) treatment and Helicobacter pylori eradication. The current treatment strategy is called quadruple therapy and includes proton pump inhibitors, bismuth, and two broad-band antibiotics. This fact may affect medication compliance, leading to a resistance rate of more than 25% to clarithromycin or metronidazole. To counter this, from the perspective of natural products, an intragastric-targeting all-in-one theranostic platform is established: a drug carrier microcapsule composed of multiple synergistic antiulcer drugs, including bismuth, gallotannin, and antibiotics is obtained (BiG@MCs), and the therapeutic effects of BiG@MCs in rodent models are further evaluated. The results show that the BiG@MCs are spherical with homogeneous particle size (3 ± 0.5 µm) and can be response-released to the acidic environment of the stomach (pH 2.0-3.0), preventing the premature release of the BiG@MCs in physiological conditions. It is worth noting that the bismuth component can be easily identified by computed tomography and other detection instruments, which provide the possibility for drug tracing. In summary, these results indicate that BiG@MCs provide a versatile intragastric-targeting drug delivery platform for GU therapeutics.

A Nanocrystal Platform Based on Metal-Phenolic Network Wrapping for Drug Solubilization

The preparation of drugs into nanocrystals represents a practical pharmaceutical technology to solubilize poorly water-soluble drugs and enhance bioavailability. However, commonly used stabilizers in nanocrystals like polymers and surfactants are frequently inefficient and cannot stabilize nanocrystals for an expected time. This study reports an exquisite platform for nanocrystal production based on a metal-phenolic network (MPN). MPN-wrapped nanocrystal particles (MPN-NPs) were fabricated through an anti-solvent precipitation method using tannic acid and Fe^III or Al^III as coupling agents and characterized by dynamic light scattering, transmission electron microscope, ultraviolet and visible spectrophotometry, fourier-transform infrared spectroscopy, and X-ray powder diffraction. In vitro release, cytotoxicity, and stability were mainly studied with MPN-NPs loading paclitaxel. The suitability of MPN as a nanocrystal stabilizer was also investigated for other classical hydrophobic drugs, including simvastatin, andrographolide, atorvastatin calcium, ferulic acid, and famotidine. The results showed that MPN could effectively wrap and stabilize various drug nanocrystals apart from famotidine. The maximum solubilization of MPN towards atorvastatin calcium was up to 1587 folds, and it also exhibited an excellent solubilizing effect on other hydrophobic drugs. We disclosed that the drug was entrapped in MPN in the nanocrystal form, and there were distinct physiochemical interactions between MPN and the payload. Our findings suggested that MPN may be a promising platform for nanocrystal production to address the challenge of low solubility associated with hydrophobic drugs. Graphical abstract.

Calcium carbonate carriers for combined chemo- and radionuclide therapy of metastatic lung cancer

Considering the clinical limitations of individual approaches against metastatic lung cancer, the use of combined therapy can potentially improve the therapeutic effect of treatment. However, determination of the appropriate strategy of combined treatment can be challenging. In this study, combined chemo- and radionuclide therapy has been realized using radionuclide carriers (¹⁷⁷Lu-labeled core-shell particles, ¹⁷⁷Lu-MPs) and chemotherapeutic drug (cisplatin, CDDP) for treatment of lung metastatic cancer. The developed core-shell particles can be effectively loaded with ¹⁷⁷Lu therapeutic radionuclide and exhibit good radiochemical stability for a prolonged period of time. In vivo biodistribution experiments have demonstrated the accumulation of the developed carriers predominantly in lungs. Direct radiometry analysis did not reveal an increased absorbance of radiation by healthy organs. It has been shown that the radionuclide therapy with ¹⁷⁷Lu-MPs in mono-regime is able to inhibit the number of metastatic nodules (untreated mice = 120 ± 12 versus¹⁷⁷Lu-MPs = 50 ± 7). The combination of chemo- and radionuclide therapy when using ¹⁷⁷Lu-MPs and CDDP further enhanced the therapeutic efficiency of tumor treatment compared to the single therapy (¹⁷⁷Lu-MPs = 50 ± 7 and CDDP = 65 ± 10 versus¹⁷⁷Lu-MPs + CDDP = 37 ± 5). Thus, this work is a systematic research on the applicability of the combination of chemo- and radionuclide therapy to treat metastatic lung cancer.

Transport of Magnetic Polyelectrolyte Capsules in Various Environments

Microcapsules consisting of eleven layers of polyelectrolyte and one layer of iron oxide nanoparticles were fabricated. Two types of nanoparticles were inserted as one of the layers within the microcapsule’s walls: Fe2O3, ferric oxide, having a mean diameter (Ø) of 50 nm and superparamagnetic Fe3O4 having Ø 15 nm. The microcapsules were suspended in liquid environments at a concentration of 108 caps/mL. The suspensions were pumped through a tube over a permanent magnet, and the accumulation within a minute was more than 90% of the initial concentration. The design of the capsules, the amount of iron embedded in the microcapsule, and the viscosity of the transportation fluid had a rather small influence on the accumulation capacity. Magnetic microcapsules have broad applications from cancer treatment to molecular communication.

Overcoming the obstacles of current photodynamic therapy in tumors using nanoparticles

Photodynamic therapy (PDT) has been applied in clinical treatment of tumors for a long time. However, insufficient supply of pivotal factors including photosensitizer (PS), light, and oxygen in tumor tissue dramatically reduces the therapeutic efficacy of PDT. Nanoparticles have received an influx of attention as drug carriers, and recent studies have demonstrated their promising potential to overcome the obstacles of PDT in tumor tissue. Physicochemical optimization for passive targeting, ligand modification for active targeting, and stimuli-responsive release achieved efficient delivery of PS to tumor tissue. Various trials using upconversion NPs, two-photon lasers, X-rays, and bioluminescence have provided clues for efficient methods of light delivery to deep tissue. Attempts have been made to overcome unfavorable tumor microenvironments via artificial oxygen generation, Fenton reaction, and combination with other chemical drugs. In this review, we introduce these creative approaches to addressing the hurdles facing PDT in tumors. In particular, the studies that have been validated in animal experiments are preferred in this review over proof-of-concept studies that were only performed in cells.

The Optimized Delivery of Triterpenes by Liposomal Nanoformulations: Overcoming the Challenges

The last decade has witnessed a sustained increase in the research development of modern-day chemo-therapeutics, especially for those used for high mortality rate pathologies. However, the therapeutic landscape is continuously changing as a result of the currently existing toxic side effects induced by a substantial range of drug classes. One growing research direction driven to mitigate such inconveniences has converged towards the study of natural molecules for their promising therapeutic potential. Triterpenes are one such class of compounds, intensively investigated for their therapeutic versatility. Although the pharmacological effects reported for several representatives of this class has come as a well-deserved encouragement, the pharmacokinetic profile of these molecules has turned out to be an unwelcomed disappointment. Nevertheless, the light at the end of the tunnel arrived with the development of nanotechnology, more specifically, the use of liposomes as drug delivery systems. Liposomes are easily synthesizable phospholipid-based vesicles, with highly tunable surfaces, that have the ability to transport both hydrophilic and lipophilic structures ensuring superior drug bioavailability at the action site as well as an increased selectivity. This study aims to report the results related to the development of different types of liposomes, used as targeted vectors for the delivery of various triterpenes of high pharmacological interest.

Effect of the stiffness of one-layer protein-based microcapsules on dendritic cell uptake and endocytic mechanism

Microcapsules are one of the most promising microscale drug carriers due to their facile fabrication, excellent deformability, and high efficacy in drug storage and delivery. Understanding the effects of their physicochemical properties (size, shape, rigidity, charge, surface chemistry, etc.) on both in vitro and in vivo performance is not only highly significant and interesting but also very challenging. Stiffness, an important design parameter, has been extensively explored in recent years, but how the rigidity of particles influences cellular internalization and uptake mechanisms remains controversial. Here, one-layered lysozyme-based microcapsules with well-controlled stiffness (modulus ranging from 3.49 ± 0.18 MPa to 26.14 ± 1.09 MPa) were prepared and used to investigate the effect of stiffness on the uptake process in dendritic cells and the underlying mechanism. The cellular uptake process and endocytic mechanism were investigated with laser scanning confocal microscopy, mechanism inhibitors, and pathway-specific antibody staining. Our data demonstrated that the stiffness of protein-based microcapsules could be a strong regulator of intracellular uptake and endocytic kinetics but had no obvious effect on the endocytic mechanism. We believe our results will provide a basic understanding of the intracellular uptake process of microcapsules and the endocytic mechanism and inspire strategies for the further design of potential drug delivery microcarriers.

Insight into the mechanism and formation process of bioinspired poly(amino acid)/polyphenol capsules engineered with fast pH switchable permeability

Capsules have hollow cores and closed wall structures, and they have attracted considerable interest due to their wide applications and significance in life science. The engineering process of bioinspired capsules and related applications have earned heavy concerns. However, the mechanism of capsule formation is often ignored. Herein, based on polyornithine (POR) and tannic acid (TA), two facile strategies to engineer bioinspired capsules were proposed, and the formation mechanisms were deeply explored. We found that the oxidized state of TA had a profound influence not on the thickness or permeability of the formed capsule but on the mechanism and generation process. Compared to TA/POR capsules produced from TA without oxidization (TA/POR), capsules produced from TA with preoxidization (oTA/POR) had thicker shells with higher impermeability. The dominant construction mode in the shells of TA/POR capsules was electrostatic interactions but became Schiff base bonds in oTA/POR capsules. The permeability of oTA/POR displayed pH reversibility and strong pH dependence, with 100% permeability at lower pH and 100% impermeability at pH 7, completing loading/releasing kinetics in minutes at pH 4. We believe these findings contribute to knowledge of bioinspired capsules from engineering processes and formation mechanisms, extending their applications in various fields, such as in drug delivery, artificial cells, and sensors.

Polyelectrolyte Multi-Layered Griseofulvin Nanoparticles: Conventional versus Continuous In-Situ Layer-by-Layer Fabrication

Polyelectrolyte multilayers are promising drug carriers with potential applications in the delivery of poorly soluble drugs. Furthermore, the polyelectrolyte multilayer contributes towards electrostatic interactions, which enhances the physical and chemical stability of colloids when compared to those prepared by other approaches. The aim of this work was to generate a polyelectrolyte multilayer on well characterised nanoparticles of the poorly water-soluble drug, griseofulvin. Griseofulvin (GF) nanoparticles (300 nm) were produced by wet bead milling, bearing a negative surface charge due to the use of poly(sodium 4-styrenesulfonate) (PSS) as a stabiliser. Six further layers of alternating chitosan and PSS polyelectrolyte multilayer were successfully generated at the particle surface either via use of: (1) the conventional method of adding excess coating polymer followed by centrifugation, or (2) the continuous in situ approach of adding sufficient amount of coating polymer. The continuous in situ method was designed de novo by the consecutive addition of polymers under high shear rate mixing. In comparison to the continuous in situ method, the conventional method yielded nanoparticles of smaller size (282 ±9 nm vs. 497 ±34 nm) and higher stability by maintaining its size for 6 months. In conclusion, the parent griseofulvin nanosuspension proved to be a suitable candidate for the polyelectrolyte multilayer fabrication providing an avenue for a bespoke formulation with versatile and potentially enhanced drug delivery properties.

Fabrication of a dual stimuli-responsive magnetic nanohydrogel for delivery of anticancer drugs

A dual stimuli-responsive magnetic nanohydrogel was fabricated as a potent drug delivery system (DDS) for 'smart' treatment of cancer by chemo/hyperthermia approach. For this objective, Fe₃O₄ nanoparticles (NPs) were produced via a co-precipitation approach and then modified by 3-(trimethoxysilyl) propylmethacrylate (MPS) moiety. The modified NPs were copolymerized with N,N'-(dimethylamino)ethyl methacrylate (DMAEMA), and maleic anhydride (MA) monomers by a free radical polymerization approach to afford a Fe₃O₄@P(DMAEMA-co-MA) core-shell NPs. Afterward, the NPs were shell crosslinked by the reaction of anhydride unites with neutralized cystamine (Cys). The fabricated pH- and reduction-responsive magnetic nanohydrogel was physically loaded with methotrexate (MTX), as an anticancer drug, and its drug loading efficiency (LE) was calculated as 64 ± 2.7%. The developed nanohydrogel/MTX exhibited proper stimuli-triggered drug release behavior that qualified it as an efficient DDS according to the abnormal micro-environment of cancerous tumors. The anticancer activity investigation using chemo/hyperthermia therapy approach by MTT-assay revealed that the nanohydrogel/MTX might show better clinical outcomes than those of the free MTX.

pH-Responsive Capsule Polymer Particles Prepared by Interfacial Photo-Cross-Linking: Effect of the Alkyl Chain Length of the pH-Responsive Monomer

pH-responsive capsule particles have immense potential for use in various advanced fields, such as microreactors and drug delivery. Moreover, the interfacial photo-cross-linking of spherical polymer particles is a promising strategy to create various functional capsule particles. In this study, pH-responsive capsule polymer particles were prepared by interfacial photo-cross-linking with photo-reactive polymers possessing different pH-responsive monomer units of different alkyl chain lengths, namely, 2-dimethylaminoethyl methacrylate, 2-diethylaminoethyl methacrylate, and 2-diisopropylaminoethyl methacrylate. Using these different pH-responsive monomers, regulation of the controlled release properties of pH-responsive capsule particles was achieved. All capsule particles prepared from these three different polymers released encapsulated molecules under acidic conditions; however, more acidic conditions were necessary for releasing encapsulated molecules with the increasing alkyl chain length. The afforded results indicated that pH-responsive monomers of different alkyl chain lengths could be successfully employed to regulate the pH-responsive controlled release property of the capsule particles prepared by interfacial photo-cross-linking.

Recent Progress of Layer-by-layer Assembly, Free-Standing Film and Hydrogel Based on Polyelectrolytes

Nowadays, polyelectrolytes play an essential role in the development of new materials. Their use allows creating new properties of materials and surfaces and vary them in a wide range. Basically, modern methods are divided into three areas-the process of layer-by-layer deposition, free-standing films, and hydrogels based on polyelectrolytes. Layer-by-layer assembly of polyelectrolytes on various surfaces is a powerful technique. It allows giving surfaces new properties, for example, protect them from corrosion. Free-standing films are essential tools for the design of membranes and sensors. Hydrogels based on polyelectrolytes have recently shown their applicability in electrical and materials science. The creation of new materials and components with controlled properties can be achieved using polyelectrolytes. This review focuses on new technologies that have been developed with polyelectrolytes over the last five years.

pH-Responsive Chitosan/Alginate Polyelectrolyte Complexes on Electrospun PLGA Nanofibers for Controlled Drug Release

The surface functionalization of electrospun nanofibers allows for the introduction of additional functionalities while at the same time retaining the membrane properties of high porosity and surface-to-volume ratio. In this work, we sequentially deposited layers of chitosan and alginate to form a polyelectrolyte complex via layer-by-layer assembly on PLGA nanofibers to introduce pH-responsiveness for the controlled release of ibuprofen. The deposition of the polysaccharides on the surface of the fibers was revealed using spectroscopy techniques and ζ-potential measurements. The presence of polycationic chitosan resulted in a positive surface charge (16.2 ± 4.2 mV, pH 3.0) directly regulating the interactions between a model drug (ibuprofen) loaded within the polyelectrolyte complex and the layer-by-layer coating. The release of ibuprofen was slowed down in acidic pH (1.0) compared to neutral pH as a result of the interactions between the drug and the coating. The provided mesh acts as a promising candidate for the design of drug delivery systems required to bypass the acidic environment of the digestive tract.