Layer-by-layer adsorption: Factors affecting the choice of substrates and polymers

Multicore, SDS-Based Polyelectrolyte Nanocapsules as Novel Nanocarriers for Paclitaxel to Reduce Cardiotoxicity by Protecting the Mitochondria

The clinical application of paclitaxel (PTX), a widely used anticancer drug, is constrained by cardiac arrhythmias and disruptions in vascular homeostasis. To mitigate the non-specific, high toxicity of PTX towards cardiomyocytes, we propose the application of newly synthesized SDS-based polyelectrolyte multicore nanocapsules. This study aims to verify the hypothesis that SDS-based NCs can mitigate the cytotoxic effects of PTX on cardiac cells and serve as effective nanocarriers for this drug. We investigated two types of multicore NCs with differing polyelectrolyte coatings: poly-L-lysine (PLL) and a combination of PLL with poly-L-glutamic acid (PGA). The cytotoxicity of the formulated nanosystems was evaluated using HL-1 cardiomyocytes. Oxygraphy, flow cytometry, spectrophotometry, spectrofluorimetry, fluorescence microscopy, and RT-PCR were employed to assess disruptions in cardiac cellular homeostasis. Our data revealed that, among the tested NCs, SDS/PLL/PGA/PTX exhibited reduced cardiotoxicity and were better tolerated by HL-1 cardiomyocytes compared to SDS/PLL/PTX or PTX alone. In addition, SDS/PLL/PGA/PTX showed a marginal disruption of mitochondria's homeostasis, and no changes in APT level and intracellular calcium concentrations were observed. These findings underscore the potential of SDS-based multicore nanocarriers in anticancer therapy, particularly due to diminished cardiotoxicity and long-term stability in the biological fluids.

Eco-Friendly Fire-Retardant Coating on Cotton Using Layer by Layer Deposition Technique

Fire hazards are an increasing concern in several high-tech industries of public importance, particularly where textile fabrics are used in abundance. In this study, a novel layer by layer deposition method was utilized to develop a fire-retardant coating on cotton fabric. The method involves a hybrid cationic solution consisting of chitosan and branched polyethyleneimine, while bentonite clay was used as the anionic species. The treated fabric was characterized using SEM, VFT, and attenuated total reflection Fourier transform infrared spectroscopy (FTIR). SEM and EDS profiling confirmed the successful deposition of the (BPEI/CH + BNT) species on the surface of the cotton fabrics. FTIR analysis shows changes in chemical composition between the uncoated and coated samples, as confirmed by modifications in peaks at 3621 cm-1, 1023.3 cm-1, 1631 cm-1, and 614.8 cm-1. Finally, the thermal degradation behavior of pre-coated and post-coated samples was evaluated using thermogravimetric (TGA) analysis within a temperature range of 25 °C~700 °C, where the highest residue of ~19.83% was observed at 700 °C for the D-BPCB-30BL sample, signifying highly improved thermal stability compared to uncoated cotton.

Two-Pronged Attack: Dual Activation of Fat Reduction Using Near-Infrared-Responsive Nanosandwich for Targeted Anti-Obesity Treatment

Excessive fat accumulation and chronic inflammation are two typical characteristics of obesity. AMP-activated protein kinase (AMPK), a master regulator of energy metabolism, is involved in adipogenesis, lipogenesis, and inflammation modulation in adipose tissue (AT). Thus, effective lipid reduction and anti-inflammation through AMPK regulation play vital roles in treating obesity. Herein, an anti-obesity nanosandwich is fabricated through attaching polymetformin (PolyMet) onto photothermal agent black phosphorus nanosheets (BP). PolyMet activates AMPK to inhibit adipogenesis, promote browning, and mitigate AT inflammation by decreasing macrophage infiltration, repolarizing macrophage phenotype, and downregulating pro-inflammatory cytokines. Additionally, BP induces lipolysis and apoptosis of adipocytes and macrophages through a photothermal effect. By further functionalization using hyaluronic acid (HA) and MMP2 substrate-linking P3 peptide-modified HA (P3-HA), an enhanced anti-obesity effect is obtained by dual-targeting of P3 and HA, and HA-mediated CD44 poly-clustering after MMP2 cleavage. Upon laser irradiation, the designed nanosandwich (P3-HA/PM@BP) effectively inhibits obesity development in obese mice, increases M2/M1 ratio in AT, reduces the serum levels of cholesterol/triglyceride and improves insulin sensitivity, exhibiting promising research potential to facilitate the clinical development of modern anti-obesity therapies.

Adsorption of polyelectrolytes in the presence of varying dielectric discontinuity between solution and substrate

We examine the interactions between polyelectrolytes (PEs) and uncharged substrates under conditions corresponding to a dielectric discontinuity between the aqueous solution and the substrate. To this end, we vary the relevant system characteristics, in particular the substrate dielectric constant ɛs under different salt conditions. We employ coarse-grained molecular dynamics simulations with rodlike PEs in salt solutions with explicit ions and implicit water solvent with dielectric constant ɛw = 80. As expected, at low salt concentrations, PEs are repelled from the substrates with ɛs < ɛw but are attracted to substrates with a high dielectric constant due to image charges. This attraction considerably weakens for high salt and multivalent counterions due to enhanced screening. Furthermore, for monovalent salt, screening enhances adsorption for weakly charged PEs, but weakens it for strongly charged ones. Meanwhile, multivalent counterions have little effect on weakly charged PEs, but prevent adsorption of highly charged PEs, even at low salt concentrations. We also find that correlation-induced charge inversion of a PE is enhanced close to the low dielectric constant substrates, but suppressed when the dielectric constant is high. To explore the possibility of a PE monolayer formation, we examine the interaction of a pair of like-charged PEs aligned parallel to a high dielectric constant substrate with ɛs = 8000. Our main conclusion is that monolayer formation is possible only for weakly charged PEs at high salt concentrations of both monovalent and multivalent counterions. Finally, we also consider the energetics of a PE approaching the substrate perpendicular to it, in analogy to polymer translocation. Our results highlight the complex interplay between electrostatic and steric interactions and contribute to a deeper understanding of PE-substrate interactions and adsorption at substrate interfaces with varying dielectric discontinuities from solution, ubiquitous in biointerfaces, PE coating applications, and designing adsorption setups.

Effect of Periodate-Induced Cross-linking on Dual Anticancer Drug Release from Poly(2-isopropyl-2-oxazoline)/Tannic Acid-Based Layer-by-Layer Microparticles

This study reports, first, on the preparation and cross-linking of multilayers composed of poly(2-isopropyl-2-oxazoline-co-ethyleneimine) (PiPOX-PEI) and tannic acid (TA). PiPOX was synthesized by cationic ring-opening polymerization (CROP) and partially hydrolyzed, yielding a random copolymer PiPOX-PEI. It was then coassembled at the surface with TA using the layer-by-layer (LbL) technique. Multilayers were exposed to NaIO4 solution to induce covalent bond formation between PEI units of PiPOX-PEI and TA. Cross-linking with NaIO4 enhanced the stability of the multilayers, especially under basic conditions. Second, the potential of PiPOX-PEI and TA multilayers as a stimuli-responsive dual drug-releasing platform was examined using curcumin (CUR) and doxorubicin (DOX) as model drugs. These drugs were chosen as they can act in a combinatorial manner to increase cell death. The surface of CUR-containing CaCO3 microparticles was modified with PiPOX-PEI and TA multilayers and postloaded with DOX. We found that LbL particles could release DOX in a pH-responsive manner, whereas temperature-induced release was observed only when the temperature was raised above 40 °C. The DOX and CUR released from the LbL particles could act synergistically on HCT-116 cells. Cross-linking increased the DOX release from LbL particles but decreased the CUR release from the core. Corroborating the release data, the synergy observed with the non-cross-linked particles was lost with the cross-linked particles, and the decrease in the viability of HCT-116 cells was attributed mainly to the release of DOX. Overall, we describe here NaIO4-induced cross-linking of PiPOX-PEI/TA LbL films, the effects of pH, temperature, and cross-linking on DOX and CUR release from multilayers, and comparison of the combinatorial effect of DOX and CUR for cross-linked and non-cross-linked LbL microparticles through cell viability assays.

Layer-by-layer assembly of chitosan/alginate thin films containing Salmonella enterica bacteriophages for antibacterial applications

The emergence of antibiotic resistant bacteria and the ineffectiveness of routine treatments inspired development of alternatives to biocides for antibacterial applications. Bacteriophages are natural predators of bacteria and are promising alternatives to antibiotics. This study presents fabrication of a Salmonella enterica bacteriophage containing ultra-thin multilayer film composed of chitosan and alginate and demonstrates its potential as an antibacterial coating for food packaging applications. Chitosan/alginate film was prepared through layer-by-layer (LbL) self-assembly technique. A bacteriophage, which belongs to Siphoviridae morphotype (MET P1-001_43) and infects Salmonella enterica subsp. enterica serovar Enteritidis (Salmonella Enteritidis), was post-loaded into chitosan/alginate film. The LbL growth, stability, and surface morphology of chitosan/alginate film as well as phage deposition into multilayers were analysed through ellipsometry, QCM-D and AFM techniques. The bacteriophage containing multilayers showed antibacterial activity at pH 7.0. In contrast, anti-bacterial activity was not observed at acidic conditions. We showed that wrapping a Salmonella Enteritidis contaminated chicken piece with aluminium foil whose surface was modified with phage loaded chitosan/alginate multilayers decreased the number of colonies on the chicken meat, and it was as effective as treating the meat directly with phage solution.

Overcoming the Low-Stability Bottleneck in the Clinical Translation of Liposomal Pressurized Metered-Dose Inhalers: A Shell Stabilization Strategy Inspired by Biomineralization

Currently, several types of inhalable liposomes have been developed. Among them, liposomal pressurized metered-dose inhalers (pMDIs) have gained much attention due to their cost-effectiveness, patient compliance, and accurate dosages. However, the clinical application of liposomal pMDIs has been hindered by the low stability, i.e., the tendency of the aggregation of the liposome lipid bilayer in hydrophobic propellant medium and brittleness under high mechanical forces. Biomineralization is an evolutionary mechanism that organisms use to resist harsh external environments in nature, providing mechanical support and protection effects. Inspired by such a concept, this paper proposes a shell stabilization strategy (SSS) to solve the problem of the low stability of liposomal pMDIs. Depending on the shell material used, the SSS can be classified into biomineralization (biomineralized using calcium, silicon, manganese, titanium, gadolinium, etc.) biomineralization-like (composite with protein), and layer-by-layer (LbL) assembly (multiple shells structured with diverse materials). This work evaluated the potential of this strategy by reviewing studies on the formation of shells deposited on liposomes or similar structures. It also covered useful synthesis strategies and active molecules/functional groups for modification. We aimed to put forward new insights to promote the stability of liposomal pMDIs and shed some light on the clinical translation of relevant products.

Recent Developments in Layer-by-Layer Assembly for Drug Delivery and Tissue Engineering Applications

Surfaces with biological functionalities are of great interest for biomaterials, tissue engineering, biophysics, and for controlling biological processes. The layer-by-layer (LbL) assembly is a highly versatile methodology introduced 30 years ago, which consists of assembling complementary polyelectrolytes or biomolecules in a stepwise manner to form thin self-assembled films. In view of its simplicity, compatibility with biological molecules, and adaptability to any kind of supporting material carrier, this technology has undergone major developments over the past decades. Specific applications have emerged in different biomedical fields owing to the possibility to load or immobilize biomolecules with preserved bioactivity, to use an extremely broad range of biomolecules and supporting carriers, and to modify the film's mechanical properties via crosslinking. In this review, the focus is on the recent developments regarding LbL films formed as 2D or 3D objects for applications in drug delivery and tissue engineering. Possible applications in the fields of vaccinology, 3D biomimetic tissue models, as well as bone and cardiovascular tissue engineering are highlighted. In addition, the most recent technological developments in the field of film construction, such as high-content liquid handling or machine learning, which are expected to open new perspectives in the future developments of LbL, are presented.

Algae-Based Biopolymers for Batteries and Biofuel Applications in Comparison with Bacterial Biopolymers-A Review

Algae-based biopolymers can be used in diverse energy-related applications, such as separators and polymer electrolytes in batteries and fuel cells and also as microalgal biofuel, which is regarded as a highly renewable energy source. For these purposes, different physical, thermochemical, and biochemical properties are necessary, which are discussed within this review, such as porosity, high temperature resistance, or good mechanical properties for batteries and high energy density and abundance of the base materials in case of biofuel, along with the environmental aspects of using algae-based biopolymers in these applications. On the other hand, bacterial biopolymers are also often used in batteries as bacterial cellulose separators or as biopolymer network binders, besides their potential use as polymer electrolytes. In addition, they are also regarded as potential sustainable biofuel producers and converters. This review aims at comparing biopolymers from both aforementioned sources for energy conversion and storage. Challenges regarding the production of algal biopolymers include low scalability and low cost-effectiveness, and for bacterial polymers, slow growth rates and non-optimal fermentation processes often cause challenges. On the other hand, environmental benefits in comparison with conventional polymers and the better biodegradability are large advantages of these biopolymers, which suggest further research to make their production more economical.

Synergistic Combination of Dual Clays in Multilayered Nanocomposites for Enhanced Flame Retardant Properties

In an effort to reduce the flammability of synthetic polymeric materials such as cotton fabrics and polyurethane foam (PUF), hybrid nanocoatings are prepared by layer-by-layer assembly. Multilayered nanocomposites of a cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDDA), are paired with two kinds of clay nanoplatelets, montmorillonite (MMT) and vermiculite (VMT). The physical properties such as thickness and mass and thermal behaviors in clay-based nanocoatings with and without incorporation of tris buffer are compared to assess the effectiveness of amine salts on flame retardant (FR) performances. A PDDA-tris/VMT-MMT system, in which tris buffer is introduced into the cationic PDDA aqueous solution, produces a thicker and heavier coating. Three different systems, including PDDA/MMT, PDDA/VMT-MMT, and PDDA-tris/VMT-MMT, result in conformal coating, retaining the weave structure of the fabrics after being exposed to a vertical and horizontal flame test, while the uncoated sample is completely burned out. The synergistic effects of dual clay-based hybrid nanocoatings are greatly improved by adding amine salts. Cone calorimetry reveals that the PDDA-tris/VMT-MMT-coated PUF eliminates a second peak heat release rate and significantly reduces other FR performances, compared to those obtained from the clay-based multilayer films with no amine salts added. Ten bilayers of PDDA-tris/VMT-MMT (≈250 nm thick) maintain the shape of foam after exposure to a butane torch flame for 12 s. As for practical use of these nanocomposites in real fire disasters, spray-assisted PDDA-tris/VMT-MMT multilayers on woods exhibit high resistance over flammability. Improved fire resistance in PDDA-tris/VMT-MMT is believed to be due to the enhanced char yield through the addition of tris buffer that promotes the deposition of more clay particles while retaining a highly ordered deposition of a densely packed nanobrick wall structure. This work demonstrates the ability to impart significant fire resistance to synthetic polymer materials in a fully renewable nanocoating that uses environmentally benign chemistry.

Titanium-Dioxide-Nanoparticle-Embedded Polyelectrolyte Multilayer as an Osteoconductive and Antimicrobial Surface Coating

Bioactive surface coatings have retained the attention of researchers and physicians due to their versatility and range of applications in orthopedics, particularly in infection prevention. Antibacterial metal nanoparticles (mNPs) are a promising therapeutic, with vast application opportunities on orthopedic implants. The current research aimed to construct a polyelectrolyte multilayer on a highly porous titanium implant using alternating thin film coatings of chitosan and alginate via the layer-by-layer (LbL) self-assembly technique, along with the incorporation of silver nanoparticles (AgNPs) or titanium dioxide nanoparticles (TiO2NPs), for antibacterial and osteoconductive activity. These mNPs were characterized for their physicochemical properties using quartz crystal microgravimetry with a dissipation system, nanoparticle tracking analysis, scanning electron microscopy, and atomic force microscopy. Their cytotoxicity and osteogenic differentiation capabilities were assessed using AlamarBlue and alkaline phosphatase (ALP) activity assays, respectively. The antibiofilm efficacy of the mNPs was tested against Staphylococcus aureus. The LbL polyelectrolyte coating was successfully applied to the porous titanium substrate. A dose-dependent relationship between nanoparticle concentration and ALP as well as antibacterial effects was observed. TiO2NP samples were also less cytotoxic than their AgNP counterparts, although similarly antimicrobial. Together, these data serve as a proof-of-concept for a novel coating approach for orthopedic implants with antimicrobial and osteoconductive properties.

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.

Biocompatibility and osteoinductive ability of casein phosphopeptide modified polyetheretherketone

Polyetheretherketone (PEEK) is a potential implant material for dental application due to its excellent mechanical properties. However, its biological inertness and poor osteoinductive ability limited its clinical application. Based on a lay-by-layer self-assembly technique, here we incorporated casein phosphopeptide (CPP) onto PEEK surface by a simple two-step strategy to address the poor osteoinductive ability of PEEK implants. In this study, the PEEK specimens were positively charged by 3-ammoniumpropyltriethoxysilane (APTES) modification, then the CPP was adsorbed onto the positively charged PEEK surface electrostatically to obtain CPP-modified PEEK (PEEK-CPP) specimens. The surface characterization, layer degradation, biocompatibility and osteoinductive ability of the PEEK-CPP specimens were studied in vitro. After CPP modification, the PEEK-CPP specimens had a porous and hydrophilic surface and presented enhanced cell adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells. These findings indicated that CPP modification could significantly improve the biocompatibility and osteoinductive ability of PEEK-CPP implants in vitro. In a word, CPP modification is a promising strategy for the PEEK implants to achieve osseointegration.

Unveiling the Assembly of Neutral Marine Polysaccharides into Electrostatic-Driven Layer-by-Layer Bioassemblies by Chemical Functionalization

Marine-origin polysaccharides, in particular cationic and anionic ones, have been widely explored as building blocks in fully natural or hybrid electrostatic-driven Layer-by-Layer (LbL) assemblies for bioapplications. However, the low chemical versatility imparted by neutral polysaccharides has been limiting their assembly into LbL biodevices, despite their wide availability in sources such as the marine environment, easy functionality, and very appealing features for addressing multiple biomedical and biotechnological applications. In this work, we report the chemical functionalization of laminarin (LAM) and pullulan (PUL) marine polysaccharides with peptides bearing either six lysine (K₆) or aspartic acid (D₆) amino acids via Cu(I)-catalyzed azide-alkyne cycloaddition to synthesize positively and negatively charged polysaccharide-peptide conjugates. The successful conjugation of the peptides into the polysaccharide's backbone was confirmed by proton nuclear magnetic resonance and attenuated total reflectance Fourier-transform infrared spectroscopy, and the positive and negative charges of the LAM-K₆/PUL-K₆ and LAM-D₆/PUL-D₆ conjugates, respectively, were assessed by zeta-potential measurements. The electrostatic-driven LbL build-up of either the LAM-D₆/LAM-K₆ or PUL-D₆/PUL-K₆ multilayered thin film was monitored in situ by quartz crystal microbalance with dissipation monitoring, revealing the successful multilayered film growth and the enhanced stability of the PUL-based film. The construction of the PUL-peptide multilayered thin film was also assessed by scanning electron microscopy and its biocompatibility was demonstrated in vitro towards L929 mouse fibroblasts. The herein proposed approach could enable the inclusion of virtually any kind of small molecules in the multilayered assemblies, including bioactive moieties, and be translated into more convoluted structures of any size and geometry, thus extending the usefulness of neutral polysaccharides and opening new avenues in the biomedical field, including in controlled drug/therapeutics delivery, tissue engineering, and regenerative medicine strategies.

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.

Fabrication and Characterization of Eco-Friendly Polyelectrolyte Bilayer Films Based on Chitosan and Different Types of Edible Citrus Pectin

The eco-friendly polyelectrolyte bilayer films were prepared by layer-by-layer (LBL) casting method using chitosan (CS) and four types of edible citrus pectin as film substrates. The results showed that the polyelectrolyte bilayer films exhibited excellent comprehensive properties. Furthermore, the interaction between CS and pectin was closely related to the degree of methyl-esterification (DM), molecular weight (Mw), and zeta potential of pectin. The low DM, Mw, and high zeta potential of the low methyl-esterified pectin (LM) resulted in a denser internal structure of the bilayer film, stronger UV shielding performance, and stronger gas barrier ability. The high DM and Mw of the high methyl-esterified pectin (HM) endow the bilayer film with stronger mechanical properties, thermal stability, and antifogging property. The microstructural and spectroscopic analysis showed that there are hydrogen bonds and electrostatic interactions between the layers. Overall, the developed CS-pectin polyelectrolyte bilayer films provided potential applications for food bioactive packaging.

Current Perspectives on Synthetic Compartments for Biomedical Applications

Nano- and micrometer-sized compartments composed of synthetic polymers are designed to mimic spatial and temporal divisions found in nature. Self-assembly of polymers into compartments such as polymersomes, giant unilamellar vesicles (GUVs), layer-by-layer (LbL) capsules, capsosomes, or polyion complex vesicles (PICsomes) allows for the separation of defined environments from the exterior. These compartments can be further engineered through the incorporation of (bio)molecules within the lumen or into the membrane, while the membrane can be decorated with functional moieties to produce catalytic compartments with defined structures and functions. Nanometer-sized compartments are used for imaging, theranostic, and therapeutic applications as a more mechanically stable alternative to liposomes, and through the encapsulation of catalytic molecules, i.e., enzymes, catalytic compartments can localize and act in vivo. On the micrometer scale, such biohybrid systems are used to encapsulate model proteins and form multicompartmentalized structures through the combination of multiple compartments, reaching closer to the creation of artificial organelles and cells. Significant progress in therapeutic applications and modeling strategies has been achieved through both the creation of polymers with tailored properties and functionalizations and novel techniques for their assembly.

Efficient adsorption of methyl orange and methyl blue dyes by a novel triptycene-based hyper-crosslinked porous polymer

It is still a great challenge to develop new materials for the highly efficient entrapment of organic dyes from aqueous solution. Herein, a novel triptycene-based hyper-crosslinked porous polymer (TPP-PP) was designed and synthesized by a simple Friedel-Crafts reaction. The obtained polymer TPP-PP has a high surface area, abundant pore structure and stable thermal performance. Due to the above characteristics, TPP-PP has good adsorption performance for anionic methyl orange solution (MO) and cationic methyl blue solution (MB). Under the optimal experiment conditions, the TPP-PP showed an excellent adsorption capacity for MO (220.82 mg g-1) and MB (159.80 mg g-1), respectively. The adsorption kinetics fitted the pseudo-second-order model. The adsorption of MO by TPP-PP reaches equilibrium within 180 minutes, and the adsorption of MB reaches equilibrium within 150 minutes. The adsorption behavior was not only spontaneous but also endothermic in reality. At the same time, TPP-PP also has good reusability. After 5 cycles of experiments, the removal rate of MO and MB by TPP-PP can still reach more than 80%. Thus, the Friedel-Crafts reaction crosslinked method might be a promising approach for the synthesis of novel material for the highly efficient extraction of dye wastewater.

Recent advances in polymeric core-shell nanocarriers for targeted delivery of chemotherapeutic drugs

The treatment effect of chemotherapeutics is often impeded by nonspecific biodistribution and limited biocompatibility. Polymeric core-shell nanocarriers (PCS NCs) composed of a polymer core and at least one shell have been widely applied for cancer therapy and have shown great potential in selectively delivering chemotherapeutic drugs to tumor sites. These PCS NCs can effectively ameliorate the delivery efficiency and therapeutic index of anticarcinogens by prolonging drug residence in the bloodstream, enhancing tumor tissue drug penetration, facilitating cellular drug uptake, controlling the spatiotemporal release of payloads, or codelivering two or more bioactive agents. This review summarizes recently published literature on using PCS NCs to transport chemotherapeutic drugs with poor aqueous solubility and discusses their design principles, structural features, functional properties, and potential limitations.

Wetting-Induced Polyelectrolyte Pore Bridging

Active layers of ion separation membranes often consist of charged layers that retain ions based on electrostatic repulsion. Conventional fabrication of these layers, such as polyelectrolyte deposition, can in some cases lead to excess coating to prevent defects in the active layer. This excess deposition increases the overall membrane transport resistance. The study at hand presents a manufacturing procedure for controlled polyelectrolyte complexation in and on porous supports by support wetting control. Pre-wetting of the microfiltration membrane support, or even supports with larger pore sizes, leads to ternary phase boundaries of the support, the coating solution, and the pre-wetting agent. At these phase boundaries, polyelectrolytes can be complexated to form partially freestanding selective structures bridging the pores. This polyelectrolyte complex formation control allows the production of membranes with evenly distributed polyelectrolyte layers, providing (1) fewer coating steps needed for defect-free active layers, (2) larger support diameters that can be bridged, and (3) a precise position control of the formed polyelectrolyte multilayers. We further analyze the formed structures regarding their position, composition, and diffusion dialysis performance.

Polyelectrolyte Multilayers: An Overview on Fabrication, Properties, and Biomedical and Environmental Applications

Polyelectrolyte multilayers are versatile materials that are used in a large number of domains, including biomedical and environmental applications. The fabrication of polyelectrolyte multilayers using the layer-by-layer technique is one of the simplest methods to obtain composite functional materials. The properties of the final material can be easily tuned by changing the deposition conditions and the used building blocks. This review presents the main characteristics of polyelectrolyte multilayers, the fabrication methods currently used, and the factors influencing the layer-by-layer assembly of polyelectrolytes. The last section of this paper presents some of the most important applications of polyelectrolyte multilayers, with a special focus on biomedical and environmental applications.

Synergistic combination therapy of lung cancer using lipid-layered cisplatin and oridonin co-encapsulated nanoparticles

Lung cancer treatment using cisplatin (DDP) in combination with other drugs are effective for the treatment of non-small cell lung cancer (NSCLC). The aim of this study was to prepare a layer-by-layer nanoparticles (NPs) for the co-loading of DDP and oridonin (ORI) and to evaluate the antitumor activity of the system in vitro and in vivo. Novel DDP and ORI co-loaded layer-by-layer NPs (D/O-NPs) were constructed. The mean diameter, surface change stability and drug release behavior of NPs were evaluated. In vitro cytotoxicity of D/O-NPs was investigated against DDP resistant human lung cancer cell line (A549/DDP cells), and in vivo anti-tumor efficiency of D/O-NPs was tested on mice bearing A549/DDP cells xenografts. D/O-NPs have a diameter of 139.6 ± 4.4 nm, a zeta potential value of +13.8 ± 1.6 mV. D/O-NPs could significantly enhance in vitro cell toxicity and in vivo antitumor effect against A549/DDP cells and lung cancer animal model compared to the single drug loaded NPs and free drugs. The results demonstrated that the D/O-NPs could be used as a promising lung cancer treatment system.

Alcalase Microarray Base on Metal Ion Modified Hollow Mesoporous Silica Spheres as a Sustainable and Efficient Catalysis Platform for Proteolysis

The industrial exploitation of protease is limited owing to its sensitivity to environmental factors and autolysis during biocatalytic processes. In the present study, the alcalase microarray (Bacillus licheniformis, alcalase@HMSS-NH₂-Metal) based on different metal ions modified hollow mesoporous silica spheres (HMSS-NH₂-Metal) was successfully developed via a facile approach. Among the alcalase@HMSS-NH₂-Metal (Ca²⁺, Zn²⁺, Fe³⁺, Cu²⁺), the alcalase@HMSS-NH₂-Fe³⁺ revealed the best immobilization efficiency and enzymatic properties. This tailor-made nanocomposite immobilized alcalase on a surface-bound network of amino-metal complex bearing protein-modifiable sites via metal-protein affinity. The coordination interaction between metal ion and alcalase advantageously changed the secondary structure of enzyme, thus significantly enhanced the bioactivities and thermostability of alcalase. The as-prepared alcalase@HMSS-NH₂-Fe³⁺ exhibited excellent loading capacity (227.8 ± 23.7 mg/g) and proteolytic activity. Compared to free form, the amidase activity of alcalase microarray increased by 5.3-fold, the apparent kinetic constant V_max/K_m of alcalase@HMSS-NH₂-Fe³⁺ (15.6 min⁻¹) was 1.9-fold higher than that of free alcalase, and the biocatalysis efficiency increased by 2.1-fold for bovine serum albumin (BSA) digestion. Moreover, this particular immobilization strategy efficiently reduced the bioactivities losses of alcalase caused by enzyme leaking and autolysis during the catalytic process. The alcalase microarray still retained 70.7 ± 3.7% of the initial activity after 10 cycles of successive reuse. Overall, this study established a promising strategy to overcome disadvantages posed by free alcalase, which provided new expectations for the application of alcalase in sustainable and efficient proteolysis.

Thin and Flexible Ion Sensors Based on Polyelectrolyte Multilayers Assembled onto the Carbon Adhesive Tape

A novel flexible ion-selective sensor for potassium and sodium detection was proposed. Flexible ion-selective electrodes with pseudo-liquid internal solution on contrary to the system with a solid contact provided a more stable analytical signal. Such advantages were achieved because of polyelectrolyte (PEI/PSS) layers adsorption on the conduct substrate with a layer-by-layer technique. Such an approach demonstrated that ion-selective electrodes save sensitivity with Nernstian dependence: 56.2 ± 1.4 mV/dec a _Na⁺ and 56.3 ± 1.9 mV/dec a _K⁺ , as well as a fast time of response for potassium (5 s) and sodium (8 s) was shown. The sensing platform proposed demonstrates a better time of response and is close to the Nernstian value of sensitivity with a sensor low cost. The results proposed confirm a pseudo-liquid junction for the ion-selective electrode. Biocompatibility of an ion-selective sensing platform was demonstrated at potassium potentiometric measurements in Escherichia coli biofilms. Potassium levels in a biofilm were measured with potentiometry and showed agreement with the previous results.

Layer-by-layer assembly of nanofilms to control cell functions

Control of cell functions by layer-by-layer assembly has a great challenge in tissue engineering and biomedical applications. We summarize current hot approaches in this review.