Layer-by-layer Research Articles

Preparation and properties of liquid-core yogurt balls by layer-by-layer assembly of edible packaging materials

Abstract To address the issue of yogurt adhering to the inner walls of packaging, resulting in resource wastage, a controllable particle size of alginate-calcium yogurt liquid core ball (LC-Yoba) was prepared using a mold-reverse spherification method. The effectiveness of layer-by-layer (LBL) assembly techniques in enhancing the performance of LC-Yoba was investigated. The results showed that a multilayer structure composed of beeswax-chitosan (BW-CS) was successfully assembled on the surface of LC-Yoba, wherein the number of assembly layers significantly impacts its performance. Compared with the unassembled LC-Yoba, the bursting force of the assembled three layers of LC-Yoba increased by 194.67 %, the elasticity increased by 19.76 %, and the weight loss rate decreased by 86.58 %. In addition, the appearance of the three layers of LC-Yoba and the pH, acidity, and water holding capacity of the yogurt were maintained in a stable state within 72 h at room temperature.

Versatile MOF-based nanofibrous heterostructures for engineering the CO2 photoreduction activity and selectivity: From CO to C2H5OH

Photocatalytic CO2 reduction is a potential promising strategy for eliminating the global energy crisis and environmental issue. However, the complex reduction pathway leads to multiple possible products with limited efficiency, representing a great barrier for the further development. Herein, we report a Metal-organic framework (MOF) based heterostructure model for the efficient photoreduction of CO2 with full controllable product selectivity between CO and C2H5OH. Novel core-sheath like MOF@TiO2 heterostructures could be efficiently prepared by the layer-by-layer (LBL) growth of HKUST-1 onto Cu-embedded TiO2 nanofibers (NFs), affording covalent heterointerfaces for efficient S-scheme charge separation and promising potential in photocatalytic activity regulation. By improving the CO2 capture and retention via in situ amino-functionalization of HKUST-1, the photocatalytic CO production rate could be greatly promoted from 8.76 ± 0.84 to 43.46 ± 0.86 μmol g−1h−1 accompanied by an enhancement of selectivity from 91.7 % to 98.3 %. Moreover, the product could be efficiently engineered into ethanol with a C2 product selectivity of 94.2 % by introducing Cu nanoparticles (NPs) as the additional CC coupling site. The in situ FT-IR and DFT calculations reveal the mechanistic process and decisive role of amino-functionalization and Cu NPs deposition in photocatalytic activity engineering. This work highlights the key factors and significance of fabricating MOFs based heterostructures with tunable photocatalytic activity for achieving CO2 neutralization.

Construction of durable, multifunctional superhydrophobic wood surface via ɛ-polylysine/PDMS/wax treatment

In addressing the limitations of wood's susceptibility to water and moisture, this study explored the development of a durable, superhydrophobic surface through a novel ɛ-polylysine/polydimethylsiloxane (PDMS)/wax composite system. Leveraging the layer-by-layer (LBL) assembly, the incorporation of cationic ɛ-polylysine not only improved the adherence of PDMS and wax to the wood surface through electrostatic attraction but also facilitated a more uniform distribution, achieving optimal hydrophobicity at a ɛ-polylysine concentration of 2 g/L. The synergistic effect of the wood's natural rough structure and the deposition of these hydrophobic substances endowed the treated wood with superhydrophobic properties, showcasing exceptional self-cleaning capabilities by efficiently repelling a variety of liquid contaminants. Durability assessments through sandpaper abrasion, chemical exposure, and accelerated weathering tests confirmed the enhanced long-term stability of the treated wood surfaces. Furthermore, the incorporation of ε-polylysine provided nice antimicrobial properties, showing a substantial reduction in bacterial adhesion. The ε-polylysine/PDMS/wax composite system represents a significant advancement in the development of multifunctional wood surfaces, promising broader applications in sustainable building materials, furniture, and packaging solutions.

Single-Walled Carbon Nanotube-Modified Gold Leaf Immunosensor for Escherichia coli Detection.

The requirement to prevent foodborne illnesses underscores the need for reliable detection tools, stimulating biosensor technology with practical solutions for in-field applications. This study introduces a low-cost immunosensor based on a single-walled carbon nanotube (SWCNT)-modified gold leaf electrode (GLE) for the sensitive detection of Escherichia coli. The immunosensor is realized with a layer-by-layer (LbL) assembly technique, creating an electrostatic bond between positively charged polyethylenimine (PEI) and negatively charged carboxyl-functionalized SWCNTs on the GLE. The structural and functional characterization of the PEI-SWCNT film was performed with Raman spectroscopy, high-resolution scanning electron microscopy (HRSEM), and electrical measurements. The PEI-SWCNT film was used as a substrate for antibody immobilization, and the electrochemical sensing potential was validated using electrochemical impedance spectroscopy (EIS). The results showed a wide dynamic range of E. coli detection, 101-108 cfu/mL, with a limit of detection (LOD) of 1.6 cfu/mL in buffer and 15 cfu/mL in the aqueous solution used for cleansing fresh lettuce leaves, affirming its efficiency as a practical and affordable tool in enhancing food safety.

Development of high barrier poly(l-actic acid)/chitosan/graphene oxide flexible films for meat packaging by layer-by-layer

An new high-barrier packaging films for meat preservation were obtained by depositing graphene oxide (GO) layer-by-layer (LbL) on poly(l-lactic acid)(PLLA)-poly (butylene itaconate) (PBI) copolymers (PLBI) with chitosan (CS) as bonding layer in this study. The 1H NMR results revealed that PLBI copolymer was successful synthesized. The introduction of PBI reduced the Tg and crystallization capacity of PLLA film, which made the copolymer films exhibit extremely high flexibility (up to 186.1% elongation at break). The film also exhibited high hydrophilicity, which was favorable for the effective attachment of CS. With CS as an intermediate layer, the FTIR and SEM results showed that the GO was evenly distributed onto the PLBI film surface due to the electrostatic interaction. The oxygen, water vapor and UV light barrier properties of PLBI/CS/(GO-CS)x films were improved and increased with the GO-CS layers. The PLBI/CS/(GO-CS)10 films, with extremely low oxygen permeability coefficients about 0.4 × 10−8 cm3 m/m2·h·Pa, delayed the increase in weight loss, hardness, pH, TVB-N, TBARS, and total viable counts of chilled meat during storage. It also decreased the discoloration, and loss of springness and cohesiveness of chilled meat caused by long-term refrigeration. The LbL films even showed better freshness-keeping effect than commercial PA/PE films due to its superior barrier and certain antibacterial properties, suggesting great potential application in fresh meat preservation.

Layer-by-Layer Assembly of Renal-Targeted Polymeric Nanoparticles for Robust Arginase-2 Knockdown and Contrast-Induced Acute Kidney Injury Prevention.

The mitochondrial enzyme arginase-2 (Arg-2) is implicated in the pathophysiology of contrast-induced acute kidney injury (CI-AKI). Therefore, Arg-2 represents a candid target for CI-AKI prevention. Here, layer-by-layer (LbL) assembled renal-targeting polymeric nanoparticles are developed to efficiently deliver small interfering RNA (siRNA), knockdown Arg-2 expression in renal tubules, and prevention of CI-AKI is evaluated. First, near-infrared dye-loaded poly(lactic-co-glycolic acid) (PLGA) anionic cores are electrostatically coated with cationic chitosan (CS) to facilitate the adsorption and stabilization of Arg-2 siRNA. Next, nanoparticles are coated with anionic hyaluronan (HA) to provide protection against siRNA leakage and shielding against early clearance. Sequential electrostatic layering of CS and HA improves loading capacity of Arg-2 siRNA and yields LbL-assembled nanoparticles. Renal targeting and accumulation is enhanced by modifying the outermost layer of HA with a kidney targeting peptide (HA-KTP). The resultant kidney-targeting and siRNA loaded nanoparticles (PLGA/CS/HA-KTP siRNA) exhibit proprietary accumulation in kidneys and proximal tubular cells at 24 h post-tail vein injection. In iohexol-induced in vitro and in vivo CI-AKI models, PLGA/CS/HA-KTP siRNA delivery alleviates oxidative and nitrification stress, and rescues mitochondrial dysfunction while reducing apoptosis, thereby demonstrating a robust and satisfactory therapeutic effect. Thus, PLGA/CS/HA-KTP siRNA nanoparticles offer a promising candidate therapy to protect against CI-AKI.

Layer-by-layer Assembly of Nanosheets with Matching Size and Shape for More Stable Membrane Structure than Nanosheet-Polymer Assembly.

Layer-by-layer (LbL) assembly of oppositely charged materials has been widely used as an approach to make two-dimensional (2D) nanosheet-based membranes, which often involves 2D nanosheets being alternately deposited with polymer-based polyelectrolytes to obtain an electrostabilized nanosheet-polymer structure. In this study, we hypothesized that using 2D nanosheets with matching physical properties as both polyanions and polycations may result in a more ordered nanostructure with better stability than a nanosheet-polymer structure. To compare the differences between nanosheet-nanosheet vs nanosheet-polymer structures, we assembled negatively charged molybdenum disulfide nanosheets (MoS2) with either positively charged graphene oxide (PrGO) nanosheets or positively charged polymer (PDDA). Using combined measurements by ellipsometer and quartz crystal microbalance with dissipation, we discovered that the swelling of MoS2-PrGO in ionic solutions was 60% lower than that of MoS2-PDDA membranes. Meanwhile, the MoS2-PrGO membrane retained its permeability upon drying, whereas the permeability of MoS2-PDDA decreased by 40% due to the restacking of MoS2. Overall, the MoS2-PrGO membrane demonstrated a better filtration performance. Additionally, our X-ray photoelectron spectroscopy results and analysis on layer density revealed a clearer transition in material composition during the LbL synthesis of MoS2-PrGO membranes, and the X-ray diffraction pattern suggested its resemblance to an ordered, layer-stacked structure. In conclusion, the MoS2-PrGO membrane made with nanosheets with matching size, shape, and charge density exhibited a much more aligned stacking structure, resulting in reduced membrane swelling under high salinity solutions, controlled restacking, and improved separation performance.

Influence of density and chemical additives on paper mechanical properties

In this work we have investigated the effect of surface modification of fibres on the overall mechanical properties of high-density papers. Paper sheets were prepared by a combination of heat-pressing and polyelectrolyte Layer-by-Layer (LbL) modification of different softwood fibres. LbLs of Polyallylamine Hydrochloride (PAH) and Hyaluronic Acid (HA) were adsorbed onto unbleached kraft fibres and bleached Chemo-ThermoMechanical Pulp (CTMP) to improve the strength of the fibre–fibre joints in papers made from these fibres. Additionally, different sheet-making procedures were used to prepare a range of network densities with different degrees of fibre–fibre interaction in the system. The results demonstrate that interfacial adhesion within fibre–fibre joints plays a pivotal role in the network's performance, even at higher paper densities. Hygroexpansion measurements and fracture zone imaging with Scanning Electron Microscopy (SEM) further support the claim that stronger interactions between the fibres allow for a better utilisation of the inherent fibre properties. Surface treatments and network densification significantly improved the paper sheets' mechanical properties. Specifically, LbL-treatments alone increased specific stiffness up to 60% and specific strength by over 100%. This improvement is linked to the build-up of residual stresses during drying. Due to a high interaction between the fibres during water removal the fibres become constrained, leading to increased stretching of fibre segments. Strengthened fibre joints intensify this constraint, further increasing the stretch and, consequently, the paper's strength.

Construction of oleogels based on emulsion gels stabilized by glycyrrhizic acid and chitosan

Liquid oils can be converted into elastic solids by preparing oleogels using an emulsion-templated approach. In this study, we prepared emulsion gels using a layer-by-layer (LBL) electrostatic deposition approach. These emulsion gels were then used as templates to prepare oleogels. Initially, oil-in-water emulsion gels were formed using glycyrrhizic acid (GA) as a natural anionic surfactant to form and stabilize the oil droplets. Cationic chitosan (CS) was then added to these emulsions to form a biopolymer coating around the oil droplets. The GA/CS ratio in these emulsion gels played a critical role in determining the physical stability of the oleogels created from them. At a sufficiently high chitosan concentration (3% CS for samples with 1% GA, 2% CS for samples with 2% GA), the emulsion gels were resistant to destabilization during drying, which was attributed to the formation of a thick chitosan coating around the oil droplets. The oil loss from the optimized oleogels (GCOs1-3, GCOs2-2, GCOs2-3) during drying was relatively low (0.41%–1.08%), indicating their strong oil binding capacity. In contrast, non-optimized oleogels (2% GA, 1% CS) were prone to droplet coalescence and oil loss (74.2% ± 1.3%) during drying. The optimized oleogels (GCOs1-3, GCOs2-2, GCOs2-3) all had relatively high storage modulus (∼150 kPa) at a frequency of 1 rad/s. Overall, the interfacial engineering strategy used in this study may be useful for converting liquid oils into semi-solid materials, which may be useful for several applications in the food and other industries.

Nanoarchitectonics and electrocatalytic properties of platinum nanoparticles in weak polyelectrolytes‐based multilayer thin films

AbstractIn this study, the electrocatalytic behavior of platinum (Pt) nanoparticles (NPs) in a novel multilayered thin film is investigated for proton exchange membrane fuel cells (PEMFC) applications. The multilayer thin films are assembled by the alternate deposition of branched polyethylenimine (BPEI) and poly(acrylic acid) (PAA) from aqueous solutions through a layer‐by‐layer (LbL) technique. Two extreme assembly pH conditions critically influence the films' physical and morphological characteristics, subsequently affecting their electrochemical behavior. Manipulation of the assembly pH modifies the charge density of the weak polyelectrolytes (BPEI and PAA), leading to variations in physical, structural, and electrochemical properties. The LbL thin films assembled at a pH of 9.5 for BPEI and 4.5 for PAA exhibit significantly greater thickness compared to the same film with all components deposited at pH 4.5. This is attributed to in‐and‐out diffusion of the partially charged polyelectrolytes with coiled polymeric conformation (BPEI at pH 9.5 and PAA at pH 4.5). As‐assembled LbL thin films are used as nanoreactors for the deposition of Pt NPs. The nanoscale control over polymeric conformation and charge density significantly influences electrocatalytic performance. 9.5BPEI/4.5PAA thin films exhibit higher electrocatalytic activity relative to 4.5BPEI/4.5PAA systems. This improved performance in 9.5BPEI/4.5PAA multilayers is ascribed to the fact that more carboxylic acid groups of PAA are coated in an exponentially grown behavior, which provides more active sites available for Pt NPs to be deposited. The multilayer thin films containing uniformly dispersed Pt NPs can be an attractive and advanced hybrid electrode material with great promise for the proton exchange membrane fuel cells.

Advancements in Polymer-Assisted Layer-by-Layer Fabrication of Wearable Sensors for Health Monitoring.

Recent advancements in polymer-assisted layer-by-layer (LbL) fabrication have revolutionized the development of wearable sensors for health monitoring. LbL self-assembly has emerged as a powerful and versatile technique for creating conformal, flexible, and multi-functional films on various substrates, making it particularly suitable for fabricating wearable sensors. The incorporation of polymers, both natural and synthetic, has played a crucial role in enhancing the performance, stability, and biocompatibility of these sensors. This review provides a comprehensive overview of the principles of LbL self-assembly, the role of polymers in sensor fabrication, and the various types of LbL-fabricated wearable sensors for physical, chemical, and biological sensing. The applications of these sensors in continuous health monitoring, disease diagnosis, and management are discussed in detail, highlighting their potential to revolutionize personalized healthcare. Despite significant progress, challenges related to long-term stability, biocompatibility, data acquisition, and large-scale manufacturing are still to be addressed, providing insights into future research directions. With continued advancements in polymer-assisted LbL fabrication and related fields, wearable sensors are poised to improve the quality of life for individuals worldwide.

The layer-by-layer assembled ERGO+/ERGO− multilayer modified electrode for sensitive detection of dopamine

Graphene materials represented by graphene oxide (GO) have been widely regarded as functional coatings or films to modify surface of the electrode for detecting dopamine molecules. However, interfacial material properties for detection sensitivity, film stability, and applicability to electrodes are still highly desired. Herein, we first present a screen-printing carbon electrode (SPCE) coated with an electrochemically reduced layer-by-layer (LbL) assembled multilayer driven by an electrostatic interaction between positively charged polyethyleneimine-modified GO with amine groups (ERGO+) and negatively charged carboxyl-functionalized GO (ERGO−), which is briefly described as (ERGO+/ERGO−)n/SPCE. Firstly, without using conventional glassy carbon and gold electrodes, SPCE was tried to make coatings adapt to more flexible and unstable electrodes, simultaneously guaranteeing higher detection performance. Secondly, although a variety of electrochemical sensors such as GO−/SPCE and ERGO−/SPCE were obtained through the drop-casting technique, as-prepared (ERGO+/ERGO−)n/SPCE showed much higher electrocatalytic activities with enhanced peak current signals and reduced charge transfer resistance. Finally, excellent electrochemical properties and sensing performances of the (ERGO+/ERGO−)n/SPCE sensor for detection of dopamine were demonstrated, especially having a linear range of 1 μM to 1000 μM. Meanwhile, the detection limit is as low as 0.39 μM and S/N is equal to 3. The present work offers a potential direction to develop GO modified electrodes for sensitive biomolecular detection.

Poly(β-aminoester) Physicochemical Properties Govern the Delivery of siRNA from Electrostatically Assembled Coatings.

Localized short interfering RNA (siRNA) therapy has the potential to drive high-specificity molecular-level treatment of a variety of disease states. Unfortunately, effective siRNA therapy suffers from several barriers to its intracellular delivery. Thus, drug delivery systems that package and control the release of therapeutic siRNAs are necessary to overcome these obstacles to clinical translation. Layer-by-layer (LbL) electrostatic assembly of thin film coatings containing siRNA and protonatable, hydrolyzable poly(β-aminoester) (PBAE) polymers is one such drug delivery strategy. However, the impact of PBAE physicochemical properties on the transfection efficacy of siRNA released from LbL thin film coatings has not been systematically characterized. In this study, we investigate the siRNA transfection efficacy of four structurally similar PBAEs in vitro. We demonstrate that small changes in structure yield large changes in physicochemical properties, such as hydrophobicity, pKa, and amine chemical structure, driving differences in the interactions between PBAEs and siRNA in polyplexes and in LbL thin film coatings for wound dressings. In our polymer set, Poly3 forms the most stable interactions with siRNA (Keff,w/w = 0.298) to slow release kinetics and enhance transfection of reporter cells in both colloidal and thin film coating approaches. This is due to its unique physiochemical properties: high hydrophobicity (clog P = 7.86), effective pKa closest to endosomal pH (pKa = 6.21), and high cooperativity in buffering (nhill = 7.2). These properties bestow Poly3 with enhanced endosomal buffering and escape properties. Taken together, this work elucidates the connections between small changes in polymer structure, emergent properties, and polyelectrolyte theory to better understand PBAE transfection efficacy.

Solvent-tolerant lignosulfonate-attapulgite/calcium carbonate coating on nylon filter mesh for oily water treatment

Due to the rapid increasing drainage of oily wastewater, robust and durable filtration materials with underwater superoleophobic coatings are highly desired. The existing underwater superoleophobic filter materials for oil/water separation are always subject to mechanical and chemical damages, causing the significant loss of superoleophobicity. Herein, a robust and tolerant nylon filter mesh (NFM) with underwater superoleophobicity was fabricated through simple layer-by-layer (LBL) assembly of lignosulfonate (LS), attapulgite (APT) nanorods, calcium ion, and carbonate on NFM. Compared with LS@CaCO3 assembly, the obtained LS-APT@CaCO3 assembly on NFM exhibits good micro/nano-structure, uniform distribution, and excellent underwater superoleophobicity (oil contact angle: > 156°). Moreover, after the fabricated mesh is subjected to the immersion in corrosive environments (acid, base, and salt aqueous solutions) and hot water as well as severe mechanical scratch, the oil contact angle are still higher than 147.5°, implying superb durability. More importantly, the as-obtained NFM is able to treat a variety of oil/pure water and oil/corrosive solution mixtures with separation efficiencies of over 98.2 %. Therefore, the as-prepared mesh has a huge application potential in oil-polluted water remediation due to the simple, facile, and eco-friendly preparation process.

Photo-crosslinking and layer-by-layer processed organic photodetectors with remarkably suppressed dark current

The effective reduction of dark (or noise) current presents a significant hurdle in enhancing the detectivity of organic photodetectors (OPDs). To address this challenge, a photo-crosslinkable donor polymer, PM6-Br50, is synthesized by introducing bromoalkyl side-chains onto the PM6 structure. This modification enables the formation of a pseudo planar heterojunction (p-PHJ) structure of crosslinked donor/acceptor through a layer-by-layer (LbL) sequential process without the necessity for an semi-orthogonal solvent. This innovation effectively overcomes solvent-related limitations in the LbL process. Additionally, we replace the semi-metallic hole-transport layer (HTL), PEDOT:PSS, with a semiconducting conjugated polyelectrolyte (TPAFS-TMA) with a high conduction band. The p-PHJ configuration, featuring pure donor/anode and pure acceptor/cathode contacts, enhances the charge injection barrier for electrons (holes) from the anode (cathode) in the dark under reverse bias, effectively minimizing dark current. Furthermore, the TPAFS-TMA HTL serves to impede electron injection from the anode. Through the synergistic combination of these two strategies, a significantly reduced dark current density (4.03 × 10−10 A cm−2) is measured by four orders of magnitude, compared to the bulk heterojunction OPDs with PEDOT:PSS. Furthermore, we measure remarkably high shot noise-based and total noise current-based specific detectivities of 4.27 × 1013 and 6.97 × 1012 cm Hz1/2 W−1 (with linear dynamic range of 73.7 dB), respectively.

Layer-by-layer self-assembly of durable, breathable and enhanced performance thermoelectric fabrics for collaborative monitoring of human signal

Thermoelectric devices have received widespread attention in next-generation flexible electronics due to their excellent self-powered characteristics, multifunctionality and high integrability. However, current thermoelectric devices suffer from drawbacks such as poor durability, complex preparation processes, and terrible air permeability which is the necessary metric in wearing comfort. Here, we propose a layer-by-layer (LBL) self-assembly strategy to prepare multifunctional thermoelectric fabrics with enhanced thermoelectric performance and durability. Based on the self-assembly effect, the interfacial bonding between the thermoelectric material and the fabric substrate is effectively improved, so that the thermoelectric properties of the fabrics can still be maintained stable after 2000 bending cycles and 600 washing cycles. Moreover, this strategy increases the electrical conductivity of the fabric by a factor of 4 without affecting the fabric’s air permeability (up to 400 mm s−1 at 50 Pa) and tensile properties (strains exceeding 100 %). Due to its wearability and multifunctionality, the fabric was designed as a synergistic monitoring system that includes facial respiration monitoring and knee joint motion monitoring for continuous monitoring of the athlete’s dynamic body condition. This thermoelectric fabric shows amazing potential for advanced smart textiles, soft robotics and human–computer interaction.

High-Density, Nonvolatile, Flexible Multilevel Organic Memristor Using Multilayered Polymer Semiconductors.

Nonvolatile organic memristors have emerged as promising candidates for next-generation electronics, emphasizing the need for vertical device fabrication to attain a high density. Herein, we present a comprehensive investigation of high-performance organic memristors, fabricated in crossbar architecture with PTB7/Al-AlOx-nanocluster/PTB7 embedded between Al electrodes. PTB7 films were fabricated using the Unidirectional Floating Film Transfer Method, enabling independent uniform film fabrication in the Layer-by-Layer (LbL) configuration without disturbing underlying films. We examined the charge transport mechanism of our memristors using the Hubbard model highlighting the role of Al-AlOx-nanoclusters in switching-on the devices, due to the accumulation of bipolarons in the semiconducting layer. By varying the number of LbL films in the device architecture, the resistance of resistive states was systematically altered, enabling the fabrication of novel multilevel memristors. These multilevel devices exhibited excellent performance metrics, including enhanced memory density, high on-off ratio (>108), remarkable memory retention (>105 s), high endurance (87 on-off cycles), and rapid switching (∼100 ns). Furthermore, flexible memristors were fabricated, demonstrating consistent performance even under bending conditions, with a radius of 2.78 mm for >104 bending cycles. This study not only demonstrates the fundamental understanding of charge transport in organic memristors but also introduces novel device architectures with significant implications for high-density flexible applications.

Influence of chitosan’s purification methodology on the formation of layer-by-layer films

Concern for the environment for the development of new biodegradable materials has been constant in scientific circles. With this in mind, this work proposes a study on the formation of self-assembled thin films using chitosan (Qt), a biodegradable material. This polyelectrolyte has several purification methodologies, but we did not identify any studies on the effect of these methodologies on film formation. Thus, after the purification process and characterization of the three forms of chitosan purification, films were produced using the layer-by-layer (LBL) technique. The growth of the films was monitored using the UV-vis technique. Spectroscopy in the Infrared region showed positions in the main bands present in chitosan and sodium nitroprusside (NP) in the formed films. Two semi-reversible processes were found for the QtN/NP and QtAc/NP films, related to the reduction of iron oxide present in the NP. The effect of pH (4.0, 7.0 and 10) on the electrochemical processes indicated that the charge transfer occurs more efficiently at pH 7.0.

Modulating the Nature of Ionizable Lipids and Number of Layers in Hyaluronan-Decorated Lipid Nanoparticles for In Vitro Delivery of RNAi.

Lipid nanoparticles (LNPs) have established their position as nonviral vectors for gene therapy. Tremendous efforts have been made to modulate the properties of LNPs to unleash their full clinical potential. Among the strategies being pursued, the layer-by-layer (LbL) technique has gained considerable attention in the biomedical field. Illuminated by our previous work, here we investigate if the LbL approach could be used to modify the LNP cores formulated with three different ionizable lipids: DODMA, MC3, and DODAP. Additionally, we wondered if more than three layers could be loaded onto LNPs without disrupting their gene transfection ability. Taking advantage of physicochemical analysis, as well as uptake and gene silencing studies, we demonstrate the feasibility of modifying the surface of LNPs with the LbL assembly. Precisely, we successfully modified three different LNPs using the layer-by-layer strategy which abrogated luciferase activity in vitro. Additionally, we constructed a 5×-layered HA-LNP containing the MC3 ionizable lipid which outperformed the 3×-layered counterpart in transfecting miRNA-181-5p to the pediatric GBM cell line, as a proof-of-concept in vitro experiment. The method used herein has been proven reproducible, of easy modification to adapt to different ionizable lipid-containing LNPs, and holds great potential for the translation of RNA-based therapeutic strategies.

Fire safe and sustainable lightweight materials based on Layer-by-Layer coated keratin fibers from tannery wastes

The increasing consciousness about the depletion of natural resources and the sustainability agenda are the major driving forces to try to reuse and recycle organic materials such as agri-food and industrial wastes. In this context, keratin fibers, as a waste from the tannery industry, represent a great opportunity for the development of green functional materials. In this paper, keratin fibers were surface functionalized using the Layer-by-Layer (LbL) deposition technique and then freeze-dried in order to obtain a lightweight, fire-resistant, and sustainable material. The LbL coating, made with chitosan and carboxymethylated cellulose nanofibers, is fundamental in enabling the formation of a self-sustained structure after freeze-drying. The prepared porous fiber networks (density 100 kg m–3) display a keratin fiber content greater than 95 wt% and can easily self-extinguish the flame during a flammability test in a vertical configuration. In addition, during forced combustion tests (50 kW m–2) the samples exhibited a reduction of 37 % in heat release rate and a reduction of 75 % in smoke production if compared with a commercial polyurethane foam. The results obtained represent an excellent opportunity for the development of fire-safe sustainable materials based on fiber wastes.