Layer-by-layer Films Research Articles

Three-Color Protein Photolithography with Green, Red, and Far-Red Light.

Protein photolithography is an invaluable tool for generating protein microchips and regulating interactions between cells and materials. However, the absence of light-responsive molecules that allow for the copatterning of multiple functional proteins with biocompatible visible light poses a significant challenge. Here, a new approach for photopatterning three distinct proteins on a single surface by using green, red, and far-red light is reported. The cofactor of the green light-sensitive protein CarH is engineered such that it also becomes sensitive to red and far-red light. These new cofactors are shown to be compatible with two CarH-based optogenetic tools to regulate bacterial cell-cell adhesions and gene expression in mammalian cells with red and far-red light. Further, by incorporating different CarH variants with varying light sensitivities in layer-by-layer (LbL) multiprotein films, specific layers within the films, along with other protein layers on top are precisely removed by using different colors of light, all with high spatiotemporal accuracy. Notably, with these three distinct colors of visible light, it is possible to incorporate diverse proteins under mild conditions in LbL films based on the reliable interaction between Ni2+- nitrilotriacetic acid (NTA) groups and polyhistidine-tags (His-tags)on the proteins and their subsequent photopatterning. This approach has potential applications spanning biofabrication, material engineering, and biotechnology.

Chiral Bioelectrocatalytic Oxidations Driven By Electrocatalytic Oxygen Reduction and Horseradish Peroxidase or Cytochrome P450

Biocatalysis, the use of enzymes for synthesis, has emerged as a powerful tool for synthesis of chiral molecules in pharmaceutical and fine chemical industries. Natural enzymes offer inherent stereoselectivity, making them attractive catalysts for this purpose. Peroxidases and cytochrome P450s enzymes utilize an iron-heme cofactor to perform a diverse array of chemical transformations including CH2 hydroxylation, epoxidations, and sulfur-oxidations. Here, we report chiral biocatalytic oxidations in microemulsion media driven by horseradish peroxidase (HRP) coupled with a synthetic Cu2+-polymer electrocatalyst to convert O2 to H2O2. This tandem system uses crosslinked layer-by-layer (LBL) films of polyelectrolytes with Cu2+- poly(2-hydroxy-3-dipicolylamino) propyl methacrylate (Py-PGMADPA) to drive O2 reduction. Peroxide in turn activates HRP crosslinked in LbL films on magnetic beads (MB) to biocatalytically oxidize styrene, ethylbenzene, and methyl phenylacetate to chiral products. R-stereoisomers of these reactants were selectively formed with a high enantiomeric excess of > 80%. Conductive microemulsion reaction media are used to provide solubility to the non-polar reactants and water to hydrate the enzymes to function. The enzyme films show high thermal stability and high chiral selectivity up to 90 °C. A second synthetic goal was to compare chiral products of reactions catalyzed by cyt P450’s natural catalytic pathway mimicked by electrocatalysis versus via electrochemical generation of H2O2. We immobilized baculosome-P450s in LBL films with polystyrene sulfonate for the natural catalytic pathway, and for peroxide activation crosslinked P450 LbL on magnetic beads. These synthetic hybrid approaches open new doors to designing biocatalytic syntheses using an electrochemical driving force. Keywords: Biocatalysis, organic syntheses, cytochrome P450, horseradish peroxidase, regioselective and stereoselective oxidation

Complex Sequence-Defined Heteropolymers Enable Controlled Film Growth in Layer-By-Layer Assembly.

Digitally-encoded poly(phosphodiesters) (d-PPDE) with highly complex primary structures are evaluated for layer-by-layer (LbL) assembly. To be easily decoded by mass spectrometry (MS), these digital polymers contain many different monomers: 2 coding units allowing binary encryption, 1 cleavable spacer allowing controlled MS fragmentation, and 3 mass tags allowing fragment identification. These complex heteropolymers are therefore composed of 6 different motifs. Despite this strong sequence heterogeneity, it is found that they enable a highly controlled LbL film formation. For instance, a regular growth is observed when alternating the deposition of negatively-charged d-PPDE and positively-charged poly(allyl amine hydrochloride) (PAH). Yet, in this approach, the interdistance between consecutive coded d-PPDE layers remains relatively small, which may be an issue for data storage applications, especially for the selective decoding of the stored information. Using poly(sodium 4-styrene sulfonate) (PSS) as an intermediate non-coded polyanion, it is shown that a controlled interdistance between d-PPDE layers can be easily achieved, while still maintaining a regular LbL growth. Last but not least, it is found in this work that d-PPDE of relatively small molecular weight (i.e., significantly smaller than those of PAH and PSS) still enables a controlled LbL assembly.

Investigating layer-by-layer films of carbon nanotubes and nickel phthalocyanine towards diquat detection

The indiscriminate use of pesticides makes us susceptible to the toxicity of these chemical compounds, which may be present in high quantities in our food. It is crucial to develop inexpensive and rapid methods for determining these pesticides for government control or even for the general population. In this study, we investigated the fabrication of self-assembled LbL films using multi-walled carbon nanotubes (MWCNT) and nickel tetrasulphonated phthalocyanine (NiTsPc) as an electrochemical sensor for the herbicide Diquat (DQ). The Layer-by-Layer (LbL) assembly of the (MWCNT/NiTsPc) film was examined, along with its structural and morphological characteristics. The effect of the number of layers in DQ detection was evaluated by cyclic voltammetry, followed by the detection through differential pulse voltammetry. The achieved limit of detection was 9.62 × 10−7 mol L−1. A ~ 30% decrease in sensitivity was observed in the presence of Paraquat, a banned herbicide and electrochemical interferent due to the structural similarities, which is regularly neglected in the most published studies. The sensor was tested in real samples, demonstrating a recovery of 98.5% in organic apples.

A microfluidic platform for automatic continuous flow layer‐by‐layer assembly of polymer multilayered nanofilms

AbstractCapillary flow layer‐by‐layer assembly is a microfluidic platform for high throughput preparation and screening of multilayered polymer nanofilms. However, it is time‐consuming and labor‐intensive, since the switching of polyelectrolyte solutions is done manually. As the emergence of flow chemistry and microdevices for artificial intelligence‐based lab automation, an automatic system that can switch polymer solutions and washing liquids is urgently needed for building functional LbL films inside microfluidic devices. Herein, we construct a continuous flow (ConF)‐layer‐by‐layer (LbL) device that can automatically fabricate polymer nanofilms inside a microfluidic device. By including a flow separator and a mixer (a model polyelectrolyte pair), chitosan and carboxymethyl cellulose can be deposited inside a microfluidic device using the ConF‐LbL system. Resulting nanofilms are studied by investigating thickness and surface roughness of the nanofilms and comparing with the other conventional LbL methods. The acid dissolution method was used to compare the differences in stability between nanofilms made from ConF‐LbL and static immersive method in similar conditions. Furthermore, by using one optimized film formulation for coating on the inside walls of a microfluidic chip, we successfully demonstrated the ability of this device to capture cancer cells in whole blood. This ConF‐LbL platform is expected to be a convenient tool to coat functional nanofilms inside microdevices for biomedical and sensor applications.

Controlled Insertion of Silver Nanoparticles in LbL Nanostructures: Fine-Tuning the Sensing Units of an Impedimetric E-Tongue

Silver nanoparticles (AgNPs) possess unique characteristics ideal for enhancing device sensitivity, primarily due to their high surface-to-volume ratio facilitating heightened interaction with analytes. Integrating AgNPs into polymers or carbon-based materials results in nanocomposites with synergistic properties, enabling the detection of minute changes in the environment across various applications. In this study, we investigate the adsorption kinetics of AgNPs within multilayered layer-by-layer (LbL) structures, specifically examining the impact of AgNPs concentration in the LbL film formation that is further explored as sensing units in an impedimetric microfluidic e-tongue. Although absorption kinetic studies are infrequent, they are crucial to optimize the AgNPs adsorption and distribution within LbL structures, significantly influencing upcoming applications. Through systematic variation of AgNPs concentration within identical LbL architectures, we applied the films as sensing units in a microfluidic e-tongue capable of distinguishing food enhancers sharing the umami taste profile. Across all tested scenarios, our approach consistently achieves robust sample separation, evidenced by silhouette coefficient, principal component analyses, and long-term stability. This work contributes to exploring controlled nanomaterial-based developments, emphasizing the importance of precise parameter control for enhanced sensor performance across diverse analytical applications.

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.

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.

Stimuli-triggered multilayer films in response to temperature and ionic strength changes for controlled favipiravir drug release

The block copolymer micelles and natural biopolymers were utilized to form layer-by-layer (LbL) films via electrostatic interaction, which were able to effectively load and controllably release favipiravir, a potential drug for the treatment of coronavirus epidemic. The LbL films demonstrated reversible swelling/shrinking behavior along with the manipulation of temperature, which could also maintain the integrity in the structure and the morphology. Due to dehydration of environmentally responsive building blocks, the drug release rate from the films was decelerated by elevating environmental temperature and ionic strength. In addition, the pulsed release of favipiravir was observed from the multilayer films under the trigger of temperature, which ensured the precise control in the content of the therapeutic reagents at a desired time point. The nanoparticle-based LbL films could be used for on-demand in vitro release of chemotherapeutic reagents.

High‐Reproducibility Layer‐by‐Layer Non‐Fullerene Organic Photovoltaics with 19.18% Efficiency Enabled by Vacuum‐Assisted Molecular Drift Treatment

AbstractThe thin film deposition engineering of layer‐by‐layer (LbL) non‐fullerene organic solar cells (OSCs) favors vertical phase distributions of donor:acceptor (D:A), effectively boosting the power conversion efficiency (PCE). However, previous deposition strategies mainly aimed at optimizing the morphology of LbL films, and paid limited attention to the reproducibility of device performance. To achieve high device performance and maintain reproducibility, a strategy for hierarchical morphology manipulation in LbL OSCs is developed. A series of LbL devices are fabricated by introducing vacuum‐assisted molecular drift treatment (VMDT) to the donor or acceptor layer individually or simultaneously to elucidate the functionalities of this treatment. Essentially, the VMDT provides an extended drift driving force to manipulate the donor and acceptor molecules, resulting in a well‐defined vertical phase distribution and ordered molecular packing. These enhancements facilitate improvement in the D:A interface area and charge transport channel, ultimately contributing to impressive PCEs of 19.18% from 18.27% in the LbL devices. More importantly, using VMDT overcomes the notorious batch‐dependent and heat treatment degradation issues of OSCs, leading to excellent batch‐to‐batch reproducibility and enhanced stability of the devices. This reported method provides a promising strategy available for industrial and laboratory use to controllably manipulate the morphology of LbL OSCs.

Engineering Degradation Rate of Polyphosphazene-Based Layer-by-Layer Polymer Coatings.

Degradable layer-by-layer (LbL) polymeric coatings have distinct advantages over traditional biomedical coatings due to their precision of assembly, versatile inclusion of bioactive molecules, and conformality to the complex architectures of implantable devices. However, controlling the degradation rate while achieving biocompatibility has remained a challenge. This work employs polyphosphazenes as promising candidates for film assembly due to their inherent biocompatibility, tunability of chemical composition, and the buffering capability of degradation products. The degradation of pyrrolidone-functionalized polyphosphazenes was monitored in solution, complexes and LbL coatings (with tannic acid), providing the first to our knowledge comparison of solution-state degradation to solid-state LbL degradation. In all cases, the rate of degradation accelerated in acidic conditions. Importantly, the tunability of the degradation rate of polyphosphazene-based LbL films was achieved by varying film assembly conditions. Specifically, by slightly increasing the ionization of tannic acid (near neutral pH), we introduce electrostatic "defects" to the hydrogen-bonded pairs that accelerate film degradation. Finally, we show that replacing the pyrrolidone side group with a carboxylic acid moiety greatly reduces the degradation rate of the LbL coatings. In practical applications, these coatings have the versatility to serve as biocompatible platforms for various biomedical applications and controlled release systems.

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.

Light-Responsive Layer-By-Layer Film Containing Gold Nanorods for Sequential Drug Release.

Chemically and physically stable multidrug-loaded layer-by-layer (LbL) films are promising candidates for sequential and on-demand drug release at concentrations suitable for various applications. The synergistic effect of the sequential release of drugs may enhance their therapeutic efficacy in treating skin cancer and other complex medical conditions. In this study, we prepared LbL films by alternating the deposition of cationic linear polyethylenimine, camptothecin (CPT)-loaded gold nanorods (GNRs), anionic poly(styrenesulfonate), and doxorubicin (DOX) based on electrostatic interactions. The film exhibited loading of CPT and DOX, which could be tuned according to the requirements of the application by changing the parameters of the LbL process. Herein, CPT was encapsulated in GNRs and showed good stability and absorption in the near-infrared (NIR) range (650-900 nm). The prepared LbL film showed a pH-dependent DOX release. Subsequently, the functionalized GNRs showed excellent photothermal properties, which assisted the on-demand release of CPT upon NIR irradiation with further release of DOX. Our results suggest that the LbL approach for sequential drug release can be an effective drug delivery platform owing to its cytocompatibility, anticancer effects, and stimuli-responsive properties.

A Layer-by-Layer Self-Assembled Bio-Macromolecule Film for Stable Zinc Anode.

Side reactions on zinc metal (Zn) anodes are formidable issues that cause limited battery life of aqueous zinc-ion batteries (AZIBs). Here, a facile and controllable layer-by-layer (LbL) self-assembly technique is deployed to construct an ion-conductive and mechanically robust electrolyte/anode interface for stabilizing the Zn anode. The LbL film consists of two natural and biodegradable bio-macromolecules, chitosan (CS) and sodium alginate (SA). It is shown that such an LbL film tailors the solvation sheath of Zn ions and facilitates the oriented deposition of Zn. Symmetric cells with the four double layers of CS/SA ((CS/SA)4 -Zn) exhibit stable cycles for over 6500h. The (CS/SA)4 -Zn||H2 V3 O8 coin cell maintains a specific capacity of 125.5 mAh g-1 after 14000 cycles. The pouch cell with an electrode area of 5 × 7 cm2 also presents a capacity retention of 83% for over 500 cycles at 0.1 A g-1 . No obvious dendrites are observed after long cycles in both symmetric and full cells. Given the cost-effective material and fabrication, and environmental friendliness of the LbL films, this Zn protection strategy may boost the industrial application of AZIBs.

Layer-by-layer assembly of poly-l-lysine/hyaluronic acid protein reservoirs on poly(glycerol sebacate) surfaces

The modification of biomaterial surfaces has become increasingly relevant in the context of ongoing advancements in tissue engineering applications and the development of tissue-mimicking polymer materials. In this study, we investigated the layer-by-layer (LbL) deposition of polyelectrolyte multilayer protein reservoirs consisting of poly-l-lysine (PLL) and hyaluronic acid (HA) on the hydrophobic surface of poly(glycerol sebacate) (PGS) elastomer. Using the methods of isothermal titration calorimetry and surface plasmon resonance, we systematically investigated the interactions between the polyelectrolytes and evaluated the deposition process in real time, providing insight into the phenomena associated with film assembly. PLL/HA LbL films deposited on PGS showed an exceptional ability to incorporate bone morphogenetic protein-2 (BMP-2) compared to other growth factors tested, thus highlighting the potential of PLL/HA LbL films for osteoregenerative applications. The concentration of HA solution used for film assembly did not affect the thickness and topography of the (PLL/HA)10 films, but had a notable impact on the hydrophilicity of the PGS surface and the BMP-2 release kinetics. The release kinetics were successfully described using the Weibull model and hyperbolic tangent function, underscoring the potential of these less frequently used models to compare the protein release from LbL protein reservoirs.

Evaluation of bioactive multilayer and edible gelatin/xanthan gels crosslinked with Echinacea purpurea for Ricotta cheese preservation

In view of enhancing the reliability and performance of active biodegradable and sustainable biomaterials, physically stable layer by layer (LBL) and multilayer films were developed for active food preservation applications. Herein, we propose for the first time, multifunctional and edible biopolymeric packages fabricated from gelatin (Gel), xanthan (Xan) and naturally crosslinked by Echinacea purpurea extract (EPE), which was the active ingredient. As displayed by FTIR and SEM, LBL casting and EPE crosslinking brought about strong dense, and compact composite structures resulting from a significant boost in the intramolecular H-bonding between the composing molecules and layers. Such phenomenon resulted in considerable enhancement in the films mechanical properties, oxygen, water vapor (WV) barriers, and antioxidant capacities at EPE concentration of 3 % as compared to pure gels and Gel/EPE blends. More importantly, EPE release patterns were more controlled in acidic environments than in aqueous conditions over 120 h. Remarkably, multilayer Gel/EPE/Xan treatment reduced impressive 95 ± 0.09 and 80 ± 0.13 % of Staphylococcus aureus and Salmonella enterica, respectively after 48 h. Eventually, the films wrapping succeeded in keeping Ricotta cheese samples properties much closer to those of the fresh ones in terms of weight loss, pH, visual appearance and microbiological analysis. LBL and multilayer films could substantially reduce the bacterial count by high 4.07 ± 0.17 and 3.97 ± 0.23 log CFU/g, respectively under chilled storage over 9 days. By virtue of these positive features, our modified films can be configured as affordable and eco-friendly alternatives for conventional plastic packaging.

Development of a Nanostructured Film Containing Palygorskite and Dermaseptin 01 Peptide for Biotechnological Applications

AbstractClay minerals are suitable matrices to anchor organic molecules such as antimicrobial peptides (AMPs) so that their bioactivity is maintained, enabling the formation of new materials with potential for new applications in biotechnology. The objective of the present study was to develop a nanostructured film where the properties of palygorskite (Plg) were combined at the molecular level with Dermaseptin 01 (DRS 01), in which the clay mineral also served as a substrate for the immobilization of this peptide. The films were prepared using the Layer-by-Layer (LbL) self-assembly technique. Crude palygorskite without purification (Plg IN) was subjected to physical and chemical procedures to increase its adsorptive properties. The structure, chemical composition, and morphology of Plg were investigated by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), X-ray fluorescence spectrometry (XRF), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). LbL films were adsorbed onto ITO (Indium Tin Oxide) and characterized electrochemically by cyclic voltammetry (CV), UV-Visible spectroscopy, and atomic force microscopy (AFM). For the ITO/DRS 01 and ITO/Plg/DRS 01 films, an oxidation process at +0.77 V was observed, confirming that the DRS 01 maintained its electroactive behavior and intrinsic properties. The results also showed that Plg served as excellent support for the immobilization of DRS 01, increasing its concentration and availability in the film form. This work reported immobilizing the DRS 01 peptide with Plg for the first time in an ultrathin film with bioactive properties. Thus, the film developed can be explored for applications such as biosensor devices and antimicrobial coating materials as well as other biotechnological applications.

Examining layer‐by‐layer assembly of polyelectrolyte‐drug interactions using Quartz Crystal Microbalance with Dissipation

AbstractThe incorporation of drug molecules into layer‐by‐layer (LbL) assemblies attracts great interest in biomedical applications. This work describes the preparation and characterization of LbL multilayers including drugs, namely ibuprofen (IBF‐Na) and Diclofenac sodium salt (DCF‐Na) as anionic molecules. The main aim is to enhance the drug loading capacity within the LbL assembly. The effects of drug‐LbL multilayered films obtained from poly(diallyl dimethylammonium chloride) (PDADMAC)/IBF‐Na and PDADMAC/DCF‐Na interactions on multilayer growth and loading of model molecules are examined using UV‐Visible and Quartz‐Crystal Microbalance with Dissipation (QCM‐D). The wet mass of PDADMAC/IBF‐Na is found to be 67.2 ng/cm2, while PDADMAC/DCF‐Na film exhibits 201.6 ng/cm2 mass adsorption. Furthermore, the multilayer stabilities are assessed against neutral, acidic, and basic solutions. The results demonstrate that the LbL films have robustness, without any signs of multilayer degradation. By the way, the incorporation of IBF‐Na into the feed solution leads to the formation of a rigid structure, whereas the inclusion of DCF‐Na results in a comparatively flexible structure. The use of a higher molecular weight and more polar drug in the feed causes a noticeable rise in surface hydrophilicity and surface roughness. PDADMAC/IBF‐Na and PDADMAC/DCF‐Na display average contact angles of 46 ± 1.3° and 76 ± 2° while they have roughness values of 5.9 and 8.0 nm, respectively. LbL multilayers fabricated from a polycation and anionic drug can be considered as a promising material platform for controlled drug loading due to their tunable physicochemical and morphological properties as well as surface wettability.

Influence of blending and layer-by-layer assembly methods on chitosan–gelatin composite films enriched with curcumin nanoemulsion

In this study, gelatin (GE) was composited with chitosan films (CH) and chitosan films incorporated with curcumin nanoemulsion (CH-CNE) through blending and layer-by-layer (LbL) assembly in order to overcome the physical limitations of the chitosan and its incorporated films. Furthermore, the distinctive effects of blending and LbL assembly on the physicochemical parameters of the composite films were assessed. The composite LbL films incorporated with GE exhibited improvement of water vapor barrier, tensile strength, solubility, which contributed to the enhanced antioxidant activity from the single components. By contrast, the composite films of the blending method exhibited greater elongation at break and increased swelling degree. Additionally, the films containing the nanoemulsion exhibited reduced light transmission and increased opacity. The thermal properties indicating the thermal stability and compatibility interactions of the composite films were examined by the glass transition temperature (Tg). Results revealed that the distinctive behavior of the Tg was affected by the compositing method. The LbL films exhibited substantially increased Tg, indicating enhanced thermal stability. The results indicated that the composited films formed via the LbL assembly attained better physicochemical properties and thermal stability, implying higher compatible film than the blending.

Investigation of the Synergistic Effect of Layer-by-Layer Films of Carbon Nanotubes and Polypyrrole on a Flexible Electrochemical Device for Paraquat Sensing

This research aims to study flexible sensors based on a poly(butylene adipate-co-terephthalate) (PBAT) biodegradable polymer and graphite. Sensors were modified through the layer-by-layer (LbL) technique to improve their electrochemical behavior for paraquat (PQ) detection. Nanostructured films were obtained by alternating layers of anionic and cationic materials, carbon nanotubes (CNTs), and polypyrrole (PPY), respectively. The devices, with and without modification, were characterized by contact angle, scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). Electrochemical characterization was labeled via cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). PQ molecules were detected using the differential pulse voltammetry (DPV) technique in a concentration range of 0.1 to 2.1 µM. The sensor detection limit (LOD) was obtained using the analytical curve, with it being equal to 0.073 µM. The LbL film gPBAT(PPY/CNT)n sensor showed good stability, reproducibility, and repeatability, with recovery values ranging from 99.4% to 109.3% for PQ when the analyzed samples were contaminated with tap water. The produced electrodes have the advantage of being flexible, disposable, reproducible, and of low manufacturing cost, which makes them attractive for portable environmental analysis.