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A novel modification technique employing a layer-by-layer (LbL) self-assembly method, integrated with a pressure-assisted filtration system, was developed for enhancing a commercial polyethersulfone (PES) microfiltration (MF) membrane. This modification involved the incorporation of tannic acid (TA) in conjunction with graphene oxide (GO) nanosheets. The effectiveness of the LbL method was confirmed through comprehensive characterization analyses, including ATR-FTIR, SEM, water contact angle (WCA), and mean pore size measurements, comparing the modified membrane with the original commercial one. Sixteen variations of PES MF membranes were superficially modified using a three-factorial design, with the deposited amount of TA and GO as key factors. The influence of these factors on the morphology and performance of the membranes was systematically investigated, focusing on parameters such as pure water permeability (PWP), blue corazol (BC) dye removal efficiency, and flux recovery rate (FRR). The membranes produced with the maximum amount of GO (0.1 mg, 0.55 wt%) and TA as the inner and outer layers demonstrated remarkable FRR and significant BC removal, exceeding 80%. Notably, there was no significant difference observed when using either 0.2 (1.11 wt%) or 0.4 mg (2.22 wt%) in the first layer, as indicated by the Tukey mean test. Furthermore, the modified membrane designated as MF/TA0.4GO0.1TA0.4 was evaluated in the filtration of a simulated dye bath wastewater, exhibiting a BC removal efficiency of 49.20% and a salt removal efficiency of 27.74%. In conclusion, the novel PES MF membrane modification proposed in this study effectively enhances the key properties of pressure-driven separation processes.

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This article presents the assembly and characterization of poly(diallyldimethylammonium chloride)/multi-walled carbon nanotubes (PDDA/MWCNTs) thin films on borosilicate bottles using a layer-by-layer (LBL) approach. The thin films, consisting of 10 bilayers of coating materials, were thoroughly characterized using UV-VIS spectroscopy, scanning electron microscopy (SEM), and zeta potential measurements. The modified bottles were then utilized for the extraction of analytes with diverse acid-base characteristics, including drugs, illicit drugs, and pesticides, from saliva, urine, and surface water samples. The studied analytes can be adsorbed on the surface of the LBL film mainly through hydrogen bonding and/or hydrophobic interactions. Remarkably high extraction percentages of up to 92 % were achieved, accompanied by an impressive enhancement in the analytical signal of up to 12 times when the sample volume was increased from 0.7 to 10 mL. These results highlight the outstanding extraction and sorption capabilities of the developed material. Additionally, the (PDDA/MWCNTs)10 films exhibited notable resistance to extraction and desorption processes, enabling their reuse for at least 5 cycles. The straightforward and cost-effective fabrication of these sorbent materials using the LBL technique, combined with the ability to extract target compounds during sample transportation and/or storage, renders this sample preparation method a promising alternative.

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The layer-by-layer (LbL) technique has been proven to be one of the most versatile approaches in order to fabricate functional nanofilms. The use of simple and inexpensive procedures as well as the possibility to incorporate a very wide range of materials through different interactions have driven its application in a wide range of fields. On the other hand, field-effect transistors (FETs) are certainly among the most important elements in electronics. The ability to modulate the flowing current between a source and a drain electrode via the voltage applied to the gate electrode endow these devices to switch or amplify electronic signals, being vital in all of our everyday electronic devices. In this topical review, we highlight different research efforts to engineer field-effect transistors using the LbL assembly approach. We firstly discuss on the engineering of the channel material of transistors via the LbL technique. Next, the deposition of dielectric materials through this approach is reviewed, allowing the development of high-performance electronic components. Finally, the application of the LbL approach to fabricate FETs-based biosensing devices is also discussed, as well as the improvement of the transistor's interfacial sensitivity by the engineering of the semiconductor with polyelectrolyte multilayers.

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The harmful effects on the environment caused by the indiscriminate use of synthetic plastics and the inadequate management of post-consumer waste have given rise to efforts to redirect this consumption to bio-based economic models. In this sense, using biopolymers to produce materials is a reality for food packaging companies searching for technologies that allow these materials to compete with those from synthetic sources. This review paper focused on the recent trends in multilayer films with the perspective of using biopolymers and natural additives for application in food packaging. Firstly, the recent developments in the area were presented concisely. Then, the main biopolymers used (gelatin, chitosan, zein, polylactic acid) and main methods for multilayer film preparation were discussed, including the layer-by-layer, casting, compression, extrusion, and electrospinning methods. Furthermore, we highlighted the bioactive compounds and how they are inserted in the multilayer systems to form active biopolymeric food packaging. Furthermore, the advantages and drawbacks of multilayer packaging development are also discussed. Finally, the main trends and challenges in using multilayer systems are presented. Therefore, this review aims to bring updated information in an innovative approach to current research on food packaging materials, focusing on sustainable resources such as biopolymers and natural additives. In addition, it proposes viable production routes for improving the market competitiveness of biopolymer materials against synthetic materials.

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The development of biodegradable packaging materials has been drawing attention worldwide to minimize the environmental impact of traditional petroleum-based plastics. Nevertheless, it is challenging to obtain bio-based materials with suitable properties for packaging applications. Films produced from a single biopolymer often lack some important properties. An alternative to overcome this limitation is the multilayer assembly. Under this technology, two or more materials with specific and complementary properties are combined into a single-layered structure, thus improving the performance of bio-polymer plastics. This review presents the main aspects of bio-based multilayer film production technologies, discussing their advantages and disadvantages, which have to be considered to produce the most suitable film for each specific application. Most of the studies reported that such films resulted in increased mechanical performance and decreased water, oxygen, and dioxide carbon permeability. This approach allows the addition of compounds leading to antioxidant or antibacterial activity. Finally, a discussion about the future challenges is also presented.

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Drug delivery carriers are considered an encouraging approach for the localized treatment of disease with minimum effect on the surrounding tissue. Particularly, layer-by-layer releasing particles have gained increasing interest for their ability to develop multifunctional systems able to control the release of one or more therapeutical drugs and biomolecules. Although experimental methods can offer the opportunity to establish cause and effect relationships, the data collection can be excessively expensive or/and time-consuming. For a better understanding of the impact of different design conditions on the drug-kinetics and release profile, properly designed mathematical models can be greatly beneficial. In this work, we develop a continuum-scale mathematical model to evaluate the transport and release of a drug from a microparticle based on an inner core covered by a polymeric shell. The present mathematical model includes the dissolution and diffusion of the drug and accounts for a mechanism that takes into consideration the drug biomolecules entrapped into the polymeric shell. We test a sensitivity analysis to evaluate the influence of changing the model conditions on the total system behavior. To prove the effectiveness of this proposed model, we consider the specific application of antibacterial treatment and calibrate the model against the data of the release profile for an antibiotic drug, metronidazole. The results of the numerical simulation show that ∼85% of the drug is released in 230 h, and its release is characterized by two regimes where the drug dissolves, diffuses, and travels the external shell layer at a shorter time, while the drug is released from the shell to the surrounding medium at a longer time. Within the sensitivity analysis, the outer layer diffusivity is more significant than the value of diffusivity in the core, and the increase of the dissolution parameters causes an initial burst release of the drug. Finally, changing the shape of the particle to an ellipse produces an increased percentage of drugs released with an unchanged release time.

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BACKGROUND: Alzheimer's disease (AD) is the most common form of dementia and affect more than 50 million people worldwide. Thus, there is a high demand by non-invasive methods for an early diagnosis. This work explores the AD diagnostic using the amyloid beta 1-40 (Aß40) peptide encapsulated into dipalmitoyl phosphatidyl glycerol (DPPG) liposomes and immobilized on polyethylene imine previously deposited on screen-printed carbon electrodes to detect autoantibodies against Aß40, a potential biomarker found in plasma samples. METHODS: The immunosensor assembly was accompanied by atomic force microscopy (AFM) images that showed globular aggregates from 20 to 200 nm corresponding liposomes and by cyclic voltammetry (CV) through increase of the voltammogram area each material deposited. After building the immunosensor, when it was exposed to antibody anti-Aß40, there was an increase in film roughness of approximately 9 nm, indicating the formation of the immunocomplex. RESULTS: In the detection by CV, the presence of specific antibody, in the range of 0.1 to 10 µg/ml, resulted in an increase in the voltammograms area and current in 0.45 V reaching 3.2 µA.V and 5.7 µA, respectively, in comparison with the control system, which remained almost unchanged from 0.1 µg/ml. In patient samples, both cerebrospinal fluid (CSF) and plasma, was possible separated among positive and negative samples for AD using CV profile and area, with a difference of 0.1 µA.V from the upper error bar of healthy samples for CSF sample and 0.6 µA.V for plasma sample. CONCLUSIONS: These results showed the feasibility of the method employed for the non-invasive diagnostic of Alzheimer's disease detecting natural autoantibodies that circulate in plasma through a simple and easy-to-interpret method.

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The development of blood-interacting surfaces is critical to fabricate biomaterials for medical use, such as prostheses, implants, biosensors, and membranes. For instance, thrombosis is one of the leading clinical problems when polymer-based materials interact with blood. To overcome this limitation is necessary to develop strategies that limit platelets adhesion and activation. In this work, hyaluronan (HA)/chitosan (Chi) based-films, recently reported in the literature as platforms for tumor cell capture, were developed and, subsequently, functionalized with sulfated chitosan (ChiS) using a layer-by-layer technique. ChiS, when compared to native Chi, presents the unique abilities to confer anti-thrombogenic properties, to reduce protein adsorption, and also to limit calcification. Film physicochemical characterization was carried out using FTIR and XPS for chemical composition assessment, AFM for the surface morphology, and contact angle for hydrophilicity evaluation. The deposition of ChiS monolayer promoted a decrease in both roughness and hydrophilicity of the HA/Chi films. In addition, the appearance of sulfur in the chemical composition of ChiS-functionalized films confirmed the film modification. Biological assay indicated that the incorporation of sulfated groups limited platelet adhesion, mainly because a significant reduction of platelets adhesion to ChiS-functionalized films was observed compared to HA/Chi films. On balance, this work provides a new insight for the development of novel antithrombogenic biomaterials, opening up new possibilities for devising blood-interaction surfaces.

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A sensitive detection of carbohydrate antigen 15-3 (CA15-3) levels may allow for early diagnosis and monitoring the treatment of breast cancer, but this can only be made in routine clinical practice if low-cost immunosensors are available. In this work, we developed a sandwich-type electrochemical immunosensor capable of rapid detection of CA15-3 with an ultra-low limit of detection (LOD) of 0.08 fg mL-1 within a wide linear concentration range from 0.1 fg mL-1 to 1 µg mL-1. The immunosensor had a matrix of a layer-by-layer film of Au nanoparticles and reduced graphene oxide (Au-rGO) co-electrodeposited on screen-printed carbon electrodes (SPCE). The high sensitivity was achieved by using secondary antibodies (Ab2) labeled with horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2) as signal amplifiers, and hydroquinone (HQ) was used as an electron mediator. The immunosensor was selective for CA15-3 in human serum and artificial saliva samples, robust, and stable to permit storage at 4 °C for more than 30 days. With its high performance, the immunosensor may be incorporated into future point-of-care (POC) devices to determine CA15-3 in distinct biological fluids, including in blood and saliva samples.

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Electrostatic interaction between protein and polysaccharides could influence structured liquid oil stability when emulsification is used for this purpose. The objective of this work was to structure sunflower oil forming emulsions and High Internal Phase Emulsions (HIPEs) using pea protein (PP) and xanthan gum (XG) as a stabilizer, promoting or not their electrostatic attraction. The 60/40 oil-in-water emulsions were made varying the pH (3, 5, and 7) and PP:XG ratio (4:1, 8:1, and 12:1). To form HIPEs, samples were oven-dried and homogenized. The higher the pH, the smaller the droplet size (Emulsions: 15.60-43.96 µm and HIPEs: 8.74-20.38 µm) and the oil release after 9 weeks of storage at 5 °C and 25 °C (oil loss < 8%). All systems had weak gel-like behavior, however, the values of viscoelastic properties (G' and G″) increased with the increment of PP:XG ratio. Stable emulsions were obtained at pHs 5 and 7 in all PP:XG ratios, and at pH 3 in the ratio 4:1. Stable HIPEs were obtained at pH 7 in the ratios PP:XG 4:1, 8:1, and 12:1, and at pH 5 at PP:XG ratio 4:1. All these systems presented different characteristics that could be exploited for their application as fat substitutes.

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Early diagnosis of cancer is crucial for therapeutic methods to be more effective and to decrease the mortality rate due to this disease. Current diagnostic methods include imaging techniques that require expensive equipment and specialized personnel, making it difficult to apply them to many patients. To overcome these limitations, many biosensors have been developed to monitor cancer biomarkers. Here, we report on the electrochemical biosensor for selective detection of tumor cells using a simple and low-cost methodology. Layer-by-layer (LbL) self-assembly was used to modify indium tin oxide (ITO) electrodes with alternating layers of polyallylamine hydrochloride (PAH) and folic acid (FA), which binds to overexpressed folate receptors alpha (FRα) in tumor cells. The LbL-based biosensor showed high sensitivity in detecting cervical cancer cells (HeLa cells) using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). A linear dependence with the logarithm cell concentration was observed and excellent detection limits were found, 4 cells mL-1 and 19 cells mL-1 for EIS and CV measurements, respectively. The developed biosensor also presented great reproducibility (RSD = 1.7%) and repeatability (RSD = 1.8%). The selectivity was confirmed after the biosensor interaction with healthy cells (HMEC cells), which did not produce significant changes in the electrochemical signals. Furthermore, it was demonstrated that selective detection of tumor cells occurs via an interaction with FA. The LbL-based biosensor provides a simple, accurate, and cost-effective platform to be applied in the early diagnosis of cancer.

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The main objective of the present work was to design a biomimetic free-standing multilayered PEM film, constructed by the layer-by-layer (LbL) assembly approach, based on natural biopolymers and intended to recreate the complex mucus-mimetic matrices in order to provide mechanistic insights into biophysical interactions between drugs and the physiological gel-forming mucin network of mucus that covers the mucosal epithelia named as(CS/ALG)/(PGM) PEM film. The obtained results indicate that mucin may delay or increase drug precipitation on the mucus layer, depending on specific drug-mucin interactions driving drug supersaturation or drug crystallization phenomena. It was found that the drug lipophilicity characteristics governed the mucin binding degree, which had an influencing role on the drug translocation across this gel-like hydrogel. Moreover, the ionization of these drugs did not have a significant role on the drug binding ability to mucin as much as the lipophilicity properties did. The (CS/ALG)/(PGM) PEM film may be a promising tool to routine testing drug-mucus interactions to evaluate biophysical interactions between this protective barrier of the organism against different drug therapeutic products or external aggressive agents, leading to the optimization of drug delivery products or drugs for particular disease states.

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The food industry has increased its interest in using "consumer-friendly" and natural ingredients to produce food products. In the case of emulsifiers, one of the possibilities is to use biopolymers with emulsification capacity, such as octenyl succinic anhydride modified starch, which can be used in combination with other polysaccharides, such as chitosan and carboxymethylcellulose, in order to improve the capacity to protect bioactive compounds. In this work, multilayer nano-emulsion systems loaded with oregano essential oil were produced by high energy methods and characterized. The process optimization was carried out based on the evaluation of particle size, polydispersity index, and zeta potential. Optimal conditions were achieved for one-layer nano-emulsions resulting in particle size and zeta potential of 180 nm and -42 mV, two layers (after chitosan addition) at 226 nm and 35 mV, and three layers (after carboxymethylcellulose addition) of 265 nm and -1 mV, respectively. The encapsulation efficiency of oregano essential oil within nano-emulsions was 97.1%. Stability was evaluated up to 21 days at 4 and 20 °C. The three layers nano-emulsion demonstrated to be an efficient delivery system of oregano essential oil, making 40% of the initial oregano essential oil available versus 13% obtained for oregano essential oil in oil, after exposure to simulated digestive conditions.

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HYPOTHESIS: Dimensionally stable electroactive films displaying spatially addressed redox sites is still a challenging goal due to gel-like structure. Polyelectrolyte and surfactants can yield highly mesostructured films using simple buildup strategies as layer-by-layer. The use of redox modified surfactants is expected to introduce order and an electroactive response in thin films. EXPERIMENTS: The assembly of polyacrylic acid and different combinations of redox-modified and unmodified hexadecyltrimethylammonium bromide yields highly structured and electroactive thin films. The growth, viscoelastic properties, mass, and electron transport of these films were studied by combining electrochemical and quartz crystal balance with dissipation experiments. FINDINGS: Our results show that the films are highly rigid and poorly hydrated. The mass and charge transport reveal that the ingress (egress) of the counter ions during the electrochemical oxidation (reduction) is accompanied with a small amount of water, which is close to their hydration sphere. Thus, the generated mesostructured films present an efficient charge transport with negligible changes in their structures during the electron transfer process. The control over the meso-organization and its stability represents a promising tool in the construction of devices where the vectorial transfer of electrons, or ions, is required.

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Folate receptor alpha (FR-α) is a glycoprotein overexpressed in tumor cell surfaces, especially in gynecologic cancers, and can be used as a biomarker for diagnostics. Currently, FRα is quantified by positron emission tomography (PET) or fluorescence imaging techniques. However, these methods are costly and time-consuming. We report on the development of an electrochemical biosensor for FRα detection based on the use of nanostructured layer-by-layer (LbL) films as modified electrodes. Multilayer films were deposited on indium tin oxide (ITO) electrodes by the alternately assembling of positively charged polyallylamine hydrochloride (PAH) and negatively charged folic acid (FA), used as the biorecognition element. UV-vis and FTIR spectroscopies revealed the successful PAH and FA adsorption on ITO. Devices performance was evaluated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The [PAH/FA] films presented a good reproducibility (RSD of 1.12%) and stability when stored in the Tris-HCl solution (RSD 6.7%). The biosensor electrochemical response exhibited a linear relationship with FRα concentration in the range from 10 to 40 nM. The limit of detection reached for CV and EIS measurements were 0.7 and 1.5 nM, respectively. As a proof-of-concept, we show that the devices can differenciate tumor cells from healthy cell, showing an excellent selectivity. The biosensor device based on [PAH/FA] films represents a promising strategy for a simple, rapid, and low-cost cancer diagnosis through FRα quantification on the surface of cancer cells.

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Implant placement is an important repair method in dentistry and orthopedics. Increasing efforts have focused on optimizing the biocompatibility and osseointegration properties of titanium (Ti) and Ti-based alloys. In this work, Ti-based alloys were modified by the layer-by-layer (LbL) technique, which is a simple and versatile method for surface modification. The morphology and chemical structure of LbL films of poly(sodium 4-styrenesulfonate) (PSS) and Ti dioxide (TiO2) nanoparticles were first characterized employing ultraviolet-visible and Fourier-transform infrared spectroscopies as well as atomic force microscopy for further application in Ti-based alloy implants. The changes provoked by the LbL PSS/TiO2 film on the Ti-based alloy surfaces were then investigated by scanning electron microscopy and micro-Raman techniques. Finally, in vivo tests (immunolabeling and biomechanical analysis) performed with screw implants in rats suggested that PSS/TiO2 multilayers promote changes in both topography and chemical surface properties of the screw, providing beneficial effects for osteoblast activity. This simple and relatively low-cost growth process can open up possibilities to improve dental implants and, probably, bone implants in general.

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Herein, poly (N-(4-aminophenyl) methacrylamide))-carbon nano-onions (PAPMA-CNOs = f-CNOs) and anilinated-poly (ether ether ketone) (AN-PEEK) have synthesized, and AN-PEEK/f-CNOs composite thin films were primed via layer-by-layer (LbL) self-assembly for stimuli-responsive drug release. The obtained thin films exhibited pH-responsive drug release in a controlled manner; pH 4.5 = 99.2% and pH 6.5 = 59.3% of doxorubicin (DOX) release was observed over 15 days. Supramolecular π-π stacking interactions between f-CNOs and DOX played a critical role in controlling drug release from thin films. Cell viability was studied with human osteoblast cells and augmented viability was perceived. Moreover, the thin films presented 891.4 ± 8.2 MPa of the tensile strength (σult), 43.2 ± 1.1 GPa of Young's modulus (E), and 164.5 ± 1.7 Jg-1 of toughness (K). Quantitative scrutiny revealed that the well-ordered aligned nanofibers provide critical interphase, and this could be responsible for augmented tensile properties. Nonetheless, a pH-responsive and mechanically robust biocompatible thin-film system may show potential applications in the biomedical field.

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Electrochemical immunosensors have been developed to determine the carbohydrate antigen 19-9 (CA19-9). They are based on screen-printed carbon electrodes (SPCEs) coated with layer-by-layer (LbL) films of carbon black (CB) and polyelectrolytes. Owing to a suitable choice of LbL film architecture, the procedures for immobilization of anti-CA19-9 antibodies on the electrode surfaces were straightforward. Mechanically flexible immunosensors were capable of detecting CA19-9 within a dynamic range of 0.01 to 40 U mL-1 and a limit of detection of 0.07 U mL-1 using differential pulse voltammetry. In addition to detecting CA19-9 at clinically relevant concentrations for pancreatic cancer in standard solutions, the immunosensors provide the determination of CA19-9 on cell lysate and human serum samples. Using LbL films led to immunosensors with superior performance compared to similar systems obtained by drop casting. The fabrication of this relatively simple, inexpensive platform is a demonstration that SPCEs modified with cost-effective materials are able to detect cancer biomarkers and may be adapted to other disposable immunosensors. Graphical abstract Schematic representation of assembly and characterization of electrochemical immunosensors for the determination of carbohydrate antigen 19-9 based on printed electrodes modified with composites of carbon black and polyelectrolyte films.

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The increasing need for point-of-care diagnosis has sparked the development of label-free sensing platforms, some of which are based on impedance measurements with biological cells. Here, interdigitated electrodes were functionalized with layer-by-layer (LbL) films of hyaluronan (HA) and chitosan (CHI) to detect prostatic tumor cells (PC3 line). The deposition of LbL films was confirmed with atomic force microscopy and polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS), which featured the vibrational modes of the HA top layer capable of interacting specifically with glycoprotein CD44 receptors overexpressed in tumor cells. Though the CHI/HA LbL films cannot be considered as a traditional biosensor due to their limited selectivity, it was possible to distinguish prostate tumor cells in the range from 50 to 600 cells/µL in in vitro experiments with impedance spectroscopy. This was achieved by treating the impedance data with information visualization methods, which confirmed the distinguishing ability of the films by observing the absence of false positives in a series of control experiments. The CD44-HA interactions may, therefore, be exploited in clinical analyses and point-of-care diagnostics for cancer, particularly if computational methods are used to process the data.

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Electroactive thin films are an important element in the devices devoted to energy conversion, actuators, and molecular electronics, among others. Their build-up by the layer-by-layer technique is an attractive choice since a fine control over the thickness and composition can be achieved. However, most of the assemblies described in the literature show a lack of internal order, and their thicknesses change upon oxidation-state alterations. In this work, we describe the formation of layer-by-layer assemblies of redox surfactants and polyelectrolytes that leads to the construction of mesoscale organized electroactive films. In contrast to thin films prepared with traditional redox polymers, here, the redox surfactant does not only allow the control of the film meso-organization (from 2D hexagonal to circular hexagonal phases) but it also allows the control of the number and position of the redox centers. Finally, these films show high stability and a negligible structural deformation under redox-state changes.