Synthetic Nanoclay Research Articles

Exploring the Interaction of Lipid Bilayers with Curcumin-Laponite Nanoparticles: Implications for Drug Delivery and Therapeutic Applications.

Curcumin, the active compound in turmeric, is renowned for its anti-inflammatory, antioxidant, and antimicrobial properties, making it beneficial for treating conditions like arthritis, neurodegenerative diseases, and various cancers. Despite its promising therapeutic potential, curcumin's poor bioavailability-due to its rapid metabolism and low solubility-limits its clinical efficacy. To address this, recent research has focused on enhancing curcumin delivery using nanoparticles, liposomes, and novel nanomaterials. Among these, laponite, a synthetic nanoclay, has shown promise in improving curcumin delivery due to its unique properties, including large surface area, dual charge, and stability in solution. This study explores the use of curcumin-laponite nanoparticles as carrier vehicles for controlled delivery to in vitro model membranes. Utilizing advanced techniques such as neutron reflectometry, atomic force microscopy, quartz crystal microbalance with dissipation, and infrared spectroscopy, the interaction between curcumin-laponite nanoparticles and solid-supported lipid bilayers is monitored, revealing enhanced stability and controlled release of curcumin across the membrane. These findings pave the way for the development of curcumin-based therapies targeting cardiovascular, neurological, and oncological diseases, leveraging the synergistic effects of curcumin's biological activity and laponite's delivery capabilities.

Rheologically improved microemulsion for deactivation of simulants of blister and nerve agents

The efficiency of decontamination of blister and nerve agents was studied using the example of nucleophilic decomposition of paraoxone (O,O-diethyl-O-4-nitrophenyl phosphate) and oxidation of methylphenyl sulfide. Hydrogen peroxide solutions in an oil-in-water microemulsion containing synthetic nanoclay Laponite EP and polyvinylpyrrolidone polymer were studied as reactive decontamination systems. The base of the microemulsion consisted of an aqueous phase, a codetergent (isopropanol), oil (hexane), with a variation of detergent (cetylpyridinium chloride, sodium dodecyl sulfate, and Triton X-100). It was shown that the solubility of paraoxone and methylphenyl sulfide in the studied microemulsions increases by an average of 100 times or more compared to the solubility in water, and the substrate binding constants are 2–3 times higher than the binding constants in similar microemulsion media. It was found that the presence of nanoclay in the microemulsion provides a catalytic effect, i.e. an increase in the rate of decomposition of paraoxone and methylphenyl sulfide by at least 2 times. In addition, nanoclay thickens the microemulsion and, together with the polymer, increases the viscosity of the reaction medium. The determined kinetic parameters of decontamination and solubility of substrates allow us to conclude that the use of the investigated microemulsion system provides an acceleration of nucleophilic substitution and oxidation reactions by 150–350 times compared to the reaction rate in water.

Hemolytic Activity and Cytotoxicity of Synthetic Nanoclays with Montmorillonite Structure for Medical Applications.

The factors influencing the appearance of toxicity in samples of synthetic montmorillonite with a systematically changing chemical composition Nax(Al, Mg)2-3Si4O10(OH)2 nH2O, which are potentially important for their use in medicine as drug carriers, targeted drug delivery systems, entero- and hemosorbents have been studied. Samples synthesized under hydrothermal conditions had the morphology of nanolayers self-organized into the nanosponge structures. The effect of the aluminum content, particle sizes, porosity, and ζ-potential of the samples on their toxicity was studied. The cytotoxic effect of the samples on eukaryotic cells Ea. hy 926 was determined using the MTT assay. The hemolytic activity of the samples in the wide concentration range in relation to human erythrocytes was also estimated. It has been established that the toxicity of aluminosilicate nanoparticles can be significantly reduced by correctly selecting their synthesis conditions and chemical composition, which opens up the opportunities for their use in medicine.

Controlled Release of Epigenetically-Enhanced Extracellular Vesicles from a GelMA/Nanoclay Composite Hydrogel to Promote Bone Repair.

Extracellular vesicles (EVs) have garnered growing attention as promising acellular tools for bone repair. Although EVs’ potential for bone regeneration has been shown, issues associated with their therapeutic potency and short half-life in vivo hinders their clinical utility. Epigenetic reprogramming with the histone deacetylase inhibitor Trichostatin A (TSA) has been reported to promote the osteoinductive potency of osteoblast-derived EVs. Gelatin methacryloyl (GelMA) hydrogels functionalised with the synthetic nanoclay laponite (LAP) have been shown to effectively bind, stabilise, and improve the retention of bioactive factors. This study investigated the potential of utilising a GelMA-LAP hydrogel to improve local retention and control delivery of epigenetically enhanced osteoblast-derived EVs as a novel bone repair strategy. LAP was found to elicit a dose-dependent increase in GelMA compressive modulus and shear-thinning properties. Incorporation of the nanoclay was also found to enhance shape fidelity when 3D printed compared to LAP-free gels. Interestingly, GelMA hydrogels containing LAP displayed increased mineralisation capacity (1.41-fold) (p ≤ 0.01) over 14 days. EV release kinetics from these nanocomposite systems were also strongly influenced by LAP concentration with significantly more vesicles being released from GelMA constructs as detected by a CD63 ELISA (p ≤ 0.001). EVs derived from TSA-treated osteoblasts (TSA-EVs) enhanced proliferation (1.09-fold), migration (1.83-fold), histone acetylation (1.32-fold) and mineralisation (1.87-fold) of human bone marrow stromal cells (hBMSCs) when released from the GelMA-LAP hydrogel compared to the untreated EV gels (p ≤ 0.01). Importantly, the TSA-EV functionalised GelMA-LAP hydrogel significantly promoted encapsulated hBMSCs extracellular matrix collagen production (≥1.3-fold) and mineralisation (≥1.78-fold) in a dose-dependent manner compared to untreated EV constructs (p ≤ 0.001). Taken together, these findings demonstrate the potential of combining epigenetically enhanced osteoblast-derived EVs with a nanocomposite photocurable hydrogel to promote the therapeutic efficacy of acellular vesicle approaches for bone regeneration.

Shear-thinning hydrogels containing reactive oxygen species-responsive nanoparticles for salvianolic acid B delivery to rescue oxidative damaged HUVECs

Reactive oxygen species (ROS)-induced oxidative stress plays a key role in the peripheral arterial disease (PAD). Salvianolic acid B (SAB) is a natural phenolic compound and possesses antioxidant properties. However, the poor bioavailability of hydrophilic SAB may limit its applications. Boronic ester-based nanoparticles (NPs) as ROS‐responsive carriers can release drug rapidly and selectively at damaged tissue. Dextran, a polysaccharide, has been used to decrease the platelet aggregation in PAD patients. Laponite, a synthetic nanoclay, has been widely used in biomedical applications. In the study, the laponite hydrogels containing ROS-responsive dextran-based NPs was developed as a carrier for SAB delivery. The synthesis processes of boronic ester modified dextran (PHB-DEX) were characterized by Fourier transform infrared spectrophotometer and thermogravimetry analyzer. The PHB-DEX NP was ∼195.3 nm with spherical structure and could be hydrolyzed completely within 9 min under oxidative stress. Optimal concentration of SAB to treat HUVECs was ∼100 μM. The results of scanning electron microscopy demonstrated that SAB-loaded NPs (SAB-NPs) were well dispersed in laponite hydrogels matrix. The rheological behaviors of laponite containing SAB-NPs (LNPs) showed the shear-thinning properties and increase of fluidity when removing shear stress. The LNPs with sustained drug release properties could scavenge ROS and rescue human umbilical vein endothelial cells from oxidative damage via decrease of the inflammatory level (TNF, IL-1α, IL-1β, IL-6, and MMP-9) and apoptosis. The biocompatibility of the developed hydrogels has been demonstrated in-vivo. The results suggested that the developed LNPs might have potentials for PAD treatment.

Uses of Nanoclays and Adsorbents for Dye Recovery: A Textile Industry Review

Wastewater recovery is one of the most pressing contaminant-related subjects in the textile industry. Many cleaning and recovery techniques have been applied in recent decades, from physical separation to chemical separation. This work reviews textile wastewater recovery by focusing on natural or synthetic nanoclays in order to compare their capabilities. Presently, a wide variety of nanoclays are available that can adsorb substances dissolved in water. This review summarizes and describes nanoclay modifications for different structures (laminar, tubular, etc.) to compare adsorption performance under the best conditions. This adsorbent capacity can be used in contaminant industries to recover water that can be used and be recontaminated during a second use to close the production circle. It explores and proposes future perspectives for the nanoclay hybrid compounds generated after certain cleaning steps. This is a critical review of works that have studied adsorption or desorption procedures for different nanoclay structures. Finally, it makes a future application proposal by taking into account the summarized pros and cons of each nanoclay. This work addresses contaminant reuse, where part of the employed dyes can be reused in printing or even dyeing processes, depending on the fixing capacity of the dye in the nanoclay, which is herein discussed.

De Novo Design of Functional Coassembling Organic-Inorganic Hydrogels for Hierarchical Mineralization and Neovascularization.

Synthetic nanostructured materials incorporating both organic and inorganic components offer a unique, powerful, and versatile class of materials for widespread applications due to the distinct, yet complementary, nature of the intrinsic properties of the different constituents. We report a supramolecular system based on synthetic nanoclay (Laponite, Lap) and peptide amphiphiles (PAs, PAH3) rationally designed to coassemble into nanostructured hydrogels with high structural integrity and a spectrum of bioactivities. Spectroscopic and scattering techniques and molecular dynamic simulation approaches were harnessed to confirm that PAH3 nanofibers electrostatically adsorbed and conformed to the surface of Lap nanodisks. Electron and atomic force microscopies also confirmed an increase in diameter and surface area of PAH3 nanofibers after coassembly with Lap. Dynamic oscillatory rheology revealed that the coassembled PAH3-Lap hydrogels displayed high stiffness and robust self-healing behavior while gas adsorption analysis confirmed a hierarchical and heterogeneous porosity. Furthermore, this distinctive structure within the three-dimensional (3D) matrix provided spatial confinement for the nucleation and hierarchical organization of high-aspect ratio hydroxyapatite nanorods into well-defined spherical clusters within the 3D matrix. Applicability of the organic–inorganic PAH3-Lap hydrogels was assessed in vitro using human bone marrow-derived stromal cells (hBMSCs) and ex vivo using a chick chorioallantoic membrane (CAM) assay. The results demonstrated that the organic–inorganic PAH3-Lap hydrogels promote human skeletal cell proliferation and, upon mineralization, integrate with the CAM, are infiltrated by blood vessels, stimulate extracellular matrix production, and facilitate extensive mineral deposition relative to the controls.

Hyaluronic Acid/Laponite Clay Nanocomposites‐Based Hydrogels for 3D Bioprinting Applications

Hyaluronic acid (HA) is a glycosaminoglycan with excellent physicochemical and biological properties and represents a potential component to constitute inks used in tissues and organs 3D bioprinting process. On the other hand, it does not have an adequate degree of rigidity necessary for the structural maintenance of printed components. Laponite (Lap) is a synthetic nanoclay capable of increasing the rheological properties of polymeric hydrogels. The present study aimed to develop and characterize HA/Lap clay nanocomposites-based hydrogels for the constitution of inks for 3D bioprinting, considering the Lap potential to improve the rheological characteristics of HA. For this, HA (12 mg/mL) and Laponite-XLG (50 mg/mL) hydrogels were initially produced. Three additional hydrogels, composed from the association of different percentages of HA and Lap samples (w/w), were manufactured (HA/Lap 75:25%, 50:50%, and 25:75%). After constitution, all hydrogels samples were characterized by rheological and spectrophotometric analysis (Fourier-Transform Infrared Spectroscopy-FTIR). Finally, they were submitted to an in vitro cytotoxicity test, with cell viability (human fibroblasts-GM07492) established by a spectrophotometric Resazurin/Resorufin method. The rheological analysis results demonstrate a directly proportional increase in hydrogel viscosity concerning the increase in Lap percentage. The values of HA, Lap, and experimental HA/Lap clay nanocomposites-based hydrogels samples (75:25%, 50:50%, and 25:75%) were 4.9, 12.7, 4.0, 9.4, and 12.0 Pa.s, respectively. In FTIR analysis, bands (wavenumber 1000.7 cm-1) were identified in the Lap and HA/Lap samples, corresponding to the stretching of the Si-O interaction of Lap's tetrahedral layer. The viability tests demonstrated the non-toxic profile of the HA, Lap, and the hydrogels resulting from their associations. Such results demonstrate the biological safety of HA/Lap samples and the rheological modifying role from Lap on developed hydrogels. The viscosity levels achieved, especially in the proportions of HA/Lap of 50:50% and 25:75%, demonstrate its potential in the constitution of inks for use in 3D bioprinting. Further research should contribute to establishing the ideal composition (percentage of HA and Lap) and the printability characteristics of the HA/Lap clay nanocomposites-based hydrogels.

Synthetic Nanoclay Gels Do Not Cause Skin Irritation in Healthy Human Volunteers.

Synthetic clays are promising biomaterials for delivery of therapeutic molecules in regenerative medicine. However, before their use can be translated into clinical applications, their safety must be assessed in human volunteers. The aim of this study was to test the hypothesis that a synthetic nanoclay (LAPONITE) does not cause irritation to the human skin. To achieve this, a nanoclay gel at two different concentrations (1.5 and 3% w/v) was applied on the forearm of healthy volunteers for 24 h. 1% sodium lauryl sulfate (SLS) and 3% (w/v) polyacrylic acid were used as the positive and negative controls, respectively. The compromise in the skin barrier function was measured by trans-epidermal water loss (TEWL), erythema by spectroscopic measurements, and skin inflammatory biomarkers (IL-1α and IL-1RA) by the enzyme-linked immunosorbent assay. We found that the nanoclay caused no prolonged increase in TEWL, erythema, or induction of inflammatory cytokines. This was in contrast to 1% SLS, a known irritant, which induced significant increases in both skin erythema and TEWL. We conclude that the nanoclay is not an irritant and is thus suitable for therapeutic interventions at the skin surface.

Dr Barbara S. Neumann: clay scientist and industrial pioneer; creator of Laponite®

In 2019, BYK Additives (Widnes, UK; www.byk.com) marked the 55th anniversary of the discovery by Dr Barbara Zsusanna (Susanna) Neumann of the extraordinary product known as Laponite®. The range of Laponite® products developed in the UK during the early 1960s is one of the first examples of truly nanodimensional materials manufactured on an industrial scale, at a time when the field of nanotechnology was only being hinted at (Feynman, 1959). These hectorite-like synthetic nanoclays with very unusual properties have been an enduring commercial success for the UK company that first patented and introduced them to the market, Laporte Industries, which is now a part of the BYK company. The Laponite® brand has proved tremendously popular with academic and industrial scientists worldwide, being cited in >3000 patents and >2500 published academic articles.

Synthesis and Viscoelastic Properties of Smart Hydrogel

Here we report the synthesis and viscoelastic properties of smart hydrogels based on N-isopropylacrylamide, cationic (3-acrylamidopropyl)trimethylammonium chloride and nanoclay. Hydrogels were prepared by aqueous free radical polymerization. The effect of some salts, N,N '-methylenebisacrylamide, (3-acrylamidopropyl)trimethylammonium chloride and nanoclay content on the viscoelastic properties was studied. Also volume phase transition temperature and thermal behavior of the prepared hydrogels were investigated. Synthetic nanoclay and anionic groups of the bind to the cationic co-monomer units and significantly affected the viscoelasticity and thermal properties of the hydrogels. DSC measurements showed that the volume phase transition temperature of hydrogels depended on nanoclay content. By introducing of co-monomer, 250 mM solution of NaCl 15 mM bis(trifluoromethane)sulfonimide lithium salt (LiNTF2) and laponite nanoclay, a 10, 4, and 3.8 fold increase in elastic module was obtained, respectively, compared to that of the homopolymer PNIPAM hydrogel. With a temperature change from 20 to 45°C for the homopolymer PNIPAM hydrogel in 15 mM LiNTF2, the elastic module grew 5 times larger.

Bioactive and Elastic Nanocomposites with Antimicrobial Properties for Bone Tissue Regeneration.

Bone injuries represent a major challenge in the medical field. The commonly used treatments for bone regeneration rely on the use of bone grafts that are usually associated with complications such as donor site morbidity, disease transmission, high cost, and lack of availability. Bone tissue engineering has become a golden solution for the repair of bone injuries by regenerating the damaged biological tissues using biocompatible scaffolds. However, most of the tissue engineered scaffolds do not possess the combined properties of high elasticity, appropriate stiffness, biocompatibility, osteoinductivity, and antimicrobial properties. In this study, we engineered bioactive and antimicrobial nanocomposites that can promote bone formation while simultaneously provide a barrier against bacterial infections commonly associated with bone implants. We used PEGylated polyglycerol sebacate as nanocomposites base, which was functionalized with Laponite nanosilicates, a synthetic nanoclay, and an antimicrobial peptide (AMP). The successful synthesis of the PEGylated polyglycerol sebacate and Laponite incorporation within the nanocomposites were confirmed through nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy (FTIR). The scaffolds had an elastic modulus and ultimate tensile strength within a range of 3.8-4.7 MPa and 1.5-3 MPa, respectively. Furthermore, the scaffolds loaded with antimicrobial peptide exhibited a significant antimicrobial activity against both Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. The in vitro cytocompatibility tests showed >90% viability of preosteoblast (W-20-17) cells. Moreover, in vitro differentiation assays demonstrated the scaffolds' ability to promote osteogenic differentiation of W-20-17. Collectively, the nanocomposites containing Laponite and antimicrobial peptide were proven to have osteoinductive and antimicrobial activity, making them desirable for bone tissue engineering applications.

Dynamic properties of a sand–nanoclay composite

The paper describes the influence of 1–3% (by dry mass of sand) Laponite, a highly plastic synthetic nanoclay, on the dynamic properties of Ottawa sand, based on undrained resonant column tests. The effect of Laponite depends on the amount added, the confining stress and consolidation time. With 1% Laponite, there is an increase in the very small-strain shear stiffness at all confining stresses, which increases with extended consolidation time, reflecting the thixotropic nature of the nanoclay. Added Laponite also produces an increase in small-strain damping, an extension of the linear strain threshold; and it delays the generation of excess pore pressure, degradation of shear modulus and increase in damping with shear strain. These effects, which become more significant with increasing Laponite content, can be attributed to the impact of the clay on the fabric and grain-to-grain contacts. Evidence is provided that Laponite interferes with direct interaction between the sand grains, and the thickness of the clay layer present at the contacts appears to control the small-strain behaviour of the sand–Laponite mixtures. The formation of a gel-like pore fluid from the hydration of Laponite in the voids, and the degree to which it occupies the pore space, are responsible for the behaviour in the non-linear region.

Synthesis of Nanobentonite–Poly(vinyl alcohol)–Bacterial Cellulose Nanocomposite by Electrospinning for Wound Healing Applications

Polymer‐based composites are used for wound healing applications. This work aims to prepare an inorganic‐polymer nanocomposite based on bentonite, poly(vinyl alcohol), and bacterial cellulose by electrospinning for wound healing. The nanocomposite is synthesized using a solution intercalation technique, with 1–2 wt% nanobentonite concentration variation. The effects of commercial and laboratory‐synthesized nanobentonite as well as the extract of the green walnut shell (EGWS) are examined and characterized by different techniques. The addition of nanobentonite increases the average size of fibers and tensile strength up to 200 nm and more than 15 MPa, respectively, due to the presence of hydrogen bonding formed between the nanobentonite sheets and polymer matrix. By the addition of synthetic nanoclay and EGWS, moderate elongation and strength are achieved. The hydrophilicity shows a decreasing trend up to 2 wt% of commercial nanobentonite; however, the laboratory‐synthesized nanobentonite is not significantly effective. Effects of extracts on the viability of cultured human adipose tissue–derived mesenchymal stem cells (ADSCs) are quantitated, where the samples containing 1–2 wt% of commercial nanobentonite have less toxicity than others. Antibacterial activity is tested against both Escherichia coli and Staphylococcus aureus bacteria according to the agar diffusion test for 72 h, in which EGWS‐based mats exhibit strong antimicrobial activity.

Thermo-responsive hydrogels based on poly(N-isopropyl-acrylamide) and hyaluronic acid cross-linked with nanoclays

Semi-interpenetrating polymer networks (SIPN) based on thermoresponsive poly(N-isopropylacrylamide) (PNIPA) and water-soluble sodium salts of linear hyaluronic acid (Na-HA) were physically cross-linked with synthetic nanoclay (laponite XLG). PNIPA hydrogels with different cross-linking densities and Na-HA concentrations were synthesized by in situ free-radical redox polymerization. The structure and heterogeneity of the semi-IPN hydrogels were examined by SEM and XRD. The content of clay incorporated in the gel was determined by TGA. DSC measurements showed that volume phase transition temperature and its enthalpy varied with the clay and hyaluronic acid content. SIPN hydrogels containing negatively charged polyelectrolyte, Na- HA, exhibited higher Qe and faster deswelling rates than the corresponding PNIPA NC hydrogels. The presence of the anionic Na-HA polymer reduced the storage modulus, indicating a weakening of the hydrogel network structure, especially at lower clay contents. The nanocomposite hydrogels exhibited high tan ? values, which increased with increasing Na-HA content.

Osteogenic and angiogenic tissue formation in high fidelity nanocomposite Laponite-gelatin bioinks

Bioprinting of living cells is rapidly developing as an advanced biofabrication approach to engineer tissues. Bioinks can be extruded in three-dimensions (3D) to fabricate complex and hierarchical constructs for implantation. However, a lack of functionality can often be attributed to poor bioink properties. Indeed, advanced bioinks encapsulating living cells should: (i) present optimal rheological properties and retain 3D structure post fabrication, (ii) promote cell viability and support cell differentiation, and (iii) localise proteins of interest (e.g. vascular endothelial growth factor (VEGF)) to stimulate encapsulated cell activity and tissue ingrowth upon implantation. In this study, we present the results of the inclusion of a synthetic nanoclay, Laponite® (LPN) together with a gelatin methacryloyl (GelMA) bioink and the development of a functional cell-instructive bioink. A nanocomposite bioink displaying enhanced shape fidelity retention and interconnected porosity within extrusion-bioprinted fibres was observed. Human bone marrow stromal cell (HBMSC) viability within the nanocomposite showed no significant changes over 21 days of culture in LPN-GelMA (85.60 ± 10.27%), compared to a significant decrease in GelMA from 7 (95.88 ± 2.90%) to 21 days (55.54 ± 14.72%) (p < 0.01). HBMSCs were observed to proliferate in LPN-GelMA with a significant increase in cell number over 21 days (p < 0.0001) compared to GelMA alone. HBMSC-laden LPN-GelMA scaffolds supported osteogenic differentiation evidenced by mineralised nodule formation, including in the absence of the osteogenic drug dexamethasone. Ex vivo implantation in a chick chorioallantoic membrane model, demonstrated excellent integration of the bioink constructs in the vascular chick embryo after 7 days of incubation. VEGF-loaded LPN-GelMA constructs demonstrated significantly higher vessel penetration than GelMA-VEGF (p < 0.0001) scaffolds. Integration and vascularisation was directly related to increased drug absorption and retention by LPN-GelMA compared to LPN-free GelMA. In summary, a novel light-curable nanocomposite bioink for 3D skeletal regeneration supportive of cell growth and growth factor retention and delivery, evidenced by ex vivo vasculogenesis, was developed with potential application in hard and soft tissue reparation.

2D Nanoclay for Biomedical Applications: Regenerative Medicine, Therapeutic Delivery, and Additive Manufacturing.

Clay nanomaterials are an emerging class of 2D biomaterials of interest due to their atomically thin layered structure, charged characteristics, and well-defined composition. Synthetic nanoclays are plate-like polyions composed of simple or complex salts of silicic acids with a heterogeneous charge distribution and patchy interactions. Due to their biocompatible characteristics, unique shape, high surface-to-volume ratio, and charge, nanoclays are investigated for various biomedical applications. Here, a critical overview of the physical, chemical, and physiological interactions of nanoclay with biological moieties, including cells, proteins, and polymers, is provided. The state-of-the-art biomedical applications of 2D nanoclay in regenerative medicine, therapeutic delivery, and additive manufacturing are reviewed. In addition, recent developments that are shaping this emerging field are discussed and promising new research directions for 2D nanoclay-based biomaterials are identified.

Investigation into the Potential Migration of Nanoparticles from Laponite-Polymer Nanocomposites.

In this study, the migration potential of laponite, a small synthetic nanoclay, from nanocomposites into foods was investigated. First, a laponite/ethylene vinyl acetate (EVA) masterbatch was compounded several times and then extruded into thin low-density polyethylene (LDPE) based films. This way, intercalation and partial exfoliation of the smallest type of clay was achieved. Migration of laponite was investigated using Asymmetric Flow Field-Flow Fractionation (AF4) with Multi-Angle Laser Light Scattering (MALLS) detection. A surfactant solution in which laponite dispersion remained stable during migration test conditions was used as alternative food simulant. Sample films with different loadings of laponite were stored for 10 days at 60 °C. No migration of laponite was found at a limit of detection of 22 µg laponite per Kg food. It can be concluded that laponite (representing the worst case for any larger structured type of clay) does not migrate into food once it is incorporated into a polymer matrix.

Facile and On-Demand Cross-Linking of Nacre-Mimetic Nanocomposites Using Tailor-Made Polymers with Latent Reactivity.

The development of on-demand cross-linking strategies is a key aspect in promoting mechanical properties of high-performance bioinspired nanocomposites. Here, we embed styrene sulfonyl azide groups with latent chemical reactivity into water-soluble copolymers and assemble those with high-aspect-ratio synthetic nanoclays to generate well-defined layered polymer/nanoclay nacre-mimetics. A considerable stiffening and strengthening occurs upon activation of the covalent cross-linking using simple heating. Varying the amount of cross-linkable units allows molecular control of mechanical properties from ductile to stiff and strong. Moreover, the covalent cross-linking enhances the moisture stability of water-borne nacre-mimetics. The strategy is facile and versatile allowing for a transfer into applications.

3D freeform printing of silk fibroin

Freeform fabrication has emerged as a key direction in printing biologically-relevant materials and structures. With this emerging technology, complex structures with microscale resolution can be created in arbitrary geometries and without the limitations found in traditional bottom-up or top-down additive manufacturing methods. Recent advances in freeform printing have used the physical properties of microparticle-based granular gels as a medium for the submerged extrusion of bioinks. However, most of these techniques require post-processing or crosslinking for the removal of the printed structures (Miller et al., 2015; Jin et al., 2016) [1,2]. In this communication, we introduce a novel method for the one-step gelation of silk fibroin within a suspension of synthetic nanoclay (Laponite) and polyethylene glycol (PEG). Silk fibroin has been used as a biopolymer for bioprinting in several contexts, but chemical or enzymatic additives or bulking agents are needed to stabilize 3D structures. Our method requires no post-processing of printed structures and allows for in situ physical crosslinking of pure aqueous silk fibroin into arbitrary geometries produced through freeform 3D printing. Statement of Significance3D bioprinting has emerged as a technology that can produce biologically relevant structures in defined geometries with microscale resolution. Techniques for fabrication of free-standing structures by printing into granular gel media has been demonstrated previously, however, these methods require crosslinking agents and post-processing steps on printed structures. Our method utilizes one-step gelation of silk fibroin within a suspension of synthetic nanoclay (Laponite), with no need for additional crosslinking compounds or post processing of the material. This new method allows for in situ physical crosslinking of pure aqueous silk fibroin into defined geometries produced through freeform 3D printing.