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The present paper describes the preparation and characterization of novel microbeads from alginate filled with nanoclay such as halloysite nanotubes (HNTs). HNTs were used as support for the growth of layered double hydroxide (LDH) crystals producing a flower-like structure (HNT@LDH). Such nanofiller was loaded with grapefruit seed oil (GO), an active compound with antimicrobial activity, up to 50% wt. For comparison, the beads were also loaded with HNT and LDH separately, and filled with the same amount of GO. The characterization of the filler was performed using XRD and ATR spectroscopy. The beads were analyzed through XRD, TGA, ATR and SEM. The functional properties of the beads, as nanocarriers of the active compound, were investigated using UV-vis spectroscopy. The release kinetics were recorded and modelled as a function of the structural characteristics of the nanofiller. [ABSTRACT FROM AUTHOR]

In the framework of designing a novel bio-coating for the preservation of fresh fruits, this paper reports the design, preparation, and characterization of novel bio-nanocomposites based on pectin loaded with grapefruit seed oil (GO), a natural compound with antimicrobial properties, encapsulated into halloysite nanotubes (HNTs). The vacuum-based methodology was used for the encapsulation of the oil into the hollow area of the nanotubes, obtaining nano-hybrids (HNT-GO) with oil concentrations equal to 20, 30, and 50 wt%. Physical properties (thermal, mechanical, barrier, optical) were analyzed. Thermal properties were not significantly (p < 0.05) affected by the filler, while an improvement in mechanical performance (increase in elastic modulus, stress at breaking, and deformation at breaking up to 200%, 48%, and 39%, respectively, compared to pure pectin film) and barrier properties (increase in water permeability up to 480% with respect to pure pectin film) was observed. A slight increase in opacity was detected without significantly compromising the transparency of the films. The release of linoleic acid, the main component of GO, was followed for 21 days and was correlated with the amount of the hybrid filler, demonstrating the possibility of tailoring the release kinetic of active molecules. In order to evaluate the effectiveness of the prepared bio-composites as an active coating, fresh strawberries were coated and compared to uncoated fruit. Qualitative results showed that the fabricated novel bio-coating efficiently extended the preservation of fresh fruit. [ABSTRACT FROM AUTHOR]

This work concerns the fabrication of a green, novel, and sustainable system for the efficient removal of methylene blue from aqueous solutions. The proposed system is obtained by using sodium alginate/soybean extract blend reinforced with hemp hurd from agro‐waste resources and halloysite nanotubes (HNTs). The ionotropic gelation methodology, using calcium chloride as a crosslinking agent, was easily applied to obtain composite beads. The adsorption studies were carried out up to 24 h using methylene blue as model system. The effect of HNTs on adsorption capacity was investigated proving that an increase in inorganic filler determined an increase in adsorption capacity from 32 to 49 mg/g by adding 35% wt of HNTs. The experimental data were fitted through four different models, demonstrating that the adsorption phenomenon is described by second‐order process. Film diffusion and pore diffusion values were evaluated to better investigate the rate controlling mechanisms. Isotherm studies were then carried out to extrapolate thermodynamic parameters. Finally, a possible mechanism of adsorption was proposed on the basis of chemisorption mechanism. Here, we demonstrate that the proposed novel, inexpensive, and sustainable composite material obtained from agro‐waste resources has high efficiency in removing a cationic dye from wastewaters. [ABSTRACT FROM AUTHOR]

The formulation of cost-effectiveness sustainable materials is extensively growing and becoming an attractive approach for both industrial and academic fields. In this context, the bio-based aliphatic polyamide 11 (PA11) has acquired significant interest as environmentally friendly thermoplastic option. In addition, its formulation with selected natural antioxidant and/or reinforced compounds through green processing methods, might improve physical and mechanical properties without sacrificing the intrinsic bio-based nature of the matrix. In this work, we have investigated and compared the photo-oxidative degradation processes occurring on PA11 composites based on thymol and halloysite nanotubes prepared by using ball-milling method. In particular, halloysite nanotubes were used as green nano-container of a natural antioxidant molecule, and reinforced nano-filler as well. Molecular and structural information of photo-exposed samples were obtained by using size exclusion chromatography (SEC) and matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Thermal and mechanical properties were also tested as well as thymol release. Data collected confirmed that PA11 filled with HNTs-Thymol nano-hybrid showed superior durability performance if compared to both pure PA11 and PA11 blend realized by simply adding thymol and HNTs to polymer matrix. Furthermore, we found that HNTs and thymol combined in the nano-hydrid form exhibited an active and synergic role to achieve a major photo stabilization of PA11 biocomposite, without sacrificing its mechanical properties. [ABSTRACT FROM AUTHOR]

Multiscale polymeric composites combining a biodegradable matrix with low cost and biocompatible hybrid nanocarriers promise to supply a new generation of multipurpose devices for drug delivery. The aim of this work was to investigate the release mechanisms of sodium benzoate ( NaBz) from halloysite nanotubes ( HNTs) embedded in a biodegradable polymer matrix (poly(ϵ-caprolactone)). To that purpose, different amounts of NaBz molecules were successfully incorporated into HNTs using a simple environmentally friendly procedure. The resulting HNT-NaBz nano-hybrids were then incorporated into a poly(ϵ-caprolactone) matrix by high energy ball milling at ambient temperature and in dry conditions. Analysis of the resulting composites showed important effects of the HNT-NaBz nano-hybrids on the thermal and mechanical properties. Controlled drug release, followed by UV spectrophotometry, was also found to be dependent on the HNT-NaBz relative fractions. Experimental data were thus analyzed using a modified Gallagher − Corrigan model and correlated with the nano-hybrid morphologies. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This work aims to evaluate the possibility to introduce natural nano-containers for active molecules, such as halloysite nanotubes (HNTs), into an environmentally friendly material: natural zein. Composites were prepared in a wide range of HNTs composition (i.e. 1–10 wt%) and structural and physical properties were analyzed. HNTs were also filled with an active molecule commonly used as preservative in food packaging, such as potassium sorbate (KS), and the diffusion of such molecule was evaluated. The zein thermal degradation resulted significantly improved with the filler content. Mechanical properties showed a reinforcement of zein matrix. HNTs were filled with potassium sorbate and dispersed into the zein matrix. [ABSTRACT FROM AUTHOR]

This paper reports the preparation and characterization of green composites based on pectins and nano-hybrids composed of halloysite nanotubes (HNTs) loaded with rosemary essential oil. Different hybrid percentages were mixed into a pectin matrix, by ball milling in the presence of water. Cast films were obtained and analyzed. Structural organization and physical properties (thermal, mechanical, barrier to water vapor) were correlated to the nano-hybrid content. A preliminary study on the kinetics of release of the rosmarinic acid, chosen as a model molecule, was also performed. This work showed the potential of these systems in the active packaging field where controlled release of active species is required. [ABSTRACT FROM AUTHOR]

Composites based on Poly(ethylene terephthalate) (PET) and Halloysite nanotubes (HNTs) were prepared through high energy ball milling (HEBM) at ambient temperature and with no solvents. A wide range of HNTs loading was used (i.e. 1–7 wt%) and films produced. Morphological organization and physical (thermal, degradation, mechanical) properties were analyzed and correlated to HNTs content. HNTs were also filled with an antimicrobial model molecule, sodium benzoate, to test the effectiveness of such nano-containers as filler for polymers to be used in active packaging, enlightening very good perspectives in this field. [ABSTRACT FROM AUTHOR]

PLA nanocomposites at various Halloysite (HNT) loadings are produced by melt-mixing and then shaped as films. HNT is additionally surface-treated by silanization reaction with 3-(trimethoxysilyl)propyl methacrylate (TMSPM). The morphology, thermal and transport properties to water vapor (sorption, diffusion, permeability) of nanocomposite films are examined and compared to those of neat PLA. Due to the good nanofiller dispersion within PLA matrix, favorable interactions between components and other specific characteristic features (thermal, mechanical, optical), these nanocomposites are potentially interesting for use as environmental friendly packaging materials. [ABSTRACT FROM AUTHOR]

Novel biodegradable composites were prepared using PLA and a nano-hybrid composed of halloysite nanotubes (HNTs) filled with Lysozyme, as antimicrobial. The nano-hybrid was characterized from a structural point of view and the Lysozyme content evaluated by thermogravimetric analysis. Several composites were prepared using ball milling, in dry conditions at ambient temperature, varying the nano-hybrid loading (i.e. 3, 5, 10 wt%). The structural organization and physical properties (thermal, mechanical and barrier to water vapor) ware analyzed and correlated to the nano-hybrid content. Controlled Lysozyme release into saline solution was followed using UV spectrophotometry. The release kinetics was found to be dependent on HNTs-Lysozyme relative fractions. The experimental results were analyzed by a modified Gallagher-Corrigan model. [ABSTRACT FROM AUTHOR]

Nowaday the use of essential oils, having antimicrobial activity, is quite limited in the field of active packaging for the difficulty to retain the active compound for a long time into the material. The paper reports the design and fabrication of a nano-carrier able to incorporate and protect an essential oil (i.e. citral) for targeted applications. The hybrid filler was produced by growing layered double hydroxide (LDH) nanocrystals as plates on halloysite nanotubes (Hal) (Hal@LDH). Such hybrid filler was used as a carrier of citral as an antimicrobial essential oil. The active filler was incorporated into the starch matrix at 5, 10, and 15 wt% and films were produced. The structural organization of the filler was conducted by using Scansion Electron Microscopy (SEM), Thermogravimetric Analysis (TGA) and X-ray Diffraction (XRD) analysis. The obtained bio-composite films were structurally analyzed through XRD and SEM with EDX analysis. The physical performances were evaluated through the analysis of mechanical properties, contact angle, radical scavenging activity and release kinetics of citral, as a function of filler loading. To assess the possibility of using such composites for food packaging applications, tests were carried out on different strains such as Escherichia coli, Listeria monocytogenes, and Salmonella bongori. • A hybrid carrier loaded with citral was prepared to produce starch based active films. • The used methodology to produce the hybrid carrier was ball milling at ambient temperature. • Analysis of structure and physical properties of the composites was carrier out. • Films showed antimicrobial activity against pathogens active in food spoilage. [ABSTRACT FROM AUTHOR]

This research aims for designing and fabricating green and sustainable systems for an efficient removal of methylene blue from aqueous solutions. The hybrid beads, obtained by using ionotropic gelation technique and calcium chloride as cross-linking agent, are composed of sodium alginate matrix, hemp hurd as agro-waste resource and halloysite nanoclay (HNTs). The produced composite beads were characterized morphologically by using SEM and EDX techniques. The batch adsorption studies were performed up to 24 h using methylene blue (MB) as model hazardous dye in order to investigate the effect of HNTs content (0–35% wt) and pH (2, 7 and 12) on the adsorption capacity. In neutral conditions, a maximum adsorption capacity of 32 mg/g was obtained for sample with 0% of HNTs while it increases up to 41, 43 and 50 mg/g for 5%, 20% and 35%wt, respectively. Moreover, swelling/deswelling behavior and point of zero charge (PZC) analysis were even investigated since they are known to affect the adsorption process. A slight increase in PZC can be observed by adding clay nanotubes from 7.42 (0% wt HNTs) up to 7.98 (35% wt HNTs). The experimental data were fitted through first order model, pseudo-second order model and intraparticle diffusion model, demonstrating that the adsorption phenomenon is well described by second order process as well as that the process is mainly characterized by boundary diffusion and intraparticle diffusion. Finally, diffusion of dye was evaluated as function of HNTs content and H+ concentration appearing to decrease from pH= 2 up to pH= 7 and then to increase in alkaline medium (pH=12). Diffusion coefficient and recovery % trends were modeled through design of experiment methodology. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Smart biodegradable packaging was designed using red onion extract as a pH sensor. • Salicylate-loaded halloysite-layered double hydroxide filler provides active function. • The filler stabilizes the extract enhancing its reliability in reporting pH changes. • Biodegradability is ensured by a potato starch matrix. • Spectroscopic, mechanical and antimicrobial properties of the films were examined. A multifunctional and sustainable packaging was developed based on a potato starch matrix loaded with a cyanidin-rich freeze-dried onion extract (OE) anchored on a halloysite-layered double hydroxide filler. Due to a distinct colour change that varies according to the environmental pH, the extract acts as a visual sensor of food quality and it is stabilised by the filler which can be loaded with antibacterial agents, providing the active component of the film. In this work, the physical, mechanical and antimicrobial properties of films prepared with only extract or containing both extract and filler are examined and compared. In addition, the real-time sensing capability of the films was tested by monitoring their colour changes when applied in meat and milk storage. [ABSTRACT FROM AUTHOR]

Solvent-free syntheses provide an alternative path that reduces the use of hazardous substances. In this work, a sustainable synthesis of nanometric layered double hydroxide particles grafted over halloysite nanotubes (HNT@LDH) is reported using a mechanochemical technique. Samples loaded with different LDH percentage (100%, 50%, 40%, 30%, 20%, 10% with respect to the HNT content) were prepared and characterized. Spectroscopic and morphological characterizations allowed to select the sample with 20% by weight of LDH as the best composite (HNT@LDH20), wherein no LDH phase segregation was observed and the nanosheets were homogeneously grafted throughout the surface of the halloysite nanotubes. The combination of cationic and anionic clays in one filler enables the preparation of a composite which can be easily dispersed in a polymer and release active molecules. To this end, salicylate ions were incorporated into the layered double hydroxide nanoflakes of HNT@LDH20 and three intercalation strategies, comprising both solvent-free and traditional intercalating routes, were tested. Results of salicylate release tests indicate that the intercalating route used affects the amount of species hosted, the strength of the salicylate-LDH interactions and the drug release time, thus offering the possibility of selecting the most suitable method of drug incorporation to tune the salicylate content depending on a specific aim. [Display omitted] [ABSTRACT FROM AUTHOR]