Unveiling the MIL-53(Al) MOF: Tuning Photoluminescence and Structural Properties via Volatile Organic Compounds Interactions

MIL-53(Al) is a metal-organic framework (MOF) with unique properties, including structural flexibility, thermal stability, and luminescence. Its ability to adsorb volatile organic compounds (VOCs) and water vapor makes it a promising platform for sensing applications. This study investigated the adsorption mechanism of MIL-53(Al) with different VOCs, including ketones, alcohols, aromatics, and water molecules, focusing on structural transformations due to pore size variation and photoluminescence properties. The reported results assess MIL-53(Al) selectivity towards different VOCs and provide insights into their fundamental properties and potential applications in sensing.

From micro to macro: Physical-chemical characterization of wheat starch-based films modified with PEG200, sodium citrate, or citric acid

Needing to extend the shelf-life of packaged food and the evolving consumer demands led researchers to seek innovative, eco-friendly, and biocompatible packaging solutions. Starch is among the most promising natural and renewable alternatives to non-degradable plastics. Here, we deeply study the structural features of starch films modified by adding citric acid (CA) or sodium citrate (SC) as a cross-linker and polyethylene glycol 200 (PEG200) as a plasticizer and obtained through solvent casting. The substances' influence on starch films was evaluated through Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) and Solid-state Nuclear Magnetic Resonance (ss-NMR) spectroscopies. Films' macroscopic properties, such as swelling index, solubility, thermo-mechanical features, and moisture absorption, were also assessed to foresee potential applications. Proper amounts of CA, CS, and PEG200 improve film properties and inhibit starch chains' retrogradation and recrystallization. Besides, the chemical neighbourhood of nuclei observed through ss-NMR significantly changed alongside the polymer chains' mobility. The latter result indicates a different polymer chain structural organization that could justify the film's higher resistance to thermal degradation and elongation at the break. This methodological approach is effective in predicting the macroscopic behaviour of a polymeric material and could be helpful for the application of such products in food preservation.

Upcycling of Poly(lactic acid) Waste: A Valuable Strategy to Obtain Ionic Liquids

With the aim to investigate new strategies for upcycling of plastic waste, we performed aminolysis of poly(lactic acid) (PLA), using N,N-dimethylethylenediamine (DMEDA), N,N-dimethylpropylenediamine (DMPDA), and 3-aminopropylimidazole (API) as nucleophiles. The N-substituted lactamides obtained were alkylated by using alkyl halides differing in alkyl chain length, obtaining organic salts that in most cases behaved as ionic liquids (ILs). Both aminolysis of PLA and alkylation of amides were carried out taking into consideration the basic principles of the holistic approach to green chemistry, applied at a laboratory scale, and carefully selecting the nature of the reaction solvent, temperature range, and amount of reagents. Organic salts obtained from the alkylation of N-substituted lactamides were investigated to determine their glass or solid-liquid transitions and their thermal stability. Furthermore, cytotoxicity toward normal lung fibroblasts was also assessed. Data collected show that the proposed strategy represents a valuable protocol to upcycle plastic waste, using it as starting material to obtain alternative solvents of potential industrial relevance.

New Biocide Based on Tributyltin(IV) Ferulate-Loaded Halloysite Nanotubes for Preserving Historical Paper Artworks

Combining biologically active compounds with nanocarriers is an emerging and promising strategy for enhancing the activities of molecules while reducing their levels of toxicity. Green nanomaterials have recently gained momentum in developing protocols for treating and preserving artifacts. In this study, we designed a functional biohybrid material by incorporating tributyltin(IV) ferulate (TBT-F) into halloysite nanotubes (HNTs), generating a new formulation called HNT/TBT-F. The primary objective was to develop a formulation with robust antimicrobial properties and reinforcing features for treating paper with artistic and historical value. To characterize HNT/TBT-F, assess the HNT's loading capacity, and investigate the TBT-F release kinetics from the nanotubes, various analytical techniques, including UV-Vis and infrared spectroscopies, thermogravimetry, and microscopy analysis, were employed. Furthermore, we evaluated the antimicrobial potential of TBT-F and HNT/TBT-F against Kocuria rhizophila, a bacterial strain known for its opportunistic behavior and a cause of artifact biodeterioration. HNT/TBT-F exhibited a significantly stronger bactericidal effect than TBT-F alone against K. rhizophila cells growing planktonically or those forming a biofilm. This enhanced performance could relate to the confinement of TBT-F within the nanotubes, which likely improved its physical-chemical stability and increased the local concentration of TBT-F upon contact with the bacterial cells. Additionally, we evaluated the mechanical properties of a paper treated with HNT/TBT-F, assessing any potential alterations in its color. The findings of this study highlight the favorable attributes of the HNT/TBT-F formulation and its potential for developing protocols aimed at consolidating and preserving culturally significant paper objects.

Application of the Ugi reaction for preparation of submicron capsules based on sugar beet pectin

The Ugi four-component condensation in diluted liposomal suspensions was used to prepare pectin-based submicron capsules. A set of isocyanides and aldehydes was used to optimize the synthesis of capsule shells. Modified sugar beet pectin was selected as a natural polymer with pronounced surface activity to create a capsule shell. At first, liposomal composition was optimized in order to select suitable conditions for capsule formation. Then, the wide set of capsules constructed on modified sugar beet pectin scaffold has been synthesized. The choice was determined by level of substitution degree and possible chemical diversity of the modified surface. Detailed characterization of products has been performed for polysaccharide particles with liposomal core prepared with various processing parameters (concentration, cross-linking components, the density of linkage). The chemical structure, average size, polydispersity index, morphology, stability, and cytotoxicity of obtained particles have been investigated in dependence on the shell content. The obtained submicrometer cross-linked capsules (220-240 nm) with controlled colloidal properties showed high stability and low toxicity. Thus, the proposed carriers have a great potential as sustained drug delivery systems for different administration routes.

Nanocomposites based on halloysite nanotubes and sulphated galactan from red seaweed Gloiopeltis: Properties and delivery capacity of sodium diclofenac

We developed novel composite films based on biocompatible components, such as halloysite clay nanotubes and sulphated galactan (Funori) from red seaweed Gloiopeltis. The filling of the nanotubes within the sulphated galactan matrix was carried out by a green protocol (aqueous casting method) assuring that Funori/halloysite nanocomposites can be totally considered as sustainable materials. The amount of halloysite in the composites was systematically changed to explore the effects of the nanofiller concentration on the mesoscopic properties of the films. We observed that the halloysite content significantly affects the initial water contact angle and the light attenuation coefficient of the Funori based films. These results were interpreted according to SEM images, which showed that the surface morphologies of the nanocomposites depend on the halloysite amounts filled within the polymeric matrix. The mechanical characterization of the nanocomposites was conducted by tensile experiments performed using a linear stress ramp. Moreover, tensile tests were conducted in oscillatory regime at variable temperature to investigate the viscoelastic properties of the nanocomposites. Finally, we filled the biopolymeric matrix with halloysite nanotubes containing sodium diclofenac. The drug release kinetics from the nanocomposites at variable halloysite contents were studied to evaluate their suitability as oral dissolving films for pharmaceutical applications.

Phenolic Compounds from Sour Cherry Pomace: Microencapsulation, in Vitro Digestion, and Cell Growth Activities

The objective of this work was the valorisation of sour cherry (Prunus cerasus L.) pomace as a source of biologically active compounds. To formulate microcapsules, polyphenolic compounds were extracted and encapsulated with maltodextrin as wall material, by freeze-drying. An in vitro digestion study was carried out on obtained encapsulates but also on sour cherry pomace extract and sour cherry pomace freeze-dried powder. The results indicated that encapsulation, as well as freeze-drying, provided a good protective effect on bioactive compounds during digestion. Furthermore, the potential antiproliferative and cytotoxic activities of encapsulates and sour cherry pomace extract were evaluated using breast adenocarcinoma MCF7 cell lines, colon adenocarcinoma HT-29 cell lines, and noncancer cell line. Encapsulates and sour cherry pomace extract showed variable anti-proliferative activity towards all cell lines. Obtained results showed that encapsulation of sour cherry pomace could be useful for improving the stability of polyphenolic compounds in the gastrointestinal tract. The results highlight the bioactive potential of sour cherry pomace as a nutraceutical resource and the protective effects of microencapsulation on the digestion of bioactive compounds.

Thermoresponsive behavior of cyclodextrin inclusion complexes with weakly anionic alkyl ethoxy carboxylates

This study investigates the temperature responsive behavior of inclusion complexes formed by weakly anionic alkyl ethoxy carboxylates and α (αCD) and β-cyclodextrins (βCD). Small-angle neutron scattering (SANS) was performed to probe the structural behaviour at the 1-100 nanometer scale of the hierarchical assemblies at different temperatures. The phase transitions and thermodynamics were systematically monitored as a function of the degree of ionization of the surfactant by differential scanning calorimetry (DSC). Herein, we investigate the effect of the surfactant degree of ionization on the thermoresponsive properties of the inclusion complex supramolecular assemblies. Inclusion complexes formed with the ionized surfactant spontaneously assemble into multilayered structures, which soften with increasing temperature. We also found that the presence of charges is not only required to impart order to the supramolecular assemblies, but also induced in-plane crystallization of the inclusion complexes. Finally, the use of a weakly anionic surfactant allows us to probe the interplay between the charge density and temperature on the assembly of surfactant-cyclodextrin inclusion complexes. This study helps to improve the design of multi-responsive supramolecular systems based on cyclodextrins.

Keratin/alginate hybrid hydrogels filled with halloysite clay nanotubes for protective treatment of human hair

Keratin/alginate hydrogels filled with halloysite nanotubes (HNTs) have been tested for the protective coating of human hair. Preliminary studies have been conducted on the aqueous colloidal systems and the corresponding hydrogels obtained by using Ca²⁺ ions as crosslinkers. Firstly, we have investigated the colloidal properties of keratin/alginate/HNTs dispersions to explore the specific interactions occurring between the biomacromolecules and the nanotubes. Then, the rheological properties of the hydrogels have been studied highlighting that the keratin/alginate interactions and the subsequent addition of HNTs facilitate the biopolymer crosslinking. Finally, human hair samples have been treated with the hydrogel systems by the dipping procedure. The protection efficiency of the hydrogels has been evaluated by studying the tensile properties of hair fibers exposed to UV irradiation. In conclusion, keratin/alginate hydrogel filled with halloysite represents a promising formulation for hair protective treatments due to the peculiar structural and rheological characteristics.

Hierarchical assembly of pH-responsive surfactant-cyclodextrin complexes

In this work, the inclusion complexes of alkyl ethoxy carboxylates with α-cyclodextrin (αCD) and β-cyclodextrin (βCD) were investigated. The thermodynamics of the complexation process was probed by isothermal titration calorimetry (ITC) and volumetry as a function of the degree of ionization of the surfactant. The complexation process was shown to be an enthalpically driven pH-independent process. For both types of cyclodextrins, the complexes were found to spontaneously self-assemble into highly-ordered supramolecular aggregates probed by small-angle neutron scattering and electron and optical microscopy. Herein, we report the formation of thin platelets for nonionized surfactant systems and equally spaced multilayered hollow cylinders for ionized systems in a hierarchical self-assembly process. In addition, the analysis allowed unveiling the effect of the number of ethylene oxides in the surfactants and the CD cavity size on the morphology of the aggregates. Finally, this study also highlights the importance of examining the tuning parameters' influence on the short and long-range interactions involved in the control of the assembly process.

Chitosan Functionalized with Carboxyl Groups as a Recyclable Biomaterial for the Adsorption of Cu (II) and Zn (II) Ions in Aqueous Media

The modification of chitosan represents a challenging task in obtaining biopolymeric materials with enhanced removal capacity for heavy metals. In the present work, the adsorption characteristics of chitosan modified with carboxyl groups (CTS-CAA) towards copper (II) and zinc (II) ions have been tested. The efficacy of the synthesis of CTS-CAA has been evaluated by studying various properties of the modified chitosan. Specifically, the functionalized chitosan has been characterized by using several techniques, including thermal analyses (differential scanning calorimetry and thermogravimetry), spectroscopies (FT-IR, XRD), elemental analysis, and scanning electron microscopy. The kinetics and the adsorption isotherms of CTS-CAA towards both Cu (II) and Zn (II) have been determined in the aqueous solvent under variable pH. The obtained results have been analyzed by using different adsorption models. In addition, the experiments have been conducted at variable temperatures to explore the thermodynamics of the adsorption process. The regeneration of CTS-CAA has been investigated by studying the desorption process using different eluents. This paper reports an efficient protocol to synthesize chitosan-based material perspective as regenerative adsorbents for heavy metals.

Prodrug based on halloysite delivery systems to improve the antitumor ability of methotrexate in leukemia cell lines

The prodrug approach, as well as the development of specific systems able to deliver a chemotherapeutic agent in the target site, decreasing the side effects often associated with its administration, are still a challenging. In this context, both methotrexate drug molecules (MTX) and biotin ligand moieties, whose receptors are overexpressed on the surface of several cancer cells, were loaded on halloysite nanotubes (HNTs) to develop nanomaterial based on multifunctional and "smart" delivery systems. To highlight the crucial role played by biotin, carrier systems based on HNTs and MTX were also synthetized. In detail, several approaches were envisaged: i) a supramolecular interaction between the clay and the drug; ii) a covalent grafting of the drug onto the HNTs external surface and, iii) a combination of both approaches. The nanomaterials obtained were characterized by thermogravimetric analysis, FT-IR, and UV-vis spectroscopies, DLS and ζ-potential measurements and the morphologies were imaged by HAADF/STEM investigations. Kinetic release experiments at different pH conditions were also performed. Finally, as a proof-of-concept application of our pro-drug delivery systems based on HNTs in cancer therapy, the cytotoxic effects were evaluated on acute myeloid leukemia cell lines, HL60 and its multidrug resistance variant, HL60R. The obtained results showed that both the MTX prodrug system and the biotinylated ones played a crucial role in the biological activity and, they are promising agents for the cancer treatments.

Halloysite nanotubes as nanoreactors for heterogeneous micellar catalysis

HYPOTHESIS

Electrostatic attractions between the anionic head group of sodium alkylsulphates and the positively charged inner surface of halloysite nanotubes (HNTs) drive to the formation of tubular inorganic micelles, which might be employed as nanoreactors for the confinement of non polar compounds in aqueous media. On this basis, sodium alkylsulphates/halloysite hybrids could be efficient nanocatalysts for organic reactions occurring in water.

EXPERIMENTS

Sodium decylsulphate (NaDeS) and sodium dodecylsulphate (NaDS) were selected for the functionalization of the halloysite cavity. The composition, the structure and the surface charge properties of the hybrid nanotubes were determined. The actual formation of inorganic micelles was explored by studying the microviscosity and polarity characteristics of the surfactant modified nanotubes through fluorescence spectroscopy experiments using DiPyme as probe. The performances of the sodium alkylsulphates/halloysite composites as micellar catalysts for the Belousov-Zhabotinsky (BZ) reaction were investigated.

FINDINGS

The halloysite functionalization with sodium alkylsulphates generated the formation of hydrophobic microdomains with an enhanced microviscosity. Compared to the surfactant conventional micelles, the functionalized nanotubes induced larger enhancements on the rate constant of the BZ reaction. This is the first report on the surfactant/halloysite hybrids showing their efficiencies as reusable nanocatalysts, which are dependent on their peculiar microviscosity and polarity properties.

Inclusion complexes of triblock L35 copolymer and hydroxyl propyl cyclodextrins: a physico-chemical study

Polypseudorotaxanes based on triblock L35 copolymer and hydroxyl propyl-modified cyclodextrins (HP-α-CD and HP-β-CD) have been characterized. Their physico-chemical properties have been correlated to the threading process.

Nonporous, Strong, Stretchable, and Transparent Electrospun Aromatic Polyurea Nanocomposites as Potential Anticorrosion Coating Films

This study, for the first time, focused on the fabrication of nonporous polyurea thin films (~200 microns) using the electrospinning method as a novel approach for coating applications. Multi-walled carbon nanotubes (MWCNTs) and hydrophilic-fumed nanosilica (HFNS) were added separately into electrospun polyurea films as nano-reinforcing fillers for the enhancement of properties. Neat polyurea films demonstrated a tensile strength of 14 MPa with an elongation of 360%. At a loading of 0.2% of MWCNTs, the highest tensile strength of 21 MPa and elongation of 402% were obtained, while the water contact angle remained almost unchanged (89°). Surface morphology analysis indicated that the production of polyurea fibers during electrospinning bonded together upon curing, leading to a nonporous film. Neat polyurea exhibited high thermal resistance with a degradation temperature of 380 °C. Upon reinforcement with 0.2% of MWCNTs and 0.4% of HFNS, it increased by ~7 °C. The storage modulus increased by 42 MPa with the addition of 0.2% of MWCNTs, implying a superior viscoelasticity of polyurea nanocomposite films. The results were benchmarked with anti-corrosive polymer coatings from the literature, revealing that the production of nonporous polyurea coatings with robust strength, elasticity, and thermal properties was achieved. Electrospun polyurea coatings are promising candidates as flexible anti-corrosive coatings for heat exchanges and electrical wires.

Conversion of Organic Dyes into Pigments: Extraction of Flavonoids from Blackberries (Rubus ulmifolius) and Stabilization

The blackberry’s color is composed mainly of natural dyes called anthocyanins. Their color is red–purple, and they can be used as a natural colorant. Anthocyanins are flavonoids, which are products of plants, and their colors range from orange and red to various shades of blue, purple and green, according to pH. In this study, the chemical composition of an extract obtained from blackberries was defined by LC-ESI/LTQOrbitrap/MS in positive and negative ionization mode. Furthermore, we investigated the adsorption process of blackberry extract using several inorganic fillers, such as metakaolin, silica, Lipari pumice, white pozzolan and alumina. The pigments exhibit different colors as a function of their interactions with the fillers. The analysis of the absorption data allowed the estimation of the maximum adsorbing capacity of each individual filler tested. Through thermogravimetric measurements (TGA), the thermal stability and the real adsorption of the organic extract were determined.

Effect of Polymer Length on the Adsorption onto Aluminogermanate Imogolite Nanotubes

This study evidences the adsorption of model nonionic polymers onto aluminogermanate imogolite nanotubes, attractive porous nanofillers with potential molecular loading and release applications. We resolve the underlying mechanisms between nanotubes and polyethylene glycols with different molecular weights by means of nanoisothermal titration calorimetry. The analysis of the results provides a direct thermodynamic characterization, allowing us to propose a detailed description of the energetics involved in the formation of polymer/imogolite complexes. The affinity toward the nanotube surface is enthalpy-driven and strongly depends on the polymer chain length, which significantly affects the polymer configuration and the flow properties of the resulting complexes, probed by small-angle neutron scattering and rheology, respectively. These findings open new avenues for the rational design of these hybrid mixtures for advanced applications.

Chitosan-based smart hybrid materials: a physico-chemical perspective

Chitosan is one of the most studied cationic polysaccharides. Due to its unique characteristics of being water soluble, biocompatible, biodegradable, and non-toxic, this macromolecule is highly attractive for a broad range of applications. In addition, its complex behavior and the number of ways it interacts with different components in a system result in an astonishing variety of chitosan-based materials. Herein, we present recent advances in the field of chitosan-based materials from a physico-chemical perspective, with focus on aqueous mixtures with oppositely charged colloids, chitosan-based thin films, and nanocomposite systems. In this review, we focus our attention on the physico-chemical properties of chitosan-based materials, including solubility, mechanical resistance, barrier properties, and thermal behaviour, and provide a link to the chemical peculiarities of chitosan, such as its intrinsic low solubility, high rigidity, large charge separation, and strong tendency to form intra- and inter-molecular hydrogen bonds.

Cyclodextrin/surfactant inclusion complexes: An integrated view of their thermodynamic and structural properties

Cyclodextrins (CDs) play an important role in self-assembly systems of amphiphiles. The structure of CDs provides distinguished physicochemical properties, including the ability to form host-guest complexes. The complexation affects the properties of guest molecules and can produce supramolecular aggregates with desirable characteristics for fundamental and practical applications. Surfactants are particularly attractive host molecules due to their wide variety, availability, responsiveness to different stimuli, and high relevance in different fields, e.g. medical, cosmetic, pharmaceutical, and food industries. The tendency of organization in higher-order supramolecular aggregates arises the interest in applying such versatile complexes in the development of novel materials. In this review, we provide a comprehensive overview of the thermodynamics aspects of surfactants and CDs inclusion complexes formation in aqueous environment, emphasizing the assessment of the interactions, thermodynamic driving forces, and structural aspects. Also, the most common analytical techniques used to gather deep insight into the aspects of CDs complexes are discussed and the perspectives for the surfactant-cyclodextrin complexes are pointed out.

Pickering Emulsions Based on Wax and Halloysite Nanotubes: An Ecofriendly Protocol for the Treatment of Archeological Woods

A novel green protocol for the consolidation and protection of waterlogged archeological woods with wax microparticles has been designed. First, we focused on the development of halloysite nanotubes (HNTs) based Pickering emulsions using wax as the inner phase of the oil-in-water droplets. The optimization of the preparation strategy was supported by both optical microscopy and scanning electron microscopy, which allowed us to show the morphological features of the prepared hybrid systems and their structural properties, i.e., the distribution of the clay at the interface. Also, the dependence of the overall dimensions of the prepared systems on the halloysite content was demonstrated. Microdifferential scanning calorimetry (μ-DSC) was conducted in order to assess whether the thermal properties of the wax are affected after its interaction with HNTs. Then, the Pickering emulsions were employed for the treatment of waterlogged wooden samples. Compared to the archeological woods treated with pure wax, the addition of nanotubes induced a remarkable improvement in the mechanical performance in terms of stiffness and flexural strength. The proposed protocol is environmentally friendly since water is the only solvent used throughout the entire procedure, even if wax is vehiculated into the pores at room temperature. As a consequence, the design of wax/halloysite Pickering emulsions represents a promising strategy for the preservation of wooden artworks, and it has a great potential to be scaled up, thus becoming also exploitable for the treatments of shipwrecks of large size.

Halloysite Nanotubes Coated by Chitosan for the Controlled Release of Khellin

In this work, we have developed a novel strategy to prepare hybrid nanostructures with controlled release properties towards khellin by exploiting the electrostatic interactions between chitosan and halloysite nanotubes (HNT). Firstly, khellin was loaded into the HNT lumen by the vacuum-assisted procedure. The drug confinement within the halloysite cavity has been proved by water contact angle experiments on the HNT/khellin tablets. Therefore, the loaded nanotubes were coated with chitosan as a consequence of the attractions between the cationic biopolymer and the halloysite outer surface, which is negatively charged in a wide pH range. The effect of the ionic strength of the aqueous medium on the coating efficiency of the clay nanotubes was investigated. The surface charge properties of HNT/khellin and chitosan/HNT/khellin nanomaterials were determined by ζ potential experiments, while their morphology was explored through Scanning Electron Microscopy (SEM). Water contact angle experiments were conducted to explore the influence of the chitosan coating on the hydrophilic/hydrophobic character of halloysite external surface. Thermogravimetry (TG) experiments were conducted to study the thermal behavior of the composite nanomaterials. The amounts of loaded khellin and coated chitosan in the hybrid nanostructures were estimated by a quantitative analysis of the TG curves. The release kinetics of khellin were studied in aqueous solvents at different pH conditions (acidic, neutral and basic) and the obtained data were analyzed by the Korsmeyer-Peppas model. The release properties were interpreted on the basis of the TG and ζ potential results. In conclusion, this study demonstrates that halloysite nanotubes wrapped by chitosan layers can be effective as drug delivery systems.

On the effect of the nature of counterions on the self-assembly of polyoxyethylene alkyl ether carboxylic acids

In this contribution, we investigate the effect of the type of counterion on the properties of dilute solutions of polyoxyethylene alkyl ether carboxylic acids. Two different surfactants, presenting an oleic acid alkyl chain and on-average five and nine ethylene oxide units, and terminated by a weakly anionic carboxymethyl group were studied. The surfactants were gradually ionized with sodium hydroxide, arginine, and choline hydroxide. The solutions properties were probed by light scattering, electrophoretic mobility, density and sound velocity measurements, as well as by small-angle neutron scattering. To our initial surprise, no specific effect arising from the nature of the counterion could be determined. We ascribe this phenomenon to the fact that the presence of the ethylene oxide units markedly dilutes the surfactant head group charge density, reducing counterion condensation and subsequent counterion specific effects.

Halloysite/Keratin Nanocomposite for Human Hair Photoprotection Coating

We propose a novel keratin treatment of human hair by its aqueous mixtures with natural halloysite clay nanotubes. The loaded clay nanotubes together with free keratin produce micrometer-thick protective coating on hair. First, colloidal and structural properties of halloysite/keratin dispersions and the nanotube loaded with this protein were investigated. Above the keratin isoelectric point (pH = 4), the protein adsorption into the positive halloysite lumen is favored because of the electrostatic attractions. The ζ-potential magnitude of these core-shell particles increased from -35 (in pristine form) to -43 mV allowing for an enhanced colloidal stability (15 h at pH = 6). This keratin-clay tubule nanocomposite was used for the immersion treatment of hair. Three-dimensional-measuring laser scanning microscopy demonstrated that 50-60% of the hair surface coverage can be achieved with 1 wt % suspension application. Hair samples have been exposed to UV irradiation for times up to 72 h to explore the protection capacity of this coating by monitoring the cysteine oxidation products. The nanocomposites of halloysite and keratin prevent the deterioration of human hair as evident by significant inhibition of cysteic acid. The successful hair structure protection was also visually confirmed by atomic force microscopy and dark-field hyperspectral microscopy. The proposed formulation represents a promising strategy for a sustainable medical coating on the hair, which remediates UV irradiation stress.

Selective Cytotoxic Activity of Prodigiosin@halloysite Nanoformulation

Prodigiosin, a bioactive secondary metabolite produced by Serratia marcescens, is an effective proapoptotic agent against various cancer cell lines, with little or no toxicity toward normal cells. The hydrophobicity of prodigiosin limits its use for medical and biotechnological applications, these limitations, however, can be overcome by using nanoscale drug carriers, resulting in promising formulations for target delivery systems with great potential for anticancer therapy. Here we report on prodigiosin-loaded halloysite-based nanoformulation and its effects on viability of malignant and non-malignant cells. We have found that prodigiosin-loaded halloysite nanotubes inhibit human epithelial colorectal adenocarcinoma (Caco-2) and human colon carcinoma (HCT116) cells proliferative activity. After treatment of Caco-2 cells with prodigiosin-loaded halloysite nanotubes, we have observed a disorganization of the F-actin structure. Comparison of this effects on malignant (Caco-2, HCT116) and non-malignant (MSC, HSF) cells suggests the selective cytotoxic and genotoxic activity of prodigiosin-HNTs nanoformulation.

Effect of the supramolecular interactions on the nanostructure of halloysite/biopolymer hybrids: a comprehensive study by SANS, fluorescence correlation spectroscopy and electric birefringence

The structural properties of halloysite/biopolymer aqueous mixtures were firstly investigated by means of combining different techniques, including small-angle neutron scattering (SANS), electric birefringence (EBR) and fluorescence correlation spectroscopy (FCS). Among the biopolymers, non-ionic hydroxypropylcellulose and polyelectrolytes (anionic alginate and cationic chitosan) were selected. On this basis, the specific supramolecular interactions were correlated to the structural behavior of the halloysite/biopolymer mixtures. SANS data were analyzed in order to investigate the influence of the biopolymer adsorption on the halloysite gyration radius. In addition, a morphological description of the biopolymer-coated halloysite nanotubes (HNTs) was obtained by the simulation of SANS curves. EBR experiments evidenced that the orientation dynamics of the nanotubes in the electric field is influenced by the specific interactions with the polymers. Namely, both variations of the polymer charge and/or wrapping mechanisms strongly affected the HNT alignment process and, consequently, the rotational mobility of the nanotubes. FCS measurements with fluorescently labeled biopolymers allowed us to study the aqueous dynamic behavior of ionic biopolymers after their adsorption onto the HNT surfaces. The combination of EBR and FCS results revealed that the adsorption process reduces the mobility in water of both components. These effects are strongly enhanced by HNT/polyelectrolyte electrostatic interactions and wrapping processes occurring in the halloysite/chitosan mixture. The attained findings can be useful for designing halloysite/polymer hybrids with controlled structural properties.

Halloysite Nanotubes: Interfacial Properties and Applications in Cultural Heritage

The peculiar surfaces of halloysite nanotubes and their biocompatibility are attracting the interest of researchers based on the wide range of attainable applications. The large aspect ratio of this nanotubular material ensures promising properties as a reinforcing agent in polymeric matrixes, such as cellulose and its derivatives, that entail strengthening due to, for instance, aging-induced degradation. The halloysite cavity has a suitable size for hosting a large variety of active species such as deacidifying (calcium hydroxide) and flame retardant agents (fluorinated surfactants) for a controlled and sustained release relevant to the conservation of cultural heritage. Additionally, anionic surfactants can be selectively adsorbed at the inner surface generating inorganic micelles able to solubilize hydrophobic species in a controlled cleaning protocol. We briefly discuss how the natural halloysite nanotubes can be supportive in various conservation processes of cultural heritage and present an outlook for future perspectives.

Improvement of oxidation resistance of polymer-based nanocomposites through sonication of carbonaceous nanoparticles

The work aim is focused on two different aspects: first, the investigation of the effect of extended ultra-sound-assisted treatment (us) of carbonaceous nanoparticles, such as carbon nanotubes (CNTs) and carbon black (CB), on their radical scavenging activity, and second, the investigation of the oxidative resistance of polymer-based nanocomposites, containing us-treated CNTs and CB. Particularly, the CNTs and CB have been subjected to us sonication for different time intervals and the performed analysis reveals that both kinds of nanoparticles show decreased average hydrodynamic diameters and large content of surface defects. Really, the increased content of CNTs and CB defects, achieved during the sonication time, leads to an increased reactivity toward 1,1-diphenyl-2-pycryl (DPPH) radicals and an enhanced anti-oxidant activity toward macro-radicals, coming from the photo-degradation of the host polymer matrix. The studies of photo-oxidative behavior of the nanocomposites, based on Ultra High Molecular Weight (UHMWPE), reveal that the us treatment of the nanoparticles has a benefic effect on the oxidative resistance of the nanocomposites, especially at long exposure times. Overall, the ultra-sound-assisted treatment can be considered twofold powerful tool: (i) for disruption of the nanoparticles aggregations, and (ii) for capitalization of surface defects, amplifying and tuning in a controlled way the radical scavenging activity of the carbonaceous nanoparticles.

Preparation of palladated porous nitrogen-doped carbon using halloysite as porogen: disclosing its utility as a hydrogenation catalyst

In this article, halloysite nanoclay (Hal) was used as porogen for the synthesis of nitrogen doped porous carbon material with high specific surface area and pore volume. To this purpose, polymerization of melamine and terephthalaldehyde (MT) was performed in the presence of amine-functionalized carbon coated Hal (Hal@Glu-2N) that was prepared from hydrothermal treatment of Hal and glucose. Then, the prepared nanocomposite was palladated and carbonized to afford Pd@Hal@C. To further improve the textural properties of the nanocomposite, and introduce more pores in its structure, Hal nanotubes were etched. The characterization of the resulting compound, Pd@C, and comparing it with Pd@Hal@C, showed that etching of Hal significantly increased the specific surface area and pore volume in Pd@C. Pd@C was successfully used as a heterogeneous catalyst for promoting hydrogenation of nitroarens in aqueous media using hydrogen with atmospheric pressure as a reducing agent. The comparison of the structural features and catalytic activity of the catalyst with some control catalysts, including, Pd@Hal, Pd@Hal@Glu, Pd@Hal@Glu-MT and Pd@Hal@C confirmed that nitrogen groups in C could improve the Pd anchoring and suppress its leaching, while etching of Hal and introduction of more pores could enhance the catalytic activity through facilitating the mass transfer.

Functional biohybrid materials based on halloysite, sepiolite and cellulose nanofibers for health applications

Biohybrid materials were prepared by co-assembling the three following components: nanotubular halloysite, microfibrous sepiolite, and cellulose nanofibers dispersed in water, in order to exploit the most salient features of each individual component and to render homogeneous, flexible, yet strong films. Indeed, the incorporation of halloysite improves the mechanical performance of the resulting hybrid nanopapers and the assembly of the three components modifies the surface features concerning wetting properties compared to pristine materials, so that the main characteristics of the resulting materials become tunable with regard to certain properties. Owing to their hierarchical porosity together with their diverse surface characteristics, these hybrids can be used in diverse biomedical/pharmaceutical applications. Herein, for instance, loading with two model drugs, salicylic acid and ibuprofen, allows controlled and sustained release as deduced from antimicrobial assays, opening a versatile path for developing other related organic-inorganic materials of potential interest in diverse application fields.

Simultaneous Removal and Recovery of Metal Ions and Dyes from Wastewater through Montmorillonite Clay Mineral

The main objective of this work was to evaluate the potential of Montmorillonite nanoclay (Mt), readily and inexpensively available, for the simultaneous adsorption (and removal) of two classes of pollutants: metal ions and dyes. The attention was focused on two "model" pollutants: Ce(III) and crystal violet (CV). The choice is due to the fact that they are widespread in wastewaters of various origins. These characteristics, together with their effect on human health, make them ideal for studies on water remediation. Moreover, when separated from wastewater, they can be recycled individually in industrial production with no or simple treatment. Clay/pollutant hybrids were prepared under different pH conditions and characterized through the construction of the adsorption isotherms and powder X-ray diffraction. The adsorption behavior of the two contaminants was revealed to be significantly different: the Langmuir model reproduces the adsorption isotherm of Ce(III) better, thus indicating that the clay offers a unique adsorption site to the metal ions, while the Freundlich model proved to be the most reliable for the uptake of CV which implies heterogeneity of adsorption sites. Moreover, metal ions do not adsorb at all under acidic conditions, whereas the dye is able to adsorb under all the investigated conditions. The possibility to modulate the adsorption features by simply changing the pH conditions was successfully employed to develop an efficient protocol for the removal and separation of the different components from aqueous solutions mimicking wastewaters.

Safely Dissolvable and Healable Active Packaging Films Based on Alginate and Pectin

Extensive usage of long-lasting petroleum based plastics for short-lived application such as packaging has raised concerns regarding their role in environmental pollution. In this research, we have developed active, healable, and safely dissolvable alginate-pectin based biocomposites that have potential applications in food packaging. The morphological study revealed the rough surface of these biocomposite films. Tensile properties indicated that the fabricated samples have mechanical properties in the range of commercially available packaging films while possessing excellent healing efficiency. Biocomposite films exhibited higher hydrophobicity properties compared to neat alginate films. Thermal analysis indicated that crosslinked biocomposite samples possess higher thermal stability in temperatures below 120 °C, while antibacterial analysis against E. coli and S. aureus revealed the antibacterial properties of the prepared samples against different bacteria. The fabricated biodegradable multi-functional biocomposite films possess various imperative properties, making them ideal for utilization as packaging material.

The Essential Oil of Thymbra capitata and its Application as A Biocide on Stone and Derived Surfaces

Many chemicals used nowadays for the preservation of cultural heritage pose a risk to both human health and the environment. Thus, it is desirable to find new and eco-friendly biocides that can replace the synthetic ones. In this regard, plant essential oils represent effective alternatives to synthetic substances for the preservation of historical monuments. Thymbra capitata (syn. Thymus capitatus) is a medicinal and aromatic plant growing in the Mediterranean area and endowed with important pharmacological properties related to its essential oil. Among them, the antimicrobial ones make the T. capitata essential oil an ideal candidate for industrial applications; for instance, as biocide for the inhibition and elimination of biological patinas of cyanobacteria and green algae on historical monuments. In the present work, we studied the chemical composition of the essential oil from T. capitata growing in Malta by gas chromatography-mass spectrometry (GC/MS). The major volatile component is the phenolic monoterpene carvacrol (73.2%), which is capable of damaging the cytoplasmic membrane and to interfere both in the growth curve and in the invasive capacity, though the contribution of minor components γ-terpinene and p-cymene cannot be disregarded. For the oil application on the stone surface, Pickering emulsions systems were prepared with an essential oil/water 1:3 mass ratio stabilized with kaolinite at 4 mass% in the presence of Laponite^®; this allowed to limit the fast volatility of the oil and guaranteed a better application and an easier removal from the artefacts attacked by biodeteriogens both indoor and outdoor. This formulation caused the elimination of biodeteriogens from treated surfaces without residuals or films on artworks surface, and the effect was retained up to four months.

Selective Antimicrobial Effects of Curcumin@Halloysite Nanoformulation: A Caenorhabditis elegans Study

Alterations in the normal gastrointestinal microbial community caused by unhealthy diet, environmental factors, and antibiotic overuse may severely affect human health and well-being. Novel antimicrobial drug formulations targeting pathogenic microflora while not affecting or even supporting symbiotic microflora are urgently needed. Here we report fabrication of a novel antimicrobial nanocontainer based on halloysite nanotubes loaded with curcumin and protected with a dextrin outer layer (HNTs+Curc/DX) and its effective use to suppress the overgrowth of pathogenic bacteria in Caenorhabditis elegans nematodes. Nanocontainers have been obtained using vacuum-facilitated loading of hydrophobic curcumin into halloysite lumens. We have applied UV-vis and infrared spectroscopy, thermogravimetry and microscopy to characterize the HNTs+Curc/DX nanocontainers. In experiments in vitro we found that HNTs+Curc/DX effectively suppressed the growth of Serratia marcescens cells, whereas Escherichia coli bacteria were not affected. We applied HNTs+Curc/DX nanocontainers to alleviate the S. marcescens infection in C. elegans nematodes in vivo. The nematodes ingest HNTs+Curc/DX at 4-6 ng per worm, which results in improvement of the nematodes' fertility and life expectancy. Remarkably, treatment of S. marcescens-infected nematodes with HNTs+Curc/DX nanocontainers completely restored the longevity, demonstrating the enhanced bioavailability of hydrophobic curcumin. We believe that our results reported here open new avenues for fabrication of effective antimicrobial nanoformulations based on hydrophobic drugs and clay nanotubes.