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The development of fluorescent materials that can act as sensors for the determination of metal ions in biological fluids is important since they show, among others, high sensitivity and specificity. However, most of the molecules that are used for these purposes possess a very low solubility in aqueous media, and, thus, it is necessary to adopt some derivation strategies. Clay minerals, for example, hectorite, as natural materials, are biocompatible and available in large amounts at a very low cost that have been extensively used as carrier systems for the delivery of different hydrophobic species. In the present work, we report the synthesis and characterization of a hectorite/phenanthroline nanomaterial as a potential fluorescent sensor for Zn ion detection in water. The interaction of phenanthroline with the Ht interlaminar space was thoroughly investigated, via both theoretical and experimental studies (i.e., thermogravimetry, FT-IR, UV-vis and fluorescence spectroscopies and XRD measurements), while its morphology was imaged by scanning electron microscopy. Afterwards, the possibility to use it as sensor for the detection of Zn2+ ions, in comparison to other metal ions, was investigated through fluorescent measurements, and the stability of the solid Ht/Phe/Zn complex was assessed by different experimental and theoretical measurements. [ABSTRACT FROM AUTHOR]

Recently, fluorescent sensors have gained considerable attention due to their high sensitivity, low cost and noninvasiveness. Among the different materials that can be used for this purpose, carbon dots (CDs) represent valuable candidates for applications in sensing. These, indeed, are easily synthesized, show high quantum yield and are highly biocompatible. However, it was pointed out that the photoluminescence properties of these nanomaterials are strictly dependent on the synthetic and purification methods adopted. The presence of halloysite nanotubes (HNTs), a natural, low cost and biocompatible clay mineral, has been found to be efficient in obtaining small and highly monodispersed CDs without long and tedious purification techniques. Herein, we report the comparison of synthetic pathways for obtaining halloysite-N-doped CDs (HNTs-NCDs) that could be used in biological sensing. One was based on the synthesis of N-doped CDs by a bottom-up approach on HNTs' surface by a MW pyrolysis process; the other one was based on the post-modification of pristine N-doped CDs with halloysite derivatives. The evaluation of the best synthetic route was performed by different physico-chemical techniques. It was found that the bottom-up approach led to the formation of N-doped CDs with different functional groups onto the HNTs' surface. This evidence was also translated in the different fluorescence quantum yields and the existence of several functional groups in the obtained materials was investigated by potentiometric titrations. Furthermore, the ability of the synthesized nanomaterials as sensors for Fe3+ ions detection was assessed by spectroscopic measurements, and the cellular uptake was verified by confocal/fluorescence microscopies as well. [ABSTRACT FROM AUTHOR]

Nowadays the use of hydrogels for biomedical purposes is increasing because of their interesting features that allow the development of targeted drug delivery systems. Herein, hydrogel based on Laponite® (Lap) clay mineral as gelator and cucurbit[6]uril (CB[6]) molecules were synthetized for the delivery of flufenamic acid (FFA) for potential topical application. Firstly, the interaction between CB[6] and FFA was assessed by UV‐vis spectroscopic measurements and molecular modeling calculations. Then, the obtained complex was used as filler for Lap hydrogel (Lap/CB[6]/FFA). The properties of the hydrogel in terms of viscosity and, self‐repair abilities were investigated; its morphology was imaged by scanning electron and polarized optical microscopies. Furthermore, the changes in the hydrodynamic radii and in the colloidal stability of CB[6]/Lap mixture were investigated in terms of translational diffusion from dynamic light scattering and ζ‐potential measurements. Finally, the kinetic in vitro release of FFA, from Lap/CB[6]/FFA hydrogel, was studied in a medium mimicking the pH of skin and the obtained results were discussed both by an experimental point of view and by molecular modeling calculations. [ABSTRACT FROM AUTHOR]

[Display omitted] Development of nanocomposite coating with antibiofilm properties is of fundamental importance to efficient fight biofilm formation preventing infections in biomedical area. In this context, halloysite nanotubes (HNTs), biocompatible and low-cost clay mineral, have been efficiently used as filler for different polymeric matrices affording several nanocomposites with appealing antimicrobial properties. The modification of HNTs surfaces represents a valuable strategy to improve the utilization of the clay for biological purposes. Experiments. Herein, the covalent modification of the HNTs lumen with properly designed dopamine derivatives with different perfluoroalkyl chain length is reported. The obtained nanomaterials are thoroughly characterized by several techniques. As proof of concept the antibiofilm properties on E. coli strain of the nanomaterials are assayed as well. Finally, the HNTs fillers were introduced into a polydopamine matrix allowing for the preparation of functional coatings, resistant to formation of microbial biofilms. All characterization methods proved the selectivity of the modification and the increased hydrophobicity of the lumen. In particular 27Al solid state nuclear magnetic resonance (NMR) spectra showed a upfield shift of the Al signal. Studies on the antibiofilm properties highlighted different activities according to the length of perfluoroalkyl chains of organic molecules as proved by 19F solid state NMR spectra. The synthetized materials were promising for future application as coatings on medical implants. [ABSTRACT FROM AUTHOR]

Bacterial infections represent one of the major causes of mortality worldwide. Therefore, over the years, several nanomaterials with antibacterial properties have been developed. In this context, clay minerals, because of their intrinsic properties, have been efficiently used as antimicrobial agents since ancient times. Halloysite nanotubes are one of the emerging nanomaterials that have found application as antimicrobial agents in several fields. In this review, we summarize some examples of the use of pristine and modified halloysite nanotubes as antimicrobial agents, scaffolds for wound healing and orthopedic implants, fillers for active food packaging, and carriers for pesticides in food pest control. [ABSTRACT FROM AUTHOR]

The article titled "Front Cover: Thixotropic Hydrogels Based on Laponite® and Cucurbituril for Delivery of Lipophilic Drug Molecules" in the journal ChemPlusChem discusses the potential use of laponite hydrogels filled with a supramolecular complex of cucurbit[6]uril and flufenamic acid for topical drug delivery. The cover picture showcases this application. The research article, authored by Viseras‐Iborra, Riela, and their colleagues, provides more detailed information on this topic. The authors of the article are Marina Massaro, Giuseppe Cinà, Ana Borrego‐Sánchez, C. Ignacio Sainz‐Díaz, César Viseras‐Iborra, Rita Sánchez‐Espejo, Raquel de Melo Barbosa, Federica Leone, Ivana Pibiri, Renato Noto, and Serena Riela. [Extracted from the article]

The design and development of nanomaterials capable of penetrate cancer cells is fundamental when anticancer therapy is involved. The use of collagenase (Col) is useful since this enzyme can degrade collagen, mainly present in the tumor extracellular matrix. However, its use is often limited since collagenase suffers from inactivation and short half-life. Use of recombinant ultrapure collagenase or carrier systems for their delivery are among the strategies adopted to increase the enzyme stability. Herein, based on the more stability showed by recombinant enzymes and the possibility to use them in anticancer therapy, we propose a novel strategy to further increase their stability by using halloysite nanotubes (HNTs) as carrier. ColG and ColH were supramolecularly loaded onto HNTs and used as fillers for Veegum gels. The systems could be used for potential local administration of collagenases for solid tumor treatment. All techniques adopted for characterization showed that halloysite interacts with collagenases in different ways depending with the Col considered. Furthermore, the hydrogels showed a very slow release of the collagenases within 24 h. Finally, biological assays were performed by studying the digestion of a type-I collagen matrix highlighting that once released the Col still possessed some activity. Thus we developed carrier systems that could further increase the high recombinant collagenases stability, preventing their inactivation in future in vivo applications for potential local tumor treatment. [Display omitted] • Halloysite was as carrier for recombinant collagenases to increase their stability. • The nanomaterials were used as fillers for Veegum gels for potential local tumor treatment. • Collagenases (Col) interact in different way with halloysite surfaces. • A very slow release of Col was observed from the nanocomposite hydrogels. • Once released Col preserve their enzymatic activity. [ABSTRACT FROM AUTHOR]

In the last years, the use of clay minerals for pharmaceutical purposes has increased due to their interesting properties. Hectorite (Ht) is a clay belonging to the smectite group which has attracted attention for applications in biology, tissue engineering and as drug carrier and delivery system. However, the mechanisms involved in Ht cellular uptake and transport into cells, are still unclear. Herein, we used a labeled Ht (Ht/ 1Cl) to study both the cellular uptake, by confocal laser scanning microscopy, and internalization pathways involved in the cellular uptake, by various endocytosis-inhibiting studies and fluorescence microscopy. These studies highlighted that Ht can penetrate the cellular membrane, localizing mainly in the cytoplasm. The main intracellular transport mechanisms are the ATP-dependent ones and those where filaments and microtubules are involved. Finally, as proof of concept for the potential of Ht as carrier system, we envisaged the covalent grafting of the anticancer molecule methotrexate (MTX), chosen as model, to obtain the Ht-MTX nanomaterial. The covalent linkage was confirmed by several techniques and the morphology of the obtained nanomaterial was imaged by SEM and TEM investigations. The kinetic release of the drug from the Ht-MTX nanomaterial in physiological conditions was studied as well. Furthermore, cytotoxic studies on different cell lines, namely, HL-60, HL-60R, MCF-7, 5637, UMUC3 and RT112 showed that Ht could be a promising material for anticancer therapy. [Display omitted] • Labeled Ht was used to study the cellular uptake and internalization pathways. • Ht can penetrate the cellular membrane, localizing mainly in the cytoplasm. • The main intracellular transport mechanisms are the ATP-dependent ones. • Mechanisms where filaments and microtubules are involved are also possible. • Ht was covalent modified with methotrexate for biological applications. [ABSTRACT FROM AUTHOR]

The design of multifunctional nanomaterials which can help the healing processes of skin, preventing the bacterial infections, is crucial for the development of suitable therapy for the treatment of chronic lesions. The use of clay minerals in wound healing applications is well documented since the prehistoric period and offers several advantages due to their intrinsic properties. Herein, we report the development of ciprofloxacin carrier systems based on hectorite/halloysite (Ht/Hal) hybrid hydrogels for potential wound healing applications. To achieve this objective firstly the ciprofloxacin molecules were loaded onto Hal by a supramolecular and covalent approach. The so obtained fillers were thoroughly investigated by several techniques and at molecular level by means of quantum mechanics calculations along with empirical interatomic potentials. Afterwards the modified Hal were used as filler for Ht hydrogels. The introduction of modified Hal, in hectorite hydrogel, helps the gel formation with an improvement of the rheological properties. The in vitro kinetic release from both the fillers and from the hybrid hydrogels was studied both at skin's pH (5.4) and under neutral conditions (pH 7.4); in addition, the factors controlling the ciprofloxacin release process were determined and discussed. Finally, the in vitro biocompatibility of the Hal fillers was evaluated by means of cytotoxic assays and laser scanning confocal microscopy on normal human dermal fibroblasts. [Display omitted] • Ciprofloxacin carrier systems based on Ht/Hal hybrid hydrogels were developed. • Ciprofloxacin molecules were loaded onto Hal filler by a supramolecular and covalent approach. • The introduction of modified Hal in Ht hydrogel improved rheological properties. • Kinetic release of the drug was studied both at skin's pH and under neutral conditions. • Biocompatibility of the Hal fillers was evaluated on normal human dermal fibroblasts. [ABSTRACT FROM AUTHOR]

Halloysite is an aluminosilicate clay with a predominantly hollow tubular structure (HNTs) able to act as a nanocontainer for the encapsulation of several chemicals. However, HNTs possess low affinity for metal ions in their pristine form and they need to be modified for improving their adsorption capabilities. Therefore, to overcome this issue herein we report a straightforward approach for the covalent modification of the external surface of halloysite nanotubes with hectorite clay. Compared to halloysite, hectorite possesses a lamellar structure with higher cation exchange capacity. The covalent linkage between the two clays was verified by several techniques (FTIR spectroscopy, 13C CP-MAS NMR, TGA, ζ−potential, DLS, and XRD measurements) and the morphology was imaged by TEM investigations. As proof of concept the adsorption ability of the obtained nanomaterial in comparison to pristine clays was proved using ciprofloxacin and silver ions chosen as models for their different chemical characteristics. [ABSTRACT FROM AUTHOR]

Halloysite nanotubes (HNTs), clay minerals belonging to the kaolin groups, are emerging nanomaterials which have attracted the attention of the scientific community due to their interesting features, such as low-cost, availability and biocompatibility. In addition, their large surface area and tubular structure have led to HNTs' application in different industrial purposes. This review reports a comprehensive overview of the historical background of HNT utilization in the last 20 years. In particular it will focus on the functionalization of the surfaces, both supramolecular and covalent, following applications in several fields, including biomedicine, environmental science and catalysis. [ABSTRACT FROM AUTHOR]

Halloysite surface was modified with tetrabutylammonium iodide, and then the obtained nanomaterial was used as support for ZnO nanoparticles. After characterization, the nanomaterial was used as a catalyst for fatty acid methyl esters (FAMEs) production. The recyclability of the nanomaterial was also investigated, and the optimization of reaction conditions by the design of experiments approach was performed as well. In addition, the synthesized nanomaterial was tested as a catalyst for FAME production from a series of waste lipids affording biodiesel in moderate to good yields (35–95%), depending on the matrix. To fully exploit the feasibility of clay minerals as catalysts in biodiesel formation, a screening of different clays and clay minerals with different morphologies and compositions, such as sepiolite, palygorskite, bentonite, and hectorite was also performed in the esterification of FFAs (a mixture of 1:1 palmitic and stearic acids). Finally, hectorite, chosen as a model of 2:1 clay minerals, was covalently modified, and tested as a catalyst in the esterification of FFAs. [Display omitted] • TBAI covalently linked on halloysite surface was used as support for ZnO NPs. • The nanomaterial was used as a catalyst for fatty acid methyl esters production. • It was used on a series of waste lipids affording biodiesel in moderate to good yields (35–95%). • A screening of different clay minerals with different morphologies and composition was also performed. • Hectorite was covalent modified to improve catalytic activity in the esterification of free fatty acids. [ABSTRACT FROM AUTHOR]