Interfacial Self-Assembly in Halloysite Nanotube Composites.

A self-assembly of clay nanotubes in functional arrays for the production of organized organic/inorganic heterostructures is described. These 50-nm-diameter natural alumosilicate nanotubes are biocompatible. Halloysite allows for 10-20 wt % chemical/drug loading into the inner lumen, and it gives an extended release for days and months (anticorrosion, self-healing, flame-retardant, antifouling, and antibacterial composites). The structured surfaces of the oriented nanotube micropatterns enhance interactions with biological cells, improving their capture and inducing differentiation in stem cells. An encapsulation of the cells with halloysite enables control of their growth and proliferation. This approach was also developed for spill petroleum bioremediation as a synergistic process with Pickering oil emulsification. We produced 2-5-nm-diameter particles (Au, Ag, Pt, Co, Ru, Cu-Ni, Fe3O4, ZrO2, and CdS) selectively inside or outside the aluminosilicate clay nanotubes. The catalytic hydrogenation of benzene and phenol, hydrogen production, impacts of the metal core-shell architecture, the metal particle size, and the seeding density were optimized for high-efficiency processes, exceeding the competitive industrial formulations. These core-shell mesocatalysts are based on a safe and cheap natural clay nanomaterial and may be scaled up for industrial applications.

Case Report: Recurrent Type 2 Leprosy Reaction Associated with Multiple Nerve Function Impairments Refractory to Steroids: A Therapeutic Challenge.

Nerve function impairment (NFI) in leprosy results in serious deformities of the face, hands, and feet and contributes significantly to the stigma associated with the disease. Most literature on NFI focuses on either type 1 reaction-associated NFI, or the silent neuropathy, whereas NFI associated with type 2 reaction (T2R) is less well researched. The latter, however, can be more refractory to conventional treatment, not solely owing to its recurrent nature. We present a therapeutically challenging case of a 31-year-old male with borderline lepromatous leprosy with recurrent T2R associated with recurrent and progressive sensorimotor NFI, largely unresponsive to oral steroids and multibacillary, multidrug therapy.

A 1-D model to retrieve the vertical profiles of minor atmospheric constituents for cloud microphysical modeling: I. Formulation and validation.

Determining the number concentration of minor constituents in the atmosphere is very important as it determines the whole tropospheric chemistry process. These constituents may act as cloud condensation nuclei (CCN) and ice nuclei (IN), impacting heterogeneous nucleation inside the cloud. However, the estimations of the number concentration of CCN/IN in cloud microphysical parameters are associated with uncertainties. In the present work, a hybrid Monte Carlo Gear solver has been developed to retrieve profiles of CH4, N2O, and SO2. The idealized experiments have been carried out using this solver for retrieving vertical profiles of these constituents over four megacities, viz., Delhi, Mumbai, Chennai, and Kolkata. Community Long-term Infrared Microwave Coupled Atmospheric Product System (CLIMCAPS) dataset around 0800 UTC (2000UTC) has been used for initializing the number concentration of CH4, N2O, and SO2 for daytime (nighttime). The daytime (nighttime) retrieved profiles have been validated using 2000 UTC (next day 0800 UTC) CLIMCAPS products. ERA5 temperature dataset has been used to estimate the kinematic rate of reactions with 1000 perturbations determined using Maximum Likelihood Estimation (MLE). The retrieved profiles and CLIMCAPS products are in very good agreement, as evidenced by the percentage difference between them within the range of 1.3 × 10-5-60.8 % and the coefficient of determination mainly within the range between 81 and 97 %. However, during the passage of tropical cyclone and western disturbance, its value became as low as 27 and 65 % over Chennai and Kolkata, respectively. The enactment of synoptic scale systems such as western disturbances, tropical cyclone Amphan, and easterly waves caused disturbed weather over these megacities-the retrieved profiles during disturbed weather cause large deviations of vertical profiles of N2O. However, the profiles of CH4 and SO2 have less deviation. It is inferred that incorporating this methodology in the dynamical model will be useful to simulate the realistic vertical profiles of the minor constituents in the atmosphere.

Hot spots localization in proteins by optimized short time Ramanujan Fourier transform.

Specific functions in biological processes are dependent on protein-protein interactions. Hot spot residues play a key role in the determination of these interactions and have wide applications in engineering proteins and drug discovery. Experimental techniques to identify hotspots are often labor intensive and expensive. Also, most of the computational methods which have been developed are structure based and need some training. In this work, hotspots have been identified by sequence information alone using the Resonant Recognition Model (RRM). The proposed method uses characteristic period in place of traditionally used characteristic frequency by RRM-based methods. The characteristic period has been extracted from the consensus spectrum of protein families using the Ramanujan Fourier Transform (RFT). Position-period plots for proteins have been generated using Short Time RFT (ST-RFT) with a Gaussian window. Hot spots have been identified by thresholding of the signal corresponding to the protein's characteristic period in the ST-RFT. To enhance the performance of the ST-RFT, Gaussian window shape parameter has been optimized using concentration measure as a metric. Better sensitivity of this method has been observed compared to other reported RRM-based methods. Since the method is model independent it does not requires any training and can be readily used for any protein sequence provided its interface residues and protein family are known.

Superhydrophobic Polyurethane Foam Coated with Polysiloxane-Modified Clay Nanotubes for Efficient and Recyclable Oil Absorption.

Superhydrophobic polyurethane foam (PUF) is prepared by surface coating of halloysite nanotubes. The nanotubes were first modified by surface grafting with hexadecyltrimethoxysilane, followed by assembly on the PUF by dip coating. This treatment makes the water contact angle of the modified PUF higher than 150°. The modified foam has a highly selective absorption of oils and organic solvents. The absorption ratios of the modified PUF for chloroform and dichloroethane reached 104 and 74, respectively. Such superhydrophobic foam can maintain the oil absorption performance even after 10 absorption-squeezing cycles, demonstrating good recyclability. The modified foam can pick up oil or organic solvent continuously and quickly from water's surface. This hydrophobic nanotube coating also enhances the flame retardancy of the PUF, and the modified foam will extinguish itself maintaining its integrity. The preparation method for hydrophobic and flame-retardant PUF by coating with natural clay nanotubes is a simple process and promises scalable applications in oil-water separation.

Tubule Nanoclay-Organic Heterostructures for Biomedical Applications.

Natural halloysite nanotubes (HNTs) show unique hollow structure, high aspect ratio and adsorption ability, good biocompatibility, and low toxicity, which allow for various biomedical applications in the diagnosis and treatment of diseases. Here, advances in self-assembly of halloysite for cell capturing and bacterial proliferation, coating on biological surfaces and related drug delivery, bone regeneration, bioscaffolds, and cell labeling are summarized. The in vivo toxicity of these clay nanotubes is discussed. Halloysite allows for 10-20% drug loading and can extend the delivery time to 10-100 h. These drug-loaded nanotubes are doped into the polymer scaffolds to release the loaded drugs. The rough surfaces fabricated by self-assembly of the clay nanotubes enhance the interactions with tumor cells, and the cell capture efficacy is significantly improved. Since halloysite has no toxicity toward microorganisms, the bacteria composed within these nanotubes can be explored in oil/water emulsion for petroleum spilling bioremediation. Coating of living cells with halloysite can control the cell growth and is not harmful to their viability. Quantum dots immobilized on halloysite were employed for cell labeling and imaging. The concluding academic results combined with the abundant availability of these natural nanotubes promise halloysite applications in personal healthcare and environmental remediation.

Evolution of Hair Treatment and Care: Prospects of Nanotube-Based Formulations.

A new approach for hair treatment through coating with nanotubes loaded with drugs or dyes for coloring is suggested. This coating is produced by nanotube self-assembly, resulting in stable 2-3 µm thick layers. For medical treatment such formulations allow for sustained long-lasting drug delivery directly on the hair surface, also enhanced in the cuticle openings. For coloring, this process allows avoiding a direct hair contact with dye encased inside the clay nanotubes and provides a possibility to load water insoluble dyes from an organic solvent, store the formulation for a long time in dried form, and then apply to hair as an aqueous nanotube suspension. The described technique works with human and other mammal hairs and halloysite nanoclay coating is resilient against multiple shampoo washing. The most promising, halloysite tubule clay, is a biocompatible natural material which may be loaded with basic red, blue, and yellow dyes for optimized hair color, and also with drugs (e.g., antilice care-permethrin) to enhance the treatment efficiency with sustained release. This functionalized nanotube coating may have applications in human medical and beauty formulations, as well as veterinary applications.

Investigation of Amphiphilic Polypeptoid-Functionalized Halloysite Nanotubes as Emulsion Stabilizer for Oil Spill Remediation.

Halloysite nanotubes (HNTs), naturally occurring and environmental benign clay nanoparticles, have been successfully functionalized with amphiphilic polypeptoid polymers by surface-initiated polymerization methods and investigated as emulsion stabilizers toward oil spill remediation. The hydrophilicity and lipophilicity balance (HLB) of the grafted polypeptoids was shown to affect the wettability of functionalized HNTs and their performance as stabilizers for oil-in-water emulsions. The functionalized HNTs having relatively high hydrophobic content (HLB = 12.0-15.0) afforded the most stable oil-in-water emulsions containing the smallest oil droplet sizes. This has been attributed to the augmented interfacial activities of polypeptoid-functionalized HNTs, resulting in more effective reduction of interfacial tension, enhancement of thermodynamic propensity of the HNT particles to partition at the oil-water interface, and increased emulsion viscosity relative to the pristine HNTs. Cell culture studies have revealed that polypeptoid-functionalized HNTs are noncytotoxic toward Alcanivorax borkumensis, a dominant alkane degrading bacterium found in the ocean after oil spill. Notably, the functionalized HNTs with higher hydrophobic polypeptoid content (HLB = 12.0-14.3) were shown to induce more cell proliferation than either pristine HNTs or those functionalized with less hydrophobic polypeptoids. It was postulated that the functionalized HNTs with higher hydrophobic polypeptoid content may promote the bacterial proliferation by providing larger oil-water interfacial area and better anchoring of bacteria at the interface.

Self-assembly of clay nanotubes on hair surface for medical and cosmetic formulations.

While most hair care formulations are developed on the basis of surfactants or polymers, we introduce self-assembly coating of micro and nanoparticles as the underlying principle for hair modification, protection and enhancement. Halloysite clay nanotubes formed by rolled sheets of aluminosilicate kaolin assemble on the surface of hair forming a robust multilayer coverage. Prior to the application, clay nanotubes were loaded with selected dyes or drug allowing for hair coloring or medical treatment. This facile process is based on a 3-minute application of 1 wt% aqueous dispersion of color/drug loaded halloysite resulting in a ca. 3 µm thick uniform hair surface coating. This technique, which employs a very safe, biocompatible and inexpensive material, is ubiquitous with respect to the species of source of hair and additives in solvent, making it viable as an excipient for conventional medical and veterinarian formulations.

Bacterial proliferation on clay nanotube Pickering emulsions for oil spill bioremediation.

Halloysites (tubular aluminosilicate) are introduced as inexpensive natural nanoparticles that form and stabilize oil-water emulsions. Pickering emulsification can proceed with energies low enough to be afforded by ocean turbulence and the stability of droplets extends over more than a week. The oil/water interface is shown to be roughened and bacteria, which are added for oil degradation, are better attached to such oil droplets than to droplets without halloysites. The metabolic activity of Alcanivorax borkumensis, alkanotrophic bacteria widely distributed in marine environments, is enhanced by halloysite addition. A halloysite-based dispersant system is therefore environmentally friendly and promising for further optimization. The key elements of the described formulations are natural clay nanotubes, which are abundantly available in thousands of tons, thus making this technology scalable for environmental remediation.

Halloysite clay nanotubes for life sciences applications: From drug encapsulation to bioscaffold.

Natural forming clay halloysite is an emerging nanomaterial carrier for sustained drug delivery. These 50 nm diameter aluminosilicate tubes, with inner - alumina and outer - silica surface layers, can be loaded with 10-30 wt% of drug molecules, DNA and enzymes. The opposite charge of the inner and outer halloysite surface allow for selective drug adsorption inside or outside the clay nanotubes. The drug loaded halloysite enhanced the zeta potential of minus 50-60 mV allowing for stable aqueous nanocolloids. Halloysite nanoformulations provide an extended 10-20 h release profile, and may be functionalized (e.g., clogging tubes' end with polymers extending release time to 1-2 weeks or allowing for triggered release), which renders these clay nanostructures as promising controlled delivery systems. Recent studies demonstrate the potential of abundantly available halloysite clay nanotubes for life science applications, from drug delivery via oral or topical administration, to tissue scaffolds and regenerative medicine, while assessing their cellular internalization, stability, biosafety and biocompatibility are featured. The benefits and limitations of halloysite clay nanotubes are discussed, as well as the directions for future developments.