Daylight Bactericidal Titania Textiles: A Contribution to Nosocomial Infections Control

Ultrasound-assisted water oxidation: unveiling the role of piezoelectric metal-oxide sonocatalysts for cancer treatment

Ultrasound radiation has been widely used in biomedical application for both diagnosis and therapy. Metal oxides nanoparticles (NPs), like ZnO or TiO2 NPs, have been widely demonstrated to act as excellent sonocatalysts and significantly enhance cavitation at their surface, making them optimal for sonodynamic cancer therapy. These NPs often possess semiconductive and piezoelectric properties that contribute to the complex phenomena occurring at the water-oxide interface during sonostimulation. Despite the great potential in applied sonocatalysis and water splitting, the complex mechanism that governs the phenomenon is still a research subject. This work investigates the role of piezoelectric ZnO micro- and nano-particles in ultrasound-assisted water oxidation. Three metal oxides presenting fundamental electronic and mechanical differences are evaluated in terms of ultrasound-triggered reactive oxygen species generation in aqueous media: electromechanically inert SiO2 NPs, semiconducting TiO2 NPs, piezoelectric and semiconducting ZnO micro- and nanoparticles with different surface areas and sizes. The presence of silver ions in the aqueous solution was further considered to impart a potential electron scavenging effects and better evaluate the oxygen generation performances of the different structures. Following sonoirradiation, the particles are optically and chemically analyzed to study the effect of sonostimulation at their surface. The production of gaseous molecular oxygen is measured, revealing the potential of piezoelectric particles to generate oxygen under hypoxic conditions typical of some cancer environments. Finally, the best candidates, i.e. ZnO nano and micro particles, were tested on osteosarcoma and glioblastoma cell lines to demonstrate their potential for cancer treatment.

Daylight Photoactive TiO2 Sol-Gel Nanoparticles: Sustainable Environmental Contribution

Visible-light-photoactive titania micro- or nanoparticles excel in a wide range of industrial areas, particularly in environmental remediation. The sol-gel methodology is one pivotal technique which has been successfully used to synthesize either crystalline and amorphous TiO₂ micro- and nanoparticles due to its outstanding chemical simplicity and versatility, along with the green chemistry approach. This short review aims to collect and discuss the most recent developments in visible-light-photoactive titania-based nanoparticles in the environmental remediation area. Titania co-doping, titania composite design, and, recently, amorphous networks have been the most used strategies to address this goal. Finally, a prediction regarding the future of these fields is given.

Hyaluronic Acid Allows Enzyme Immobilization for Applications in Biomedicine

Enzymes are proteins that control the efficiency and effectiveness of biological reactions and systems, as well as of engineered biomimetic processes. This review highlights current applications of a diverse range of enzymes for biofuel production, plastics, and chemical waste management, as well as for detergent, textile, and food production and preservation industries respectively. Challenges regarding the transposition of enzymes from their natural purpose and environment into synthetic practice are discussed. For example, temperature and pH-induced enzyme fragilities, short shelf life, low-cost efficiency, poor user-controllability, and subsequently insufficient catalytic activity were shown to decrease pertinence and profitability in large-scale production considerations. Enzyme immobilization was shown to improve and expand upon enzyme usage within a profit and impact-oriented commercial world and through enzyme-material and interfaces integration. With particular focus on the growing biomedical market, examples of enzyme immobilization within or onto hyaluronic acid (HA)-based complexes are discussed as a definable way to improve upon and/or make possible the next generation of medical undertakings. As a polysaccharide formed in every living organism, HA has proven beneficial in biomedicine for its high biocompatibility and controllable biodegradability, viscoelasticity, and hydrophilicity. Complexes developed with this molecule have been utilized to selectively deliver drugs to a desired location and at a desired rate, improve the efficiency of tissue regeneration, and serve as a viable platform for biologically accepted sensors. In similar realms of enzyme immobilization, HA’s ease in crosslinking allows the molecule to user-controllably enhance the design of a given platform in terms of both chemical and physical characteristics to thus best support successful and sustained enzyme usage. Such examples do not only demonstrate the potential of enzyme-based applications but further, emphasize future market trends and accountability.

Smart Shockwave Responsive Titania-Based Nanoparticles for Cancer Treatment

Nanomedicine is an emerging treatment approach for many cancers, characterized by having high sensitivity and selectivity for tumor cells and minimal toxic effects induced by the conventional chemotherapeutics. In these context, smart nanoparticles (NPs) are getting increasingly relevant in the development of new therapies. NPs with specific chemical composition and/or structure and being stimuli-responsive to magnetic, light or ultrasound waves are new promising tools. In the present work, amorphous-titania propyl-amine functionalized (a-TiO₂-NH₂) NPs, coated with bovine serum albumin (BSA), are stimulated with high energy shock waves to induce cytotoxic effects in cancer cells. First, a new method to coat a-TiO₂-NH₂ NPs with BSA (a-TiO₂-NH₂/BSA) was proposed, allowing for a high dispersion and colloidal stability in a cell culture media. The a-TiO₂-NH₂/BSA NPs showed no cancer cell cytotoxicity. In a second step, the use of shock waves to stimulate a-TiO₂-NH₂/BSA NPs, was evaluated and optimized. A systematic study was performed in in vitro cell culture aiming to impair the cancer cell viability: NP concentrations, time steps and single versus multiple shock waves treatments were studied. The obtained results highlighted the relevance of NPs design and administration time point with respect to the shock wave treatment and allow to hypothesize mechanical damages to cells.

What Is Driving the Growth of Inorganic Glass in Smart Materials and Opto-Electronic Devices?

Inorganic glass is a transparent functional material and one of the few materials that keeps leading innovation. In the last decades, inorganic glass was integrated into opto-electronic devices such as optical fibers, semiconductors, solar cells, transparent photovoltaic devices, or photonic crystals and in smart materials applications such as environmental, pharmaceutical, and medical sensors, reinforcing its influence as an essential material and providing potential growth opportunities for the market. Moreover, inorganic glass is the only material that is 100% recyclable and can incorporate other industrial offscourings and/or residues to be used as raw materials. Over time, inorganic glass experienced an extensive range of fabrication techniques, from traditional melting-quenching (with an immense diversity of protocols) to chemical vapor deposition (CVD), physical vapor deposition (PVD), and wet chemistry routes as sol-gel and solvothermal processes. Additive manufacturing (AM) was recently added to the list. Bulks (3D), thin/thick films (2D), flexible glass (2D), powders (2D), fibers (1D), and nanoparticles (NPs) (0D) are examples of possible inorganic glass architectures able to integrate smart materials and opto-electronic devices, leading to added-value products in a wide range of markets. In this review, selected examples of inorganic glasses in areas such as: (i) magnetic glass materials, (ii) solar cells and transparent photovoltaic devices, (iii) photonic crystal, and (iv) smart materials are presented and discussed.

Biomimetic Amorphous Titania Nanoparticles as Ultrasound Responding Agents to Improve Cavitation and ROS Production for Sonodynamic Therapy

Conventional therapies to treat cancer often exhibit low specificity, reducing the efficiency of the treatment and promoting strong side effects. To overcome these drawbacks, new ways to fight cancer cells have been developed so far focusing on nanosystems. Different action mechanisms to fight cancer cells have been explored using nanomaterials, being their remote activation one of the most promising. Photo- and sonodynamic therapies are relatively new approaches that emerged following this idea. These therapies are based on the ability of specific agents to generate highly cytotoxic reactive oxygen species (ROS) by external stimulation with light or ultrasounds (US), respectively. Crystalline (TiO2) and amorphous titania (a-TiO2) nanoparticles (NPs) present a set of very interesting characteristics, such as their photo-reactivity, photo stability, and effective bactericidal properties. Their production is inexpensive and easily scalable; they are reusable and demonstrated already to be nontoxic. Therefore, these NPs have been increasingly studied as promising photo- or sonosensitizers to be applied in photodynamic/sonodynamic therapies in the future. However, they suffer from poor colloidal stability in aqueous and biological relevant media. Therefore, various organic and polymer-based coatings have been proposed. In this work, the role of a-TiO2 based NPs synthesized through a novel, room-temperature, base-catalyzed, sol-gel protocol in the generation of ROS and as an enhancer of acoustic inertial cavitation was evaluated under ultrasound irradiation. A novel biomimetic coating based on double lipidic bilayer, self-assembled on the a-TiO2-propylamine NPs, is proposed to better stabilize them in water media. The obtained results show that the biomimetic a-TiO2-propylamine NPs are promising candidates to be US responding agents, since an improvement of the cavitation effect occurs in presence of the developed NPs. Further studies will show their efficacy against cancer cells.

"Tailoring the TiO2 phases through microwave-assisted hydrothermal synthesis: Comparative assessment of bactericidal activity"

Nanocrystalline titania (TiO₂) is one of the most investigated crystalline nanostructured systems in the field of materials science. The technological applications of this material are related to its optoelectronic and photocatalytic properties, which in turn are strongly dependent on the crystal phase (i.e., anatase, brookite, and rutile), particle size, and surface structure. However, systematic comparative studies of all its crystal phases are scarce in literature due to difficulties in providing a controlled synthesis, which is primarily important in obtaining the brookite phase. In this report, the synthesis of TiO₂ nanoparticles in the anatase, brookite, and rutile structures was explored, using amorphous TiO₂ as a common precursor under microwave-assisted hydrothermal conditions. The influence of parameters such as temperature, acidity, and precursor concentration on phase crystallization were investigated. The TiO₂ materials (amorphous and crystalline phases as well as commercial Degussa P25) were systematically characterized using Raman spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, UV-visible reflectance spectroscopy, and dynamic and electrophoretic light scattering. The bactericidal activity and photocatalytic antibacterial effectiveness of each material were evaluated through the determination of the minimum inhibitory and bactericidal concentrations, and via the mortality kinetic method under ultraviolet (UV) illumination under similar conditions with two bacterial groups of unique cellular structures: Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). The results are discussed with particular emphasis on the relationship between the synthesis parameters (acidity, precursor concentration, temperature and reaction time) and the bactericidal properties.

Synthesis and Characterization of Novel Integral Asymmetric Monophasic Cellulose-Acetate/Silica/Titania and Cellulose-Acetate/Titania Membranes

Two series of novel integral asymmetric monophasic hybrid membranes, cellulose acetate/silica/titania (CA/SiO₂/TiO₂—series 1) and cellulose acetate/titania (CA/TiO₂—series 2), were developed by the coupling of sol-gel technology and a modified version of the phase inversion technique. SEM micrographs confirmed the integral asymmetric structure of all membranes. ATR-FTIR and ICP-OES results showed that, for the membranes in series 1, TiO₂ is covalently bound to SiO_2, which, in turn, is covalently bound to CA, while for the membranes in series 2, TiO₂ is directly and covalently bound to the CA matrix. Permeation experiments revealed that the permeation performance of the membranes in series 1 is unaffected by the introduction of TiO₂. In contrast, the introduction of TiO₂ in the series 2 membranes increased the hydraulic permeability by a factor of at least 2 when compared to the pristine CA membrane and that incremental additions of TiO₂ further increased the Lp.