Gradual hydrophobization of silica aerogel for controlled drug release

A Review on Hydrophobically Associated Alginates: Approaches and Applications

Alginates are linear anionic polysaccharides, which are well-known for their biocompatible, nontoxic, and biodegradable nature. The polymer consists of alternating units of β-(1 → 4)-linked D-mannuronic acid (M) and α-(1 → 4)-linked L-guluronic acid (G) that have hydroxyl and carboxyl groups as the main functional groups. As a large number of free carboxyl and hydroxyl groups are present in the polymeric chain, the polymer is predominantly hydrophilic. The food and pharmaceutical industries have been the most extensive utilizers of alginates to produce gelling and thickening agents. However, by imparting hydrophobicity to alginates, the range of applications can be widened. Although there are reviews on alginate and its chemical modifications, reviews focusing on hydrophobically associated alginates have not been presented. The commonly used chemical modifications to incorporate hydrophobicity include esterification, Ugi reaction, reductive amination, and graft copolymerization. The hydrophobically modified alginates play an important role in delivery of hydrophobic drugs and pesticides as the modification increases the affinity toward hydrophobic components and helps in their sustained release. Due to their nontoxic and edible nature, they find use in the food industry as emulsion stabilizer to stabilize oil-in-water emulsions and to improve creaming ability. Further, alginate-based materials such as membranes, aerogels, and films are hydrophobically modified to improve their functionality and applicability to water treatment and food packaging. This Review aims to highlight the important chemical modifications and methods that are done to impart hydrophobicity to alginate, and the applications of hydrophobically modified alginates in different sectors ranging from drug delivery to food packaging are discussed.

Additive Manufacturing of Transparent Multi-Component Nanoporous Glasses

Fabrication of glass with complex geocd the low resolution of particle-based or fused glass technologies. Herein, a high-resolution 3D printing of transparent nanoporous glass is presented, by the combination of transparent photo-curable sol-gel printing compositions and digital light processing (DLP) technology. Multi-component glass, including binary (Al2 O3 -SiO2 ), ternary (ZnO-Al2 O3 -SiO2 , TiO2 -Al2 O3 -SiO2 ), and quaternary oxide (CaO-P2 O5 -Al2 O3 -SiO2 ) nanoporous glass objects with complex shapes, high spatial resolutions, and multi-oxide chemical compositions are fabricated, by DLP printing and subsequent sintering process. The uniform nanopores of Al2 O3 -SiO2 -based nanoporous glasses with the diameter (≈6.04 nm), which is much smaller than the visible light wavelength, result in high transmittance (>95%) at the visible range. The high surface area of printed glass objectives allows post-functionalization via the adsorption of functional guest molecules. The photoluminescence and hydrophobic modification of 3D printed glass objectives are successfully demonstrated. This work extends the scope of 3D printing to transparent nanoporous glasses with complex geometry and facile functionalization, making them available for a wide range of applications.

The processes behind drug loading and release in porous drug delivery systems

Porous materials are ubiquitous and exhibit properties suitable for depositing therapeutic compounds. Drug loading in porous materials can protect the drug, control its release rate, and improve its solubility. However, to achieve such outcomes from porous delivery systems, effective incorporation of the drug in the internal porosity of the carrier must be guaranteed. Mechanistic knowledge of the factors influencing drug loading and release from porous carriers allows rational design of formulations by selecting a suitable carrier for each application. Much of this knowledge exists in research areas other than drug delivery. Thus, a comprehensive overview of this topic from the drug delivery aspect is warranted. This review aims to identify the loading processes and carrier characteristics influencing the drug delivery outcome with porous materials. Additionally, the kinetics of drug release from porous materials are elucidated, and the common approaches to mathematical modeling of these processes are outlined.

Emerging Trends in Nanotechnology: Aerogel-Based Materials for Biomedical Applications

At present, aerogel is one of the most interesting materials globally. The network of aerogel consists of pores with nanometer widths, which leads to a variety of functional properties and broad applications. Aerogel is categorized as inorganic, organic, carbon, and biopolymers, and can be modified by the addition of advanced materials and nanofillers. Herein, this review critically discusses the basic preparation of aerogel from the sol-gel reaction with derivation and modification of a standard method to produce various aerogels for diverse functionalities. In addition, the biocompatibility of various types of aerogels were elaborated. Then, biomedical applications of aerogel were focused on this review as a drug delivery carrier, wound healing agent, antioxidant, anti-toxicity, bone regenerative, cartilage tissue activities and in dental fields. The clinical status of aerogel in the biomedical sector is shown to be similarly far from adequate. Moreover, due to their remarkable properties, aerogels are found to be preferably used as tissue scaffolds and drug delivery systems. The advanced studies in areas including self-healing, additive manufacturing (AM) technology, toxicity, and fluorescent-based aerogel are crucially important and are further addressed.

Research progress and applications of silica-based aerogels - a bibliometric analysis

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields. In order to grasp the progress of silica-based aerogels, we utilize bibliometrics and visualization methods to analyze the research hotspots and the application of this important field. Firstly, we collect all the publications on silica-based aerogels and then analyze their research trends and performances by a bibliometric method regarding publication year/citation, country/institute, journals, and keywords. Following this, the major research hotspots of this area with a focus on synthesis, mechanical property regulation, and the applications for thermal insulation, adsorption, and Cherenkov detector radiators are identified and reviewed. Finally, current challenges and directions in the future regarding silica-based aerogels are also proposed.

Silica aerogels are three-dimensional porous materials that were initially produced in 1931. During the past nearly 90 years, silica aerogels have been applied extensively in many fields.