A Review of the Application of Resorcinarenes and SBA-15 in Drug Delivery

Ionic resorcinarenes as drug solubilization agents in water

Resorcinarenes are capable of host-guest complexation with small molecules, however, they are less studied as pharmaceutical drug delivery aids. This article reports on the aqueous-solubility enhancing effect of an octa-sulfonated resorcinarene and a C-hydroxybenzyl ammonium resorcinarene chloride on three hydrophobic drugs: isoniazid, caffeine, and griseofulvin. The findings are backed by dynamic light scattering, isothermal calorimetric titration, and nuclear magnetic resonance experiments in water. Aqueous mixtures of equal volumes of drug compounds and resorcinarene solutions produced a more soluble and clearer unit than solutions of pure drug compounds in water. Light scattering experiments revealed shifts in particle sizes of pure drug compounds to the range of resorcinarene hosts. 1H NMR measurements of resorcinarene-drug mixtures confirmed interactions with shift changes ranging from -0.20 to 0.81 ppm. Binding affinities quantified through ITC experiments ranged between 0.54 and 211 mM, signifying interactions between resorcinarenes and drug compounds necessary for the solubility of the drugs. Cytotoxicity studies suggest that resorcinarenes alone, or complexed with any of the drug compounds, do not exert cytotoxicity in mammalian cells HEK-293 up to 200 μM. We herein propose a set of hydrophilic resorcinarene macrocycles as potential drug solubilizers.

Synthesis of Ordered Mesoporous Silica with Nonionic Surfactant/Anionic Polyelectrolyte as Template under Near-Neutral pH Conditions

Ordered mesoporous silica is widely used in catalysis, adsorption, and biomedicine, among which SBA-15 (Santa Barbara Amorphous-15) is one of the most widely studied. However, the synthesis of SBA-15 often requires strong acid (hydrochloric acid or sulfuric acid), which will not only corrode industrial equipment but also pollute the environment with the wastewater containing strong acid and halogen (sulfur). Here, we demonstrate a green synthetic strategy for SBA-15 under weakly acidic conditions through an anionic assembly route. With the assistance of poly(acrylic acid) (PAA) and 3-aminopropyltrimethoxysilane (APMS), the pH value of the synthesis system can be increased to 4-5, which is a mild near-neutral condition. In addition, halogen-free synthesis using organic acids is also achieved. The powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and N2 sorption characterizations show that the obtained SBA-15 has good texture properties, with a specific surface area of 430-500 m2/g and ordered 6-8 nm mesopores, which is similar to SBA-15 synthesized in traditional strong acid. This strategy provides a facile and environmentally friendly route for the large-scale production of ordered mesoporous materials.

Synthesis of calix (4) resorcinarene based amphiphilic macrocycle as an efficient nanocarrier for Amphotericin-B to enhance its oral bioavailability

The supramolecular-based macrocyclic amphiphiles have fascinating attention and find extensive utilization in the pharmaceutical industry for efficient drug delivery. In this study, we designed and synthesized a new supramolecular amphiphilic macrocycle to serve as an efficient nanocarrier, achieved by treating 4-hydroxybenzaldehyde with 1-bromotetradecane. The derivatized product was subsequently treated with resorcinol to cyclize, resulting in the formation of a calix(4)-resorcinarene-based supramolecular amphiphilic macrocycle. The synthesized macrocycle and intermediate products were characterized using mass spectrometry, IR, and 1H NMR spectroscopic techniques. The amphotericin-B (Amph-B)-loaded and unloaded amphiphiles were screened for biocompatibility studies, vesicle formation, particle shape, size, surface charge, drug entrapment, in-vitro release profile, and stability through atomic force microscopy (AFM), Zetasizer, HPLC, and FT-IR. Amph-B -loaded macrocycle-based niosomal vesicles were investigated for in-vivo bioavailability in rabbits. The synthesized macrocycle exhibited no cytotoxicity against normal mouse fibroblast cells and was found to be hemocompatible and safe in mice following an acute toxicity study. The drug-loaded macrocycle-based vesicles appeared spherical, nano-sized, and homogeneous in size, with a notable negative surface charge. The vesicles remained stable after 30 days of storage. The results of Amph-B oral bioavailability and pharmacokinetics revealed that the newly tailored niosomal formulation enhanced drug solubility, protected drug degradation at gastric pH, facilitated sustained drug release at the specific target site, and delayed plasma drug clearance. Incorporating such advanced niosomal formulations in the field of drug delivery systems has the potential to revolutionize therapeutic outcomes and improve the quality of patient well-being.

Amorphization of Ethenzamide and Ethenzamide Cocrystals-A Case Study of Single and Binary Systems Forming Low-Melting Eutectic Phases Loaded on/in Silica Gel

The applicability of different solvent-free approaches leading to the amorphization of active pharmaceutical ingredients (APIs) was tested. Ethenzamide (ET), an analgesic and anti-inflammatory drug, and two ethenzamide cocrystals with glutaric acid (GLU) and ethyl malonic acid (EMA) as coformers were used as pharmaceutical models. Calcinated and thermally untreated silica gel was applied as an amorphous reagent. Three methods were used to prepare the samples: manual physical mixing, melting, and grinding in a ball mill. The ET:GLU and ET:EMA cocrystals forming low-melting eutectic phases were selected as the best candidates for testing amorphization by thermal treatment. The progress and degree of amorphousness were determined using instrumental techniques: solid-state NMR spectroscopy, powder X-ray diffraction, and differential scanning calorimetry. In each case, the API amorphization was complete and the process was irreversible. A comparative analysis of the dissolution profiles showed that the dissolution kinetics for each sample are significantly different. The nature and mechanism of this distinction are discussed.

Calixarene Functionalized Supramolecular Liquid Crystals and Their Diverse Applications

Liquid crystals are considered to be the fourth state of matter with an intermediate order and fluidity in comparison to solids and liquids. Calixarenes are among one of the most versatile families of building blocks for supramolecular chemistry due to their unique vaselike structure that can be chemically engineered to have different shapes and sizes. During the last few decades, calixarenes have drawn much attention in the field of supramolecular chemistry due to their diverse applications in the fields of ion and molecular recognition, ion-selective electrodes for catalysis, drug delivery, gelation, organic electronics and sensors, etc. Imbuing liquid crystallinity to the calixarene framework leads to functionalized calixarene derivatives with fluidity and order. Columnar self-assembly of such derivatives in particular enhance the charge migration along the column due to the 1D stacking due to the enhanced π-π overlap. Considering limited reports and reviews on this new class of calixarene based liquid crystals, a comprehensive account of the synthesis of calixarene liquid crystals along with their mesomorphic behavior and potential applications are presented in this review.

Advanced Studies on Drug Delivery Systems: Characterization and Their Impact on Pharmaceutical and Medicinal Areas

This work shows some advanced studies in model pharmaceutical formulations that help to develop guidelines for the rational design of controlled release systems [...]