Facile Preparation of High Strength Silica Aerogel Composites via a Water Solvent System and Ambient Pressure Drying without Surface Modification or Solvent Replacement

To further reduce the manufacturing cost and improve safety, silica aerogel composites (SAC) with low density and low thermal conductivity synthesized via ambient pressure drying (APD) technology have gradually become one of the most focused research areas. As a solvent, ethanol is flammable and needs to be replaced by other low surface tension solvents, which is dangerous and time-consuming. Therefore, the key steps of solvent replacement and surface modification in the APD process need to be simplified. Here, we demonstrate a facile strategy for preparing high strength mullite fiber reinforced SAC, which is synthesized by APD using water as a solvent, rather than using surface modification or solvent replacement. The effects of the fiber density on the physical properties, mechanical properties, and thermal conductivities of SAC are discussed in detail. The results show that when the fiber density of SAC is 0.24 g/cm3, the thermal conductivity at 1100 °C is 0.127 W/m·K, and the compressive strength at 10% strain is 1.348 MPa. Because of the simple synthesis process and excellent thermal-mechanical performance, the SAC is expected to be used as an efficient and economical insulation material.

The Permeability of Poly(lactic-co-glycolic acid) Nanoparticles Loaded with Psoralen to Human Skin in Medical Chemotherapy

Objective: In order to improve the clinical efficacy and reduce the side effects, PLGA nanoparticles loaded with psoralen for external use were prepared, and the permeation, distribution and influencing factors of PLGA nanoparticles delivered via microneedles in human skin were investigated. Methods: The psoralen nanoparticles were prepared by solvent replacement and interfacial polymer deposition. The percutaneous process of PLGA nanoparticles loaded with psoralen was observed with Franz diffusion cell and laser confocal microscope. The distribution of the nanoparticles in each cortex was quantified by HPLC. Results: The retention of PLGA nanoparticles delivered via microneedles in the skin was significantly increased (P < 0.01), and the retention in the epidermis was greater than that in the dermis (P < 0.01); the release rate in vitro was 75.58% after 24 hours, and less than 0.5% after 48 hours. Conclusion: PLGA nanoparticles loaded with psoralen can effectively promote the penetration and distribution of PLGA nanoparticles in human skin after being delivered to human skin through microneedles. With the increase of depth, the amount of PLGA nanoparticles gradually decreases, and with the extension of time, the penetration promotion effect of microneedles is more obvious. PLGA nanoparticles loaded with psoralen may become one of the clinical methods to improve the photochemotherapy of psoralen and develop a new transdermal drug delivery system to reduce its toxic and side effects.

Diffusion of Resveratrol in Silica Alcogels

The trans-resveratrol (RSV)-loaded silica aerogel (RLSA) was prepared by the sol-gel method, adding the drug during the aging process, solvent replacement and freeze drying. A series of characterizations showed that RSV stays in the silica aerogel in two ways. First, RSV precipitates due to minimal solubility in water during the solvent replacement process. After freeze drying, the solvent evaporates and the RSV recrystallizes. It can be seen from scanning electron microscope (SEM) and transmission electron microscope (TEM) images that the recrystallized RSV with micron-sized long rod-shaped is integrated with the dense silica network skeleton. Second, from small-angle X-ray scattering (SAXS) results, a portion of the RSV molecules is not crystallized and the size is extremely small. This can be attached to the primary and secondary particles of silica to enhance its network structure and inhibit shrinkage, which is why the volume and pore size of RLSA is larger. In addition, the diffusion of RSV in silica alcogel was studied by a one-dimensional model. The apparent diffusion coefficients of inward diffusion, outward diffusion and internal diffusion were calculated by fitting the time- and position-dependent concentration data. It was found that the outward diffusion coefficient (5.25 × 10−10 m2/s) is larger than the inward (2.93 × 10−10 m2/s), which is probably due to the interface effect. The diffusion coefficients obtained for different concentrations in the same process (inward diffusion) are found to be different. This suggests that the apparent diffusion coefficient obtained is affected by molecular adsorption.

Amylase-Sensitive Polymeric Nanoparticles Based on Dextran Sulfate and Doxorubicin with Anticoagulant Activity

This study looked into the synthesis and study of Dextrane Sulfate–Doxorubicin Nanoparticles (DS–Dox NP) that are sensitive to amylase and show anticoagulant properties. The particles were obtained by the method of solvent replacement. They had a size of 305 ± 58 nm, with a mass ratio of DS:Dox = 3.3:1. On heating to 37 °C, the release of Dox from the particles was equal to 24.2% of the drug contained. In the presence of amylase, this ratio had increased to 42.1%. The study of the biological activity of the particles included an assessment of the cytotoxicity and the effect on hemostasis and antitumor activity. In a study of cytotoxicity on the L929 cell culture, it was found that the synthesized particles had less toxicity, compared to free doxorubicin. However, in the presence of amylase, their cytotoxicity was higher than the traditional forms of the drug. In a study of the effect of DS–Dox NP on hemostasis, it was found that the particles had a heparin-like anticoagulant effect. Antitumor activity was studied on the model of ascitic Zaidel hepatoma in rats. The frequency of complete cure in animals treated with the DS–Dox nanoparticles was higher, compared to animals receiving the traditional form of the drug.

Spray dried proliposomes of Rosmarinus officinalis polyphenols: a quality by design approach

Harnessing the benefits of rosemary polyphenols is limited by variability in their physicochemical properties. These limitations may be overcome by encapsulation in systems possessing hydro-lipophilic centers thereby accommodating molecules of different polarities. Proliposomes offer a viable option in this regards, being particles which form liposomal suspension in water. Lyophilized extracts of rosemary was encapsulated in hydrogenatedsoyphosphatidylcholine/cholesterol by solvent replacement method. Spray dried proliposomes were obtained with lactose as carrier. Using Central Composite Design, the effects of lipid, extract and carrier concentrations on response variables including bioactive content and retention, moisture content characteristics, recuperation and redispersibility were evaluated by statistical analysis. Keywords: Polyphenols; antioxidant; proliposomes; spray drying