Ultrasound-assisted solution crystallization of fotagliptin benzoate: Process intensification and crystal product optimization

Potential of High-Intensity Focused Ultrasound in Enamel Remineralization

Remineralization is an essential interventional strategy for intercepting enamel white spot lesions (WSLs). Given the limitations of both natural and/or fluoride-mediated repair processes, there is a need to develop novel strategies for repairing enamel WSLs via a minimally invasive approach while restoring the unique ultrastructural integrity and functional properties. Inspired by the unique capability of high-intensity focused ultrasound (HIFU) in facilitating the crystallization process, we propose a novel strategy of employing HIFU for in vitro repair of WSLs through synergizing the crystallization process required for hydroxyapatite (HAP) formation from its precursor (calcium phosphate ion clusters; CPICs). Following CPIC formulation and characterization including the resultant amorphous calcium phosphate (ACP), the effect of HIFU on the ACP-to-HAP transition on the amorphous substrate was investigated using transmission electron microscopy and high-resolution transmission electron microscopy, selected area electron diffraction, and X-ray diffraction (XRD). The results showed profound amorphous-to-crystalline phase transition, within 5- to 30-min HIFU exposure, whereas the long axis of the resultant HAP corresponded with the (002) plane, and a lattice spacing of 0.34 nm indicated a preferred c-axis growth direction consistent with the orientation of natural enamel crystallites. For enamel repair, artificial WSLs were created on enamel specimens and then subjected to CPICs, followed by HIFU exposure for 2.5, 5, or 10 min. Scanning electron and atomic force microscopies revealed the decreased surface roughness and the gradual obliteration in the WSL porous structure with continuous linear coaxial arrangement of HAP crystallites filling the prismatic/interprismatic gaps closely resembling sound enamel specifically with 5-min HIFU exposure. Enamel WSL ultrastructural repair was further confirmed from XRD and Raman spectral analyses with the associated regaining of mineral density and nanomechanical properties as reflected from micro-computed tomography (CT) and nanoindentation results, respectively. Micro-CT further validated the subsurface remineralization of WSLs with HIFU exposure. Within the same exposure parameters, HIFU exhibited a potent antibiofilm effect against Streptococcus mutans. This study introduced a new approach for remineralizing enamel WSLs through the potent synergy between HIFU and CPICs.

Application of ultrasonic-enhanced active seed crystals in the removal of sodium oxalate from alumina refinery waste liquor

When organic matter, especially sodium oxalate (Na2C2O4), accumulates to a certain extent, it will seriously affect the alumina production process in the refinery and therefore urgently needs to be removed. This work attempts to illuminate the benefits of ultrasonic intensification of the crystallization process of Na2C2O4, taking the alumina refinery waste liquor, i.e., flat plate washing liquor, as a case study. The effects of different operating parameters (seed crystal addition amount, caustic soda concentration, reaction time, ultrasonic power) on the crystallization behavior and yield are discussed, and it is found that ultrasonic can increase the Na2C2O4 removal rate to 70.4%. The addition of ultrasonic promotes the morphological evolution of Na2C2O4 and is of great significance to the optimization of the components of the precipitated Na2C2O4. Specifically, the proportion of Na2C2O4 in the crystallized product reaches 64% with conventional conditions, while it reaches 77% with ultrasonic conditions. Therefore, ultrasonic can greatly reduce the alkali loss caused by the crystallization process of Na2C2O4 in flat plate washing liquor, which has great economic benefits.

Controlling the Architecture of Freeze-Dried Collagen Scaffolds with Ultrasound-Induced Nucleation

Collagen is a naturally occurring polymer that can be freeze-dried to create 3D porous scaffold architectures for potential application in tissue engineering. The process comprises the freezing of water in an aqueous slurry followed by sublimation of the ice via a pre-determined temperature-pressure regime and these parameters determine the arrangement, shape and size of the ice crystals. However, ice nucleation is a stochastic process, and this has significant and inherent limitations on the ability to control scaffold structures both within and between the fabrication batches. In this paper, we demonstrate that it is possible to overcome the disadvantages of the stochastic process via the use of low-frequency ultrasound (40 kHz) to trigger nucleation, on-demand, in type I insoluble bovine collagen slurries. The application of ultrasound was found to define the nucleation temperature of collagen slurries, precisely tailoring the pore architecture and providing important new structural and mechanistic insights. The parameter space includes reduction in average pore size and narrowing of pore size distributions while maintaining the percolation diameter. A set of core principles are identified that highlight the huge potential of ultrasound to finely tune the scaffold architecture and revolutionise the reproducibility of the scaffold fabrication protocol.

Polymer-mediated and ultrasound-assisted crystallization of ropivacaine: Crystal growth and morphology modulation

The objective of this research was to modify the crystal shape and size of poorly water-soluble drug ropivacaine, and to reveal the effects of polymeric additive and ultrasound on crystal nucleation and growth. Ropivacaine often grow as needle-like crystals extended along the a-axis and the shape was hardly controllable by altering solvent types and operating conditions for the crystallization process. We found that ropivacaine crystallized as block-like crystals when polyvinylpyrrolidone (PVP) was used. The control over crystal morphology by the additive was related to crystallization temperature, solute concentration, additive concentration, and molecular weight. SEM and AFM analyses were performed providing insights into crystal growth pattern and cavities on the surface induced by the polymeric additive. In ultrasound-assisted crystallization, the impacts of ultrasonic time, ultrasonic power, and additive concentration were investigated. The particles precipitated at extended ultrasonic time exhibited plate-like crystals with shorter aspect ratio. Combined use of polymeric additive and ultrasound led to rice-shaped crystals, which the average particle size was further decreased. The induction time measurement and single crystal growth experiments were carried out. The results suggested that PVP worked as strong nucleation and growth inhibitor. Molecular dynamics simulation was performed to explore the action mechanism of the polymer. The interaction energies between PVP and crystal faces were calculated, and mobility of the additive with different chain length in crystal-solution system was evaluated by mean square displacement. Based on the study, a possible mechanism for the morphological evolution of ropivacaine crystals assisted by PVP and ultrasound was proposed.

Sustainable emerging high-intensity sonication processing to enhance the protein bioactivity and bioavailability: An updated review

High-intensity ultrasound (HIU) is considered one of the promising non-chemical eco-friendly techniques used in food processing. Recently (HIU) is known to enhance food quality, extraction of bioactive compounds and formulation of emulsions. Various foods are treated with ultrasound, including fats, bioactive compounds, and proteins. Regarding proteins, HIU induces acoustic cavitation and bubble formation, causing the unfolding and exposure of hydrophobic regions, resulting in functional, bioactive, and structural enhancement. This review briefly portrays the impact of HIU on the bioavailability and bioactive properties of proteins; the effect of HIU on protein allergenicity and anti-nutritional factors has also been discussed. HIU can enhance bioavailability and bioactive attributes in plants and animal-based proteins, such as antioxidant activity, antimicrobial activity, and peptide release. Moreover, numerous studies revealed that HIU treatment could enhance functional properties, increase the release of short-chain peptides, and decrease allergenicity. HIU could replace the chemical and heat treatments used to enhance protein bioactivity and digestibility; however, its applications are still on research and small scale, and its usage in industries is yet to be implemented.