Hyo Na Kim

Bio: Hyo Na Kim is an academic researcher from Gachon University. The author has contributed to research in topics: Vickers hardness test & Mechanochemistry. The author has an hindex of 3, co-authored 4 publications receiving 75 citations. Previous affiliations of Hyo Na Kim include University of Illinois at Urbana–Champaign.

The Effects of Ultrasound on Crystals: Sonocrystallization and Sonofragmentation

Abstract: When ultrasound is applied to a solution for crystallization, it can affect the properties of the crystalline products significantly. Ultrasonic irradiation decreases the induction time and metastable zone and increases the nucleation rate. Due to these effects, it generally yields smaller crystals with a narrower size distribution when compared with conventional crystallizations. Also, ultrasonic irradiation can cause fragmentation of existing crystals which is caused by crystal collisions or sonofragmentation. The effect of various experimental parameters and empirical products of sonocrystallization have been reported, but the mechanisms of sonocrystallization and sonofragmentation have not been confirmed clearly. In this review, we build upon previous studies and highlight the effects of ultrasound on the crystallization of organic molecules. In addition, recent work on sonofragmentation of molecular and ionic crystals is discussed.

Sonofragmentation of Ionic Crystals.

Abstract: Mechanochemistry deals with the interface between the chemical and the mechanical worlds and explores the physical and chemical changes in materials caused by an input of mechanical energy. As such, the chemical and physical effects of ultrasound, i.e., sonochemistry, are forms of mechanochemistry. In this paper, the fragmentation of ionic crystals during ultrasonic irradiation of slurries has been quantitatively investigated: the rate of fragmentation depends strongly on the strength of the materials (as measured by Vickers hardness or by Young's modulus). This is a mechanochemical extension of the Bell–Evans–Polanyi Principle or Hammond's Postulate: activation energies for solid fracture correlate with binding energies of solids. Sonofragmentation is unaffected by slurry loading or liquid vapor pressure, but is suppressed by increasing liquid viscosity. The mechanism of the particle breakage is consistent with a direct interaction between the shockwaves created by the ultrasound (through acoustic cavitation) and the solid particles in the slurry. Fragmentation is proposed to occur from defects in the solids induced by compression–expansion, bending, or torsional distortions of the crystals.

Sonofragmentation of Organic Molecular Crystals vs Strength of Materials.

Abstract: Mechanochemistry, the interface between the chemical and the mechanical worlds, includes the relationship between the chemical and mechanical properties of solids. In this work, fragmentation of organic molecular crystals during ultrasonic irradiation of slurries has been quantitatively investigated. This has particular relevance to nucleation processes during sonocrystallization, which is increasingly used in the processing and formulation of numerous pharmaceutical agents (PAs). We have discovered that the rates of sonofragmentation are very strongly correlated with the strength of the materials (as measured by Vickers hardness and Young's modulus). This is a mechanochemical extension of the Bell-Evans-Polanyi Principle or Hammond's Postulate: the kinetics (i.e., rates) of solid fracture correlate with thermodynamic properties of solids (e.g., Young's modulus). The mechanism of the particle breakage is consistent with a direct interaction between the shockwaves or localized microjets created by the ultrasound (through acoustic cavitation) and the solid particles in the slurry. Comparisons of the sonofragmentation patterns of ionic and molecular crystals showed that ionic crystals are more sensitive to sonofragmentation than molecular crystals for a given Young's modulus. The rates of sonofragmentation are proposed to correlate with the types and densities of imperfections in the crystals.

Ultrasonic method and apparatus for producing particles having a controlled size distribution

Abstract: An ultrasonic apparatus for producing particles of a pharmaceutical agent or other material comprises a flow-through ultrasonic horn comprising an inlet, an outlet, and an interior channel that connects the inlet to the outlet for flow of a fluid therethrough. The ultrasonic horn is connectable to a transducer, and a crystallization tube is adjacent to the ultrasonic horn. The crystallization tube comprises an inlet port and outlet port for flow of an antisolvent therethrough, and it further includes a side access port. The outlet of the ultrasonic horn is inserted into the side access port so as to be in fluid communication with the crystallization tube.

Formulation of More Efficacious Curcumin Delivery Systems Using Colloid Science: Enhanced Solubility, Stability, and Bioavailability

Abstract: Curcumin is a bioactive constituent isolated from turmeric that has historically been used as a seasoning, pigment, and herbal medicine in food. Recently, it has become one of the most commonly studied nutraceuticals in the pharmaceutical, supplement, and food areas because of its myriad of potential health benefits. For instance, it is claimed to exhibit antioxidant, anti-inflammatory, antimicrobial, antiparasite, and anticancer activities when ingested as a drug, supplement, or food. Toxicity studies suggest that it is safe to consume, even at relatively high levels. Its broad-spectrum biological activities and low toxicity have meant that it has been widely explored as a nutraceutical ingredient for application in functional foods. However, there are several hurdles that formulators must overcome when incorporating curcumin into commercial products, such as its low water solubility (especially under acidic and neutral conditions), chemical instability (especially under neutral and alkaline conditions), rapid metabolism by enzymes in the human body, and limited bioavailability. As a result, only a small fraction of ingested curcumin is actually absorbed into the bloodstream. These hurdles can be at least partially overcome by using encapsulation technologies, which involve trapping the curcumin within small particles. Some of the most commonly used edible microparticles or nanoparticles utilized for this purpose are micelles, liposomes, emulsions, solid lipid particles, and biopolymer particles. Each of these encapsulation technologies has its own benefits and limitations for particular product applications and it is important to select the most appropriate one.

The Effects of Ultrasound on Crystals: Sonocrystallization and Sonofragmentation

Abstract: When ultrasound is applied to a solution for crystallization, it can affect the properties of the crystalline products significantly. Ultrasonic irradiation decreases the induction time and metastable zone and increases the nucleation rate. Due to these effects, it generally yields smaller crystals with a narrower size distribution when compared with conventional crystallizations. Also, ultrasonic irradiation can cause fragmentation of existing crystals which is caused by crystal collisions or sonofragmentation. The effect of various experimental parameters and empirical products of sonocrystallization have been reported, but the mechanisms of sonocrystallization and sonofragmentation have not been confirmed clearly. In this review, we build upon previous studies and highlight the effects of ultrasound on the crystallization of organic molecules. In addition, recent work on sonofragmentation of molecular and ionic crystals is discussed.