1,721,227 research outputs found
Modification of the Size Distribution of Lysozyme Microbubbles Using a Post-Sonication Technique
No full textThe control of the physical and functional properties of ultrasound responsive microbubbles is of interest because of their potential applications in therapeutic and diagnostic medicine. Crosslinked lysozyme microbubbles, synthesized using high intensity low frequency (20 kHz) ultrasound, possess long-term stability and retain bactericidal property. However, the relatively broader size distribution of these microbubbles may limit their use in some applications. In this article, we introduce a post-sonication technique for modifying the size distribution of lysozyme microbubbles. The post-sonication of these microbubbles at very high ultrasound frequencies (213, 355, 647, and 1056 kHz) led to the selective destruction of microbubbles of certain size range, leading to changes in the size distribution of microbubbles. An increase in acoustic power (10 W-60 W) at a fixed frequency (1056 kHz) resulted in a relatively narrow size distribution of the microbubbles. Although the enzymatic activity of microbubbles was reduced by the post-sonication treatment, significant activity was still preserved
Ultrasound-Assisted Synthesis of Cross-Linked Poly(ethylene glycol) Nanostructures with Hydrophobic Core and Hydrophilic Shell
No full textTailoring the properties of ultrasonically synthesised microbubbles
No full textAir-filled lysozyme microbubbles can be synthesized in an aqueous medium by emulsification followed by the cross-linking of protein molecules under high-intensity ultrasound. Here, we report on the tailoring of the properties of the ultrasonically synthesised microbubbles using new procedures. The efficiency of formation, size, size distribution and morphology of the microbubbles were controlled by manipulating the experimental conditions, namely, the sonication power and the length of sonication. An increase in the sonication time and power led to the formation of larger microbubbles with a broader size distribution. The microbubble shell thickness was found to decrease with an increase in the sonication power and time. Furthermore, a pulsed sonoluminescence technique was used to study the strength and stability of the microbubbles. The experimental results have shown that the effects of sonication time and power on the properties of the microbubbles are quite complex. A simple graphical matrix has been derived to obtain stable microbubbles with a narrow size distribution
The Design of Multifunctional Microbubbles for Ultrasound Image-Guided Cancer Therapy
No full textGas-filled microbubbles are widely used in diagnostic imaging. Recent developments have greatly enhanced the potential use of microbubbles for both diagnostic and therapeutic applications. For the potential use of microbubbles in therapeutic applications, the chemical nature of the shell and its mechanical properties are crucial, and require a tailored synthetic approach. This review describes methods of preparation, mechanism of action, in vitro and in vivo stability and structural/functional characterization of microbubbles. New mechanisms for ultrasound-enhanced local drug and gene delivery are reviewed. Different strategies used to target microbubbles to regions of disease and some of the recent experiences in ultrasound image-guided therapy are also discussed
Ultrasound-assisted preparation of nanopolymeric and micropolymeric materials for the encapsulation of bioactive agents
No full textRole of Counterions in Controlling the Properties of Ultrasonically Generated Chitosan-Stabilized Oil-in-Water Emulsions
No full textAn oil-in-water emulsion was ultrasonically prepared in aqueous chitosan solutions containing different counterions. Tetradecane was used as the oil phase in order to mimic nonpolar substances used in food processes. Various acids were used to dissolve chitosan, and we found that conjugate bases of the acids used, which act as counterions to neutralize the positive charges of ammonium ions present in the chitosan backbone, played a significant role in controlling the size, size distribution, and stability of chitosan-encapsulated tedradecane emulsion droplets (microspheres). The counterion effect is also found to be strongly dependent upon tetradecane (TD)/chitosan (CS) ratio and ultrasonic power. Key observations are: (i) for a given TD/CS ratio, the size and size distribution decrease when the acid is varied from nitric acid to benzenesulfonic acid at high TD/CS ratio, and the effect becomes less significant at low TD/CS ratio; (ii) for a given acid, the size and size distribution increase with an increase in TD/CS ratio; and (iii) at low TD/CS ratio the size and size distribution are significantly influenced by the viscosity of the system. A possible mechanism for the observed counterion effect is proposed. The role of counterions, solution viscosity, and ultrasonic power in controlling the physical and functional properties of ultrasonically generated chitosan-stabilized tetradecane microspheres is discussed in detail. The key new finding of this study is that it is possible to form stable emulsions without the addition of external emulsifiers and stabilizers, but only using chitosan with different acids to dissolve chitosan. This strategy could be used in the generation of stable food emulsions
Ultrasonic microencapsulation of oil-soluble vitamins by hen egg white and green tea for fortification of food
Full text linkWe report the microencapsulation of oil soluble vitamins (A, D and E) using a one pot ultrasonic process and raw egg white proteins as a shell material. Green tea catechin/iron complex coating method was further developed to impart UV filtering property to the microcapsules in order to protect the encapsulated nutrients from photodegradation. The microcapsules showed antibacterial properties and long shelf-life. The encapsulated vitamins were protected from degradation upon heating, UV irradiation, simulated storage/transit and cooking processes. The in-vitro digestion study showed that functional vitamin D can be potentially released in the gastrointestinal tract improving vitamin D availability by more than 2-fold compared to the free vitamin. The vitamin D microcapsules were highly stable and maintained their microstructures once incorporated into staple food products. The low-cost egg white shell encapsulated vitamins can improve the nutritional value of staple food products to combat maternal and child malnutrition
One-pot ultrasonic synthesis of multifunctional microbubbles and microcapsules using synthetic thiolated macromolecules
No full textA one-pot ultrasonic procedure has been developed as a versatile route for synthesizing polymer-coated microspheres that have potential application as drug delivery vehicles. The use of synthetic thiolated poly(methacrylic acid) macromolecules as the shell material offers control over size, morphology and functionality of the microspheres
Methods of preparation of multifunctional microbubbles and their in vitro / in vivo assessment of stability, functional and structural properties
No full textMicrobubbles (MBs) are ultrasound responsive colloidal particles with a strong potential to become theranostic agents, combining the contrast agent activity with therapeutic functionality. In the last decades, MBs have played a significant role as ultrasound contrast agents in diagnostic imaging. MBs have also shown great potential in applications such as molecular imaging, drug delivery, gene therapy and sonothrombolysis. A full understanding of all physical processes underlying the MBs' stability and acoustic behavior is available in the literature. Efforts have been now addressed to the study of chemical and biological features of multifunctional lipid, protein, or polymer shelled MBs. A number of methods of preparation of "smart" MBs for ultrasound image-guided therapy have been recently developed. In this review, different approaches utilized in preparing multifunctional MBs are discussed with specific attention to the current strategies adopted to design MBs with specialized functions. In vitro / in vivo assessment of MBs' stability and activity will be discussed with a particular emphasis on the emerging applications of MBs for the multiple imaging modalities, the effective opening of blood brain barrier, BBB, and for the therapeutic treatment of antimicrobial films
Synthesis of gold nanosheets with controlled morphology by combining a natural amino acid with high-frequency ultrasound
No full textIn this study, we report on the formation of gold nanosheets with different morphologies using a naturally occurring amino acid, viz, tryptophan, as a reducing and capping agent at ambient conditions. The importance of in situ-oxidized tryptophan for promoting anisotropic growth of gold (Au) nuclei to form two-dimensional gold nanosheets is demonstrated. Furthermore, we investigated the effect of high frequency ultrasound (490 kHz) and tryptophan to fabricate ultrathin gold nanosheets with controlled morphologies (triangular and polygonal shapes), without using any other reagents/stabilizers. The size of gold sheets (200 nm to micrometer range) can be controlled by tuning the experimental conditions. A possible mechanism for the formation of well-defined gold nanostructures with different morphologies is provided. High frequency sonication leads to the simultaneous dimerization of tryptophan and Au reduction, and we show that the interaction of tryptophan dimers with Au nuclei plays an important role in the formation of gold sheets. The sonochemically synthesized AuNSs displayed superior catalytic activity in the reduction of 4-nitrophenol to 4-aminophenol with a specific rate constant of 1.96 x 10(3) s(-1) per unit gram of active catalyst and with excellent recyclability
- …
