Low and high frequency ultrasonic techniques offer a green strategy to synthesize multifunctional nanoparticles from small aromatic biological molecules and proteins with tunable size, morphology, and optical and bio-functional properties.

Ultrasonically synthesized core-shell microcapsules can be made of synthetic polymers or natural biopolymers, such as proteins and polysaccharides, and have found applications in food, drug delivery and cosmetics. This study reports on the ultrasonic synthesis of microcapsules using unmodified (natural) and biodegradable glycogen nanoparticles derived from various sources, such as rabbit and bovine liver, oyster and sweet corn, for the encapsulation of soybean oil and vitamin D. Depending on their source, glycogen nanoparticles exhibited differences in size and ‘bound’ proteins. We optimized various synthetic parameters, such as ultrasonic power, time and concentration of glycogens and the oil phase to obtain stable core-shell microcapsules. Particularly, under ultrasound-induced emulsification conditions (sonication time 45 s and sonication power 160 W), native glycogens formed microcapsules with diameter between 0.3 μm and 8 μm. It was found that the size of glycogen as well as the protein component play an important role in stabilizing the Pickering emulsion and the microcapsules shell. This study highlights that native glycogen nanoparticles without any further tedious chemical modification steps can be successfully used for the encapsulation of nutrients.

High-frequency ultrasound treatment is found to be a one-pot green technique to produce peptide-based nanostructures by ultrasound assisted self-assembly of oligopeptides. [Arg-Phe]₄ octapeptides, consisting of alternating arginine (Arg/R) and phenylalanine (Phe/F) sequences, were subjected to 430 kHz ultrasound in aqueous solution in the absence of any external agents, to form [RF]₄ nanoparticles ([RF]₄-NPs), ~220 nm in diameter. A comprehensive analysis of the obtained nanoparticles demonstrated that the aromatic moieties of the oligopeptides can undergo oxidative coupling to form multiple oligomeric species, which then self-assemble into well-defined fluorescent nanoparticles. [RF]₄-NPs were functionalized with polyethylene glycol (PEGylated) to improve their colloidal stability. Unlike the parent peptide, the PEGylated [RF]₄-NPs showed limited cytotoxicity towards MDA-MB-231 cells. Furthermore, the intracellular trafficking of PEGylated [RF]₄-NPs was investigated after incubation with MDA-MB-231 cells to demonstrate their efficient endo-lysosomal escape. This work highlights that the combined use of ultrasonic technologies and peptides enables easy fabrication of nanoparticles, with potential application in drug delivery.

A facile sonochemical method to fabricate magnetic tryptophan-iron oxide nanoparticles for biomedical applications.

Amino acids and peptides are biological molecules that can self-assemble to construct several multifunctional nanostructures with potential applications as biomedical devices. Despite the advantages of self-assembling biomolecules, precise control over the morphology and size of the obtained nanostructures is vital to control their functionality in a biological milieu. Although several techniques have been explored and applied to control the self-assembly phenomenon, they often require salts, metal ions, and organic solvents. Therefore, the development of facile, one-pot, and efficient green synthesis techniques to construct biofunctional nanomaterials is always in high demand. In the current PhD work, we have investigated the application of high-frequency ultrasound to generate multifunctional nanostructures from biomolecules, metals, and oxides. Ultrasound-assisted biofunctional nanoparticles were fabricated from self-assembling oligopeptides with potential bioimaging and drug delivery applications. High-frequency ultrasound also triggered the formation of magnetic tryptophan nanoparticles with interesting optical properties which can be utilized in biosensing applications and as a contrast agent in magnetic resonance imaging. A sonochemical technique was invented to construct 2D gold nanostructures with controlled morphology and excellent catalytic properties.