Temperature is key to yield and stability of BSA stabilized microbubbles

Assembly of Metal-Phenolic Networks onto Microbubbles for One-Step Generation of Functional Microcapsules

The one-step assembly of metal-phenolic networks (MPNs) onto particle templates can enable the facile, rapid, and robust construction of hollow microcapsules. However, the required template removal step may affect the refilling of functional species in the hollow interior space or the in situ encapsulation of guest molecules during the formation of the shells. Herein, a simple strategy for the one-step generation of functional MPNs microcapsules is proposed. This method uses bovine serum albumin microbubbles (BSA MBs) as soft templates and carriers, enabling the efficient pre-encapsulation of guest species by leveraging the coordination assembly of tannic acid (TA) and FeIII ions. The addition of TA and FeIII induces a change in the protein conformation of BSA MBs and produces semipermeable capsule shells, which allow gas to escape from the MBs without template removal. The MBs-templated strategy can produce highly biocompatible capsules with controllable structure and size, and it is applicable to produce other MPNs systems like BSA-TA-CuII and BSA-TA-NiII . Finally, those MBs-templated MPNs capsules can be further functionalized or modified for the loading of magnetic nanoparticles and the pre-encapsulation of model molecules through covalence or physical adsorption, exhibiting great promise in biomedical applications.

Preparation, Multispectroscopic Characterization, and Stability Analysis of Monascus Red Pigments-Whey Protein Isolate Complex

Monascus red pigments (MRPs) are mainly used as natural food colorants; however, their application is limited due to their poor stability. To expand their areas of application, we investigated the binding constants and capacity of MRPs to whey protein isolate (WPI) and whey protein hydrolysate (WPH) and calculated the surface hydrophobicities of WPI and WPH. MRPs were combined with WPI and WPH at a hydrolysis degree (DH) of 0.5% to form the complexes (DH = 0.0%) and (DH = 0.5%), respectively. Subsequently, the structural characteristics of complex (DH = 0.5%) and WPI were characterized and the color retention rates of both complexes and MRPs were investigated under different pretreatment conditions. The results showed that the maximum binding constant of WPI with MRPs was 0.670 ± 0.06 U-1 and the maximum binding capacity was 180 U/g. Furthermore, the thermal degradation of complex (DH = 0.0%), complex (DH = 0.5%), and MRPs in a water bath at 50-100 °C followed a first-order kinetic model. Thus, the interaction of WPI with MRPs could alter the protein conformation of WPI and effectively protect the stability of MRPs.

Hybrid (Bovine Serum Albumin)/Poly(N-vinyl-2-pyrrolidone-co-acrylic acid)-Shelled Microbubbles as Advanced Ultrasound Contrast Agents

Microbubbles are routinely used ultrasound contrast agents in the clinic. While a soft protein shell is commercially preferable for imaging purposes, a rigid polymer shell demonstrates prolonged agent stability. Hence, combining polymers and proteins in one shell composition can advance microbubble properties. We formulated the hybrid "protein-copolymer" microbubble shell with a complex of bovine serum albumin and an amphiphilic copolymer of N-vinyl-2-pyrrolidone and acrylic acid. The resulting microbubbles demonstrated advanced physicochemical and acoustic properties, preserving in vitro biocompatibility. Adjusting the mass ratio between protein and copolymer allowed fine tuning of the microbubble properties of concentration (by two orders, up to 10¹⁰ MBs/mL), mean size (from 0.8 to 5 μm), and shell thickness (from 28 to 50 nm). In addition, the minimum air-liquid surface tension for the "protein-copolymer" solution enabled the highest bubble concentration. At the same time, a higher copolymer amount in the bubble shell increased the bubble size and tuned duration and intensity of the contrast during an ultrasound procedure. Demonstrated results exemplify the potential of the hybrid "protein-polymer" microbubble shell, allowing tailoring of microbubble properties for image-guided applications, combining advances of each material involved in the formulation.

Update of ultrasound-assembling fabrication and biomedical applications for heterogeneous polymer composites

As a power-driving approach, ultrasound irradiation is very appealing to the preparation or modification of new materials. In the review, we overviewed the latest development of ultrasound-mediated effects or reactions in polymer composites, and demonstrated its unique and powerful aspects on the polymerization or aggregation. The review generalized the different categories of heterogeneous polymer composites by defining the constituents, and described the shapes, sizes and basic properties of various purpose-specific or site-specific products. Importantly, the review paid more attention to the main biomedicine applications of heterogeneous polymer composites, such as drug or bioactive substance entrapment, delivery, release, imaging, and therapy, and emphasized many advantages of ultrasound-assembling approaches and heterogeneous polymer composites in biology and medicine fields. In addition, the review also indicated the prospective challenges of heterogeneous polymer composites both in ultrasound-assembling designs and in biomedical applications.

Microbubbles Stabilized by Protein Shell: From Pioneering Ultrasound Contrast Agents to Advanced Theranostic Systems

Ultrasound is a widely-used imaging modality in clinics as a low-cost, non-invasive, non-radiative procedure allowing therapists faster decision-making. Microbubbles have been used as ultrasound contrast agents for decades, while recent attention has been attracted to consider them as stimuli-responsive drug delivery systems. Pioneering microbubbles were Albunex with a protein shell composed of human serum albumin, which entered clinical practice in 1993. However, current research expanded the set of proteins for a microbubble shell beyond albumin and applications of protein microbubbles beyond ultrasound imaging. Hence, this review summarizes all-known protein microbubbles over decades with a critical evaluation of formulations and applications to optimize the safety (low toxicity and high biocompatibility) as well as imaging efficiency. We provide a comprehensive overview of (1) proteins involved in microbubble formulation, (2) peculiarities of preparation of protein stabilized microbubbles with consideration of large-scale production, (3) key chemical factors of stabilization and functionalization of protein-shelled microbubbles, and (4) biomedical applications beyond ultrasound imaging (multimodal imaging, drug/gene delivery with attention to anticancer treatment, antibacterial activity, biosensing). Presented critical evaluation of the current state-of-the-art for protein microbubbles should focus the field on relevant strategies in microbubble formulation and application for short-term clinical translation. Thus, a protein bubble-based platform is very perspective for theranostic application in clinics.

Self-Healing Behavior of Polymer/Protein Hybrid Hydrogels

The paper presents the viscoelastic properties of new hybrid hydrogels containing poly(vinyl alcohol) (PVA), hydroxypropylcellulose (HPC), bovine serum albumin (BSA) and reduced glutathione (GSH). After heating the mixture at 55 °C, in the presence of GSH, a weak network is formed due to partial BSA unfolding. By applying three successive freezing/thawing cycles, a stable porous network structure with elastic properties is designed, as evidenced by SEM and rheology. The hydrogels exhibit self-healing properties when the samples are cut into two pieces; the intermolecular interactions are reestablished in time and therefore the fragments repair themselves. The effects of the BSA content, loaded deformation and temperature on the self-healing ability of hydrogels are presented and discussed through rheological data. Due to their versatile viscoelastic behavior, the properties of PVA/HPC/BSA hydrogels can be tuned during their preparation in order to achieve suitable biomaterials for targeted applications.

Air-Filled Microbubbles Based on Albumin Functionalized with Gold Nanocages and Zinc Phthalocyanine for Multimodal Imaging

Microbubbles are intravascular contrast agents clinically used in diagnostic sonography, echocardiography, and radiology imaging applications. However, up to date, the idea of creating microbubbles with multiple functionalities (e.g., multimodal imaging, photodynamic therapy) remained a challenge. One possible solution is the modification of bubble shells by introducing specific compounds responsible for such functions. In the present work, air-core microbubbles with the shell consisting of bovine serum albumin, albumin-coated gold nanocages, and zinc phthalocyanine were prepared using the sonication method. Various physicochemical parameters such as stability over time, size, and concentration were investigated to prove the potential use of these microbubbles as contrast agents. This work shows that hybrid microbubbles have all the necessary properties for multimodal imaging (ultrasound, raster-scanning microscopy, and fluorescence tomography), which demonstrate superior characteristics for potential theranostic and related biomedical applications.

Improving carvacrol bioaccessibility using core-shell carrier-systems under simulated gastrointestinal digestion

The impact of encapsulating carvacrol in chitosan-albumin based core-shell nano-carriers (NCs) on its stability and bioaccessibility was determined under simulated digestion conditions. These NCs consisted of chitosan (C) core enclosed by bovine serum albumin (BSA) shell. The mean particle size ranged from 52.4 ± 10 nm to 203 ± 6 nm and zeta-potential from + 21 ± 3.6 to -18 ± 2.7 mV. The size and charge were significantly modified after the protein-shell formation around the polysaccharide-core. Core-shell NCs were more stable, with less aggregation under simulated gastrointestinal conditions than C-NCs, presumably due to greater steric repulsion. Likewise, core-shell NCs were observed relatively more stabilized in the intestinal phase than gastric phase. The bioaccessibility of carvacrol was enhanced significantly when it was encapsulated in the core-shell NCs. These findings imply that C-BSA based core-shell NCs might be an efficient means of encapsulating, protecting and delivering hydrophobic bioactive compounds for applications in functional foods.

Air-Filled Bubbles Stabilized by Gold Nanoparticle/Photodynamic Dye Hybrid Structures for Theranostics

Microbubbles have already reached clinical practice as ultrasound contrast agents for angiography. However, modification of the bubbles’ shell is needed to produce probes for ultrasound and multimodal (fluorescence/photoacoustic) imaging methods in combination with theranostics (diagnostics and therapeutics). In the present work, hybrid structures based on microbubbles with an air core and a shell composed of bovine serum albumin, albumin-coated gold nanoparticles, and clinically available photodynamic dyes (zinc phthalocyanine, indocyanine green) were shown to achieve multimodal imaging for potential applications in photodynamic therapy. Microbubbles with an average size of 1.5 ± 0.3 μm and concentration up to 1.2 × 10⁹ microbubbles/mL were obtained and characterized. The introduction of the dye into the system reduced the solution’s surface tension, leading to an increase in the concentration and stability of bubbles. The combination of gold nanoparticles and photodynamic dyes’ influence on the fluorescent signal and probes’ stability is described. The potential use of the obtained probes in biomedical applications was evaluated using fluorescence tomography, raster-scanning optoacoustic microscopy and ultrasound response measurements using a medical ultrasound device at the frequency of 33 MHz. The results demonstrate the impact of microbubbles’ stabilization using gold nanoparticle/photodynamic dye hybrid structures to achieve probe applications in theranostics.

Critical Role of a Nanometer-Scale Microballoon Shell on Bulk Acoustic Properties of Doped Soft Matter

A material's acoustic properties depend critically upon porosity. Doping a soft material with gas-filled microballoons permits a controlled variation of the porosity through a scalable fabrication process while generating well-tailored spherical cavities that are impermeable to liquids. However, evidence is lacking of how the nanometer-scale polymeric shell contributes to the overall effective material properties in the regime where the wavelength is comparable to the sample thickness. Here, we measure ultrasound transmission through a microballoon-doped soft material as a function of microballoon and impurity concentration, sample thickness, and frequency. The measured longitudinal wave speeds are an order of magnitude larger than those in similar systems where no shell is present, while the transverse wave speed is found to linearly increase with microballoon concentration, also in contrast to systems with no shell. Furthermore, we find the results are independent of the soft material's elastic moduli as well as a lesser contribution of the microballoon shell on material attenuation. The results are validated with a multiple scattering model and suggest the shell contributes significantly to the material's bulk acoustic properties despite its thickness being 4 orders of magnitude smaller than the acoustic wavelength. Our results demonstrate how a nanometer-scale interface between a gas cavity and a soft polymer can be used in the submicrometer design of acoustic materials, and are important for observations of such phenomena as strong interference effects in soft matter.

Perception of creaminess in foods

Food texture and mouthfeel play a crucial role in product and consumer acceptability. Creaminess, enjoyed by consumers, is a complex, multimodal sensory perception involving olfactory, gustatory and tactile cues. Oral viscosity and lubrication are the key underlying physical properties that define the mechanism of creaminess perception. Thickness, smoothness, mouth-coating, and dairy flavor can together play roles in the sensation of creaminess. The aim of this review is to present an understanding of the term" creaminess" along with different modalities involved in its perception, and to explore the oral physiological parameters and key physical properties that may be involved in the different oral modalities. An analysis of the previously examined links between food structure and composition and oral physiological parameters is presented. The review also presents a brief summary of previous models describing contributions of taste, aroma, and textural sensations. It emphasizes on the role of oral processing in testing proposed models with experimental evidence supporting those models and the future trends to enhance creaminess.

Recent advances in micro- and nano-bubbles for atherosclerosis applications

Micro- and nano-bubbles have been developed as powerful multimodal theranostic agents for atherosclerosis treatment.

Biocompatible Chitosan Nanobubbles for Ultrasound-Mediated Targeted Delivery of Doxorubicin

Ultrasound-targeted delivery of nanobubbles (NBs) has become a promising strategy for noninvasive drug delivery. The biosafety and drug-transporting ability of NBs have been a research hotspot, especially regarding chitosan NBs due to their biocompatibility and high biosafety. Since the drug-carrying capacity of chitosan NBs and the performance of ultrasound-assisted drug delivery remain unclear, the aim of this study was to synthesize doxorubicin hydrochloride (DOX)-loaded biocompatible chitosan NBs and assess their drug delivery capacity. In this study, the size distribution of chitosan NBs was measured by dynamic light scattering, while their drug-loading capacity and ultrasound-mediated DOX release were determined by a UV spectrophotometer. In addition, a clinical ultrasound imaging system was used to evaluate the ability of chitosan NBs to achieve imaging enhancement, while the biosafety profile of free chitosan NBs was evaluated by a cytotoxicity assay in MCF-7 cells. Furthermore, NB-mediated DOX uptake and the apoptosis of Michigan Cancer Foundation-7 (MCF-7) cells were measured by flow cytometry. The results showed that the DOX-loaded NBs (DOX-NBs) exhibited excellent drug-loading ability as well as the ability to achieve ultrasound enhancement. Ultrasound (US) irradiation promoted the release of DOX from DOX-NBs in vitro. Furthermore, DOX-NBs effectively delivered DOX into mammalian cancer cells. In conclusion, biocompatible chitosan NBs are suitable for ultrasound-targeted DOX delivery and are thus a promising strategy for noninvasive and targeted drug delivery worthy of further investigation.

Sonochemistry-Assembled Stimuli-Responsive Polymer Microcapsules for Drug Delivery

Stimuli-responsive polymer microcapsules (PMs) fabricated by the sonochemical method have emerged for developing useful drug delivery systems, and the latest developments are mainly focusing on the synthetic strategies and properties such as structure, size, stability, loading capacity, drug delivery, and release. There, the primary attribution of sonochemistry is to offer a simple and practical approach for the preparation of PMs. Structure, size, stability, and properties of PMs are designed mainly according to synthetic materials, implementation schemes, or specific demands. Numerous functionalities of PMs based on different stimuli are demonstrated: targeting motion in a magnetic field or adhering to the living cells with sensitive sites through molecular recognition, and stimuli-triggered release including enzymatic catalysis, chemical reaction as well as physical or mechanical process. The current review discusses the basic principles and mechanisms of stimuli effects, and describes the progress in the application such as targeted drug systems and controlled drug systems, and also gives an outlook on the future challenges and opportunities for drug delivery and theranostics.

A facile sonochemical synthesis of shell-stabilized reactive microbubbles using surface-thiolated bovine serum albumin with the Traut's reagent

The short lifetime of proteinaceous microbubbles produced using conventional sonication method has hindered their applications in drug delivery and metal removal from wastewater. In this study, we aimed to synthesize stable proteinaceous microbubbles and to demonstrate their reactivity. Our model protein, bovine serum albumin (BSA) was treated with 2-iminothiolane hydrochloride (Traut's reagent) to convert primary amines to thiols before the synthesis of microbubbles. Microbubbles produced with the Traut's reagent-treated BSA (BSA-SH MBs) were initially concentrated at median sizes of 0.5 and 2.5μm. The 0.5μm portion quickly vanished, and the 2.5μm portion gradually shrank to ∼850nm in ∼3days and became stabilized afterward for several months under 4°C. Characterizations of BSA-SH MBs by Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) indicated the presence of free unbound thiols and primary amines on their surface, implying the possibility of further surface modification. Based on the zeta potential measurement, the isoelectric point (IEP) of BSA-SH MBs was determined to be 4.5. The attachments of BSA-SH MBs on alumina, silica, and gold surfaces in different pH environments were carried out with a quartz crystal microbalance with dissipation monitoring (QCM-D), demonstrating the reactivities of BSA-SH MBs. At pH 6, the negatively charged BSA-SH MBs were adsorbed onto the alumina surface by electrostatic interaction. Analogously, at pH 4, the adsorption of the positively charged BSA-SH MBs on the silica surface was confirmed. Compared with the electrostatic interaction, the adsorption of BSA-SH MBs on the gold surface is attributed to the strong gold-thiol bonding effect. This is the first time that a universal approach for stabilizing protein-shelled microbubbles was reported using only one single step of surface treatment of proteins with the Traut's reagent.

Nanobubbles: a promising efficienft tool for therapeutic delivery

In recent decades ultrasound-guided delivery of drugs loaded on nanocarriers has been the focus of increasing attention to improve therapeutic treatments. Ultrasound has often been used in combination with microbubbles, micron-sized spherical gas-filled structures stabilized by a shell, to amplify the biophysical effects of the ultrasonic field. Nanometer size bubbles are defined nanobubbles. They were designed to obtain more efficient drug delivery systems. Indeed, their small sizes allow extravasation from blood vessels into surrounding tissues and ultrasound-targeted site-specific release with minimal invasiveness. Additionally, nanobubbles might be endowed with improved stability and longer residence time in systemic circulation. This review will describe the physico-chemical properties of nanobubbles, the formulation parameters and the drug loading approaches, besides potential applications as a therapeutic tool.

Effect of Temperature and Pressure on the Stability of Protein Microbubbles

Protein microbubbles are air bubbles with a network of interacting proteins at the air-water interface. Protein microbubbles are commonly used in medical diagnostic and therapeutic research. They have also recently gained interest in the research area of food as they can be used as structural elements to control texture, allowing for the manufacture of healthier foods with increased consumer perception. For the application of microbubbles in the food industry, it is important to gain insights into their stability under food processing conditions. In this study, we tested the stability of protein microbubbles against heating and pressurization. Microbubbles could be heated to 50 °C for 2 min or pressurized to 100 kPa overpressure for 15 s without significantly affecting their stability. At higher pressures and temperatures, the microbubbles became unstable and buckled. Buckling was observed above a critical pressure and was influenced by the shell modulus. The addition of cross-linkers like glutaraldehyde and tannic acid resulted in microbubbles that were stable against all tested temperatures and overpressures, more specifically, up to 120 °C and 470 kPa, respectively. We found a relation between the storage temperatures of microbubble dispersions (4, 10, 15, and 21 °C) and a decrease in the number of microbubbles with the highest decrease at the highest storage temperature. The average rupture time of microbubbles stored at different storage temperatures followed an Arrhenius relation with an activation energy for rupture of the shell of approximately 27 kT. This strength ensures applicability of microbubbles in food processes only at moderate temperatures and storage for a moderate period of time. After the proteins in the shell are cross-linked, the microbubbles can withstand pressures and temperatures that are representative of food processes.

Synthesis, characterization and stability of BSA-encapsulated microbubbles

In this work, we present an account of experimental studies performed for the synthesis, shelf stability andin vitrostability of microbubbles made from perfluorobutane (PFB) gas and coated in a shell of Bovine Serum Albumin (BSA).

Analysis of Bovine Serum Albumin Ligands fromPuerariae flosUsing Ultrafiltration Combined with HPLC-MS

Rapid screening techniques for identification of active compounds from natural products are important not only for clarification of the therapeutic material basis, but also for supplying suitable chemical markers for quality control. In the present study, ultrafiltration combined with high performance liquid chromatography-mass spectrometry (HPLC-MS) was developed and conducted to screen and identify bovine serum albumin (BSA) bound ligands fromPuerariae flos. Fundamental parameters affecting the screening like incubation time, BSA concentration, pH, and temperature were studied and optimized. Under the optimum conditions, nine active compounds were identified by UV and MS data. The results indicated that this method was able to screen and identify BSA bound ligands form natural products without the need of preparative isolation techniques. Moreover, the method has more effective with easier operation procedures.