Recent Progress toward Physical Stimuli-Responsive Emulsions

Advancements in emulsion systems for specialized infant formulas: Research process and formulation proposals for optimizing bioavailability of nutraceuticals

With the rapid advancements in nutrition and dietary management, infant formulas for special medical purposes (IFSMPs) have been developed to cater to the unique nutraceutical requirements of infants with specific medical conditions or physiological features. However, there are various challenges in effectively preserving and maximizing the health benefits of the specific nutraceuticals incorporated in IFSMPs. This review provides an overview of the nutritional compositions of various IFSMPs and highlights the challenges associated with the effective supplementation of specific nutraceuticals for infants. In addition, it emphasizes the promising potential of emulsion delivery systems, which possess both encapsulation and delivery features, to significantly improve the solubility, stability, oral acceptance, and bioavailability (BA) of nutraceutical bioactives. Based on this information, this work proposes detailed strategies for designing and developing model IFSMP emulsions to enhance the BA of specially required nutraceuticals. Key areas covered include emulsion stabilization, selective release mechanisms, and effective absorption of nutraceuticals. By following these proposals, researchers and industry professionals can design and optimize emulsion-based IFSMPs with enhanced health benefits. This review not only outlines the developmental states of IFSMP formulations but also identifies future research directions aimed at improving the physiological health benefits of IFSMPs. This effort lays the theoretical groundwork for the further development of emulsion-type IFSMP in infant formula (IF) industry, positioning the IF industry to better meet the complex needs of infants requiring specialized nutrition.

Stimuli-Responsive Polymers for Engineered Emulsions

Emulsions are complex. Dispersing two immiscible phases, thus expanding an interface, requires effort to achieve and the resultant dispersion is thermodynamically unstable, driving the system toward coalescence. Furthermore, physical instabilities, including creaming, arise due to presence of dispersed droplets of different densities to a continuous phase. Emulsions allow the formulation of oils, can act as vehicles to solubilize both hydrophilic and lipophilic molecules, and can be tailored to desirable rheological profiles, including "gel-like" behavior and shear thinning. The usefulness of emulsions can be further expanded by imparting stimuli-responsive or "smart" behaviors by inclusion of a stimuli-responsive emulsifier, polymer or surfactant. This enables manipulation like gelation, breaking, or aggregation, by external triggers such as pH, temperature, or salt concentration changes. This platform generates functional materials for pharmaceuticals, cosmetics, oil recovery, and colloid engineering, combining both smart behaviors and intrinsic benefit of emulsions. However, with increased functionality comes greater complexity. This review focuses on the use of stimuli-responsive polymers for the generation of smart emulsions, motivated by the great adaptability of polymers for this application and their efficacy as steric stabilizers. Stimuli-responsive emulsions are described according to the trigger used to provide the reader with an overview of progress in this field.

Computational Insights into a CO2-Responsive Emulsion Prepared Using the Superamphiphile Assembled by Electrostatic Interactions

The superamphiphiles exhibit broad prospects for fabricating stimuli-responsive emulsions. Because the superamphiphiles are assembled via noncovalent interactions, they have the advantage of fast response and high efficiency. Recently, a series of switchable emulsions using CO2-responsive superamphiphiles have been developed, which extends the applications of CO2-responsive materials in widespread field. However, there is still a lack of fundamental understanding on the switching mechanism related to the assembled structure of superamphiphiles at the oil-water interface. We employed molecular dynamics (MD) simulations to investigate the reversible emulsification/demulsification process of a responsive emulsion system stabilized by a recently developed responsive superamphiphile (BTOA), which consists of oleic acid (OA) and cationic amine (named 1,3-bis(aminopropyl)tetramethyldisiloxane, BT). The simulation results present the morphologies in both the emulsion and demulsification states. It is found that the ionized OA- and the protonated BT+ together form an adsorption layer at the oil-water interface. The hydrophobic parts of BT+ are inserted into the adsorption layer, and the two amine groups contact the water phase. This adsorption layer reduces the interfacial tension and stabilizes the emulsion. After the bubbling of CO2, the surfactants were fully protonated to OA and BT2+. Because of the changes in the molecular polarity, OA and BT2+ entered the oil and water phases, respectively, resulting in demulsification. The structural and dynamical properties were analyzed to reveal the different intermolecular interactions that were responsible for the reversible reversibility of the emulsion. The observations are considered to be complementary to experimental studies and are expected to provide deeper insights into studies on developing responsive materials via supramolecular assemblies.