Chitosan-hydrophobic alginate nanocomposites stabilized pH-triggered Pickering emulsion for drug controlled-release

Photo-responsive Pickering emulsions triggered by in-situ pH modulation using a photoacid generator

HYPOTHESIS

Pickering emulsions that respond to changes in pH by the addition of acid or alkali have been extensively studied, but the development of photo-responsive Pickering emulsions has been more challenging. This study attempts to demonstrate a novel approach to achieve photo-responsiveness in Pickering emulsions by incorporating a photoacid generator (PAG) into the oil phase. Upon UV irradiation, the PAG is expected to release protons (H+), which can then regulate the pH of the emulsion system and control its stability.

EXPERIMENTS

Amphiphilic colloidal particles obtained by modifying silica particles with poly (2-(dimethylamino)ethyl methacrylate) (SiO2-PDMAEMA) are used to stabilize the Pickering emulsions. The protonation and deprotonation of the SiO2-PDMAEMA particles at different pH values allow for the tuning of emulsion stability. By introducing the PAG into the stable Pickering emulsion system and applying UV irradiation to trigger the in-situ release of H+, the pH of the emulsion is systematically decreased, and the corresponding changes in emulsion stability are investigated.

FINDINGS

The results show that UV irradiation alone cannot induce emulsion instability. However, when PAG is added to the oil phase, the Pickering emulsions exhibit a significant decrease in pH under UV irradiation, ultimately leading to emulsion destabilization and phase separation. At a UV intensity of 20 mW/cm2 for 2 min, the H+ release from the PAG significantly lower the emulsion's pH, causing the SiO2-PDMAEMA particles to detach from the oil-water interface and resulting in emulsion instability. Higher concentrations of SiO2-PDMAEMA particles in the emulsion require more PAG to induce instability, as confirm by confocal laser scanning microscopy (CLSM) image. This study presents a versatile approach to develop photo-responsive Pickering emulsions which can have potential applications in areas such as drug delivery, cosmetics, and responsive materials.

Demulsification of Pickering emulsions: advances in understanding mechanisms to applications

Pickering emulsions are ultra-stable dispersions of two immiscible fluids stabilized by solid or microgel particles rather than molecular surfactants. Although their ultra-stability is a signature performance indicator, often such high stability hinders their demulsification, i.e., prevents the droplet coalescence that is needed for phase separation on demand, or release of the active ingredients encapsulated within droplets and/or to recover the particles themselves, which may be catalysts, for example. This review aims to provide theoretical and experimental insights on demulsification of Pickering emulsions, in particular identifying the mechanisms of particle dislodgment from the interface in biological and non-biological applications. Even though the adhesion of particles to the interface can appear irreversible, it is possible to detach particles via (1) alteration of particle wettability, and/or (2) particle dissolution, affecting the particle radius by introducing a range of physical conditions: pH, temperature, heat, shear, or magnetic fields; or via treatment with chemical/biochemical additives, including surfactants, enzymes, salts, or bacteria. Many of these changes ultimately influence the interfacial rheology of the particle-laden interface, which is sometimes underestimated. There is increasing momentum to create responsive Pickering particles such that they offer switchable wettability (demulsification and re-emulsification) when these conditions are changed. Demulsification via wettability alteration seems like the modus operandi whilst particle dissolution remains only partially explored, largely dominated by food digestion-related studies where Pickering particles are digested using gastrointestinal enzymes. Overall, this review aims to stimulate new thinking about the control of demulsification of Pickering emulsions for release of active ingredients associated with these ultra-stable emulsions.

High internal phase emulsion stabilized by soy protein isolate-Rutin complex: Rheological properties, bioaccessibility and in vitro release kinetics

High internal phase emulsions (HIPEs) are promising carrier materials for encapsulating and delivering hydrophobic bioactive compounds. By strategically adjusting the composition, particle size, or charge of HIPEs, it is possible to enhance both their stability and the bioaccessibility of hydrophobic polyphenols encapsulated within them. In this study, different soy protein isolate (SPI)-rutin (SPI-R) complexes (formed under various preheating temperatures) were used to stabilize HIPEs, while the particle size, and charge of HIPEs was further adjusted through different homogenization rates. The results demonstrated that an optimal preheating temperature of 70 °C for the complex and a homogenization rate of 15,000 rpm for HIPEs enhanced the stability of the entire emulsion system by producing more uniform and smaller droplet distribution with improved rheological properties. Furthermore, in vitro digestion experiments showed that HIPEs stabilized by the SPI-R complexes (HSR) at optimal homogenization rate had better loading efficiency (98.68 %) and bioaccessibility compared to other groups. Additionally, fitting results from release kinetics confirmed that rutin encapsulated by HSR could achieve sustained release effect. Overall, these findings suggest that HSR has great potential as an effective vehicle for delivering hydrophobic bioactive compounds like rutin within the food industry.

Chitosan-Derived Nanocarrier Polymers for Drug Delivery and pH-Controlled Release in Type 2 Diabetes Treatment

Diabetes, particularly Type 2 Diabetes Mellitus (T2DM), is a chronic metabolic disorder with high and increasing global prevalence, characterized by insulin resistance and inadequate insulin secretion. Despite advancements in novel drug delivery systems, widespread and systematic treatment of advanced glycation end products (AGEs) remains challenging due to issues like drug toxicity, low water solubility, and uncontrolled release. Thus, developing nanoplatforms with controlled release capabilities has become a major research focus. Due to its excellent biocompatibility and drug delivery properties, chitosan has attracted considerable attention as a typical biopolymer. In this study, we designed and synthesized an intelligent fluorescence-pH sensitive nanopolymer material using chitosan. We loaded drug 1 and chromium phthalocyanine (CrPc) into folic acid-conjugated carboxymethyl chitosan (FA-CMCS) nanocarriers, forming FA-CMCS@1-CrPc. Comprehensive characterization of FA-CMCS@1-CrPc was conducted using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermal gravimetric analysis (TGA), and gas adsorption analysis (BET). The results indicate that the nanomaterial was successfully synthesized and exhibits excellent specific surface area, biocompatibility, and fluorescence response. Further research revealed that FA-CMCS@1-CrPc not only achieved controlled drug release but also could regulate drug release by adjusting pH. Additionally, due to its strong fluorescence performance, the nanomaterial demonstrated higher detection sensitivity, especially for monitoring the release of 5% trace drugs. An in vitro model of insulin-resistant cells was established to evaluate the effects of the drug delivery system on glucose degradation and AGE-RAGE regulation, providing a foundation for the development of new T2DM drugs.

Modulation the Synergistic Effect of Chitosan-Sodium Alginate Nanoparticles with Ca2+: Enhancing the Stability of Pickering Emulsion on D-Limonene

Pickering emulsions (PEs) have been regarded as an effective approach to sustaining and preserving the bioactivities of essential oils. The aim of this research is to prepare a PE stabilized by chitosan/alginate nanoparticles (CS-SA NPs) for the encapsulation and stabilization of D-limonene. In this work, the influence of calcium ions (Ca2+) on the morphology and interaction of nanoparticles was studied, and then the preparation technology of CS-SA/Ca2+ NPs was optimized. The results showed that the presence of Ca2+ reduced the size of the nanoparticles and made them assume a spherical structure. In addition, under the conditions of 0.2 mg/mL CaCl2, 0.6 mg/mL SA, and 0.4 mg/mL CS, the CS-SA/Ca2+ NPs had the smallest size (274 ± 2.51 nm) and high stability (-49 ± 0.69 mV). Secondly, the PE was prepared by emulsifying D-limonene with CS-SA/Ca2+ NPs, and the NP concentrations and homogenization speeds were optimized. The results showed that the small droplet size PE could be prepared with 2 mg/mL NP and a homogenization speed of 20,000 r/min, and it had excellent antibacterial and antioxidant activities. Most importantly, the emulsion showed higher activity, higher resistance to ultraviolet (UV) and a higher temperature than free D-limonene. This research provides a feasible solution for the encapsulation, protection and delivery of essential oils.

Acetalized starch-based nanoparticles stabilized acid-sensitive Pickering emulsion as a potential antitumor drug carrier

Pickering emulsions are attracting increased attention owing to their therapeutic applications. However, the slow-release property of Pickering emulsions and the in vivo solid particle accumulation caused by the solid particle stabilizer film limit their applications in therapeutic delivery. In this study, drug-loaded, acid-sensitive Pickering emulsions were prepared using acetal-modified starch-based nanoparticles as stabilizers. The acetalized starch-based nanoparticles (Ace-SNPs) not only act as a solid-particle emulsifier to stabilize Pickering emulsions but also exhibit acid sensitivity and degradability, conducive to the destabilization of Pickering emulsions to release the drug and reduce the effect of particle accumulation in an acidic therapeutic environment. In vitro drug release profiles show that 50 % of curcumin was released in 12 h in an acidic medium (pH 5.4), whereas only 14 % of curcumin was released in 12 h at higher pH (7.4), indicating that the Ace-SNP stabilized Pickering emulsion possess good acid-responsive release characteristics in acidic environments. Moreover, acetalized starch-based nanoparticles and their degradation products showed good biocompatibility, and the resulting curcumin-loaded Pickering emulsions exhibited significant anticancer activity. These features suggest that the acetalized starch-based nanoparticle-stabilized Pickering emulsion has the potential for application as an antitumor drug carrier to enhance therapeutic effects.

Pickering emulsions stabilized by homogenized ball-milled eggshell particles in combination with sodium alginate

Eggshells, by-products of egg processing, were ball-milled and homogenized into particles (eggshell particles, ESPs) and then were used as the stabilizer with a two-step oil addition method to produce Pickering emulsions. Meanwhile, sodium alginate (SA) was used to modify the emulsifying ability of ESPs. The results indicated that SA addition helped to improve the dispersion performance and increase the negative charge of ESPs. Pickering emulsions stabilized by ESPs/SA showed much smaller particle size than those stabilized by ESPs. The maximum oil fraction in the ESPs/SA-stabilized emulsions reached up to 0.8, while that was only 0.75 in ESPs-stabilized emulsions. The presence of SA significantly enhanced the freeze-thaw, thermal, dilution, and centrifuge stability of ESPs-stabilized Pickering emulsions. The findings demonstrate the potential of eggshell particles as a kind of natural Pickering stabilizer, which will increase the high value-added utilization of poultry egg industry by-products.

Preparation of Pickering emulsion stabilized by lauroyl lysine

In this paper, the effect of Nε-lauroyl lysine (LL) on stabilizing W/O Pickering emulsions was investigated, and the effect of crystallization temperature on the particle size of LL was explored. The Pickering emulsion was prepared with LL as particle emulsifier, and the effects of homogenization rate, emulsification temperature, particle concentration, oil-water volume ratio and other factors on the preparation of emulsion were discussed. The results showed that the LL particles were the smallest for a crystallization temperature of 30 °C with a size of (1.3 ± 0.2) µm. The oil-water-LL contact angle was 142.9° ± 1.6°, and the prepared emulsion was of W/O type. The most stable emulsions were obtained under the following conditions: homogenization rate = 11,000 r min−1, emulsification temperature = 20 °C, particle concentration = 2 wt%, oil-water volume ratio = 1:1. In addition, LL showed good tolerance to the aqueous phases with different pH values. The LL-stabilized emulsion system proved to be stable over the long term in the stand tests.

Progress in the Application of Food-Grade Emulsions

The detailed investigation of food-grade emulsions, which possess considerable structural and functional advantages, remains ongoing to enhance our understanding of these dispersion systems and to expand their application scope. This work reviews the applications of food-grade emulsions on the dispersed phase, interface structure, and macroscopic scales; further, it discusses the corresponding factors of influence, the selection and design of food dispersion systems, and the expansion of their application scope. Specifically, applications on the dispersed-phase scale mainly include delivery by soft matter carriers and auxiliary extraction/separation, while applications on the scale of the interface structure involve biphasic systems for enzymatic catalysis and systems that can influence substance digestion/absorption, washing, and disinfection. Future research on these scales should therefore focus on surface-active substances, real interface structure compositions, and the design of interface layers with antioxidant properties. By contrast, applications on the macroscopic scale mainly include the design of soft materials for structured food, in addition to various material applications and other emerging uses. In this case, future research should focus on the interactions between emulsion systems and food ingredients, the effects of food process engineering, safety, nutrition, and metabolism. Considering the ongoing research in this field, we believe that this review will be useful for researchers aiming to explore the applications of food-grade emulsions.

pH-sensitive hyaluronic acid-targeted prodrug micelles constructed via a one-step reaction for enhanced chemotherapy

Although many chemotherapy prodrugs have been developed for tumor therapy, non-targeted delivery, uncontrolled release and tedious construction procedure of prodrugs still limit their clinical application in tumor treatment. In this work, hyaluronic acid (HA) which has tumor-targeting ability was used to conjugate to antitumor drug podophyllotoxin (PPT) to construct a pH-sensitive prodrug named HA-CO-O-PPT just via a one-step esterification reaction. The HA-CO-O-PPT spontaneously assembled into nano spherical micelles in aqueous medium, which had outstanding serum stability and blood compatibility. The obtained prodrug micelles (named HP micelles) exhibited a pH-responsive drug release mode with cumulative release reaching 81.2% due to their dissociation in response to acid stimulus, and had a high cellular uptake efficiency beyond 97% owing to HA receptor-mediated targeting. Furthermore, it was found that the prodrug micelles showed excellent antitumor activities in vivo with the tumor inhibition ratio up to 85% and negligible systemic toxicity. Accordingly, the pH-responsive HP micelles constructed by a simple one-step reaction, could be a promising candidate as a chemotherapeutic agent for cancer therapy.

Ion-responsive chitosan hydrogel actuator inspired by carrotwood seed pod

Inspired by the gradient hygroscopic structure of carrotwood seed pod, patterned anisotropic structure was created in polysaccharide hydrogel by an anodic electrical writing process. Locally released Fe²⁺ was oxidized to Fe³⁺ and chelated with chitosan chains in the written area, resulting in a gradient structure in the hydrogel. The asymmetrical stress generated by the different swelling of the gradient structure enables the hydrogel to bend autonomously. The hydrogel shows opposite bending in deionized water and NaCl solution. The physicochemical properties of the hydrogel are characterized by tensile test, SEM, EDS, XRD, TGA, DTG and FT-IR. SEM and EDS show that the written hydrogel has a structural gradient and a concentration gradient of Fe³⁺ vertically. Moreover, anodic electrical writing increases the flexibility of chitosan hydrogel due to decreased crystallinity. This controllable electrical writing technique is convenient to create patterned anisotropic structure and provide a novel design concept for natural hydrogel actuators.

Physicochemical properties of fucoidan and its applications as building blocks of nutraceutical delivery systems

Many bioactive ingredients with health effects such as antioxidant, anti-inflammatory and neuroprotective possess low bioavailability due to poor solubility and sensitivity. Fucoidan is an ideal material for encapsulating bioactive ingredients because of its unique physicochemical and biological properties, which can improve the function and application of bioactive ingredients. Nevertheless, there is still a lack of review about the physicochemical properties as well as functionalities of fucoidan and the application of fucoidan-based delivery systems in functional food. Hence, in this review, recent advances on the structure, chemical modification, physicochemical properties and biological activity of fucoidan are summarized. This review systematacially describes the recent update on the fucoidan as a wall material for delivering nutraceuticals with a broad discussion on various types of delivery systems ranging from nanoparticles, nanoparticle/bead complexes, emulsions, edible films, nanocapsules and hydrogels. Futhermore, the technical scientific issues of the application of fucoidan in the field of food are emphasized. On the basis of more comprehensive and deeper understandings, the review ends with a concluding remark on future directions of fucoidan-based delivery systems for purposes. Novel fucoidan-based delivery systems such as aerogels, Pickering emulsions, emulsion-filled-hydrogels, liposomes-in-fucoidan, co-delivery systems of bioactive igredients can be designed.

DOX-loaded silver nanotriangles and photothermal therapy exert a synergistic antibreast cancer effect via ROS/ERK1/2 signaling pathway

The combination of multiple therapies has been proved to be more effective than a single therapy for many cancers. This study aimed to investigate the synergistic antibreast cancer effect of doxorubicin-loaded silver nanotriangles (DOX-AgNTs) combined with near-infrared (NIR) irradiation and explore the underlying mechanism. AgNTs were prepared by a chemical method and DOX was loaded via electrostatic adsorption. Characterization was performed by transmission electron microscopy, ultraviolet-visible spectroscopy and dynamic light scattering. The viability of MDA-MB-231 cells was detected by using MTT assay to evaluate the synergistic anticancer effect of DOX-AgNTs combined with NIR irradiation. The intracellular reactive oxygen species (ROS) level and cell apoptosis were analyzed by flow cytometry. Mitochondrial membrane potential (MMP) was measured with fluorescence microscopy. The mechanism was further investigated with ROS scavenger N-acetylcysteine and specific inhibitors of extracellular signal-regulated kinase 1/2 (ERK1/2), C-jun N-terminal kinase and p38 pathways. Characterization results revealed that the prepared AgNTs were mostly triangular and the mean edge length was about 126 nm. The combination of DOX-AgNTs and NIR exhibited a superior synergistic anticancer effect over single DOX-AgNTs or photothermal therapy (PTT). N-acetylcysteine and ERK1/2 inhibitor U0126 were found to significantly rescue the decreased cell viability, declined MMP and increased apoptosis induced by the combined treatment. Our results suggested that DOX-AgNTs combined with PTT performed a synergistic antibreast cancer effect. The synergy might be closely associated with the excessive production of ROS, changed MMP and the activation of ERK1/2 signaling pathway. These findings might provide a new perspective for the development of breast cancer treatments with excellent efficacy.

Structural changes in pH-responsive gelatin/hydroxypropyl methylcellulose phthalate blends aimed at drug-release systems

The present study aimed to investigate the thermal- and pH-dependent gelation behavior of gelatin/HPMCP blends using ultraviolet (UV) spectrophotometry, viscoelasticity, and dynamic light scattering (DLS). We found that the release of lisinopril from gelatin/HPMCP gels can be inhibited at low pH. UV spectrophotometric analysis showed that pH had a significant effect on the transparency of aqueous HPMCP systems and gelatin/HPMCP gels. The viscoelastic patterns of gelatin/HPMCP at pH 4.6 considerably differed from those of gelatin/HPMCP at pH 5.2 and 6.0. DLS measurements showed that HPMCP molecules in low concentrations underwent strong aggregation below pH 4.8. Such HPMCP aggregation induces a physical barrier in the matrix structures of the gelatin/HPMCP gels, which inhibits the drug release at pH 1.2. This hydrogel delivery system using polymer blends of gelatin/HPMCP can be used in oral gel formulations with pH-responsive properties.

Fabrication and antibacterial evaluation of peppermint oil-loaded composite microcapsules by chitosan-decorated silica nanoparticles stabilized Pickering emulsion templating

Novel peppermint oil (PO)-loaded composite microcapsules (CM) with hydroxypropyl methyl cellulose (HPMC)/chitosan/silica shells were effectively fabricated by PO Pickering emulsion, which were stabilized with chitosan-decorated silica nanoparticles (CSN). The surface modification of chitosan could improve the hydrophobicity of silica nanoparticles and favor their adsorption at the oil-water interface of PO Pickering emulsions. The microcapsule composite shells were formed dependent on the electrostatic adsorption of HPMC and CSN, and further subjected to spray-drying. The peppermint oil-loaded composite microcapsules with 100% HPMC as wall material (PO-CM@100%HPMC) seemed to be optimum formulation based on the prolonged release, acceptable entrapment efficiency (89.1%) and drug loading (25.5%). The PO-CM@100%HPMC could remarkably prolong the stability of PO. Moreover, the PO-CM@100%HPMC had a long-term antimicrobial activity (85.4%) against S. aureus and E. coli even after storage for 60 days. Therefore, the Pickering emulsions based microcapsules seemed to be a promising strategy for antibacterial application for PO.

Bioactive Ibuprofen-Loaded PLGA Coatings for Multifunctional Surface Modification of Medical Devices

To modulate the biofunctionality of implantable medical devices commonly used in clinical practice, their surface modification with bioactive polymeric coatings is an attractive and successful emerging strategy. Biodegradable coatings based on poly(lactic acid-co-glycolic acid), PLGA, represent versatile and safe candidates for surface modification of implantable biomaterials and devices, providing additional tunable ability for topical delivery of desired therapeutic agents. In the present study, Ibuprofen-loaded PLGA coatings (PLGA/IBUP) were obtained by using the dip-coating and drop-casting combined protocol. The composite materials demonstrated long-term drug release under biologically simulated dynamic conditions. Reversible swelling phenomena of polymeric coatings occurred in the first two weeks of testing, accompanied by the gradual matrix degradation and slow release of the therapeutic agent. Irreversible degradation of PLGA coatings occurred after one month, due to copolymer's hydrolysis (evidenced by chemical and structural modifications). After 30 days of dynamic testing, the cumulative release of IBUP was ~250 µg/mL. Excellent cytocompatibility was revealed on human-derived macrophages, fibroblasts and keratinocytes. The results herein evidence the promising potential of PLGA/IBUP coatings to be used for surface modification of medical devices, such as metallic implants and wound dressings.