Novel Fluorescent Microemulsion: Probing Properties, Investigating Mechanism, and Unveiling Potential Application

Recent Progress of Preparation Strategies in Organic Nanoparticles for Cancer Phototherapeutics

Phototherapy has the advantages of being a highly targeted, less toxic, less invasive, and repeatable treatment, compared with conventional treatment methods such as surgery, chemotherapy, and radiotherapy. The preparation strategies are significant in order to determine the physical and chemical properties of nanoparticles. However, choosing appropriate preparation strategies to meet applications is still challenging. This review summarizes the recent progress of preparation strategies in organic nanoparticles, mainly focusing on the principles, methods, and advantages of nanopreparation strategies. In addition, typical examples of cancer phototherapeutics are introduced in detail to inform the choice of appropriate preparation strategies. The relative future trend and outlook are preliminarily proposed.

In Vitro Evaluation of a Fluorescent Microemulsion as an Oral Delivery Carrier and its Potential Application in Tracking Bioactive Compounds Label-Free

In this work, a microemulsion emitting fluorescence was fabricated as a potential oral delivery system for bioactive compounds. In simulated oral administration, the microemulsion was characterized for its microstructure by ¹hydrogen-nuclear magnetic resonance (¹H-NMR). Results showed that microemulsions not only have good resistance to oral and gastric phases, but also lay a solid foundation for the release of bioactive compounds in the intestine. Fluorescence stability tests showed that microemulsions exhibit a remarkable fluorescence intensity in the digestive environment, indicating feasibility as a label-free delivery carrier. Moreover, in vitro release tests of bioactive compounds confirmed that an α-linolenic acid (ALA)-loaded microemulsion mainly released in the intestine, thereby achieving the aim of controlling the release of bioactive compounds. These results suggest that the synthesized fluorescent microemulsion, combining the favorable features of nontoxicity, antidigestive stability, remarkable fluorescence intensity, and controllable release, can be regarded as a promising label-free delivery carrier for oral administration.

Formation and stability of Eucommia ulmoides Oliver seed oil-loaded inverse microemulsion formed by food-grade ingredients and its antioxidant activities

Eucommia ulmoides Oliver seed oil (E.u oil) as a functional oil is rich in many natural active components such as α-linolenic acid (56% to 63%), vitamin E, aucubin, and so on. In this study, water-in-oil (W/O) microemulsions composed of Eucommia ulmoides Oliver seed oil, distilled water, a blend of Sorbitan monooleate 80 (Span 80) and Polysorbate (20) sorbitan monooleate (Tween 80), and propylene glycol were prepared for improving the compatibility of Eucommia ulmoides Oliver seed oil. Pseudoternary phase diagrams were built to illustrate the phase behavior of the microemulsions, based on hydrophilic-lipophilic balance values, cosurfactant type, the proportion of cosurfactant, and the changing environmental stress. Dynamic light scattering, transmission electron microscopy, and electrical conductivity measurements were performed to characterize the microstructural aspects. The optimum process conditions at which the Eucommia ulmoides Oliver seed oil-loaded microemulsion had good tolerance to pH and salinity were: Propylene glycol served as cosurfactant, water-Propylene glycol, and Span 80-Tween 80 ratios separately kept constant at 1:1 and 6:4. These microemulsions with narrow size distribution, nanoscale particle size (below 60 nm), transparent appearance had a wide range of oil phase content and free-radical scavenging capacity toward DPPH and ABTS radicals with half-maximal inhibitory concentration (IC₅₀ ) values of 49.20 and 33.43 mg/mL, respectively. PRACTICAL APPLICATION: This nanostructure, environmental stability, and antioxidant activity of microemulsions containing Eucommia ulmoides Oliver seed oil is a potential delivery system as an alternative to α-linolenic acid and can be used for the delivery of peptides, proteins, antioxidants, and water-soluble nutrients.

Antiproliferative Ability and Fluorescence Tracking of α-Linolenic Acid-Loaded Microemulsion as Label-Free Delivery Carriers in MDA-MB-231 Cells

In this work, the effects of α-linolenic acid (ALA) loaded in oil-in-water (O/W) and water-in-oil-in-water (W/O/W) microemulsions on cell viability, lactic dehydrogenase (LDH) viability, and reactive oxygen species (ROS) levels were examined using Cell Counting Kit-8 (CCK-8), an LDH assay kit, and a fluorescence microscope, respectively. The CCK-8 assay demonstrated that ALA inhibited MDA-MB-231 human breast cancer cell proliferation in a dose-dependent manner. Further, the results of LDH activity and ROS levels revealed that ALA-induced cancer cell damage was closely related to oxidative stress. Under the irradiation of ultraviolet light, the microemulsion without any added fluorescent dye would emit bright blue fluorescence, and the fluorescent images of the cells treated with ALA-loaded O/W and W/O/W microemulsions at different incubation times were taken, which exhibited long-term photostability and biocompatibility. In addition, the fluorescence mechanism of the microemulsion was explained by immobilizing surfactant molecules with aggregation-induced emission (AIE) properties at the water-oil interface through the microemulsion with a self-assembled structure. These findings showed the potential application of O/W and W/O/W microemulsions as the label-free delivery carriers in long-term imaging of living cells and real-time release monitoring of nutrients.

Preparation of α-Linolenic-Acid-Loaded Water-in-Oil-in-Water Microemulsion and Its Potential as a Fluorescent Delivery Carrier with a Free Label

Our previous work has demonstrated that α-linolenic acid (ALA)-loaded oil-in-water (O/W) microemulsion could enhance ALA antioxidant capacity. Meanwhile, we also observed that synthesized microemulsion itself had fluorescence. In this work, we have prepared a multiple water-in-oil-in-water (W/O/W) microemulsion to further enhance ALA antioxidant capacity and activate this delivery carrier application potential with a free label. The compositions of primary water-in-oil (W/O) microemulsion were obtained using pseudo-ternary phase diagrams, and then W/O/W microemulsion was prepared adopting the "two-step heterotherm method". The conductivity of W/O/W microemulsion was measured to lie between 250.0 and 350.0 μs/cm. The spherical droplets with a mean particle diameter of 10.0-20.0 nm were confirmed by transmission electron microscopy and dynamic light scattering. Nuclear magnetic resonance confirmed that ALA diffused to the multiple water-oily interface simultaneously. In addition, the in vitro release and antioxidant capacity measurements of ALA-loaded W/O/W microemulsion concluded the sustained-release effect and excellent antioxidant capacity. The fluorescent intensity of W/O/W microemulsion was markedly increased in comparison to O/W microemulsion. The synthesized microemulsion could lead to important applications and have advantages of a label-free fluorescent carrier for optical imaging purposes.

Substantial Enhancement of the Antioxidant Capacity of an α-Linolenic Acid Loaded Microemulsion: Chemical Manipulation of the Oil-Water Interface by Carbon Dots and Its Potential Application

Various active ingredients play a crucial role in providing and supplementing the nutritional requirements of organisms. In this work, we attempted to chemically manipulate the interfacial microstructure of oil-water microemulsions (ME) with carbon dots (CDs), concentrating on substantially enhancing the antioxidant capacity of α-linolenic acid (ALA). To this end, CDs were synthesized and introduced into an ME. The molecular interaction of surfactant with CDs was investigated by Fourier-transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). The microstructure of the ME was monitored by transmission electron microscopy (TEM) and cryo-electron microscopy (cryo-EM). The cryo-EM result showed the oil-water interface in the ME was better defined after the CDs were loaded, and ¹H NMR proved the CDs were distributed mainly at the interface. On the basis of these results, interfacial models were proposed. Final evaluation results demonstrated the stabilizing effect and oxidation-inhibition ability of the ALA-loaded ME was substantially enhanced after the introduction of the CDs, indicating a "turn off" effect of the interface. Interestingly, CDs do not affect the in vitro release of ALA, indicating a "turn on" effect of the interface. This work provided a successful interface manipulation with a nanocarrier that can be used for a large diversity of food nutraceuticals.