Deep eutectic solvents as a green alternative to organic solvents for ß-cyclodextrin pseudo-stationary phase in capillary electrophoresis.

ß-cyclodextrin (ß-CD), as an important pseudo-stationary phase (PSP) in capillary electrophoresis (CE), frequently confronts challenges stemming from its limited water solubility, particularly when high concentrations are required for resolving complex analytes. Traditionally, researchers often resort to the use of (toxic) organic solvents to enhance the solubility of ß-CD, establishing non-aqueous capillary electrophoresis (NACE) for specific separations. However, such practices are hazardous to health and run counter to the principles of green analytical chemistry. In this study, we demonstrate a deep eutectic solvent (DES), Proline:Urea (PU), as a promising alternative to conventional organic solvents for ß-CD-based CE separations. The DES exhibits a solubility of up to 30% for ß-CD, a significant improvement compared to the 1.8% solubility in the aqueous phase. Utilizing this DES-type separation medium, we achieved simultaneous baseline separation of a complex analyte composed of eight structurally similar naphthoic acid derivatives. Furthermore, we conducted a systematic comparison of ß-CD's performance in aqueous CE buffers, organic solvents, and DESs, highlighting the superiority of this novel and environmentally friendly CE separation medium.

Capillary electrophoresis separations with deep eutectic solvents as greener separation media: A proof-of-concept study.

Capillary electrophoresis (CE) has conventionally been classified into aqueous and non-aqueous categories based on the types of buffer solvents employed. Traditionally, non-aqueous CE has always been associated with the use of organic solvents, which are considered hazardous to health and environmentally detrimental. In this work, we introduce deep eutectic solvents (DESs) as CE separation media for the first time, presenting a novel and environmentally friendly approach to CE separations. The DES employed consists of proline and urea (Proline:Urea, PU), both of which are naturally occurring compounds that are readily available, cost-effective, and environmentally benign. Various fundamental aspects of the DES-type CE media were investigated, including thermal property, viscosity, electroconductivity, Joule heating effect, and compatibility with detectors. A simulated complex mixture of ten naphthalene-based compounds with varied charges and sizes was separated using the DES-based medium in capillary zone electrophoresis (CZE) mode. Moreover, we also established a DES-based micellar electrokinetic chromatography (MEKC) system utilizing Tween-20 as the surfactant. Six structurally similar naphthalene derivatives (isomers) that couldn't be resolved by CZE were effectively separated due to their strong hydrophobic interaction with Tween-20 micelles within the DES medium. Given that DESs are "designer" solvents with highly tunable properties and environmentally friendly characteristics, this study demonstrates the potential of employing DESs as an alternative to organic solvents for greener CE separations.

Chiral separation by capillary electrokinetic chromatography with hydrophobic deep eutectic solvents as pseudo-stationary phases.

This study demonstrated for the first time that hydrophobic deep eutectic solvents (HDESs) can be used in capillary electrophoresis (CE) for chiral separations. We found that the an HDES methyltrioctylammonium chloride:octanoic acid (N8881Cl:OctA) can exist in the form of nano-sized microdroplets in CE background electrolyte solutions, and show hydrophobic effects as a new type of pseudo-stationary phase (PSP) during CE separation. When used in combination with various cyclodextrin (CD)-type chiral selectors, the presence of N8881Cl:OctA significantly improved the enantioresolutions of several model drugs. Moreover, the migration time of the enantiomers can also be reduced when an anionic CD (e.g., carboxymethyl-ß-cyclodextrin (CM-ß-CD)) was used. Critical factors influencing the chiral separations were systematically investigated including the HDES concentration, hydrogen-bond acceptor (HBA)/hydrogen-bond donor (HBD) ratio, CD concentration, buffer pH, and applied voltage, etc. An insight into chiral recognition mechanism with HDES is provided for reference. A comparison of the chiral CE performance of HDESs with traditional surfactants was also performed to demonstrate their superiority as a new type of PSP.

A feasibility study on the use of hydrophobic eutectic solvents as pseudo-stationary phases in capillary electrophoresis for chiral separations.

A critical challenge in using deep eutectic solvents (DESs) in capillary electrophoresis (CE) is to develop separation systems in which a DES can really work as a single entity. To achieve this, the authors recently demonstrated a novel strategy that takes advantage of the aqueous dispersibility of hydrophobic DESs (or more accurately hydrophobic eutectic solvents (HESs)). However, the previous work was limited only to the separation of achiral analytes, e.g., analogues, homologues, and isomers. The present study was designed as a follow-up study in order to explore the feasibility of employing HES-type pseudo-stationary phases (PSPs) in CE for chiral separations. By using carboxymethyl-ß-cyclodextrin (CM-ß-CD) as a model chiral selector, we provide the first evidence that there is a potential synergistic effect between HESs and traditional chiral selectors. Specifically, the combined use of HES (-)-menthol:octanoic acid and CM-ß-CD allowed excellent enantioseparations of several basic drugs which were not able to be resolved in the single CM-ß-CD system. The enantioresolutions were significantly improved while the migration times of the enantiomers were also shortened due to the hydrophobic mechanism of the HES-type PSP. Critical factors influencing the novel chiral CE system were systematically investigated. Since HESs are considered as "designer" solvents with highly tunable properties, this study demonstrates the potential of employing HESs (or HDES)-type PSPs in CE for chiral separations.

Self-Assembled Tocopherol-Albumin Nanoparticles with Full Biocompatibility for Chemo-photothermal Therapy against Breast Cancer.

BACKGROUND: The combination of photothermal therapy (PTT) and chemotherapy has proven to be a promising strategy for cancer treatment. Various nanomaterials have shown great potential in combination therapy, including gold, graphene oxide, iron oxide, and other nanoparticles. However, their undefinable toxicity in vivo greatly slowed down their development for clinical applications. OBJECTIVE: The present work aimed to develop a multifunctional nanoparticle for chemo-photothermal therapy composed of acknowledged biocompatible materials. METHODS: A novel biocompatible nanoparticle (HIT-NPs) was self-assembled through the intrinsic interaction between D-α-tocopherol Succinate (TOS), human serum albumin (HSA) and indocyanine green (ICG). Doxorubicin (DOX) was then loaded due to the ion pairing between DOX and TOS. The feasibility of combined chemo-photothermal therapy induced by DOX-loaded HIT-NPs was carefully evaluated. RESULTS: In vitro, HIT-NPs showed no cytotoxicity on human normal liver cells (HL-7702 cells) but obvious killing effects on murine breast cancer cells (4T1 cells). The combined chemo-photothermal therapeutic effect on 4T1 cells was successfully obtained. DOX-loaded HIT-NPs could effectively accumulate in 4T1 subcutaneous tumors after intravenous injection, and the tumor temperature rapidly increased under laser exposure, indicating the feasibility of PTT in vivo. CONCLUSION: The self-assembled HIT-NPs could provide a promising platform for combined chemo- photothermal cancer therapy with full biocompatibility.

Effect of light regime and provenance on leaf characteristics, growth and flavonoid accumulation in Cyclocarya paliurus (Batal) Iljinskaja coppices.

BACKGROUND: As a highly valued and multiple function tree species, Cyclocarya paliurus is planted and managed for timber production and medical use. However, limited information is available on its genotype selection and cultivation for growth and phytochemicals. Responses of growth and secondary metabolites to light regimes and genotypes are useful information to determine suitable habitat conditions for the cultivation of medicinal plants. RESULTS: Both light regime and provenance significantly affected the leaf characteristics, leaf flavonoid contents, biomass production and flavonoid accumulation per plant. Leaf thickness, length of palisade cells and chlorophyll a/b decreased significantly under shading conditions, while leaf areas and total chlorophyll content increased obviously. In the full light condition, leaf flavonoid contents showed a bimodal temporal variation pattern with the maximum observed in August and the second peak in October, while shading treatment not only reduced the leaf content of flavonoids but also delayed the peak appearing of the flavonoid contents in the leaves of C. paliurus. Strong correlations were found between leaf thickness, palisade length, monthly light intensity and measured flavonoid contents in the leaves of C. paliurus. Muchuan provenance with full light achieved the highest leaf biomass and flavonoid accumulation per plant. CONCLUSIONS: Cyclocarya paliurus genotypes show diverse responses to different light regimes in leaf characteristics, biomass production and flavonoid accumulation, highlighting the opportunity for extensive selection in the leaf flavonoid production.