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Preparative separation and purification of rebaudioside A from steviol glycosides using mixed-mode macroporous adsorption resins (MARs) were systematically investigated. Mixed-mode MARs were prepared by a physical blending method. By evaluation of the adsorption/desorption ratio and adsorption/desorption capacity of mixed-mode MARs with different proportions toward RA and ST, the mixed-mode MAR 18 was chosen as the optimum strategy. On the basis of the static tests, it was found that the experimental data fitted best to the pseudosecond-order kinetics and Temkin-Pyzhev isotherm. Furthermore, the dynamic adsorption/desorption experiments were performed on the mini column packed with mixed-mode MAR 18. After one run treatment, the purity of rebaudioside A in purified product increased from 40.77 to 60.53%, with a yield rate of 38.73% (W/W), and that in residual product decreased from 40.77 to 36.17%, with a recovery yield of 57.61% (W/W). The total recovery yield reached 96.34% (W/W). The results showed that this method could be utilized in large-scale production of rebaudioside A from steviol glycosides in industry.

According to the Friedel-Crafts and amination reaction, a series of macroporous adsorption resins (MARs) with novel structures were synthesized and identified by the Brunauer-Emmett-Teller (BET) method and Fourier transform infrared (FTIR) spectra, and corresponding adsorption behaviors for (-)-epigallocatechin gallate (EGCG) and caffeine (CAF) extracted from waste tea were systemically investigated. Based on evaluation of adsorption kinetics, the kinetic data were well fitted by pseudo-second-order kinetics. Langmuir, Freundlich, Temkin-Pyzhev, and Dubinin-Radushkevich isotherms were selected to illustrate the adsorption process of EGCG and CAF on the MARs. Thermodynamic parameters were adopted to explain in-depth information of inherent energetic changes associated with the adsorption process. The effect of temperature on EGCG and CAF adsorption by D101-3 was further expounded. Van der Waals force, hydrogen bonding, and electrostatic interaction were the main driving forces for the adsorption of EGCG and CAF on the MARs. This study might provide a scientific reference point to aid the industrial large-scale separation and enrichment of EGCG from the extracts of waste tea using modified MARs.

A series of macroporous adsorption resins (MARs) with novel structure were synthesized on the basis of the Friedel-Crafts catalyzed and amination reaction. Adsorption feature of the synthetic resins with respect to the purification effect were investigated systemically by employing rutin as the adsorbate. Different from traditional adsorption patterns, the results showed interesting conclusions: (1) With the increase in the temperature of the experiment, the adsorption capacity increased gradually; with the increase in the concentration of the initial solution, the adsorption capacity increased to the maximum and then decreased gradually. (2) The classical models that the inductive effect transmitted to the first layer and the adsorption process contained in one compartment could not explain our experimental results reasonably. Thus, a new adsorption isotherm model that the inductive effect passed on to a higher layer and a new adsorption kinetics model in which the adsorption process contained more compartments were created according to the multiparameter theory and Karickhoff's theory by investigating the regression of the experimental results. The conclusion that the inductive effect passed to the fourth layer and the adsorption process contained four compartments was drawn.

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Codelivery of multiple chemotherapeutics with different action mechanisms is a promising strategy for cancer treatment. In this study, we developed a novel polymer-dendrimer hybrid nanoparticle-based nanosystem for efficient and controlled codelivery of two model chemotherapeutics, doxorubicin (DOX) and paclitaxel (PTX). The nanosystem was characterized to have a nano-in-nano structure with a size of around 150 nm. The model drugs could feasibly be loaded into the nanosystem ratiometrically with high drug-loading contents by controlling the feeding drug ratios. Also, the model drugs could be released from the nanosystem following a sequential release manner-specifically, quick PTX release and sustained DOX release. Acidic pH was found to enhance the release of both drugs. Moreover, the nanosystem was taken up by cancer cells rapidly and efficiently, and the delivered drugs could release sustainably and efficiently in cells to reach their action targets. In vitro cytotoxicity results demonstrated that, by optimizing drug ratios, the dual-drug-loaded nanosystem could result in better antitumor efficacy than the single-drug-loaded nanosystem or free dual-drug combination. Furthermore, the dual-drug-loaded nanosystem could induce significant changes in both the nucleus and tubulin patterns synergistically. All data suggest that the nano-in-nano polymer-dendrimer hybrid nanoparticle-based nanosystem is a promising candidate to achieve controlled multidrug delivery for effective combination cancer therapy.

By targeting CD44 receptors, inhibiting multidrug resistance (MDR), controlling drug release, and synergistically inhibiting tumor growth, a multilayered nanosystem was developed to serve as a multifunctional platform for the treatment of drug-resistant breast cancers. The multilayer nanosystem is composed of a poly(lactic-co-glycolic acid) core, a liposome second layer, and a chitosan third layer. The chitosan-multilayered nanoparticles (Ch-MLNPs) can co-deliver three chemotherapeutic agents: doxorubicin (DOX), paclitaxel (PTX), and silybin. The three drugs are released from the multilayered NPs in a controlled and sequential manner upon internalization and localization in the cellular endosomes. The presence of a chitosan layer allows the nanosystem to target a well-characterized MDR breast cancer biomarker, the CD44s receptor. In vitro cytotoxicity study showed that the nanosystem loaded with triple drugs, DOX–PTX–silybin, resulted in better antitumor efficacy than the single-drug or dual-drug nano-formulations. Likely attributed to the MDR-inhibition effect of silybin, the co-delivered DOX and PTX exhibited a better synergistic effect on MDR breast cancer cells than on non-MDR breast cancer cells. The in vivo study also showed that the multilayered nanosystem promoted MDR inhibition and synergy between chemotherapeutic agents, leading to significant tumor reduction in a xenograft animal model. Ch-MLNPs reduced the tumor volume by fivefold compared to that of the control group without causing overt cytotoxicity.