Yu Ping Li

A review of biodegradable polymeric systems for oral insulin delivery

Abstract Currently, repeated routine subcutaneous injections of insulin are the standard treatment for insulin-dependent diabetic patients. However, patients’ poor compliance for injections often fails to achieve the stable concentration of blood glucose. As a protein drug, the oral bioavailability of insulin is low due to many physiological reasons. Several carriers, such as macromolecules and liposomes have been used to deliver drugs in vivo. In this review article, the gastrointestinal barriers of oral insulin administration are described. Strategies for increasing the bioavailability of oral insulin, such absorption enhancers, enzyme inhibitors, enteric coatings are also introduced. The potential absorption mechanisms of insulin-loaded nanoparticles across the intestinal epithelium, including intestinal lymphatic route, transcellular route and paracellular route are discussed in this review. Natural polymers, such as chitosan and its derivates, alginate derivatives, γ-PGA-based materials and starch-based nanoparticles have been exploited for oral insulin delivery; synthetic polymers, such as PLGA, PLA, PCL and PEA have also been developed for oral administration of insulin. This review focuses on recent advances in using biodegradable natural and synthetic polymers for oral insulin delivery along with their future prospects.

Pluronic P85/poly(lactic acid) vesicles as novel carrier for oral insulin delivery.

Poly(lactic acid)-b-Pluronic-b-poly(lactic acid) (PLA-P85-PLA) vesicles were developed as novel carrier for oral insulin delivery. PLA-P85-PLA block copolymer was synthesized by ring opening polymerization of the monomer l-lactide using Pluronic copolymer P85 as the initiator. Insulin-loaded PLA-P85-PLA vesicles were prepared by dialysis method and the mean diameter of insulin-loaded PLA-P85-PLA vesicles was determined to be 178 nm. The cytotoxicity studies using human ovarian cancer cells OVCAR-3 indicate that PLA-P85-PLA block copolymer has good biocompatibility. Both in vitro and in vivo release behavior of insulin loaded in PLA-P85-PLA vesicles were studied. It was observed that insulin was released out gradually from PLA-P85-PLA vesicles and almost all insulin was released out 7.5h later. More importantly, for the oral administration of insulin-loaded PLA-P85-PLA vesicles at insulin doses of 200 IU/kg, the minimum blood glucose concentration was observed in the diabetic mice test after 2.5h, which was 15% of initial glucose level. Furthermore, the blood glucose concentration increased slowly to 31.8% of initial blood glucose concentration after 10.5h and was maintained at this level for at least an additional 14h (32.5% of initial blood glucose concentration at 24.5h). These results proved that PLA-P85-PLA vesicles could be promising polymeric carriers for oral insulin delivery application due to their sustained and enhanced hypoglycemic effect.

In vitro &in vivo targeting behaviors of biotinylated Pluronic F127/poly(lactic acid) nanoparticles through biotin-avidin interaction.

Biotinylated Pluronic F127/poly(lactic acid) block copolymers (B-F127-PLA) were successfully synthesized previously by our group. In the present study, the release behaviors of paclitaxel-loaded B-F127-PLA nanoparticles and their targeting properties to human ovarian carcinoma cells were investigated. Paclitaxel (pac) loaded in B-F127-PLA nanoparticles shows an initial burst release in the first 6h and followed by a slow release. The in vitro targeting behaviors of B-F127-PLA nanoparticles against human ovarian cancer cells (OVCAR-3, SKOV-3) were investigated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) tests and fluorescence microscopy (FM) technique. Targeting was based on a three-step biotin-avidin targeting approach using biotinylated anti-CA125 antibody specific for the CA-125 antigen that is highly expressed on OVCAR-3 cells but not expressed on SKOV-3 cells. MTT results show that the anticancer effect of paclitaxel in B-F127-PLA nanoparticles over OVCAR-3 cells was stronger than that over SKOV-3 cells, indicating that B-F127-PLA nanoparticles were delivered more effectively to OVCAR-3 cells than to SKOV-3 cells. The targeting behaviors of B-F127-PLA nanoparticles were further confirmed by FM technique. The intracellular distribution of B-F127-PLA nanoparticles was also studied using a triple-labeling method. It was observed that B-F127-PLA nanoparticles are mainly localized within the cytoplasm of OVCAR-3 cells. The in vivo antitumor efficacy of pac-loaded B-F127-PLA nanoparticles by three-step method as measured by change in tumor volume of OVCAR-3 implanted in Balb/C nude mice was greater than that by one-step method.

Active Targeting Behaviors of Biotinylated Pluronic/Poly(Lactic Acid) Nanoparticles In Vitro through Three-Step Biotin–Avidin Interaction

In order to prepare targeted drug carriers, previously a biotin group has been attached by our group to the end of Pluronic F87/poly(lactic acid) and Pluronic P85/poly(lactic acid) block co-polymers to obtain B-F87–PLA and B-P85–PLA, respectively. In this paper, the active targeting properties of B-F87–PLA and B-P85–PLA nanoparticles in vitro were investigated through a three-step biotin–avidin interaction by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) tests and fluorescence microscopy (FM). Two kinds of human ovarian cancer cells (OVCAR-3 and SKOV-3) and paclitaxel were chosen for the cytotoxicity tests. CA-125 antigen is over-expressed on OVCAR-3 cells but not on SKOV-3 cells. The loading and release behavior of paclitaxel loaded in B-Pluronic–PLA nanoparticles were also studied. Paclitaxel loaded in both B-F87–PLA and B-P85–PLA nanoparticles shows an initial rapid release followed by a slow release period. Compared with SKOV-3 cells, the cytotoxicity results implied that paclitaxel-loaded B-Pluronic–PLA nanoparticles were delivered more effectively to OVCAR-3 cells due to the specific interaction between the biotin groups on the surface of B-Pluronic–PLA nanoparticles and the avidin/biotinylated MAb X306/CA-125 antigen complexes on the surface of OVCAR-3 cells. The active targeting properties of B-F87–PLA nanoparticles were further confirmed by FM.

Enhanced effect of folated pluronic F87-PLA/TPGS mixed micelles on targeted delivery of paclitaxel

Targeted drug delivery systems have great potential to overcome the side effect and improve the bioavailability of conventional anticancer drugs. In order to further improve the antitumor efficacy of paclitaxel (PTX) loaded in folated Pluronic F87/poly(lactic acid) (FA-F87-PLA) micelles, D-α-tocopheryl poly(ethylene glycol) 1000 succinate (TPGS or Vitamin E TPGS) were added into FA-F87-PLA to form FA-F87-PLA/TPGS mixed micelles. The LE of PTX-loaded mixed micelles (13.5%) was highest in the mass ratio 5 to 3 of FA-F87-PLA to TPGS. The in vitro cytotoxicity assays indicated that the IC50 values for free PTX injections, PTX-loaded FA-F87-PLA micelles and PTX-loaded FA-F87-PLA/TPGS mixed micelles after 72h of incubation were 1.52, 0.42 and 0.037mg/L, respectively. The quantitative cellular uptake of coumarin 6-loaded FA-F87-PLA/TPGS and FA-F87-PLA micelles showed that the cellular uptake efficiency of mixed micelles was higher for 2 and 4h incubation, respectively. In vivo pharmacokinetic studies found that the AUC of PTX-loaded FA-F87-PLA/TPGS mixed micelles is almost 1.4 times of that of PTX-loaded FA-F87-PLA micelles. The decreased particle size and inhibition of P-glycoprotein effect induced by the addition of TPGS could result in enhancing the cellular uptake and improving the antitumor efficiency of PTX-loaded FA-F87-PLA/TPGS mixed micelles.

Novel folated Pluronic/poly(lactic acid) nanoparticles for targeted delivery of paclitaxel

The purpose of this study was to explore the in vitro and in vivo targeting behaviors of novel folated Pluronic/poly(lactic acid) block copolymers (FA–Pluronic–PLA) for the anticancer drug, paclitaxel. Both paclitaxel-loaded FA–Pluronic–PLA nanoparticles show in vitro sustained release and in vivo prolonged circulation time. The in vitro actively targeting behavior of paclitaxel-loaded FA–Pluronic–PLA nanoparticles against OVCAR-3 cells (folate receptor positive) was proved by the cytotoxicity tests. The in vivo targeting properties of nanoparticles were also studied in OVCAR-3 ovarian tumor-bearing mice. It was observed that the tumor growth percentage for targeted paclitaxel-loaded FA–F127–PLA nanoparticles is lower than that for non-targeted paclitaxel-loaded PLA–F127–PLA nanoparticles. It was observed from FM images that FA–Pluronic–PLA nanoparticles are mainly localized within the cytoplasm of OVCAR-3 cells.

The targeting properties of folate-conjugated Pluronic F127/poly (lactic-co-glycolic) nanoparticles

Novel Folated Pluronic F127/poly (lactic-co-glycolic) (FA-F127-PLGA) and PLGA-F127-PLGA block copolymer were synthesized and nanoparticles self-assembled from these two copolymers were prepared by dialysis method. Paclitaxel (PTX) was successfully encapsulated in these two nanoparticles. According to in vitro release studies of PTX-loaded nanoparticles, after an initial burst release during the first 11h, the entrapped PTX released slowly in the following 82h. The cytotoxicity studies demonstrated that the in vitro antitumor effect of PTX could be improved by encapsulating PTX into PLGA-F127-PLGA nanoparticles. Moreover, folate-targeted FA-F127-PLGA nanoparticles were more effective than PLGA-F127-PLGA when delivering PTX in folate receptor overexpressing OVCAR-3 cells, which mainly due to the FA-receptor-meditated endocytosis. As the treatment time became longer, the targeting effects were more obvious. The targeting effect of FA-F127-PLGA nanoparticles was also investigated in vitro by measuring the cellular uptake of the nanoparticles. The results showed that FA-F127-PLGA nanoparticles were more easily to be uptaken by OVCAR-3 cells in comparison with PLGA-F127-PLGA nanoparticles. In vivo pharmacokinetic studies indicated that FA-F127-PLGA nanoparticles prolong the circulation time of PTX in plasma, and delay the blood clearance of PTX. These results indicated that Folated FA-F127-PLGA could be a potential carrier in long-term PTX delivery.

Antioxidant Activities of Xiao-Yan-Hua-Jie-San and Identification of the Active Components

Xiao-Yan-Hua-Jie-San (XYHJS), a traditional Chinese prescription, is used as a medication recipe to clinically treat inflammation and hepatitis. In previous study, we reported the hepatoprotective effects of XYHJS by increasing an antioxidant enzyme activity in mice. In the present study, the main bioactive components of XYHJS and their antioxidant activity were further investigated by using different model systems in vitro. The total phenolics content in the extract of XYHJS was determined by the Folin-Ciocalteu method. Analysis of the major phenolic compounds in the extract of XYHYS was carried out by high-performance liquid chromatography (HPLC) and thin layer chromatographic (TLC) method. The total phenolic content of the extract was 2.84 ± 0.06 mg gallic acid equivalent (GAE)/g extract powder. The phenolic acid in XYHJS was found to be gallic acid (GA). The content of GA was 2.80 mg/ml by HPLC (n=5, RSD=1.26%). Furthermore, the antioxidant activity of XYHJS extract was determined by 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH) scavenging activity and hydroxyl free radicals (·OH) scavenging activity assay. The radical scavenging activity of XYHJS increased significantly in a concentration-dependent manner. At a concentration of 2.5 mg/ml, the DPPH and ·OH scavenging activity was 89.94% and 91.53%, respectively. It can be concluded that the content of GA in XYHJS is very high and it is the main contributor to the antioxidant activity of XYHJS. Our study indicates that XYHJS prescription could be considered to be an effective agent in the prevention of various liver diseases associated with oxidative stress.

The Stimulatory Activities of Baicalein and Baicalin Compounds Derived from Scutellaria baicalensis on Insulin Secretion In Vitro

The medicinal plant Scutellaria baicalensis Georgi has been used widely in traditional Chinese medicine for anti-inflammation, anticancer, antiviral and antibacterial infections, reducing the total cholesterol level and decreasing blood pressures. Baicalein and baicalin are two major flavonoid of Scutellaria baicalensis Georgi, exhibit various bioactivities. In the present study, the stimulatory activity of baicalin and baicalein derived from Scutellaria baicalensis on insulin secretion in vitro was investigated using HIT-T15 cell, a Syrian hamster transformed β-cell line. The survival rate of cells treated with baicalin or baicalein (0.01-0.5 mg/ml) increased significantly (P < 0.05). In the presence of 5.6 mM glucose, baicalin or baicalein (0.01-0.5 mg/ml) increased glucose-stimulated insulin secretion and cellular ATP levels in HIT-T15 cells. Baicalin and baicalein exhibited significant stimulatory activity in a dose-dependent manner without apparent cytotoxicity at concentrations less than 0.1 mg/ml. The results obtained in this study suggest that baicalin or baicalein increases the insulin secretion of HIT-T15 cells by the enhancement of β-cells activity and cellular ATP levels. Baicalin or baicalein could be candidates for a new class of anti-diabetic drugs.

Stereo-Controlled Total Synthesis of Ieodomycins A and B

A highly convergent formal synthesis of Ieodomycins A and B was achieved in 7 steps. The key features involved in the synthetic sequence of Ieodomycins A and B are the Sharpless asymmetric epoxidation and the Mukaiyama aldol reaction[. The synthesis of C-3 epimer of Ieodomycins A and B was also accomplished in good yields, but now just Heptyl diene aldehyde was getted thought 4 steps. Use Geraniol as meterials to make the corresponding aldehyde (1) via Swern oxidation. Though epoxidation, Wittig reaction and HIO4 oxidation to get the intermediate . Useing it though few steps, the target molecule can be getted.