A simplified and miniaturized glucometer-based assay for the detection of ß-glucosidase activity.

ß-Glucosidase activity assays constitute an important indicator for the early diagnosis of neonatal necrotizing enterocolitis and qualitative changes in medicinal plants. The drawbacks of the existing methods are high consumption of both time and reagents, complexity in operation, and requirement of expensive instruments and highly trained personnel. The present study provides a simplified, highly selective, and miniaturized glucometer-based strategy for the detection of ß-glucosidase activity. Single-factor experiments showed that optimum ß-glucosidase activity was exhibited at 50 °C and pH 5.0 in a citric acid-sodium citrate buffer when reacting with 0.03 g/mL salicin for 30 min. The procedure for detection was simplified without the need of a chromogenic reaction. Validation of the analytical method demonstrated that the accuracy, precision, repeatability, stability, and durability were good. The linear ranges of ß-glucosidase in a buffer solution and rat serum were 0.0873-1.5498 U/mL and 0.4076-2.9019 U/mL, respectively. The proposed method was free from interference from ß-dextranase, snailase, ß-galactosidase, hemicellulase, and glucuronic acid released by baicalin. This demonstrated that the proposed assay had a higher selectivity than the conventional dinitrosalicylic acid (DNS) assay because of the specificity for salicin and unique recognition of glucose by a personal glucose meter. Miniaturization of the method resulted in a microassay for ß-glucosidase activity. The easy-to-operate method was successfully used to detect a series of ß-glucosidases extracted from bitter almonds and cultured by Aspergillus niger. In addition, the simplified and miniaturized glucometer-based assay has potential application in the point-of-care testing of ß-glucosidase in many fields, including medical diagnostics, food safety, and environmental monitoring.

[Transthyretin-binding activity of hexabromocyclododecanes (HBCDs) and its thyroid hormone disrupting effects after developmental exposure].

In vivo and in vitro research approaches were carried out to survey the potential health risk of environmental exposure by hexabromocyclododecanes (HBCDs). Transthyretin-binding assay was designed to test for the potency of HBCDs to compete with thyroxine (T4) for binding to the transport protein. The results showed that the binding of 25I-T4 and T4 was only slightly inhabited even at the highest competitive concentration of HBCDs (75.08%, 80 micromol x L(-1)), indicating the marginally interfere potency of HBCDs in the transportation of T4. Sprague-Dawley rats of 3-days old were exposed to 0.2 mg/kg and 1 mg/kg HBCDs for 21 d to examine the thyroid hormones (THs) disrupting effects of HBCDs after developmental exposure. Compared with the controls, levels of total 3,3',5-triiodothyronine (TT3), free 3,3',5-triiodothyronine (FT3), increased significantly (p < 0.05, p < 0.05) in low- and high-dose exposures, thyroid stimulating hormone (TSH) also increased slightly while the total thyroxine (TT4), free thyroxine (FT4) had a decline about two-fold inversely. Combined both the in vivo and in vitro results, the possible mode of action of HBCDs on THs disruption may through the synergy or substitution effect of T3. The findings support further investigation of the potential THs disrupting effects of HBCDs on public health, especially on children during brain development.

[Vascular endothelial cells targeted Tyr-RGD-PEG-PEI nano-drug synthesis and its biological activity].

The study is designed to synthesize nano-carrier Tyr-RGD (cyclo-[Arg-Gly-Asp-d-Tyr-Lys]) and poly(ethylene glycol) modified polyethylenimine (Tyr-RGD-PEG-PEI) targeting vascular endothelial cells, then analyze its nanoparticle properties and the characteristics of drug carrying and targeting properties in vivo / in vitro tumor. The nano-carrier Tyr-RGD-PEG-PEI was synthesized with the method of chemical synthesis and the properties of this nanoparticle and drug carrying characteristics were identified. Its effect of targeting vascular endothelial cells in vitro was studied with the method of competitive binding assay. The fluorescent labeled nano-drug was injected into tumor-bearing nude mice to observe its tumor-targeting. The mean size of nano-carrier Tyr-RGD-PEG-PE was about 145 nm, good in encapsulation efficiency of siRNA. After incubation in plasma for half an hour, only about 3 percent of siRNA out. It was confirmed that it was a single spot with TLC analysis, the R(f) value was 0.65. Receptor competition experiments showed that the nano could effectively compete with RGD in binding the receptors on endothelial cells. Tumor-bearing nude mice experiments showed that when containing a fluorescent-labeled siRNA of Tyr-RGD-PEG-PEI nano-drug was injected into mice, after 24 hours this nano-drug mainly distributed within the tumor tissue. However, nano-drug without Tyr-RGD appeared in tumor tissue as well as other organs such as livers, lungs, etc. The Tyr-RGD-targeted gene vector Tyr-RGD-PEG-PEI synthesized in this study has good nanoparticle properties and high efficiency of gene-drug encapsulation. Study of nude mice shows that the ability of its tumor-targeting is significantly better than nano-drug without Tyr-RGD.

[Folate-poly-L-lysine-Gd-DTPA as MR contrast agent for tumor imaging via folate receptor-targeted delivery].

OBJECTIVE: To study folate-conjugated Gd-DTPA-Poly-L-Lysine (folate-PL-Gd-DTPA) as MR targeting agent to tumor cells via folate receptor, to evaluate feasibility and effectiveness by observing MR signal variations and imaging feature of pulmonary tumor xenografts in nude mice using this contrast material. METHODS: (1) Using Poly-L-Lysine (PL) as linker, after PL was tethered with caDTPA, GdCl(3) was added to label DTPA-PL, then PL-Gd-DTPA was conjugated to folate, a specific MR contrast agent, was thus prepared. (2) Using high performance liquid chromatography (HPLC) to evaluate the conjugate purity, and the ICP-AES to test Gd(3+) concentration, while the activity evaluated by competitive folate receptor binding with folic acid. (3) Folate-PL-Gd-DTPA as specific contrast agents (study group, n = 6) and Gd-DTPA as non-specific contrast agents (control group, n = 4) was injected respectively into caudal vein of the nude mice which was pulmonary tumor xenografts as experimental model in the study. MRI was performed with plain scans, enhanced scans at 30 minutes, 3 hours, 6 hours, 14 hours, 24 hours, 38 hours, 48 hours, 62 hours and 72 hours after the success of injection. Signal intensities of tumors and muscles were measured. RESULTS: (1) folate-PL-Gd-DTPA was successfully synthesized with high affinity to folate receptor and high concentration of Gd(3+) (56 Gd(3+)/folate). (2) folate-PL-Gd-DTPA had an excellent tumor selectivity in pulmonary tumor xenografts in the animal model. After injection, the tumor signal intensity in the study group was significantly higher than that observed before injection; An average intensity increase of 125.4% was observed from pre-contrast to post-contrast images of the tumor, which was observed at 24 - 48 hours after injection; The muscle signal intensity at any time-point after injection showed no statistically difference with that observed before injection. In control group, the tumor signal intensity showed statistically difference with that observed before injection at 0.5 hour and 3 hours, the biggest difference appeared at 0.5 hour; The muscle signal intensity at 0.5 hour time-point showed statistically difference with that observed before injection. CONCLUSION: Folate-PL-Gd-DTPA could be combined to tumor cells appetencially via folate receptor and significantly targeted to tumor cells with rich folate receptors for MR imaging.

Synthesis and biological evaluation of diethylenetriamine pentaacetic acid-polyethylene glycol-folate: a new folate-derived, (99m)Tc-based radiopharmaceutical.

(99m)Technetium-labeled diethylenetriamine pentaacetic acid-polyethylene glycol-folate (DTPA-PEG-folate) was synthesized and tested as a radiopharmaceutical agent, which targeted the lymphatic system with metastatic tumor. Folic acid was reacted with H2N-PEG-NH2 to yield H2N-PEG-folate. After purification by anion-exchange chromatography, the product was reacted with cyclic DTPA. By removal of unreacted DTPA by size-exclusion chromatography, DTPA-PEG-Folate was obtained. Fluorescein-5-isothiocyanate (FITC)-labeled DTPA-PEG-folate and DTPA-PEG-OCH3 were prepared via a dicyclohexylcarbodiimide-mediated coupling. In vitro competitive binding test showed that the uptake of [125I] folic acid was inhibited by DTPA-PEG-folate and the 50% inhibitory concentration was 4.37 pmol/L (R2 = 0.9922). The relative affinity of DTPA-PEG-FITC was 0.18 for human folate receptor comparing with folic acid. In cultured tumor cells, uptake of fluorescence-labeled DTPA-PEG-folate was found to increase significantly in folate-deficient medium compared with that of untargeted DTPA-PEG-OCH3 and FITC-ethylenediamine. The competition with free folic acid blocked the cell uptake of DTPA-PEG-folate. These results confirmed the DTPA-PEG-folate entered into KB cells through the folate receptor endocytosis pathway in vitro. The radiolabeled yield of [(99m)Tc] DTPA-PEG-folate was in excess of 98%, and specific activities of 7.4 kBq (0.2 microCi/microg) were achieved. After subcutaneous injection, [(99m)Tc] DTPA-PEG-folate exhibited an initial increase and successive decline of accumulation in popliteal nodes in normal Wistar rats. Expect for the kidney, uptake by other tissues was rather low. In a normal rabbit imagine study, the lymphatic vessels were readily visualized by single-photon-emission computed tomography following subcutaneous injection of [(99m)Tc] DTPA-PEG-folate. In conclusion, the [(99m)Tc] DTPA-PEG-folate conjugate may have a potential as a lymphatic tumor-targeted radiopharmaceutical.