Effect of Retro-Inverso Isomer of Bradykinin on Size-Dependent Penetration of Blood-Brain Tumor Barrier.

Retro-inverso bradykinin (RI-BK) has better metabolic stability and higher affinity for the BK type 2 (B2) receptor, compared with bradykinin. At low doses, RI-BK can selectively enhance the permeability of the blood-brain tumor barrier (BBTB) without harming normal brain tissue. In this study, gold nanoparticles (GNPs) of size ranging from 5 to 90 nm are synthesized to assess the optimal size of nanocarriers that achieves maximum brain accumulation after the treatment of RI-BK. The ability of the GNPs to cross the BBTB is tested in a rat C6 glioma tumor model. The results of inductively coupled plasma-mass spectrometry and transmission electron microscopy indicate that GNPs with size of 70 nm achieve maximum permeability to the glioma. The present study supports the conclusion that RI-BK can enhance the permeability of BBTB and provides fundamental information for further development of nanomedicines or nanoprobes for glioma therapy.

D-Peptides as Recognition Molecules and Therapeutic Agents.

Over recent years, D-peptides have attracted increasing attention. D-peptides increase enzymatic stability, prolong the plasma half-life, improve oral bioavailability, and enhance binding activity and specificity with receptor or target proteins, in comparison with the corresponding L-peptide. Therefore, D-peptides are considered to have potential as recognition molecules and therapeutic agents. This review focuses on the design and application of D-peptides with biological activity.

D-SP5 Peptide-Modified Highly Branched Polyethylenimine for Gene Therapy of Gastric Adenocarcinoma.

Peptide-mediated targeting of tumors has become an effective strategy for cancer therapy. Retro-inverso peptides resist protease degradation and maintain their bioactivity. We used the retro-inverso peptide D(PRPSPKMGVSVS) (D-SP5) as a targeting ligand to develop gene therapy for gastric adenocarcinoma. D-SP5 has a higher affinity for human gastric adenocarcinoma (SGC7901) cells compared with that of its parental peptide, L(SVSVGMKPSPRP) (L-SP5). Polyethylenimine (PEI)/pDNA, polyethylene glycol (mPEG)-PEI/pDNA and D-SP5-PEG-PEI/pDNA were prepared for further study. Quantitative luciferase assays showed the transfection efficiency of D-SP5-PEG-PEI/pGL(4.2) was larger compared with that of mPEG-PEI/pGL(4.2). Flow cytometry assays revealed that the apoptosis rates of SGC7901 cells treated with D-SP5-PEG-PEI/pTRAIL were larger than mPEG-PEI/pTRAIL. Western blot assays indicated that the expression of tumor necrosis factor-related apoptosis inducing ligand (TRAIL) protein in SGC7901 cells treated with D-SP5-PEG-PEI/pTRAIL was higher compared with that in cells treated with mPEG-PEI/pTRAIL. In vivo pharmacodynamics study revealed that D-SP5-PEG-PEI/pTRAIL could inhibit the growth of gastric adenocarcinoma SGC7901 xenografts in nude mice. Our results demonstrate that D-SP5-PEG-PEI is a safe and efficient gene delivery vector with potential applications in antitumor gene therapy.

Two-stage prediction of the effects of imidazolium and pyridinium ionic liquid mixtures on luciferase.

The predicted toxicity of mixtures of imidazolium and pyridinium ionic liquids (ILs) in the ratios of their EC50, EC10, and NOEC (no observed effect concentration) were compared to the observed toxicity of these mixtures on luciferase. The toxicities of EC50 ratio mixture can be effectively predicted by two-stage prediction (TSP) method, but were overestimated by the concentration addition (CA) model and underestimated by the independent action (IA) model. The toxicities of EC10 ratio mixtures can be basically predicted by TSP and CA, but were underestimated by IA. The toxicities of NOEC ratio mixtures can be predicted by TSP and CA in a certain concentration range, but were underestimated by IA. Our results support the use of TSP as a default approach for predicting the combined effect of different types of ILs at the molecular level. In addition, mixtures of ILs mixed at NOEC and EC10 could cause significant effects of 64.1% and 97.7%, respectively. Therefore, we should pay high attention to the combined effects in mixture risk assessment.

[Microplate luminometry for toxicity bioassay of chemicals on luciferase].

A new microplate luminometry for the toxicity bioassay of chemicals on firefly luciferase, was developed using the multifunctional microplate reader (SpectraMax M5) to measure the luminous intensity of luciferase. Efects of luciferase concentration, luciferin concentration, ATP concentration, pH, temperature, and reaction time on the luminescence were systematically investigated. It was found that ATP exerted a biphasic response on the luciferase luminescence and the maximum relative light units (RLU) occurred at an ATP concentration of 1.1 x 10(-4) mol x L(-1). The method was successfully employed in the toxic effect test of NaF, NaCl, KBr and NaBF4 on luciferase. Using nonlinear least square technique, the dose-response curves (DRC) of the 4 chemicals were accurately fitted with the coefficient of determination (R2) between the fitted and observed responses being greater than 0.99. The median effective concentration (EC50) of the 4 chemicals were accurately measured from the DRC models. Compared with some literatures, the bioassay is a fast easy-operate and cost-effective method with high accuracy.

A novel peptide ligand RAP12 of LRP1 for glioma targeted drug delivery.

The receptor associated protein (RAP) is a 39 kDa chaperone protein, binding tightly to low-density lipoprotein receptor-related protein-1 (LRP1) that is overexpressed in glioma, tumor neovasculature, vasculogenic mimicry (VM), the blood-brain barrier (BBB) and the blood-brain tumor barrier (BBTB). Herein, we miniaturized the RAP protein into a short peptide RAP12 (EAKIEKHNHYQK) aiding by computer-aided peptide design technique. RAP12 contained the essential lysines at the positions 253 and 256. The binding affinity of RAP12 to LRP1 was theoretically and experimentally evaluated. In cellular level, RAP12 could effectively internalize into U87, HUVEC and bEnd.3 cells. When modified on the surface of PEG-PLA micelles (RAP12-PEG-PLA), RAP12 could effectively facilitate the penetration of micelles through the BBB/BBTB in vitro/vivo. Paclitaxel-loaded RAP12-PEG-PLA could remarkably inhibit the growth of glioma cells and the formation of tumor neovasculature and VM, significantly prolong the median survival time of nude mice bearing intracranial glioma in comparison to model mice treated with plain micelles or Taxol. These results suggested that the RAP12 held the potential for multifunctional glioma-targeted drug delivery.

A facile approach to functionalizing cell membrane-coated nanoparticles with neurotoxin-derived peptide for brain-targeted drug delivery.

The blood brain barrier separates the circulating blood from the extracellular fluid in the central nervous system and thus presents an essential obstacle to brain transport of therapeutics. Herein, we report on an effective brain-targeted drug delivery system that combines a robust red blood cell membrane-coated nanoparticle (RBCNP) with a unique neurotoxin-derived targeting moiety. The RBCNPs retain the complex biological functions of natural cell membranes while exhibiting physicochemical properties that are suitable for effective drug delivery. CDX peptide is derived from candoxin and shows high binding affinity with nicotinic acetylcholine receptors (nAChRs) expressed on the surface of brain endothelial cells. Through a facile yet robust approach, we successfully incorporate DCDX peptides onto the surface of RBCNPs without compromising the peptide's brain targeting ability. The resulting DCDX-RBCNPs show promising brain targeting efficiency both in vitro and in vivo. Using a glioma mouse model, we demonstrate that doxorubicin-loaded DCDX-RBCNPs have superior therapeutic efficacy and markedly reduced toxicity as compared to the nontargeted drug formulations. While RBCNPs are used as a model system to evaluate the surface modification approach, the reported method can be readily generalized to various types of cell membrane-derived nanocarriers for broad medical applications.

MPEG-DSPE polymeric micelle for translymphatic chemotherapy of lymph node metastasis.

Lymph node metastasis is one of the major pathways for tumor formation and it is difficult to deliver chemotherapeutics at therapeutic concentrations to lymph node metastasis. This study prepared methyl poly(ethylene glycol)-distearoylphosphatidylethanolamine/doxorubicin (MPEG-DSPE/DOX) micelle for the treatment of lymph node metastasis. The MPEG-DSPE/DOX micelle prepared were of spherical morphology with a particle size of 20 ± 5 nm. The uptake rates of DOX and MPEG-DSPE/DOX micelle by A375 cells were 51.2% and 88.7%, respectively. The phagocytosis rate of MPEG-DSPE/Rhodamine B micelle by RAW264.7 cells was 17.2-fold lower than for Rhodamine B alone. After subcutaneous injection, MPEG-DSPE micelle underwent lymphatic absorption and accumulated in popliteal lymph nodes. MPEG-DSPE/DOX micelle significantly alleviated damage to the subcutaneous tissue of the injection sites compared with DOX alone. We established a model of nude mice bearing lymph node metastasis of A375 cells. After subcutaneous injection, the weights of both the popliteal and iliac lymph nodes of the MPEG-DSPE/DOX micelle group were significantly lower than in the saline and DOX groups. MPEG-DSPE/DOX micelle effectively killed the tumor cells in popliteal and iliac lymph nodes. In conclusion, MPEG-DSPE micelle is a promising drug delivery system for the treatment of lymph node metastasis.

Retro-inverso bradykinin opens the door of blood-brain tumor barrier for nanocarriers in glioma treatment.

The blood-brain barrier and the blood-brain tumor barrier (BBTB) prevent most drugs entering brain tumors. Complicated preparation procedures of drug delivery systems and damage to normal brain tissue have limited the application of many strategies for the treatment of brain tumor in clinical trials. We have designed a bradykinin analog, retro-inverso bradykinin (RI-BK), which is characterized by resistance to proteolysis and high binding activity with the bradykinin type 2 (B2) receptor. After systemic administration, RI-BK binds to B2 receptors and induces a change in zonula occluden-1 and depolymerization of F-actin to selectively open the BBTB. RI-BK increased the accumulation of drug-loaded nanocarriers in the glioma but not in normal brain. Co-administration with RI-BK enhanced the therapeutic efficiency of drug-loaded nanocarriers for glioma. These findings suggest that RI-BK could be translated into the clinic as an adjunctive treatment for malignant brain tumors.

Predicting synergistic toxicity of heavy metals and ionic liquids on photobacterium Q67.

Results from three mathematical approaches to predict the toxicity of uniform design mixtures of four heavy metals (HMs) including Cd(II), Ni(II), Cu(II), and Zn(II) and six ionic liquids (ILs) were compared to the observed toxicity of these mixtures on Vibrio qinghaiensis sp.-Q67. Single toxicity analysis indicated that the ILs had greater toxicity than the HMs. Combined toxicities of HMs and ILs were found to be synergistic. The combined toxicities were underestimated by concentration addition (CA) and independent action (IA) models. However, the mixture toxicities were effectively predicted by the integrated CA with IA based on multiple linear regression model (ICIM). We propose that ICIM model can serve as a useful tool for predicting the toxicity of interactive mixtures.