Cao Xie

Cyclic RGD conjugated poly(ethylene glycol)-co-poly(lactic acid) micelle enhances paclitaxel anti-glioblastoma effect

The use of glioblastoma-targeted drug delivery system facilitates efficient delivery of chemotherapeutic agents to malignant gliomas in the central nervous system while minimizing high systemic doses associated with debilitating toxicities. To employ the high binding affinity of a cyclic RGD peptide (c(RGDyK), cyclic Arginine-Glycine-Aspartic acid-D-Tyrosine-Lysine) with integrin alpha(v)beta(3) over-expressed on tumor neovasculature and U87MG glioblastoma cells, we prepared paclitaxel-loaded c(RGDyK)-Poly(ethylene glycol)-block-poly(lactic acid) micelle (c(RGDyK)-PEG-PLA-PTX). In vitro physicochemical characterization of these novel micelles showed satisfactory encapsulated efficiency, loading capacity and size distribution. In vitro cytotoxicity studies proved that the presence of c(RGDyK) enhanced the anti-glioblastoma cell cytotoxic efficacy by 2.5 folds. The binding affinity of c(RGDyK)-PEG-PLA micelle with U87MG cells was also investigated. The competitive binding IC(50) value of c(RGDyK)-PEG-PLA micelle was 26.30 nM, even lower than that of c(RGDyK) (56.23 nM). In U87MG glioblastoma-bearing nude mice model, biodistribution of (125)I-radiolabeled c(RGDyK)-PEG-PLA or DiR encapsulated micelles and anti-glioblastoma pharmacological effect was investigated after intravenous administration. c(RGDyK)-PEG-PLA micelle accumulated in the subcutaneous and intracranial tumor tissue, and when loaded with PTX (c(RGDyK)-PEG-PLA-PTX), exhibited the strongest tumor growth inhibition among the studied paclitaxel formulations. The anti-glioblastoma effect of c(RGDyK)-PEG-PLA-PTX micelle was also reflected in the median survival time of mice bearing intracranial U87MG tumor xenografts where the median survival time of c(RGDyK)-PEG-PLA-PTX micelle-treated mice (48 days) was significantly longer than that of mice treated with PEG-PLA-PTX micelle (41.5 days), Taxol (38.5 days) or saline (34 days). Therefore, our results suggested that c(RGDyK)-PEG-PLA micelle may be a potential drug delivery system in the treatment of integrin alpha(v)beta(3) over-expressed glioblastoma.

Targeted gene delivery to glioblastoma using a C-end rule RGERPPR peptide-functionalised polyethylenimine complex

Safe and efficient systems capable of specifically targeting brain tumour cells represent a promising approach for the treatment glioblastoma multiforme. Neuropilin-1 (NRP-1) is over-expressed in U87 glioma cells. In the current study, the tumour specific peptide RGERPPR, which binds specifically to NRP-1, was used as a targeting ligand in a gene delivery strategy for glioblastoma. The RGERPPR peptide was coupled to branched polyethylenimine (PEI, 25kDa) using heterobifunctional Mal-PEG-NHS, resulting in a novel gene delivery polymer. Polymer/plasmid DNA (pDNA) complexes were formed and their sizes and zeta potentials were measured. Compared with the unmodified mPEG-PEI/pDNA complexes, the RGERPPR-PEG-PEI/pDNA complex led to a significant enhancement in intracellular gene uptake and tumour spheroid penetration. Furthermore, the RGERPPR-PEG-PEI/pDNA complex facilitated enhanced transfection efficiency levels, as well as a reduction in cytotoxicity when tested in U87 glioma cells in vitro. Most significantly of all, when complexes formed with pDsRED-N1 were injected into the tail vein of intracranial U87 tumour-bearing nude mice, the RGERPPR-PEG-PEI complexes led to improved levels of red fluorescence protein expression in the brain tissue. Taken together, the results show that RGERPPR-PEG-PEI could be used as a safe and efficient gene delivery vehicle with potential applications in glioblastoma gene delivery.

LyP-1-conjugated PEGylated liposomes: a carrier system for targeted therapy of lymphatic metastatic tumor.

The application of liposomes in targeted therapy of lymphatic metastatic tumors has been hampered by the low uptake rate of liposome by metastatic lymph nodes. In this report, LyP-1, a peptide that can specifically bind tumor cells, tumor lymphatics and tumor-associated macrophages, was conjugated to liposomes for targeting and treating lymphatic metastatic tumors. Firstly, LyP-1-conjugated PEGylated liposomes loaded with fluorescein or doxorubicin (DOX) were prepared and showed satisfactory vesicle size and size distribution. The in vitro cellular uptake and in vivo near-infrared fluorescence imaging results showed that LyP-1 modification increased liposome uptake by tumor cells and metastatic lymph nodes, but did not increase uptake by normal lymph nodes. The immunofluorescence analysis evidenced that LyP-1-conjugated liposomes were distributed adjacent to tumor lymphatics and tumor-associated macrophages in metastatic lymph nodes. The pharmacodynamic study suggested that compared with unmodified liposomes, LyP-1-conjugated DOX-loaded liposomes exhibited enhanced inhibition effect on tumor cells in vitro and lymphatic metastatic tumors in vivo. Pathological examination showed that liposomal DOX caused reduced tissue damage to injection site compared with DOX solution. In summary, LyP-1-conjugated PEGylated liposomes could be targeted to metastatic lymph nodes based on their specific binding to tumor cells, tumor lymphatics and tumor-associated macrophages. They are a safe and effective drug delivery system of antineoplastic agents for targeted therapy of lymphatic metastatic tumors.

9-NC-loaded folate-conjugated polymer micelles as tumor targeted drug delivery system: Preparation and evaluation in vitro

In this study, folate-conjugated polymer micelles were synthesized by mixing folate-poly(ethylene glycol)-distearoylphosphatidylethanolamine (FA-PEG-DSPE) and methoxy-poly(ethylene glycol)-distearoylphosphatidylethanolamine (MPEG-DSPE) to encapsulate anticancer agent 9-nitro-camptothecin (9-NC). Formulations were characterized by critical micellization concentration (CMC) values of copolymers, micelle particle size, zeta-potential, encapsulation efficiency and drug loading efficiency. The molar ratio of FA-PEG-DSPE and MPEG-DSPE was chosen to avoid the macrophages and at the same time express highly active targeting ability. The targeting ability of folate-conjugated polymer micelles was investigated against three kinds of tumor cell lines (HeLa, SGC7901 and BXPC3). The drug efficacy in vitro of folate-conjugated polymer micelles was evaluated by using the methylthiazoletetrazolium (MTT) method. The results showed that the CMC values of MPEG-DSPE and FA-PEG-DSPE were 0.97 x 10(-5)M and 1.0 x 10(-5)M, respectively. The average size of folate-conjugated micelle was about 21-24 nm and the micelle size distribution of both empty and drug-loaded micelles were rather narrow. The encapsulation efficiency and drug loading efficiency were 97.6% and 4.64%, respectively. The drug-loaded micelles were stable during storage at 4 degrees C for 4 weeks. Micelles maintain the similar size and did not show 9-NC leakage. The best molar ratio of FA-PEG-DSPE and MPEG-DSPE in folate-conjugated micelles was 1:100 which can effectively solubilize 9-NC, avoid the macrophages in vitro and has a higher anti-tumor activity than both drug-loaded MPEG-DSPE micelles and free anticancer agents. The folate-conjugated polymer micelle which can avoid the macrophages is a kind of promising carrier for poorly soluble anticancer agents via folate receptor (FR) that mediated endocytosis to target tumor cells.

A D‐Peptide Ligand of Nicotine Acetylcholine Receptors for Brain‐Targeted Drug Delivery

Lysosomes of brain capillary endothelial cells are implicated in nicotine acetylcholine receptor (nAChR)-mediated transcytosis and act as an enzymatic barrier for the transport of peptide ligands to the brain. A D-peptide ligand of nAChRs (termed (D)CDX), which binds to nAChRs with an IC50 value of 84.5 nM, was developed by retro-inverso isomerization. (D)CDX displayed exceptional stability in lysosomal homogenate and serum, and demonstrated significantly higher transcytosis efficiency in an in vitro blood-brain barrier monolayer compared with the parent L-peptide. When modified on liposomal surface, (D)CDX facilitated significant brain-targeted delivery of liposomes. As a result, brain-targeted delivery of (D)CDX modified liposomes enhanced therapeutic efficiency of encapsulated doxorubicin for glioblastoma. This study illustrates the importance of ligand stability in nAChRs-mediated transcytosis, and paves the way for developing stable brain-targeted entities.

Oligoarginine-modified biodegradable nanoparticles improve the intestinal absorption of insulin.

The strategy of oral administration of bioactive macromolecules using cell-penetrating peptides (CPPs) is restricted to covalent linkage or electrostatic interaction between the cargo and CPPs. In the present study, we devised an approach utilizing CPP-functionalized poly(lactic-co-glycolic acid) (PLGA) nanoparticles as a carrier for oral delivery of insulin. Pegylated PLGA nanoparticles were modified with poly(arginine)8 enantiomers (l-R8 and d-R8) via a maleimide-mediated covalent conjugating procedure. The physical and chemical features of the nanoparticles were characterized, which confirmed the successful immobilization of R8 to the nanoparticles. Using a Caco-2 cell monolayer model, R8-modified nanoparticles were found to exhibit significantly increased cellular uptake and transportation. Pharmacokinetics and pharmacodynamics of the insulin-loaded nanoparticles were evaluated with rats by intestinal administration. Compared to the unmodified nanoparticles, l-R8 and d-R8 modified-nanoparticles increased the relative bioavailabilities of insulin by 3.2- and 4.4-times, meanwhile, improved the hypoglycemic effects by 2.5- and 3.7-times, respectively. Neither of the R8-modified nanoparticles caused perceptible histological toxicities. The results implied that surface modification of biodegradable nanoparticles with poly(arginine)8, especially with the d-form enantiomer, showed remarkable advancement in promoting the intestinal absorption of insulin. This delivery system is also promising for the delivery of a wide variety of bioactive macromolecules by oral administration.

Imaging brain tumor by dendrimer-based optical/paramagnetic nanoprobe across the blood-brain barrier

A multimodal optical/paramagnetic nanoprobe, Den-Angio, was developed and demonstrated a capability to circumvent the blood brain barrier (BBB) and visualize brain tumors with high sensitivity in vivo. Den-Angio holds promise to pre-operatively localize brain tumors and make image-guided tumor resection possible during surgery.

Poly(ethylene glycol)-block-poly(D,L-lactide acid) micelles anchored with angiopep-2 for brain-targeting delivery.

In this study, angiopep with high transcytosis capacity and parenchymal accumulation was used as a novel ligand for the brain-targeting delivery of poly(ethylene glycol)-block-poly(d,l-lactide acid) (PEG-PLA) micelles. Angiopep-2 was synthesized by solid-phase peptide synthesis, and then conjugated with maleimide-PEG-PLA to form angiopep-PEG-PLA. The micelles composed of methoxy-PEG-PLA (mPEG-PLA) and angiopep-PEG-PLA was prepared by film-hydration method. Near-infrared fluorescence dye, DiR was loaded into micelles to evaluate the brain-targeting ability of micelles with or without angiopep modification by near-infrared fluorescence imaging in vivo and ex vivo. Significant near-infrared (NIR) fluorescent signal was detected in the brain after angiopep-anchored micelles administration and further confirmed by imaging the whole brain and brain slices, compared with that of the micelles without modification. 125I-radiolabeled angiopep-PEG-PLA micelles after intravenous administration in mice showed high brain accumulation for up to 24 h. These results indicate that angiopep-modified PEG-PLA micelle is a promising brain-targeting nanocarrier for lipophilic drugs.

Retro-inverso isomer of Angiopep-2: a stable d-peptide ligand inspires brain-targeted drug delivery.

The blood-brain barrier (BBB) prevents most drugs from reaching the site of central nervous system (CNS) diseases, intensively confining the therapeutic efficiency. Angiopep-2 (here termed (L)Angiopep), which is a 19-mer peptide derived from human Kunitz domain, can trigger transcytosis and traverse the BBB by recognizing low density lipoprotein-related protein 1 (LRP-1) expressed on the brain capillary endothelial cells. Various enzymes in the blood and the BBB, however, present multiple metabolic barriers to peptide-inspired brain-targeted drug delivery. Here we designed a retro-inverso isomer of (L)Angiopep, termed (D)Angiopep, to inspire brain-targeted drug delivery. Both (D)Angiopep and (L)Angiopep displayed high uptake capacity in LRP-1 overexpressed cells, including bEnd.3 and U87 cells. (D)Angiopep demonstrated lower uptake efficiency in both cell lines than did (L)Angiopep, suggestive of lower binding affinity to LRP-1 of the d-peptide. (D)Angiopep was resistant to proteolysis in fresh rat blood serum, while more than 85% of (L)Angiopep disappeared within 2 h. Endocytosed (D)Angiopep and (L)Angiopep were found to be colocalized with lysosomal compartments of bEnd.3 cells, indicating that susceptibility to proteolysis of (L)Angiopep in the BBB may further attenuate its transcytosis efficiency. In vivo, (D)Angiopep modified PEG-DSPE micelles displayed high distribution in normal brain and intracranial glioblastoma. Due to the expression of LRP-1 on the BBB and glioblastoma cells, proteolytically stable (D)Angiopep holds much potential for designing two-order brain tumor targeted delivery systems.

Liposome-based glioma targeted drug delivery enabled by stable peptide ligands

The treatment of glioma is one of the most challenging tasks in clinic. As an intracranial tumor, glioma exhibits many distinctive characteristics from other tumors. In particular, various barriers including enzymatic barriers in the blood and brain capillary endothelial cells, blood-brain barrier (BBB) and blood-brain tumor barrier (BBTB) rigorously prevent drug and drug delivery systems from reaching the tumor site. To tackle this dilemma, we developed a liposomal formulation to circumvent multiple-barriers by modifying the liposome surface with proteolytically stable peptides, (D)CDX and c(RGDyK). (D)CDX is a D-peptide ligand of nicotine acetylcholine receptors (nAChRs) on the BBB, and c(RGDyK) is a ligand of integrin highly expressed on the BBTB and glioma cells. Lysosomal compartments of brain capillary endothelial cells are implicated in the transcytosis of those liposomes. However, both peptide ligands displayed exceptional stability in lysosomal homogenate, ensuring that intact ligands could exert subsequent exocytosis from brain capillary endothelial cells and glioma targeting. In the cellular uptake studies, dually labeled liposomes could target both brain capillary endothelial cells and tumor cells, effectively traversing the BBB and BBTB monolayers, overcoming enzymatic barrier and targeting three-dimensional tumor spheroids. Its targeting ability to intracranial glioma was further verified in vivo by ex vivo imaging and histological studies. As a result, doxorubicin liposomes modified with both (D)CDX and c(RGDyK) presented better anti-glioma effect with prolonged median survival of nude mice bearing glioma than did unmodified liposomes and liposomes modified with individual peptide ligand. In conclusion, the liposome suggested in the present study could effectively overcome multi-barriers and accomplish glioma targeted drug delivery, validating its potential value in improving the therapeutic efficacy of doxorubicin for glioma.