Synergistic tumor microenvironment targeting and blood-brain barrier penetration via a pH-responsive dual-ligand strategy for enhanced breast cancer and brain metastasis therapy.

Cancer associated fibroblasts (CAFs) which shape the tumor microenvironment (TME) and the presence of blood brain barrier (BBB) remain great challenges in targeting breast cancer and its brain metastasis. Herein, we reported a strategy using PTX-loaded liposome co-modified with acid-cleavable folic acid (FA) and BBB transmigrating cell penetrating peptide dNP2 peptide (cFd-Lip/PTX) for enhanced delivery to orthotopic breast cancer and its brain metastasis. Compared with single ligand or non-cleavable Fd modified liposomes, cFd-Lip exhibited synergistic TME targeting and BBB transmigration. Moreover, upon arrival at the TME, the acid-cleavable cFd-Lip/PTX showed sensitive cleavage of FA, which reduced the hindrance effect and maximized the function of both FA and dNP2 peptide. Consequently, efficient targeting of folate receptor (FR)-positive tumor cells and FR-negative CAFs was achieved, leading to enhanced anti-tumor activity. This strategy provides a feasible approach to the cascade targeting of TME and BBB transmigration in orthotopic and metastatic cancer treatment.

Losartan loaded liposomes improve the antitumor efficacy of liposomal paclitaxel modified with pH sensitive peptides by inhibition of collagen in breast cancer.

The dense collagen network in tumors restricts the penetration of drugs into tumors. Free losartan could inhibit collagen, but it would cause hypotension at the dosage of 10 mg/kg/d. In this study, losartan was encapsulated in liposomes (LST-Lip) and the collagen inhibition ability of LST-Lip was investigated. Our results showed the blood pressure was not affected by LST-Lip at the dosage of 2.5 mg/kg every other day. The amount of Evans Blue in tumor in LST-Lip group was 1.98 times of that in control group. Confocal laser scanning microscopy images showed that prior injection of LST-Lip could inhibit collagen and further improve the tumorous accumulation of liposomes modified with TH peptides (AGYLLGHINLHHLAHL(Aib)HHIL-NH2) (TH-Lip) in 4T1 tumors. Compared with control group, the tumor inhibition rate of combined strategy of LST-Lip and paclitaxel loaded TH-Lip (PTX-TH-Lip) was 41.73%, while that of group only treated with PTX-TH-Lip was 14.94%. Masson's trichrome staining confirmed that collagen was inhibited in LST-Lip group. Thus, the administration of LST-Lip in advance could inhibit the collagen in tumors effectively and did not affect the blood pressure, then PTX-TH-Lip injected subsequently could exert enhanced antitumor efficacy. In conclusion, this combined strategy might be promising for breast cancer therapy.

Synergistic dual-ligand doxorubicin liposomes improve targeting and therapeutic efficacy of brain glioma in animals.

Therapeutic outcome for the treatment of glioma was often limited due to low permeability of delivery systems across the blood-brain barrier (BBB) and poor penetration into the tumor tissue. In order to overcome these hurdles, we developed the dual-targeting doxorubicin liposomes conjugated with cell-penetrating peptide (TAT) and transferrin (T7) (DOX-T7-TAT-LIP) for transporting drugs across the BBB, then targeting brain glioma, and penetrating into the tumor. The dual-targeting effects were evaluated by both in vitro and in vivo experiments. In vitro cellular uptake and three-dimensional tumor spheroid penetration studies demonstrated that the system could not only target endothelial and tumor monolayer cells but also penetrate tumor to reach the core of the tumor spheroids and inhibit the growth of the tumor spheroids. In vivo imaging further demonstrated that T7-TAT-LIP provided the highest tumor distribution. The median survival time of tumor-bearing mice after administering DOX-T7-TAT-LIP was significantly longer than those of the single-ligand doxorubicin liposomes and free doxorubicin. In conclusion, the dual-ligand liposomes comodified with T7 and TAT possessed strong capability of synergistic targeted delivery of payload into tumor cells both in vitro and in vivo, and they were able to improve the therapeutic efficacy of brain glioma in animals.

Synergistic cytotoxicity and co-autophagy inhibition in pancreatic tumor cells and cancer-associated fibroblasts by dual functional peptide-modified liposomes.

Pancreatic ductal adenocarcinoma (PDA) is a highly fatal disease with 5-year survival of ∼8.5%. Nanoplatforms such as nab-paclitaxel and nanoliposomal irinotecan demonstrate superiority and utility in treating different progressions of PDA by prolonging the median overall survival by only a few months. Due to the dense surrounding stroma and the high autophagy in pancreatic cancer, integrin ɑvß3 targeting, acid environmental sensitive, TR peptide-modified liposomal platforms loaded with combined autophagy inhibiting hydroxychloroquine (HCQ), and cytotoxic paclitaxel (PTX) were designed (TR-PTX/HCQ-Lip) to accomplish the aim of synergistically killing tumor cells while inhibiting stroma fibrosis. The results showed that TR peptide-modified liposomes (TR-Lip) have superior targeting and penetrating effects both in vitro and in vivo. TR-PTX/HCQ-Lip efficiently inhibited autophagy in pancreatic cells and surrounding cancer-associated fibroblasts. The synergistic anti-fibrosis roles were also confirmed both in vitro and in vivo, all of which contributes to the enhanced curative effects of TR-PTX/HCQ-Lip in both heterogenetic and orthotopic pancreatic cancer models. STATEMENT OF SIGNIFICANCE: Autophagy plays a significant role in pancreatic ductal adenocarcinoma, especially in activating cancer associated fibroblasts which is also related to collagen generation that promotes the formation of dense stroma, which hinder the cytotoxic drugs to target and kill cancer cells. In this study, we designed integrin ɑvß3 targeting, acid environmental sensitive liposomal platforms to co-loaded paclitaxel and the autophagy inhibitor hydroxychloroquine. The results showed that the muti-functional liposomes can target to the pancreatic tumor and efficiently kill tumor cells and inhibit stroma fibrosis, thus improve the therapeutic effect in orthotopic pancreatic cancer models.

pH-sensitive folic acid and dNP2 peptide dual-modified liposome for enhanced targeted chemotherapy of glioma.

Effective chemotherapy for clinical glioma treatment is still lacking due to the poor penetration of blood-brain barrier (BBB) and the poor internalization into tumor cells. To facilitate the transmigration across the BBB as well as the glioma targeting of chemotherapeutics, we constructed cell penetrating peptide dNP2 and tumor microenvironment-cleavable folic acid (FA) dual modified, paclitaxel (PTX) loaded liposome for the targeted delivery of glioma. The modification of dNP2 significantly enhanced the transmigration across the BBB in an in vitro BBB model. The acid-cleavable cFd-Lip/PTX exhibited sensitive cleavage of FA at pH 6.8, which led to enhanced cellular uptake mediated by both cell penetrating peptide dNP2 and the interaction between FA and folate receptor (FR) on the glioma cells. After intravenous injection, compared with non-cleavable Fd-Lip and single modified liposomes, cFd-Lip enhanced the accumulation in orthotropic glioma and improved the anti-tumor effect of glioma-bearing mice. The dual modified liposomes also facilitated deep penetration into tumor cells and consequently enhanced the cytotoxicity of PTX-loaded liposomes. The acid-cleavable dual modified strategy retained the BBB penetrating and tumor targeting ability, meanwhile, the cleavage of FA further maximized the cell permeability of dNP2, exhibiting enhanced tumor targeting effect. The multi-targeting strategy provides a promising approach towards targeted chemotherapy for glioma.

Tandem Peptide Based on Structural Modification of Poly-Arginine for Enhancing Tumor Targeting Efficiency and Therapeutic Effect.

The nonselectivity of cell penetrating peptides had greatly limited the application in systemic administration. By conjugating a dGR motif to the C-terminal of octa-arginine, the formed tandem peptide R8-dGR had been proved to specifically recognize both integrin αvß3 and neuropilin-1 receptors. However, the positive charge of poly-arginine would still inevitably lead to rapid clearance in the circulation system. Therefore, in this study, we tried to reduce the positive charge of poly-arginine by decreasing the number of arginine, to thus achieve improved tumor targeting efficiency. We had designed several different Rx-dGR peptides (x = 4, 6, and 8) modified liposomes and investigated their tumor targeting and penetrating properties both in vitro and in vivo. Among all the liposomes, R6-dGR modified liposomes exhibited a long circulation time similar to that of PEGylated liposomes while they retained strong penetrating ability into both tumor cells and tumor tissues, and thus had displayed the most superior tumor targeting efficiency. Then, paclitaxel and indocyanine green coloaded liposomes were prepared, and R6-dGR modified coloaded liposomes also exhibited enhanced antitumor effect on C6 xenograft tumor bearing mice. Therefore, we suggest R6-dGR as a potential tumor targeting ligand with both strong penetrating ability and improved pharmacokinetic behavior, which could be further used for efficient antitumor therapy.

A New Concept of Enhancing Immuno-Chemotherapeutic Effects Against B16F10 Tumor via Systemic Administration by Taking Advantages of the Limitation of EPR Effect.

The enhanced permeability and retention (EPR) effect has been comfortably accepted, and extensively assumed as a keystone in the research on tumor-targeted drug delivery system. Due to the unsatisfied tumor-targeting efficiency of EPR effect being one conspicuous drawback, nanocarriers that merely relying on EPR effect are difficult to access the tumor tissue and consequently trigger efficient tumor therapy in clinic. In the present contribution, we break up the shackles of EPR effect on nanocarriers thanks to their universal distribution characteristic. We successfully design a paclitaxel (PTX) and alpha-galactosylceramide (αGC) co-loaded TH peptide (AGYLLGHINLHHLAHL(Aib)HHIL-Cys) -modified liposome (PTX/αGC-TH-Lip) and introduce a new concept of immuno-chemotherapy combination via accumulation of these liposomes at both spleen and tumor sites naturally and simultaneously. The PTX-initiated cytotoxicity attacks tumor cells at tumor sites, meanwhile, the αGC-triggered antitumor immune response emerges at spleen tissue. Different to the case that liposomes are loaded with sole drug, in this concept two therapeutic processes effectively reinforce each other, thereby elevating the tumor therapy efficiency significantly. The data demonstrates that the PTX/αGC-TH-Lip not only possess therapeutic effect against highly malignant B16F10 melanoma tumor, but also adjust the in vivo immune status and induce a more remarkable systemic antitumor immunity that could further suppress the growth of tumor at distant site. This work exhibits the capability of the PTX/αGC-TH-Lip in improving immune-chemotherapy against tumor after systemic administration.

Utilizing G2/M retention effect to enhance tumor accumulation of active targeting nanoparticles.

In recent years, active targeting strategies by ligand modification have emerged to enhance tumor accumulation of NP, but their clinical application was strictly restricted due to the complex preparation procedures, poor stability and serious toxicity. An effective and clinical translational strategy is required to satisfy the current problems. Interestingly, the internalization of NP is intimately related with cell cycle and the expression of receptors is not only related with cancer types but also cell cycle progression. So the cellular uptake of ligand modified NP may be related with cell cycle. However, few investigations were reported about the relationship between cell cycle and the internalization of ligand modified NP. Herein, cellular uptake of folic acid (FA) modified NP after utilizing chemotherapeutic to retain the tumor cells in G2/M phase was studied and a novel strategy was designed to enhance the active targeting effect. In our study, docetaxel (DTX) notably synchronized cells in G2/M phase and pretreatment with DTX highly improved in vitro and in vivo tumor cell targeting effect of FA decorated NP (FANP). Since FA was a most common used tumor active targeting ligand, we believe that this strategy possesses broader prospects in clinical application for its simplicity and effectiveness.

Dual-functionalized liposomal delivery system for solid tumors based on RGD and a pH-responsive antimicrobial peptide.

[D]-H6L9, as a pH-responsive anti-microbial peptide (AMP), has been evidenced by us to be an excellent choice in tumor microenvironment-responsive delivery as it could render liposomes responsive to the acidified tumor microenvironment. However, [D]-H6L9-modified liposomes could not actively target to tumor area. Therefore, integrin αvß3-targeted peptide RGD was co-modified with [D]-H6L9 onto liposomes [(R + D)-Lip] for improved tumor delivery efficiency. Under pH 6.3, (R + D)-Lip could be taken up by C26 cells and C26 tumor spheroids (integrin αvß3-positive) with significantly improved efficiency compared with other groups, which was contributed by both RGD and [D]-H6L9, while RGD did not increase the cellular uptake performance on MCF-7 cells (integrin αvß3-negative). Results showed that RGD could decrease cellular uptake of (R + D)-Lip while [D]-H6L9 could increase it, implying the role of both RGD and [D]-H6L9 in cellular internalization of (R + D)-Lip. On the other hand, (R + D)-Lip could escape the entrapment of lysosomes. PTX-loaded (R + D)-Lip could further increase the cellular toxicity against C26 cells compared with liposomes modified only with RGD and [D]-H6L9 respectively, and achieve remarkable tumor inhibition effect on C26 tumor models.

Dual Receptor Recognizing Cell Penetrating Peptide for Selective Targeting, Efficient Intratumoral Diffusion and Synthesized Anti-Glioma Therapy.

Cell penetrating peptides (CPPs) were widely used for drug delivery to tumor. However, the nonselective in vivo penetration greatly limited the application of CPPs-mediated drug delivery systems. And the treatment of malignant tumors is usually followed by poor prognosis and relapse due to the existence of extravascular core regions of tumor. Thus it is important to endue selective targeting and stronger intratumoral diffusion abilities to CPPs. In this study, an RGD reverse sequence dGR was conjugated to a CPP octa-arginine to form a CendR (R/KXXR/K) motif contained tandem peptide R8-dGR (RRRRRRRRdGR) which could bind to both integrin αvß3 and neuropilin-1 receptors. The dual receptor recognizing peptide R8-dGR displayed increased cellular uptake and efficient penetration ability into glioma spheroids in vitro. The following in vivo studies indicated the active targeting and intratumoral diffusion capabilities of R8-dGR modified liposomes. When paclitaxel was loaded in the liposomes, PTX-R8-dGR-Lip induced the strongest anti-proliferation effect on both tumor cells and cancer stem cells, and inhibited the formation of vasculogenic mimicry channels in vitro. Finally, the R8-dGR liposomal drug delivery system prolonged the medium survival time of intracranial C6 bearing mice by 2.1-fold compared to the untreated group, and achieved an exhaustive anti-glioma therapy including anti-tumor cells, anti-vasculogenic mimicry and anti-brain cancer stem cells. To sum up, all the results demonstrated that R8-dGR was an ideal dual receptor recognizing CPP with selective glioma targeting and efficient intratumoral diffusion, which could be further used to equip drug delivery system for effective glioma therapy.

Significantly enhanced tumor cellular and lysosomal hydroxychloroquine delivery by smart liposomes for optimal autophagy inhibition and improved antitumor efficiency with liposomal doxorubicin.

Hydroxychloroquine (HCQ) inhibits autophagy and therefore can sensitize some cancer cells to chemotherapy, but the high doses required limit its clinical use. Here we show that loading HCQ into liposomes (HCQ/Lip) decorated with a pH-sensitive TH-RGD targeting peptide (HCQ/Lip-TR) can concentrate HCQ in B16F10 tumor cells and lysosomes. HCQ/Lip-TR was efficiently internalized as a result of its ability to bind ITGAV-ITGB3/integrin αvß3 receptors highly expressed on the tumor cell surface and to undergo charge reversal from anionic at pH 7.4 to cationic at pH 6.5. Studies in vitro at pH 6.5 showed that the intracellular HCQ concentration was 35.68-fold higher, and lysosomal HCQ concentration 32.22-fold higher, after treating cultures with HCQ/Lip-TR than after treating them with free HCQ. The corresponding enhancements observed in mice bearing B16F10 tumors were 15.16-fold within tumor cells and 14.10-fold within lysosomes. HCQ/Lip-TR was associated with milder anemia and milder myosuppressive reductions in white blood cell and platelet counts than free HCQ, as well as less accumulation in the small intestine, which may reduce risk of intestinal side effects. In addition, co-delivering HCQ/Lip-TR with either free doxorubicin (DOX) or liposomal DOX improved the ability of DOX to inhibit tumor growth. Biochemical, electron microscopy and immunofluorescence experiments confirmed that HCQ/Lip-TR blocked autophagic flux in tumor cells. Our results suggest that loading HCQ into Lip-TR liposomes may increase the effective concentration of the inhibitor in tumor cells, allowing less toxic doses to be used.

Arginine-Glycine-Aspartic Acid-Modified Lipid-Polymer Hybrid Nanoparticles for Docetaxel Delivery in Glioblastoma Multiforme.

Hybrid nanoparticles consisting of lipids and the biodegradable polymer, poly (D,L-lactide-co-glycolide) (PLGA), were developed for the targeted delivery of the anticancer drug, docetaxel. Transmission electron microscopic observations confirmed the presence of a lipid coating over the polymeric core. Using coumarin-6 as a fluorescent probe, the uptake efficacy of RGD conjugated lipid coated nanoparticles (RGD-L-P) by C6 cells was increased significantly, compared with that of lipid-polymer hybrid nanoparticles (L-P; 2.5-fold higher) or PLGA-nanoparticles (PLGA-P; 1.76-fold higher). The superior tumor spheroid penetration of RGD-L-P indicated that RGD-L-P could target effectively and specifically to C6 cells overexpressing integrin α(v)ß3. The anti-proliferative activity of docetaxel-loaded RGD-L-P against C6 cells was increased 2.69- and 4.13-fold compared with L-P and PLGA-P, respectively. Regarding biodistribution, the strongest brain-localized fluorescence signals were detected in glioblastoma multiforme (GBM)-bearing rats treated with 1,10-Dioctadecyl-3,3,30,30-tetramethylindotricarb-ocyanine iodide (DiR)-loaded RGD-L-P, compared to rats treated with DiR-loaded L-P or PLGA-P. The median survival time of GBM-bearing rats treated with docetaxel-loaded RGD-L-P was 57 days, a fold increase of 1.43, 1.78, 3.35, and 3.56 compared with animals given L-P (P < 0.05), PLGA-P (P < 0.05), Taxotere (P < 0.01) and saline (P < 0.01), respectively. Collectively, these results support RGD-L-P as a promising drug delivery system for the specific targeting and the treatment of GBM.

Multifunctional Tandem Peptide Modified Paclitaxel-Loaded Liposomes for the Treatment of Vasculogenic Mimicry and Cancer Stem Cells in Malignant Glioma.

The chemotherapy of aggressive glioma is usually accompanied by a poor prognosis because of the formation of vasculogenic mimicry (VM) and brain cancer stem cells (BCSCs). VM provided a transporting pathway for nutrients and blood to the extravascular regions of the tumor, and BCSCs were always related to drug resistance and the relapse of glioma. Thus, it is important to evaluate the inhibition effect of antiglioma drug delivery systems on both VM and BCSCs. In this study, paclitaxel-loaded liposomes modified with a multifunctional tandem peptide R8-c(RGD) (R8-c(RGD)-Lip) were used for the treatment of glioma. An in vitro cellular uptake study proved the strongest targeting ability to be that of R8-c(RGD)-Lip to glioma stem cells. Drug loaded R8-c(RGD)-Lip exhibited an efficient antiproliferation effect on BCSCs and could induce the destruction of VM channels in vitro. The following pharmacodynamics study demonstrated that R8-c(RGD)-modified drug-loaded liposomes achieved both anti-VM and anti-BCSC effects in vivo. Finally, no significant cytotoxicity of the blood system or major organs of the drug-loaded liposomes was observed under treatment dosage in the safety evaluation. In conclusion, all of the results proved that R8-c(RGD)-Lip was a safe and efficient antiglioma drug delivery system.

Tumor-targeted paclitaxel delivery and enhanced penetration using TAT-decorated liposomes comprising redox-responsive poly(ethylene glycol).

To combine the advantage of poly(ethylene gylcol) (PEG) for longer circulation and cell-penetrating peptides (CPPs) for efficient cellular uptake, paclitaxel (PTX)-loaded liposomes functionalized with TAT, the most frequently used CPP, and cleavable PEG via a redox-responsive disulfide linker (PTX-C-TAT-LP) were successfully developed here. Under physiological conditions, TAT was shielded by PEG layer and liposomes exhibited a long blood circulation. At tumor site, PEG could be detached in the presence of exogenous reducing agent [glutathione (GSH)] and TAT was exposed to facilitate cell internalization. In the presence of GSH, the liposomal vesicle C-TAT-LP showed increased cellular uptake and improved three-dimensional tumor spheroids penetration in vitro compared with analogous stable shielded liposomes. C-TAT-LP achieved enhanced tumor distribution and demonstrated superior delivery efficiency in vivo. PTX-C-TAT-LP with GSH strongly inhibited the proliferation of murine melanoma B16F1 tumor cells in vitro and in vivo with the tumor inhibition rate being 69.4% on B16F1-bearing mice. In addition, the serum aspartate transaminase level, alanine transaminase level, and creatine kinase level were almost completely within normal range in the PTX-C-TAT-LP with GSH group, revealing PTX-C-TAT-LP with GSH had no obvious drug-related adverse events for liver and heart. Taken together, C-TAT-LP is a promising tumor-targeting drug carrier.

A novel antitumour strategy using bidirectional autophagic vesicles accumulation via initiative induction and the terminal restraint of autophagic flux.

Autophagy is a lysosomal degradation pathway that protects cancer cells from multiple endogenous and extraneous stresses, particularly during the pathogenesis of cancer. An autophagic balance exists in the tumour microenvironment. Appropriate disturbance to this balance may have therapeutic potential. Here, we report a novel antitumour strategy based on an autophagic catastrophic vacuolisation effect in tumour cells. We achieved this effect via initiative induction and the terminal restraint of autophagic flux. The TAT-Beclin 1 peptide (T-B) was constructed for the initiative induction of autophagic flux, whereas hydroxychloroquine (HCQ)-loaded liposomes (HCQ-Lip) were constructed for terminal restraint. We demonstrate that T-B, a new CPP tandem autophagy inducing peptide, effectively activates the autophagy signal at the early stage of the autophagy pathway. HCQ deacidified the lysosome during the final stage of autophagy. We combined T-B and HCQ-Lip to induce autophagic catastrophic vacuolisation and death in several tumour cell lines based on the idea of "broadening sources of income and reducing expenditure". The co-treated group exhibited at least a 1.86-fold greater and up to 5.66-fold greater cytotoxic effect in vitro. In addition, this strategy showed at least a 2.0-fold tumour inhibitory effect compared to the other groups in vivo. Therefore, this bidirectional accumulation of autophagic vesicles exhibited potential efficacy for tumour treatment.

Liposomes Combined an Integrin αvß3-Specific Vector with pH-Responsible Cell-Penetrating Property for Highly Effective Antiglioma Therapy through the Blood-Brain Barrier.

Glioma, one of the most common aggressive malignancies, has the highest mortality in the present world. Delivery of nanocarriers from the systemic circulation to the glioma sites would encounter multiple physiological and biological barriers, such as blood-brain barrier (BBB) and the poor penetration of nanocarriers into the tumor. To circumvent these hurdles, the paclitaxel-loaded liposomes were developed by conjugating with a TR peptide (PTX-TR-Lip), integrin αvß3-specific vector with pH-responsible cell-penetrating property, for transporting drug across the BBB and then delivering into glioma. Surface plasmon resonance (SPR) studies confirmed the very high affinity of TR-Lip and integrin αvß3. In vitro results showed that TR-Lip exhibited strong transport ability across BBB, killed glioma cells and brain cancer stem cells (CSCs), and destroyed the vasculogenic mimicry (VM) channels. In vivo results demonstrated that TR-Lip could better target glioma, and eliminated brain CSCs and the VM channels in tumor tissues. The median survival time of tumor-bearing mice after administering PTX-TR-Lip (45 days) was significantly longer than that after giving free PTX (25.5 days, p < 0.001) or other controls. In conclusion, PTX-TR-Lip would improve the therapeutic efficacy of brain glioma in vitro and in vivo.

A pH-responsive cell-penetrating peptide-modified liposomes with active recognizing of integrin αvß3 for the treatment of melanoma.

The use of pH-responsive cell-penetrating peptides (CPPs) is an attractive strategy for drug delivery in vivo, however, they still could not actively target to the desired sites. Here, we designed a pH-responsive CPP (TR) with the ability of active targeting to integrin αvß3, which was a tandem peptide consisted of active targeting ligand peptide (c(RGDfK)) and pH-responsive CPP (TH). The targeting efficiency of TR with integrin was evaluated by molecular simulation and docking studies. The affinity assays of TR peptide modified liposomes (TR-Lip) at pH7.4 and pH6.5 demonstrated adequately the pH-responsive binding efficacy of TR-Lip with integrin αvß3. The cellular uptake of CFPE-labeled TR-Lip on integrin αvß3-overexpressing B16F10 cells was 41.67-, 30.67-, and 11.90-fold higher than that of CFPE-labeled PEG-, RGD-, and TH-modified liposomes at pH6.5, respectively, suggesting that TR-Lip could not only actively target to αvß3-overexpressing cells compared to TH-Lip, but also significantly increased cellular uptake compared to RGD-Lip. At the concentration of 20µg/mL paclitaxel (PTX), the killing activity of PTX-loaded TR-Lip (PTX-TR-Lip) against B16F10 cells was 1.80-, 1.45-, 1.30-, 1.15-time higher than that of PTX-loaded PEG-, RGD-, TH-modified liposomes and free PTX at pH6.5, respectively. In vivo imaging displayed the maximum accumulation of DiD-labeled TR-Lip at tumor sites compared to the other groups. Tumor inhibition rate of B16F10 tumor-bearing mice treated with PTX-TR-Lip was 85.04%, relative to that of PBS. In B16F10 tumor-bearing mice, PTX-TR-Lip showed significantly higher survival rate compared with the other groups. Collectively, all the results in vitro and in vivo suggested that TR-Lip would be a potential delivery system for PTX to treat integrin αvß3-overexpressing tumor-bearing mice.

Enhanced glioma targeting and penetration by dual-targeting liposome co-modified with T7 and TAT.

The development of a drug delivery strategy that can not only cross the blood-brain barrier (BBB) rapidly, but also target the glioma and reach the core of glioma is essential and important for glioma treatment. To achieve this goal, we established a dual-targeting liposomal system modified with TAT (AYGRKKRRQRRR) and T7 (HAIYPRH), in which the specific ligand T7 could target BBB and brain glioma tumor and the nonspecific ligand TAT could enhance the effect of passing through BBB, and elevate the penetration into the tumor. The dual-targeting effects were evaluated by both in vitro and in vivo experiments. To identify the targeting effect, in vitro cellular uptake and BBB model were performed. Tumor spheroid penetration was performed to evaluate the penetration characteristics of the dual-targeting liposomes. In vivo pharmacokinetic studies were utilized to evaluate the influence of T7 and TAT peptides on the behavior of nanoparticle drug delivery system, and tissue distribution was further utilized to evaluate the glioma-targeting efficiency of the dual-targeting liposomes.

Increased tumor targeted delivery using a multistage liposome system functionalized with RGD, TAT and cleavable PEG.

Though PEGylation has been widely used to enhance the accumulation of liposomes in tumor tissues through enhanced permeability and retention (EPR) effects, it still inhibits cellular uptake and affects intracellular trafficking of carriers. Active targeting molecules displayed better cell selectivity but were shadowed by the poor tumor penetration effect. Cell penetrating peptides could increase the uptake of the carriers but were limited by their non-specificity. Dual-ligand system may possess a synergistic effect and create a more ideal drug delivery effect. Based on the above factors, we designed a multistage liposome system co-modified with RGD, TAT and cleavable PEG, which combined the advantages of PEG, specific ligand and penetrating peptide. The cleavable PEG could increase the stability and circulation time of liposomes during circulation. After the passive extravasation to tumor tissues, the previously hidden dual ligands on the liposomes were exposed in a controlled manner at the tumor site through exogenous administration of a safe reducing agent L-cysteine. The RGD specifically recognized the integrins overexpressed on various malignant tumors and mediated efficient internalization in the synergistic effect of the RGD and TAT. Invitro cellular uptake and 3D tumor spheroids penetration studies demonstrated that the system could not only be selectively and efficiently taken up by cells overexpress ingintegrins but also penetrate the tumor cells to reach the depths of the avascular tumor spheroids. In vivo imaging and fluorescent images of tumor section further demonstrated that this system achieved profoundly improved distribution within tumor tissues, and the RGD and TAT ligands on C-R/T liposomes produced a strong synergistic effect that promoted the uptake of liposomes into cells after the systemic administration of L-cysteine. The results of this study demonstrated a tremendous potential of this multistage liposomes for efficient delivery to tumor tissue and selective internalization into tumor cells.