Chitosan-Based Polyelectrolyte Complexes as Potential Nanoparticulate Carriers: Physicochemical and Biological Characterization

Purpose

To investigate the effect of polyelectrolytes on the formation and physicochemical properties of chitosan nanoparticles (CS-NPs) used for the delivery of an anticancer drug, doxorubicin (DOX).

Method

Three DOX-loaded CS-NPs were formulated with tripolyphosphate (CS-TP/DOX NPs), dextran sulfate (CS-DS/DOX NPs), and hyaluronic acid (CS-HA/DOX NPs) by using ionotropic gelation or complex coacervation.

Results

CS-TP/DOX NPs were the smallest, with an average size of ~100 nm and a narrow size distribution, while CS-DS/DOX and CS-HA/DOX NPs were ~200 nm in size. Transmission electron microscopy clearly showed a spherical shape for all the NPs. The strong binding affinity of DOX for the multiple sulfate groups in DS resulted in a sustained release profile from CS-DS/DOX NPs at pH 7.4, while CS-HA/DOX NPs exhibited faster DOX release. This trend was also present under acidic conditions, where release of DOX was significantly augmented because of polymer protonation. Compared to CS-TP/DOX or CS-DS/DOX NPs, CS-HA/DOX NPs showed superior cellular uptake and cytotoxicity in MCF-7 and A-549 cells, because of their ability to undergo CD44-mediated endocytosis. Pharmacokinetic studies clearly showed that all CS-NPs tested significantly improved DOX plasma circulation time and decreased its elimination rate constant. Consistent with the in vitro release data, CS-DS/DOX NPs exhibited a relatively better DOX plasma profile and enhanced blood circulation, compared to CS-HA/DOX or CS-TP/DOX NPs. Overall, these results demonstrated how NP design can influence their function.

Conclusions

Taken together, CS-based polyelectrolyte complexes could provide a versatile delivery system with enormous potential in the pharmaceutical and biomedical sectors.     

A Multi-Functional Tumor Theranostic Nanoplatform for MRI Guided Photothermal-Chemotherapy

Purpose

To develop a multi-functional theranostic nanoplatform with increased tumor retention, improving antitumor efficacy and decreased side effects of chemotherapy drugs.

Methods

GO@Gd nanocomposites was synthesized via decorating gadolinium (Gd) nanoparticles (GdNP) onto graphene oxide (GO), and then functionalized by polyethylene glycol (PEG2000), folic acid (FA), a widely used tumor targeting molecule, was linked to GO@Gd-PEG, finally, doxorubicin (DOX) was loaded onto GO@Gd-PEG-FA and obtained a tumor-targeting drug delivery system (GO@Gd-PEG-FA/DOX). GO@Gd-PEG-FA/DOX was characterized and explored its theranostic applications both in a cultured MCF-7 cells and tumor-bearing mice.

Results

GO@Gd-PEG-FA/DOX could efficiently cross the cell membranes, lead to more apoptosis and afford higher antitumor efficacy without obvious toxic effects to normal organs owing to its prolonged blood circulation and 7.6-fold higher DOX uptake of tumor than DOX. Besides, GO@Gd-PEG-FA/DOX also served as a powerful photothermal therapy (PTT) agent for thermal ablation of tumor and a strong T1-weighted contrast agent for tumor MRI diagnosis. The multi-functional nanoplatform also could selectively kill cancer cells in highly localized regions via the excellent tumor-targeting and MRI guided PTT abilities.

Conclusions

GO@Gd-PEG-FA/DOX exhibited excellent photothermal-chemotherapeutic efficacy, tumor-targeting property and tumor diagnostic ability.

     

Near-Infrared Light-Sensitive Liposomes for the Enhanced Photothermal Tumor Treatment by the Combination with Chemotherapy

Purpose

To develop a near-infrared (NIR) light-sensitive liposome, which contains hollow gold nanospheres (HAuNS) and doxorubicin (DOX), and evaluate their potential utility for enhancing antitumor activity and controlling drug release.

Methods

The liposomes (DOX&HAuNS-TSL) were designed based on a thermal sensitive liposome (TSL) formulation, and hydrophobically modified HAuNS were attached onto the membrane of the liposomes. The behavior of DOX release from the liposomes was investigated by the dialysis, diffusion in agarose gel and cellular uptake of the drug. The biodistribution of DOX&HAuNS-TSL was assessed by i.v. injection in tumor-bearing nude mice. Antitumor efficacy was evaluated both histologically using excised tissue and intuitively by measuring the tumor size and weight.

Results

Rapid and repetitive DOX release from the liposomes (DOX&HAuNS-TSL), could be readily achieved upon NIR laser irradiation. The treatment of tumor cells with DOX&HAuNS-TSL followed by NIR laser irradiation showed significantly greater cytotoxicity than the treatment with DOX&HAuNS-TSL alone, DOX-TSL alone (chemotherapy alone) and HAuNS-TSL plus NIR laser irradiation (Photothermal ablation, PTA, alone). In vivo antitumor study indicated that the combination of simultaneous photothermal and chemotherapeutic effect mediated by DOX&HAuNS-TSL plus NIR laser presented a significantly higher antitumor efficacy than the PTA alone mediated by HAuNS-TSL plus NIR laser irradiation.

Conclusions

Our study could be as the valuable reference and direction for the clinical application of PTA in tumor therapy.     

Spatiotemporally Controlled Co-delivery of Anti-vasculature Agent and Cytotoxic Drug by Octreotide-Modified Stealth Liposomes

Purpose

Both combretastatin A-4 (CA-4) and doxorubicin (DOX) was loaded in different form in a targeted nanomedicine in order to achieve the active delivery of these two drugs followed by sequentially suppressing tumor vasculature and tumor cells.

Methods

Octreotide-modified stealth liposomes loaded with CA-4 and DOX (Oct-L[CD]) were prepared and characterized. Then in vitro release, cellular uptake, in vitro antitumor effect, pharmacokinetics, in vivo sequential killing effect, in vivo antitumor efficacy against somatostatin receptor (SSTR) positive cells, as well as the action mechanism of such system, were studied.

Results

A rapid release of CA-4 followed by a slow release of DOX was observed in vitro. The active targeted liposomes Oct-L[CD] showed a specific cellular uptake through ligand-receptor interaction and a higher antitumor effect in vitro against SSTR-positive cell line. The in vivo sequential killing effect of such system was found as evidenced by the fast inhibition of blood vessels and slow apoptosis-inducing of tumor cells. Oct-L[CD] also exhibited the strongest antitumor effect in MCF-7 subcutaneous xenograft models.

Conclusions

Oct-modified co-delivery system may have great potential as an effective carrier for cancer therapy.     

Bioactive Lipids-Based pH Sensitive Micelles for Co-Delivery of Doxorubicin and Ceramide to Overcome Multidrug Resistance in Leukemia

Purpose

Construction of a novel PEGylated bioactive lipids-based micelle system for co-delivery of doxorubicin (DOX) and short chain ceramide (C6-ceramide) to overcome multidrug resistance in leukemia.

Methods

The PEGylated bioactive lipids-based micelle system was constructed via electrostatic and hydrophobic interactions among DOX, bioactive lipids PazPC and C6-ceramide. The micellar formulation was characterized in terms of size, zeta potential, stability and release behavior, etc., and in vitro cytotoxicity, in vivo antitumor efficacy and the underlying mechanism were further evaluated.

Results

This novel micellar system showed small size (~15 nm), high drug encapsulation efficiency (>90%), good stability and endosomal acid-triggered release of DOX. Synergistic cytotoxic effects between DOX and bioactive lipid C6-ceramide in P-gp overexpressing drug resistant leukemia P388/ADR cells were observed. The mechanistic studies demonstrated that modulation of drug efflux system and induction of apoptotic effects by lipids were responsible for the synergistic effects between DOX and C6-ceramide in drug resistant leukemia P388/ADR cells. Using an in-vivo P388/ADR leukemia mouse model, the median survival time of the DOX-loaded PEGylated micelles with PazPC and C6-ceramide as major components was significantly greater than that of free DOX and control group.

Conclusions

We developed a novel pH sensitive bioactive lipids-based micellar formulation which could potentially be useful in delivering chemotherapeutic drug DOX and provide a novel strategy to increase the therapeutic index for drug resistant leukemia treatment.     

Near-Infrared Image-Guided Delivery and Controlled Release Using Optimized Thermosensitive Liposomes

Purpose

To engineer optimized near-infrared (NIR) active thermosensitive liposomes to potentially achieve image-guided delivery of chemotherapeutic agents.

Methods

Thermosensitive liposomes were surface-coated with either polyethylene glycol or dextran. Differential scanning calorimetry and calcein release studies were conducted to optimize liposomal release, and flow cytometry was employed to determine the in vitro macrophage uptake of liposomes. Indocyanine green (ICG) was encapsulated as the NIR dye to evaluate the in vivo biodistribution in tumor-bearing mice.

Results

The optimized thermosensitive liposome formulation consists of DPPC, SoyPC, and cholesterol in the 100:50:30 molar ratio. Liposomes with dextran and polyethylene glycol demonstrated similar thermal release properties; however in vitro macrophage uptake was greater with dextran. Non-invasive in vivo NIR imaging showed tumor accumulation of liposomes with both coatings, and ex vivo NIR imaging correlated well with actual ICG concentrations in various organs of healthy mice.

Conclusions

The optimized thermosensitive liposome formulation demonstrated stability at 37?°C and efficient burst release at 40 and 42?°C. Dextran exhibited potential for application as a surface coating in thermosensitive liposome formulations. In vivo studies suggest that liposomal encapsulation of ICG permits reliable, real-time monitoring of liposome biodistribution through non-invasive NIR imaging.     

Novel Core-Interlayer-Shell DOX/ZnPc Co-loaded MSNs@ pH-Sensitive CaP@PEGylated Liposome for Enhanced Synergetic Chemo-Photodynamic Therapy

Purpose

This work was intended to develop novel doxorubicin (DOX)/zinc (II) phthalocyanine (ZnPc) co-loaded mesoporous silica (MSNs)@ calcium phosphate (CaP)@PEGylated liposome nanoparticles (NPs) that could efficiently achieve collaborative anticancer therapy by the combination of photodynamic therapy (PDT) and chemotherapy. The interlayer of CaP could be utilized to achieve pH-triggered controllable drug release, promote the cellular uptake, and induce cell apoptosis to further enhance the anticancer effects.

Methods

MSNs were first synthesized as core particles in which the pores were diffusion-filled with DOX, then the cores were coated by CaP followed by the liposome encapsulation with ZnPc to form the final DOX/ZnPc co-loaded MSNs@CaP@PEGylated liposome.

Results

A core-interlayer-shell MSNs@CaP@PEGylated liposomes was developed as a multifunctional theranostic nanoplatform. In vitro experiment indicated that CaP could not only achieve pH-triggered controllable drug release, promote the cellular uptake of the NPs, but also generate high osmotic pressure in the endo/lysosomes to induce cell apoptosis. Besides, the chemotherapy using DOX and PDT effect was achieved by the photosensitizer ZnPc. Furthermore, the MSNs@CaP@PEGylated liposomes showed outstanding tumor-targeting ability by enhanced permeability and retention (EPR) effect.

Conclusions

The novel prepared MSNs@CaP@PEGylated liposomes could serve as a promising multifunctional theranostic nanoplatform in anticancer treatment by synergic chemo-PDT and superior tumor-targeting ability.

     

Mitochondrial Delivery of Doxorubicin by Triphenylphosphonium-Functionalized Hyperbranched Nanocarriers Results in Rapid and Severe Cytotoxicity

Purpose

To develop a novel hyperbranched polymer-based nanocarrier for efficient drug delivery to cell mitochondria. Also to study for the first time the cytotoxic effect of doxorubicin via mitochondria-specific delivery system.

Methods

We introduced alkyltriphenylphosphonium groups (TPP) to a poly(ethylene imine) hyperbranched polymer (PEI). We harnessed the hydrophobic assembly of these alkylTPP functionalized PEI molecules into ~100 nm diameter nanoparticles (PEI-TPP) and further encapsulated the chemotherapy agent doxorubicin (DOX), to produce the mitotropic nanoparticles PEI-TPP-DOX.

Results

By administering PEI-TPP-DOX to human prostate carcinoma cells DU145, we found that: (i) PEI-TPP-DOX specifically localized at cell mitochondria as revealed by the inherent DOX fluorescence; (ii) in contrast to the slow apoptotic cell death incurred by DOX over the period of days at micromolar concentrations, PEI-TPP-DOX triggered rapid and severe cytotoxicity within few hours of incubation and at submicromolar incubation concentrations. This cytotoxicity was mainly found to be of a necrotic nature, not precluding autophagy related death pathways to a smaller extent.

Conclusions

We have elaborated a versatile mitotropic nanocarrier; furthermore, using this platform, we have developed a mitochondrial-doxorubicin formulation with exceptional cytocidal properties, even in nanomolar concentrations.

Hyaluronic Acid Derivative-Based Self-Assembled Nanoparticles for the Treatment of Melanoma

Purpose

Hyaluronic acid-ceramide (HACE)-based nanoparticles (NPs) were developed for the targeted delivery of doxorubicin (DOX), and their antitumor efficacy for melanoma was evaluated.

Methods

DOX-loaded HACE-based self-assembled NPs were prepared and their physicochemical properties were characterized. The in vitro cytotoxicity of HACE was measured using an MTS-based assay. The cellular uptake efficiency of DOX into mouse melanoma B16F10 cells was assessed by confocal laser scanning microscopy and flow cytometry. Tumor growth and body weight were monitored after the intratumoral and intravenous injection of DOX-loaded NPs into a B16F10 tumor-bearing mouse model.

Results

DOX-loaded NPs, with a mean diameter of ~110?nm, a narrow size distribution, and high drug entrapment efficiency, were prepared. A sustained DOX release pattern was shown, and drug release was enhanced at pH 5.5 compared with pH 7.4. The cytotoxicity of HACE to B16F10 cells was negligible. It was assumed that DOX was taken up into the B16F10 cells through receptor-mediated endocytosis. A significant inhibitory effect was observed on tumor growth, without any serious changes in body weight, after the injection of DOX-loaded NPs into the B16F10 tumor-bearing mouse model.

Conclusions

DOX-loaded HACE-based NPs were successfully developed and their antitumor efficacy against B16F10 tumors was demonstrated.     

Multifunctional Tumor-Targeting Nanocarriers Based on Hyaluronic Acid-Mediated and pH-Sensitive Properties for Efficient Delivery of Docetaxel

Purpose

The objective of this work was to develop a multifunctional tumor-targeting nanocarrier based on the mechanism of CD44-mediated endocytosis and pH-induced drug release to improve the therapeutic efficacy of docetaxel (DTX).

Methods

Hyaluronic acid-coated docetaxel-loaded cholesteryl hemisuccinate vesicles (HA-CHEMS vesicles) were prepared. The physiochemical properties and pH-dependent drug release of HA-CHEMS vesicles were evaluated. The HA-CHEMS vesicles were investigated for CD44-mediated internalization and in vitro cell viability using MCF-7,A549 and L929 cells.In addition,tissue distribution as well as antitumor efficacy was also evaluated in MCF-7 tumor-bearing mouse model.

Results

The particle size and zeta potential of HA-CHEMS vesicles were 131.4?±?6.2 nm and ?13.3?±?0.04 mV,respectively. The in vitro drug release results demonstrated a pH-responsive drug release under different pH conditions. In vitro cell viability tests suggested that the encapsulation of DTX in HA-CHEMS vesicles led to more than 51.6-fold and 46.3-fold improved growth inhibition in MCF-7 and A549 cell lines,respectively compared to Taxotere®. From the cell uptake studies,the coumarin 6-loaded HA-CHEMS vesicles enhanced intracellular fluorescent intensity in the CD44-overexpressing cell line (MCF-7). Biodistribution studies revealed selective accumulation of HA-CHEMS vesicles in the MCF-7 bearing BalB/c nude mice as a result of passive accumulation and active targeting (CD44-mediated endocytosis). Compared to Taxotere®,HA-CHEMS vesicles exhibited higher antitumor activity by reducing tumor volume (P?<?0.05) and drug toxicity,demonstrating the success of the multifunctional targeting delivery.

Conclusions

This work corresponds to the preparation of a multifunctional tumor-targeted delivery system. Our investigation shows that hyaluronan-bearing docetaxel-loaded cholesteryl hemisuccinate vesicles (HA-CHEMS vesicles) is a highly promising therapeutic system,leading to tumor regression after intravenous administration without visible toxicity.     

Photo-Inducible Crosslinked Nanoassemblies for pH-Controlled Drug Release

Purpose

To control drug release from block copolymer nanoassemblies by variation in the degree of photo-crosslinking and inclusion of acid sensitive linkers.

Methods

Poly(ethylene glycol)-poly(aspartate-hydrazide-cinnamate) (PEG-CNM) block copolymers were prepared and conjugated with a model drug, doxorubicin (DOX), through acid sensitive hydrazone linkers. The block copolymers formed photo-inducible, self-assembled nanoassemblies (piSNAs), which were used to produce photo-inducible crosslinked nanoassemblies (piCNAs) through UV crosslinking. The nanoassemblies were characterized to determine particle size, surface charge, pH- and crosslinking-dependent DOX release, in vitro cytotoxicity, and intracellular uptake as a function of photo-crosslinking degree.

Results

Nanoassemblies with varying photo-crosslinking degrees were successfully prepared while retaining particle size and surface charge. Photo-crosslinking caused no noticeable change in DOX release from the nanoassemblies at pH 7.4, but the DOX-loaded nanoassemblies modulated drug release as a function of crosslinking at pH 6.0. The nanoassemblies showed similar cytotoxicity regardless of crosslinking degrees, presumably due to the low cellular uptake and cell nucleus drug accumulation.

Conclusions

Photo-crosslinking is useful to control drug release from pH-sensitive block copolymer nanoassemblies as a function of crosslinking without altering the particle properties, and thus providing unique tools to investigate the pharmaceutical effects of drug release on cellular response.     

Chitooligosaccharides Modified Reduction-Sensitive Liposomes: Enhanced Cytoplasmic Drug Delivery and Osteosarcomas-Tumor Inhibition in Animal Models

Purpose

To investigate the potential of a reduction-sensitive and fusogenic liposomes, enabled by surface-coating with chotooligosaccharides (COS) via a disulfide linker, for tumor-targeted cytoplasmic drug delivery.

Methods

COS (MW2000-5000) were chemically tethered onto the liposomes through a disulfide linker (-SS-) to cholesterol (Chol). Doxorubicin (DOX) was actively loaded in the liposomes. Their reduction-sensitivities, cellular uptake, cytotoxicity, pharmacokinetics and antitumor efficacy were investigated.

Results

The Chol-SS-COS/DOX liposomes (100 nm) had zeta potential of 33.9 mV and high drug loading (13% w/w). The liposomes were stable with minimal drug leakage under physiological conditions but destabilized in the presence of reducing agents, dithiothreitol (DTT) or glutathione (GSH) at 10 mM, the cytosolic level. MTT assay revealed that the cationic Chol-SS-COS/DOX liposomes had higher cytotoxicity to MG63-osteosarcoma cells than non-reduction sensitive liposome (Chol-COS/DOX). Flow cytometry and confocal microscopy revealed that Chol-SS-COS/DOX internalized more efficiently than Chol-COS/DOX with more content to cytoplasm whereas Chol-COS/DOX located around the cell membrane. Chol-SS-COS/DOX preferentially internalized into MG63 cancer cell over LO2 normal liver cells. In rats both liposomes produced a prolonged half-life of DOX by 4 - 5.5 fold (p < 0.001) compared with the DOX solution. Chol-SS-COS/DOX exhibited strong inhibitory effect on tumor growth in MG63 cell-bearing nude mice (n = 6), and extended animal survival rate.

Conclusions

Reduction-responsive Chol-SS-COS liposomes may be an excellent platform for cytoplasmic delivery of anticancer drugs. Conjugation of liposomes with COS enhanced tumor cell uptake, antitumor effect and survival rate in animal models.

     

PEGylated Multi-Walled Carbon Nanotubes for Encapsulation and Sustained Release of Oxaliplatin

Purpose

To develop PEGylated multi-walled carbon nanotubes as a sustained release drug delivery system.

Methods

Oxaliplatin was incorporated into inner cavity of PEGylated multi-walled carbon nanotubes (MWCNT-PEG) using nano-extraction. Oxaliplatin release rates from MWCNT-PEG-Oxaliplatin were investigated using dialysis tubing. Cytotoxicity of oxaliplatin, MWCNT-Oxaliplatin and MWCNT-PEG-Oxaliplatin were evaluated in HT29 cell by MTT assay, Pt-DNA adducts formation, γ-H2AX formation and cell apoptosis assay.

Results

Loading of oxaliplatin into MWCNT-PEG was ~43.6%. Sustained release occurred to MWCNT-PEG-Oxaliplatin, with only 34% of oxaliplatin released into medium within 6 h. In MTT assay, MWCNT-PEG-Oxaliplatin showed slightly decreased cytotoxic effect when cell viability was assessed at 12 and 24 h. A drastic increase of cytotoxicity was found when cell viability was assessed at 48 and 96 h. Pt-DNA adducts formation, γ-H2AX formation and cell apoptosis assay results showed the same trend as the MTT assay, suggesting sustained-release for MWCNT-Oxaliplatin and MWCNT-PEG-Oxaliplatin formulations.

Conclusions

PEGylated multi-walled carbon nanotubes can be used as sustained release drug delivery system, thus remarkably improving cytotoxicity of oxaliplatin on HT-29 cells.     

Stability Influences the Biodistribution, Toxicity, and Anti-tumor Activity of Doxorubicin Encapsulated in PEG-PE Micelles in Mice

Purpose

To investigate the influences of stability of doxorubicin (DOX) retained in PEG-PE/HSPC micelles on its biodistribution, toxicity and anti-tumor activity in mice.

Methods

We incorporated HSPC into PEG-PE micelles at various molar ratios by a self-assembly procedure. Micelles were characterized by dynamic light scattering, transmission electron microscope, atomic force microscopy. Agarose gel electrophoresis assay was used to detect stable retention of DOX in micellar preparations. Biodistribution, toxicity and anti-tumor activity of doxorubicin encapsulated in PEG-PE/HSPC micelles in mice were investigated.

Results

HSPC incorporation not only changed the size and shape of PEG-PE micelles, but also decreased the ability of DOX stable retained in PEG-PE micelles, resulting in a great discrepancy in biodistribution, toxicity and anti-tumor activity among micellar DOX preparations. DOX encapsulated in PEG-PE micelles (M₁-DOX), with narrower size distribution and greater stability, demonstrated better cytotoxicity in vitro and low systemic toxicity with superior anti-tumor metastasis activity in vivo.

Conclusions

Encapsulation of DOX into PEG-PE micelles showed the best therapeutic activity and lowest systemic toxicity compared to other HSPC-incorporated PEG-PE micellar preparations. Stable retention of drugs within micelles is important and is determined by compatibility between drugs and polymer blocks.     

Drug Release Patterns and Cytotoxicity of PEG-poly(aspartate) Block Copolymer Micelles in Cancer Cells

Purpose

To test physicochemical and biological properties of PEG-poly(aspartate) [PEG-p(Asp)] block copolymer micelles entrapping doxorubicin hydrochloride (DOX) through ionic interaction.

Methods

PEG-p(Asp) was synthesized from 5?kDa PEG and 20 Asp units. Carboxyl groups of p(Asp) were present as benzyl ester [PEG-p(Asp/Bz)], sodium salt [PEG-p(Asp/Na)] or free acid [PEG-p(Asp/H)]. Block copolymers and DOX were mixed at various ratios to prepare polymer micelles, which were subsequently characterized to determine particle size, drug loading and release patterns, and cytotoxicity against prostate (PC3 and DU145) and lung (A549) cancer cell lines.

Results

PEG-p(Asp/Bz), Na- and H-micelles entrapped 1.1, 56.8 and 40.6?wt.% of DOX, respectively. Na- and H-micelles (<100?nm) showed time-dependent DOX release at pH 7.4, which was accelerated at pH 5.0. Na-micelles were most stable at pH 7.4, retaining 31.8% of initial DOX for 48?h. Cytotoxicity of Na-micelles was 23.2% (A549), 28.5% (PC3) and 45.9% (DU145) more effective than free DOX.

Conclusion

Ionic interaction appeared to entrap DOX efficiently in polymer micelles from PEG-p(Asp) block copolymers. Polymer micelles possessing counter ions (Na) of DOX in the core were the most stable, releasing drugs for prolonged time in a pH-dependent manner, and suppressing cancer cells effectively.     

Pharmaceutical Differences Between Block Copolymer Self-Assembled and Cross-Linked Nanoassemblies as Carriers for Tunable Drug Release

Purpose

To identify the effects of cross-linkers and drug-binding linkers on physicochemical and biological properties of polymer nanoassembly drug carriers.

Methods

Four types of polymer nanoassemblies were synthesized from poly(ethylene glycol)-poly(aspartate) [PEG-p(Asp)] block copolymers: self-assembled nanoassemblies (SNAs) and cross-linked nanoassemblies (CNAs) to each of which an anticancer drug doxorubicin (DOX) was loaded by either physical entrapment or chemical conjugation (through acid-sensitive hydrazone linkers).

Results

Drug loading in nanoassemblies was 27?~?56% by weight. The particle size of SNA changed after drug and drug-binding linker entrapment (20?~?100 nm), whereas CNAs remained 30?~?40 nm. Drug release rates were fine-tunable by using amide cross-linkers and hydrazone drug-binding linkers in combination. In vitro cytotoxicity assays using a human lung cancer A549 cell line revealed that DOX-loaded nanoassemblies were equally potent as free DOX with a wide range of drug release half-life (t_1/2?=?3.24?~?18.48 h, at pH 5.0), but 5 times less effective when t_1/2?=?44.52 h.

Conclusion

Nanoassemblies that incorporate cross-linkers and drug-binding linkers in combination have pharmaceutical advantages such as uniform particle size, physicochemical stability, fine-tunable drug release rates, and maximum cytotoxicity of entrapped drug payloads.     

Biodegradable Polymersomes as Nanocarriers for Doxorubicin Hydrochloride: Enhanced Cytotoxicity in MCF-7/ADR Cells and Prolonged Blood Circulation

Purpose

DOX is one of the most potent anticancer drugs. But its short half-life and the occurrence of multi-drug resistance (MDR) markedly limit its clinical application. To solve these problems, we develop DOX loaded polymersomes (DOX polymersomes).

Methods

An methoxy poly(ethylene glycol)-b-poly(epsilon-caprolactone) (mPEG-b-PCL) copolymer was synthesized and used to prepare DOX polymersomes. The pharmaceutical properties of DOX polymersomes were characterized. The in vitro release profile of DOX from polymersomes was investigated. The in vitro cytotoxicity and cell uptake studies were performed on MCF-7 and MCF-7/ADR cells. The in vivo pharmacokinetic profiles were investigated on Sprague–Dawley rats.

Results

DOX polymersomes had a nano-scale particle size of about 60 nm with a hydrophobic membrane about 10 nm in thickness. Release of DOX from the polymersomes took place in a sustained manner. Cell experiments showed DOX polymersomes enhanced the cytotoxicity and the intracellular accumulation of DOX in MCF-7/ADR cells, compared with free DOX. In vivo pharmacokinetic study showed the DOX polymersomes increased the bioavailability and prolonged the circulation time in rats.

Conclusions

The entrapment of DOX in biodegradable polymersomes could enhance cytotoxicity in MCF-7/ADR cells and improve its in vivo pharmacokinetic profile.

     

Up-regulating Blood Brain Barrier Permeability of Nanoparticles via Multivalent Effect

Purpose

To investigate the multivalent effect for up-regulating the intracerebral delivery of nanoparticles via receptor-mediated transcytosis.

Methods

Nanoparticles labeled with near-infrared (NIR) fluorophore and different numbers of angiopep-2 peptides that specifically target low-density lipoprotein receptor-related protein (LRP) on the brain capillary endothelial cells were developed. Bio-distribution studies quantified the intracerebral uptakes of these nanoparticles at 2 and 24 h after intravenous injection. In vivo NIR fluorescence imaging, ex vivo autoradiographic imaging and 3D reconstructed NIR fluorescence imaging revealed the nanoparticle distribution pattern in brain. Fluorescence microscopic imaging identified the nanoparticle locations at the cellular level.

Results

The multimetirc association between the angiopep-2 peptides labeled on the nanoparticle and the LRP receptors on the brain capillary endothelial cells significantly increased the intracerebral uptake of the nanoparticles. Nanoparticle Den-Angio4 labeled four angiopep-2 peptides achieved the highest BBB traverse efficacy. After penetrating the BBB, Den-Angio4 distributed heterogeneously and mainly located at hippocampus, striatum and cerebellum in the brains.

Conclusions

The multivalent effect significantly enhances the BBB permeability of nanoparticles. Den-Angio4 as a nanoparticle prototype provides a two order targeted strategy for diagnosis or treatment of central nerver system diseases by first traversing the BBB via receptor-mediated endocytosis and secondly targeting the leisions with high receptor expression level.     

Thermo-Sensitive Liposome co-Loaded of Vincristine and Doxorubicin Based on Their Similar Physicochemical Properties had Synergism on Tumor Treatment

Purpose

To develop vincristine (VCR) and doxorubicin (DOX) co-encapsulated thermo-sensitive liposomes (VD-TSL) against drug resistance, with increased tumor inhibition rate and decreased system toxicity, improving drug targeting efficiency upon mild hyperthermia (HT) in solid tumor.

Methods

Based on similar physicochemical properties, VCR and DOX were co-loaded in TSL with pH gradient active loading method and characterized. The time-dependent drug release profiles at 37 and 42°C were assessed by HPLC. Then we analysed the phospholipids in filtrate after ultrafiltration and studied VD-TSL stability in mimic in vivo conditions and long-time storage conditions (4°C and ?20°C). Cytotoxic effect was studied on PANC and sw-620 using MTT. Intracellular drug delivery was studied by confocal microscopy on HT-1080. In vivo imaging of TSL pharmacokinetic and biodistribution was performed on MCF-7 tumor-bearing nude mice. And therapeutic efficacy on these xenograft models were followed under HT.

Results

VD-TSL had excellent particle distribution (about 90 nm), high entrapment efficiency (>95%), obvious thermo-sensitive property, and good stability. MTT proved VD-TSL had strongest cell lethality compared with other formulations. Confocal microscopy demonstrated specific accumulation of drugs in tumor cells. In vivo imaging proved the targeting efficiency of TSL under hyperthermia. Then therapeutic efficacy revealed synergism of VCR and DOX co-loaded in TSL, together with HT.

Conclusion

VD-TSL could increase drug efficacy and decrease system toxicity, by making good use of synergism of VCR and DOX, as well as high targeting efficiency of TSL.