Glucose-Sensitive Liposomes Incorporating Hydrophobically Modified Glucose Oxidase

Glucose-sensitive liposomes were prepared by incorporating hydrophobically modified glucose oxidase (EC 1.1.3.4.) into the liposomal bilayer of dioleoylphosphatidylethanolamine and cholesteryl hemisuccinate. For the release test, calcein, a fluorescence marker, was entrapped in the liposomes. The liposomes were stable under neutral conditions in terms of calcein release but an extensive release was observed under acidic conditions. In the experiment of glucose concentration-dependent calcein release, no release was observed for 180 min when the suspension of liposome was free of glucose. With a glucose concentration of 50 mg/dL, no appreciable amount of calcein was released for the first 20 min, and then the release rate was accelerated. At 200 mg/dL glucose concentration which is diagnostic and indicative for insulin-dependent diabetes, the lag time of calcein release became shorter and a faster response was obtained. When glucose concentration further increased to 400 mg/dL, the calcein release rate and the degree of release in 180 min were almost the same as the values when the glucose concentration was 200 mg/dL. The glucose concentration-dependent release is due to pH change, since the suspension of liposomes became acidic during the release experiments.     

Gd(¿)-DOTA-modified sonosensitive liposomes for ultrasound-triggered release and MR imaging

ABSTRACT: Ultrasound-sensitive (sonosensitive) liposomes for tumor targeting have been studied in order to increase the antitumor efficacy of drugs and decrease the associated severe side effects. Liposomal contrast agents having Gd(III) are known as a nano-contrast agent system for the efficient and selective delivery of contrast agents into pathological sites. The objective of this study was to prepare Gd(III)-DOTA-modified sonosensitive liposomes (GdSL), which could deliver a model drug, doxorubicin (DOX), to a specific site and, at the same time, be capable of magnetic resonance (MR) imaging. The GdSL was prepared using synthesized Gd(III)-DOTA-1,2-distearoyl-sn-glycero-3-phosphoethanolamine lipid. Sonosensitivity of GdSL to 20-kHz ultrasound induced 33% to 40% of DOX release. The relaxivities (r1) of GdSL were 6.6 to 7.8 mM[MINUS SIGN]1 s[MINUS SIGN]1, which were higher than that of MR-bester[REGISTERED SIGN]. Intracellular uptake properties of GdSL were evaluated according to the intensity of ultrasound. Intracellular uptake of DOX for ultrasound-triggered GdSL was higher than that for non-ultrasound-triggered GdSL. The results of our study suggest that the paramagnetic and sonosensitive liposomes, GdSL, may provide a versatile platform for molecular imaging and targeted drug delivery.     

Egg phosphatidylcholine and dioleoylphosphatidylethanolamine liposomes containing acid proteinoid: Comparison of pH‐sensitivity

pH‐Sensitive liposomes were prepared by modifying the surfaces of egg phosphatidylcholine (EPC) liposomes and dioleoylphosphatidylethanolamine (DOPE) liposomes with an acidic proteinoid. The acidic proteinoid (Prot AL) was prepared by a melt‐condensation of aspartic acid and leucine (98.5:1.5 mol/mol). The maximum amount of Prot AL accommodated by EPC liposomes without loss of the fluorescence quenching of calcein occurred when the ratio of Prot AL to EPC was 1:2. The EPC liposomes exhibited pH‐dependent release but the degree of release in 5 min was less than 10% in the range of pH 6.0–8.0. A marked increase in release was observed at pH 5.5 and the degree of release was about 38%. Acidification‐induced contraction of Prot AL may impose a mechanical stress on the liposomal membrane, deforming and demaging the membrane. On the other hand, a high fluorescence quenching, more than 60%, was obtained when the ratio of Prot AL to DOPE was 5.5:10. The pH‐sensitivity of DOPE liposomes bearing the proteinoid was much higher than that of egg PC liposomes bearing the same proteinoid. Following the changes in the size with varying pH, DOPE liposomes seemed to be disintegrated.     

Fluorescent Silica Nanoparticles Targeting Mitochondria: Trafficking in Myeloid Cells and Application as Doxorubicin Delivery System in Breast Cancer Cells

Fluorescent silica nanoparticles (SiNPs) appear to be a promising imaging platform, showing a specific subcellular localization. In the present study, we first investigated their preferential mitochondrial targeting in myeloid cells, by flow cytometry, confocal microscopy and TEM on both cells and isolated mitochondria, to acquire knowledge in imaging combined with therapeutic applications. Then, we conjugated SiNPs to one of the most used anticancer drugs, doxorubicin (DOX). As an anticancer agent, DOX has high efficacy but also an elevated systemic toxicity, causing multiple side effects. Nanostructures are usually employed to increase the drug circulation time and accumulation in target tissues, reducing undesired cytotoxicity. We tested these functionalized SiNPs (DOX-NPs) on breast cancer cell line MCF-7. We evaluated DOX-NP cytotoxicity, the effect on the cell cycle and on the expression of CD44 antigen, a molecule involved in adhesion and in tumor invasion, comparing DOX-NP to free DOX and stand-alone SiNPs. We found a specific ability to release a minor amount of CD44+ extracellular vesicles (EVs), from both CD81 negative and CD81 positive pools. Modulating the levels of CD44 at the cell surface in cancer cells is thus of great importance for disrupting the signaling pathways that favor tumor progression.     

Preparation and efficacy of tumor vasculature‐targeted doxorubicin cationic liposomes coated by N‐trimethyl chitosan

Cationic liposomes (CLs) can accumulate in tumor vascular endothelial cells (VECs) to show high selective targeting ability. Therefore, chemotherapeutic agent‐loaded CLs are considered as new therapeutic vehicles to enhance the treatment efficacy. This study investigated the effect of N‐trimethyl chitosan (TMC), one of derivatives of chitosan with positive charge determined by its degree of quaternization (DQ), on preparing doxorubicin (DOX)‐loaded CLs. TMCs with various DQ, i.e., 20% (TMC20), 40% (TMC40), and 60% (TMC60) were synthesized and characterized by ¹HNMR. DOX‐loaded liposomes (DOXL) were prepared by ammonium sulfate gradients followed by TMC‐coating to obtain TMC‐coated DOXL with various positive surface charges. The morphology, size, ζ‐potential and drug release in vitro of TMC‐coated DOXL were studied compared with those of DOXL. Human umbilical vein endothelial cells (HUVECs) as cell model, the vascular targeting ability of TMC‐coated DOXL was evaluated in vitro. A solid tumor, formed by implantationmurine hepatoma cells (H₂₂) into mice, as tumor model, the tumor inhibition rate and tumor histological sections stained by HE of TMC‐coated DOXL group were researched compared with those of free DOX and DOXL group. It was found that with the increase of TMC's DQ, the positive surface charge of TMC‐coated DOXL was enhanced accordingly, which had little effect on DOX release in vitro while led to the significant increase of DOX uptake by HUVECs in vitro and the treatment effect on solid tumor in vivo. Especially, TMC‐coated DOXL showed better targeting ability to the nuclei compared with free DOX and DOXL, which could further enhance the efficacy of DOX in vivo. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Oleanolic acid and ursolic acid stabilize liposomal membranes

The effects of oleanolic acid (OA) and ursolic acid (UA) on the fluidity and stability of dipalmitoyl phosphatidylcholine (DPPC) liposomal membrane were monitored by measuring the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene labeled in the liposomal membrane and the leakage of calcein from the probe-encapsulated liposomes. The experiments with the liposomes made of DPPC and OA or UA showed that OA and UA exhibited a moderate fluidity-modulating effect for the liquid-crystalline liposomal membrane, and a strong condensing effect for both crystalline and liquid-crystalline liposomal membranes. Their effects were comparable to those of cholesterol. These results suggest that their fluidity-modulating and condensing effects might have some implications in their biological functions.     

Influence of Liposomes’ and Lipoplexes’ Physicochemical Characteristics on Their Uptake Rate and Mechanisms by the Placenta

Pregnant women are still considered as drug orphans. Developing new medications for pregnancy complications is an urgent need. Nanomedicines seem to be a promising approach to control the biodistribution of drugs to ensure both the mother’s and the fetus’ safety. Understanding the interaction between nanoparticles and the placental barrier is a key factor to the success of the development of nanomedicines for pregnant women. In this study, we evaluated the behavior of fluorescent PEGylated liposomes and lipoplexes in human placental tissue using in vitro and ex vivo models, BeWo cell culture and suspended villous placental explants, respectively. Fluorescent based analytical tools such as Fluorescence activated cells sorting (FACS), confocal microscopy and HPLC coupled to fluorescence detection were used to assess liposomes penetration and their endocytosis mechanisms in the placenta. First, no influence of the PEGylation density was observed on the cellular internalization of liposomal formulations using both models. The comparison between neutral and cationic liposomes exhibits a significant higher internalization of the cationic formulation compared to the neutral ones. In addition, the HPLC quantification of the fluorescent liposomes in human villous explants demonstrated an increase of cationic liposomes uptake with increasing incubation concentrations. Similar uptake of cationic liposomes and lipoplexes, containing the same cationic lipid, the DMAPAP but with an overall neutral surface charge, was observed and evidenced the higher effect of composition than charge surface on trophoblast penetration. Moreover, both cationic liposomes and lipoplexes exhibited an endocytosis mechanism of internalization via pathways implicating dynamin. These data highlight the key role of the liposome’s lipid composition and the possibility to modulate their internalization in the placenta by adjusting their design.     

Carbohydrate – lipid conjugates for targeted drug and gene delivery

The role of macrophages in the uptake and processing of liposomes evident from the increased deposition of liposomal content in cells. It has been reported that macrophages may serve as a secondary drug carrier for the delivery of liposomal drugs. The uptake of liposomal content by macrophages can be promoted by incorporation of ligands capable of interacting with macrophage surface receptors. Therefore, carbohydrate‐based molecules for targeted drug and gene delivery must be developed for rational therapy. In this article, we report the synthesis of glycolipid conjugates for applications in liposomal drug delivery systems and for targeting drugs and genes to receptors.     

Simple Fabrication of Glutathione-Responsive PEGylated Micellar Nanocarriers for Dual Drugs Delivery

The authors report a feasible simple method to fabricate two kinds of micellar nanocarriers (MPEG-SS-CPT/DOX) with polyethylene glycol (PEG) based on the self-assembly of glutathione (GSH)-responsive amphiphilic PEGylated polymers (MPEG-SS-CPT) in free doxorubicin (DOX) solution, which could carry two anticancer drugs of camptothecin (CPT) and DOX toward cancer cells together. In in vitro release studies, the micelles of MPEG-SS-CPT/DOX could undergo the triggered disassembly to release CPT and DOX under GSH stimulus much faster than without GSH. Furthermore, the MPEG-SS-CPT nanocarriers could release CPT with no change of its original structure after degradation. From the experiments of loading and release of drugs, the cell viability assay, cellular uptake, and flow cytometry studies, it was found that the fibrous micelles modified by PEG with a molecular weight of 350 had greater potential in the field of drug delivery than the other with a molecular weight of 1900.     

Description of Release Process of Doxorubicin from Modified Carbon Nanotubes

The article discusses the release process of doxorubicin hydrochloride (DOX) from multi-wall carbon nanotubes (MWCNTs). The studies described a probable mechanism of release and actions between the surface of functionalized MWCNTs and anticancer drugs. The surface of carbon nanotubes (CNTs) has been modified via treatment in nitric acid to optimize the adsorption and release process. The modification efficiency and physicochemical properties of the MWCNTs+DOX system were analyzed by using SEM, TEM, EDS, FTIR, Raman Spectroscopy and UV-Vis methods. Based on computer simulations at pH 7.4 and the experiment at pH 5.4, the kinetics and the mechanism of DOX release from MWNT were discussed. It has been experimentally observed that the acidic pH (5.4) is appropriate for the efficient release of the drug from CNTs. It was noted that under acidic pH conditions, which is typical for the tumour microenvironment almost 90% of the drug was released in a relatively short time. The kinetics models based on different mathematical functions were used to describe the release mechanism of drugs from MWCNTs. Our studies indicated that the best fit of experimental kinetic curves of release has been observed for the Power-law model and the fitted parameters suggest that the drug release mechanism of DOX from MWCNTs is controlled by Fickian diffusion. Molecular dynamics simulations, on the other hand, have shown that in a neutral pH solution, which is close to the blood pH, the release process does not occur keeping the aggregation level constant. The presented studies have shown that MWCNTs are promising carriers of anticancer drugs that, depending on the surface modification, can exhibit different adsorption mechanisms and release.     

Surface modified cellulose nanocrystalline hybrids actualizing efficient and precise delivery of doxorubicin into nucleus with: In vitro and in vivo evaluation

Rod-like-shape nanomedicines with the ability of lysosomal pH-controlled drug release can precisely deliver doxorubicin (DOX) into its target, nucleus, and can fully exert its anticancer effect. Taking advantage of their large specific surface area, cellulose nanocrystals (CNCs) were used to fabricate pH-responsive DOX-loaded rod-like shaped hybrids nanomedicines: cis-aconityl-doxorubicin (CAD)@polyethylenimine (PEI)@CNCs (CAD@PEI@CNCs) via layer-by-layer (LbL) assembly. In vitro, CAD@PEI@CNCs hybrids displayed rod-like shape, high drug loading content, lysosomal pH-controlled drug release, efficient and precise doxorubicin (DOX) delivering into the nucleus. Moreover, the cellular uptake of CAD@PEI@CNCs hybrids was 20.9 folds higher than that of DOX·HCl against A549 cells. The cytotoxicity of CAD@PEI@CNCs hybrids was much higher than that of DOX·HCl and the pH-irresponsive hybrids against A549 cell. In vivo, CAD@PEI@CNCs hybrids exhibited good antitumor effect: (42.0 ± 6)% inhibition rate and few harms to the nude mice. Altogether, rod-like shaped pH-responsive CAD@PEI@CNCs hybrids nanomedicines could efficiently overcome the vascular and tumor barriers, and precisely deliver DOX to nucleus to convert DOX antitumor effects. These results indicate that CAD@PEI@CNCs have great potential to act as advanced nanomedicines with enhanced delivery efficiency and therapeutic efficiency.     

Acid-Sphingomyelinase Triggered Fluorescently Labeled Sphingomyelin Containing Liposomes in Tumor Diagnosis after Radiation-Induced Stress

In liposomal delivery, a big question is how to release the loaded material into the correct place. Here, we will test the targeting and release abilities of our sphingomyelin-consisting liposome. A change in release parameters can be observed when sphingomyelin-containing liposome is treated with sphingomyelinase enzyme. Sphingomyelinase is known to be endogenously released from the different cells in stress situations. We assume the effective enzyme treatment will weaken the liposome making it also leakier. To test the release abilities of the SM-liposome, we developed several fluorescence-based experiments. In in vitro studies, we used molecular quenching to study the sphingomyelinase enzyme-based release from the liposomes. We could show that the enzyme treatment releases loaded fluorescent markers from sphingomyelin-containing liposomes. Moreover, the release correlated with used enzymatic activities. We studied whether the stress-related enzyme expression is increased if the cells are treated with radiation as a stress inducer. It appeared that the radiation caused increased enzymatic activity. We studied our liposomes’ biodistribution in the animal tumor model when the tumor was under radiation stress. Increased targeting of the fluorescent marker loaded to our liposomes could be found on the site of cancer. The liposomal targeting in vivo could be improved by radiation. Based on our studies, we propose sphingomyelin-containing liposomes can be used as a controlled release system sensitive to cell stress.     

Shikonin‐loaded liposomes as a new drug delivery system: Physicochemical characterization and in vitro cytotoxicity

Alkannin and shikonin are naturally occurring hydroxynaphthoquinones with a well‐established spectrum of wound healing, antimicrobial, anti‐inflammatory, and antioxidant activities. Recently, extensive scientific effort has been focused on their effectiveness on several tumors and mechanism(s) of antitumor activity. Liposomes have been proved as adequate drug carriers offering significant advantages over conventional formulations, such as controlled release and targeted drug delivery, leading to the appearance of several liposomal formulations in the market, some of them concerning anticancer drugs. The aim of the present study was to prepare shikonin‐loaded liposomes for the first time in order to enhance shikonin therapeutic index. An optimized technique based on the thin film hydration method was developed and liposomes characterization was performed in terms of their physicochemical characteristics, drug entrapment efficiency, and release profile. Results indicated the successful incorporation of shikonin into liposomes, using both 1,2‐dipalmitoylphosphatidylcholine and egg phosphatidylcholine lipids. Liposomes presented good physicochemical characteristics, high entrapment efficiency and satisfactory in vitro release profile. In vitro cytotoxicity of liposomes was additionally tested against three human cancer cell lines (breast, glioma, and non‐small cell lung cancer) showing a moderate growth inhibitory activity. Practical applications: Shikonin is a naturally occurring hydroxynaphthoquinone and extensive scientific research (in vitro, in vivo, and clinical trials) has been conducted during the last years, focusing on its effectiveness on several tumors and mechanism(s) of antitumor action. The purpose of this work was to prepare and characterize shikonin‐loaded liposomes as a new drug delivery system for shikonin. Liposomal formulations provide significant advantages over conventional dosage forms, such as controlled release and targeted drug delivery for anticancer agents. Thus, liposomes could reduce shikonin's side effects, enhance selectivity to cancer cells and protect shikonin from internal biotransformations and instability matters (oxidization and polymerization). Furthermore, liposomal delivery helps overcome the low aqueous solubility of shikonin, which is the major barrier to its oral and internal administration, since it cannot be dissolved and further absorbed from the receptor.     

Hollow superparamagnetic iron oxide nanoshells as a hydrophobic anticancer drug carrier: intracelluar pH-dependent drug release and enhanced cytotoxicity

With curcumin and doxorubicin (DOX) base as model drugs, intracellular delivery of hydrophobic anticancer drugs by hollow structured superparamagnetic iron oxide (SPIO) nanoshells (hydrodynamic diameter: 191.9 ± 2.6 nm) was studied in glioblastoma U-87 MG cells. SPIO nanoshell-based encapsulation provided a stable aqueous dispersion of the curcumin. After the SPIO nanoshells were internalized by U-87 MG cells, they localized at the acidic compartments of endosomes and lysosomes. In endosome/lysosome-mimicking buffers with a pH of 4.5-5.5, pH-dependent drug release was observed from curcumin or DOX loaded SPIO nanoshells (curcumin/SPIO or DOX/SPIO). Compared with the free drug, the intracellular curcumin content delivered via curcumin/SPIO was 30 fold higher. Increased intracellular drug content for DOX base delivered via DOX/SPIO was also confirmed, along with a fast intracellular DOX release that was attributed to its protonation in the acidic environment. DOX/SPIO enhanced caspase-3 activity by twofold compared with free DOX base. The concentration that induced 50% cytotoxic effect (CC(50)) was 0.05 ± 0.03 μg ml(-1) for DOX/SPIO, while it was 0.13 ± 0.02 μg ml(-1) for free DOX base. These results suggested SPIO nanoshells might be a promising intracellular carrier for hydrophobic anticancer drugs.     

血小板膜伪装介孔聚多巴胺纳米药物传递系统的制备及应用

以三甲基苯为模板剂,采用一锅法制备了具有介孔结构的聚多巴胺纳米粒子(MPDA).通过静电吸附负载盐酸阿霉素(DOX),通过血小板膜(PLTM)仿生伪装得到PLTM-DOX@MPDA纳米粒子.采用TEM、纳米粒度分析仪、BET和UV-Vis对纳米粒子的性质、形貌和粒径进行表征.结果表明,MPDA表面具有清晰的介孔结构,经PLTM包裹后的PLTM-DOX@MPDA平均粒径约为184 nm.MPDA孔径主要分布于45 nm左右,孔容为0.6232 cm3/g,比表面积高达61.181 m2/g,该介孔结构支持MPDA作为高效的药物传递系统.体外释药、体外细胞摄取和体外细胞毒性实验结果表明,PLTM-DOX@MPDA具有pH响应性控制药物释放,可以实现药物缓释,可以避免巨噬细胞吞噬并且主动靶向癌细胞,可显著提高DOX对人乳腺癌细胞(MDA-MB-231)细胞的杀伤作用.     

Retention of Eucalyptol,a Natural Volatile Insecticide,in Delivery Systems Based on Hydroxypropyl‐β‐Cyclodextrin and Liposomes

Eucalyptol (Euc) is a natural monoterpene with insecticide effects. Being highly volatile and sensitive to ambient conditions, its encapsulation would enlarge its application. Euc‐loaded conventional liposomes (CL), cyclodextrin/drug inclusion complex, and drug‐in‐cyclodextrin‐in‐liposomes (DCL) are prepared to protect Euc from degradation, reduce its evaporation, and provide its controlled release. The liposomal suspension is freeze‐dried using hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) as cryoprotectant. The liposomes are characterized before and after freeze‐drying. The effect of Euc on the fluidity of liposomal membrane is also examined. A release study of Euc from delivery systems, in powder and reconstituted forms, is performed by multiple head extraction at 60 °C after 6 months of storage at 4 °C. CL and DCL suspensions are homogeneous, show nanometric vesicles size, spherical shape, and negative surface charge before and after freeze‐drying. Moreover, HP‐β‐CD does not affect the fluidity of liposomes. CL formulations present a weak encapsulation for Euc. The loading capacity of eucalyptol in DCL is 38 times higher than that in CL formulation. In addition, freeze‐dried DCL and HP‐β‐CD/Euc inclusion complex show a higher retention of eucalyptol than CL delivery system. Both carrier systems HP‐β‐CD/Euc and Euc‐loaded DCL decrease Euc evaporation and improve its retention. Practical Applications: Eucalyptol is a natural insecticide. It is highly volatile and poorly soluble in water. To enlarge its application, its encapsulation in three delivery systems (conventional liposomes, cyclodextrin/drug inclusion complex, combined system composed of cyclodextrin inclusion complex and liposome) is studied. In this paper it is proved that cyclodextrin/eucalyptol inclusion complex and eucalyptol‐in‐cyclodextrin‐in‐liposome are effective delivery systems for encalyptol encapsulation, retention, and release.     

Multifunctional Containers from Anionic Liposomes and Cationic Polymers/Colloids

The study describes an “open” method for concentrating anionic bilayer lipid vesicles (liposomes) locally by electrostatically binding them in a complex with cationic polymers. This method is implemented by mixing premade solutions of liposomes and polymers, which significantly reduces the time and cost of obtaining multiliposomal complexes. Binding of liposomes with cationic linear polymers, latexes, and star polymers does not solve the problem of obtaining multiliposomal complexes: the size of such complexes cannot be controlled, and these variants fail to ensure the integrity of bound liposomes or result in complexes with a minimal amount of liposomes. The best results are demonstrated by complexes of anionic liposomes and polystyrene nanoparticles with grafted cationic chains (spherical polycationic brushes). Each brush can bind several dozen liposomes, which retain their integrity after being adsorbed on the surface of the brush. Such complexes do not dissociate into the initial components either in physiological saline with [NaCl] = 0.15 mol/L or in the presence of significant amounts of protein. The use of liposomes with different fillers (different liposomal “compartments”) makes it possible to obtain multiliposomal complexes with the desired fraction of substances encapsulated in the liposomes. The proposed approach is of interest in terms of obtaining multiliposomal complexes for concentration, compartmentalization, and subsequent controlled release of drugs.     

Enhanced localization of anticancer drug in tumor tissue using polyethylenimine-conjugated cationic liposomes

Liposome-based drug delivery systems hold great potential for cancer therapy. However, to enhance the localization of payloads, an efficient method of systemic delivery of liposomes to tumor tissues is required. In this study, we developed cationic liposomes composed of polyethylenimine (PEI)-conjugated distearoylglycerophosphoethanolamine (DSPE) as an enhanced local drug delivery system. The particle size of DSPE-PEI liposomes was 130 ± 10 nm and the zeta potential of liposomes was increased from -25 to 30 mV by the incorporation of cationic PEI onto the liposomal membrane. Intracellular uptake of DSPE-PEI liposomes by tumor cells was 14-fold higher than that of DSPE liposomes. After intratumoral injection of liposomes into tumor-bearing mice, DSPE-PEI liposomes showed higher and sustained localization in tumor tissue compared to DSPE liposomes. Taken together, our findings suggest that DSPE-PEI liposomes have the potential to be used as effective drug carriers for enhanced intracellular uptake and localization of anticancer drugs in tumor tissue through intratumoral injection.     

Application of Asymmetrical Flow Field-Flow Fractionation for Characterizing the Size and Drug Release Kinetics of Theranostic Lipid Nanovesicles

Liposome size and in vitro release of the active substance belong to critical quality attributes of liposomal carriers. Here, we apply asymmetric flow field-flow fractionation (AF4) to characterize theranostic liposomes prepared by thin lipid film hydration/extrusion or microfluidics. The vesicles’ size was derived from multi-angle laser light scattering following fractionation (AF4) and compared to sizes derived from dynamic light scattering measurements. Additionally, we adapted a previously developed AF4 method to study zinc phthalocyanine (ZnPc) release/transfer from theranostic liposomes. To this end, theranostic liposomes were incubated with large acceptor liposomes serving as a sink (mimicking biological sinks) and were subsequently separated by AF4. During incubation, ZnPc was transferred from donor to acceptor fraction until reaching equilibrium. The process followed first-order kinetics with half-lives between 119.5–277.3 min, depending on the formulation. The release mechanism was postulated to represent a combination of Fickian diffusion and liposome relaxation. The rate constant of the transfer was proportional to the liposome size and inversely proportional to the ZnPc/POPC molar ratio. Our results confirm the usefulness of AF4 based method to study in vitro release/transfer of lipophilic payload, which may be useful to estimate the unwanted loss of drug from the liposomal carrier in vivo.     

Polyurethane/doxorubicin nanoparticles based on electrostatic interactions as pH‐sensitive drug delivery carriers

In order to obtain a pH‐sensitive delivery carrier for doxorubicin (DOX), DOX‐loaded polyurethane (PU·DOX) nanoparticles were readily prepared in water by electrostatic interactions between amphiphilic polyurethane with carboxyl pendent groups (PU‐COOH) and doxorubicin hydrochloride (DOX·HCl). The structures of the products obtained were characterized by Fourier transform infrared spectroscopy, ¹H NMR spectroscopy, gel permeation chromatography, UV–visible spectroscopy, dynamic light scattering and transmission electron microscopy. The average hydrodynamic size of the PU·DOX nanoparticles was around 182 nm with negative surface charge (?1.1 mV) and a spherical or rodlike shape. PU·DOX nanoparticles had a higher drug‐loading content of 14.1 wt%. The in vitro drug release properties of PU·DOX nanoparticles were investigated at pH 4.0, 5.0 and 7.4, respectively. PU·DOX nanoparticles exhibited a good pH‐sensitive drug release property, but there was almost no release of DOX from PU·DOX nanoparticles at pH 7.4. The in vitro cellular uptake assay and the Cell Counting Kit‐8 assay demonstrated that PU·DOX nanoparticles had a higher level of cellular internalization and higher inhibitory effects on the proliferation of human breast cancer (MCF‐7) cells than pure DOX. The enhancement of the inhibition effects resulted from increasing apoptosis‐inducing effects on MCF‐7 cells, which was related to the enhancement of Bax expression and the reduction of Bcl‐2 expression confirmed by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling (TUNEL) assay, real‐time polymerase chain reaction (PCR) assay and western blot assay. © 2018 Society of Chemical Industry