Folate-modified poly(2-ethyl-2-oxazoline) as hydrophilic corona in polymeric micelles for enhanced intracellular doxorubicin delivery

The transmembrane transport of drug loaded micelles to intracellular compartment is quite crucial for efficient drug delivery. In the current study, we investigated the cellular internalization and anticancer activity of doxorubicin loaded micelles with folate modified stealthy PEOz corona. Folate-decorated micelles incorporating doxorubicin were characterized for particle size, degree of folate decoration, drug loading content and encapsulation efficiency, morphology, and surface charge. The targeting capability and cell viability were assessed using HeLa, KB, A549 and MCF-7/ADR cell lines. In vitro study clearly illustrated the folate receptor (FR) mediated targeting of FA modified micelles to FR-positive human HeLa, KB and MCF-7/ADR cells, while specific delivery to FR-negative A549 cells was not apparently increased at the same experimental conditions. Cytotoxicity assay showed 60% and 58% decrease in IC₅₀ values for HeLa and KB cells, while only a slight decrease for A549 cells, following treatment with folate modified formulations. The enhanced intracellular delivery of FA modified micelles in MCF-7/ADR cells was also observed. In vivo antitumor tests revealed DOX entrapped FA-PEOz-PCL micelles effectively inhibited the tumor growth and reduced the toxicity to mice compared with free DOX. The current study showed that the targeted nano-vector improved cytotoxicity of DOX and suggested that this novel PEOz endowed stealthy micelle system held great promise in tumor targeted therapy.     

Doxorubicin Loaded pH-sensitive Micelle: Antitumoral Efficacy against Ovarian A2780/DOXR Tumor

PURPOSE: To evaluate pH-sensitive mixed micelles for multidrug resistant (MDR) ovarian tumor targeting and optical imaging of solid tumors. METHOD: Doxorubicin (DOX) encapsulated pH-sensitive mixed micelles composed of poly(L: -histidine)(MW 5K)-b-PEG(MW 2K) and poly(L: -lactic acid)(3K)-b-PEG (2K)-folate (PHSM-f) were prepared. Folate receptor-mediated endocytosis, drug uptake, endosomal disruption and cell viability were investigated at the cellular level. For in vivo tumor growth inhibition tests, multidrug resistant ovarian A2780/DOX(R) xenografted nude mice were used. Optical imaging was performed by using a Cy5.5 fluorescence dye-labeled mixed micelle system. Cy5.5 fluorescence intensity at the tumor site was measured in KB epidermoid xenografted nude mice. RESULTS: In vitro cell viability and drug distribution in the cytoplasm demonstrated the significantly superior efficacy of PHSM-f to free DOX and a control sample of DOX loaded pH-insensitive micelle composed of poly(L: -lactic acid)(3K)-b-PEG(2K)/poly(L: -lactic acid)(3K)-b-PEG(2K)-folate (80/20 wt/wt%) (PHIM-f). The mechanisms of these results were proved by folate receptor mediated endocytosis of micelle and endosomal disruption function by it. In addition, the optical imaging demonstrated the future application of the diagnositic area. PHSM-f inhibited the growth of multidrug resistant ovarian tumors efficiently in mice, with minimum weight loss. CONCLUSIONS: The pH-sensitive mixed micelle system demonstrates effective antitumor efficacy against the multidrug resistant ovarian tumor A2780/DOX(R).     

Cellular uptake and cytotoxicity of shell crosslinked stearic acid-grafted chitosan oligosaccharide micelles encapsulating doxorubicin

Stearic acid-grafted chitosan oligosaccharide (CSO-SA) with 3.48% amino-substituted degree (SD%) was synthesized by coupling reaction. The CSO-SA could self-aggregate to form micelle with a critical micelle concentration (CMC) at 0.035 mg/mL in the aqueous phase. The CSO-SA self-aggregate micelles indicated spatial structure with multi-hydrophobic core. One CSO-SA chain could form 2.8 hydrophobic cores. Cellular uptakes of CSO-SA micelles by using A549, LLC, and SKOV3 cells as model tumor cell lines showed the faster cellular internalization of CSO-SA micelles, and the cellular uptakes on the LLC and SKOV3 cells were higher than that on the A549 cells. Doxorubicin (DOX) was then used as a model drug to incorporate into CSO-SA micelles. To reduce the initial burst drug release from CSO-SA micelles loading DOX (CSO-SA/DOX), the shell of CSO-SA micelles was crosslinked by glutaraldehyde. The shell crosslinking of CSO-SA micelles reduced the micelle size and surface potential, but it did not significantly affect the cellular uptake and drug encapsulation efficiency of CSO-SA micelles. The cellular inhibition experiments demonstrated that the cytotoxicity of DOX was increased by the encapsulation of CSO-SA micelles. CSO-SA/DOX displayed the best antitumor efficacy in SKOV3 cell line due to the higher cellular uptake percentage of CSO-SA micelles and the lower sensitivity of free drug to the cells. The cytotoxicities of shell crosslinked CSO-SA/DOX were highly enhanced in all cell lines than those of unmodified CSO-SA/DOX.     

Honokiol-loaded polymeric nanoparticles: an active targeting drug delivery system for the treatment of nasopharyngeal carcinoma

The purpose of this study was to develop a novel drug delivery system for a sustained and targeted delivery of honokiol (HK) to the nasopharyngeal carcinoma (NPC) HNE-1 cell lines, since the folate receptor (FR) is over-expressed on their surface. Emulsion solvent evaporation was used to develop the active targeting nanoparticles-loaded HK (ATNH) using copolymerpoly (?-caprolactone)-poly (ethyleneglycol)-poly (?-caprolactone) (PCEC), which was modified with folate (FA) by introducing Polythylenimine (PEI). ATNH characterization, including particle size distribution, morphology, drug loading, encapsulation efficiency and drug release, was performed. Transmission electron microscopy (TEM) and Fourier transform infrared spectroscopy (FTIR) were employed to evaluate the shape and construction, respectively. MTT assay, cell uptake study and apoptosis test were assayed to detect the antitumor properties and targeting uptake by HNE-1 cells in vitro. Cell-cycle redistribution, ^18?F-FDG PET/CT and immunohistochemistry were performed in vivo. The ATNH we developed were successfully synthesized and showed a suitable size distribution, high encapsulation efficiency, gradual release, and targeting uptake by the cells in vitro. Moreover, ATNH significantly inhibited tumor growth, metabolism, proliferation, micro-vessel generation, and caused cell-cycle arrest at G₁ phase. Thus, these nanoparticles we developed might represent a novel formulation for HK delivery and a promising potential therapy in the treatment of cancer.     

Enhanced Intercellular Retention Activity of Novel pH-sensitive Polymeric Micelles in Wild and Multidrug Resistant MCF-7 Cells

Purpose The purpose of this work was to demonstrate the advantage of using pH-sensitive polymeric mixed micelles (PHSM) composed of poly(l-histidine) (polyHis)/poly(ethylene glycol) (PEG) and poly(l-lactic acid) (pLLA)/PEG block copolymers with folate conjugation to increase drug retention in wild-type and MDR tumor cells. Materials and Methods Both wild-type and multidrug resistant (MDR) human breast adenocarcinoma (MCF-7) cell lines were used to investigate the accumulation and elimination of doxorubicin (DOX), PHSM with folate (PHSM/f), and pH-insensitive micelles composed of pLLA/PEG block copolymer with folate (PHIM/f). Results Cells treated with PHSM/f showed decelerated elimination kinetics compared to cells treated with PHIM/f. MDR cells treated with drug-containing PHSM/f for 30 min retained 80% of doxorubicin (DOX) even after incubation for 24 h in the absence of drug. On the other hand, cells treated with drug-containing PHIM/f retained only 40% of DOX within the same period of time. Flow cytometry and confocal microscopy confirmed these results. Conclusions Cellular entry of the micelles occurred via receptor-mediated endocytosis using folate receptors. The pH-induced destabilization of PHSM/f led to rapid distribution of drug and polymer throughout the cells, most likely due to polyHis-mediated endosomal disruption. This reduced the likelihood of drug efflux via exocytosis from resistant tumor cells.     

Reduction-responsive PEtOz-SS-PCL micelle with tailored size to overcome blood–brain barrier and enhance doxorubicin antiglioma effect

A series of novel reduction-responsive micelles with tailored size were designed and prepared to release doxorubicin (DOX) for treating glioma, which were developed based on amphiphilic block copolymer poly (2-ethyl-2-oxazoline)-b-poly (ε-caprolactone) (PEtOz-SS-PCL) and the micelle size could be regulated by designing the polymer structure. The DOX-loaded PEtOz-SS-PCL micelles had small size and rapid drug release in reductive intracellular environments. Biodistribution and in vivo imaging studies in C6 glioma mice tumor model showed that DOX loaded PEtOz-SS-PCL43 micelles with the smallest size had superior accumulation and fast drug release in tumor sites. In vivo antitumor activity demonstrated that DOX-loaded PEtOz-SS-PCL43 micelles improved antitumor efficacy in contrast to PEtOz-SS-PCL micelles with larger size toward the orthotopic C6-Luci cells-bearing mice. This study shows great potential in tailoring the micelle size and introducing the responsive bonds or compartment for intracellular drug delivery and release in glioma treatment by designing the architecture of the polymer.     

Cytotoxic enhancement of hexapeptide-conjugated micelles in EGFR high-expressed cancer cells

Objectives: The aim of this study was to develop the hexapeptide-conjugated active targeting micelles for delivery of doxorubicin (DOX) and paclitaxel (PTX) to EGFR high-expressed cancer cells.

Methods: A hexapeptide, which mimicked the EGFR, was applied as a targeting ligand. The active targeting micelles were prepared using the synthesized poly(D,L-lactide-co-glycolide)–PEG copolymer conjugated with the hexapeptide. The micelles were used for encapsulating DOX and/or PTX, and the cellular uptake, in vitro drug release and cellular viability of drug-loaded peptide-conjugated and peptide-free micelles were investigated.

Results: The particle size of drug-loaded peptide-conjugated and peptide-free micelles was < 150 nm with narrow size distribution. The uptake of peptide-conjugated micelles was more efficient in EGFR high-expressed MDA-MB-468 and SKOV3 cells than in EGFR low-expressed HepG2 cells. The in vitro release of DOX and PTX was faster in pH 4.0 (500 U lipase) than in pH 7.4 release medium. The cytotoxicity in terms of IC₅₀ of DOX/PTX-loaded peptide-conjugated micelles was 4.8-folds lower than that of peptide-free micelles and 18.2-folds lower than DOX/PTX drug solution in SOKV3 cells.

Conclusion: The peptide-conjugated micelles acted as a nanocarrier to increase intracellular accumulation of anticancer drugs in EGFR high-expressed SKOV3 cancer cells to enhance cell cytotoxicity.     

Engineering a folic acid-decorated ultrasmall gemcitabine nanocarrier for breast cancer therapy: Dual targeting of tumor cells and tumor-associated macrophages

Combination of passive targeting with active targeting is a promising approach to improve the therapeutic efficacy of nanotherapy. However, most reported polymeric systems have sizes above 100 nm, which limits effective extravasation into tumors that are poorly vascularized and have dense stroma. This will, in turn, limit the overall effectiveness of the subsequent uptake by tumor cells via active targeting. In this study, we combined the passive targeting via ultra-small-sized gemcitabine (GEM)-based nanoparticles (NPs) with the active targeting provided by folic acid (FA) conjugation for enhanced dual targeted delivery to tumor cells and tumor-associated macrophages (TAMs). We developed an FA-modified prodrug carrier based on GEM (PGEM) to load doxorubicin (DOX), for co-delivery of GEM and DOX to tumors. The co-delivery system showed small particle size of ～10 nm in diameter. The ligand-free and FA-targeted micelles showed comparable drug loading efficiency and a sustained DOX release profile. The FA-conjugated micelles effectively increased DOX uptake in cultured KB cancer cells that express a high level of folate receptor (FR), but no obvious increase was observed in 4T1.2 breast cancer cells that have a low-level expression of FR. Interestingly, in vivo, systemic delivery of FA-PGEM/DOX led to enhanced accumulation of the NPs in tumor and drastic reduction of tumor growth in a murine 4T1.2 breast cancer model. Mechanistic study showed that 4T1.2 tumor grown in mice expressed a significantly higher level of FOLR2, which was selectively expressed on TAMs. Thus, targeting of TAM may also contribute to the improved in vivo targeted delivery and therapeutic efficacy.     

Enhanced tumor-targeted delivery of anticancer drugs by folic acid-conjugated pH-sensitive polymeric micelles

In order to enhance the targeted delivery of anticancer drugs by polymeric micelles, folic acid (FA), the ligand of folate receptor (FR) over-expressed in the most cancer cells, modified pH-sensitive polymeric micelles were designed and fabricated to encapsulate doxorubicin (DOX) by combination of pH-sensitive amphiphilic polymer poly(2-ethyl-2-oxazoline)-poly(D,L-lactide) with FA-conjugated poly(2-ethyl-2-oxazoline)-poly(D,L-lactide). The prepared micelles were characterized to have about 36 nm in diameter with narrow distribution, well-defined spherical shape observed under TEM and pH-responsive drug release behavior. Moreover, the tumor targeting ability of the FA-modified pH-sensitive polymeric micelles was demonstrated by the cellular uptake, in vitro cytotoxicity to FR-positive KB cells and in vivo real time near-infrared fluorescence imaging in KB tumor-bearing nude mice. The efficient drug delivery by the micelles was ascribed to the synergistic effects of FR-mediated targeting and pH-triggered drug release. In conclusion, the designed FR-targeted pH-sensitive polymeric micelles might be of great potential in tumor targeted delivery of water-insoluble anticancer drugs.     

基于前药构建混合胶束实现紫杉醇/阿霉素共递送

为了达到靶向递送,实现肿瘤的联合治疗,制备两亲性紫杉醇-聚乙二醇前药以及小分子阿霉素前药,两者共同构成混合胶束实现共递送.合成还原敏感性的聚乙二醇-紫杉醇前体药物(mPEG-SS-PTX)和靶向性叶酸修饰的聚乙二醇-紫杉醇前体药物(FA-PEG-SS-PTX).同时合成pH敏感阿霉素-乌头酸酐(CAD)小分子前药,采用...     

Folate-decorated poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) nanoparticles for targeting delivery: optimization and in vivo antitumor activity

Abstract

Context: Doxorubicin (DOX)-loaded folate-targeted poly(3-hydroxybutyrate-co-3-hydroxyoctanoate) [P(HB-HO)] nanoparticles [DOX/FA-PEG-P(HB-HO) NPs] have potential application in clinical treatments for cervical cancer due to specific affinity of folate and folate receptor in HeLa cells.

Objective: The aim of this study was to develop an optimized formulation for DOX/FA-PEG-P(HB-HO) NPs, and investigate the targeting and efficacies of the nanoparticles.

Materials and methods: DOX/FA-PEG-P(HB-HO) NPs were prepared by W₁/O/W₂ solvent extraction/evaporation method, and an orthogonal experimental design [L₉ (3⁴)] was applied to establish the optimum conditions. The physico–chemical characteristics, microscopic observation and in vivo antitumor study of the nanoparticles were evaluated.

Results: The optimum formulation was obtained with DOX 10% (w/v), FA-PEG-P(HB-HO) 6.5% (w/v), PVA 3%(w/v) and oil phase/internal water phase volume ratio of 3/1. The size distribution, drug loading and encapsulation efficiency of the optimized nanoparticles were 150–350?nm, 29.6?±?2.9% and 83.5?±?5.7%, respectively. In vitro release study demonstrated that 80% of the drug could release from the nanoparticles within 11 days. Furthermore, in vitro microscopic observation and in vivo antitumor study showed that DOX/FA-PEG-P(HB-HO) NPs could inhibit HeLa cells effectively, and the tumor inhibition rate (TIR) in vivo was 76.91%.

Discussion and conclusions: DOX/FA-PEG-P(HB-HO) NPs have been successfully developed and optimized. In vitro drug release study suggested a sustained release profile. Moreover, DOX/FA-PEG-P(HB-HO) NPs could effectively inhibit HeLa cells with satisfying targeting, and reduce side effects and toxicity to normal tissues. DOX/FA-PEG-P(HB-HO) NPs were superior in terms of inhibiting HeLa tumor over non-targeted formulations therapy.     

载阿霉素透明质酸聚合物纳米粒的构建及其体外性质研究

目的 合成透明质酸（HA）接枝单油酸甘油酯（GMO）两亲性聚合物HGO,并研究其所制备载阿霉素（DOX）纳米粒的理化性质及体外抗肿瘤效果。方法 HA与GMO通过酯化反应制得载体聚合物HGO,通过核磁共振波谱法及红外光谱法对其进行结构表征;采用芘荧光探针法测定聚合物临界聚集浓度（CAC）。采用透析法制备聚合物HGO载阿霉素（DOX@HGO）纳米粒,并对其进行粒径分布、Zeta电位及微观形态的表征;通过检测其在不同离子强度、不同pH条件下的粒径变化考察纳米粒的体外稳定性;考察DOX@HGO纳米粒在不同pH条件下的体外释放行为;CCK-8法考察DOX@HGO纳米粒对MDA-MB-231细胞的体外抑瘤效果;并通过荧光显微镜研究MDA-MB-231细胞对DOX溶液、DOX@HGO纳米粒的摄取能力,以及HA预处理对DOX@HGO纳米粒摄取的影响。结果 成功制得两亲性聚合物HGO,聚合物HGO中GMO的取代度为15.8%,CAC为0.023 mg·mL^-1。DOX@HGO纳米粒呈规则的球形,平均粒径为（130.800±1.709）nm,平均电位为（-32.600±0.153）mV,包封率和载药量分别为（98.65±0.74）%和（33.03±0.17）%,在不同离子强度下、模拟胃肠液中表现出良好的稳定性;DOX@HGO纳米粒的体外释放表现出pH依赖性。体外抗肿瘤活性实验表明,DOX@HGO纳米粒对MDA-MB-231细胞的生长具有较好的抑制作用;与DOX溶液比较,DOX@HGO纳米粒显著增加肿瘤细胞对于DOX的摄取（P＜0.05） ,HA预处理显著减少肿瘤细胞对DOX@HGO的摄取（P＜0.05）。结论 所构建的DOX@HGO纳米粒具有良好的理化性质,并且具有一定的pH敏感性及靶向抗肿瘤细胞的能力,是具有应用潜力的药物载体。     

pH Triggered Doxorubicin Delivery of PEGylated Glycolipid Conjugate Micelles for Tumor Targeting Therapy

The main objective of this study was aimed at tumor microenvironment-responsive vesicle for targeting delivery of the anticancer drug, doxorubicin (DOX). A glucolipid-like conjugate (CS) was synthesized by the chemical reaction between chitosan and stearic acid, and polyethylene glycol (PEG) was then conjugated with CS via a pH-responsive cis-aconityl linkage to produce acid-sensitive PEGylated CS conjugates (PCCS). The conjugates with a critical micelle concentration (CMC) of 181.8 μg/mL could form micelles in aqueous phase, and presented excellent DOX loading capacity with a drug encapsulation efficiency up to 87.6%. Moreover, the PCCS micelles showed a weakly acid-triggered PEG cleavage manner. In vitro drug release from DOX-loaded PCCS micelles indicated a relatively faster DOX release in weakly acidic environments (pH 5.0 and 6.5). The CS micelles had excellent cellular uptake ability, which could be significantly reduced by the PEGylation. However, the cellular uptake ability of PCCS was enhanced comparing with insensitive PEGylated CS (PCS) micelles in weakly acidic condition imitating tumor tissue. Taking PCS micelles as a comparative group, the PCCS drug delivery system was demonstrated to show much more accumulation in tumor tissue, followed by a relatively better performance in antitumor activity together with a security benefit on xenograft tumor model.     

Polydopamine and peptide decorated doxorubicin-loaded mesoporous silica nanoparticles as a targeted drug delivery system for bladder cancer therapy

We reported a simple polydopamine (PDA)-based surface modification method to prepare novel targeted doxorubicin-loaded mesoporous silica nanoparticles and peptide CSNRDARRC conjugation (DOX-loaded MSNs@PDA-PEP) for enhancing the therapeutic effects on bladder cancer. Drug-loaded NPs were characterized in terms of size, size distribution, zeta potential, transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) surface area and drug loading content. In vitro drug release indicated that DOX-loaded MSNs@PDA and MSNs@PDA-PEP had similar release kinetic profiles of DOX. The PDA coating well controlled DOX release and was highly sensitive to pH value. Confocal laser scanning microscopy (CLSM) showed that drug-loaded MSNs could be internalized by human bladder cancer cell line HT-1376, and DOX-loaded MSNs@PDA-PEP had the highest cellular uptake efficiency due to ligand–receptor recognition. The antitumor effects of DOX-loaded nanoparticles were evaluated by the MTT assay in vitro and by a xenograft tumor model in vivo, demonstrating that targeted nanocarriers DOX-loaded MSNs@PDA-PEP were significantly superior to free DOX and DOX-loaded MSNs@PDA. The novel DOX-loaded MSNs@PDA-PEP, which specifically recognized HT-1376 cells, can be used as a potential targeted drug delivery system for bladder cancer therapy.     

雷公藤甲素叶酸靶向纳米胶束的制备及其体外抗炎作用研究

目的 制备雷公藤甲素叶酸靶向纳米胶束（TP@PCL-PEG-FA）,并研究其体外抗炎效果。方法 采用薄膜水化法制备TP@PCL-PEG-FA胶束,对粒径和电位进行表征,观察其形态特征,采用超滤法测定包封率和载药量,同时考察药物的体外释放。观察胶束的摄取效率,考察体外抗炎作用。结果 TP@PCL-PEG-FA胶束的平均粒径为（34.1±5.1） nm,Zeta电位为（-10.1±2.2） mV,呈类球形,粒径分布均一。包封率为（85.7±5.8）%,载药量为（1.8±0.5）%。TP@PCL-PEG-FA胶束均能够相对缓慢释放药物,具有缓释效果。与普通非靶向PCL-PEG胶束相比,PCL-PEG-FA胶束在脂多糖刺激的RAW 264.7细胞中的摄取效率明显提高,TP@PCL-PEG-FA胶束有更强的体外抗炎效率。结论 制备了雷公藤甲素的叶酸靶向的TP@PCL-PEG-FA胶束,具有更好的体外靶向抗炎作用,为雷公藤甲素的纳米递药系统提供了一种新策略和新思路。     

Redox-responsive biocompatible nanocarriers based on novel heparosan polysaccharides for intracellular anticancer drug delivery

Heparosan is a natural precursor of heparin biosynthesis in mammals. It is stable in blood circulation but can be degraded in lysosomes, showing good biocompatibility and long circulation features. So heparosan can be designed as anticancer drug carriers to increase tumor selectivity and improve the therapeutic effect. A novel redox-sensitive heparosancystamine-vitamin E succinate(KSV) micelle system was constructed for intracellular delivery of doxorubicin(DOX). Simultaneously, the redox-insensitive heparosan-adipic acid dihydrazide-vitamin E succinate copolymer(KV) was synthesized as control. DOX-loaded micelles(DOX/KSV) with an average particle size of 90–120 nm had good serum stability and redox-triggered depolymerization. In vitro drug release test showed that DOX/KSV micelles presented obvious redox-triggered release behavior compared with DOX/KV. Cytotoxicity and cell uptake were investigated using MGC80-3 tumor cells and COS7 fibroblast-like cells. The cell survival rate of blank micelles was more than 90%, and the cytotoxicity of DOX/KSV in MGC80-3 cells was higher than in COS7 cells, indicating that the carrier has better biocompatibility and less toxicity side effect. The cytotoxicity of DOX/KSV against MGC80-3 cells was significantly greater than that of free DOX and DOX/KV. Furthermore, compared with DOX/KV in MGC80-3 cells, DOX/KSV micelles uptook more anticancer drugs and then released DOX faster into the cell nucleus. The micelles were endocytosed by multiple pathways, but clathrin-mediated endocytosis was the main pathway. Therefore, heparosan polysaccharide could be a potential option as anticancer carrier for enhancing efficacy and mitigating toxicity.     

Sericin nanomicelles with enhanced cellular uptake and pH-triggered release of doxorubicin reverse cancer drug resistance

Drug resistance is the major challenge facing cancer chemotherapy and nanoscale delivery systems based on natural materials, such as sericin, are a promising means of overcoming drug resistance. Yet, no attempt of introducing synthetic poly(γ-benzyl-L-glutamate) (PBLG) onto sericin polypeptide to fabricate a facile biocompatible and biodegradable micelle has been tried. Here, we prepared a polypeptide-based amphiphilic polymer containing hydrophilic sericin polypeptide backbone and PBLG side chains via ring-opening polymerization (ROP) strategy. The introduction of PBLG side chains remarkably enhances the stability of sericin micelles in water. Meanwhile, the micelles exhibited a high loading capacity and pH-responsive release ability for antitumor drug doxorubicin (DOX), called sericin-PBLG-DOX. Owing to the excellent cell membrane penetration of sericin-PBLG, the cellular uptake of DOX when loaded into micelles was improved. Subsequently, sericin-PBLG-DOX was transferred into perinuclear lysosomes, where the release rate of DOX was accelerated. Compared to the same dose of DOX, sericin-PBLG-DOX could induce a more efficient anti-tumor effect both in vitro and in vivo, and these micelles have promise for future clinical applications in overcoming cancer drug resistance with good biosafety, enhanced cellular uptake, pH-triggered drug release, efficient anti-tumor effects, and minimized systemic toxicity.     

Dynamic micelles with detachable PEGylation at tumoral extracellular pH for enhanced chemotherapy

Although surface PEGylation of nanomedicines can decrease serum protein adsorption in vivo, it also blocks uptake by tumor cells. This dilemma could be overcome by employing detachably PEGylated strategy at tumoral extracellular microenvironment to achieve improved cellular uptake while prolonged circulation times. Herein, the amphiphilic graft copolymers with pH-sensitive ortho ester-linked mPEG in side chains and polyurethanes in backbone, can self-assemble into the free and doxorubicin (DOX)-loaded micelles. The pH-sensitive micelles could undergo several characteristics as follows: (i) PEGylated shells for stability in sodium dodecyl sulfonate (SDS) solution; (ii) DePEGylation via degradation of ortho ester linkages at tumoral extracellular pH (6.5) for gradually dynamic size changes and effective release of DOX; and (iii) enhanced cellular uptake and cytotoxicity via positive DOX. Moreover, the dynamic micelles with detachable PEGylation could quickly penetrate the centers of SH-SY5Y multicellular spheroids (MCs) and strongly inhibit tumor growth in vitro and in vivo, and might be considered as promising and effective drug carriers in tumor therapy.     

Selectivity of folate conjugated polymer micelles against different tumor cells

Folate or folic acid has been employed as a targeting moiety of various anticancer agents to increase their cellular uptake within target cells since folate receptors are vastly overexpressed in several human tumors. In this study, a biodegradable polymer poly(d,l-lactide-co-glycolide)-poly(ethylene glycol)-folate (PLGA-PEG-FOL) was used to form micelles for encapsulating anticancer drug doxorubicin (DOX). The drug loading content, encapsulation efficiency and in vitro release were characterized. To evaluate the targeting ability of the folate conjugated micelles, the cytotoxicity and cellular uptake of DOX-loaded micelles on three cancer cell lines with different amount of folate receptors (KB, MATB III, C6) and normal fibroblast cells (CCL-110) were compared. The cytotoxicity of PLGA-PEG-FOL micelles to cancer cells was found to be much higher than that of normal fibroblast cells, demonstrating that the folate conjugated micelles has the ability to selectively target to cancer cells. For normal cells, the cellular uptake of PLGA-PEG-FOL micelles was similar to PLGA-PEG micelles without folate conjugation, and was substantially lower than that of cancer cells. In addition, the cell cycle analysis showed that the apoptotic percentage of normal fibroblasts was substantially lower compared with the cancer cells after exposing to DOX-loaded PLGA-PEG-FOL micelles. An optimal folate amount of approximately 40-65% on the micelles was found to be able to kill cancer cells but, at the same time, to have very low effect to normal cells.     

载多西紫杉醇的F3多肽靶向单分子胶束的制备和体外评价

目的：制备载多西紫杉醇的F3多肽靶向单分子胶束（DTX/PAMAM-PLA-PEG-F3）,并对其进行体外评价。方法：所制备的单分子胶束采用动态光散射仪和透射电镜测定其粒径分布和形态;采用高效液相色谱法测定单分子胶束的载药量和评估其体外释药特性;采用MTT法考察单分子胶束的抗肿瘤活性;采用流式细胞仪和共聚焦显微镜探究细胞摄取胶束机制。结果：制备的单分子胶束呈球形,平均粒径（32.0±5.8） nm,载药量（12.4±1.3）wt.%;体外释药研究表明制备的单分子胶束具有pH响应性;与非靶向胶束组相比,靶向胶束组的对乳腺癌MDA-MB-231细胞的细胞毒性更高,细胞摄取效率加强,靶向配体F3多肽可介导肿瘤细胞特异性摄取靶向单分子胶束。结论：DTX/PAMAM-PLA-PEG-F3作为纳米药物载体在提高抗肿瘤疗效方面具有广阔的应用前景。