pH-sensitive polymeric micelles triggered drug release for extracellular and intracellular drug targeting delivery

Most of the conventional chemotherapeutic agents used for cancer chemotherapy suffer from multidrug resistance of tumor cells and poor antitumor efficacy.Based on physiological differences between the normal tissue and the tumor tissue,one effective approach to improve the efficacy of cancer chemotherapy is to develop pH-sensitive polymeric micellar delivery systems.The copolymers with reversible protonationedeprotonation core units or acid-liable bonds between the therapeutic agents and the micelle-forming copolymers can be used to form pH-sensitive polymeric micelles for extracellular and intracellular drug smart release.These systems can be triggered to release drug in response to the slightly acidic extracellular fluids of tumor tissue after accumulation in tumor tissues via the enhanced permeability and retention effect,or they can be triggered to release drug in endosomes or lysosomes by pH-controlled micelle hydrolysis or dissociation after uptake by cells via the endocytic pathway.The pH-sensitive micelles have been proved the specific tumor cell targeting,enhanced cellular internalization,rapid drug release,and multidrug resistance reversal.The multifunctional polymeric micelles combining extracellular pH-sensitivity with receptor-mediated active targeting strategies are of great interest for enhanced tumor targeting.The micelles with receptor-mediated and intracellular pH targeting functions are internalized via receptor-mediated endocytosis followed by endosomal-pH triggered drug release inside the cells,which reverses multidrug resistance.The pH sensitivity strategy of the polymeric micelles facilitates the specific drug delivery with reduced systemic side effects and improved chemotherapeutical efficacy,and is a novel promising platform for tumor-targeting drug delivery.

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 p H-sensitive polymeric micelles were designed and fabricated to encapsulate doxorubicin(DOX) by combination of p H-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 p H-responsive drug release behavior. Moreover, the tumor targeting ability of the FA-modified p H-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 p H-triggered drug release. In conclusion, the designed FR-targeted p H-sensitive polymeric micelles might be of great potential in tumor targeted delivery of water-insoluble anticancer drugs.

Linear-like polypeptide-based micelle with pH-sensitive detachable PEG to deliver dimeric camptothecin for cancer therapy

Nano drug delivery systems have made significant progress in delivering anticancer drugs camptothecin(CPT).However,many challenges for CPT delivery remain,including low drug loading efficiency,premature drug leakage,and poor cellular internalization.Herein,we report a novel dual-sensitive polypeptide-based micelle with remarkably high drug loading of CPT for cancer therapy.This self-assembled micelle possesses the following essential components for CPT:(1)pH-sensitive PEG(OHC-PEG-CHO)for prolonging blood circulation and allowing biocompatibility by shielding the cationic micelles,which can be detached under the tumor acidic microenvironment and facilitates the cellular uptake;(2)polypeptide polylysine-polyphenylalanine(PKF)synthesized via ring-opening polymerization for micelle formation and CPT analogue loading;(3)dimeric CPT(DCPT)with redox-sensitive linker for increasing CPT loading and ensuring drug release at tumor sites.Interestingly,the linear-like morphology of PEG-PKF/DCPT micelles was able to enhance their cellular internalization when compared with the spherical blank PKF micelles.Also,the anticancer efficacy of DCPT against lung cancer cells was significantly improved by the micelle formation.In conclusion,this work provides a promising strategy facilitating the safety and effective application of CPT in cancer therapy.

Synthesis and evaluation of cationic polymeric micelles as carriers of lumbrokinase for targeted thrombolysis

To achieve targeted thrombolysis, a targeted delivery system of lumbrokinase(LK) was constructed using RGDfk-conjugated hybrid micelles. Based on the specific affinity of RGDfk to glycoprotein complex of GP Ⅱ b/Ⅲ a expressed on the surface of membrane of activated platelet, LK loaded targeted micelles(LKTM) can be delivered to thrombus. The hybrid micelles were composed of polycaprolactone-block-poly(2-(dimethylamino) ethyl methacrylate)(PCL-PDMAEMA), methoxy polyethylene glycol-block-polycaprolactone(mPEG-PCL)and RGDfk conjugated polycaprolactone-block-polyethylene glycol(PCL-PEG-RGDfk). PCLPDMAEMA was synthesized via ring open polymerization(ROP) and atom transfer radical polymerization(ATRP). PCL-PEG-RGDfk was synthesized via ROP and carbodiimide chemistry. The prepared LKTM was characterized by dynamic light scattering(DLS) and transmission electron microscope(TEM). Colloidal stability assay showed the prepared LKTM was stable. Biocompatibility assay was performed to determine the safe concentration range of polymer. The assay of fluorescent distribution in vivo demonstrated that LKTM can be efficiently delivered to thrombi in vivo. Thrombolysis in vivo indicated the thrombolytic potency of LKTM was optimal in all groups. Notably, the laboratory mice treated with LKTM exhibited a significantly shorter tail bleeding time compared to those treated with LK or LK-loaded micelles without RGDfk, which suggested that the targeted delivery of LK using RGDfk-conjugated hybrid micelles effectively reduced the bleeding risk.

Evaluation of Cisplatin-Loaded Polymeric Micelles and Hybrid Nanoparticles Containing Poly(Ethylene Oxide)-Block-Poly(Methacrylic Acid) on Tumor Delivery

Particulate carriers such as polymeric micelles (PMs) and liposomes have been investigated to increase drug accumulation in tumors and reduce distribution to healthy tissues. In this study, we prepared PM and hybrid nanoparticles (HNPs) with poly(ethylene oxide)-block-poly(methacrylic acid) (PEO-b-PMAA) for loading cisplatin, and evaluated cisplatin release, cytotoxicity, and biodistribution in mice. PM composed of PEO-b-PMAA and HNPs composed of egg phosphatidylcholine (EPC)/PEO-b-PMAA at molar ratios of 50/2.8 (HNP-P5) and 50/50 (HNP-P50), respectively, were prepared by a nanoprecipitation method. The sizes of PM, HNP-P5, and HNP-P50 after inclusion of cisplatin were approximately 200, 100, and 55 nm, respectively, and their entrapment efficiencies were approximately 44% - 66%. In the drug-release study, HNP-P5 and HNP-P50 showed reduced release of cisplatin compared with PM. Regarding the cytotoxic assay, HNP-P5 exhibited lower cytotoxicity for mouse Lewis lung carcinoma (LLC) and mouse colon carcinoma Colon 26 cells than PM and HNP-P50. In terms of biodistribution, PM could significantly improve blood circulation and tumor accumulation after intravenous injection into Colon 26 tumor-bearing mice compared with free cisplatin, but HNP-P5 and HNP-P50 did not. EPC in HNPs might be destabilized in the circulation, although it could reduce release of cisplatin in in vitro experiments. This study suggested that polymeric micelles composed of PEO-b-PMAA are a better carrier for cisplatin than hybrid nanoparticles composed of PEO-b-PMAA and EPC.

Preparation of adhesive resveratrol micelles and determination of drug content

Objective:Resveratrol polymer micelles with tissue adhesion were prepared and the content of resveratrol in the micelles was determined by HPLC.Method:The micelle adhesion experiment was carried out by polylysine orifice plate experiment and small animal fluorescence imaging method,and the micelle prescription was optimized to obtain resveratrol micelles with good adhesion.The separation was performed on a Shiseido SPOLAR C18 column(150 mm×4.6 mm,5μm)with methanol-water(42:58)as the mobile phase.The flow rate was 1.0 mL·min^(-1),the detection wavelength was 305 nm,the column temperature was 35℃,and the injection volume was 10μL.Results:Resveratrol micelles prepared with F127 alone had the best adhesion.The peak area and concentration of resveratrol had a good linear relationship in the concentration range of 10~200μg/mL(r=0.9996).The specificity,precision,recovery and stability all met the methodological requirements.Conclusion:In this experiment,resveratrol micelles with tissue adhesion were successfully prepared,and a method for the determination of resveratrol content in micelles was established.The method is accurate,rapid and simple.

Polymeric complex micelle loaded with axially substituted silicon(Ⅳ) phthalocyanine

A novel axially substituted silicon（IV） phthalocyanine, namely di-pyridyloxy axially substituted silicon（IV） phthalocyanine 2 was synthesized and characterized by UV/vis, IR, elemental analysis, MS as well as IH NMR spectroscopy. Hydrophobic 2 was encapsulated by amphiphilic triblock copolymer poly[N^e-（benzyloxycarbonyl-lysine]-poly（ethylene glycol）-poly [N^e-（benzyl oxycarbonyl） （PLL（Z）-b-PEG-b-PLL（Z）） to form hydrophobic 2-loaded polymeric complex micelle （PIC） （2-loaded P/C）. Atom force microscopy （AFM） image showed that 2-loaded PIC formed a spherical nanocarrier with approximately 35-50 nm in diameter. The fluorescence intensity and lifetime of 2-loaded PIC was significantly enhanced bv the incorporation 2 into PIC nanocarrier.

Polyamine-Polymeric Micelle Hybrid Hydrogel: Microscopic Properties of Crosslinkers Affecting Macroscopic Rheological Properties of Hydrogel

We have developed a hybrid hydrogel that is formed from a crosslinkable polymeric micelle and a polyamine. Under optimal conditions, the hydrogel rapidly formed in one second after a crosslinkable polymeric micelle solution was mixed with a polyamine solution. We could change the hydrogel’s gelation properties, such as the storage modulus and gelation time by tuning the molecular weights of block copolymers and by tuning the pH of the dissolving-solvent of the hydrogel’s constituent components. Furthermore, we have clarified here that the structural difference among the micelles acting as crosslinkers can affect the gelation properties of the hydrogel. According to our findings, the hydrogel that was formed from the polymeric micelles possessing a highly packed (i.e., well-entangled or crosslinked) inner core exhibited a higher storage modulus than the hydrogel that was formed from the polymeric micelles possessing a lowly packed structure. Our results demonstrate that a microscopic structural difference among crosslinkers can induce a macroscopic change in the properties of the resulting hydrogels. For medical applications, the hydrogel proposed in the present paper can encapsulate the hydrophobic compounds in crosslinkers (polymeric micelles) so that the hydrogel can be available as the biomaterial for their sustained release.

The polymer micelles and application in tumor targeted therapy system

The current cancer chemotherapy drugs are inefficient and highly toxic,thus selecting the appropriate new forms of cancer treatment has become one of the important tasks.On the basis of domestic and foreign research,the composition,characteristics and main preparation methods of polymeric micelles,particularly the targeted polymeric micelles are illustrated.This review introduces different targeted polymeric micelles used as an anticancer drug carrier.By making use of the inside microenvironment of tumor cells,the preparation of a variety of new polymeric micelles with slight side effects and powerful effect in vitro and vivo,which can achieve effective control of drug release,is promising in application.

Thermo-and pH-sensitive Polymer with Pendant Spacer-linked Imidazole Cycles

By the reaction of poly(acryloyl chloride) with N-(3-aminopropyl)imidazole, poly(N-(3-(1H-imidazol-1-yl)propyl)acrylamide) was synthesized. The new polymer contains an imidazole ring removed from the main chain by a spacer of five bonds. The structure and purity, molecular weight, hydrodynamic and thermosensitive properties of the obtained sample were studied by1H-and13C-NMR, FTIR spectroscopy, acid-base titration, light scattering, turbidimetry and viscometry. The observed ability of the imidazole-containing polymer to form and destroy associates in water-salt solutions at pH 6.6-7.4 and temperatures of 29-48℃ indicates that these are promising candidates for designing complex biomedical systems. The new polymer is able to form complexes with oligo-DNA more actively than poly(1-vinylimidazole), which is of interest for gene delivery applications. The polymer cross-linked with epichlorohydrin gives micro-relief coatings on the plastic surface, and the modified surface is able to attach negatively charged objects. This thermo-and pH-sensitive polymer modification can be applied to create finely controlled surfaces for cell culturing.

Improved Anti-tumor Efficiency against Prostate Cancer by Docetaxel-loaded PEG-PCL Micelles

This study primarily focused on the systematic assessment of both in vitro and in vivo anti-tumor effects of docetaxel-loaded polyethylene glycol（PEG）2000-polycaprolactone（PCL）2600 micelles on hormone-refractory prostate cancer（HRPC）. By using solvent evaporation method, PEG-PCL was chosen to prepare doxetaxel（DTX）-loaded mPEG-PCL micelles（DTX-PMs）, with the purpose of eliminating side effects of the commercial formulation（Tween 80） and prolonging the blood circulation time. The prepared DTX-PMs had an average particle size of 25.19±2.36 nm, a zeta potential of 0.64±0.15 mV, a polydispersity index of 0.56±0.03, a drug loading of（8.72±1.05）%, and an encapsulation efficiency of（98.1±8.4）%. In vitro cytotoxicity studies indicated that DTX-PMs could effectively kill LNCap-C4-2B cells and show a dose- and time-dependent efficacy. The hemolysis test showed that DTX-PMs had less hemocytolysis than the commercial product of Duopafei. A sustained in vitro release behavior and prolonged circulation time in blood vessels were observed in the DTX-PMs. Furthermore, when compared with Duopafei, the DTX-PMs dramatically reduced the prostate specific antigen（PSA） level and tumor growth of prostate tumor-bearing nude mice in vivo. In conclusion, the DTX-PMs can lower systemic side effects, improve anti-tumor activity with prolonged blood circulation time, and will bring an alternative to patients with HRPC.

Preparation of pH-sensitive Composite Nanofiltration Membrane

Positively charged composite nanofiltration （NF） membranes were prepared through interfacial polymerization of poly[2-（N,N-dimethyl amino）ethyl methacrylate]（PDMAEMA） on porous polysulfone （PSF） substrate membranes. The effects of pH on swelling ratio （SR） of the pure crosslinked PDMAEMA membrane and on separation performances of the composite NF membrane were investigated. The results show that the quaternized amino groups produced through interfacial polymerization technique are soluble in both phases, which accelerate the crosslinking reaction as self-catalysts. The swelling/contracting behavior of the pure crosslinked PDMAEMA exhibited a well reversible pH sensitive property. Importantly, the rejection and flux of the composite NF membrane show pH-sensitive behavior in NF process. Furthermore, with the help of a relatively novel method to measure membrane conduction, the true zeta potentials calculated on the basis of the streaming potential measurements proved the pH-sensitive behavior of the NF membrane.

FORMATION OF FLOWER-LIKE AGGREGATES FROM SELF-ASSEMBLING OF MICELLES WITH PEO SHELLS AND CROSS-LINKED POLYACRYLAMIDE CORES

Amphiphilic block copolymers,poly(ethylene oxide)-b-poly(N-acryloxysuccinimide) (PEO-b-PNAS) with various molecular weights have been successfully synthesized by atom transfer radical polymerization (ATRP) of NAS using functionalized PEO (PEO-Br) as ATRP macroinitiator.The self-assembling of the block copolymers in water,which is a good solvent for PEO and a non-solvent for PNAS.yielded spherical core-shell micelles with PNAS as core and PEO as shell.The cross-linked reaction of oxysuccinimide in PNAS chain...

Micelles as potential drug delivery systems for colorectal cancer treatment

Despite the significant progress in cancer therapy,colorectal cancer(CRC)remains one of the most fatal malignancies worldwide.Chemotherapy is currently the mainstay therapeutic modality adopted for CRC treatment.However,the long-term effectiveness of chemotherapeutic drugs has been hampered by their low bioavailability,non-selective tumor targeting mechanisms,non-specific biodistribution associated with low drug concentrations at the tumor site and undesirable side effects.Over the last decade,there has been increasing interest in using nanotechnology-based drug delivery systems to circumvent these limitations.Various nanoparticles have been developed for delivering chemotherapeutic drugs among which polymeric micelles are attractive candidates.Polymeric micelles are biocompatible nanocarriers that can bypass the biological barriers and preferentially accumulate in tumors via the enhanced permeability and retention effect.They can be easily engineered with stimuli-responsive and tumor targeting moieties to further ensure their selective uptake by cancer cells and controlled drug release at the desirable tumor site.They have been shown to effectively improve the pharmacokinetic properties of chemotherapeutic drugs and enhance their safety profile and anticancer efficacy in different types of cancer.Given that combination therapy is the new strategy implemented in cancer therapy,polymeric micelles are suitable for multidrug delivery and allow drugs to act concurrently at the action site to achieve synergistic therapeutic outcomes.They also allow the delivery of anticancer genetic material along with chemotherapy drugs offering a novel approach for CRC therapy.Here,we highlight the properties of polymeric micelles that make them promising drug delivery systems for CRC treatment.We also review their application in CRC chemotherapy and gene therapy as well as in combination cancer chemotherapy.

Characterization of pH-sensitive Poly (acrylic acid-co-N-vinyl-2-pyrrolidone) Hydrogels Prepared by Gamma Radiation

The pH-sensitive copolymer hydrogels were prepared with the monomers of acrylic acid and N-vinyl-2-pyrrolidone based on gamma radiation technique. The morphology of the hydrogels was monitored by using scanning electron microscope. The influence of absorbed dose, monomer composition and concentration on the swelling ratio (SR) of the hydrogels were investigated in detail. The effect of pH and temperature of the swelling medium on the swelling behavior of the hydrogels were also examined. The results show that the SR of the copolymer hydrogels decreases with the monomer concentration and absorbed dose increasing. The copolymer hydrogels show a better pH-sensitive behavior. In alkaline solution, the SR of the hydrogels is much higher than in acid solution.

Preparation and characterization of dual pH-sensitive polymer-doxorubicin conjugate micelles

In the present study, we designed and fabricated pH-sensitive polymeric micelles based on the conjugate of poly（2-ethyl-2-oxazoline）-poly（D,L-lactide）（PEOz-PLA） with doxorubicin（PEOz-PLA-imi-DOX） to efficiently inhibit tumor cell growth. Hence, PEOz-PLA-imi-DOX was successfully synthesized by connecting DOX to the hydrophobic end of pH-sensitive PEOz-PLA via acid cleavable benzoic imine linker and characterized by 1 H NMR spectrum and thin layer chromatography. The critical micelle concentration of PEOz-PLA-imi-DOX was determined to be（14.84±3.85） mg/L. The conjugate micelles（denoted as PP-DOX-PM） formed by PEOz-PLA-imi-DOX using film-hydration method were characterized to have a nano-scaled size of about 21 nm in diameter, and the drug loading content was 1.67%. PP-DOX-PM showed pH-dependent drug release behavior with gradually accelerated release of DOX with decrease of pH value, illustrating the micelles＇ distinguishing feature of endo/lysosomal pH from physiological pH by accelerating drug release. As anticipated, PP-DOX-PM maintained the cytotoxicity of DOX against MDA-MB-231 cells. Collectively, PP-DOX-PM might have great potential for effective suppression of tumor growth.

ROS-responsive and triple-synergistic mitochondria-targeted polymer micelles for efficient induction of ICD in tumor therapeutics

Immunogenic cell death(ICD)represents a modality of apoptosis distinguished by the emanation of an array of damage-related molecular signals.This mechanism introduces a novel concept in the field of contemporary tumor immunotherapy.The inception of reactive oxygen species(ROS)within tumor cells stands as the essential prerequisite and foundation for ICD induction.The formulation of highly efficacious photodynamic therapy(PDT)nanomedicines for the successful induction of ICD is an area of significant scientific inquiry.In this work,we devised a ROS-responsive and triple-synergistic mitochondria-targeted polymer micelle(CAT/CPT-TPP/PEG-Ce6,CTC)that operates with multistage amplification of ROS to achieve the potent induction of ICD.Utilizing an“all-in-one”strategy,we direct both the PDT and chemotherapeutic units to the mitochondria.Concurrently,a multistage cyclical amplification that caused by triple synergy strategy stimulates continuous,stable,and adequate ROS generation(domino effect)within the mitochondria of cells.Conclusively,influenced by ROS,tumor cell-induced ICD is effectively activated,remodeling immunogenicity,and enhancing the therapeutic impact of PDT when synergized with chemotherapy.Empirical evidence from in vitro study substantiates that CTC micelles can efficiently provoke ICD,catalyzing CRT translocation,the liberation of HMGB1 and ATP.Furthermore,animal trials corroborate that polymer micelles,following tail vein injection,can induce ICD,accumulate effectively within tumor tissues,and markedly inhibit tumor growth subsequent to laser irradiation.Finally,transcriptome analysis was carried out to evaluate the changes in tumor genome induced by CTC micelles.This work demonstrates a novel strategy to improve combination immunotherapy using nanotechnology.

A biomimetic and pH-sensitive polymeric micelle as carrier for paclitaxel delivery

As nano-scale drug delivery systems,smart micelles that are sensitive to specific biological environment and allowed for target site-triggered drug release by reversible stabilization of micelle structure are attractive.In this work,a biocompatible and pH-sensitive copolymer is synthesized through bridging poly(2-methacryloyloxyethyl phosphorylcholine)(PMPC)block and poly(D,L-lactide)(PLA)block by a benzoyl imine linkage(Blink).Biomimetic micelles with excellent biocompatibility based on such PLA-Blink-PMPC copolymer are prepared as carriers for paclitaxel(PTX)delivery.Due to the rapid breakage of the benzoyl imine linkage under acidic condition,the micelle structure is disrupted with accelerated PTX release.Such pH-sensitive triggered drug release behavior in synchronization with acidic conditions at tumor site is helpful for improving the utilization of drug and facilitating antitumor efficacy.These micelles can be used as promising drug delivery systems due to their biocompatible and smart properties.

聚合物胶束在纳米载药体系的应用研究进展

聚合物胶束具有能使难溶性药物有效增溶、粒径小、制备方法简单多样等独特优势,作为癌症诊疗的新型药物递送系统已引起广泛关注,但聚合物胶束的临床应用较少。介绍了聚合物胶束的制备和表征方法,综述了聚合物胶束在癌症治疗中的有效性及聚合物胶束制剂的临床应用,指出了其在临床应用中面临的挑战。

活性氧响应型鬼臼毒素聚合物前药胶束的制备及其抗口腔癌活性

目的制备基于透明质酸(HA)活性氧(ROS)响应型鬼臼毒素(POD)聚合物前药胶束(HTP-M),并考察其抑制口腔鳞状细胞癌(OSCC)效果。方法采用两步酯化法合成基于HA的ROS响应型POD聚合物前药HA-TK-POD,采用透析法制备聚合物前药胶束HTP-M,并对其形态特征、粒径、电位和载药量进行表征,同时考察ROS响应性药物释放。以SCC-9细胞和荷瘤小鼠为模型,考察HTP-M体内外抗肿瘤效果。结果磁共振氢谱(1 H-NMR)证实HA-TK-POD聚合物前药成功合成。所得HTP-M胶束呈类球形,粒径(126.1±3.5)nm,分布均一,Zeta电位(-26.8±1.9)mV。HTP-M载药量(12.3±0.8)%,具有良好ROS响应性。HTP-M可特异性靶向CD44高表达的SCC-9细胞,具有良好的体内外抗肿瘤效果。结论制备了一种基于HA的ROS响应型POD聚合物前药胶束HTP-M,其具有良好的ROS响应性,并可有效抑制OSCC,为临床OSCC的治疗提供了新策略。