Biodegradable poly(epsilon-caprolactone)-poly(ethylene glycol) block copolymers: characterization and their use as drug carriers for a controlled delivery system

A Nanoplatform with Precise Control over Release of Cargo for Enhanced Cancer Therapy

The development of a nanocarrier delivery system having both sufficient stability in blood circulation and a rapid drug release profile at target sites remains a major challenge in cancer therapy. Here, a multifunctional star-shaped micellar system with a precisely spatiotemporal control of releasing encapsulated agents is developed by mixing a photoinitiated crosslinking amphiphilic copolymer with a phenylboronic acid (PBA)-functionalized redox-sensitive amphiphilic copolymer for the first time. The combination of the functional polymers effectively resolves the contradiction that the micellar system cannot release the rapid drug release in cells when it possesses an extreme stability that is often required in blood circulation. In this system, the inner core polymers are photo-crosslinked, endowing a stable micelle matrix structure; the end groups of the hydrophilic segments are decorated with PBA ligands, providing an active targeting ability; disulfide bonds in the micellar matrix impart a redox-responsive trigger for the prompt intracellular release of drugs. As a result, with a relatively low DOX dosage (2 mg kg(-1) per injection) the in vivo antitumor effect on H22-bearing BALB/c mice shows that the micelles have a high therapeutic efficacy against solid tumors while minimal side effects against normal tissues.

In Vitro and In Vivo Evaluation of Targeted Sunitinib-Loaded Polymer Microbubbles Against Proliferation of Renal Cell Carcinoma

OBJECTIVES

The poor safety profile of sunitinib capsules has encouraged the identification of targeted drug delivery systems against renal cell carcinoma. This study aimed to explore the effect of sunitinib-loaded microbubbles along with ultrasound (US) treatment on proliferation and apoptosis of human GRC-1 granulocyte renal carcinoma cells in vitro and in vivo (xenograft tumor growth in nude mice).

METHODS

Liposomes containing sunitinib were prepared by using the transmembrane ammonium sulfate gradient method and then absorbed into polymer microbubbles to generate sunitinib-loaded microbubbles. Entrapment of sunitinib was verified by 25-25-[N-[(7-nitro-2-1,3-benzoxadiazol-4-yl)methyl]amino]-27-norcholesterol staining. GRC-1 cells were treated with microbubbles alone, liposomes alone, sunitinib alone, sunitinib-loaded microbubbles without and with US, and no treatment (control). Cell survival and apoptosis were assessed at 12, 24, and 48 hours after treatment. Xenograft tumors were induced by implantation of GRC-1 cells in nude mice. The animals with tumors were then randomly assigned to sunitinib alone, sunitinib-loaded microbubbles - US, sunitinib-loaded microbubbles + US, and no treatment (control; n = 10 per group). The tumor volumes were analyzed on the 7th, 15th, and 21st days.

RESULTS

The sunitinib entrapment efficiency in the liposomes was approximately 78%. The effective sunitinib concentration in each group was 0.1 μg/mL. The sunitinib-loaded microbubble + US group showed a lower in vitro cell survival rate (P < .001) compared with the other groups. Greater in vivo inhibition of xenograft tumor growth was also observed in the sunitinib-loaded microbubble + US group compared with the other groups.

CONCLUSIONS

Combined sunitinib-loaded microbubbles and US treatment significantly inhibits growth of renal carcinoma cells both in vitro and in vivo.

Poly(caprolactone)–poly(ethylene glycol)–poly(caprolactone) (PCL–PEG–PCL) nanoparticles: a valuable and efficient system for in vitro and in vivo delivery of curcumin

Curcumin was encapsulated within PCL–PEG–PCL micelles through a single-step nano-precipitation method, leading to the creation of CUR/PCL–PEG–PCL micelles..

Different oligoarginine modifications alter endocytic pathways and subcellular trafficking of polymeric nanoparticles

Different length of oligoarginine ligands alter both endocytic pathways and subcellular trafficking of PEG-b-PCL nanoparticles.

Biodegradable poly(ethylene glycol)–poly(ε-carprolactone) polymeric micelles with different tailored topological amphiphilies for doxorubicin (DOX) drug delivery

The self-assembly and drug release of the three PEG–PCL copolymers with different topologies but identical molar ratio between PEG to PCL.

Development and biodistribution of a theranostic aluminum phthalocyanine nanophotosensitizer

BACKGROUND

Aluminum phthalocyanine (AlPc) is an efficient second generation photosensitizer (PS) with high fluorescence ability. Its use in photodynamic therapy (PDT) is hampered by hydrophobicity and poor biodistribution.

METHODS

AlPc was converted to a biocompatible nanostructure by incorporation into amphiphilic polyethylene glycol-polycaprolactone (PECL) copolymer nanoparticles, allowing efficient entrapment of the PS in the hydrophobic core, water dispersibility and biodistribution enhancement by PEG-induced surface characteristics. A series of synthesized PECL copolymers were used to prepare nanophotosensitizers with an average diameter of 66.5-99.1nm and encapsulation efficiency (EE%) of 66.4-78.0%. One formulation with favorable colloidal properties and relatively slow release over 7 days was selected for in vitro photophysical assessment and in vivo biodistribution studies in mice.

RESULTS

The photophysical properties of AlPc were improved by encapsulating AlPc into PECL-NPs, which showed intense fluorescence emission at 687nm and no AlPc aggregation has been induced after entrapment into the nanoparticles. Biodistribution of AlPc loaded NPs (AlPc-NPs) and free AlPc drug in mice was monitored by in vivo whole body fluorescence imaging and ex vivo organ imaging, with in vivo imaging system (IVIS). Compared to a AlPc solution in aqueous TWEEN 80 (2 w/v%), the developed nanophotosensitizer showed targeted drug delivery to lungs, liver and spleen as monitored by the intrinsic fluorescence of AlPc at different time points (1h, 24h and 48h) post iv. administration.

CONCLUSIONS

The AlPc-based copolymer nanoparticles developed offer potential as a single agent-multifunctional theranostic nanophotosensitizer for PDT coupled with imaging-guided drug delivery and biodistribution, and possibly also fluorescence diagnostics.

Incorporation of aligned PCL-PEG nanofibers into porous chitosan scaffolds improved the orientation of collagen fibers in regenerated periodontium

The periodontal ligament (PDL) is a group of highly aligned and organized connective tissue fibers that intervenes between the root surface and the alveolar bone. The unique architecture is essential for the specific physiological functionalities of periodontium. The regeneration of periodontium has been extensively studied by researchers, but very few of them pay attention to the alignment of PDL fibers as well as its functionalities. In this study, we fabricated a three-dimensional multilayered scaffold by embedding highly aligned biodegradable poly (ε-caprolactone)-poly(ethylene glycol) (PCE) copolymer electrospun nanofibrous mats into porous chitosan (CHI) to provide topographic cues and guide the oriented regeneration of periodontal tissue. In vitro, compared with random group and porous control, aligned nanofibers embedded scaffold could guide oriented arrangement and elongation of cells with promoted infiltration, viability and increased periodontal ligament-related genes expression. In vivo, aligned nanofibers embedded scaffold showed more organized arrangement of regenerated PDL nearly perpendicular against the root surface with more extensive formation of mature collagen fibers than random group and porous control. Moreover, higher expression level of periostin and more significant formation of tooth-supporting mineralized tissue were presented in the regenerated periodontium of aligned scaffold group. Incorporation of aligned PCE nanofibers into porous CHI proved to be applicable for oriented regeneration of periodontium, which might be further utilized in regeneration of a wide variety of human tissues with a specialized direction.

STATEMENT OF SIGNIFICANCE

The regeneration of periodontium has been extensively studied by researchers, but very few of them give attention to the alignment of periodontal ligament (PDL) fibers as well as its functionalities. The key issue is to provide guidance to the orientation of cells with aligned arrangement of collagen fibers perpendicular against the root surface. This study aimed to promote oriented regeneration of periodontium by structural mimicking of scaffolds. The in vitro and in vivo performances of the scaffolds were further evaluated to test the topographic-guiding and periodontium healing potentials. We also think our research may provide ideas in regeneration of a wide variety of human tissues with a specialized direction.

Drug Carrier for Photodynamic Cancer Therapy

Photodynamic therapy (PDT) is a non-invasive combinatorial therapeutic modality using light, photosensitizer (PS), and oxygen used for the treatment of cancer and other diseases. When PSs in cells are exposed to specific wavelengths of light, they are transformed from the singlet ground state (S₀) to an excited singlet state (S₁-Sn), followed by intersystem crossing to an excited triplet state (T₁). The energy transferred from T₁ to biological substrates and molecular oxygen, via type I and II reactions, generates reactive oxygen species, (¹O₂, H₂O₂, O₂*, HO*), which causes cellular damage that leads to tumor cell death through necrosis or apoptosis. The solubility, selectivity, and targeting of photosensitizers are important factors that must be considered in PDT. Nano-formulating PSs with organic and inorganic nanoparticles poses as potential strategy to satisfy the requirements of an ideal PDT system. In this review, we summarize several organic and inorganic PS carriers that have been studied to enhance the efficacy of photodynamic therapy against cancer.

Full factorial design optimization of anti-inflammatory drug release by PCL-PEG-PCL microspheres

A biodegradable triblock poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) copolymer was successfully synthesized by ring-opening polymerization of ε-caprolactone, and was characterized by intrinsic viscosimetry, (1)H nuclear magnetic resonance, infrared spectroscopy and X-ray diffraction. Copolymer microparticles loaded with ibuprofen were prepared by an oil-in-water (o/w) emulsion solvent evaporation process. They were carefully weighted and characterized through their zeta potential. In this work, 4 selected process parameters (shaking speed X1, time of contact X2, poly(vinyl alcohol) concentration X3, and ibuprofen concentration X4) were adjusted at 2 different values. For each of the 16 experimental conditions, repeated twice, the drug encapsulation efficiency of the microspheres was determined, according to the following definition: EE (X1, X2, X3, X4)=mass of encapsulated ibuprofen/total weight of ibuprofen. A "full factorial design method" was applied to analyze the results statistically according to a polynomial fit and to determine the optimal conditions for the microencapsulation of the ibuprofen through an accurate statistical protocol. The microparticles obtained exhibit a spherical shape as shown by electron microscopy.

Synthesis and evaluation of MePEG-PCL diblock copolymers: surface properties and controlled release behavior

The amphiphilic block copolymers are composed of various combinations of hydrophilic and hydrophobic block unimers. The variation in unimer ratio alters the surface as well as micelle-forming properties of the block copolymers. These nanoscopic micelles have the ability to encapsulate hydrophobic compounds and act as potential drug carrier. MePEG-PCL copolymers with various block lengths were synthesized by ring-opening polymerization and characterized by ¹HNMR, GPC, WXRD and DSC. The number average molecular weight of the block copolymer was found to vary from 7511 to 21,270 as determined by GPC and ¹HNMR studies. The surface topology of the polymer films was determined by AFM analysis, which shows a smoother surface with increased MePEG contents in the block copolymers. The protein-binding assay indicates a better biocompatibility of the block copolymers in comparison to MePEG or PCL alone. The CMC of the block copolymer provides the information about micelle formations for encapsulation of hydrophobic materials and affects the in vitro release.

pH-Responsive Shape Memory Poly(ethylene glycol)-Poly(ε-caprolactone)-based Polyurethane/Cellulose Nanocrystals Nanocomposite

In this study, we developed a pH-responsive shape-memory polymer nanocomposite by blending poly(ethylene glycol)-poly(ε-caprolactone)-based polyurethane (PECU) with functionalized cellulose nanocrystals (CNCs). CNCs were functionalized with pyridine moieties (CNC-C6H4NO2) through hydroxyl substitution of CNCs with pyridine-4-carbonyl chloride and with carboxyl groups (CNC-CO2H) via 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO) mediated surface oxidation, respectively. At a high pH value, the CNC-C6H4NO2 had attractive interactions from the hydrogen bonding between pyridine groups and hydroxyl moieties; at a low pH value, the interactions reduced or disappeared due to the protonation of pyridine groups, which are a Lewis base. The CNC-CO2H responded to pH variation in an opposite manner. The hydrogen bonding interactions of both CNC-C6H4NO2 and CNC-CO2H can be readily disassociated by altering pH values, endowing the pH-responsiveness of CNCs. When these functionalized CNCs were added in PECU polymer matrix to form nanocomposite network which was confirmed with rheological measurements, the mechanical properties of PECU were not only obviously improved but also the pH-responsiveness of CNCs could be transferred to the nanocomposite network. The pH-sensitive CNC percolation network in polymer matrix served as the switch units of shape-memory polymers (SMPs). Furthermore, the modified CNC percolation network and polymer molecular chains also had strong hydrogen bonding interactions among hydroxyl, carboxyl, pyridine moieties, and isocyanate groups, which could be formed or destroyed through changing pH value. The shape memory function of the nanocomposite network was only dependent on the pH variation of the environment. Therefore, this pH-responsive shape-memory nancomposite could be potentially developed into a new smart polymer material.

Shish-kebab-structured poly(ε-caprolactone) nanofibers hierarchically decorated with chitosan-poly(ε-caprolactone) copolymers for bone tissue engineering

In this work, scaffolds with a shish-kebab (SK) structure formed by poly(ε-caprolactone) (PCL) nanofibers and chitosan-PCL (CS-PCL) copolymers were prepared via electrospinning and subsequent crystallization for bone tissue engineering applications. The aim of this study was to introduce nanosized topography and the high biocompatibility of chitosan onto PCL nanofibers to enhance cell affinity to PCL scaffolds. CS-PCL copolymers with various ratios were synthesized, and then spontaneously crystallized as kebabs onto the electrospun PCL fibers, which acted as shishes. Scanning electron microscopy (SEM) results demonstrated that the copolymer with PCL to chitosan ratio of 8.8 could hierarchically decorate the PCL nanofibers and formed well-shaped kebabs on the PCL nanofiber surface. Water contact angle tests and biomimetic activity experiments revealed that the shish-kebab scaffolds with CS-PCL kebabs (PCL-SK(CS-PCL(8.8))) showed enhanced hydrophilicity and mineralization ability compared with smooth PCL and PCL-SK(PCL) shish-kebab scaffolds. Osteoblast-like MG63 cells cultured on the PCL-SK(CS-PCL(8.8)) scaffolds showed optimizing cell attachment, cell viability, and metabolic activity, demonstrating that this kind of scaffold has potential applications in bone tissue engineering.

Multi-stimulus-responsive shape-memory polymer nanocomposite network cross-linked by cellulose nanocrystals

In this study, we developed a thermoresponsive and water-responsive shape-memory polymer nanocomposite network by chemically cross-linking cellulose nanocrystals (CNCs) with polycaprolactone (PCL) and polyethylene glycol (PEG). The nanocomposite network was fully characterized, including the microstructure, cross-link density, water contact angle, water uptake, crystallinity, thermal properties, and static and dynamic mechanical properties. We found that the PEG[60]-PCL[40]-CNC[10] nanocomposite exhibited excellent thermo-induced and water-induced shape-memory effects in water at 37 °C (close to body temperature), and the introduction of CNC clearly improved the mechanical properties of the mixture of both PEG and PCL polymers with low molecular weights. In addition, Alamar blue assays based on osteoblasts indicated that the nanocomposites possessed good cytocompatibility. Therefore, this thermoresponsive and water-responsive shape-memory nanocomposite could be potentially developed into a new smart biomaterial.

Dynamically tunable polymer microwells for directing mesenchymal stem cell differentiation into osteogenesis

Dynamically tunable geometric microwells have great capacity to regulate the cytoskeletal structure and differentiation of mesenchymal stem cells along adipogenesis and osteogenesis pathways.

Enzyme mimetic-catalyzed ATRP and its application in block copolymer synthesis combined with enzymatic ring-opening polymerization

Use of an enzyme mimetic (DhHP-6) as an ATRP catalyst for the synthesis of a series of functional polymers.

The control of mesenchymal stem cell differentiation using dynamically tunable surface microgrooves

Many studies have demonstrated the potential to modulate stem cell differentiation by using static material substrate surfaces. However, cells actually grow in a dynamically diverse microenvironment in vivo. The regulated signals to the differentiation provided by these materials should not be passive or static but be active and dynamic. To mimic the endogenous cell culture microenvironment, a novel system is designed to realize the dynamic change of the surface geometries as well as a resultant mechanical force using a thermally activated four-stage shape memory polymer. The parallel microgroove surface patterns are fabricated via thermal embossing lithography on the polymer substrate surface. The dynamic microgroove surfaces accompanying with the mechanical force can effectively and significantly regulate the shape and the cytoskeletal arrangement of rBMSC compared with the static patterned and non-patterned surfaces. Cellular and molecular analyses reveal that the spatiotemporally programmed regulation of cell shape is more viable to coax lineage-specific differentiation of stem cell in contrast to the general reports with the static surfaces. Therefore, this study provides a facile strategy in designing and manufacturing an artificial substrate with a mimic natural cellular environment to precisely direct the cell differentiation.

Thermoresponsive polymers: insights into decisive hydrogel characteristics, mechanisms of gelation, and promising biomedical applications

Thermally induced gelling systems have gained enormous attention over the last decade. They consist of hydrophilic homopolymers or block copolymers in water that present a sol at room temperature and form a gel after administration into the body. This article reviews the main types of thermoresponsive polymers, with special focus on decisive hydrogel characteristics, mechanisms of gelation, and biocompatibility. Promising biomedical applications are described with a focus on injectable formulations, which include solubilization of small hydrophobic drugs, controlled release, delivery of labile biopharmaceutics, such as proteins and genes, cell encapsulation, and tissue regeneration. Furthermore, combinations of thermoresponsive hydrogels and various nanocarriers as promising systems for sustained drug delivery are discussed through selected examples from the literature. Finally, there is a brief overview of current progress in nano-sized systems incorporating thermoresponsive properties.

Thermo-triggered drug release from actively targeting polymer micelles

How to deliver the drug to the target area at the right time and at the right concentration is still a challenge in cancer therapy. In this study, we present a facile strategy to control drug release by precisely controlling the thermo-sensitivity of the nanocarriers to the variation of environmental temperature. One type of thermoresponsive Pluronic F127-poly(d,l-lactic acid) (F127-PLA, abbreviated as FP) copolymer micelles was developed and decorated with folate (FA) for active targeting. FP100 micelles assembled from FP with PLA segment having polymerization degree of 100 had a low critical solution temperature of 39.2 °C close to body temperature. At 37 °C, little amount of encapsulated anticancer drug DOX is released from the FP100 micelles, while at a slightly elevated temperature (40 °C), the shrinkage of thermoresponsive segments causes a rapid release of DOX and instantly increases the drug concentration locally. The cytocompatibility analysis and cellular uptake efficiency were characterized with the fibroblast cell line NIH 3T3 and human cervix adenocarcinoma cell line HeLa. The results demonstrate that this copolymer has excellent cytocompatibility, and FA-decorated FP100 micelles present much better efficiency of cellular uptake and higher cytotoxicity to folate receptor (FR)-overexpressed HeLa cells. In particular, under hyperthermia (40 °C) the cytotoxicity of DOX-loaded FA-FP100 micelles against HeLa cells was significantly more obvious than that upon normothermia (37 °C). Therefore, these temperature-responsive micelles have great potential as a drug vehicle for cancer therapy.

In vitro evaluation of effects of sustained anti-TNF release from MPEG-PCL-MPEG and PCL microspheres on human rheumatoid arthritis synoviocytes

Anti-tumor necrosis factor α (TNFα) drugs such as etanercept (ETN) have been mostly used in systemic treatment of rheumatoid arthritis. To eliminate the side effects in long-term treatments and to achieve a local sustained anti-inflammatory effect, a controlled drug delivery system is needed for anti-TNFα drugs. This study aims to develop novel injectable microcarriers of ETN that can provide long-term controlled release of this protein drug upon intra-articular application. In this study, poly(ε-caprolactone) (PCL) and its copolymer with poly(ethylene glycol), methoxypoly(ethylene glycol)-poly(ε-caprolactone)-methoxypoly(ethylene glycol) microspheres (MPEG-PCL-MPEG) were compared for their prospective success in rheumatoid arthritis treatment. Microspheres with smooth surface of a mean particle diameter of approximately 5 μm were prepared with both polymers. MPEG-PCL-MPEG microspheres had higher encapsulation efficiency than PCL microspheres. The activity of encapsulated ETN within MPEG-PCL-MPEG microspheres also retained while 90% of the activity of ETN within PCL microspheres could retain during 90-day release. MPEG-PCL-MPEG microspheres showed faster ETN release compared to PCL microspheres in various release media. Cumulative amounts of ETN released from both types of microspheres were significantly lower in cell culture medium and in synovial fluids than in phosphate buffered saline. This was mainly due to protein adsorption onto microspheres. Hydrophilic MPEG segment enhanced ETN release while preventing protein adsorption on microspheres compared to PCL. Sustained ETN release from microspheres resulted with a significant decrease in pro-inflammatory cytokines (TNFα, IFNγ, IL-6, IL-17) and MMP levels (MMP-3, MMP-13), while conserving viability of fibroblast-like synoviocytes compared to the free drug. Results suggest that MPEG-PCL-MPEG is a potential copolymer of PCL that can be used in development of biomedical materials for effective local treatment purposes in chronic inflammatory arthritis owing to enhanced hydrophilicity. Yet, PCL microspheres are also promising systems having good compatibility to synoviocytes and would be especially the choice for treatment approach requiring longer term and slower release.

Polymersomes as an effective drug delivery system for glioma--a review

Glioma is one of the most commonly occurring malignant brain tumours which need proper treatment strategy. The current therapies for treating glioma like surgical resection, radiotherapy, and chemotherapy have failed in achieving satisfactory results and this forms a rationale for the development of novel drug delivery systems. Among them, polymersomes are superior novel carriers with diverse functions like enhanced stability, low permeability, tunable membrane properties, surface functionality, and long blood circulation time which make them suitable for cancer therapy. These are bilayered vesicles capable of encapsulating both hydrophilic and hydrophobic drugs used to target glioma effectively. In this review, we have discussed on general preparation, characterization, and targeting aspects of surface modified polymersomes for effective delivery of therapeutic agents to glioma.