Amphiphilic biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) triblock copolymers: synthesis, characterization and their use as drug carriers for folic acid

Construction of a Drug Delivery System via pH-Responsive Polymeric Nanomicelles Containing Ferrocene for DOX Release and Enhancement of Therapeutic Effects

We report an amphiphilic block copolymer via poly(ethylene glycol) methyl ether-D_labile-poly(caprolactone)-ferrocene (mPEG-D_labile-PCL-Fc) to deliver anticancer drug doxorubicin (DOX). Lipase Novozyme-435 was used as a catalyst for ring-opening polymerization with ε-caprolactone, and an acid-sensitive Schiff base was used to connect the hydrophilic and hydrophobic parts; the ferrocene provided ferrous ions and was introduced at the end of the amphiphilic copolymer. The resulting copolymers were characterized by ¹H NMR/¹³C NMR and could be self-assembled in an aqueous solution to form nanomicelles with PCL-Fc as a hydrophobic core and mPEG as a hydrophilic shell. Transmission electron microscopy showed that the micelles were spherical and nanosized before and after DOX loading. The blank micelles also showed good biocompatibility. The drug-loaded polymeric nanomicelles exhibited a positive anticancer effect relative to the copolymers without ferrocene; the therapeutic effect of drug-loaded micelles containing ferrocene was more obvious. In vitro drug release results also showed that the polymer had a good pH response. Confocal microscopy also showed that polymeric micelles can effectively deliver and release the drug; the polymer containing ferrocene also leads to significantly improved ROS levels in tumor cells. Ferrocene can effectively and synergistically inhibit tumor cells with DOX.

Organocatalyzed ring-opening copolymerization of α-bromo-γ-butyrolactone with ε-caprolactone for the synthesis of functional aliphatic polyesters - pre-polymers for graft copolymerization

Diphenyl phosphate (DPP) was exploited as an organocatalyst to synthesize copolymers by ring-opening polymerization with α-bromo-γ-butyrolactone (αBrγBL) and ε-caprolactone (εCL) as monomers and polyethylene glycol (PEG) as initiator. The conversion rates of monomers and molecular weights of copolymers synthesized under different conditions were determined by ¹H-NMR. The ¹H-NMR results showed that the copolymers of αBrγBL and εCL initiated by PEG (PEGCB) were successfully synthesized and the conversions of εCL were relatively high (＞70%), while the conversions of αBrγBL were relatively low (＜26%). The highest molar ratio of αBrγBL to εCL units in these copolymers is 0.17, when the copolymerization was carried out at 100℃ for 17h.

The bromine atoms hanged on the chain of the copolymers PEGCB provide a good opportunity to construct graft copolymers via atom transfer radical polymerization (ATRP). The subsequent grafting of 2-(dimethylamino)ethyl methacrylate (DMAEMA) was conducted by using PEGCB3 as macroinitiator, CuBr/N,N’,N’,N”,N”- pentamethyldiethylenetriamine (PMDETA) as catalysts and toluene/anisole as solvents via ATRP. According to the analysis of ¹H-NMR, the grafting efficiency, grafting ratio and grafting frequency were 22.4%, 160.7% and 1133.8, respectively.

Investigation of cationized triblock and diblock poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers for oral delivery of enoxaparin: In vitro approach

In this study, poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers grafted with a cationic ligand, propargyltrimethyl ammonium iodide (PTA), to fabricate the cationized triblock (P(CatCLCL)₂-PEG) and diblock (P(CatCLCL)-mPEG) copolymers were investigated their potential use for oral delivery of enoxaparin (ENX). Influences of various PTA contents and different structures of the copolymers on molecular characteristics, ENX encapsulation, particle characteristics, and capability of drug transport across Caco-2 cells were elucidated. The results showed that P(CatCLCL)₂-PEG and P(CatCLCL)-mPEG copolymers self-aggregated and encapsulated ENX into spherical particles of ∼200-450nm. The increasing amount of PTA on the copolymers increased encapsulation efficiency of over 90%. The ENX release from both types of the cationized copolymer particles was pH-dependent which was retarded at pH 1.2 and accelerated at pH 7.4, supporting the drug protection in the acidic environment and possible release in the blood circulation. The toxicity of ENX-loaded particles on Caco-2 cells decreased when decreasing the amount of PTA. The triblock and diblock particles dramatically enhanced ENX uptake and transport across Caco-2 cells as compared to the ENX solution. However, the different structures of the copolymers slightly affected ENX transport. These results suggested that P(CatCLCL)₂-PEG and P(CatCLCL)-mPEG copolymers would be potential carriers for oral delivery of ENX.

STATEMENT OF SIGNIFICANCE

The anionic drugs such as proteins, peptides or polysaccharides are generally administered via invasive route causing patient incompliance and high cost of hospitalization. The development of biomaterials for non-invasive delivery of those drugs has gained much attention, especially for oral delivery. However, they have limitation due to non-biocompatibility and poor drug bioavailability. In this study, the novel poly(ε-caprolactone)-co-poly(ethylene glycol) copolymers grafted with propargyltrimethyl ammonium iodide, a small cationic ligand, were introduced to use as a carrier for oral delivery of enoxaparin, a highly negatively charged drug. The study showed that these cationized copolymers could achieve high enoxaparin entrapment efficiency, protect drug release in an acidic environment and enhance enoxaparin permeability across Caco-2 cells, the intestinal cell model. These characteristics of the cationized copolymers make them a potential candidate for oral delivery of anionic drugs for biomaterial applications.

Preparation of curcumin-loaded PCL-PEG-PCL triblock copolymeric nanoparticles by a microchannel technology

Biodegradable polymeric nanoparticles (NPs) have potential therapeutic applications; however, preparing NPs of a specific diameter and uniform size distribution is a challenge. In this work, we fabricated a microchannel system for the preparation of curcumin (Cur)-loaded NPs by the interfacial precipitation method, which rapidly and consistently generated stable NPs with a relatively smaller diameter, narrow size distribution, and higher drug-loading capacity and entrapment efficiency. Poly(ε-caprolactone)-poly(ethylene glycol)-poly (ε-caprolactone) triblock copolymers(PCEC) used as the carrier material was synthesized and characterized. Cur-loaded PCEC NPs had an average size of 167.2nm with a zeta potential of -29.23mV, and showed a loading capacity and drug entrapment efficiency of 15.28%±0.23% and 96.11%±0.13%, respectively. Meanwhile, the NPs demonstrated good biocompatibility and bioavailability, efficient cellular uptake, and long circulation time and a possible liver targeting effect in vivo. These results indicate that the Cur-loaded PCEC NPs can be used as drug carriers in controlled delivery systems and other biomedical applications.

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..

Synthesis and self-assembly behaviour of poly(Nα-Boc-l-tryptophan)-block-poly(ethylene glycol)-block-poly(Nα-Boc-l-tryptophan)

We report for the first time the use of Nα-Boc-l-tryptophan for the synthesis of amphiphilic BAB triblock copolymers for potential drug delivery applications.

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.

From nanospheres to micelles: simple control of PCL-g-PEG copolymers’ amphiphilicity through thiol–yne photografting

A unique combination of polyester post-polymerization modification and photoradical thiol–yne addition is reported for the synthesis of amphiphilic degradable graft copolymers with controlled compositions, used to prepare micelles or nanospheres.

Folate-conjugated amphiphilic block copolymers for targeted and efficient delivery of doxorubicin

In this paper, novel biodegradable amphiphilic block copolymers based on folate-conjugated poly(ethylene glycol)-b-copolycarbonates (FA-PEG-b-P(MAC-co-DTC)) and methoxy poly(ethylene glycol)-b-copolycarbonates (mPEG-b-P(MAC-co-DTC)) were successfully synthesized for targeted and efficient delivery of doxorubicin (DOX) to cancer cells. Immobilized porcine pancreas lipase (IPPL) was employed as the catalyst to perform the ring-opening copolymerization in bulk, while the folate-conjugated poly(ethylene glycol) (FA-PEG) or methoxy poly(ethylene glycol) (mPEG) was used as the initiator. The resulting copolymers, characterized by (1)H NMR and GPC, could self-assemble to form nano-sized micelles in aqueous solution by dialysis method. P(MAC-co-DTC) acted as the hydrophobic core, thereby aggregating hydrophilic PEG chains as the outer shell with FA as targeting ligand located at the surface of the polymeric micelles. Transmission electron microscopy (TEM) observation showed that the micelles dispersed in spherical shape with nano-size before and after DOX loading. Both the FA-conjugated and non-conjugated block copolymers showed low cellular cytotoxicity. Furthermore, as compared to the non-conjugated copolymers, much more efficient cellular uptake of the FA-conjugated copolymers via FA-receptor-mediated endocytosis could be observed by confocal laser scanning microscopy (CLSM), while MTT assays also demonstrated highly potent cytotoxic activity against HeLa cells.

Rapamycin-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) nanoparticles: preparation, characterization and potential application in corneal transplantation

OBJECTIVES

Allograft rejection is the major cause of corneal graft failure. To inhibit corneal allograft rejection, rapamycin as a novel immunosuppressive agent has been discovered. However, the high water insolubility and low bioavailability of rapamycin has strongly hindered its application in the clinical setting. In this paper, we attempted to develop a novel rapamycin nano-formulation using poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCEC) nanoparticles as carrier by an emulsion evaporation method for potential application in corneal transplantation.

METHODS

The solubility of rapamycin in the nano-formulation was determined and in-vitro release studies were performed. The developed rapamycin-loaded PCEC nanoparticles were further characterized by dynamic light scattering, transmission electron microscopy, X-ray diffraction and differential scanning calorimetery. Toxicity studies were performed in eye-related cell lines.

KEY FINDINGS

The rapamycin in nano-formulation exhibited ∼10³-fold increased solubility as compared with native rapamycin. According to the results of the in-vitro cytotoxicity assay, the developed PCEC nanoparticles did not exhibit any apparent cytotoxicity against various eye-related cell lines with PCEC nanoparticle concentrations in the range of 0.05-10 mg/ml. In-vitro release study showed that the release of rapamycin was sustained from PCEC nanoparticles over a period of 48 h.

CONCLUSIONS

All the results suggested that the developed rapamycin-loaded PCEC nanoparticles might be suitable for immunosuppression in corneal transplantation by instillation administration.

Thermosensitive β-cyclodextrin modified poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) micelles prolong the anti-inflammatory effect of indomethacin following local injection

A novel biodegradable and injectable in situ gel-forming controlled drug delivery system based on thermosensitive β-cyclodextrin-modified poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) co-polymer (PCEC-β-CD) was studied in this work. The drug encapsulating capacity has been improved by introducing β-CD bound to the PCEC co-polymer. The prepared PCEC-β-CD co-polymers self-assembled in water to form micelles, and underwent a temperature-dependent gel-sol transition, which was in the form of a flowing injectable solution at low temperatures but became a non-flowing gel at around physiological body temperature. Furthermore, a small hydrophobic drug molecule indomethacin (IND) was successfully encapsulated in PCEC-β-CD micelles by dialysis at a high encapsulation efficiency and drug loading capacity. The IND-loaded micelles (IND-M) exhibited controlled release in vitro. Additionally, a pharmacodynamic study in vivo based on both the carrageenan-induced acute and complete Freund's adjuvant-induced adjuvant arthritis models indicated that sustained therapeutic efficacy could be achieved through subcutaneous injection of IND-loaded micelles. A significant improvement in the anti-inflammatory effect of IND in rats occurred on encapsulation in PCEC-β-CD micelles.

Doxorubicin-Loaded PEG-PCL-PEG Micelle Using Xenograft Model of Nude Mice: Effect of Multiple Administration of Micelle on the Suppression of Human Breast Cancer

The triblock copolymer is composed of two identical hydrophilic segments Monomethoxy poly(ethylene glycol) (mPEG) and one hydrophobic segment poly(ε-caprolactone) (PCL); which is synthesized by coupling of mPEG-PCL-OH and mPEG-COOH in a mild condition using dicyclohexylcarbodiimide and 4-dimethylamino pyridine. The amphiphilic block copolymer can self-assemble into nanoscopic micelles to accommodate doxorubixin (DOX) in the hydrophobic core. The physicochemical properties and in vitro tests, including cytotoxicity of the micelles, have been characterized in our previous study. In this study, DOX was encapsulated into micelles with a drug loading content of 8.5%. Confocal microscopy indicated that DOX was internalized into the cytoplasm via endocystosis. A dose-finding scheme of the polymeric micelle (placebo) showed a safe dose of PEG-PCL-PEG micelles was 71.4 mg/kg in mice. Importantly, the circulation time of DOX-loaded micelles in the plasma significantly increased compared to that of free DOX in rats. A biodistribution study displayed that plasma extravasation of DOX in liver and spleen occurred in the first four hours. Lastly, the tumor growth of human breast cancer cells in nude mice was suppressed by multiple injections (5 mg/kg, three times daily on day 0, 7 and 14) of DOX-loaded micelles as compared to multiple administrations of free DOX.