Preparation of curcumin loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) nanofibers and their in vitro antitumor activity against Glioma 9L cells

The purpose of this work was to develop implantable curcumin-loaded poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone) (PCL-PEG-PCL, PCEC) nanofibers, which might have potential application in cancer therapy. Curcumin was incorporated into biodegradable PCEC nanofibers by electrospinning method. The surface morphology of the composite nanofibers was characterized on Scanning Electron Microscope (SEM). The average diameter of the nanofibers was 2.3-4.5μm. In vitro release behavior of curcumin from the fiber mats was also studied in detail. The in vitro cytotoxicity assay showed that the PCEC fibers themselves did not affect the growth of rat Glioma 9L cells. Antitumor activity of the curcumin-loaded fibers against the cells was kept over the whole experiment process, while the antitumor activity of pure curcumin disappeared within 48 h. These results strongly suggested that the curcumin/PCEC composite nanofibers might have potential application for postoperative chemotherapy of brain cancers.     

Improving anti-tumor activity with polymeric micelles entrapping paclitaxel in pulmonary carcinoma

Nanoscale polymeric micelles have promising applications as drug delivery systems (DDS). In this work, to improve the anti-tumor activity and eliminate toxicity of the commercial formulation (cremophor EL and ethanol) of paclitaxel (PTX), we developed biodegradable poly(ethylene glycol)-poly(ε-caprolactone) (MPEG-PCL) micelles entrapping PTX by a simple one-step solid dispersion method, which is without any surfactants or additives and is easy to scale up. In addition, the PTX micelles could be lyophilized into powder without any adjuvant and the re-dissolved PTX micelles are stable and homogeneous. The prepared PTX micelles have a mean particle size of 38.06 ± 2.30 nm, a polydispersity index of 0.168 ± 0.014, a drug loading of 14.89 ± 0.06% and an encapsulation efficiency of 99.25 ± 0.38%. A molecular modeling study implied that PTX interacted with PCL as a core, which was embraced by PEG as a shell. The encapsulation of PTX in polymeric micelles enhanced its cytotoxicity by increasing the uptake by LL/2 cells. A sustained in vitro release behavior and slow extravasation behavior from blood vessels in a transgenic zebrafish model were observed in the PTX micelles. Furthermore, compared with Taxol?, the PTX micelles were more effective in suppressing tumor growth in the subcutaneous LL/2 tumor model. The PTX micelles also inhibited metastases in the pulmonary metastatic LL/2 tumor model and prolonged survival in both mouse models. Pharmacokinetic and tissue distribution studies showed that after PTX was encapsulated in polymeric micelles, the biodistribution pattern of PTX was altered and the PTX concentration in tumors was increased compared with Taxol? after intravenous injection. In conclusion, we have developed a polymeric micelles entrapping PTX that enhanced cytotoxicity in vitro and improved anti-tumor activity in vivo with low systemic toxicity on pulmonary carcinoma. The biodegradable MPEG-PCL micelles entrapping PTX may have promising applications in pulmonary carcinoma therapy.     

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

Amphiphilic biodegradable poly(ε-caprolactone)-poly(ethylene glycol)-poly (ε-caprolactone) (PCEC) triblock copolymers have been successfully synthesized by the ring-opening polymerization of ε-caprolactone (ε-CL) employing SnOct as catalyst and double-hydroxyl capped PEG (DHPEG) as macro-initiator. The triblock structure and copolymer composition were conformed by FT-IR, ¹H-NMR, and GPC. Using a membrane dialysis method, PCEC micelles were prepared with a core–shell type. The critical micelle concentration (CMC) of PCEC triblock copolymers was determined by fluorescence technique using pyrene as probe, and CMC values decreased with the increase of PCL chain length. From the observation of transmission electron microscopy (TEM), the morphology of polymer micelles was spherical in shape. Micelles size measured by dynamic light scattering (DLS) exhibited a narrow size distribution. Folic acid (FA) was then used as a model drug to incorporate into PCEC micelles. The diameter, drug loading, and drug release rate of PCEC micelles were influenced by the feed weight ratio of FA and copolymer, and polymer composition. In addition, in vitro release experiments of the drug-loaded PCEC micelles exhibited sustained release behavior without any burst effects and the release behavior was also affected by the pH of release media.     

Therapeutic application of injectable thermosensitive hydrogel in preventing local breast cancer recurrence and improving incision wound healing in a mouse model

Many drug delivery systems (DDSs) have been investigated for local targeting of malignant disease with the intention of increasing anti-tumor activity and minimizing systemic toxicity. An injectable thermosensitive hydrogel was applied to prevent locoregional recurrence of 4T1 breast cancer in a mouse model. The presented hydrogel, which is based on poly(ethyleneglycol)-poly(ε-caprolactone)-poly(ethylene glycol) (PEG-PCL-PEG, PECE), flows freely at normal temperature, forms a gel within seconds in situ at body temperature, and eventually releases the drug in a consistent and sustained fashion as it gradually biodegrades. Locoregional recurrence after primary tumor removal was significantly inhibited in mice treated with the paclitaxel (PTX)-loaded PECE hydrogel subcutaneously (9.1%) administered, compared with the blank hydrogel (80.0%), systemic (77.8%) and locally (75.0%) administered PTX, and the control group (100%) (P < 0.01). In addition, tensile strength measurements of the surgical incisions showed that the PECE hydrogel accelerates wound healing at postoperative day 7 (P < 0.05), and days 4 and 14 (P > 0.05), in agreement with histopathological examinations. This novel DDSs represents a promising approach for local adjuvant therapy in malignant disease.     

Thermosensitive poly(N-isopropylacrylamide)-b-poly(ε-caprolactone) nanoparticles for efficient drug delivery system

To investigate thermosensitive polymeric nanoparticle, amphiphilic block copolymers of poly(N-isopropylacrylamice)-b-poly(ε-caprolactone) (PNPCL) with different PCL block lengths were synthesized by hydroxy-terminated poly(N-isopropyoacrylamide) (PNiPAAm) initiated ring opening polymerization of ε-caprolactone. Owing to their amphiphilic characteristics, the block copolymers formed self-assembled polymeric nanoparticles in aqueous milieus with thermosensitive PNiPAAm shell compartment. The characterizations of the nanoparticles revealed that the PNPCL nanoparticles showed PCL block length dependent physicochemical characters such as particle sizes, critical aggregation concentrations, and core hydrophobicities. Moreover, the thermosensitive PNiPAAm shells conferred unique temperature responsive properties such as phase transitions with temperature elevation over its lower critical solution temperature (LCST). The temperature induced phase transition resulted in the formation of PNiPAAm hydrogel layer on the PNPCL nanoparticle surface. The drug release tests revealed that the formation of thermosensitive hydrogel layer resulted in the enhanced sustained drug release patterns by acting as an additional diffusion barriers. Therefore, the introduction of thermosensitive polymers on polymeric nanoparticles might be a potential approaches to modulate drug release behaviors.     

Multifunctional and thermoresponsive unimolecular micelles for tumor-targeted delivery and site-specifically release of anticancer drugs

Considering the fact that tumors have a lower pH value and a higher temperature than a normal tissue, a new type of thermoresponsive and biodegradable micelles, based on the H40-poly(?-caprolactone)-b-poly(N-isopropylacrylamide-co-acrylamide)-fluorescein methyl ester/b′-methoxy poly(ethylene glycol)/poly(ethylene glycol)-folate (i.e., H40-PCL-b-P(NIPAAm-co-AAm)-FL/b′-MPEG/PEG-FA (HPPNAP-FA)) with imaging and targeting moieties on the periphery were developed for the tumor-targeted delivery and temperature-induced site-specifically release of hydrophobic anticancer drugs. The amphiphilic HPPNAP-FA copolymer was able to self-assemble into unimolecular micelles in aqueous solution with an average diameter of 65 nm. The lower critical solution temperature (LCST) of micelles was around 39.5 °C. The anticancer drug, paclitaxel (PTX), was encapsulated into the multifunctional micelles. In vitro release studies demonstrated that the drug-loaded delivery system is relatively stable at physiologic conditions but susceptible to mild acidic environments and temperatures above LCST which would trigger the release of encapsulated drugs. Both flow cytometry and fluorescent microscopy showed that the cellular uptake of the PTX-loaded HPPNAP-FA micelles is higher than that of the PTX-loaded HPPNAP because of the folate receptor mediated endocytosis. The efficacy of this thermoresponsive drug delivery system was also evaluated at temperatures above the LCST (40 °C); the results demonstrated that the cellular uptake and the cytotoxicity of PTX-loaded micelles increase prominently. These results indicate that these multifunctional and thermoresponsive unimolecular micelles are promising biomaterials to improve the delivery efficiency and cancer specificity of hydrophobic chemotherapeutic drugs.     

Dual-sensitive and folate-conjugated mixed polymeric micelles for controlled and targeted drug delivery

For this study, we prepared a new type of drug carrier with the characteristics of stimuli-responsive transition and tumor-specific recognition through the co-assembly of two series of amphiphilic block copolymers, poly(ε-caprolactone)-b-poly[triethylene glycol methacrylate-co-N-methacryloyl caproic acid] and poly(ε-caprolactone)-b-poly[triethylene glycol methacrylate-co-N-(2-(methacrylamido)ethyl) folatic amide]. The pH-dependent thermal transition and the content of the targeting ligands of the mixed polymeric micelles are well correlated with the chemical structures and compositions of these two copolymers. Doxorubicin-loaded mixed polymeric micelles are stable at body temperature in the neutral condition for prolonged circulation in blood vessels, and demonstrated rapid drug release at acidic pH levels. The cumulative drug release profiles showed a relatively slow release at pH 7.4, and a quick release of 85% in 3 h at pH 5.3. The cytotoxicity tests against FA-positive (HeLa) and FA-negative (HT-29) tumor cell lines suggest that this mixed polymeric micelle system has potential merits as a controlled and targeted drug delivery system.     

Amphiphilic chitosan graft copolymer via combination of ROP, ATRP and click chemistry: Synthesis, self-assembly, thermosensitivity, fluorescence, and controlled drug release

Novel amphiphilic chitosan-g-poly(ε-caprolactone)-(g-poly(2-(2-methoxyethoxy)ethyl methacrylate)-co-oligo(ethylene glycol) methacrylate) (CS-g-PCL(-g-P(MEO₂MA-co-OEGMA))) copolymers with double side chains of PCL and P(MEO₂MA-co-OEGMA) were synthesized via combination of ring-opening polymerization (ROP), atom transfer radical polymerization (ATRP) and click chemistry. The molar ratio of PCL and P(MEO₂MA-co-OEGMA) was varied through variation of the feed ratio and the coupling efficiency of click chemistry is comparatively high. The graft copolymers can assemble into spherical micelles. The micelles show thermosensitive properties and the lower critical solution temperatures (LCSTs) were influenced by CS chains and the ratio of PCL and P(MEO₂MA-co-OEGMA) side chains. Moreover, the micelles can reversibly swell and shrink in response to the change of temperatures. Furthermore, the micelles present obvious fluorescence and the fluorescent intensity can be adjusted by altering the temperatures. The investigation of doxorubicin release from the micelles indicated that the release rate of the drug could be effectively controlled by altering the temperatures.     

Synthesis and self-assembly of a new amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) block copolymer

New amphiphilic thermosensitive poly(N-vinylcaprolactam)/poly(ε-caprolactone) (PNVCL-b-PCL) block copolymers were synthesized by ring-opening polymerization of ε-caprolactone with hydroxy-terminated poly(N-vinylcaprolactam) (PNVCL-OH) as a macroinitiator. The structures of the polymers were confirmed by IR, ¹H NMR and GPC. The critical micelle concentrations of copolymer in aqueous solution measured by the fluorescence probe technique reduced with the increasing of the proportion of hydrophobic parts, so did the diameter and distribution of the micelles determined by dynamic light scattering. The shape observed by transmission electron microscopy (TEM) demonstrated that the micelles are spherical. On the other hand, the UV–vis measurement showed that polymers exhibit a reproducible temperature-responsive behavior with a lower critical solution temperature (LCST). The LCST of PNVCL-OH can be adjusted by controlling the molecular weights, and that of copolymers can be adjusted by controlling the compositions and the concentration. Variable temperature TEM measurements demonstrated that LCST transition was the result of transition of individual micelles to larger aggregates.     

PCEC hydrogel used on sustained‐release hyaluronic acid delivery with lubrication effect

Injection of bionic synovial fluid (BSF) is a conventional method to improve the lubricity of artificial joints, but BSF cannot maintain long due to the dilution and degradation of BSF in human body. To prolong the effectiveness of hyaluronic acid (HA), which is the major component of BSF, this study applies a temperature‐sensitive poly(?‐caprolactone)–poly(ethylene glycol)–poly(?‐caprolactone) (PCEC) hydrogel loaded with HA to achieve long‐term lubrication. In addition, Fourier transform infrared, nuclear magnetic resonance analysis, X‐ray diffraction, scanning electron microscopy (SEM), and gel permeation chromatography spectra were used to analyze the structure of the synthetic hydrogel. Rheological test and test tube inverting method were used to characterize the thermosensitivity. The lubrication properties of the released solution were characterized by UV–vis, tribological tests, SEM, and 3D laser confocal scanning microscope. The experimental results reveal that the triblock PCEC hydrogel contains both hydrophilic block and hydrophobic block, and both PCEC and PCEC/HA hydrogels have phase‐changed effect when the temperature increases from room temperature to body temperature. Moreover, the friction coefficient of the released solution from PCEC/HA hydrogel is approximatively 38% lower than that of phosphate buffer saline. And the ability of shear resistance and creep recovery of PCEC/HA hydrogel are better than that of PCEC hydrogel. This study provides an effective approach to achieve long‐time lubrication effect for artificial joints. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46228.     

pH响应型mPEG-PCL嵌段共聚物胶束用作药物运输

该文合成了一种具有pH敏感性,较低毒性的两亲性嵌段共聚物以用于药物运输。聚乙二醇-聚己内酯(mPEG-PCL)是以聚乙二醇单甲醚为引发剂,开环己内酯聚合而成,阿霉素则是通过顺乌头酸裂解键连在聚己内酯的末端。该嵌段聚合物通过核磁共振、红外光谱等进行表征。共轭阿霉素后的嵌段聚合物在水溶液中能够自组装形成胶束,胶束粒径约为45.4 nm,透射电镜显示胶束具有近似的球形结构。阿霉素在pH=4.0下的释放速率明显快于pH=7.4下的释放速率。mPEG-PCL在细胞培养中无细胞毒性,包载阿霉素的胶束在人类MCF-7乳腺癌细胞上表现出迟缓的细胞毒性。通过共聚焦显微镜观察游离阿霉素和mPEG-PCL-DOX胶束在MCF-7细胞内的定位说明载体能够携带阿霉素进入细胞。     

Amino acid functionalized pH- and temperature-sensitive biodegradable injectable hydrogels: synthesis,physicochemical characterization and in vivo degradation kinetics

Abstract

In recent years, injectable hydrogels that undergo sol-to-gel phase transition in response to the physiological pH- and temperature have attracted increasing attention in therapeutics delivery. In this study, we developed a biodegradable pH- and temperature-sensitive pentablock copolymers by chemical conjugation of L-cysteine oligomer to the backbone of poly(ε-caprolactone-co-lactide)-b-poly(ethylene glycol)-b-poly(ε-caprolactone-co-lactide) (PCLA-PEG-PCLA) copolymers. A series of pentablock copolymers with various chain lengths were prepared by tuning the reaction time and temperature. These copolymers were freely soluble in water at high pH and low temperature; whereas, they could form a stable gel at the physiological condition (pH 7.4, 37?°C). An in vivo injectable study in the back of Sprague-Dawley (SD) rats indicated that the copolymer could form an in situ gel. In addition, an in vivo biodegradation study of the hydrogels showed controlled degradation of the gel matrix without inflammation at the injection site. Overall, our results show that biodegradable pH- and temperature-responsive hydrogel prepared in this study found to be bioresorbable and could be used as a controlled therapeutics delivery vehicle.     

Preparation of Electrospun Electroactive Nanofibers of Four Arm Star-Shaped Poly(ε-Caprolactone)-b-Poly(2-Hydroxyethyl Methacrylate) and Its Blends with Polyaniline

A combination of ring-opening polymerization and atom-transfer radical polymerization was used to synthesize a four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate). The structure of obtained copolymer was determined by Fourier transform infrared, ¹H and ¹³C NMR spectroscopies. The uniform electroactive nanofibers consisting blend of four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) copolymer and polyaniline were produced using electrospinning technique. The electroactivity of prepared nanofibers was investigated using cyclic voltammetry measurement. The morphologies of electrospun nanofibers produced from four-arm star-shaped poly(ε-caprolactone)-b-poly(2-hydroxyethyl methacrylate) and their blends with polyaniline were investigated by the scanning electron microscopy. The presence of polyaniline resulted in significant decrease of sticking fibers.     

Diblock and triblock copolymers catalyzed by benzo-12-crown-4 bridged N-heterocyclic carbene: synthesis,characterization and degradation behavior

The sequential ring-opening polymerizations (ROP) of ε-caprolactone (ε-CL) and L-lactide (LLA) with benzo-12-crown-4-imidazole carbene (B-12-C-4imY) as the catalyst have been performed. Using either benzyl alcohol or ethylene glycol as an initiator, the corresponding poly(ε-caprolactone)-poly(L-lactide) (PCL-b-PLLA) diblock or poly(L-lactide)-poly(ε-caprolactone)-poly(L-lactide) (PLLA-PCL-PLLA) triblock copolymers were easily prepared. The results indicated that B-12-C-4imY was quite effective for the copolymerization. The diblock copolymerization of ε-CL with LLA could only be achieved when ε-CL was first polymerized followed by LLA. Feeding the two monomers simultaneously, however, only resulted in the formation of LLA homopolymers. Thermogravimetric analysis (TGA) measurements demonstrated that block copolymers exhibited the decomposition temperature lower than the PCL homopolymer. The copolymers were characterized by ¹H NMR and ¹³C NMR, FT-IR, GPC, and DSC analyses. 20?×?10 mm² rectangular specimens made of the triblock copolymer were allowed to degrade in a pH?=?7.4 phosphate buffer at 37 °C. Degradation was monitored by various analytical techniques such as GPC, IR, and ESEM.     

Synthesis of novel temperature responsive PEG-b-[PCL-g-P(MEO2MA-co-OEGMA)]-b-PEG (tBG) triblock-graft copolymers and preparation of tBG/graphene oxide composite hydrogels via click chemistry

Novel triblock-graft copolymers, poly ethylene glycol-b-[poly(ε-caprolactone)-g-poly(2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate)]-b-poly ethylene glycol (PEG-b-[PCL-g-P(MEO₂MA-co-OEGMA)]-b-PEG) (tBG), were synthesized via ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). In the synthesis process, temperature responsive P(MEO₂MA-co-OEGMA) chains were grafted onto the PCL block of triblock copolymer PEG-b-PCL-b-PEG to improve its hydrophilicity. This method succeeded in increasing the solubility of PEG-b-PCL-b-PEG in water, and more importantly, endowing PEG-b-PCL-b-PEG with temperature sensitivity. By adjusting the feed ratio of 2-(2-methoxy ethoxy) ethyl methacrylate (MEO₂MA) and oligo (ethylene glycol) methacrylate (OEGMA) monomers, the lower critical solution temperature (LCST) of the tBG can be realized at about 37 °C. Taking advantage of the excellent mechanical property of graphene sheets, alkyne-functionalized graphene oxide (alkyne-GO) was introduced to cross-link tBGs and prepare tBG/GO composite hydrogel through click reaction between tBG-N₃ and alkyne-GO. Different from traditional cross-linkers, alkyne-GO acts as reinforcing filler in the composite hydrogel. Benefiting from superior properties of PCL, PEG, P(MEO₂MA-co-OEGMA) and GO, the as-prepared temperature responsive tBG/GO hydrogel exhibits excellent mechanical strength and toughness, demonstrating future potential applications in tissue engineering and biotechnology fields.     

Biodegradable polyester blends for biomedical application

A new family of bioabsorbable materials suitable for biomedical applications was designed and prepared by means of blending of some available polyesters to develop new biodegradable materials tailored for different requirements. Multiphase polymer blends containing poly(d, l-lactide) (PLA), poly(ε-caprolactone) (PCL), poly(d, l)-lactide-co-poly(ethylene glycol) (PELA), poly(ε-caprolactone) -co-poly(ethylene glycol) (PECL), and poly(ß-hydroxybutyrate) (PHB), PLA/PCL, PELA/PECL, PHB/PLA, PHB/PELA, PHB/PCL, and PHB/PECL blends were respectively investigated. It was found that PLA/PCL, PHB, and PHB/PLA and PHB/PCL blends were seemingly immiscible, with their morphology and hydrolytic behavior were determined by the composition of the blends. On the other hand, the miscibility of PELA/PECL, PHB/PELA, and PHB/PECL blends was improved by using PELA and/or PECL block copolymers that contained poly(ethylene glycol) (PEG) as compatibilizer. The blends showed to a certain extent miscibility, fine phase morphology, and fast hydrolysis. © 1995 John Wiley & Sons, Inc.     

Synthesis, characterization, and drug delivery research of an amphiphilic biodegradable star-shaped block copolymer

An amphiphilic biodegradable three-arm star-shaped diblock copolymer containing poly(ε-caprolactone) (PCL) and poly(N-vinylpyrrolidone) (PVP) (TEA(PCL-b-PVP)₃) has been successfully synthesized by the ring-opening polymerization of ε-caprolactone (ε-CL), RAFT polymerization of N-vinylpyrrolidone and a coupling reaction of PCL with carboxyl-terminated PVP (PVP-COOH). In aqueous media, the star-shaped copolymer self-assembled into spherical micelles with diameters of near 106 nm. The critical micelle concentration of TEA(PCL-b-PVP)₃ copolymer was determined to be 5.96 × 10^?3 mg/mL. Folic acid was then used as a model drug to incorporate into TEA(PCL-b-PVP)₃ micelles, the drug loading content and encapsulation efficiency is 16.36 and 49.08 %, respectively. In vitro release experiments of the drug-loaded micelles exhibited sustained release behavior and it was affected by the pH of release media. These results indicate that the copolymer may serve as a promising “intelligent” drug delivery alternative.     

Design and characterization of PNVCL-based nanofibers and evaluation of their potential applications as scaffolds for surface drug delivery of hydrophobic drugs

In this work, nanofiber scaffolds for surface drug delivery applications were obtained by electrospinning poly(N-vinylcaprolactam) (PNVCL) and its blends with poly(ε-caprolactone) and poly(N-vinylcaprolactam)-b-poly(ε-caprolactone). The process parameters to obtain smooth and beadless PNVCL fibers were optimized. The average fibers diameter was less than 1 μm, and it was determined by scanning electron microscopy analyses. Their affinity toward water was evaluated by measuring the contact angle with water. The ketoprofen release behavior from the fibers was analyzed using independent and model-dependent approaches. The low values of the release exponent (n < 0.5) obtained for 20 and 42 °C, indicating a Fickian diffusion mechanism for all formulations. Dissolution efficiencies (DEs) revealed the effect of polymer composition, methodology used in the electrospinning process, and temperature on the release rate of ketoprofen. PNVCL/poly(N-vinylcaprolactam)-b-poly(ε-caprolactone)-based nanofibers showed greater ability to control the in vitro release of ketoprofen, in view of reduced kinetic constant and DE, making this material promising system for controlling release of hydrophobic drugs. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48472.     

pH-responsive amphiphilic H-shaped supramolecular copolymer via the inclusion complexation between β-cyclodextrin and adamantane

pH-responsive amphiphilic H-shaped copolymer was prepared by the supramolecular self-assembly between β-cyclodextrin-graft-poly(2-(N,N-diethylamino)ethyl methacrylate) (β-CD-(PDEAEMA)₂) and bi-adamantyl terminated poly(ε-caprolactone) (Ad-PCL-Ad). β-CD-(PDEAEMA)₂ was synthesized by click reaction of alkynyl-modified β-CD with azide PDEAEMA (PDEAEMA-N₃). Ad-PCL-Ad was synthesized by the DCC reaction of bi-hydroxyl terminated PCL (HO-PCL-OH) with adamantaneacetic acid. The supramolecular copolymer can self-assemble into micelles in water at room temperature. The micellization and pH-responsivity of the amphiphilic copolymer solution were investigated by transmittance, dynamic light scattering spectrophotometer, and transmission electron microscopy in water. Investigation shows that the micelles’ sizes can be adjusted through the alteration of the pH values of solutions and the supramolecular copolymer will have the potential applications in biomedical field.     

Chemochromic properties of neutral polyaniline throughout cholesterol exposure

α-Bromo-ε-caprolactone (α-BrCL) was synthesized from α-bromocyclohexanone by using 3-chloroperoxybenzoic acid. α-BrCL was then used as a comonomer in the ring-opening polymerization of ε-caprolactone (CL) initiated with aluminum isopropoxide to synthesize poly(CL-co-α-BrCL) copolymer. This copolymer was used as the macroinitiator in the atom transfer radical polymerization (ATRP) of N-isopropylacrylamide (NIPAAm) for the synthesis of stimuli-responsive and biodegradable PCL-g-PNIPAAm copolymer. A core-shell type nano-structure was formed with a hydrophilic outer shell and a hydrophobic inner core from these copolymers, which exhibited a phase transition temperature around 31 °C. The copolymers were characterized by ¹H-NMR and FT-IR spectroscopies. Number-average molecular weight of the poly(CL-co-α-BrCL) and PCL-g-PNIPAAm copolymers was calculated from corresponding ¹H-NMR spectra to be 5770 and 6810 gmol^?1, respectively. Thermal stability of the copolymer was investigated by thermogravimetric analysis (TGA) and crystallization behavior was studied by differential scanning calorimetry (DSC). Transmission electron microscopy (TEM) showed that the self-assemble micelle aggregates had well defined spherical shape. From the fluorescence spectra, fluorescence intensity of pyrene in the copolymer micelles increased and red-shifted as the copolymer concentration increases, indicating the formation of self-assemble polymeric micelles in water. The critical micelle concentration was found to be 3.2?×?10^?3?mg/mL. TEM results showed that micelles have spherical shapes with a diameter of about 70 nm. The obtained micelles can be desirable for potential applications in biomedical fields, such as drug delivery systems.