Blow-spun chitosan/PEG/PLGA nanofibers as a novel tissue engineering scaffold with antibacterial properties

Blow spinning is continuing to gain attention in tissue engineering, as the resultant nanofibrous structures can be used to create a biomimetic environment. In this study, blow spinning was used to construct nanofiber scaffolds with up to 10?% chitosan and poly(DL-lactide-co-glycolide) in the absence or presence of poly(ethylene glycol). Scanning electron microscopy demonstrated that nanofibers were distributed randomly to form three-dimensional mats. With respect to chitosan concentration, the average fiber diameter did not differ statistically in either the absence or presence of poly(ethylene glycol). In poly(ethylene glycol)-formulations, the average fiber diameter ranged from (981.9?±?611.3) nm to (1139.2?±?814.2) nm. In vitro cellular metabolic activity and proliferation studies using keratinized rat squamous epithelial cells (RL-65) showed that cytocompatibility was not compromised with the addition of poly(ethylene glycol). The cell responses at lower (1 and 2.5?%) chitosan concentrations were not significantly different from the groups without chitosan or no scaffold when cultivated for 3, 6, or 9 days. However, >15?% reduction in cellular responses were observed at 10?% chitosan. In presence of poly(ethylene glycol), nearly a 1-log incremental reduction in the number of colony forming units of Streptococcus mutans occurred as the chitosan concentration increased from 0–1 to 2.5?%. Bacterial preparations tested with poly(ethylene glycol) and 5 or 10?% chitosan were not significantly different than the positive kill control. Taken together, the most favorable conditions for attaining cytocompatibility and maintaining antibacterial functionality existed in poly(ethylene glycol)/poly(DL-lactide-co-glycolide) blow-spun scaffolds with integrated 1 or 2.5?% chitosan.     

Photo-Induced Cytotoxicity of Water-Soluble Fullerene

Abstract

The reaction of C₆₀ with poly(ethylene glycol) having a terminal primary amino group or a mixture of ethylene diamine and poly(ethylene glycol) having terminal carboxyl groups resulted in formation of water-soluble C₆₀ conjugates. These conjugates showed strong cytotoxicity to L929 cells upon visible light irradiation as a result of superoxide production.     

Electrokinetic behaviour and dispersion characteristics of ceramic powders with cationic and anionic polyelectrolytes

Three different ceramic powders, viz. alumina, zirconia and silicon nitride were dispersed using two polyelectrolytes, one cationic (Betz 1190) and the other anionic (Darvan-C). All powders examined during the study could be well dispersed only under conditions of polymer dosage and pH such that the working pH is at least 2 pH units away from the pH_IEP of the powder-dispersant combination. The shift in the isoelectric point (IEP) of the powders were determined through electro-acoustic measurements on 1% volume suspensions. Specific free energy of interaction were also computed using a model based on the electrical double layer theory of surfactant absorption. Certain trade names and company products are mentioned in the text or identified in illustrations in order to adequately specify the experimental procedure and equipment used. In no case does such identification imply recommendation or endorsement by the authors and their respective institutes nor does it imply that the products are necessarily the best available for the purpose.     

Deoxycholic acid-grafted PEGylated chitosan micelles for the delivery of mitomycin C

Mitomycin C (MTC) was incorporated to a micelle system preparing from a polymer named deoxycholic acid chitosan-grafted poly(ethylene glycol) methyl ether (mPEG-CS-DA). mPEG-CS-DA was synthesized and characterized by ¹H nuclear magnetic resonance (¹H-NMR) and Fourier transform infrared spectroscopy. mPEG-CS-DA formed a core-shell micellar structure with a critical micelle concentration of 6.57?µg/mL. The mPEG-CS-DA micelles were spherical with a hydrodynamic diameter of about 231?nm. After poly(ethylene glycol)ylation of deoxycholic acid chitosan (CS-DA), the encapsulation efficiency and drug loading efficiency increased from 50.62% to 56.42% and from 20.51% to 24.13%, respectively. The mPEG-CS-DA micelles possessed a higher drug release rate than the CS-DA micelles. For pharmacokinetics, the area under the curve (AUC) of the mPEG-CS-DA micelles was 1.5 times higher than that of MTC injection, and these micelles can enhance the bioavailability of MTC. mPEG-CS-DA micelles reduced the distribution of MTC in almost all normal tissues and had the potential to improve the kidney toxicity caused by MTC injection.     

Stereocomplex block copolymer micelles: core-shell nanostructures with enhanced stability

Monodisperse stereocomplex block copolymer micelles were obtained through the self-assembly of equimolar mixtures of poly(ethylene glycol)-block-poly(l-lactide) and poly(ethylene glycol)-block-poly(d-lactide) in water. These micelles possessed partially crystallized cores and mean hydrodynamic diameters ranging from 31 to 56 nm, depending on the lactide content. They exhibited kinetic stability and redispersion properties superior to micelles prepared with isotactic or racemic polymers alone. This study demonstrates the advantages of stereocomplex formation in the design of stabilized water-soluble nanoparticles.     

Stabilizer architectures based on fluorinated random and block copolymers for the dispersion polymerization of 2-hydroxyethyl methacrylate in supercritical carbon dioxide

Different types of stabilizers architectures based on copolymers composed of hydrophilic components and CO₂-philic fluorinated acrylate groups were investigated for the free radical dispersion polymerization of 2-hydroxyethyl methacrylate (HEMA) at 65 °C in supercritical carbon dioxide (scCO₂). Four categories of random and block copolymeric stabilizers consisting of 1H,1H,2H,2H-perfluorooctyl methacrylate (FOMA), oligo(ethylene glycol) methacrylate (OEGMA), dimethyl amino ethyl methacrylate (DMAEMA), and ethylene oxide (EO) were selected as stabilizers for HEMA. The effect of the stabilizer architecture on the polymerization results was investigated in terms of stabilizer concentration, the nature of the hydrophilic anchor groups, and block versus random copolymers. White free-flowing poly(HEMA) powders in high yield were obtained with all stabilizers. While the monomer conversion was independent, the morphology of particles was found to be considerably affected by the nature of the stabilizers.     

Electrospun PELCL membranes loaded with QK peptide for enhancement of vascular endothelial cell growth

One of the major challenges in tissue engineering of small-diameter vascular grafts is to inhibit intimal hyperplasia and keep long-term patency after implantation. Rapid endothelialization of the grafts could be an effective approach. In this study, QK, a peptide mimicking vascular endothelial growth factor, was selected as the bioactive substrate and loaded in electrospun membranes for enhancement of vascular endothelial cell growth. In detail, QK peptide was firstly introduced with poly(ethylene glycol) diacrylate into a thiolated chitosan solution that could transfer into hydrogel. Then, suspensions or emulsions of poly(ethylene glycol)-b-poly(l-lactide-co-ε-caprolactone) (PELCL) containing QK peptide (with or without chitosan hydrogel) were electrospun into fibrous membranes. For comparison, the electrospun PELCL membrane without QK was also fabricated. Results of release behaviors showed that the electrospun membranes, especially that contained chitosan hydrogel prepared by suspension electrospinning, could successfully encapsulate QK peptide and maintain its secondary structure after released. In vitro cell culture studies exhibited that the release of QK peptide could accelerate the proliferation of vascular endothelial cells in the 9 days. It was suggested that the electrospun PELCL membranes loaded with QK peptide might have potential applications in vascular tissue engineering.     

ROS‐Sensitive Degradable PEG–PCL–PEG Micellar Thermogel

A reactive oxygen species (ROS)‐sensitive degradable polymer would be a promising material in designing a disease‐responsive system or accelerating degradation of polymers with slow hydrolysis kinetics. Here, a thermogelling poly(ethylene glycol)–polycaprolactone–poly(ethylene glycol) (PEG–PCL–PEG or EG₁₂–CL₂₀–EG₁₂) triblock copolymer with an oxalate group at the middle of the polymer is reported. The polymers form micelles with an average size of 100 nm in water. Thermogelation is observed in a concentration range of 8.0?37.0 wt%. In particular, the aqueous PEG–PCL–PEG triblock copolymer solutions are in a gel state at 37 °C in a concentration range of 25.0–37.0 wt%, whereas the aqueous PEG–PCL diblock copolymer solutions are in a sol state in the same concentration range at 37 °C. Thus, the gel depot could dissolve out once degradation of the triblock copolymers occurs at the oxalate group as confirmed by the in vitro experiment. In vivo gel formation is confirmed by injecting an aqueous PEG–PCL–PEG solution (36.0 wt%) into the subcutaneous layer of rats. The gel completely disappears in 21 d. A model polypeptide drug (cyclosporine A) is released over 21 d from the in situ formed gel. The micelle‐based thermogel of PEG–PCL–PEG with ROS‐triggering degradability is a promising injectable material for biomedical applications.     

Micellar carrier based on methoxy poly(ethylene glycol)-block-poly(<Emphasis Type="Italic">ε</Emphasis>-caprolactone) block copolymers bearing ketone groups on the polyester block for doxorubicin delivery

Block copolymers of Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) bearing ketone groups (MPEG-b-P(CL-co-OPD)) are synthesized and evaluated for its potential to form micelles containing doxorubicin (DOX), a representative anticancer drug, by using an in vitro method based on membrane dialysis to emulate drug release in vivo. The ¹H NMR spectra of the prepared block copolymers in D₂O solution exhibit peaks due to the P(OPD-co-CL) in decreased intensity, indicates that the polymers form micelle particles containing the hydrophilic segments in their external parts. The CMC of the copolymer decrease with an increase in the content of ketone groups in the hydrophobic chain. Drug-free and drug-loaded solutions of structurally related copolymers indicate the polymeric aggregation into micellar-type constructs. The size of the drug-loaded micelles is found to be larger than corresponding drug-free micelles. The release rate of MPEG-b-PCL micelles is faster than MPEG-b-P(OPD-co-CL) micelles in pH 7.4 buffered solution and they have a similar release rate in pH 5.0 buffered solution. This study, therefore, confirms the potential of a novel functional block copolymers, Methoxy poly(ethylene glycol)-block-poly(ε-caprolactone) bearing ketone Groups, for the formation of polymeric micelles for drug delivery.     

Synthesis,Characterization and Drug Release Behavior of pH‐Responsive O‐carboxymethyl Chitosan‐graft‐poly(N‐vinylpyrrolidone) Hydrogel Beads

In this work, the carboxymethyl chitosan (CMCTS) grafted poly(N‐vinylpyrrolidone) (PVP) copolymers were synthesized. The hydrogel beads containing VB₂ were prepared from the copolymers by an ionic crosslinked. The experimental results shown that VB₂ drug release rate from those beads decreased with the increasing grafting percentage, crosslinker concentration and pH value of the medium. Besides, the beads have the better control ability for releasing of model drug than CMCTS does.     

The morphology and fabrication of nanostructured micelle by a novel block copolymer with linear–dendritic structure

We report here a novel approach to fabricate a nanostructured micelle as potential drug carriers and the relationship between the morphological structure and the preparation condition. The polymeric micelle aggregates constructed by self-assembly compose of the poly(ε-caprolactone)/monomethoxy poly(ethylene glycol) linear–dendritic block copolymers. The corresponding copolymers were synthesized by using ring opening polymerization of ε-caprolactone (CL) and a dendritic poly(ether–amide) (DPEA-OH) as an initiator, then coupling with the isocyanate end-capped linear monomethoxy polyethylene glycol. Fluorescence spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were performed to characterize the copolymer micelles. The critical micelle concentration (CMC) was determined to be 1.623 mg/L. The hydrodynamic radius (R_h) and the polydispersity index (PDI) are influenced by the concentration of the micelle solutions. The multiple morphologies of the micelle aggregates, including spheres, rob-like dendritic structure and vesicles were observed, which the variety depends on the various preparation conditions. The nanostructured micelles based on the linear–dendritic block copolymer possess the strong thermodynamic stability and the power of solubilization of hydrophobic drug molecules.     

Morphology and conductivity studies of a new solid polymer electrolyte: (PEG)<Subscript>x</Subscript>LiClO<Subscript>4</Subscript>

A new solid polymer electrolyte, (PEG)_xLiClO₄, consisting of poly(ethylene)glycol of molecular weight 2000 and LiClO₄ was prepared and characterized using XRD, IR, SEM, DSC, NMR and impedance spectroscopy techniques. XRD and IR results show the formation of the polymer-salt complex. The samples with higher salt concentration are softer, less opaque and less smooth compared to the low salt concentration samples. DSC studies show an increase in the glass transition temperature and a decrease in the degree of crystallinity with increase in the salt concentration. Melting temperature of SPEs is lower than the pure PEG 2000. Room temperature¹H and⁷Li NMR studies were also carried out for the (PEG)_xLiClO₄ system. The¹H linewidth decreases as salt concentration increases in a similar way to the decrease in the crystalline fraction and reaches a minimum at aroundx = 46 and then increases.⁷Li linewidth was found to decrease first and then to slightly increase after reaching a minimum atx = 46 signifying the highest mobility of Li ions for this composition. Room temperature conductivity first increases with salt concentration and reaches a maximum value (σ = 7.3 × 10⁻⁷ S/cm) atx = 46 and subsequently decreases. The temperature dependence of the conductivity can be fitted to the Arrhenius and the VTF equations in different temperature ranges. The ionic conductivity reaches a high value of ∼10 ⁻⁴S/cm close to the melting temperature.     

Synthesis,characterization, biodegradability and biocompatibility of a temperature-sensitive PBLA-PEG-PBLA hydrogel as protein delivery system with low critical gelation concentration

Temperature-sensitive hydrogels were designed using a series of A-B-A triblock copolymers consisting of poly (ethylene glycol) (PEG) with different molecular weights as the hydrophilic block B and poly (β-butyrolactone-co-lactic acid)(PBLA) with varying block lengths and composition as the hydrophobic block A. The triblock copolymers were synthesized by ring-opening polymerization (ROP) of β-BL and LA in bulk using PEG as an initiator and Sn(Oct)₂ as the catalyst. Their chemical structure and molecular characteristics were determined by NMR, GPC and DSC, and the relationship between structure and phase behaviors in aqueous solutions was investigated as well. It was found that the phase behaviors in aqueous solutions including critical micelle concentration (CMC), sol-gel-sedimentation phase transition temperature, gel window width and critical gelation concentration (CGC) are largely dependent on the molecular weight and block length ratio of PEG/PBLA. Most importantly, they show a very low CGC ranging from 4 to 8?wt% because of the introduction of β-BL. Furthermore, the biodegradability and biocompatibility of the hydrogels were evaluated. Finally, lysozyme as a model protein was used to evaluate the ability to deliver protein drugs in a sustained release manner and biologically active form. All results demonstrated that the temperature-sensitive in situ forming hydrogel has a promising potential as sustained delivery system for protein drugs.     

Preparation and characterization of pH sensitive comb-shaped chitosan material for the controlled release of coenzyme A

A novel kind of pH sensitive comb-shaped copolymer P(CS-Ma-PEGMA) was synthesized with chitosan (CS), maleic anhydride (Ma) and Poly (ethylene glycol) methacrylate (PEGMA) by grafting and co-polymerization. The structure of P(CS-Ma-PEGMA) was characterized by FT-IR and ¹H-NMR, and it was found that PEGMA was grafted onto CS and PEGMAylated chitosan was soluble. The copolymer was subjected to coenzyme A adsorption study in order to assess its application in biomedical area. The factors affecting release behavior, such as concentration and pH were discussed in this paper. The higher concentration of the copolymer showed higher absorbance peak than the lower one. The pH of the solution also had significant impact on the release of coenzyme A, and the mechanism of adsorption was suggested. The results suggested that the novel copolymer could be used as drug delivery carrier.     

Effective poly(ethylene glycol) methyl ether grafting technique onto Nylon 6 surface to achieve resistance against pathogenic bacteria <Emphasis Type="Italic">Staphylococcus aureus</Emphasis> and <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis>

Our study is focused on an efficient reduction of amide functional groups to secondary amine on Nylon 6 surface with borane–tetrahydrofuran (BH₃–THF) complex, followed by N-alkylation with benzyl chloride (C₆H₅CH₂Cl) which has been successfully used as a model system for further grafting of the reduced Nylon 6 surface by poly(ethylene glycol) methyl ether tosylate (Me-PEG-OTs). The amine-activated surface has been obtained by treatment of reduced Nylon 6 with n-butyllithium or tert-butyllithium in THF. Modified Nylon 6 has been found to be antibacterial particularly due to the presence of hydrophilic poly(ethylene glycol) methyl ether (H₃C-PEG) chains. The surface modifications were successfully characterized by various techniques. Water contact angle and free surface energy analyses indicated a significant change in the surface morphology. It was further supported by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and Raman spectroscopy. Finally, antibacterial tests were performed against two pathogenic bacterial strains Pseudomonas aeruginosa (CCM 3955) and Staphylococcus aureus (CCM 3953).     

Intelligent anticancer drug delivery performances of two poly(N-isopropylacrylamide)-based magnetite nanohydrogels

This article evaluates the anticancer drug delivery performances of two nanohydrogels composed of poly(N-isopropylacrylamide-co-itaconic anhydride) [P(NIPAAm-co-IA)], poly(ethylene glycol) (PEG), and Fe₃O₄ nanoparticles. For this purpose, the magnetite nanohydrogels (MNHGs) were loaded with doxorubicin hydrochloride (DOX) as a universal anticancer drug. The morphologies and magnetic properties of the DOX-loaded MNHGs were investigated using transmission electron microscopy (TEM) and vibrating–sample magnetometer (VSM), respectively. The sizes and zeta potentials (ξ) of the MNHGs and their corresponding DOX-loaded nanosystems were also investigated. The DOX-loaded MNHGs showed the highest drug release values at condition of 41?°C and pH 5.3. The drug-loaded MNHGs at physiological condition (pH 7.4 and 37?°C) exhibited negligible drug release values. In vitro cytotoxic effects of the DOX-loaded MNHGs were extensively evaluated through the assessing survival rate of HeLa cells using the MTT assay, and there in vitro cellular uptake into the mentioned cell line were examined using fluorescent microscopy and fluorescence-activated cell sorting (FACS) flow cytometry analyses. As the results, the DOX-loaded MNHG1 exhibited higher anticancer drug delivery performance in the terms of cytotoxic effect and in vitro cellular uptake. Thus, the developed MNHG1 can be considered as a promising de novo drug delivery system, in part due to its pH and thermal responsive drug release behavior as well as proper magnetite character toward targeted drug delivery.     

Photo-Induced Cytotoxicity of Water-Soluble Fullerene

The reaction of C₆₀ with poly(ethylene glycol) having a terminal primary amino group or a mixture of ethylene diamine and poly(ethylene glycol) having terminal carboxyl groups resulted in formation of water-soluble C₆₀ conjugates. These conjugates showed strong cytotoxicity to L929 cells upon visible light irradiation as a result of superoxide production.     

Synthesis and properties of a novel methoxy poly(ethylene glycol)-modified galactosylated chitosan derivative

Chitosan and its derivatives are attractive non-viral vectors. To produce target-cell specificity and improve the solubility of chitosan, a novel chitosan derivative, modified with galactose and methoxy poly(ethylene glycol) (mPEG) was synthesized, and structure changes of chitosan and its derivatives were characterized. Compared to chitosan, the solution viscosity of the novel chitosan derivative drastically decreased. And, the degree of substitution (DS) of chitosan by galactose and mPEG were calculated as 0.09 and 0.30. The average diameter and zeta potential of mPEGylated galactosylated chitosan (GaC) nanoparticle containing VRMFat plasmid were 178 nm and +2.93 mV, suggesting suitable properties for gene delivery system. The gel electrophoresis confirmed that the plasmid DNA was remained completely by the mPEGylated GaC nanoparticle. And, the cytotoxic effect of mPEGylated GaC nanoparticles on human embryonic kidney (HEK 293) cells was negligible in comparison with that of control chitosans. Therefore, it is expected that the mPEGylated GaC will have the potential as a targeting gene delivery system for a further application. Tao Zhang and Dong Li equally contributed to this research.     

Construction of glucose and H<Subscript>2</Subscript>O<Subscript>2</Subscript> dual stimuli-responsive polymeric vesicles and their application in controlled drug delivery

Herein, glucose and H₂O₂ stimuli-responsive vesicles are constructed based on host–guest interaction between a diblock copolymer, poly(ethylene glycol)-b-poly[3-acrylamidophenylboronic acid-co-4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)benzyl acrylate], (PEG-b-P(PBA-co-PBEM), BCP for short) and α-cyclodextrin. In the presence of glucose, the vesicles are transformed to giant swollen spherical micelles because of the formation of a negatively charged tetravalent form between phenylboronic acid and glucose. On the other hand, the vesicles are totally disassembled when they are exposed to H₂O₂, which is due to the H₂O₂-mediated degradation of the pendant phenylboronic acid pinacol ester. The glucose and H₂O₂ stimuli-responsive vesicles are then applied in the controlled release of water-soluble anticancer drug, doxorubicin hydrochloride (DOX). Upon external stimuli, the DOX displays a faster release rate than that without stimuli. Moreover, the polymeric vesicles show an excellent cytocompatibility toward MCF-7 cells, and the drug-loaded vesicles exhibit a lower cytotoxicity than free drug toward cancer cells. The drug-loaded vesicles can be taken up by MCF-7 cells and further release the DOX in cancer cells due to the high glucose and H₂O₂ concentration in tumor cells, while they have negligible effect on normal cells, which may be important for applications in the therapy of cancers as a controlled-release drug carrier.