Graft Copolymers Of Poly Research Articles

Polyester-Polydopamine Copolymers for Intravitreal Drug Delivery: Role of Polydopamine Drug-Binding Properties in Extending Drug Release.

This work reports on a novel polyester copolymer containing poly(dopamine), a synthetic analogue of natural melanin, evaluated in a sustained-release drug delivery system for ocular intravitreal administration of drugs. More specifically, a graft copolymer of poly(ε-caprolactone)-graft-poly(dopamine) (PCL-g-PDA) has been synthesized and was shown to further extend the drug release benefits of state-of-the-art biodegradable intravitreal implants composed of poly(lactide) and poly(lactide-co-glycolide). The innovative biomaterial combines the documented drug-binding properties of melanin naturally present in the eye, with the established ocular tolerability and biodegradation of polyester implants. The PCL-g-PDA copolymer was obtained by a two-step modification of PCL with a final PDA content of around 2-3 wt % and was fully characterized by size exclusion chromatography, NMR, and diffusion ordered NMR spectroscopy. The thermoplastic nature of PCL-g-PDA allowed its simple processing by hot-melt compression molding to prepare small implants. The properties of unmodified PCL and PCL-g-PDA implants were studied and compared in terms of thermal properties (differential scanning calorimetry), thermal stability (thermogravimetry analysis), degradability, and in vitro cytotoxicity. PCL and PCL-g-PDA implants exhibited similar degradation properties in vitro and were both stable under physiological conditions over 110 days. Likewise, both materials were non-cytotoxic toward L929 and ARPE-19 cells. The drug loading and in vitro release properties of the new materials were investigated with dexamethasone (DEX) and ciprofloxacin hydrochloride (CIP) as representative drugs featuring low and high melanin-binding affinities, respectively. In comparison to unmodified PCL, PCL-g-PDA implants showed a significant extension of drug release, most likely because of specific drug-catechol interaction with the PDA moieties of the copolymer. The present study confirms the advantages of designing PDA-containing polyesters as a class of biodegradable and biocompatible thermoplastics that can modulate and remarkably extend the drug release kinetics thanks to their unique drug-binding properties, especially, but not limited to, for ocular applications.

Sustainable Modification of Polyethersulfone Membrane with Poly(Maleic Anhydride-Co-Glycerol) as Novel Copolymer

This work presented an endeavour to fabricate sustainable and eco-friendly polyethersulfone (PES) ultrafiltration membranes. A novel and graft copolymer (Poly(Maleic Anhydride-Co-Glycerol)) (PMG) have been synthesized via a facile and rapid route to impart their hydrophilic features onto the final PES membrane. A series of characterization tools, for both nanoadditives and nanocomposite membranes, have been harnessed to confirm their successful fabrication processes. These include Fourier Transform Infrared Spectroscopy (FT-IR), scanning electron microscopy (SEM), Atomic Force Microscopy (AFM), and contact angle measurements (CA). Results disclosed the successful synthesis of PMG nanoparticles that manifested a smooth homogenous surface with an average molecular size of 88.07 nm. The nanocomposite membrane structure has witnessed a gradual development upon each increment in the nanoparticle content ratio along with relatively thicker pore walls. The size and shape of figure-like micropores exhibited critical visible structural changes following the nanoadditive incorporation into the PES polymeric matrix. For the nanocomposite membrane, the SEM imaging indicated that a thicker active layer and less finger-like micropores were formed at higher PMG NP content within the membrane matrix. Hydrophilicity measurements disclosed a reversible correlation with the NP content where the CA angle value was at a minimum at the higher PMG loading content. Compared to the pristine membrane, a considerable enhancement in the performance of the modified membranes was witnessed. The membrane prepared using 2.5 g PMGNPs showcased six times higher pure water flux than neat PES membrane and maintained the highest retention (98%) against BSA protein solution. Additionally, the nanocomposite revealed promising antifouling and self-cleaning characteristics.

FORMATION OF NICKEL NANOPARTICLES IN SOLUTIONS OF A HYDROPHILIC GRAFT COPOLYMER

A graft copolymer of poly(vinyl alcohol) and polyacrylamide (PVA-g-PAAm) with interacting main and grafted chains was synthesized by radical matrix polymerization of PAAm from the PVA backbone in an aqueous medium. Its basic molecular parameters including the number and length (molecular weight) of grafts were determined using elemental analysis, DTGA and viscometry. The copolymer macromolecules formed special monomolecular micelles of elipsoidal shape and length ~18-64 nm in aqueous solutions due to the formation of intramolecular polycomplexes between the main and grafted chains. This copolymer was used as a hydrophilic matrix for the in situ synthesis of nickel nanoparticles (NiNPs) in aqueous solutions.On the basis of UV-Vis spectroscopy, an original and simple method for monitoring the kinetics of the formation and yield of metal nanoparticles in systems in which a surface plasmon resonance band does not appear has been proposed and implemented. Using this approach, the kinetics of borohydride reduction of Ni-salt to NiNPs in pure water and PVA-g-PAAm solutions was studied depending on the concentrations of Ni-salt and copolymer matrices. An increase in the initial rate of accumulation and yield of NiNPs with an increase in the concentration of Ni-salt and a decrease in both parameters in copolymer solutions in comparison with pure water was established. At the same time, the accumulation rate and NiNP yield in a complex way was depended on the matrix concentration that was determined by the ratio of such factors as a decrease in the diffusion rate of NaBH4 molecules in copolymer solutions and the accumulation of Ni2+-ions in matrix particles due to complexation with active chemical groups at the first stage of reduction process. The morphology and main structural elements of the NiNPs/PVA-g-PAAm composition were revealed using TEM. It was shown that the in situ synthesis of NiNPs in copolymer matrices was accompanied by the “detachment” of PAAm grafts from the main PVA chains and led to the appearance of two new structures, such as “hairy coils” and “hairy rods”, containing small spherical NiNPs (d~0,5–12,0 nm) in isolated and chain states, respectively. The appearance of the latter structures was explained by the formation of coordination complexes of Ni2+-ions with active groups of both PVA and PAAm chains at the first stage of the reduction reaction.

Polar poly(n-butyl acrylate)-g-polyacrylonitrile elastomer with high temperature elasticity and healability as flexible electronic substrate

In this work, graft copolymer poly (n-butyl acrylate)-g-polyacrylonitrile with poly (n-butyl acrylate) as backbones and polyacrylonitrile as side chains (PnBA-g-PAN) was synthesized by macromonomer method and emulsion polymerization. The macromonomer was synthesized by atom transfer radical polymerization and end-group modification. The chemical structures and thermal properties of macromonomer and graft copolymer were investigated by FTIR, GPC, NMR and TGA, etc. The mechanical properties of graft copolymer elastomer was also measured by uniaxial tensile test. Rheological properties at different temperature and mechanical property demonstrated that graft copolymer elastomer possessed elasticity until 180 oC because of cyclization of cyano groups. Ag nanowires@PnBA-g-PAN composite elastomer was developed, and the resulted material exhibited autonomic healing property on account of segments’ flexibility and dynamic interaction between Ag nanowires (AgNWs) and cyano groups. This is a general method for generation of elastomer with high temperature elasticity and fast self-healing. The composite elastomer has potential application in flexible electronic conductor.

Effective Removal of Methylene Blue Dye Using Silver Nanoparticles Containing Grafted Polymer of Guar Gum/Acrylic Acid as Novel Adsorbent

In the present work, the synthesis of novel nanocomposite adsorbent based on graft copolymer of Poly(AA)/GG incorporated silver nanoparticles (AgNPs) has been carried out for the elimination of Methylene blue (MB) dye from the aqueous phase. The characterization of synthesized nanocomposite has been carried out by using various analytical techniques such as UV–Vis, FTIR, XRD, FE-SEM, EDX, DLS and BET studies. The UV–Vis, DLS and XRD studies revealed the stable formation of AgNPs inside the polymer matrix with an average size of 100 ± 1 nm. The − 26.40 mV value of Zeta potential also confirms the stability of AgNPs inside the polymer matrix. Furthermore, the resultant adsorbent with an improved adsorption capacity is used to eliminate the MB dye from liquid phase. The parameters such as adsorbent dose and pH of dye solution in adsorption process are optimized. Moreover, the study of the adsorption kinetics and isotherm indicate that the pseudo-second-order kinetics and Langmuir isotherm model is more suitable for describing the experimental adsorption data having maximum adsorption capacity of 833.33 mg/g. Further, the positive values of enthalpy and entropy change specify that the adsorption of MB dye onto the surface of AgNPs/GG/Poly(AA) is endothermic, spontaneous and favorable process. Hence, In-situ synthesis of AgNPs inside polymer and grafting of AA as monomer onto GG has proven to be accountable for the substantial changes in adsorption capacity for removal of MB dye from aqueous phase. Therefore, the resultant AgNPs/GG/Poly(AA) nanocomposite may prove to be a noble adsorbent for the removal of MB dye from the liquid phase.

Chitosan-g-poly (acrylonitrile-co-acrylic acid) for wastewater treatment application

Chitosan is a biodegradable natural based polymer obtained from chitin (N-deacetylated derivative), the second most abundant polysaccharide after cellulose and soluble in most organic acids. Graft copolymerization of poly (acrylonitrile-co-acrylic acid) onto chitosan has been successfully carried out using potassium persulfate as an initiator in an aqueous medium. The PAN and PAA homopolymer formed during the reaction were removed from the Chitosan grafted copolymer by Soxhlet extraction using ethanol as the solvent. The prepared graft copolymerization was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) to confirm the formation of the copolymer. The prepared chitosan-g-copolymer at ratio 25:75% of AN-co-AA was treated with metal solutions containing cadmium ions, times and pH at room temperature. It[Am1] was found that the optimum condition was pH=5, Time 120min and dose of adsorbent 3 mg /L. The results revealed that the chitosan-g-copolymer prepared was excellent in removing the heavy metals than the copolymer alone. Hence, chitosan-g- poly- AN-co-AA could open the way for wastewater treatment. The thermal stability and the electrical conductivity for all prepared samples before and after grafing were measured. By studying the thermal stability at the different ratio of AN and AA in samples co1, co2, co3, it was found that the most thermal stability sample ratio is co3 due to increasing the ratio of AN. While in sample co1 with a high ratio of AA, the thermal stability decrease according to the fast decomposition of –COOH of acrylic acid. The conductivity was 3.85x10-7 which is more than the copolymer without chitosan, which increases the electron density of the copolymer through the end group effect. As the result of σ has a range 10-8 S/cm-1 10-6 S/cm-1so, all the prepared sample can be used as an electrostatic dissipation application.

Poly(alkyl/arylphosphazene)-Metal Nanoparticle Composites

Nanoparticles of gold were prepared by reduction of Au(III) with a reducing agent in the presence of poly(methylphenylphosphazene), [Me(Ph)PN]n, (PMPP), an alcohol derivative (PMPP-OH), a graft copolymer poly(methylphenylphosphazene)-graft-polystyrene, PMPP-g-PS, and a blend of the two graft components. The process involved no phase transfer reagents because the polymers successfully moved the salts from the aqueous to the organic phase. The metal nanoparticles were characterized by UV–Visible spectroscopy and transmission electron microscopy (TEM). When stabilized by these phosphazene polymers, the average size of gold nanoparticles was between 3 and 5 nm. The PMPP-OH nanocomposites were stable in toluene at room temperature for several days, and showed no change on heating in the absence of solvent at 100 °C. In the graft copolymer and the blend, TEM imaging shows that the nanoparticles of gold were located exclusively in the phosphazene domains. An improved synthesis of the parent polymer, PMPP, used to make these and many other derivatives is described.

Pulmonary delivery of rifampicin-loaded soluplus micelles against Mycobacterium tuberculosis

Tuberculosis (TB) stands as the second “most deadly infectious disease” behind AIDS. Rifampicin (RIF) represents one of the most effective anti-TB drugs of the “short-term” oral TB therapy. However, the main limitations of the oral treatment are related with the lack of patient adherence and the development of multi-drug resistant Mycobacterium tuberculosis (Mtb) strains. Recently, the pulmonary administration of anti-TB drugs has become an attractive alternative to improve TB therapy. Hence, we have developed a respirable nanocarrier based on RIF-loaded polymeric micelles (PMs), employing a commercially available graft-copolymer of poly (vinyl caprolactam)-poly (vinyl acetate)-poly (ethylene glycol) (Soluplus). The RIF apparent aqueous solubility was increased (14.3-fold) and the micellar system was ranged in the nanoscale (~107 nm). Then, according to its in vitro aerodynamic behavior, our nanoformulation represented a suitable system for deep lung drug delivery. Interestingly, these inhalable RIF-loaded PMs enhanced (up to 2.5-fold) the in vitro drug microbicidal activity in Mtb-infected THP-1 macrophages versus a RIF solution. In addition, the biodistribution studies of the radiolabelled (99mTc) PMs demonstrated their lung accumulation over 24 hs in rats. Overall, this novel nanoformulation stands as an attractive platform for a potential inhalable TB therapy.

Design of Mechanically Robust Polymer Membranes for Non-Aqueous Flow Battery

Large scale grid storage is imperative for an efficient use of renewable energies. While aqueous redox flow batteries (RFBs) such as a vanadium-based aqueous RFB are relatively mature technologies for a grid storage, non-aqueous RFBs present an attractive alternative strategy for potentially providing much higher energy density. One of the key enablers for non-aqueous RFBs is mechanically robust and highly ion-conductive membranes. In aqueous RFBs, membranes can achieve high proton or anion conductivity due to water mediating their ion conduction, thus there are various high performance membranes for aqueous RFBs. On the other hand, for membranes in non-aqueous RFBs, achieving high ion conductivity while maintaining mechanical and chemical stability is a major challenge. The design principle for such membranes is poorly understood due to the complexity of the system. Our membranes are developed for a non-aqueous RFB with an alkali alloy anode technology that has the potential to achieve high energy density, high safety, low cost and long cycle life. This presentation will discuss the fundamental design principle in polymer membranes for non-aqueous RFBs and our recent efforts on the development of novel plasticized polymer membranes that simultaneously provide high conductivity and tailored mechanical modulus. In this study, mechanically robust crosslinked poly(ethylene oxide) membranes were synthesized and doped with sodium triflate and tetraglyme. The relationships between ion conductivity (reached up to 10-4-10-3 S/cm at r.t.), salt/gel content, glass transition temperature (Tg) and mechanical properties are investigated. The synthesized membranes are mechanically robust with storage modulus maintaining at ~1 MPa from -20 °C to 180 °C even saturated with tetraglyme. Furthermore, mechanically tailored novel single-ion conducting polymer electrolytes (SICPEs); block and graft copolymers of poly[(4-styrenesulfonyl) (trifluromethane-sulfonyl)imide] (poly(STF)) and poly[1-[3-(methacryloyloxy)-propylsulfonyl]-1-(trifluoromethanesulfonyl)imide] (poly(MPA)), were investigated. The SICPEs were synthesized by covalently attaching anionic moieties to the polymer backbones that only allows specific cations, such as lithium or sodium ions, to move freely and provide ionic conductivity (i.e. the transference number is close to 1) which is imperative for RFBs. These novel SCPE membranes include a membrane with a flexible polymer backbone to afford mechanical robustness and stretchability, and poly(STF) or poly(MPA) as side chains to provide single-ion conductivity. The effect of monomer type, degree of polymerization of the side chain, and different cations are also studied. The obtained polymer membrane showed 100% elongation and around 10-4 S/cm single-ion conductivity (no salt) at 30 °C after being doped with propylene carbonate. This work is funded by Dr. Imre Gyuk, Office of Electricity Delivery and Reliability, Department of Energy and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC.

Dual-phase all-polymeric membranes with graft copolymer filler for CO2 capture

We describe high-performance, dual-phase, all-polymeric membranes that simultaneously exhibit improved CO2 permeability and CO2/N2 selectivity. The membranes are fabricated by incorporating the graft copolymer poly(2-[3-(2H-benzotriazol-2-yl)-4-hydroxyphenyl]ethyl methacrylate)-graft-poly(oxyethylene methacrylate) (PBE) in a poly(amide-b-ether) block copolymer (Pebax) matrix. The amphiphilic PBE filler selectively interacts with Pebax, resulting in the formation of interconnected CO2-philic network channels within the matrix. The membranes exhibit a dual-phase, microphase-separated morphology, and good thermal/mechanical properties, as confirmed using transmission electron microscopy, differential scanning calorimetry, X-ray diffraction analysis, thermogravimetry analysis, and measurements performed on a universal testing machine. The CO2 and N2 permeabilities increase with the PBE content, with the maximum selectivity being observed at a PBE content of 5 wt%. The improved performance is attributable to the increased CO2 solubility owing to the efficient clustering of CO2-philic groups such as ether oxygens and triazole groups resulting from the dual-phase, interconnected morphology. The best performance corresponded to a CO2 permeability of 175.3 Barrer and a CO2/N2 selectivity of 48.2, which are much higher than those of neat Pebax (CO2 permeability of 103.3 Barrer and selectivity of 31.2) and approach the 2008 Robeson upper limit. Thus, these all-polymeric membranes are suitable for the commercialization of gas separation owing to their simple fabrication method and low cost.

Direct Organization of Morphology-Controllable Mesoporous SnO2 Using Amphiphilic Graft Copolymer for Gas-Sensing Applications.

A simple and flexible strategy for controlled synthesis of mesoporous metal oxide films using an amphiphilic graft copolymer as sacrificial template is presented and the effectiveness of this approach for gas-sensing applications is reported. The amphiphilic graft copolymer poly(vinyl chloride)-g-poly(oxyethylene methacrylate) (PVC-g-POEM) is used as a sacrificial template for the direct synthesis of mesoporous SnO2. The graft copolymer self-assembly is shown to enable good control over the morphology of the resulting SnO2 layer. Using this approach, mesoporous SnO2 based sensors with varied porosity are fabricated in situ on a microheater platform. This method reduces the interfacial contact resistance between the chemically sensitive materials and the microheater, while a simple fabrication process is provided. The sensors show significantly different gas-sensing performances depending on the SnO2 porosity, with the highly mesoporous SnO2 sensor exhibiting high sensitivity, low detection limit, and fast response and recovery toward hydrogen gas. This printable solution-based method can be used reproducibly to fabricate a variety of mesoporous metal oxide layers with tunable morphologies on various substrates for high-performance applications.

Fabrication and photodegradable properties of chitosan-g-poly(methyl vinyl ketones) nanoporous microspheres

ABSTRACTChitosan (CS) is a well-known natural polysaccharide with good biocompatibility and biodegradability. Graft copolymerization of poly (methyl vinyl ketone) (PMVK) onto chitosan was conducted by free radical method using KPS or CAN as an initiator. Nanoporous microspheres were synthesized by water-in-oil (W/O) emulsion method with glutaraldehyde(GA) as a closslinker, Tween80® as a emulsifier, followed by UV irradiation to confer nanopores by photodegradation of PMVK. Graft copolymers were characterized by FT-IR and NMR spectroscopies, and their grafting percentages were calculated by weight percentage residue of TGA thermograms. FE-SEM showed CS-g-PMVK microspheres were approximately 5 µm in diameter with rough surface due to photodegradation of PMVK by UV irradiation.

Simple Radical Polymerization of Poly(Alginate-Graft-N-Isopropylacrylamide) Injectable Thermoresponsive Hydrogel with the Potential for Localized and Sustained Delivery of Stem Cells and Bioactive Molecules.

In this study, thermoresponsive copolymers that are fully injectable, biocompatible, and biodegradable and are synthesized via graft copolymerization of poly(N-isopropylacrylamide) onto alginate using a free-radical reaction are presented. This new synthesis method does not involve multisteps or associated toxicity issues, and has the potential to reduce scale-up difficulties. Chemical and physical analyses verify the resultant graft copolymer structure. The lower critical solution temperature, which is a characteristic of sol-gel transition, is observed at 32 °C. The degradation properties indicate suitable degradation kinetics for drug delivery and bone tissue engineering applications. The synthesized P(Alg-g-NIPAAm) hydrogel is noncytotoxic with both human osteosarcoma (MG63) cells and porcine bone marrow derived mesenchymal stem cells (pBMSCs). pBMSCs encapsulated in the P(Alg-g-NIPAAm) hydrogel remain viable, show uniform distribution within the injected hydrogel, and undergo osteogenic and chondrogenic differentiation under appropriate culture conditions. Furthermore, for the first time, this work will explore the influence of alginate viscosity on the viscoelastic properties of the resulting copolymer hydrogels, which influences the rate of medical device formation and subsequent drug release. Together the results of this study indicate that the newly synthesized P(Alg-g-NIPAAm) hydrogel has potential to serve as a versatile and improved injectable platform for drug delivery and bone tissue engineering applications.

Grafted copolymer micelles with pH triggered charge reversibility for efficient doxorubicin delivery

ABSTRACTThe instability and premature charge reversal at pH 7.4 have become the major limitations of charge‐reversal delivery systems. To address this problem, graft copolymer of poly(butylene succinate)‐g‐cysteamine‐bi‐poly(ethylene glycol) (PBS‐g‐CS‐bi‐PEG, bi = benzoic imine bond) was designed and synthesized through facile thiol‐ene click reaction and subsequent Schiff's base reaction. Then, PBS‐g‐CS‐bi‐PEG and carboxyl‐functionalized polyester of poly(butylene succinate)‐g‐3‐mercaptopropionic acid (PBS‐g‐MPA) co‐assemble in aqueous solution to give PEG shell‐sheddable charge‐reversal micelles with sizes of 85–103 nm and low polydispersity of 0.11–0.12. Interestingly, the PBS‐g‐MPA/CS‐bi‐PEG micelles could sensitively and arbitrarily switch their surface charges between negative and positive status in response to pH fluctuation via reversible protonation and deprotonation of carboxyl and amino groups, which endows the desired stability of co‐assembly micelles either during long‐term storage or under physiological conditions. Doxorubicin (DOX) was loaded into PBS‐g‐MPA/CS‐bi‐PEG micelles with a high drug‐loading content of 10.2% and entrapment efficiency of 68% as a result of electrostatic attraction. In vitro release studies revealed that less than 25% of DOX was released within 24 h in the environment mimicking the physiological condition, whereas up to 81% of DOX was released in 24 h under weak‐acid condition resembling microenvironment in endosome/lysosome. In vitro cytotoxicity study suggested that blank PBS‐g‐MPA/CS‐bi‐PEG micelles possessed excellent biocompatibility, while DOX‐loaded PBS‐g‐MPA/CS‐bi‐PEG micelles showed significant cytotoxicity with half‐maximal inhibitory concentration (IC50) of 1.55–1.67 μg DOX equiv/mL. This study provides a facile and effective approach for the preparation of novel charge‐reversal micelles with switchable charges and excellent biocompatibility, which are highly promising to be used as safe nanocarriers for efficient intracellular drug delivery. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 2036–2046

Radiation Synthesis and Magnetic Property Investigations of the Graft Copolymer Poly(Ethylene-g-Acrylic Acid)/Fe3O4 Film

In this work, acrylic acid (AAc) monomer was grafted onto low-density polyethylene (LDPE) films by the direct method to obtain acid (LDPE-grafted poly(acrylic acid) (LDPE-g-PAAc)) graft copolymers. The presence of the grafted PAAc with COOH groups allows coupling with Fe2+/3+ ions. The stabilization of Fe3O4 particles onto the graft copolymers was done by in situ reduction of LDPE-g-PAAc/Fe2+/3+ with sodium borohydride (NaBH4) in aqueous solution. The LDPE-g-PAAc graft copolymer and LDPE-g-PAAc/Fe3O4 composite films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and electron spin resonance (ESR). The synthesized composites exhibit excellent magnetic properties. The results indicated that the magnetic oxide (Fe3O4) was embedded and homogenously dispersed into the surfaces of the graft copolymer films as indicated by SEM. The FT-IR analysis clearly suggests that an AAc monomer was effectively grafted onto LDPE. The XRD studies elucidate the change in the crystallinity of the graft copolymers.

Chromatographic study of the conformational behavior of graft copolymers with a broad distribution of grafting densities in dilute solutions in selective solvents for grafts

ABSTRACTA graft copolymer of poly(4-methylstyrene-graft-2-vinylpyridine) was prepared by the living “grafting onto” method. Its molecular weight and composition was analyzed by size-exclusion chromatography, liquid chromatography under limiting conditions of desorption, 1H NMR, and light scattering. The results indicated a non-negligibly broad distribution of grafting density. Its conformational behavior was studied by reversed phase liquid chromatography with gradient elution. Targeted studies provided two discrete base-line separated fractions. Their compositions were estimated by pyrolysis gas chromatography. The results suggest that distinct chain conformations (differing in grafting density and interacting differently with stationary phase) exist in studied solutions and can be separated by well-tuned chromatographic techniques. Experimental data were analyzed and interpreted on the basis of theoretical and computer studies of the conformational behavior of graft copolymers in selective solvents.

Cisplatin Loaded Poly(L-glutamic acid)-g-Methoxy Poly(ethylene glycol) Complex Nanoparticles for Potential Cancer Therapy: Preparation, In Vitro and In Vivo Evaluation.

A series of novel polypeptide-based graft copolymer poly(L-glutamic acid)-graft-methoxy poly(ethylene glycol) (PLG-g-mPEG) was synthesized through a Steglich esterification reaction of PLG with mPEG. The structure of the copolymers was confirmed by nuclear magnetic resonance spectra (NMR) and gel permeation chromatography (GPC). MTT assay demonstrated that the PLG-g-mPEGs had good cell compatibility. The unreacted carboxyl groups of the PLG-g-mPEGs were used to complex cisplatin to form polymer-metal complex nanoparticles (CDDP/PLG-g-mPEG) for cancer therapy. The average hydrodynamic radius of the CDDP/PLG-g-mPEG nanoparticles was inr the range of 14-25 nm, which was beneficial for solid tumor targeting delivery. A sustained release without initial burst was achieved for the CDDP/PLG-g-mPEG nanoparticles, indicating that the CDDP-loaded nanoparticles had great potential to suppress the drug release in blood circulation before the nanoparticles had arrived at targeting tumors. The CDDP/PLG-g-mPEG nanoparticles showed a much longer blood retention profile as compared with the free CDDP. This indicated that the CDDP-loaded nanoparticles had much more opportunity to accumulate in tumor tissue by exerting the EPR effect. In vitro tests demonstrated that the CDDP/PLG-g-mPEG nanoparticles could inhibit the proliferation of HeLa, MCF-7 and A549 cancer cells. At equal dose (4 mg kg(-1)), the CDDP/PLG-g-mPEG nanoparticles showed comparable in vivo antitumor efficacy and significantly lower systemic toxicity as compared with free cis-Diaminedichloroplatinum (cisplatin, CDDP) in MCF-7 tumor bearing mice. These suggested that the CDDP/PLG-g-mPEG nanoparticle drug delivery system had a great potential to be used for cancer therapy.

Synthesis of poly(vinyl alcohol-graft-lactic acid) copolymer and its application as medical anti-tissue adhesion thin film

Graft copolymers of poly(vinyl alcohol-g-lactic acid) (PVA-g-PLA) were synthesized through a direct polycondensation of d,l-lactic acid grafting from polyvinyl alcohol (PVA) using 1-ethyl-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC·HCl) as the catalyst. The molecular weights of the graft copolymers varied from 98,000 to 106,000, which were determined by gel permeation chromatography. It was observed that the glass transition temperatures of the copolymers decreased with the increase of lactic acid units in the copolymers. Thin films with the thickness of 0.04–0.06 mm were prepared using the copolymers. The films showed improved hydrophilicity and flexibility compared with PLA homopolymer. Small pieces of the films were implanted under the skin of mice for anti-tissue adhesion purpose. The films demonstrated good anti-tissue adhesion behavior and suitable degradability in the mouse body. The graft copolymers were non-toxic, flexible, blood compatible, non-cytotoxic and had potential applications as a medical anti-tissue adhesion agent.

High tolerated paclitaxel nano-formulation delivered by poly (lactic-co-glycolic acid)-g-dextran micelles to efficient cancer therapy

The amphiphilic graft copolymer poly (lactic-co-glycolic acid)-g-dextran (Dex-PLGA) was successfully synthesized to fabricate micelles for the delivery of paclitaxel with low critical micelle concentration (CMC). The sizes of paclitaxel-loaded Dex-PLGA (Dex-PLGA/PTX) micelles were kept below 100nm with a relatively narrow size distribution. This novel PTX nano-formulation was found to exhibit slightly stronger in vitro cytotoxicity against SKOV-3, OVCAR-8 and MCF-7 cells with Taxol®. However, it could overcome the drug resistance of multi-drug resistant human breast carcinoma cells (MCF-7/Adr cells). The maximum tolerated dose (MTD) of Dex-PLGA/PTX after a single dose was more than 200mg PTX/kg, which were 8-fold higher than that of Paclitaxel Injection. The in vivo antitumor activity results indicated that Dex-PLGA/PTX micelles treatments effectively suppressed the tumor growth and highly reduced the toxicity against animals than Taxol® and could eliminate the SKOV-3 tumor by highly increasing the drug dose. From the Clinical EditorChemotherapy for cancer has always been hampered the toxic side effect of the drugs. Nanotechnology has helped to produce various drug delivery systems to minimize these side effects. In this article, the authors designed dextran-based micelles loaded with paclitaxel. They showed effective anti-tumor activity in both in vitro and in vivo experiments with significant lower systemic toxicity.

Synthesis and Characterization of Graft Copolymers Poly(isoprene-g-styrene) of High Molecular Weight by a Combination of Anionic Polymerization and Emulsion Polymerization

In this work, high molecular weight “comb-shaped” graft copolymers, poly(isoprene-g-styrene), with polyisoprene as the backbone and polystyrene as side chains, were synthesized via free radical emulsion polymerization by copolymerization of isoprene with a polystyrene macromonomer synthesized using anionic polymerization. A small amount of toluene was used in order to successfully disperse the macromonomer. Both a redox and thermal initiation system were used in the emulsion polymerization, and the latex particle size and distribution were investigated by dynamic light scattering. The structural characteristics of the macromonomer and comb graft copolymers were investigated through use of size exclusion chromatography, spectroscopy, microscopy, thermal analysis, and rheology. While the macromonomer was successfully copolymerized to obtain the desired multigraft copolymers, small amounts of unreacted macromonomer remained in the products, reflecting its reduced reactivity due to steric effects. Nevertheless, the multigraft copolymers obtained were very high in molecular weight (5–12 × 105 g/mol) and up to 10 branches per chain, on average, could be incorporated. A material incorporating 29 wt % polystyrene exhibits a disordered microphase separated morphology and elastomeric properties. These materials show promise as new, highly tunable, and potentially low cost thermoplastic elastomers.