Synthesis and characterization of novel brush copolymers with biodegradable polyphosphoester side chains for gene delivery

A novel kind of pH‐sensitive brush copolymer [poly(2‐hydroxyethyl methacrylate)‐graft‐poly(ethylethylene phosphate)]‐block‐poly[2‐(dimethylamino)ethyl methacrylate] [(PHEMA‐g‐PEEP)‐b‐PDMAEMA] with biodegradable polyphosphoester as the side chains, and its self‐assembled aggregates were developed for nonviral gene delivery. The brush copolymers were synthesized via a combination of single‐electron transfer living radical polymerization and ring‐opening polymerization. The chemical structures of these brush copolymers were characterized by FTIR, ¹H NMR, and ³¹P NMR measurements. The critical aggregation concentration values of (PHEMA‐g‐PEEP)‐b‐PDMAEMA in pH 7.4 buffer solution were determined by the fluorescence probe technique. The interaction of (PHEMA‐g‐PEEP)‐b‐PDMAEMA and DNA was studied by agarose gel retardation assay, and the formed complexes were further investigated by means of zeta potential, dynamic light scattering, and transmission electron microscopy measurements. In addition, the in vitro cytotoxicity and transfection tests indicated that these brush copolymers showed low toxicity and favorable transfection efficiency to HeLa cells. All these results demonstrated that these biocompatible brush copolymers may be a promising candidate as nonviral polymeric gene vector. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013     

Synthesis and physicochemical characterization of biodegradable and pH‐responsive hydrogels based on polyphosphoester for protein delivery

In this work, a series of biodegradable and pH‐responsive hydrogels based on polyphosphoester and poly(acrylic acid) are presented. A novel biodegradable macrocrosslinker α‐methacryloyloxyethyl ω‐acryloyl poly(ethyl ethylene phosphate) (HEMA‐PEOP‐Ac) was synthesized by first ring‐opening polymerization of the cyclic monomer 2‐ethoxy‐2‐oxo‐1,3,2‐dioxaphospholane using HEMA as the initiator and Sn(Oct)₂ as catalyst, and subsequent conversion of hydroxyl into vinyl group. The hydrogels were then fabricated by the copolymerization of the macromonomer with acrylic acid, and their swelling/deswelling and degradation behaviors were investigated. The results demonstrated that the crosslinking density and pH values of media strongly influenced both the swelling ratio and the degradation rate of the hydrogels. The rheological properties of these hydrogels were also studied from which the storage modulus (G′) showed clear dependence on the crosslinking density. MTT and “live/dead” assay showed that these hydrogels were compatible to fibroblast cells, not exhibiting apparent cytotoxicity even at high concentrations. Moreover, in vitro bovine serum albumin release from these hydrogels was also investigated, and it could be found that the release profiles showed a burst effect followed by a continuous release phase, and the release rate was inversely proportional to the crosslinking density of hydrogels. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1919–1930, 2010     

Some novel layered-silicate nanocomposites based on a biodegradable hydroxybutyrate copolymer

This paper describes the preparation, characterization, mechanical properties and thermal stability of layered silicate nanocomposites based on poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHB-co-PHH, known as Nodax^TM). The dispersed phases were organically modified montmorillonites (clay 20A and clay 25A), mica, and talc, and they were introduced by solution mixing. Wide-angle X-ray scattering results and transmission electron microscopy (TEM) images confirmed that these two clays were intercalated and finely distributed in the Nodax^TM matrix. This type of layered filler led to remarkable improvements in mechanical properties even at very low loadings. Minimizing aggregation was more of a problem in the case of the mica and the talc, at least in this particular matrix. In some cases, these layered fillers slightly decreased the thermal stability of the Nodax^TM.     

新型中性载体PVC膜高选择性硫氰酸根电极研究

研究了新型Schiff碱对溴苯甲醛缩邻氨基酚过渡金属配合物的阴离子响应行为。实验结果表明:以Cu(Ⅱ)配合物为载体的电极对硫氰酸根具有优良的电位响应性能(pH4.0),电极的线性范围为1.0×10-1～2.0×10-5mol/L,斜率为-59.4mV/dec,检出限为9.0×10-6mol/L。其反Hofmeister选择性次序为:SCN->Sal->I->ClO4->NO2->NO3->Br->SO42->Cl-,研究了阴离子与载体的作用机理,结果表明SCN-与载体中铜原子直接作用。电极可应用于废水及人体唾液中SCN-的测定。     

Synthesis and characterization of novel biodegradable and electroactive hydrogel based on aniline oligomer and gelatin

A biodegradable electroactive hydrogel (AP-g-GA), aniline pentamer (AP) grafting gelatin (GA), is synthesized by a coupling reaction between the carboxyl group of AP and the amino side group of GA in aqueous solution. The electroactivity of the physical hydrogel is confirmed by UV-vis and CV. The hydrophobic AP changes the hydrogel's porous structure of the natural GA and the gel-time, which is confirmed by the rheological behavior of the AP-g-GA and GA. With an increase in the content of AP, the hydrogel gradually forms a porous structure, from "honeycomb" to "bamboo raft". The porous scaffolds can be crosslinked with 3.5% EDC in 90% ethanol. MTT assays show that the AP-g-GA exhibits reduced cytotoxicity compared to EM AP due to the introduction of the biocompatible GA moiety. The in vitro cell cultures suggest that the AP-g-GA#1 (with 1.9% AP) shows the best biocompatibility and cell adhesion ability.     

Photodegradation studies of novel biodegradable blends based on poly(ethylene oxide) and pectin

Blends of two biodegradable polymers: natural pectin and synthetic poly(ethylene oxide) at different weight-ratios were obtained by physical mixing in aqueous solutions, and evaporation of the solvent. The macromolecular order in the composites was investigated by applying X-ray diffraction, while the surface morphology was observed using atomic force microscopy. The photooxidative degradation of the blends was studied by viscometry, FTIR spectroscopy and UV-vis spectroscopy. It has been found that the susceptibility of the studied composites to UV radiation depends on an appropriate ratio of components, and the most sensitive to UV-irradiation among the samples studied was the equal weight-ratio blend of poly(ethylene oxide)/pectin.     

Synthesis and cell activity of novel galactosylated chitosan as a gene carrier

It is important for gene carrier to transport DNA into target cells. Although viral vectors are very efficient gene-transfer vehicles, significant drawbacks limit their applications. Chitosan (CS) has been researched widely as a non-viral vector. However, the low cell specificity and low transfection efficiency of chitosan need to be overcome. In order to conquer the drawback of chitosan, the present paper is concerned with the synthesis of novel galactosylated chitosan (GC) through etherization of chitosan and galactose in THF using BF₃·OEt₂ as promoter. The final product was characterized and confirmed by FT-IR and ¹H NMR. The degree of O-substitution (DS) of chitosan by galactose was measured to be 10.38% using anthrone-sulfuric acid colorimetric method. The mean particle diameter and average zeta potential of the GC/DNA complex were 350 nm and +22.1 mV, respectively. The GC/DNA nanoparticle was tested to transfect HEK293 cells, and the viability of HEK293 cells was not affected by the GC/DNA nanoparticle compared to that of the control.     

Polycaprolactone based biodegradable polyurethanes

Two series of segmented polyurethanes were prepared with systematic variation in soft and hard segment length. The soft segment was constituted by polycaprolactone (PCL) blocks of molecular masses 530 or 2000 and the hard segment (HS) by urethane blocks, in a concentration that varied from 12% to 44% in weight of the whole polyurethane. Morphological analyses indicated that the amount of crystallinity of copolymers was strongly dependent on the PCL molar mass and hard segment content. The copolymers with longer PCL soft segments (Mn=2000) were semicrystalline, but those with shorter PCL segment (Mn=530) were unable to crystallize. The primary factor affectingthe biodegradability of copolymers as evaluated by Sturm tests was the extent of the phase separation, and that the segmental blending of the less biodegradable polyurethane (HS) blocks with PCL in the amorphous phase had a critical unfavorable consequence, which may be attributed to the size of the accessible area by microorganisms.     

A degradable hyperbranched poly(ester amine) based on poloxamer diacrylate and polyethylenimine as a gene carrier

Polyethylenimine (PEI) is a well-known cationic polymer which has high transfection efficiency due to its buffering effect. However, nondegradability, cytotoxicity, aggregation, and short-circulation time in vivo still need to be overcome for a successful gene delivery. Degradable, hyperbranched poly(ester amine)s (PEAs) based on poloxamer diacrylate and low molecular weight branched PEI, were successfully synthesized and evaluated as a nonviral gene carrier. The PEAs were obtained in significant yields through Michael type addition reaction of diacrylate monomers and low molecular weight branched PEI. Analysis of degradation products by the reduction in molecular weight demonstrated that PEAs degrade in a controlled fashion. The PEA showed good DNA binding ability and the sizes of complexes under physiological condition were below 150 nm, implicating its potential for intracellular delivery. It showed lower cytotoxicity in three different cell lines (A549, 293T, and HepG2) compared with PEI 25K. PEAs showed much higher transfection efficiencies in three cell lines compared with PEI 25K and PEI 1.8K, and revealed little serum dependency in A549 cell line when the content of poloxamer in the PEA was increased up to 30%.     

Syntheses and evaluation of novel biodegradable amino acid based anhydride polymer resins and composites

A novel synthetic biodegradable oligomer based upon methacrylated aminocaproyl maleamic acid (MACMA), was synthesized and characterized. Injectable and in situ crosslinkable polymer networks were formulated by copolymerization of MACMA with triethyleneglycol dimethacrylate (TEGDMA). In addition, composites composed of MACMA, TEGDMA and beta-tricalcium phosphate (β-TCP) were prepared. The networks and composites were initiated by photo- and redox-polymerization, respectively. The initial compressive (CS) and diametral tensile strengths (DTS) of these materials were determined and used to evaluate the effects of MACMA/TEGDMA ratios on the degradation behavior of the materials. The neat resin networks exhibited initial CS values ranging from 6.7 to 284.2 MPa and the composites demonstrated initial DTS values ranging from 2.8 to 20.8 MPa and CS values ranging from 19.1 to 119.5 MPa. During the course of degradation the polymer neat resins lost 51%, 69% and 61% of their initial CS after 3 weeks for the MACMA/TEGDMA ratios at 25/75, 50/50 and 75/25, respectively. The resin with the MACMA/TEGDMA ratio of 75/25 completely degraded after 6 months. The composite with the MACMA/TEGDMA ratio of 25/75 exhibited a significant increase in CS after an initial decrease for 7 days and then lost 57% of its initial CS after 3 months. The composite composed of poly(MACMA) homopolymer showed a complete degradation after 21 days.     

Novel biodegradable polymers as gene carriers

This study investigated two new biodegradable polymers as gene controlled-released coatings for gene transfer. Poly(ethylene glycol)-co-poly(D,L-lactic acid) (PELA) and poly(ethylene glycol)-co-poly(lactic acid)-co-poly(glycolic acid) random copolymer (PELGA) were synthesized and used as microspheres matrices with encapsulated plasmid pCH110. The plasmid loading efficiency, cytotoxicity, transfection efficiency and in vitro degradation and release profiles of microsphere complexes were evaluated in details. The biodegradable polymers showed high DNA loading efficiency and low cytotoxicity as gene controlled-released coatings, and the poly(ethylene glycol) (PEG) contents of polymer matrices influenced the diameter, loading efficiency and transfection efficiency of plasmid DNA within the microspheres. The average diameters of PELA and PELGA microspheres were between 0.5 and 1.5 microm, and the plasmid loading efficiency was 62 and 73% for PELA and PELGA microspheres with 10% PEG content, respectively. In vitro testing showed a gradual release profile of DNA from polymeric matrices. The polymers/DNA microspheres had high transfection efficiency and early gene expression and maintenance of gene expression level for up to 96 h, although transfection efficiency were slightly lower than that of liposome in the initial 24 h. The biodegradable polymeric materials possess potential superiority as gene carriers.     

A PVC membrane pH-sensitive electrode based on methyldioctadecylamine as neutral carrier

A pH-sensitive PVC membrane electrode based on methyldioctadecylamine as neutral carrier has been prepared. It gives linear response over the pH-range 3.0-11.0 and a slope of - 58.4 +/- 0.3 mV/pH (at 20 degrees). The electrode has fairly low resistance and good potential reproducibility. The selectivity and other characteristics of the electrode have been studied.     

AFM study of a new carrier based on PLA and salen copolymers for gene therapy

The aim of this study was to synthesize novel biodegradable charged polymers to be used in DNA complexation for genetic delivery in different diseases. A new copolymer of PLA and complexed Schiff bases was synthesized in a several steps. This copolymer will be used as a nanocarrier. Also, AFM comparative studies in tapping mode were performed; on cationic copolymer and on PLA-Schiff base copolymer, on non-oriented and oriented film and on the DNA-cationic complex. The results indicated a difference in the topology and on phase picture of AFM film with or without cationic charge.     

Preparation and properties of novel biodegradable polyurethane networks based on castor oil and poly(ethylene glycol)

Polyurethane networks based on castor oil (CO) as a renewable resource polyol and poly(ethylene glycol) (PEG) with tunable biodegradation rates as potential candidates for biomedical implants and tissue engineering were synthesized through the reaction of epoxy-terminated polyurethane prepolymers (EPUs) with 1,6-hexamethylene diamine curing agent. EPUs themselves were prepared from reaction of glycidol and isocyanate terminated polyurethane prepolymers made from CO or PEG and 1,6-hexamethylene diisocyanate. All of the polymers were characterized by conventional methods, and their physical, mechanical and viscoelastic properties were studied. The results showed that the degradation rate and mechanical properties of final products could be controlled by the ratio of PEG or CO based EPUs in the final products. Increasing the PEG based EPU content caused an increase in hydrolytic degradation rate and mechanical properties. Evaluation of the L-929 fibroblast cells' interaction with prepared polymeric films showed nontoxic behavior and good cytocompatibility.     

A novel ferroelectric based on quinuclidine derivatives

The compound [(CH_3)_2 CH-C_3 H_(17) N][CoBr_4](1) based on quinuclidine derivatives was achieved by the solution synthetic method and characterized by elemental analysis,infrared spectroscopy,single-crystal X-ray structural analysis and dielectric measurement,respectively.Variable-temperature single-crystal X-ray diffraction suggested that the compound unde rwent the phase transition from the space group C2/c to Cc.The polarization curve was measured using the Sawyer-Tower circuit.The structural phase transitions of 1 was ascribed to the distortion of a [(CH_3)_2 CH-C_3 H_(17)N]~(2+) cation from this inorganicorganic hybrid material [(CH_3)_2 CH-C_3 H_(17)N][CoBr_4].The strong change in dielectric anomalies makes compound 1 a suitable candidate for promising switchable dielectric materials.This work represents a feasible strategy thought for the targeted harvesting of low temperature ferroelectrics.     

A novel drug carrier: lipophilic drug-loaded polyglutamate/polyelectrolyte nanocontainers

A novel lipophilic drug carrier, "oil-in-water" multifunctional composite nanocontainers, is developed by combining ultrasonic technique and layer-by-layer assembly. Polyglutamate/polyethyleneimine/poly(acrylic acid) nanocontainers loaded with the lipophilic drug, rifampicin, dissolved in soybean oil were fabricated. Raman confocal microscopy and scanning electron microscopy proved the successful incorporation of rifampicin into composite water-dispersible polyglutamate/polyelectrolyte nanocontainers. Transmission electron microscopy and confocal laser scanning microscopy indicated that the drug can be released by changing the pH value of the media due to the pH-responsive properties of the polyglutamate/polyelectrolyte shell.     

Mesostructured chitosan-silica hybrid as a biodegradable carrier for a pH-responsive drug delivery system

A biodegradable mesoporous chitosan-silica hybrid has been synthesized by self-assembly of non-toxic F127 Pluronic non-ionic surfactant, biodegradable chitosan and silica source through a real liquid-crystal templating route. On the basis of these biodegradable hybrids, we developed a facile one-pot pH-responsive drug delivery system relying on the coordinate bonding of a "host-metal-guest" architecture. Here, the "host", "metal" and "guest" represent amino groups of chitosan units, metal ions and drug molecules, respectively. Here, daunorubicin (DNR) was chosen as a typical anti-cancer drug molecule, the release of which can be achieved through the cleavage of the coordination bonds that are sensitive to variations in external pH at weak acidic conditions. The successful release of DNR has been observed at pH 5-6, while negligible release has been observed under physiological conditions. The existence of chitosan in the mesoporous silica enhanced both the biodegradability and the strength of the "host-metal-guest" coordination bond.