Photolithographically Patterned Cell-Repellent PEG-b-PTHPMA Diblock Copolymer for Guided Cell Adhesion and Growth

Surfaces for guided cell adhesion and growth are indispensable in several diagnostic and therapeutic applications. Towards this direction, four diblock copolymers comprising polyethylene glycol (PEG) and poly(2-tetrahydropyranyl methacrylate) (PTHPMA) are synthesized employing PEG macroinitiators of different chain lengths. The copolymer with a 5000 Da PEG block and a PEG-PTHPMA comonomers weight ratio of 43–57 provides a film with the highest stability in the culture medium and the strongest cell repellent properties. This copolymer is used to develop a positive photolithographic material and create stripe patterns onto silicon substrates. The highest selectivity regarding smooth muscle cell adhesion and growth and the highest fidelity of adhered cells for up to 3 days in culture is achieved for stripe patterns with widths between 25 and 27.5 µm. Smooth muscle cells cultured on such patterned substrates exhibit a decrease in their proliferation rate and nucleus area and an increase in their major axis length, compared to the cells cultured onto non-patterned substrates. These alterations are indicative of the adoption of a contractile rather than a synthetic phenotype of the smooth muscle cells grown onto the patterned substrates and demonstrate the potential of the novel photolithographic material and patterning method for guided cell adhesion and growth.     

A water-soluble PPDO/PEG alternating multiblock copolymer: Synthesis, characterization, and its gel-sol transition behavior

Biodegradable and nontoxic alternating multiblock copolymers based on poly (p-dioxanone) (PPDO) and poly (ethylene glycol) (PEG) were synthesized by the coupling reaction of two bifunctional prepolymers, a dihydroxyl-terminated PPDO and dicarboxylated PEG. The prepolymers and the resulting PPDO/PEG multiblock copolymers were characterized by various analytical techniques such as FT-IR, ¹H NMR, GPC, DSC and TG. At high concentration levels above critical gelation concentration (CGC), the aqueous solution of copolymers formed a gel. Temperature-sensitive gel to sol transition behaviors were investigated by the test tube inverting method. Dynamic light scattering (DLS) was used to investigate the micelle of copolymers, whose association probably caused the gelation of the system. Therefore, this novel copolymer has a great potential in injectable drug-delivery system for long-term delivery of drugs.     

聚丙交酯/聚乙二醇多嵌段共聚物的合成及其性能

聚丙交酯 (ＰＬＬＡ)由于具有良好的生物降解性和生物相容性 ,在医学领域已经得到了广泛的临床应用 ,近来又被制备成细胞支架大量应用于组织工程中[1,2 ] ,但由于其疏水性而造成细胞亲和性不好 .聚乙二醇 (ＰＥＧ)具有良好的亲水性 ,良好的生物相容性 ,但是ＰＥＧ是非降解性的 ,只有低分子量的ＰＥＧ可以被吞噬细胞所吞噬或透过肾滤膜而排出体外 ,因此 ,低分子量的ＰＥＧ常被用来与丙交酯 (Ｌ ＬＡ)共聚以改善ＰＬＬＡ支架的亲水性 .聚丙交酯 聚乙二醇共聚物 (ＰＬＥ)的三嵌段及两嵌段共聚物的合成及其性能的研究已被广泛报道[3～ 5] .研究…     

Crystallization behavior, thermal property and biodegradation of poly(3-hydroxybutyrate)/poly(ethylene glycol) grafting copolymer

The poly(3-hydroxybutyrate)(PHB)/poly(ethylene glycol)(PEG) grafting copolymer was successfully prepared by PHB and acrylate groups ended PEGM using AIBN as initiator. The crystallization behavior, thermal stability and environmental biodegradability of PHB/PEG grafting copolymers were investigated with differential scanning calorimetry (DSC), Thermogravimetric analysis (TGA), wide angle X-ray diffraction (WAXD), scanning electron microscopy (SEM), and Biodegradation test in vitro. In the results, all the grafting copolymers were found to show the X-ray diffraction arising from the PHB crystal lattice, while none of the PEG crystallized peaks could be found even though the graft percent reached 20%. This result indicated that PEG molecules were randomly grafted onto PHB chain. The thermal properties measured by DSC showed that the melting temperature(T_m) and glass transition temperature (T_g) were both shifted to lower temperature with the graft percent increasing, and this broadened the narrow processability window of PHB. According to TGA results, the thermal stability of the grafting copolymers is not changed compared to pure PHB. From the biodegradation test, it could be concluded that degradation occurred gradually from the surface to the inside and that the degradation rate could be adjusted by the PEG grafting ratio. In another words, the biodegradation profiles of PHB/PEG grafting copolymer can be controlled. These properties make PHB/PEG grafting copolymer have promising potential applications especially in agriculture fields.     

Controlling the degradation rate of thermoresponsive photo-cross-linked poly(organophosphazene) hydrogels with compositions of depsipeptide and PEG chain lengths

Thermosensitive and photo-cross-linkable poly(organophosphazenes) containing various amounts of isoleucine ethyl ester, AMPEG550, AMPEG750, aminoethyl methacrylate, and depsipeptide were synthesized, characterized, and were investigated for in vitro and in vivo degradation rates. The aqueous solutions of all polymers showed a sol-gel phase transition behavior against the temperature changes. The polymer degradation rate was majorly affected by the type and degree of the side group’s substitutions. The rate of degradation was initially dependent on the degree of photo-cross-linking, and in later stages on the amounts of the depsipeptide and PEG chain lengths in the polymer network. The amount of the pendant depsipeptide and chain length of the α-amino-ω-methoxy-poly(ethylene glycol) had significant impact on the polymer degradation rates. The polymers with high amount of the depsipeptide, and PEG750 showed fast degradation. These results suggest that the degradation rate of the injectable and dual cross-linkable gels can be tuned to the desired extent and may find wide utilities in various biomedical applications, where the gel strength and degradation rate are needed to be tightly regulated.     

Photocurable biodegradable poly(ɛ-caprolactone)/poly(ethylene glycol) multiblock copolymers showing shape-memory properties

Biodegradable multiblock copolymers were synthesized by a polycondensation of poly(ɛ-caprolactone) (PCL) diols of molecular weight (MW)=3,000 and poly(ethylene glycol)s (PEG) of MW=3,000 with 4,4′-(adipoyldioxy)dicinnamic acid (CAC) dichloride as a chain extender in diphenyl ether at 180 °C for 2 h, and were characterized by GPC, ¹H-NMR, FTIR, UV, DSC, and WAXS. These photosensitive copolymers were irradiated by a 400-W high-pressure mercury lamp (λ>280 nm) from 5–60 min to form a network structure. The gel contents increased with irradiation time, and attained ca. 90% after 60 min for all copolymers. The degree of swelling in a distilled water at ambient temperature, and the rate of degradation in a phosphate buffer solution (pH 7.2) at 37 °C increased with increasing PEG components. The shape-memory tests were performed by a cyclic thermomechanical experiments for the photocured CAC/PCL/PEG (75/25) films. The film with a gel content of 57% showed the best shape-memory property with strain fixity rate of 100% and strain recovery rate of 88%.     

聚对二氧环己酮/聚乙二醇多嵌段共聚物的合成与表征

首先合成双端羟基的聚对二氧环己酮预聚物(PPDO)和双端羧基的聚乙二醇预聚物(PEG),然后以丁二酸酐/二环己基碳二亚胺(DCC)将PPDO与PEG偶联共聚,得到PPDO/PEG多嵌段共聚物.通过1H-NMR和GPC表征了聚合物的结构和分子量.采用差示扫描量热法(DSC)和热重分析(TGA)研究了共聚物的结晶性能和热稳定性.用透析法制备了共聚物纳米粒子,并用动态光散射(DLS)表征了共聚物纳米粒子的粒径及分散度,结果表明,随着共聚物亲水链段PEG含量的增加,其纳米粒子更易形成,粒子粒径随共聚物分子量增大而增大.     

MICROPHASE SEPARATED STRUCTURES AND PROPERTIES OF PDMS-MDI-PEG COPOLYMER SURFACE

A series of poly(dimethylsiloxane)(PDMS)-4,4′-diphenylmethanediisocyanate(MDI)-poly(ethylene glycol)(PEG) multiblock copolymers were synthesized by employing two-step growth polymerization and investigated by AFM,XPS. contact angle system,protein adsorption and platelets adhesion measurements,respectively.It was found that as the molecular weight of PDMS increased,the surface of copolymers had increasing phase separation,while the increase in the molecular weight of PEG decreased the phase separation ext...     

Crystallization behavior and biodegradation of poly(3-hydroxybutyrate) and poly(ethylene glycol) multiblock copolymers

Block copolymerization by using isocyanates is an effective method for incorporating PHB and PEG because it can prepare copolymers with good properties, such as toughness, strength, and so on. In this study, we adopted soil suspension system to estimate the biodegradability of a series of PHB/PEG multiblock copolymers with different compositions and block lengths. In the degradation process, the changes in weight loss, molecular weight, and tensile strength were periodically measured to determine the biodegradability, and the surface morphology was also observed by SEM. In contrast to pure PHB, the weight loss of the copolymer was relatively lower. On the other hand, the tensile strength and molecular weight experienced apparent decrease, and for BHG1000-3-1, they reached 46.7% and 77.7% of the initial value, respectively. SEM observation showed that the surface was covered with numerous erosion pits. All these indicate that the degradation indeed took place and long-chain molecules have been hydrolyzed into shorter ones. The crystallization behavior was also investigated by DSC and WAXD. The results showed that both the segments, PEG and PHB, can form crystalline phases at lower PHB contents ranging from 29% to 44%, and when PHB component was more than 60%, only PHB phase can crystallize.     

An inflammation self-adaptive nanocarrier for highly efficient gene therapy

Inflammation represents a real micromilieu of many diseases as well as the actual application environment of nanocarriers. However, few studies have focused on the influence of the inflammatory environment on the effects of nanoparticle delivery. Herein, a novel inflammation self-adaptive nanocarrier is designed and fabricated by attaching the ascorbyl palmitate (AP) onto the surface of gene-entrapped polymeric nanocomplexes through the formation of phenylboronate bond. In vitro and in vivo studies demonstrate that the introduction of AP enhances considerably the accumulation of entrapped gene in inflammation and facilitates the intracellular uptake of gene-loading nanoparticles. Meanwhile, the gene transfection efficiency of DNA and in vivo gene therapy of nanocomplexes under an inflammation stimulus is significantly enhanced. Hence, our delicate design concept opens up a new pathway to develop an inflammation self-adaptive drug delivery system for precise drug/gene delivery and therapy.     

Synthesis and characterization of (AB)n-type poly(l-lactide)-poly(dimethyl siloxane) multiblock copolymer and the effect of its macrodiol composition on urethane formation

An (AB)_n-type multiblock copolymer containing alternating poly(l-lactide) (PLLA) and poly(dimethyl siloxane) (PDMS) segments was synthesized by chain extension of hydroxyltelechelic PLLA-PDMS-PLLA triblock copolymers, which were prepared by the ring-opening polymerization of l-lactide initiated by α,ω-functionalized hydroxyl poly(dimethyl siloxane), using 1,6-hexamethylene diisocyanate as a chain extender. The triblock and the multiblock copolymers were characterized by FT-IR, ¹H NMR and GPC. From the results of thermal analysis, two glass transition temperatures which were measured by DSC showed the occurrence of phase separation phenomena in the triblock and multiblock copolymers because of the difference of solubility parameters between PLLA and PDMS segments. The effect of the chemical composition of the triblock copolymers, including the Mw and the constitutive segment chain length of the macrodiol, on the development of the Mw of the multiblock was discussed based on diffusion effect. Furthermore, the consumption of the isocyanate groups was determined by FT-IR to investigate the dependence of the reaction kinetics of the urethane formation on the chemical composition of the triblock copolymer. The results reveal that the order of the chain extension reaction depended on the Mw of the triblock copolymer: a second order reaction was transformed into a third reaction as the Mw of the triblock copolymer increased from 7000 to 25,000 (g/mol) perhaps because of the inhibition of the formation of an active complex involved in the catalyzed-urethane reaction by the polymer chain aggregation. Finally, the mechanical properties of the multiblock copolymers demonstrated that the introduction of the extremely flexible PDMS segment substantially improved the elongation at breakage, and the tensile strength and the tensile modulus declined due to the intrinsic elasticity of such segments.     

聚乙二醇对苯二甲酸酯-b-聚对苯二甲酸丁二醇酯多嵌段共聚物内部贯通多孔支架的制备方法

以天然或合成的可生物降解材料制备细胞外基质支架是组织工程所涉及到的关键问题之一.常用的制备方法由于涉及到有机溶剂的使用、较高的加工温度以及致孔剂的残余问题,对于活性物质的引入均带来不利影响,相关的改进工作(如不使用有机溶剂和消除残余致孔剂等)尽管也获得了具有良好孔结构的支架,但却使制备过程更趋复杂.     

Polycaprolactone–poly(ethylene glycol) block copolymer,I: synthesis and degradability in vitro

A new type of biodegradable polymer material, poly(caprolactone)–poly(ethylene glycol) block copolymer (PCL-b-PEG), was synthesized by means of direct copolycondensation of ε-caprolactone with poly(ethylene glycol) in the presence of a Ti(OBu)₄ catalyst. The degradability of the polycaprolactone was improved by introducing a PEG component into it. The degradation of PCL-b-PEG copolymer increase with a decreasing crystallinity of the copolymer, and can be controlled by adjusting the component ratio of the copolymer.     

Preparation, characterization and biocompatibility of poly(ethylene glycol)-poly(n-butyl cyanoacrylate) nanocapsules with oil core via miniemulsion polymerization

A new type of nanocapsules with an oil core, coated by poly(ethylene glycol) (PEG) was designed. The loading efficiency and the biocompatibility of the polymeric nanocapsules were evaluated when it was used as a carrier for hydrophobic agent paclitaxel. The nanocapsules were synthesized through miniemulsion polymerization of butylcyanoacrylate (BCA) with PEG as initiator. The particle size and zeta potential of nanocapsules were influenced by the PEG content in the polymerization system. Fourier transform infrared (FTIR) spectra and ¹H NMR demonstrated the chemical coupling between PEG and poly(butylcyanoacrylate) (PBCA). Thermal characteristics of the copolymer were investigated by differential scanning calorimetry (DSC). The encapsulation efficiency increased concurrently with the increase of the PEG content in the system. The hemolytic assay and the cytotoxicity measurement showed that the PEG coating could significantly reduce the hemolytic potential and cytotoxicity of the nanocapsules. The results showed that the PEG-PBCA nanocapsules could be an effective carrier for hydrophobic agents.     

Surface modification of natural rubber film by polymerisation of methyl methacrylate in water-based system

Polymerisation of methyl methacrylate (MMA) on the surface of natural rubber (NR) film was studied in order to increase the surface hardness, roughness and, hence, to decrease the friction coefficient of rubber. We used the two-step process: (i) swelling of MMA and tert-butyl hydroperoxide, emulsified in an aqueous solution of sodium dodecyl sulphate, onto the NR film surface, and (ii) subsequently immersing the swollen rubber strip into an alkaline aqueous solution of ferrous ion/fructose for redox initiation. The presence of PMMA on the NR surface was examined by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR). Increasing the concentration of ferrous ion caused an increase in MMA conversion. The surface morphology observed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) in tapping mode revealed the aggregation of micronmetre-scale nodules on the modified surface. The surface hardness and roughness increased with increasing PMMA content.     

Fabrication and enhanced mechanical properties of porous PLA/PEG copolymer reinforced with bacterial cellulose nanofibers for soft tissue engineering applications

A new class of polylactic acid (PLA)/polyethylene glycol (PEG) copolymer reinforced with bacterial cellulose nanofibers (BC) was prepared using a solvent casting and particulate leaching methods. Four weight fractions of BC (1, 2.5, 5, and 10 wt%) were incorporated into copolymer via silane coupling agent. Mechanical properties were evaluated using response surface method (RSM) to optimize the impact of pore size, porosity, and BC contents. Compressive strength obtained for PLA/PEG-5 BC wt% was 9.8 MPa, which significantly dropped after developing a porous structure to 4.9 MPa. Nielson model was applied to investigate the BC stress concentration on the PLA/PEG. Likewise, krenche and Hapli-Tasi model were employed to investigate the BC nanofiber reinforcement and BC orientation into PLA/PEG chains. The optimal parameters of the experiment results found to be 5 wt% for BC, 230 μm for pore size, and 80% for porosity. Scanning electron microscopy (SEM) micrograph indicates that uniform pore size and regular pore shape were achieved after an addition of BC-5% into PLA/PEG. The weight loss of copolymer-BC with scaffolds enhanced to the double values, compared with PLA/PEG-BC % without scaffolds. Differential Scanning Calorimetric (DSC) results revealed that the BC nanofiber improved glass transition temperature (T_g) 57 °C, melting temperature (T_m) 171 °C, and crystallinity (χ %) 43% of PLA/PEG reinforced-BC-5%.     

Elastomeric/antibacterial properties in novel random Ricinus communis based-copolyesters

Poly(ricinoleic acid) (PRA), coming from the self-polycondensation of ricinoleic acid (RA), which derives from castor oil, is a very interesting polymer because of its intrinsic antimicrobial activity. However, its mechanical properties are insufficient for whatever application, thus copolymerization is required. In this work, two polyesters based on 1,3 propanediol (PD), such as poly(propylene terephthalate) (PPT) and poly(propylene isophthalate) (PPI), were chosen to prepare random copolyesters containing ricinoleate units. Different content of RA have been tested, such as 10 and 25 mol% respect to the comonomer (terephthalic or isophthalic dimethylester), to evaluate the lowest composition able to confer antibacterial activity. The materials were tested against Staphylococcus aureus and Escherichia coli, and 25 mol% of RA unit resulted to impart antimicrobial activity. Furthermore, thermal properties (DSC and TGA) as well as the elastomeric response of films were investigated. The copolymer PPI/PRA containing 10 mol% of RA presents very high elongation at break, around 1300%. Therefore, by tuning the RA amount it is possible to obtain outstanding elastomeric or antibacterial materials, suitable for textiles and/or film engineering applications.     

Effects of Grafting Density and Film Thickness on the Adhesion of Staphylococcus epidermidis to Poly(2‐hydroxy ethyl methacrylate) and Poly(poly(ethylene glycol)methacrylate) Brushes

Thin polymer films that prevent the adhesion of bacteria are of interest as coatings for the development of infection‐resistant biomaterials. This study investigates the influence of grafting density and film thickness on the adhesion of Staphylococcus epidermidis to poly(poly(ethylene glycol)methacrylate) (PPEGMA) and poly(2‐hydroxyethyl methacrylate) (PHEMA) brushes prepared via surface‐initiated atom transfer radical polymerization (SI‐ATRP). These brushes are compared with poly(ethylene glycol) (PEG) brushes, which are obtained by grafting PEG onto an epoxide‐modified substrate. Except for very low grafting densities (ρ = 1%), crystal violet staining experiments show that the PHEMA and PPEGMA brushes are equally effective as the PEG‐modified surfaces in preventing S. epidermis adhesion and do not reveal any significant variations as a function of film thickness or grafting density. These results indicate that brushes generated by SI‐ATRP are an attractive alternative to grafted‐onto PEG films for the preparation of surface coatings that resist bacterial adhesion.

     

LLDPE/SMA共混膜表面接枝PEG的研究

聚乙烯综合性能优良且价格低廉,但由于较低的表面能和惰性化学结构,其着色性、生物相容性及制品表面涂饰性能差,与各种涂饰剂的粘结强度很低,限制了其用途的拓展,须进行表面改性.聚乙烯制品的表面改性方法已有不少研究报道[1~4],相对而言,采用添加表面改性剂的方法在工艺上仍最     

Drying dissipative structures of aqueous solution of poly(ethylene glycol) on a cover glass, a watch glass, and a glass dish

Drying dissipative structures of aqueous solution of poly(ethylene glycol) (PEG) of molecular weights ranging from 200 to 3,500,000 were studied on a cover glass, a watch glass, and a glass dish on macroscopic and microscopic scales. Any convectional and sedimentation patterns did not appear during the course of drying the PEG solutions. Several important findings on the drying patterns are reported. Firstly, the crystalline structures of the dried film changed from hedrites to spherulites as the molecular weight and/or concentration of PEG increased. Secondly, lamellae were formed along the ring patterns especially at high concentrations and high molecular weights. The coupled crystalline patterns of the spherulites and the lamellae were observed in a watch glass along the ring structures, supporting the important role of the convection by the gravity during the course of dryness. The coupled patterns were difficult to be formed on a cover glass and a glass dish, except at the outside edge of the dried film. Thirdly, the size of the broad ring at the outside edge of the dried film especially on a cover glass and a watch glass increased sharply as the molecular weight increased and also as the polymer concentration increased. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.