Poly(2-oxazoline)s as materials for biomedical applications

The conjunction of polymers and medicine enables the development of new materials that display novel features, opening new ways to administrate drugs, design implants and biosensors, to deliver pharmaceuticals impacting cancer treatment, regenerative medicine or gene therapy. Poly(2-oxazoline)s (POx) constitute a polymer class with exceptional properties for their use in a plethora of different biomedical applications and are proposed as a versatile platform for the development of new medicine. Herein, a global vision of POx as a platform for novel biomaterials is offered, by highlighting the recent advances and breakthroughs in this fascinating field.     

Evaluation of photochemically immobilized poly(2-ethyl-2-oxazoline) thin films as protein-resistant surfaces

Poly(2-ethyl-2-oxazoline) (PEOX) of various molecular weights were covalently immobilized on silicon wafers and gold slides to form protein-resistant surfaces via a fast and general photocoupling chemistry based on the CH insertion reaction of light-activated perfluorophenyl azide (PFPA). The thicknesses of the immobilized PEOX films ranged from 23 to 80 ? for molecular weight of 5000 to 500,000, and the grafting density reached 3.2 × 10(-3) ?(-2) for PEOX 5000. The protein-resistant property of the films was studied using bovine serum albumin (BSA) by fluorescence imaging, ellipsometry, and surface plasmon resonance imaging (SPRi). The fluorescence imaging and ellipsometry studies showed the largest amount of BSA adsorbed on PEOX 5000 and the smallest on PEOX 500,000. This was consistent with the kinetic analysis of BSA adsorption by SPRi showing that PEOX 5000 exhibited the fastest association rate and the slowest dissociation rate whereas PEOX 500,000 had the slowest association rate and the fastest dissociation rate. The PEOX film was then applied in the fabrication of carbohydrate microarrays to reduce the nonspecific adsorption of lectins and thus the background noises. Results showed that the microarray signals were significantly enhanced when the PEOX film was used.     

Electrospinning of poly (2-ethyl-2-oxazoline)

Poly (2-ethyl-2-oxazoline) (PEOZ) is one of the commercial members of a family of materials that have shown significant application potential in a large number of technological contexts, most of them related with biomedical problems where water-soluble polymer systems are highly desirable. Polymeric fibers with diameters in the 200–800 nm range of PEOZ were prepared by electrospinning of its water solutions. Processing and solution parameters effects on the morphology and the diameter of the fibers were investigated. SEM results showed that the polymer concentration and the applied voltage might be used as variables to control the morphology and the diameter of the electrospun fibers. Solutions of the same polymer in other two organic solvents (N,N-dimethylformamide (DMF) and tetrahydrofurane (THF)) were also processed by the same technique but without the promising results of the water solutions.     

Significantly improved adhesion of poly(3,4-ethylenedioxythiophene) nanofilms to amino-silane monolayer pre-patterned SiO2 surfaces

This study reports a novel patterning method for highly pure poly(3,4-ethylenedioxythiophene) (PEDOT) nanofilms having a particularly strong adhesion to a SiO2 surface. An oxidized silicon wafer substrate was micro-contact printed with n-octadecyltrichlorosilane (OTS) monolayer, and subsequently its negative pattern was self-assembled with three different amino-functionalized alkylsilanes, (3-aminopropyl)trimethoxysilane (APS), N-(2-aminoethyl)-3-aminopropyltrimethoxy silane (EDAS), and (3-trimethoxysilylpropyl) diethylenetriamine (DETS). Then, PEDOT nanofilms were selectively grown on the aminosilane pre-patterned areas via the vapor phase polymerization method. To evaluate the adhesion and patterning, the PEDOT nanofilms and SAMs were investigated with a Scotch tape test, contact angle analyzer, optical and atomic force microscopes. The evaluation revealed that the newly developed bottom-up process can successfully offer a strongly adhered and selectively patterned PEDOT nanofilm on an oxidized Si wafer surface.     

Response of primary fibroblasts and osteoblasts to plasma treated polyetheretherketone (PEEK) surfaces

Polyetheretherketone (PEEK) is a synthetic polymer with suitable biomechanical and stable chemical properties, which make it attractive for use as an endoprothetic material and for ligamentous replacement. However, chemical surface inertness does not account for a good interfacial biocompatibility, and PEEK requires a surface modification prior to its application in vivo.In the course of this experimental study we analyzed the influence of plasma treatment of PEEK surfaces on the cell proliferation and differentiation of primary fibroblasts and osteoblasts. Further we examined the possibility of inducing microstructured cell growth on a surface with plasma-induced chemical micropatterning.We were able to demonstrate that the surface treatment of PEEK with a low-temperature plasma has significant effects on the proliferation of fibroblasts. Depending on the surface treatment, the proliferation rate can either be stimulated or suppressed. The behavior of the osteoblasts was examined by evaluating differentiation parameters.By detection of alkaline phosphatase, collagen I, and mineralized extracellular matrix as parameters for osteoblastic differentiation, the examined materials showed results comparable to commercially available polymer cell culture materials such as tissue culture polystyrene (TCPS). Further microstructured cell growth was produced successfully on micropatterned PEEK foils, which could be a future tool for bioartificial systems applying the methods of tissue engineering.These results show that chemically inert materials such as PEEK may be modified specifically through the methods of plasma technology in order to improve biocompatibility.The first two authors share first authorship.     

Cell adhesion and accelerated detachment on the surface of temperature-sensitive chitosan and poly(N-isopropylacrylamide) hydrogels

A series of temperature-sensitive poly(NIPAAm-co-CSA) hydrogels were synthesized by the copolymerization of acrylic acid-derivatized Chitosan (CSA) and N-isopropylacrylamide (NIPAAm) in aqueous solution. Their swelling properties and L929 cell adhesion and detachment behaviors were studied. It was found that poly(NIPAAm-co-CSA) hydrogels were temperature-sensitive associated with the roles of the component PNIPAAm. Most significantly, poly(NIPAAm-co-CSA) hydrogels exhibited simultaneously good swelling properties. The investigation of L929 cell adhesion and detachment of poly(NIPAAm-co-CSA) hydrogels indicated the cell adhesion and spreading was higher on the surface of poly(NIPAAm-co-CSA) hydrogels than that of PNIPAAm hydrogel at 37 degrees C due to the incorporation of CS, which having excellent cell affinity. Poly(NIPAAm-co-CSA) hydrogels showed more rapid detachment of cell sheet compared to PNIPAAm hydrogel because of the highly hydrophilic and hygroscopic nature of CS chains when reducing the culture temperature from 37 degrees C to 20 degrees C.     

Poly(carbazole-co-acrylamide) electrocoated carbon fibers and their adhesion behavior to an epoxy resin matrix

The surface properties of original high strength and preoxidized high modulus carbon fibers were altered by electrocopolymerizing acryl amide and carbazole and therefore depositing a copolymer coating onto the fibers. Scanning electron microscopy and zeta-potential measurements confirmed the presence of a rough but dense and continuous electrocoating with a basic surface character. Therefore, good adhesion behavior between the electrocoated carbon fibers and an epoxy resin matrix should be expected. The interfacial adhesion was measured using the single fiber pull-out and single fiber indentation test. It was shown that only intermediate adhesion was present between the carbon fibers and the electrocoating, but superior adhesion between the coating and epoxy resin exists. The single fiber model composites always failed at the fiber/electrocoating interface. However, as shown by using the indentation test, the interfacial adhesion between fibers and electrocoating can be significantly improved if preoxidized fibers are used as substrate for electropolymerization. A very high tensile strength for the electrocoating can be expected as derived from the single fiber pull-out tests.     

Characterization of Poly(2-Hyoroxyethyl Methacrylate) Gels

The crosslinking density and pore sizes of poly(2-hydroxyethyl methacrylate) (polyHEMA) hydrogels have been measured and correlated with the diffusion characteristics of a solute through the polymer. Studies indicated that diffusion is hindered both by obstruction by the polymer chains and by the immobility of the solvent within the gel. Values for the diffusion coefficient of a solute, D, and interaction parameters between the solvent and polymer suggest that as the concentration of crosslinking agent in the polymer network increases, the hydrophohicity of the polymer and the mobility of the solvent in the gel increase. Increased crosslinking however, increases the effectiveness of the obstruction effect, and the overall effect is a reduction in D.     

Characterization of Poly(2-Hyoroxyethyl Methacrylate) Gels

Abstract

The crosslinking density and pore sizes of poly(2-hydroxyethyl methacrylate) (polyHEMA) hydrogels have been measured and correlated with the diffusion characteristics of a solute through the polymer. Studies indicated that diffusion is hindered both by obstruction by the polymer chains and by the immobility of the solvent within the gel. Values for the diffusion coefficient of a solute, D, and interaction parameters between the solvent and polymer suggest that as the concentration of crosslinking agent in the polymer network increases, the hydrophohicity of the polymer and the mobility of the solvent in the gel increase. Increased crosslinking however, increases the effectiveness of the obstruction effect, and the overall effect is a reduction in D.     

偶联法制备聚羟基丁酸酯/聚乙二醇共聚物及其性能

利用二异氰酸酯为偶联剂,采用不同分子量的聚乙二醇(PEG)与聚羟基丁酸酯(PHB)进行偶联反应,制备一系列聚羟基丁酸酯/聚乙二醇共聚物。利用红外光谱(FT-IR)、差示扫描量热(DSC)、广角X射线衍射(WAXD)、表面水相接触角及力学性能实验对共聚物进行了分析研究。结果表明,偶联聚乙二醇后,PHB链的规整度降低,PHB的结晶度下降,非结晶区增大,同时表面亲水性变好,当采用高分子量的PEG后,共聚物的拉抻应力-应变曲线中出现了明显的屈服点,断裂伸长率也有了较大的提高,达到了11%,韧性得到改善,力学性能有一定程度的提高。     

两种聚噻吩类新型电致发光材料的合成与性能

报道了以无水FeCl3为催化剂合成异戊基取代和戊氧基取代聚噻吩的实验过程,两种聚合物稀溶液和薄膜的光发射、光吸收性能和用这两种材料作发光层制作的发光二极管的光电性能的初步研究结果.两种聚合物均具有较高的纯度和分子量.两种材料均显示了较好的发光性能,其电致发光颜色均为红橙色.烷氧基取代聚噻吩均聚物电致发光性能在学术界尚属首次发现.     

Nanoengineered surfaces enhance drug loading and adhesion

To circumvent the barriers encountered by macromolecules at the gastrointestinal mucosa, sufficient therapeutic macromolecules must be delivered in close proximity to cells.(1) Previously, we have shown that silicon nanowires penetrate the mucous layer and adhere directly to cells under high shear.(2) In this work, we characterize potential reservoirs and load macromolecules into interstitial space between nanowires. We show significant increases in loading capacity due to nanowires while retaining adhesion of loaded particles under high shear.     

聚醚共聚酰胺复合气体分离膜对CO2/N2分离性能的研究

以烟道气中CO2的捕集为研究背景,以聚醚共聚酰胺Pebax1657嵌段共聚物为选择层膜材料,采用浸渍涂覆法,制备具有超薄分离皮层的PEI/PDMS/Pebax1657/PDMS多层复合气体分离膜,研究复合气体分离膜对CO2/N2混合气的分离特性.由于CO2的增塑作用,复合膜对CO2/N2混合气的分离系数为40左右,低于其理想分离系数.操作压力和原料气中CO2浓度对复合膜的渗透分离性能以及混合气的分离效果影响显著.在实际应用中,可通过调节膜两侧操作压力来提高CO2的富集浓度.     

溴甲基化法合成聚[2-甲氧基-5-(2’-乙基己氧基)对苯乙炔]

以对甲氧基苯酚和溴代异辛烷为原料,经醚化、溴甲基化、脱溴化氢反应,成功合成聚[2-甲氧基-5-(2’-乙基己氧基)对苯乙炔](MEH-PPV),其数均分子量为5.7×104。利用傅立叶变换红外光谱(FTIR)、核磁共振波谱(1H-NMR)及紫外可见分光光谱(UV-Vis)对中间产物及MEH-PPV进行结构表征,结果表明,合成的中间产物和MEH-PPV分子结构与文献报道的一致。     

Biodegradable Poly(Lactic Acid) and Poly (Lactide-Co-Glycolide) Polymers in Sustained Drug Delivery

Poly(lactic acid) [PLA] and its co-polymers with glycolic acid [PLCG] have been known for the past 20 years of its biodegradability and histocompatibility. Their physico-chemical and biological properties have been found suitable, in many instances, for sustaining drug release in vivo and in vitro from days to months. A wide variety of drugs ranging from small molecular weight therapeutic agents to peptide hormones, antibiotics, chemotherapeutic drugs have been studied using these biodegradable polymers. Several parenteral and oral dosage forms have been investigated, which includes microcapsules, implants, pseudolatices, nanoparticles, tablets, films as well as occular devices for local delivery of drug into the eye. An attempt have been taken in this paper to review the prospect of using these biodegradable polymers for long term parenteral drug delivery of different classes of drugs.     

Microstructuring of polyelectrolyte coated surfaces for directing capsule adhesion

We use microcontact printing (/spl mu/CP) of polyelectrolytes (PEs) onto flat substrates for creating surfaces with regions of negative and positive surface charge. Subsequent incubation of these surfaces with solutions containing hollow PE capsules leads to preferential adsorption of the capsules on regions of opposite charge, while regions of like charge are passivated against adhesion. As well, adsorption of fluorescently labeled PEs is found to be directed toward oppositely charged regions at neutral pH. This approach could lead to novel functional surfaces for combinatorial chemistry or sensor applications and could also be expanded toward cell immobilization.