摘要:

This work investigates the cytocompatibility of several photoinitiating systems for potential cell encapsulation applications. Both UV and visible light initiating schemes were examined. The UV photoinitiators included 2,2-dimethoxy-2-phenylacetophenone (Irgacure 651), 1-hydroxycyclohexyl phenyl ketone (Irgacure 184), 2-methyl-1-[4-(methylthio) phenyl]-2-(4-morpholinyl)-1-propanone (Irgacure 907), and 2-hydroxy-1-[4-(hydroxyethoxy)phenyl]-2-methyl-1-propanone (Darocur 2959). The visible light initiating systems included camphorquinone (CQ) with ethyl 4-N,N-dimethylaminobenzoate (4EDMAB) and triethanolamine (TEA) and the photosensitizer isopropyl thioxanthone. A cultured fibroblast cell line, NIH/3T3, was exposed to the photoinitiators at varying concentrations from 0.01% (w/w) to 0.1% (w/w) with and without the presence of initiating light. The results demonstrated that at low photoinitiator concentrations (6 0.01% (w/w)), all of the initiator molecules were cytocompatible with the exception of CQ, Irgacure 651, and 4EDMAB which had a relative survival ~ 50% lower than a control. In the presence of low intensity initiating light (~ 6 mW cm-2 of 365 nm UV light and ~ 60 mW cm-2 of 470-490 nm visible light) and initiating radicals, Darocur 2959 at concentrations 6 0.05% (w/w) and CQ at concentrations 6 0.01% (w/w) were the most promising cytocompatible UV and visible light initiating systems, respectively. To demonstrate the potential use of cytocompatible photoinitiating systems in cell encapsulation applications, chondrocytes were encapsulated in a photocrosslinked hydrogel using 0.05% (w/w) Darocur 2959 (cytocompatible) and 0.01% (w/w) Irgacure 651 (cyto-incompatible). After photopolymerizing for 10 minutes with ~ 8 mW cm-2of 365 nm light, nearly all the chondrocytes survived the process with Darocur 2959 while very few of the chondrocytes survived the process with Irgacure 651.

ISSN:0920-5063    

DOI:10.1163/156856200743805

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

A method suitable for transfer of poly(ε-caprolactone) and poly(L-lactide) microspheres (synthesized by pseudoanionic dispersion polymerization of ε-caprolactone and L-lactide in heptane1,4-dioxane mixed solvent) from heptane to water was developed. This method consists of treating the microspheres with KOH-ethanol in the presence of surfactants (nonionic Triton X-405, anionic sodium dodecyl sulfate (SDS), and zwitterionic ammonium sulfobetaine-2 (ASB)). Partial hydrolysis of polyesters results in the formation of hydroxyl and carboxyl groups in the surface layer of microspheres and enhances their stability in water-based media. Minimal concentrations of surfactants, needed to obtain stable suspensions of particles, were equal to 3 × 10-2, and 6 × 10-2, and 3 × 10-2mol l-1for Triton X-405, SDS, and ASB, respectively. In the case of poly(ε-caprolactone) microspheres, suspensions in water were stable for all three surfactants for pH values ranging from 3 to 11. Suspensions of poly(L-lactide) were stable in the same range of pH values only for ASB. Surface charge density determined by electrophoretic mobility varied for poly(ε-caprolactone) microspheres from 2.6 × 10-7to 8.9 × 10-7mol m-2, for particles stabilized with Triton X-405 and ASB, respectively. In the case of poly(L-lactide) microspheres, surface charge density varied from 3.9 × 10-7 (stabilizer: Triton X-405) to 7.4 × 10-7mol m-2(stabilizer: ASB). Carboxyl groups located in the surface layer of poly(L-lactide) microspheres were used for covalent immobilization of 6-aminoquinoline, a fluorophore with an amino group. Maximum surface concentration of immobilized 6-aminoquinoline was equal to 1.9 × 10-6mol m-2. Poly(ε-caprolactone) microspheres transferred into water were loaded with ethyl salicylate. Loading up to 38% (w/w) was obtained.

ISSN:0920-5063    

DOI:10.1163/156856200743814

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Biological response of cells to implanted bone cement is a fundamental but often neglected issue in successful cemented implants. In this study, ten acrylic bone cements for orthopedics were assayed using two differentin vitrotesting methods on L929 cells. The cements were mixed as prescribed, cured for either 1 h or 7 days and then extracted in minimum essential medium (MEM) according to the ISO standard for the preparation of samples. For the evaluation of cytotoxicity, the neutral red uptake assay (NRU) and the incorporation of propidium iodide (PI) were used to detect the viability/death of cells. The two methods were shown to be well correlated (p< 0.0001) in the case of both the 1-h and the 7-day extracts. Two cements, i.e. CERIM LT and CMW2, were found to be toxic after 1-h curing through both the spectrophotometric NRU assay and the cytofluorometric assay with PI. After 7-day curing, these two cements, as well as the Zimmer-low viscosity cement, were toxic according to the NRU assay. The toxic effect of all the cements disappeared after dilution of extracts 1 :2 with MEM, except in the case of CERIM LT. In the search for the component inducing the toxic effect, the possible contribution of the residual monomer was discarded on the basis of literature data and the influence of various other factors was analyzed, including the contrast medium (barium sulphate or zirconium dioxide) and the concentrations ofN,N-dimethyl-paratoluidine and of benzoyl peroxide (< 1% or > 1%). Unlike zirconium dioxide, barium sulphate was found to damage the cells at the 1-h endpoint. Benzoyl peroxide at concentration > 1% was found to affect cells at the same endpoint, whereas dimethylparatoluidine had no effect regardless of the proportion.

ISSN:0920-5063    

DOI:10.1163/156856200743823

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Optimal results in biomaterial testing and tissue engineering under in vitro conditions can only be expected when the tissue generated resembles the original tissue as closely as possible. However, most of the presently used stagnant cell culture models do not produce the necessary degree of cellular differentiation, since important morphological, physiological, and biochemical characteristics disappear, while atypical features arise. To reach a high degree of cellular differentiation and to optimize the cellular environment, an advanced culture technology allowing the regulation of differentiation on different cellular levels was developed. By the use of tissue carriers, a variety of biomaterials or individually selected scaffolds could be tested for optimal tissue development. The tissue carriers are to be placed in perfusion culture containers, which are constantly supplied with fresh medium to avoid an accumulation of harmful metabolic products. The perfusion of medium creates a constant microenvironment with serum-containing or serum-free media. By this technique, tissues could be used for biomaterial or scaffold testing either in a proliferative or in a postmitotic phase, as is observed during natural development. The present paper summarizes technical developments, physiological parameters, cell biological reactions, and theoretical considerations for an optimal tissue development in the field of perfusion culture.

ISSN:0920-5063    

DOI:10.1163/156856200743832

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Cytocompatible polyurethane (PU)surface was prepared by photo-grafting 2-hydroxyethyl acrylate (HEA) onto the membrane surface. Graft polymerization was conducted by combining the use of the photo-oxidation and irradiation grafting. PU membrane was photo-oxidized to introduce the hydroperoxide groups onto the surface, then the membrane, immersed previously in monomer solution, was irradiated under UV light. The ATR-FTIR spectra, element spectroscopy for chemical analysis (ESCA), scanning electron microscopy (SEM) and water contact angle characterized the grafted copolymers and verified the occurrence of graft polymerization. The results showed that UV irradiation could realize the graft polymerization effectively and the grafting was confined within the surface layer. The grafted membrane showed minimal surface morphology. Human umbilical vein endothelial (HUVE) cells were seeded on the grafted surface. The performance of the surface in cell attachment and growth correlated with the oxygen content and mainly the carbonyl content on the surface. Cells were spread more extensively and grew faster on the surface with a higher oxygen content.

ISSN:0920-5063    

DOI:10.1163/156856200743841

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

Thermoplastic copolymers of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA) (molar ratio: 75/25 HEMA-MMA) were synthesized using HEMA containing different amounts of ethylene glycol dimethacrylate (EGDMA) to investigate their suitability for cell microencapsulation. Pure HEMA (0.0% EGDMA) was obtained with preparative chromatography to prepare a linear copolymer. Microcapsules (with a diameter of 300-400 μm) were readily made with the copolymers by interfacial precipitation. Smaller and more transparent capsules were obtained using the copolymer prepared from purer HEMA. Chinese hamster ovary (CHO) fibroblasts, as model cells, were microencapsulated in the linear copolymer. The CHO cells survived the microencapsulation process and the metabolic activity of the encapsulated cells increased within the 14 days observation period.

ISSN:0920-5063    

DOI:10.1163/156856200743850

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor