Human skin cell cultures onto PLA50 (PDLLA) bioresorbable polymers: Influence of chemical and morphological surface modifications
CRBA, UMR CNRS 5473, University Montpellier 1, Faculty of Pharmacy, 15 Avenue Charles Flahault, 34093 Montpellier Cedex 5, France. Journal of Biomedical Materials Research Part A
(Impact Factor: 3.37).
03/2005; 72(2):180-9. DOI: 10.1002/jbm.a.30216
Poly(alpha-hydroxy acid)s derived from lactic and glycolic acid are bioresorbable polymers which can cover a large range of thermal, physical, mechanical, and biological properties. Human keratinocytes have been shown as able to grow on a poly(DL-lactic acid) film. However the keratinocyte growth was delayed with respect to culture on standard tissue culture polystyrene, even though the same plateau level was observed after 2 weeks. In order to improve the performance of poly(DL-lactic acid) films as skin culture support, their surface was modified by creating tiny cavities using a method based on the leaching out of poly(ethylene oxide) from poly(lactic acid)-poly(ethylene oxide) heterogeneous blends. The surface of the films was also chemically modified by alkaline attack with sodium hydroxide and by type-I collagen coating. Murine fibroblast cell line and primary cultures of human fibroblasts and of two types of keratinocytes were allowed to adhere and to grow comparatively on the different films. The presence of cavities affected neither the adhesion of dermal fibroblasts nor that of keratinocytes. Only keratinocyte proliferation was significantly reduced by the presence of cavities. Collagen coating improved skin cell adhesion and proliferation as well, except in the case of murine fibroblasts. In the case of the NaOH treatments, similar trends were observed but their extent depended on the treatment time. In the case of chemical modifications, fluorescence microscopy bore out adhesion and proliferation tendencies deduced from MTT tests.
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ABSTRACT: In poly(DL-lactic acid)-cholesterol oligomers (LC), a novel cholesterol modified poly(DL-lactic acid) (PLA), was synthesized via bulk polymerization of DL-lactide using cholesterol initiator. Gel permeation chromatography (GPC) and 1H nuclear magnetic resonance spectroscopy (1H-NMR) results indicated a narrow molecular weight distribution of poly (DL-lactic acid)-cholesterol oligomers (LC). Mouse MC3T3 osteoblast-like cells were selected as a model system to test the cell behavior of cholesterol modified PLA substrates. The osteoblast attachment, proliferation, and viability revealed that the cholesterol modified PLA was significantly osteoblast compatible and may have potential as a bone tissue engineering material.
Available from: Michel Vert
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ABSTRACT: Historically, the search for polymeric systems that can better respect living systems in applications requiring a biomaterial for a limited period of time, started in the late sixties with the development of the so-called "bioabsorbable sutures" based on glycolic and lactic acids. As early as 1974, J. Leray and myself became interested in the use of synthetic polymers derived from hydroxyl-2 ethyl methacrylate after the pioneering work of G. Winter who showed that sponges of the Hydron ® -type promoted calcification in vivo (1). One of the shortcomings of this type of sponges was their poor mechanical properties and resistance to compression. For the sake of circumventing this shortcoming, we came to the idea that degradable polymers could behave like a sponge, degradation forming pores schematically. Starting from earlier work dealing with sutures and mandibula osteosynthesis, we selected lactic and glycolic acid-derived aliphatic polyesters (PLAxGAy where x and y stand for the percentage of L-lactyl and glycolyl units, respectively) as candidates. However, after a short period of preliminary animal investigations with L. Sedel and P. Christel, it appeared necessary to revisit the polymerisation processes in order to improve very much both intrinsic mechanical strength and lifetime to match the requirements of osteosynthesis. This period led us to select PLA98 for practical reasons that will be emphasised (2). The first application in human was performed in 1981, thanks to a traumatologist, Dr M. Audion. A company, Phusis, was created in 1984, thanks to A. Tornier, to develop bioresorbable materials for effective bone surgery. The commercial success came only on 1990 under the form of an interference screw (3). It is later on that we justified this choice after the identification of the number of factors that affect the hydrolytic degradation of PLAxGAy polymers, such as chemical, physical and configurational structures, polymerisation initiator and also size (4). From there, other devices were developed (5). It is from the success of lactic and glycolic-derived polymers that we introduced the concept of artificial biopolymers, i.e. of non-natural bioresorbable polymers made of building blocks that are normally present in biochemical pathways and that generate metabolites upon degradation or biodegradation. Accordingly, degradation by-products are biocompatible and can be eliminated and/or bioassimilated via natural pathways. As a consequence, we introduced polymers like poly(β-malic acid)s, poly(L-lysine citramide), poly(amino serinate and various copolymers (6), thus extending the fields of applications to functional bioresorbable polymers and polymer therapeutics, including drug delivery and drug targeting, domains that are still at the pioneering stage. However, because of the high therapeutic potential of PLAxGAy polymers, a demand appeared recently for methods aimed at modifying their intrinsic properties. The anionic activation of aliphatic polyesters using lithium di-isopropyl amidure (LDA) was introduced to make PLAxGAy surfaces functional and to create novel artificial biopolymers from poly(ε-caprolactone). Functionalisation of lactic and glycolic-derived polymers was also achieved by introducing gluconyl residues by copolymerisation. This route provides a original means to perform chemistry on PLAxGAy-type macromolecules (6). Recently, we approached the field of tissue engineering starting from the point that matching the degradation rate of the scaffold with the rate of tissue growth or tissue reconstruction is a key factor. The strategy was applied to skin culture and reconstruction. Our first approach was based again on PLAxGAy polymers. However, it was found that glycolic acid is unfavourable to keratinocyte growth whereas it does not affect the growth of other cell types. Once again PLAx appeared performing better in this type of application (7). According to the same strategy, we recently challenged the problem of bioresorbable stenting of coronary arteries. It was shown that PLAx-based stent prototype can be implanted in rabbit according to angioplasty and stenting in human (8). At the present time, the future of artificial biopolymers appears promising in surgery, in pharmacology and in tissue reconstruction. However, the most open domain is probably that of the medication of bioresorbable surgical devices made of artificial biopolymers and antibiotics, antitumoral agents, growth factors, etc., as already done with non-degradable polymers. A few more years are necessary to reach that ambitious stage. Acknowledgements The authors is grateful to his numerous co-workers and partners who contributed to the work exposed herein.
Available from: Ivan M Zorin
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ABSTRACT: These experiments were done to optimize the surface properties of polylactide film designed for human keratinocyte cultivation.
The film was covered with type 1 collagen to increase its hydrophilic properties. The method of protein application determines
the consistency the matrix coating and the formation of different collagen structures on the film. Substrates modified by
collagen affect the growth of cultured keratinocytes. Our data on keratinocyte spreading, morphology and cytoskeleton organization
demonstrate that the best form of collagen to use to cover the polymeric surface is the fibrillar isoform.
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