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  • 1
    Electronic Resource
    Electronic Resource
    Osteoblast migration on poly(α-hydroxy esters) (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 443-451 
    Details
    ISSN: 0006-3592
    Keywords: osteoblast ; migration ; poly(αhydroxy esters) ; poly(DL-lactic-co-glycolic acid) ; PLGA ; biodegradable polymers ; tissue engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: We investigated the migration of rat calvaria osteoblast populations on poly(α-hydroxy ester) films for up to 14 days to determine effects of substrate composition and culture conditions on the migratory characteristics of osteoblasts. Initial osteoblast culture conditions included cell colonies formed by seeding a high (84,000 cells/cm2) or low (42,000 cells/cm2) density of isolated osteoblasts on the polymer films, and bone tissue cultures formed by plating bone chips directly on the substrates. High density osteoblast colonies cultured and allowed to migrate and proliferate radially on 85:15 poly(DL-lactic-co-glycolic acid) (PLGA) films, 75:25 PLGA films, and tissue culture polystyrene controls demonstrated that the copolymer ratio in the polymer films did not affect the rate of increase in substrate surface area (or culture area) covered by the growing cell colony. However, the rate of increase in culture area was dependent on the initial osteoblast seeding density. Initial cell colonies formed with a lower osteoblast seeding density on 75:25 PLGA resulted in a lower rate of increase in culture area, specifically 4.9 ± 0.3 mm2/day, versus 14.1 ± 0.7 mm2/day for colonies seeded with a higher density of cells on the same polymer films. The proliferation rate for osteoblasts in the high and low density seeded osteoblast colonies did not differ, whereas the proliferation rate for the osteoblasts arising from the bone chips was lower than either of these isolated cell colonies. Confocal and light microscopy revealed that the osteoblast migration occurred as a monolayer of individual osteoblasts and not a calcified tissue front. These results demonstrated that cell seeding conditions strongly affect the rates of osteoblast migration and proliferation on biodegradable poly(α-hydroxy esters). © 1996 John Wiley & Sons, Inc.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    The growth and phenotypic expression of human osteoblasts (1996)
    Springer
    Cytotechnology 22 (1996), S. 263-267 
    Details
    ISSN: 1573-0778
    Keywords: biodegradable ; bone regeneration ; cell culture ; human cell osteoblasts ; polymers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The care of patients with a skeletal deficiency currently involves the use of bone graft or a non-biologic material such as a metal or polymer. There are alternate possibilities in development which involve the growth of bone cells (osteoblasts) on degradable polymer scaffolds. These tissue engineering strategies require production of the polymeric scaffold, cellular harvest followed by either ex vivo or in vivo growth of the cells on the scaffold, and exploration of the interaction between the cell and scaffold. Research into these strategies utilizes cells from a variety of species, but clinical applications will likely require human osteoblasts. This study explores the process whereby human osteoblasts are harvested under sterile conditions during joint replacement surgery from normally discarded cancellous bone, transported from the operating room to the lab, and grown in culture. This process is feasible, and the cells express their phenotype via the production of alkaline phosphatase and collagen in culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353947
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  • 3
    Electronic Resource
    Electronic Resource
    Prevascularization of porous biodegradable polymers (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 42 (1993), S. 716-723 
    Details
    ISSN: 0006-3592
    Keywords: prevascularization ; cell transplantation ; biodegradable polymers ; organ regeneration ; tissue engineering ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Highly porous biocompatible and biodegradable polymers in the form of cylindrical disks of 13.5 mm diameter were implanted in the mesentery of male syngeneic Fischer rats for a period of 35 days to study the dynamics of tissue ingrowth and the extent of tissue vascularity, and to explore their potential use as substrates for cell transplantation. The advancing fibrovascular tissue was characterized from histological sections of harvested devices by image analysis techniques. The rate of tissue ingrowth increased as the porosity and/or the pore size of the implanted devices increased. The time required for the tissue to fill the device depended on the polymer crystallinity and was smaller for amorphous polymers. The vascularity of the advancing tissue was consistent with time and independent of the biomaterial composition and morphology. Poly(L-lactic acid) (PLLA) devices of 5 mm thickness, 24.5% crystallinity, 83% porosity, and 166 μm median pore diameter were filled by tissue after 25 days. However, the void volume of prevascularized devices (4%) was minimal and not practical for cell transplantation. In contrast, for amporphous PLLA devices of the same dimensions, and the similar porosity of 87% and median pore diameter of 179 μm, the tissue did not fill completely prevascularized devices, and an appreciable percentage (21%) of device volume was still available for cell engraftment after 25 days of implantation. These studies demonstrate the feasibility of creating vascularized templates of amorphous biodegradable polymers for the transplantation of isolated or encapsulated cell populations to regenerate metabolic organs and tissues. © 1993 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260420606
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  • 4
    Electronic Resource
    Electronic Resource
    Mini-review: Islet transplantation to create a bioartificial pancreas (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 673-677 
    Details
    ISSN: 0006-3592
    Keywords: islet transplantation ; bioartificial pancreas ; immunoisolation ; extravascular devices ; macroencapsulation ; microencapsulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Donor scarcity precludes the use of pancreatic transplantation to treat type I diabetes. Xenogeneic islet transplantation offers the possibility of overcoming this problem; however, it entails the use of immunoisolation devices to prevent immune rejection of the transplanted islets. These devices consist of a semipermeable membrane, which surrounds the islets and isolates them from the host's immune system, while allowing the passage of insulin and essential nutrients, including glucose. Problems associated with proposed device designs include diffusion limitations, biocompatibility, device retrieval in the event of failure, and mechanical integrity. Microencapsulation appears to be the most promising system of immunoisolation, however, the design of a device suitable for human clinical use remains a challenge. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260430717
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  • 5
    Electronic Resource
    Electronic Resource
    Review: Hydrogels for cell immobilization (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 50 (1996), S. 357-364 
    Details
    ISSN: 0006-3592
    Keywords: hydrogel ; cell immobilization ; surface adhesion ; matrix entrapment ; microencapsulation ; immunoisolation ; bioartificial organs ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Hydrogels are being investigated for mammalian cell immobilization. Their material properties can be engineered for biocompatibility, selective permeability, mechanical and chemical stability, and other requirements as specified by the application including uniform cell distribution and a given membrane thickness or mechanical strength. These aqueous gels are attractive for analytical and tissue engineering applications and can be used with immobilization in therapies for various diseases as well as to generate bioartificial organs. Recent advances have broadened the use of hydrogel cell immobilization in biomedical fields. To provide an overview of available technology, this review surveys the current developments in immobilization of mammalian cells in hydrogels. Discussions cover hydrogel requirements for use in adhesion, matrix entrapment, and microencapsulation, the respective processing methods, as well as current applications. © 1996 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Brittle fracture of entangled polymers (1991)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 29 (1991), S. 837-841 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A stochastic model is presented to calculate the number of chain segments entangled about a unit plane when the segment length is a stochastic variable. This crossing density to which the brittle fracture energy and the critical strength of entangled polymers scale is a function of the number of moles of entanglement network strands per unit volume and the mesh size of the entanglement network. Experimental results of the molecular weight dependence of the fracture energy and strength validate the theoretical predictions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1991.090290708
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  • 7
    Electronic Resource
    Electronic Resource
    The physical mechanism for the production of hydrophilic polymer microparticles from aqueous suspensions (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 40 (1990), S. 997-1004 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: A previously reported method of producing spherical, hydrophilic microparticles by aqueous suspension polymerization is experimentally investigated. The phase separation is the result of a salting-out phenomenon. Characteristics of the salting-out effect between the monomer and suspending phase of aqueous NaCl solution are studied. The size and shape of the produced particles are characterized. It is concluded that the mechanism of polymerization is actually a combination of suspension and solution polymerization, and that the water content in the monomer phase is low enough to produce structurally homogeneous particles.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1990.070400532
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  • 8
    Electronic Resource
    Electronic Resource
    Reaction engineering aspects of suspension polymerization (1986)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 31 (1986), S. 2647-2659 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Suspension polymerization is used for the production of polymer particles with diameter in the range of 50-750 μm. The particle size distribution of the particles produced in batch-suspension polymerization is calculated using a population balance model. Power laws are derived for the average particle size and the standard deviation of the distribution. It is found that both quantities scale to the stable droplet mass of the initial dispersion of the organic phase into the aqueous one, which is a function of the agitation rate and the surface tension.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1986.070310820
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  • 9
    Electronic Resource
    Electronic Resource
    Preparation of poly(glycolic acid) bonded fiber structures for cell attachment and transplantation (1993)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 27 (1993), S. 183-189 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: A novel method was developed to prepare threedimensional structures with desired shapes used as templates for cell transplantation. The produced biomaterials are highly porous with large surface/volume and provide the necessary space for attachment and proliferation of the transplanted cells. The processing technique calls for the formation of a composite material with nonbonded fibers embedded in a matrix followed by thermal treatment and the selective dissolution of the matrix. To evaluate the technique, poly(glycolic acid) (PGA) fiber meshes were bonded using poly(L-lactic acid) (PLLA) as a matrix. The bonded structures were highly porous with values of porosity up to 0.81 and area/volume ratios as high as 0.05 μm-1. © 1993 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820270207
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  • 10
    Electronic Resource
    Electronic Resource
    Osteoblast function on synthetic biodegradable polymers (1994)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 1445-1453 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Rat osteoblasts were cultured on films of biodegradable poly(L-lactic acid) (PLLA), 75:25 poly(DL-lactic-co-glycolic acid) (PLGA), 50:50 PLGA, and poly(glycolic acid) (PGA) for up to 14 days. Osteoblasts attached equally well to all the polymer substrates after 8 h in culture. By day 4 in culture, osteoblasts had exceeded confluency numbers, and their proliferation leveled off by day 7. An increase in alkaline phosphatase (ALP) activity from 1.92 (±0.47) × 10-7 for day 7 to 5.75 (±0.12) × 10-7 μmol/cell per min for day 14 was reported for osteoblasts cultured on 75:25 PLGA, which was comparable to that observed for tissue culture polystyrene (TCPS) controls. The ALP activities expressed by osteoblasts cultured on PLLA, 50:50 PLGA, and PGA films did not significantly increase over time. Collagen synthesis for osteoblasts cultured on all polymer substrates was similar to that of TCPS and did not vary with time. The morphology of cultured osteoblasts was not affected by the continuous degradation of the polymer substrates. These results demonstrate that poly(α-hydroxy esters) can provide a suitable substrate for osteoblast culture and hold promise in bone regeneration by osteoblast transplantation. © 1994 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820281210
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