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Inkjet-printed proteins for cell patterning
BIOMATERIALS FOCUS
RESEARCH NEWS
Inkjet-printed proteins for cell patterning TISSUE ENGINEERING (a)
(b)
(c)
(d)
(a, b) Light microscopy images of printed collagen patterns. Light microscopy images of a printed collagen line pattern seeded with SMCs after culture for (c) one day and (d) four days (© 2004 Elsevier Ltd.)
The ability to micro-pattern surfaces with proteins provides the opportunity to align growing cells spatially to achieve twoand three-dimensionally controlled cell constructs. This will allow, for example, the growth of neuronal cells in lines for the fabrication of replacement neurons. Various groups have investigated a range of methods for printing proteins onto surfaces to control cell alignment and growth. Over recent years, inkjet printing in conjunction with computer-aided design (CAD) has been used in a variety of biotechnology applications including the preparation of microchips for DNA
arrays. Previous work has investigated the potential of using CAD in the fabrication of three-dimensional, polymeric scaffolds one layer at a time to allow the incorporation of pores and channels in the matrix. A group at Clemson University has investigated the use of conventional inkjet technology to pattern surfaces with collagen in two dimensions to control cell growth directly [Roth et al., Biomaterials (2004) 25, 3707]. The researchers demonstrate, using smooth muscle cells (SMCs), that inkjet technology can be used to create patterns of various geometries reproducibly, with a resolution of 350 µm, that support cell growth on agarose substrates. Lines, circles, dot arrays, and gradients of collagen can be patterned onto a substrate using standard PowerPoint software and printed using a modified Canon bubble-jet printer. Further studies using a neuronal culture of dorsal root ganglia allowed the researchers to demonstrate the successful establishment of a line pattern of dorsal root ganglia and glial cells after several days in culture. This technique clearly has the potential to provide uniquely cell-patterned constructs for cell surface engineering. It may also have further applications, through the development of multilayer techniques, for the fabrication of three-dimensional cellular constructs of controlled morphology for complete tissue reconstruction.
Porous scaffolds for cartilage repair TISSUE RECONSTRUCTION The reconstruction of damaged cartilage still represents a significant challenge to orthopedic clinicians. Various cell-based therapies are presently under evaluation using a range of different biological and nonbiological scaffolds. The nondegradable polymer system consisting of poly(ethyl methacrylate) and tetrahydrofurfuryl methacrylate (PEMA/THFMA) has previously been shown to support the growth and differentiation of bovine chondrocytes. In an attempt to develop a porous PEMA/THFMA scaffold for use in cartilage replacement, a multidisciplinary group from the University of Nottingham, UK has investigated the use of supercritical CO2 processing to produce a porous scaffold and undertaken an in vitro investigation into the growth of
chondrocytes on these novel foams [Barry et al., Biomaterials (2004) 25, 3559]. Polymer disks were prepared by curing the PEMA/THFMA system in polytetrafluoroethylene (PTFE) molds overnight. The disks were foamed using supercritical CO2 at 40°C and the porous materials characterized using scanning electron microscopy, mercury porosimetry, and helium pycnometry. Although the foams produced in this way are found to be more than 80% porous, with an open porosity in excess of 55%, the material produced has an external skin. The internal porous structure has a mean pore diameter of 99±60 µm. Following removal of the outer skin, the researchers found that chondrocytes cultured on the foamed materials maintain their rounded morphology better and synthesize more
(a)
(b)
(c)
(d)
Scanning electron micrographs of foamed PEMA/THFMA showing the (a) nonporous outer skin and (b) internal structure. Chondrocytes growing on the (c) unfoamed and (d) foamed PEMA/THFMA substrates after four days’ culture. (© 2004 Elsevier Ltd.)
glycosaminoglycan than cells cultured on unfoamed PEMA/THFMA. This supercritical-fluid-processed material may, therefore, have the
potential for optimization of the production of tissue-engineered constructs for cartilage reconstruction.
May 2004
21
RESEARCH NEWS
Inkjet-printed proteins for cell patterning TISSUE ENGINEERING (a)
(b)
(c)
(d)
(a, b) Light microscopy images of printed collagen patterns. Light microscopy images of a printed collagen line pattern seeded with SMCs after culture for (c) one day and (d) four days (© 2004 Elsevier Ltd.)
The ability to micro-pattern surfaces with proteins provides the opportunity to align growing cells spatially to achieve twoand three-dimensionally controlled cell constructs. This will allow, for example, the growth of neuronal cells in lines for the fabrication of replacement neurons. Various groups have investigated a range of methods for printing proteins onto surfaces to control cell alignment and growth. Over recent years, inkjet printing in conjunction with computer-aided design (CAD) has been used in a variety of biotechnology applications including the preparation of microchips for DNA
arrays. Previous work has investigated the potential of using CAD in the fabrication of three-dimensional, polymeric scaffolds one layer at a time to allow the incorporation of pores and channels in the matrix. A group at Clemson University has investigated the use of conventional inkjet technology to pattern surfaces with collagen in two dimensions to control cell growth directly [Roth et al., Biomaterials (2004) 25, 3707]. The researchers demonstrate, using smooth muscle cells (SMCs), that inkjet technology can be used to create patterns of various geometries reproducibly, with a resolution of 350 µm, that support cell growth on agarose substrates. Lines, circles, dot arrays, and gradients of collagen can be patterned onto a substrate using standard PowerPoint software and printed using a modified Canon bubble-jet printer. Further studies using a neuronal culture of dorsal root ganglia allowed the researchers to demonstrate the successful establishment of a line pattern of dorsal root ganglia and glial cells after several days in culture. This technique clearly has the potential to provide uniquely cell-patterned constructs for cell surface engineering. It may also have further applications, through the development of multilayer techniques, for the fabrication of three-dimensional cellular constructs of controlled morphology for complete tissue reconstruction.
Porous scaffolds for cartilage repair TISSUE RECONSTRUCTION The reconstruction of damaged cartilage still represents a significant challenge to orthopedic clinicians. Various cell-based therapies are presently under evaluation using a range of different biological and nonbiological scaffolds. The nondegradable polymer system consisting of poly(ethyl methacrylate) and tetrahydrofurfuryl methacrylate (PEMA/THFMA) has previously been shown to support the growth and differentiation of bovine chondrocytes. In an attempt to develop a porous PEMA/THFMA scaffold for use in cartilage replacement, a multidisciplinary group from the University of Nottingham, UK has investigated the use of supercritical CO2 processing to produce a porous scaffold and undertaken an in vitro investigation into the growth of
chondrocytes on these novel foams [Barry et al., Biomaterials (2004) 25, 3559]. Polymer disks were prepared by curing the PEMA/THFMA system in polytetrafluoroethylene (PTFE) molds overnight. The disks were foamed using supercritical CO2 at 40°C and the porous materials characterized using scanning electron microscopy, mercury porosimetry, and helium pycnometry. Although the foams produced in this way are found to be more than 80% porous, with an open porosity in excess of 55%, the material produced has an external skin. The internal porous structure has a mean pore diameter of 99±60 µm. Following removal of the outer skin, the researchers found that chondrocytes cultured on the foamed materials maintain their rounded morphology better and synthesize more
(a)
(b)
(c)
(d)
Scanning electron micrographs of foamed PEMA/THFMA showing the (a) nonporous outer skin and (b) internal structure. Chondrocytes growing on the (c) unfoamed and (d) foamed PEMA/THFMA substrates after four days’ culture. (© 2004 Elsevier Ltd.)
glycosaminoglycan than cells cultured on unfoamed PEMA/THFMA. This supercritical-fluid-processed material may, therefore, have the
potential for optimization of the production of tissue-engineered constructs for cartilage reconstruction.
May 2004
21