R, as with all avascular synthetic materials, these polymers are limited by an increased susceptibility to Title Loaded From File infection and the risk of extrusion, as well as complications due to poor biocompatibility, host immune responses [2,8,9], potentially inflammatory degradation products, and unknown longevity and stability over time [2,9]. Among the synthetic materials most commonly utilized for tissue-engineered auricular reconstruction are (FDA approved) polyglycolic acid (PGA) and polylactic 1655472 acid (PLA) [4,8,9], polymers typically used together due to the cell compatibility of the former and the maintenance of strength over time of the latter. Despite their frequent use, however, these materials have been noted to incite unwanted inflammatory reactions [2,3], attributed by some to the products of PLA degradation [6,7]. In addition, high-density porous polyethylene (HDPP) scaffolds, while biocompatible and often used clinically for reconstructive purposes in other anatomic regions, are quite rigid unlike auricular native cartilage [3] and associated with increased rates of infection and extrusion [10], thus resulting in suboptimal reconstructions. Synthetic (i.e., poloxamer) and naturally derived hydrogels (i.e., alginate, agarose, or fibrin) have similarly been evaluated as substrates for auricular tissue-engineered scaffolds as they are easily molded, potentially injectable, and “provide a hospitable three-dimensional support matrix” for cells contained within [3]. While biodegradable and used clinically, fibrin hydrogels are limited by their low tensile strength and poor surgical handling and are thus most often used as a coating for other, lessbiocompatible materials to increase their cellular compatibility [4,11]. Like fibrin, the extracellular matrix component collagen is abundant, biocompatible, and can be used in hydrogel form [12]. Indeed, collagen hydrogels have been utilized previously for cartilage tissue engineering applications, albeit with mixed results including the inability to independently maintain original cast dimensions without the use of an internal support [12,13]. With the recent explosion of digital technology, computerassisted design/computer-assisted manufacturing (CAD/CAM) techniques have emerged as a viable means of fabricating specific three-dimensional structures based upon virtual images. Despite the immense potential CAD/CAM approaches offer the field of tissue-engineered microtia reconstruction, few groups have effectively applied this technology towards auricular scaffold fabrication [7,14]. Furthermore, digital acquisition of three-dimensional data has commonly relied on modalities such as computed tomography [7], which is expensive and imparts harmful ionizing radiation.We therefore sought to combine digital photogrammetry with CAD/CAM techniques to develop high-density collagen type I hydrogel scaffolds and their respective molds that would precisely mimic the normal anatomy of the patient-specific external ear as well as recapitulate the complex biomechanical properties of native auricular elastic cartilage while avoiding the morbidity of traditional autologous reconstructions.Methods Ethics StatementAll animal care and experimental procedures were in compliance with the Guide for the Care and Use of Laboratory Animals [15] and were approved by the Weill Cornell Medical College Institutional Animal Care and Use Committee (protocol # 20110036). All Title Loaded From File efforts were made to minimize suffering.Isolation of chondr.R, as with all avascular synthetic materials, these polymers are limited by an increased susceptibility to infection and the risk of extrusion, as well as complications due to poor biocompatibility, host immune responses [2,8,9], potentially inflammatory degradation products, and unknown longevity and stability over time [2,9]. Among the synthetic materials most commonly utilized for tissue-engineered auricular reconstruction are (FDA approved) polyglycolic acid (PGA) and polylactic 1655472 acid (PLA) [4,8,9], polymers typically used together due to the cell compatibility of the former and the maintenance of strength over time of the latter. Despite their frequent use, however, these materials have been noted to incite unwanted inflammatory reactions [2,3], attributed by some to the products of PLA degradation [6,7]. In addition, high-density porous polyethylene (HDPP) scaffolds, while biocompatible and often used clinically for reconstructive purposes in other anatomic regions, are quite rigid unlike auricular native cartilage [3] and associated with increased rates of infection and extrusion [10], thus resulting in suboptimal reconstructions. Synthetic (i.e., poloxamer) and naturally derived hydrogels (i.e., alginate, agarose, or fibrin) have similarly been evaluated as substrates for auricular tissue-engineered scaffolds as they are easily molded, potentially injectable, and “provide a hospitable three-dimensional support matrix” for cells contained within [3]. While biodegradable and used clinically, fibrin hydrogels are limited by their low tensile strength and poor surgical handling and are thus most often used as a coating for other, lessbiocompatible materials to increase their cellular compatibility [4,11]. Like fibrin, the extracellular matrix component collagen is abundant, biocompatible, and can be used in hydrogel form [12]. Indeed, collagen hydrogels have been utilized previously for cartilage tissue engineering applications, albeit with mixed results including the inability to independently maintain original cast dimensions without the use of an internal support [12,13]. With the recent explosion of digital technology, computerassisted design/computer-assisted manufacturing (CAD/CAM) techniques have emerged as a viable means of fabricating specific three-dimensional structures based upon virtual images. Despite the immense potential CAD/CAM approaches offer the field of tissue-engineered microtia reconstruction, few groups have effectively applied this technology towards auricular scaffold fabrication [7,14]. Furthermore, digital acquisition of three-dimensional data has commonly relied on modalities such as computed tomography [7], which is expensive and imparts harmful ionizing radiation.We therefore sought to combine digital photogrammetry with CAD/CAM techniques to develop high-density collagen type I hydrogel scaffolds and their respective molds that would precisely mimic the normal anatomy of the patient-specific external ear as well as recapitulate the complex biomechanical properties of native auricular elastic cartilage while avoiding the morbidity of traditional autologous reconstructions.Methods Ethics StatementAll animal care and experimental procedures were in compliance with the Guide for the Care and Use of Laboratory Animals [15] and were approved by the Weill Cornell Medical College Institutional Animal Care and Use Committee (protocol # 20110036). All efforts were made to minimize suffering.Isolation of chondr.
