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An ideal bone scaffold should possess the following characteristics : biocompatibility ; suitable surface for cell attachment , proliferation and differentiation ; highly porous with an interconnected pore network for cell ingrowth and transport of nutrients and metabolic waste ; mechanical properties to match the requirements of the surrounding tissues to reduce or eliminate stress shielding , and to meet anatomic loading requirements to avoid mechanical failure .
 biomedical: bone scaffold; machanical property: biocompatibility; concept or principle: surface; engineering feature: cell attachment; machanical property: porous; machanical property: pore; concept or principle: cell ingrowth; process characterization: transport; concept or principle: metabolic waste; concept or principle: mechanical properties; machanical property: stress shielding; machanical property: mechanical failure
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 biomedical: bone scaffold; machanical property: biocompatibility; concept or principle: surface; engineering feature: cell attachment; machanical property: porous; machanical property: pore; concept or principle: cell ingrowth; process characterization: transport; concept or principle: metabolic waste; concept or principle: mechanical properties; machanical property: stress shielding; machanical property: mechanical failure