Abstract
The objective of the present study is to demonstrate the versatility of the digital light processing (DLP) technique particularly when using a freeze-cast ceramic layer as the feedstock, which can manufacture porous calcium phosphate (CaP) scaffolds with arbitrarily designed macroporous structures with tailored microporous frameworks specially designed for bone scaffold applications. For this goal, we employed camphene-camphor as the freezing vehicle and porogen for the preparation of photocurable CaP suspensions containing diurethane dimethacrylate (UDMA) monomers. After freeze-casting, the CaP suspensions could be solidified at controlled temperatures (~33–38 °C) and then be photopolymerized by DLP. All produced CaP scaffolds fairly resembled the designed macroporous structures (the gyroid structure with two interpenetrating macropore networks). In addition, numerous micropores were created in the CaP filaments, while the microporosity increased with increasing the camphene-camphor amount from 40 vol % to 60 vol %. As a consequence, compressive strength and modulus of hierarchically porous CaP scaffolds decreased due to an increase in overall porosity. However, reasonable mechanical properties could be obtained at high porosities owing to the CaP frameworks constructed in a periodic manner. In addition, excellent water penetration capability, biocompatibility, and apatite-forming ability were obtained, which were attributed to the microporous CaP frameworks with good pore interconnectivity and large surface area.
Highlights
Calcium phosphate (CaP) ceramics have been extensively used as bioactive materials for bone substitute applications [1,2,3]
Reasonable mechanical properties could be obtained at high porosities owing to the calcium phosphate (CaP) frameworks constructed in a periodic manner
Porous calcium phosphate (CaP) scaffolds can facilitate bone ingrowth into pores, accelerating bone regeneration when implanted into bone defect areas [4]
Summary
Calcium phosphate (CaP) ceramics have been extensively used as bioactive materials for bone substitute applications [1,2,3]. Porous calcium phosphate (CaP) scaffolds can facilitate bone ingrowth into pores, accelerating bone regeneration when implanted into bone defect areas [4]. These porous materials should possess proper mechanical strengths that can withstand applied loads during bone regeneration. The higher porosity required for faster bone regeneration inevitably causes a severe reduction in mechanical strength [5]. This tradeoff relationship is one of the most critical hurdles for the designing of new types of porous ceramic scaffolds [6]. Considerable attention has been paid to mimic the hierarchically porous structure of bones [5,6,7,8,9] in order to offer large surface areas and favorable paths for angiogenesis for new bone formation while providing reasonable mechanical properties [10,11,12,13,14]
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