title: Porous silicon confers bioactivity to polycaprolactone composites in vitro.
abstract: Silicon is an essential element for healthy bone development and supplementation with its bioavailable form (silicic acid) leads to enhancement of osteogenesis both in vivo and in vitro. Porous silicon (pSi) is a novel material with emerging applications in opto-electronics and drug delivery which dissolves to yield silicic acid as the sole degradation product, allowing the specific importance of soluble silicates for biomaterials to be investigated in isolation without the elution of other ionic species. Using polycaprolactone as a bioresorbable carrier for porous silicon microparticles, we found that composites containing pSi yielded more than twice the amount of bioavailable silicic acid than composites containing the same mass of 45S5 Bioglass. When incubated in a simulated body fluid, the addition of pSi to polycaprolactone significantly increased the deposition of calcium phosphate. Interestingly, the apatites formed had a Ca:P ratio directly proportional to the silicic acid concentration, indicating that silicon-substituted hydroxyapatites were being spontaneously formed as a first order reaction. Primary human osteoblasts cultured on the surface of the composite exhibited peak alkaline phosphatase activity at day 14, with a proportional relationship between pSi content and both osteoblast proliferation and collagen production over 4 weeks. Culturing the composite with J744A.1 murine macrophages demonstrated that porous silicon does not elicit an immune response and may even inhibit it. Porous silicon may therefore be an important next generation biomaterial with unique properties for applications in orthopaedic tissue engineering.
authors.affiliation: Institute for Science and Technology in Medicine, Keele University, Stoke-on-Trent, ST4 7QB, UK, j.r.henstock@keele.ac.uk.
authors.forename: J R
authors.initials: JR
authors.lastname: Henstock
authors.forename: U R
authors.initials: UR
authors.lastname: Ruktanonchai
authors.forename: L T
authors.initials: LT
authors.lastname: Canham
authors.forename: S I
authors.initials: SI
authors.lastname: Anderson
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001696:Biomechanical Phenomena; D018786:Bone Substitutes / Q000737:chemistry; D002130:Calcium Phosphates / Q000378:metabolism; D002460:Cell Line; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D006801:Humans; D008262:Macrophage Activation / Q000187:drug effects; D008422:Materials Testing; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011091:Polyesters / Q000737:chemistry*; D016062:Porosity; D012824:Silicic Acid / Q000008:administration & dosage; D012825:Silicon / Q000008:administration & dosage* / Q000737:chemistry* / Q000633:toxicity; D023822:Tissue Engineering
chemical_list: D001672:Biocompatible Materials; D018786:Bone Substitutes; D002130:Calcium Phosphates; D011091:Polyesters; D012824:Silicic Acid; C016240:polycaprolactone; C020243:calcium phosphate; D000469:Alkaline Phosphatase; D012825:Silicon