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We describe the synthesis of end-functionalized polystyrenes by living anionic polymerization in a microstructured reactor via termination by acetal-protected functional epoxides. Initiation of styrene polymerization by alkyllithium takes place in a micromixing device with efficient heat and mass transfer properties. A newly developed continuous polymerization-termination sequence enabled quantitative functionalization of the living carbanions by nucleophilic displacement with different, specifically designed glycidyl ethers (ethoxy ethyl glycidyl ether (EEGE), 1,2-isopropylidene glyceryl glycidyl ether (IGG), and trans-2-phenyl-1,3-dioxane glycidyl ether (PDGE)). Upon acidic hydrolysis the end-capped polystyrenes release multiple hydroxyl groups (2-3) at the chain end. Temperature and flow rates have been varied to control molecular weights and to optimize the reaction conditions for maximum polymerization and termination efficiency. The polymers were analyzed in detail using NMR spectroscopy, size exclusion chromatography (SEC), and MALDI-ToF-MS. Molecular weights of the samples prepared ranged between 1800 and 9000 g/mol. For all of the novel termination agents full termination was confirmed by MALDI-ToF MS. The approach presented is applicable for a large variety of monomers that are polymerizable by carbanionic polymerization.
The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation, since it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were a-TCP, and four materials which were created from ß-Rhenanite and its derivatives: R1-ß-Rhenanite (CaNaPO4); R1/M2 composed of CaNaPO4 and MgNaPO4; R1+SiO2 composed of CaNaPO4 and 9% SiO2 (wt%); and R17-Ca2KNa(PO4)2. HBDC were grown on the substrata for 3, 5, 7, 14 and 21 days, counted and probed for various mRNAs and proteins (Type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrata supported continuous cellular growth for 21 days. At day 21, surfaces of R1+SiO2 and R17 had the highest number of HBDC. At 14 and 21 days, cells on R1 and on R1+SiO2 displayed significantly enhanced expression of all osteogenic proteins. Since all novel calcium phosphates supported cellular proliferation together with expression of bone-related proteins at least as much as TCP, these ceramics can be regarded as potential bone substitutes. R1 and R1+SiO2 had the most effect on osteoblastic differentiation, thus suggesting that these materials may possess a higher potency to enhance osteogenesis than TCP.
Calcium phosphate coated titanium and titanium alloy are widely used as dental and orthopaedic implants. This study examines the effect of novel calcium titanium and calcium titanium zirconium phosphates suitable for plasma-spraying onto titanium substrata on the expression of bone-related genes and proteins by human bone-derived cells (HBDC) and compares this behavior to that on native titanium and hydroxyapatite-coated titanium. Test materials were an acid etched and sand-blasted titanium surface (Ti-DPS), a plasma-sprayed hydroxyapatite coating (HA), and five materials which were created from CaTi4(PO4)6 (CTP) and CaZr4(PO4)6 (CZP): sintered CaTi4(PO4)6 (CTP-S1), sintered 46CaO·23TiO2·31P2O5 (CTP-S2), sintered CaTiZr3(PO4)6, (CTZP-S1), sintered 46CaO·23ZrO2·31P2O5 (CTZP-S2) and sintered 55CaO·20TiO2·31P2O5 (CTP-S3). HBDC were grown on the substrata for 3, 7, 14 and 21 d, counted and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase and bone sialoprotein). All substrates significantly affected cellular growth and the temporal expression of an array of bone-related genes and proteins. At 14 and 21 d, cells on CTP-S3 displayed significantly enhanced expression of all osteogenic mRNAs. Surfaces of CTP-S1 and CTP-S3 had the most effect on osteoblastic differentiation inducing a greater expression of an array of osteogenic markers than recorded for cells grown on Ti-DPS and HA, suggesting that these novel materials may possess a higher potency to enhance osteogenesis.
The use of biodegradable bone substitutes is advantageous for alveolar ridge augmentation because it avoids second-site surgery for autograft harvesting. This study examines the effect of novel, rapidly resorbable calcium phosphates and a calcium phosphate bone cement on the expression of bone-related genes and proteins by human bone-derived cells (HBDCs) and compares this behavior to that of tricalciumphosphate (TCP). Test materials were -TCP, two materials with a crystalline phase Ca2KNa(PO4)2 and with a small amorphous portion containing either magnesium potassium phosphate (material denominated GB14) or silica phosphate (material denominated GB9), and a calcium phosphate bone cement (material denominated Biocement D). HBDCs were grown on the substrata for 3, 7, 14, and 21 days, counted, and probed for various mRNAs and proteins (type I collagen, osteocalcin, osteopontin, osteonectin, alkaline phosphatase, and bone sialoprotein). All substrates supported continuous cellular growth for 21 days. In the presence of GB14 and Biocement D specimens cell proliferation was reduced and cell differentiation increased. At day 21, the greatest number of cells was found on GB9 expressing significantly higher levels of bone-related proteins than cells grown on all other surfaces. Because all novel materials facilitated the expression of the osteoblastic phenotype at least as much as TCP and the polystyrene control, these biomaterials can be regarded as excellent candidate bone substitute materials. GB9 induced the highest proliferation and cellular differentiation after 21 days of incubation, suggesting that this material may possess a higher potency for enhancing osteogenesis than TCP. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 69A: 145-154, 2004