Affinity of Osteoblasts on Bone Cements Incorporated with Amino Groups / 대한정형외과학회잡지

Biomaterial surfaces can be characterized by their chemical, morphologic, and electrical surface features. The adhesion and proliferation of different types of mammarian cells on various surfaces depends on polymer surface characteristics like water wettability and charge. In clinical aspect, bone to bone cement interface loosening has been one of the causes of failure of the prosthetic implantation. In this study, the bone cement was, thus, modified by mixing a monomer with amino group, which is a positively charged chemical group, to improve cellular adhesion and proliferation and to decrease bone to bone cement interface loosening. To incorporate amino-charged groups in the bone cement, we used dimethylaminoethyl- metacrylate (DAEMA) as a adding material. As experimental materials, CMW1 bone cement (control) and CMW1 mixed with monomer containing 1mol% dimethylaminoethylmetacrylate (DMA1) and CMW1 mixed with monomer containing 3mo1% dimethylaminoethylmetacrylate (DMA3) were used. To estimate the wettability of surface of bone cement, water contact angle was measured using contact angle goniometer and water absorption was measured using the disc samples. Osteoblasts were isolated from neonatal, Spraque-Dawley rat calvaria. After 3 culturing passages, the osteoblasts were plated on the cement disks, which are placed in a 24-well tissue-culture plate, at a density of 1 X 10 (5) cells/cm. After culturing for 2, 6, 24, and 48 hours, the number of attached cells on each cement discs were counted and cell morphologies were examined with scanning electron microscope (SEM). No significant difference in the water contact angle (63-64degrees) is statistically found between 3 groups (P>0.05). The water absorbencies of DMA1 (3.61+/-0.28%) and DMA3 (6.70+/-0.56%) were higher than that of the control (2.59+/-0.21%). Diametral tensile strength were decreased at DMA1 and DMA3 groups in comparing with control and that of DMA3 was smallest (P0.05) at each culturing period. In summary, well spread osteoblasts and increased attachment and growth of them were observed, when they were plated on the amino-charged cement discs. The histocompatibility of the amino-charged cements may increase the attachment between bone and cement. However, mechanical strength may decrease due to higher water absorbency. The author will further study to find the material that is cytocompatible and that does not lead to deteriorate mechanical properties.

Interaction of pyridoxal phosphate with the amino groups at the active site of 5-aminolevulinic acid dehydratase in maize.

Pyridoxal 5'-phosphate strongly and reversibly inhibited maize leaf 5-amino levulinic acid dehydratase. The inhibition was linearly competitive with respect to the substrate 5-aminolevulinic acid at pH values between 7 to 9·0. Pyridoxal was also effective as an inhibitor of the enzyme but pyridoxamine phosphate was not inhibitory. The results suggest that pyridoxal 5'-phosphate may be interacting with the enzyme either close to or at the 5- aminolevulinic acid binding site. This conclusion was further corroborated by the detection of a Schiff base between the enzyme and the substrate, 5-aminolevulinic acid and by reduction of pyridoxal phosphate and substrate complexes with sodium borohydride.