Key Engineering Materials Vols. 288-289

Abstract: Microchannel array chips modified by metal deposition or polymer coating were contacted with blood. Titanium (Ti), chromium (Cr) and gold (Au) films were deposited onto the microchannel array chips. Albumin (Alb) and MPC polymer (MPC) were coated onto other chips. Non-treated Si chips were used as a control. Whole blood was collected with 1000 units/ml heparin solution from young healthy volunteers. The passing time of a 100 µl portion of human whole blood through these channels was measured under a pressure difference of 20 cm H2O. Simultaneously, the flow behavior of blood cells in channel was observed by an optical microscope and recorded by a video recorder. Platelet adhesion was observed on Si, Ti, Cr, and especially on Au. The blood pass-through time (BPT) increased in order of Ti, Si, Cr and Au. On the Alb- and MPC-coated chips, platelets were seldom observed and the BPTs were short in comparison with the metal chips. From these consequences, platelet adhesion depended on the materials. The BPT correlated well to the number of adherent platelets on the materials. Therefore, the blood coagulation reaction originated in platelet activation could be detected using microchannel array. We concluded that this method could be applied to evaluate initial blood compatibility of materials within several minutes in vitro.

Abstract: Fibrosis caused by the host response to long-term transplanted microcapsules and the limitation of traditional L929 cell model for biocompatibility testing inspire the development of an assay of biocompatibility based on macrophage behavior. In this paper, the human monocytic cell line THP-1 was utilized for biocompatibility evaluation of microcapsule materials. The cell viability and secretion of nitric oxide (NO) and cytokines served as index of biocompatibility were assayed. It was found that the evaluated microcapsule materials had no effect on the stimulation of NO and cytokines secretion, which meant that these materials were biocompatible. Furthermore, it suggests the THP-1 cell a convenient in vitro experimental model that might be useful for long-term predictions of material biocompatibility.

Abstract: In this study, a computer-assisted cell tracking system including an automatic image processing program for rapid and precise analysis of cell migration in various conditions was self-designed and L-929 cell migration on the glass coated with type I collagen was examined using this cell tracking system. Furthermore, computer-based image processing software, with the capture program to choose the capture interval and period, and analysis techniques were developed for quantitative analysis of the cell migration on extracellular matrices. The results showed that the migration speed of L-929 cells on the collagen-coated glass was significantly (p < 0.05) increased compared to the non-coated control. On the morphological observations, it was showed that the cells on the collagen-coated glass looked much healthier than those on the control. These results suggested that this cell tracking system would provide tools for the analysis of cell migration in various in vitro conditions and might be effective enough to evaluate various biological events including embryonic development as well as physiological and pathological tissue reorganization.

Abstract: To evaluate the biocompatibility of biomedical materials for hepatic tissue engineering, another new method was introduced to observe hepatocytes functions. In this experiment, hepatocytes were seeded onto four kinds of membranes of PLLA, PLGA (90:10), PLGA (75:25), and Chitosan cross-linked with collagen. The culture mediums were collected at 21 day after seeding, and then albumin (Alb), Urea (UN), glucose (Glu), total protein (TP), and triglyceride (TG) in the supernatant were detected by automatic biochemical analyzer. Results showed that hepatocytes on film of Chitosan cross-linked with collagen exhibited the highest level of TP and TG. These results were highly corresponding with the results of morphological observation. This data indicated that analyzing TP and TG in culture medium by automatic biochemical analyzer might be applied to evaluate hepatocytes biocompatibility on materials as a convenient and feasible method.

Abstract: Platelet adhesion and activation restrict the clinical applicability of blood-contacting biomaterial because platelet-biomaterial interaction can result in the formation of a haemostatic plug or thrombus. In this study we used LDH (lactate dehydrogenase) tests to evaluate the adsorption behavior of platelets on material surfaces. Enzyme immunoassay (EIA) was applied to evaluate platelet activation using a special monoclonal antibody directly binding to the Pselectin on the activated platelet membrane. The results show compared with the conventional detecting tools of platelet adhesion / activation such as optical microscopy. LDH (lactate dehydrogenase) testing and EIA (enzyme immunoassay) are surface-sensitive methods for the investigation of various aspects of platelet adsorption and activation on different biomaterials.

Abstract: Porous sheets of hydroxyapatite (Ca10(PO)4(OH)2; HA) with about 50 µm to 1 mm in thickness and porous HA granules of about 50 µm to 1 mm in size with tailored crystal surface were prepared by the hydrothermal vapor exposure method at the temperatures above 105 °C under saturated vapor pressure of pure water. Porous HA sheets with about 75 % porosity prepared at 120 °C were composed of rod-shaped crystals of about 30 µm in length. Porous HA granules prepared at 160 °C were also composed of rod-shaped crystals of about 20 µm in length with the mean aspect ratio of 30. These crystals were elongated along the c-axis. Rod-shaped HA crystals were locked together to make micro-pores of about 0.1 µm in size. Both of materials were nonstoichiometric HA with calcium deficient composition. These materials must have the advantage of adsorptive activity, because they had large specific crystal surface and much micro-pores.

Abstract: Single crystals of AB-type carbonate apatite were grown by a CaCO3-Na2CO3 flux method under high pressure of Ar gas. The crystals obtained were hexagonal prismatic elongated along the c-axis with the length of 2mm and the diameter of 0.3mm at a maximum. Chemical formula was Ca8.8Na1.2[(PO4)4.8(CO3)1.2]CO3 and the space group was hexagonal P6 with cell parameters a = 0.9379(2)nm, c = 0.6935(1)nm. The detailed crystal structure determined with a reliability factor Rw = 0.047 indicated that the triangular plane of carbonate ion occupying B-site was slanted off the crystallographic mirror plane and the angle of the carbonate triangle with the mirror plane varied depending on Na-substitution of adjacent Ca sites whilst the A-site carbonate ion was parallel to the c-axis.

Abstract: Microwave processing of porous hydroxyapatite ceramics was investigated in a dual frequency microwave-sintering furnace. The results revealed that microwave-sintering process could get sintered ceramics at much shorter sintering time and at lower sintering temperature than that of the conventionally heat-sintering process. Further, the microwave-sintered samples showed much smaller grain size and more uniform microstructure and reached a comparable compressive strength. The mechanism of rapid heating behavior of hydroxyapatite ceramics in microwave was also discussed. The results revealed that microwave processing was a promising method for sintering porous hydroxyapatite ceramics.