Papers by Author: P. Li

Abstract: A portable three-dimensional vision coordinate measuring system is proposed in this paper. It consists of a light pen, a CCD camera and a laptop computer. The light pen is a hand-held probe with three point light sources using LEDs and a spherical touch stylus arranged in one line. The CCD camera takes the image of LEDs on the light pen and the 3D coordinates of measured point at the center of touch stylus are obtained by computing the positions of LEDs in the image when the probe contacts the object surface. The equations of the vision measurement system are derived by using perspective of three collinear points and spatial analytic geometry. The measuring device can be set up easily on an industrial site and the measurement is convenient. The object surface can be simple, complex, or hidden from the view of camera. The effectiveness of the mathematical model and validity of the measuring system are confirmed by experiments.

Abstract: We report a study involving chitosan chains immobilized on poly (ethylene terephthalate) (PET) films by plasma and ultraviolet (UV) grafting modification. The surface structure of the modified PET is determined by means of attenuated total reflection Fourier transform infraed spectroscopy (ATR-FTIR) and X-ray photoelectron spectroscopy (XPS). The results show that the chains of chitosan are successfully grafted on the surface of PET. Platelet adhesion evaluation in vitro is conducted to examine the blood compatibility in vitro. Scanning electron microscopy (SEM) and optical microscopy reveal that the amounts of adhered, aggregated and morphologically changed platelets are reduced on the chitosan-immobilized PET films. The number of platelet adhered on the modified film is reduced by almost 48% compared to the amount of platelets on the untreated film. Our result thus shows that chitosan immobilized on the PET surface improves blood compatibility.

Abstract: The purpose of this study was to evaluate the response of osteoblasts to calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. A ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One third of the ceramics was used to form bone-like apatite (BLA), and the surface of another one third was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate whether the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in multi-layers and attached to the surface and proliferated well in the collagen and HA/TCP group. In the untreated and BLA precipitated groups, cells did not attach to the surface well. Osteoinduction was good in the BLA precipitated group and the amount of bone formed was higher; in the untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.

Abstract: The purpose of this study was to evaluate the response of osteoblasts to the calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. The ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One thirds of the ceramics were formed bone-like apatite (BLA), and the surface of another one thirds was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate if the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in multi-layers and well attached to the surface and proliferated well in the group of collagen and HA/TCP. In untreated and BLA precipitated group, cells did not attach to the surface well. Osteoinduction was good in BLA precipitated group and the amount of bone formed was higher; in untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.