This study investigates a poly(epsilon-caprolactone)-graft-type II collagen-graft-chondroitin sulfate (PCL-g-COL-g-CS) biomaterial as a scaffold for cartilage tissue engineering. Biodegradable polyester, PCL, was utilized to fabricate three-dimensional (3D) porous scaffolds by particulate leaching. The PCL scaffold was then surface modified by chemical bonding of 1,6-hexanediamine and the grafting of a bioactive polymer layer of COL and CS with the help of 1-ethyl-3-(3-dimethyl- aminopropyl) carbodiimide (EDC)/N-hydroxysuccinimide (NHS) on the modified PCL surface to produce PCL-g-COL and PCL-g-COL-g-CS, respectively. The characteristics of these modified and grafted matrices were examined by ESCA, aminolysis, collagen and CS assay, porosity and water-binding capacity. Grafted COL and CS markedly increased water-binding capacity, and promoted the spreading and growth of chondrocytes. During a 4-week culture period, PCL-g-COL and PCL-g-COL-g-CS matrices both provided more cell proliferation, as determined by measuring the DNA assay. Additionally, a larger amount of secreted collagen and glycosaminoglycans (GAGs) appeared in the PCL-g-COL-g-CS matrices than in the control (PCL) as indicated by the histochemical sections via Hematoxylin and eosin (H&E) stain, Masson trichrome stain and Safranin-O stain. The chondrocytes were induced to function normally; the cell phenotype was maintained, and the GAGs and collagen in the PCL-g-COL-g-CS scaffold were secreted in vitro. These results serve as a basis for future studies of the fabrication process and reveal the potential biocompatibility of the biomimetic matrix for regenerating articular cartilage or other organs.

A digital background calibration technique is proposed to correct gain errors in pipelined analog-to-digital converters (ADCs). The calibration technique performs the error estimation and the adaptive error correction based on the concept of split ADCs. With the 1-or 1.5-bit realization in pipelined stages, capacitor-mismatch errors can be merged with gain errors, and the proposed calibration technique can be utilized. Behavioral simulations show that the signal-to-noise-and-distortion ratio of a 12-bit pipelined ADC with an 8-bit gain accuracy and the capacitor mismatch σ = 0.125% can be improved from 56.4 to 73.8 dB. The calibration process converges in approximately 200 000 cycles.Index Terms-Adaptive systems, analog-to-digital conversion, digital background calibration, pipelined analog-to-digital converters (ADCs).

No abstract

No abstract

No abstract