Hyung-k Seo

In vitro and in vivo evaluations of 3D porous TCP-coated and non-coated alumina scaffolds.

Both tricalcium phosphate (TCP) and alumina have been extensively studied and shown to have high biocompatibility. Tricalcium phosphate has improved biodegradability and a higher solubility than hydroxyapatite. In contrast, alumina (Al2O3) is almost completely inert at physiological conditions and has been used as a biomaterial due to its wear resistance, high surface finish, and excellent hardness. Thus, the combination of these two implants would result in greater biocompatibility and phenotype maintenance. A polyurethane (PU) foam replica method was employed in this study to coat TCP on an alumina scaffold. The TCP-coated alumina scaffold was then sintered to generate a porous surface morphology. The pore sizes obtained using this approach ranged between 100—600 µm, which is ideal for cellular proliferation. The cytotoxicity, cellular proliferation, differentiation, and ECM deposition on the coated scaffold resulted in longer-term viability of osteogenic markers compared to the non-coated scaffold. Moreover, the osteogenic properties of porous TCP-coated Al2O3 scaffolds were reported in this study using rabbit models. The TCP/Al2O 3 scaffold and control Al2O3 scaffolds were implanted in the rabbit femur. The bone tissue response was analyzed with micro-computed tomography (micro CT) at 12 and 24 weeks after implantation. The porous scaffolds exhibited favorable hard and soft tissue responses at both time points. At 24 weeks, a three-fold increase in bone tissue ingrowth was observed in defects containing TCP-coated Al2O3 scaffolds compared to control Al2O3 scaffolds.

In vitro and in vivo evaluation of a macro porous β-TCP granule-shaped bone substitute fabricated by the fibrous monolithic process

In this study, a new porous beta-tricalcium phosphate (β-TCP) granule was fabricated using the fibrous monolithic (FM) process and its in vitro biocompatibility and in vivo bone formation were evaluated. SEM micrograph images showed that MG-63 cells attached to the surfaces of the implant and were well proliferated. Cellular viability was as high as 75% in a50% extract dilution solution. cDNA micro array analysis was also carried out. In this analysis, we found a total of 12 up-regulated and 25 down-regulated genes. Four rabbits were used in the in vivo experiments. 3D micro-CT images showed that the formation of new bone was almost three times greater than that of normal trabecular bone (BV/TV). The histomorphometric results correlated with the micro-CT findings; a greater amount of new bone formation and osteoblast lineage along with osteocytes were observed in the implanted animals. Also x-ray radiographic and 2D micro-CT images were taken to demonstrate the superior biodegradability of the porous granule. As biodegradation occurred along with bone formation, 6 months after implantation, the porous granule structure was not distinguishable separately from that of the trabecular bone.

PCL Infiltration into a BCP Scaffold Strut to Improve the Mechanical Strength while Retaining Other Properties

A highly porous Biphasic Calcium Phosphate (BCP) scaffold was fabricated by the sponge replica method with a microwave sintering technique. The BCP scaffold had interconnected pores ranging from 80 μm to 1000 μm, which were similar to natural cancellous bone. To enhance the mechanical properties of the porous scaffold, infiltration of polycaprolactone (PCL) was employed. The microstructure of the BCP scaffold was optimized using various volume percentages of polymethylmethacrylate (PMMA) for the infiltration process. PCL successfully infiltrated into the hollow space of the strut formed after the removal of the polymer sponge throughout the degassing and high pressure steps. The microstructure and material properties of the BCP scaffold (i.e., pore size, morphology of infiltrated and coated PCL, compressive strength, and porosity) were evaluated. When a 30 vol% of PMMA was used, the PCL-BCP scaffold showed the highest compressive strength. The compressive strength values of the BCP and PCL-BCP scaffolds were approximately 1.3 and 2MPa, respectively. After the PCL infiltration process, the porosity of the PCL-BCP scaffold decreased slightly to 86%, whereas that of the BCP scaffold was 86%. The number of pores in the 10 μm to 20 μm rage, which represent the pore channel inside of the strut, significantly decreased. The in-vitro study confirmed that the PCL-infiltrated BCP scaffold showed comparable cell viability without any cytotoxic behavior.

An efficient approach to understanding social evolution of location-focused online communities in location-based services

The booming and novel emerging promising technologies on ubiquitous computing, GPS positioning, are facilitating the development of location-based services (LBSs). Particularly, understanding the dynamic topological structures of mobile users in LBSs who visit the same physical locations has many meaningful applications including friend recommendation, location-sensitive items recommendation, and privacy management. In this paper, we proposed a novel m-triadic concept-based approach for uncovering the social evolution of location-focused online communities in LBSs. Firstly, an m-triadic concept-based location-focused online communities detection approach is presented. Further, the social evolution of the community is characterized by the time series triadic concepts in which the objectives contain the targeted users.

Mobile cloud services recommendation: a soft set-based approach

Mobile Internet and Cloud Computing technologies facilitate the rapid development of mobile cloud services. Particularly, mobile cloud services recommendation has become increasingly important as services become increasingly prevalent over the Internet. Existing recommendation mechanisms mainly focus on Quality of Services (QoS). However, the continuous emerging of many mobile cloud services leads to a server issue on the information overload for users. Hence, how to recommend the suitable mobile cloud services to users for addressing this issue is important. To this end, this paper incorporates the unique property of soft set and creatively investigated the soft set-based mobile cloud service recommendation mechanism and then devised the corresponding recommendation algorithm.

Effect of Strontium Doped Porous BCP as Bone Graft Substitutes on Osteoblast

In this study, we investigated primary biocompatibility and osteogenic gene expression of porous granular BCP bone substitutes with or without strontium (Sr) doping. In vitro biocompatibility was investigated on fibroblasts like L929 cells and osteoblasts like MG-63 cells using a cell viability assay (MTT) and one cell morphological observation by SEM, respectively. MTT results showed a cell viability percent of L929 fibroblasts, which was higher in Sr-BCP granules (98-101%) than in the non-doped granules (92-96%, p

Similarity Evalution between Graphs: A Formal Concept Analysis Approach

Many real-world applications information are organized and represented with graph structure which is often used for representing various ubiquitous networks, such as World Wide Web, social networks, and proteinprotein interactive networks. In particular, similarity evaluation between graphs is a challenging issue in many fields such as graph searching, pattern discovery, neuroscience, chemical compounds exploration and so forth. There exist some algorithms which are based on vertices or edges properties, are proposed for addressing this issue. However, these algorithms do not take both vertices and edges similarities into account. Towards this end, this paper pioneers a novel approach for similarity evaluation between graphs based on formal concept analysis. The feature of this approach is able to characterize the relationships between nodes and further reveal the similarity between graphs. Therefore, the highlight of our approach is to take vertices and edges into account simultaneously. The proposed algorithm is evaluated using a case study for validating the effectiveness of the proposed approach on detecting and measuring the similarity between graphs.