Papers by Author: Chun Ho Kim

Abstract: In this study, we developed the porous alginate (AL) scaffolds with modified pores size and distributions to actively control tissue regeneration. An addition of 5 and 10% (v/v) butanol to AL solution was effective to control pores structures of AL scaffolds. Especially, increased amount of butanol induced that proportion of smaller pores (size of around 5~10 μm) on AL scaffolds increased. Using swelling kinetics analysis, we confirmed that micro pore modified AL scaffolds show faster swelling rate than pristine scaffolds. During in vitro study, the enhanced viability and proliferation of human dermal fibroblasts (HDFs) were observed by the pore size and distribution from micro pore modified AL scaffolds. However, AL scaffolds added 10 % butanol with excessive proportion of smaller pores induced the decreased viability of HDFs for 7 days. From our results, AL scaffolds with modified pores structures represent a potential implants to control biological in vitro and in vivo functions in a variety of tissue engineering.

Abstract: Chitosan and gelatin has attracted considerable interest owing to its advantageous biological properties such as excellent biocompatibility, biodegradation, and non-toxic properties. In this paper, we investigated the potential of chitosan/gelatin (Chi-Gel) nanofibers mat with enhanced cell viability for use as cell culture scaffolds. The surface morphology, mechanical properties, and initial contact angle analysis of Chi-Gel nanofibers mat were evaluated. The proliferation of human dermal fibroblast cell (HDFs) on Chi-Gel nanofibers mat was found to be approximately 20% higher than the pure chitosan nanofibers mat after 7 days of culture. These results suggest that the Chi-Gel nanofibers mat has great potential for use tissue engineering applications.

Abstract: The emulsion stabilizing potential of chitosans was compared in the presence of organic additives. The 4 types suspension of 0.1 wt% of chitosan flocculant were obtained by mixing of chitosan colloidal dispersion with three kinds of additives; sorbic acid, benzoic acid and dibutylhydroxytoluene (BHT). The viscosity of emulsion revealed the following order of stabilizing potentials; sorbic acid > benzoic acid > BHT. As a bio-adsorbent for the treatment of biomedical wastewater, the results were capable of adsorbing more than 30% of pure chitosan. The chitosan emulsions represented that the removal efficiency were increased by COD 59.2%, BOD 70.1%, Zn 77.1%, Cu 93.7%, E. coli 99.4%. As a result of this investigation, it is remarked that the high stabilizing potential of chitosan solution is explained by higher adsorption efficiency with organics, heavy metals and microorganism, and that the effectiveness of chitosan solution for coagulating biomedical wastewater suspension could be improved due to stabilization of the viscosity in the presence of organic additives.

Abstract: The porous neutralized chitosan scaffold (NCS) was prepared by freeze-dry method. Its poor cell binding capacity was improved approximately five folds by mixing or coating of atelomeric type I collagen. In order to recreate wound-healing microenvironment within the NCS for the better wound healing effect, various concentrations of bFGF and fibronectin (FN) were supplied in the secondary freeze-dry process of the scaffold. NCS+ bFGF and NCS+FN improved the cell binding capacity by four folds and three folds respectively. Therefore supplementation of collagen, b-FGF and/or fibronectin in the NCS can improve the biocompatibility of the chitosanbased scaffold which itself revealed poor cell binding capacity.

Abstract: We have developed tensile and porous neutralized chitosan scaffold (NCS) whose pore size was controlled by freezing temperatures. At -70 oC, mean pore size of 112 μm was obtained. At -196 oC, mean pore size was approximately 70 μm at surface. The scaffold processed at -196 oC showed homogeneous small pores with structural integrity, which may be more useful as a guidance dermal scaffold for inward cell migration. The scaffold processed at –70 oC may be more useful for cell loading scaffold requiring wider pore. Since biodegradability and biocompatibility are crucial parameters for the development of dermal scaffold, we evaluated the rate of NCS degradation in the culture medium containing lysozyme by measuring weight loss as well as mean molecular weight of the scaffold. Approximately 40% weight loss at one week and 70% weight loss at 30 days was observed, which means that 70% of the scaffold will be degraded and releasable if the wound microenvironment is similar to the test condition. Again, mean molecular weight of the scaffold based on gel permeation chromatography was less than 1x105 after 10 day incubation. This result suggests that degradation of the NCS begins earlier than the observation of gross weight loss. We also evaluated whether degradation product of NCS are toxic to the human dermal fibroblast or not. Chitosan oligomer up to 1.0 mg/ml, which corresponds to 10% of the total degradation derivatives of the NCS, did not affect the viability of the dermal fibroblast based on MTT assay. This result along with the biodegradation data suggests that the NCS can be developed as suitable dermal scaffold.

Abstract: This study is to develop a novel method for preparation of the chitosan scaffold having interconnected open pore structure and controlled pore distribution. For this, the effects of addition of non-solvent on chitosan solution were estimated. The porous scaffolds were typically prepared by solid-liquid separation and subsequent sublimation of solvent. Alcohol was used as non-solvent for chitosan. The difference of freezing temperature of each of the components induced the liquidliquid and the liquid-solid phase separation via demixing solution (solvent/non-solvent/chitosan). The morphology, heterogeneous pore distribution and mechanical properties of the scaffolds were examined. The addition of non-solvent in chitosan solution was to make the controlled homogeneous micropores and improved interconnectivity between pores without any surface skin layer. For control chitosan scaffold, the pore size was mainly about 80~100 μm. On the contrary, Pore diameters could be controlled mainly within the range 30~100 μm, with a variation of solvent/non-solvent ratio. The number of minute pore (4~25 μm) over chitosan scaffold increased with increasing ratio of non-solvent. New prepared scaffold exhibited larger value of breaking elongation, more elasticity, but less tensile strength than that of control scaffold.