Tong Ho Kang

Protein adsorption of dialdehyde cellulose-crosslinked chitosan with high amino group contents

Crosslinked chitosan was prepared by Schiff base formation between the aldehyde groups of dialdehyde cellulose (DAC) and the amino groups of chitosan and a subsequent reduction. DAC was obtained through periodate oxidation of cellulose and solubilization in hot water at 100°C for 1h. Three grades of DAC-crosslinked chitosan were prepared by adding various amounts DAC. The degrees of crosslinking as determined by amino group content were 3.8, 8.3, and 12.1%, respectively. DAC-crosslinked chitosan showed higher stability in the pH 2-9 range and no cytotoxicity was identified over the course of a 21-day long-term stability test. Also, DAC-crosslinked chitosan showed remarkably high bovine serum albumin (BSA) adsorption capacity at pH 5.5 as a result of the increased amino group content, due to the reaction between DAC and chitosan molecular chains occurring at multiple points even though DAC-crosslinked chitosan showed a lower degree of crosslinking.

Small molecular weight PEGylation of diosgenin in an in vivo animal study for diabetic auditory impairment treatment

Diosgenin was modified to control its in vivo bioavailability by conjugating a hydrophilic unit, tetraethylene glycol. The diosgenin-tetraethylene glycol conjugate (TE) was orally administered in streptozotocin induced diabetic mice for this auditory protection study. The bioactivity improvement of TE for in vivo diabetic auditory impairment treatment was clearly observed in three different auditory tests and compared with that of diosgenin. The improvement in in vivo efficacy suggests that the small molecular weight PEGylation of diosgenin is a synthetically robust and systematically applicable strategy to reform the poor pharmacokinetics of a hydrophobic aglycone.

Survey on the Use of MP3 Players of High School Students and the Effect to Their Hearing Thresholds

This study surveyed MP3 player usage and evaluated its effect on hearing thresholds in high school students. It is reported an increase in risk factors for hearing loss in adolescents that paralleled the increase in sales of MP3 players. A total of 538 students in two high schools in Gwangju province participated in this study. The students completed questionnaires about their MP3 player use and their pure tone hearing thresholds were tested at several frequencies. The questionnaire results indicated that 61.1%, of the students listened to music on MP3 players for more than one hour per day, 71.6% listened for four or more days per week, and 36.7% had listened for more than 3 years. Listening at a high volume of 60% of the maximum level was reported by 51% and they recognized having ear pains. The pure tone hearing threshold was found to be raised for the adolescents who had a long history of MP3 listening at high volume (p

Enhanced antidiabetic efficacy and safety of compound K⁄β-cyclodextrin inclusion complex in zebrafish

Background 20(S)-Protopanaxadiol 20-O-D-glucopyranoside, also called compound K (CK), exerts antidiabetic effects that are mediated by insulin secretion through adenosine triphosphate (ATP)-sensitive potassium (KATP) channels in pancreatic β-cells. However, the antidiabetic effects of CK may be limited because of its low bioavailability. Methods In this study, we aimed to enhance the antidiabetic activity and lower the toxicity of CK by including it with β-cyclodextrin (CD) (CD-CK), and to determine whether the CD-CK compound enhanced pancreatic islet recovery, compared to CK alone, in an alloxan-induced diabetic zebrafish model. Furthermore, we confirmed the toxicity of CD-CK relative to CK alone by morphological changes, mitochondrial damage, and TdT-UTP nick end labeling (TUNEL) assays, and determined the ratio between the toxic and therapeutic dose for both compounds to verify the relative safety of CK and CD-CK. Results The CD-CK conjugate (EC50 = 2.158μM) enhanced the recovery of pancreatic islets, compared to CK alone (EC50 = 7.221μM), as assessed in alloxan-induced diabetic zebrafish larvae. In addition, CD-CK (LC50 = 20.68μM) was less toxic than CK alone (LC50 = 14.24μM). The therapeutic index of CK and CD-CK was 1.98 and 9.58, respectively. Conclusion The CD-CK inclusion complex enhanced the recovery of damaged pancreatic islets in diabetic zebrafish. The CD-CK inclusion complex has potential as an effective antidiabetic efficacy with lower toxicity.

Regulatory effect of hydroquinone–tetraethylene glycol conjugates on zebrafish pigmentation

We synthesized two hydroquinone-tetraethylene glycol conjugates (HQ-TGs) and investigated their logP, photophysical stability, and redox chemical stability. HQ-TGs are a little more hydrophilic than hydroquinone (HQ) and show an enhanced photophysical and redox chemical stability compared with HQ. In addition we studied the effect of HQ-TGs on cell viability and on zebrafish pigmentation. MTT assay in HF-16 cells showed HQ-TGs are less cytotoxic than HQ. The phenotype-based image analysis of zebrafish larvae suggests that HQ-TGs suppress the pigmentation of zebrafish in a dose-dependent manner. The comparative experiments on stability, cytotoxicity, and zebrafish pigmentation between HQ and HQ-TGs suggest that mono tetraethylene glycol-functionalization of HQ is an alternative solution to overcome the adverse effect of HQ.

Cellulose hydrogel film for spheroid formation of human adipose-derived stemcells

AbstractsHerein, we present a new process for the formation of cell spheroids in three-dimensional culture systems using cellulose hydrogel film. Transparent cellulose hydrogel film were prepared via dissolution-regeneration with a LiOH/urea aqueous solution and methanol. The cell viability of the cellulose hydrogel film was equivalent to that of cell tissue culture plate, revealing no cytotoxicity. Spheroids of human adipose-derived stem cells (hASCs) were successfully formed on cellulose hydrogel film. Spheroid size strongly depended on the cell seeding density and culture time, becoming larger with increases in both factors. Cell differentiation simultaneously progressed favorably with the spheroid formation of hASCs. These results suggested that cellulose hydrogel film could provide a new option with regard to tissue engineering applications.

Trigonelline promotes auditory function through nerve growth factor signaling on diabetic animal models

BACKGROUND Protection of cochlear function and reconstruction of neuronal networks in damaged auditory sensory structures is crucial for therapeutic treatment of diabetic hearing loss. Nerve growth factor (NGF) has been used as a novel therapeutic target to protect against the neurodegenerative effects of Diabetes Mellitus (DM). PURPOSE We aimed to evaluate the potential effect of trigonelline (TRG) on reducing auditory damage produced by DM using NGF as a potential marker. METHOD Docking simulations were carried out using Autodock Vina software and visualized using Discovery Studio. Morphological analysis of hair cells and neuromasts was performed on alloxan-induced diabetic zebrafish by fluorescence and scanning electron microscopy. Blockage of NGF receptor phosphorylation with K-252a was used to evaluate TRG and NGF action. Further assessment of NGF by ELISA on a primary culture of spiral ganglion cells was performed as a marker of neuronal function on the hearing system. Finally, auditory function was assessed in LepR(db/db) mice using auditory brainstem response (ABR) and transient evoked otoacoustic emission (TEOAE) during 8 weeks. RESULTS Docking simulations showed that TRG binds to the active site of NGF through molecular interactions with Lysine88 (Lys88) and Tyrosine52 (Tyr52). TRG treatment significantly reduced hair cell loss and neuromast damage in diabetic zebrafish (P < .05). Further evaluation revealed a significant increase in the number of neuromasts after NGF administration (P < .001). TRG and NGF action was suppressed during blockage of NGF receptor phosphorylation. Moreover, spiral ganglion cells revealed significant elevation on NGF values after TRG treatment (P < .05). In vivo evaluation of LepR(db/db) mice revealed a significant reduction in the auditory damage produced under diabetic progression, characterized by reduced ABR hearing threshold shifts and increased signal-to-noise ratio in TEOAE (P < .05). CONCLUSIONS This study suggests that the enhanced hearing function produced by TRG may be mediated by NGF, providing a potential therapeutic strategy for diabetic hearing loss.

A Validation Study of Auditory Brainstem Response(ABR) in ICR Mouse

청각 기능을 평가하는 방법은 크게 두 가지로 나뉘는데, 피검자의 반응이 필수적인 주관적 방법과, 피검자의 능동적참여가 필요치 않고 결과를 객관적으로 분석할 수 있는 객관적 방법이 있다.11) 객관적인 검사 중 청성유발전위(auditory evoked potential, AEP)검사는 청력선별검사, 청력역치의 추정, 청각신경계의 다양한 진단과 관련하여 많이 사용되고 있다. AEP는 전기생리학적으로 전달되는 청신경계의 전기신경자극을 두피에서 기록하여 청력의 손실유무, 손실의 정도와 유형, 손실의 부위를 진단하게 된다. AEP의 종류는 소리자극 후 반응이 나타나는 기간인 잠복기(latency)