Seohyun Kim

Physicochemical study of ascorbic acid 2-glucoside loaded hyaluronic acid dissolving microneedles irradiated by electron beam and gamma ray

A dissolving microneedle (DMN) patch encapsulated with ascorbic acid 2-glucoside (AA2G) in a needle-shaped hyaluronic acid (HA) backbone was fabricated and sterilized by electron beam (e-beam, 5-40kGy) and gamma ray (γ-ray, 5-30kGy). DMN structures maintained their morphologies and fracture force regardless of e-beam and γ-ray irradiation doses. Both e-beam (40kGy) and γ-ray (20 and 30kGy) met the product sterility requirements for cosmetics and vaccines; however, γ-ray irradiation significantly degraded the encapsulated AA2G, while e-beam maintained AA2G activity. Thus, an e-beam dose of 40kGy, which satisfied the sterility requirements without loss of AA2G, is suitable for terminal sterilization of DMNs. Moreover, we confirmed that the optimized irradiation (e-beam, 40kGy) did not affect dissolution rate and drug release profile of DMNs. Further, we confirmed that HA, the backbone polymer of DMNs, could be utilized as a stabilizer that inhibits degradation of encapsulated AA2G by irradiation. This detailed analysis can be developed further to optimize various biological drugs in transdermal drug delivery systems.

Biomechanical methodology for evaluating seat comfort during long term driving according to the variation of seat back angle

The aim of this study is to suggest a biomechanical methodology for evaluating seat comfort during long term driving with a use of driving stimulator. Recent modern car seat has become increasingly complexed and sophisticated with ongoing seat discomfort problems. Consumers’ demands for better seat comfort have also increased but most of them still choose car seats in the wrong way. Previous researches have recommended quantifying overall car seat discomfort based on questionnaire, EMG, and FEM etc. However, it is difficult to find successful objective evaluation methods in both in literature or in actual situations. Six males were recruited to participate in a laboratory study. All participants performed three trials separated by three different seat back angles (87°, 97°, and 107°) and each trial was conducted on different days. Each trial was consisted of 120 min of continuous driving on the driving simulator. Participants were recorded using Kinect v2 with a full body and pressure at both seat pan and back were measured to allow the investigator to analyze their postures. The results for each seat condition were analyzed through unpaired t-test in order to acquire statistical significance (P < 0.05). As expected, the overall discomfort rating increased over time, especially for neck and low back. Also, at 87° and 107°, the overall discomfort rating was higher than 97°. In addition, over time, we found an increase in pressure in both seat back and seat pan. These results suggest that a new biomechanical method could be an alternative for evaluating car seat comfort for long-term driving.