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Jang, Jinhyeong,Cha, Chaenyung American Chemical Society 2018 Biomacromolecules Vol.19 No.2
<P>Hydrogels possess favorable physical properties ideally suited for various biotechnology applications. To tailor to specific needs, a number of modification strategies have been employed to tune their properties. Herein, a multifunctional polymeric cross-linker based on polyaspartamide is developed, which allows for the facile adjustment of the type and number of reactive functional groups to fit different reaction schemes and control the physical properties of the hydrogels. The amine-based nucleophiles containing desired functional groups are reacted with polysuccinimide to synthesize polyaspartamide cross-linkers. The cross-linking density and the concurrent change in mechanical properties of the resulting hydrogels are controlled in a wide range only with the degree of substitution. This multivalency of the polyaspartamide linkers also induced the degradation of hydrogels by the unreacted functional groups on polyaspartamide involved in the hydrolysis. Furthermore, the polyaspartamide cross-linker conjugated with cell-recognition molecules via the same conjugation mechanism (i.e., nucleophilic substitution) render the hydrogels cell-responsive without the need of additional processing steps. This versatility of polyaspartamide-based cross-linker is expected to provide an efficient and versatile route to engineer hydrogels with controllable properties for biomedical applications.</P>
Jang, Jinhyeong,Hong, Jisu,Cha, Chaenyung Elsevier 2017 Journal of the mechanical behavior of biomedical m Vol.69 No.-
<P><B>Abstract</B></P> <P>Graphene oxide (GO) is increasingly investigated as a reinforcing nanofiller for various hydrogels for biomedical applications for its superior mechanical strength. However, the reinforcing mechanism of GO in different hydrogel conditions has not been extensively explored and elucidated to date. Herein, we systematically examine the effects of various types of precursor molecules (monomers vs. macromers) as well as mode of GO incorporation (physical vs. covalent) on the mechanical properties of resulting composite hydrogels. Two hydrogel types, (1) polyacrylamide hydrogels with varying concentrations of acrylamide monomers and (2) poly(ethylene glycol) (PEG) hydrogels with varying molecular weights of PEG macromers, are used as model systems. In addition, incorporation of GO is also controlled by using either unmodified GO or methacrylic GO (MGO) which allows for covalent incorporation. The results in this study demonstrate that the interaction between GO and the surrounding network and its effect on the mechanical properties (i.e. rigidity and toughness) of composite hydrogels are highly dependent on both the type and concentration of precursors and the mode of crosslinking. We expect this study will provide an important guideline for future research efforts on controlling the mechanical properties of GO-based composite hydrogels.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kuk, Su Keun,Jang, Junho,Han, Hyeuk Jin,Lee, Eunsang,Oh, Hyeongyeol,Kim, Hwea Yoon,Jang, Jinhyeong,Lee, Kang Taek,Lee, Hohjai,Jung, Yeon Sik,Park, Chan Beum,Bae, Byeong-Soo American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.17
<P>Herein, we report a siloxane-encapsulated upconversion nanoparticle hybrid composite (SE-UCNP), which exhibits excellent photoluminescence (PL) stability for over 40 days even at an elevated temperature, in high humidity, and in harsh chemicals. The SE-UCNP is synthesized through UV-induced free-radical polymerization of a sol-gel-derived UCNP-containing oligosiloxane resin (UCNP-oligosiloxane). The siloxane matrix with a random network structure by Si-O-Si bonds successfully encapsulates the UCNPs with chemical linkages between the siloxane matrix and organic ligands on UCNPs. This encapsulation results in surface passivation retaining the intrinsic fluorescent properties of UCNPs under severe conditions (e.g., 85 °C/85% relative humidity) and a wide range of pH (from 1 to 14). As an application example, we fabricate a two-color binary microbarcode based on SE-UCNP via a low-cost transfer printing process. Under near-infrared irradiation, the binary sequences in our barcode are readable enough to identify objects using a mobile phone camera. The hybridization of UCNPs with a siloxane matrix provides the capacity for highly stable UCNP-based applications in real environments.</P> [FIG OMISSION]</BR>
Byeon Gihwan,Kwon Sung Ok,Jhoo JinHyeong,Jang Jae-Won,Kim Yeshin 대한치매학회 2023 Dementia and Neurocognitive Disorders Vol.22 No.2
Background and Purpose: The National Responsibility Policy for Dementia Care was implemented in September 2017 in Korea. This study aimed to compare dementia incidence in Seoul and Gangwon-do before and after the implementation of this policy. Methods: We extracted insurance claim data from the Korean Health Insurance Review and Assessment Service for people diagnosed with diabetes, hypertension, or dyslipidemia for the first time in Seoul and Gangwon-do, Korea. We defined two enrollment groups based on the policy implementation date: 1) January 1, 2015 to December 31, 2016 (Index 1, pre-implementation), and 2) January 1, 2017 to December 31, 2018 (Index 2, post-implementation). Each group was followed up for 1 year from the time of enrollment. Then, we calculated hazard ratios to compare the incidence of dementia between the two groups, and between Seoul and Gangwon-do. Results: In Seoul, the incidence of dementia was significantly lower in Index 2 than in Index 1 (hazard ratio [HR], 0.926; 95% confidence interval [CI], 0.875–0.979). However, the incidence rate did not differ between the 2 groups (HR, 1.113; 95% CI, 0.966–1.281) in Gangwon-do. In Index 1, the incidence of dementia did not differ between Seoul and Gangwon-do (HR, 1.043; 95% CI, 0.941–1.156), but in Index 2, was significantly higher in Gangwon-do than in Seoul (HR, 1.240; 95% CI, 1.109–1.386). Conclusions: After implementing the National Responsibility Policy for Dementia Care, the dementia incidence rate decreased significantly in Seoul, consistent with other studies, but not in Gangwon-do.