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Nanomechanics of Cation–π Interactions in Aqueous Solution
Lu, Qingye,Oh, Dongyeop X.,Lee, Youngjin,Jho, Yongseok,Hwang, Dong Soo,Zeng, Hongbo WILEY‐VCH Verlag 2013 Angewandte Chemie Vol.125 No.14
<P><B>Eine erste direkte Untersuchung</B> der Nanomechanik von Kation‐π‐Wechselwirkungen in wässrigem Medium wurde mit einem Oberflächenkraftmessgerät durchgeführt und durch theoretische Simulationen ergänzt. Das Tetraethylammonium‐Ion (TEA) verhindert die Adhäsion von Polytryptophan (PTrp) und Poly‐<SMALL>L</SMALL>‐lysin (PLL) mit einer 100‐fach höheren Empfindlichkeit als das K<SUP>+</SUP>‐Ion (PS=Polystyrol, PTyr=Poly‐<SMALL>L</SMALL>‐tyrosin, ACh=Acetylcholin).</P>
Tunicate-mimetic nanofibrous hydrogel adhesive with improved wet adhesion
Oh, Dongyeop X.,Kim, Sangsik,Lee, Dohoon,Hwang, Dong Soo Elsevier 2015 ACTA BIOMATERIALIA Vol.20 No.-
<P><B>Abstract</B></P> <P>The main impediment to medical application of biomaterial-based adhesives is their poor wet adhesion strength due to hydration-induced softening and dissolution. To solve this problem, we mimicked the wound healing process found in tunicates, which use a nanofiber structure and pyrogallol group to heal any damage on its tunic under sea water. We fabricated a tunicate-mimetic hydrogel adhesive based on a chitin nanofiber/gallic acid (a pyrogallol acid) composite. The pyrogallol group-mediated cross-linking and the nanofibrous structures improved the dissolution resistance and cohesion strength of the hydrogel compared to the amorphous polymeric hydrogels in wet condition. The tunicate-mimetic adhesives showed higher adhesion strength between fully hydrated skin tissues than did fibrin glue and mussel-mimetic adhesives. The tunicate mimetic hydrogels were produced at low cost from recyclable and abundant raw materials. This tunicate-mimetic adhesive system is an example of how natural materials can be engineered for biomedical applications.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A biomimetic chitosan composite with improved mechanical properties in wet conditions
Dongyeop X. Oh,Dong Soo Hwang 한국당과학회 2012 한국당과학회 학술대회 Vol.2012 No.1
Chitosan is one of the most widely used structural polymers for biomedical applications because it has many favorable properties. However, one of the most critical drawbacks regarding the use of chitosan as a biomedical material is its poor mechanical properties in wet conditions. Here, we designed a method to improve the mechanical properties of chitosan in wet conditions and minimized the swelling behavior of chitosan film due to water adsorption by mimicking the sclerotization of insect cuticles and squid beaks, i.e., catechol-meditated cross-linking. The biomimetic chitosan composite film was prepared by mixing chitosan with L-3,4-dihydroxyphenylalanine (DOPA) as a catecholic cross-linker and sodium periodate as an oxidant. The catechol-meditated cross-linking provided a 7-fold enhancement in the stiffness in wet conditions compared to pure chitosan films and reduced the swelling behavior of the chitosan film. This strategy expands the possible applications for the use of chitosan composites as load-bearing biomaterials.
Parylene-Coated Cellulose Nanofiber Films with Improved Oxygen Barrier and Water Resistance
Trans Tech Publications, Ltd. 2018 Materials science forum Vol.926 No.-
<P>In this paper, we introduce a parylene-coated cellulose nanofiber film. The parylene coating overcomes the limitations of cellulose nanofiber films used as food packaging films. The disadvantages of cellulose nanofiber films are that they are poor oxygen barriers and have low water resistances. This parylene-coated film achieved a low oxygen transfer rate (OTR) of @@<@@5 ml/m<SUP>2</SUP>/day because the parylene coating effectively covered the surface pores. In contrast to a pristine cellulose nanofiber film, the parylene-coated film was hydrophobic and exhibited a water contact angle of @@>@@75º. Similar to macro-cellulose papers, the pristine cellulose nanofiber film absorbed water and tore easily. The parylene-coated film was not permeable to water. However, the coating did not yield a significant improvement in the mechanical properties or light transmittance. We also investigated the change in surface morphology by the parylene coating. The parylene-coated film has great potential as a food packaging film owing to its improved oxygen barrier and water resistance characteristics.</P>
Kang, Taegon,Oh, Dongyeop X.,Heo, Jinhwa,Lee, Han-Koo,Choy, Seunghwan,Hawker, Craig J.,Hwang, Dong Soo American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.44
<P>Mussels survive by strongly attaching to a variety of different surfaces, primarily subsurface rocks composed of metal oxides, through the formation of coordinative interactions driven by protein-based catechol repeating units contained within their adhesive secretions. From a chemistry perspective, catechols are known to form strong and reversible complexes with metal ions or metal oxides, with the binding affinity being dependent on the nature of the metal ion. As a result, catechol binding with metal oxides is reversible and can be broken in the presence of a free metal ion with a higher stability constant. It is proposed to exploit this competitive exchange in the design of a new strategy for the formation, removal, and reformation of surface coatings and self-assembled monolayers (SAM) based on catechols as the adhesive unit. In this study, catechol-functionalized tri(ethylene oxide) (TEO) was synthesized as a removable and recoverable self-assembled monolayer (SAM) for use on oxides surfaces. Attachment and detachment of these catechol derivatives on a variety of surfaces was shown to be reversible and controllable by exploiting the high stability constant of catechol to soluble metal ions, such as Fe(III). This tunable assembly based on catechol binding to metal oxides represents a new concept for reformable coatings with applications in fields ranging from friction/wettability control to biomolecular sensing and antifouling.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-44/acsami.5b06910/production/images/medium/am-2015-06910j_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b06910'>ACS Electronic Supporting Info</A></P>