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Biofilm three-dimensional architecture influences in situ pH distribution pattern on the human enamel surface

International Journal of Oral Science 2017年第2期9卷 74-79页

作者： Jin Xiao Anderson T Hara dongyeop kim Domenick T Zero Hyun Koo Geelsu Hwang Eastman Institute for Oral Health University of Rochester Medical Center Department of Cariology Operative Dentistry and Dental Public HealthOral Health Research InstituteIndiana University School of Dentistry Biofilm Research Laboratories Levy Center for Oral HealthDepartment of Orthodontics and Divisions of Pediatric Dentistry & Community Oral HealthSchool of Dental MedicineUniversity of Pennsylvania

To investigate how the biofilm three-dimensional(3D) architecture influences in situ pH distribution patterns on the enamel surface. Biofilms were formed on human tooth enamel in the presence of 1% sucrose or 0.5% glucose plus 0.5% fructose. At specific time points, biofilms were exposed to a neutral pH buffer to mimic the buffering of saliva and subsequently pulsed with 1% glucose to induce re-acidification. Simultaneous 3D pH mapping and architecture of intact biofilms was performed using two-photon confocal microscopy. The enamel surface and mineral content characteristics were examined successively via optical profilometry and microradiography analyses. Sucrose-mediated biofilm formation created spatial heterogeneities manifested by complex networks of bacterial clusters(microcolonies). Acidic regions(pH<5.5) were found only in the interior of microcolonies,which impedes rapid neutralization(taking more than 120 min for neutralization). Glucose exposure rapidly re-created the acidic niches, indicating formation of diffusion barriers associated with microcolonies structure. Enamel demineralization(white spots),rougher surface, deeper lesion and more mineral loss appeared to be associated with the localization of these bacterial clusters at the biofilm-enamel interface. Similar 3D architecture was observed in plaque-biofilms formed in vivo in the presence of sucrose. The formation of complex 3D architectures creates spatially heterogeneous acidic microenvironments in close proximity of enamel surface, which might correlate with the localized pattern of the onset of carious lesions(white spot like) on teeth.

关键词： biofilms demineralization dental caries exopolysaccharides microcolonies pH microenvironments plaque Streptococcus mutans

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Elucidating the photoluminescence-enhancement mechanism in a push-pull conjugated polymer induced by hot-electron injection from gold nanoparticles

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Photonics Research 2021年第2期9卷 131-141页

作者： DONGKI LEE SE GYO HAN JUNGHO MUN KIHYUK YANG SUNG HYUK kim JUNSUK RHO KILWON CHO dongyeop X.OH MUN SEOK JEONG Department of Energy Science Sungkyunkwan UniversitySuwon 16419Republic of Korea Department of Chemical Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea Department of Mechanical Engineering Pohang University of Science and TechnologyPohang 37673Republic of Korea Research Center for Bio-based Chemistry Korea Research Institute of Chemical Technology(KRICT)Ulsan 44429Republic of Korea

Understanding the photophysical interactions between the components in organic-inorganic nanocomposites is a key factor for their efficient application in optoelectronic devices. In particular, the photophysical study of nanocomposites based on organic conjugated polymers is rare. We investigated the effect of surface plasmon resonance(SPR) of gold nanoparticles(Au NPs) on the photoluminescence(PL) property of a push-pull conjugated polymer(PBDB-T). We prepared the hybrid system by incorporating poly(3-hexylthiophene)-stabilized Au NPs(P3 HT-Au NPs) into PBDB-T. The enhanced and blueshifted PL was observed in the hybrid system compared to PL in a neat PBDB-T system, indicating that the P3 HT chains attached to the Au NPs suppressed charge-transfer from PBDB-T to the Au NPs and relayed the hot electrons to PBDB-T(the band-filling effect).This photophysical phenomenon limited the auto-dissociation of PBDB-T excitons. Thus, the radiative recombination of the excitons occurred more in our hybrid system than in the neat system.

关键词： conjugated system polymer

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