The colonization of dental implants by oral biofilms causes inflammatory reactions that can ultimately lead to implant loss. Therefore, safety-integrated implant surfaces are under development that aim to detect bacterial attachment at an early stage and subsequently release antibacterial compounds to prevent their accumulation. Since primary oral colonizers ferment carbohydrates leading to local acidification, pH is considered a promising trigger for these surfaces. As a prerequisite for such systems, the present study aimed at specifically analyzing the pH at the interface between implant material and oral biofilms. For this purpose, in vitro–grown Streptococcus oralis monospecies biofilms and an established multispecies biofilm on titanium discs as well as in situ–grown biofilms from orally exposed titanium-equipped splints were used. Mature biofilm morphology was characterized by live/dead fluorescence staining, revealing improved growth from in vitro to in situ biofilms as well as a general decreasing membrane permeability over time due to the static incubation conditions. For pH analysis, the pH-sensitive dye C-SNARF-4 combined with 3-dimensional imaging by confocal laser-scanning microscopy and digital image analysis were used to detect extracellular pH values in different biofilm layers. All mature biofilms showed a pH gradient, with the lowest values at the material interface. Interestingly, the exact values depicted a time- and nutrient-dependent gradual acidification independently of the biofilm source and for in situ biofilms also independently of the sample donor. After short incubation times, a mild acidification to approximately pH 6.3 could be observed. But when sufficient nutrients were processed for a longer period of time, acidification intensified, leading to approximately pH 5.0. This not only defines the required turning point of pH-triggered implant release systems but also reveals the opportunity for a tailored release at different stages of biofilm formation.

中文翻译：

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口腔生物膜-种植体材料界面的逐渐酸化


口腔生物膜在种植牙上的定植会引起炎症反应，最终导致种植体丢失。因此，正在开发安全集成的植入物表面，旨在早期检测细菌附着，然后释放抗菌化合物以防止其积累。由于原代口服定植剂会发酵碳水化合物导致局部酸化，因此 pH 值被认为是这些表面的一个有前途的触发因素。作为此类系统的先决条件，本研究旨在专门分析植入物材料和口腔生物膜之间界面的 pH 值。为此，使用了体外生长的口链球菌单物种生物膜和钛盘上已建立的多物种生物膜，以及来自口腔暴露的钛夹板的原位生长生物膜。成熟生物膜形态以活/死荧光染色为特征，显示从体外到原位生物膜的生长得到改善，并且由于静态培养条件，膜通透性随着时间的推移普遍降低。对于 pH 分析，使用 pH 敏感染料 C-SNARF-4 结合共聚焦激光扫描显微镜的 3 维成像和数字图像分析来检测不同生物膜层中的细胞外 pH 值。所有成熟的生物膜都显示出 pH 梯度，在材料界面处的值最低。有趣的是，确切的值描述了独立于生物膜来源的时间和营养依赖性逐渐酸化，并且原位生物膜也独立于样品供体。孵育时间短后，可以观察到轻度酸化至约 pH 6.3。 但是，当足够的营养物质经过较长时间的加工时，酸化加剧，导致 pH 值约为 5.0。这不仅定义了 pH 触发的植入物释放系统所需的转折点，还揭示了在生物膜形成的不同阶段进行定制释放的机会。