In vitro model systems for exploring oral biofilms: From single‐species populations to complex multi‐species communities

Abstract

Numerous in vitro biofilm model systems are available to study oral biofilms. Over the past several decades, increased understanding of oral biology and advances in technology have facilitated more accurate simulation of intraoral conditions and have allowed for the increased generalizability of in vitro oral biofilm studies. The integration of contemporary systems with confocal microscopy and 16S rRNA community profiling have enhanced the capabilities of in vitro biofilm model systems to quantify biofilm architecture and analyze microbial community composition. In this review, we describe several model systems relevant to modern in vitro oral biofilm studies: the constant depth film fermenter, Sorbarod perfusion system, drip-flow reactor, modified Robbins device, flowcells, and microfluidic systems. We highlight how combining these systems with confocal microscopy and community composition analysis tools aids exploration of oral biofilm development under different conditions and in response to antimicrobial/anti-biofilm agents. The review closes with a discussion of future directions for the field of in vitro oral biofilm imaging and analysis. Introduction: Importance of in vitro model systems to the study of oral biofilmsMicroorganisms form dynamic multi-species biofilm communities on numerous surfaces in the human oral cavity (Marsh 2009). Over time, oral biofilms change in composition and architecture as component microbes interact with each other, the environment, and the host (Lamont et al. 2018). Oral biofilm communities can be extremely resilient; redeveloping rapidly after physical perturbations (e.g. brushing or flossing) and chemical treatments (e.g. application of mouthwash) (Marsh 2010). Furthermore, certain ecological and environmental conditions can alter the microbial composition and behavior of oral biofilm communities resulting in dental caries and periodontal disease (Aas et al. 2008;Peterson et al. 2013;Marsh 2018). Dental caries and periodontal disease are among the most prevalent of human diseases (Petersen et al. 2005) ranking 1 and 11 in a 2016 ranking of global health burden of 328 diseases (Vos and Collaborators 2017). In 2016, an estimated 2.44 billion people had active dental caries while

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Bacterial biofilms in the human body: prevalence and impacts on health and disease

“…Progress has also been made towards modeling respiratory infections of non-CF patients, such as through the use of differentiated primary human airway cells cultured at an air-liquid interface ( Hasan et al., 2018 ). As for the gastrointestinal tract, complex in vitro models have been developed that simulate many aspects of the oral environment, including saliva, fluid flow, and surfaces that resemble natural tooth enamel, although challenges remain in modeling bacterial interactions with gingival tissue ( Luo et al., 2022 ). Primary-tissue-derived models of the human gastric mucosa and intestinal epithelium have also taken shape over the last decade, including three-dimensional organoids that largely recapitulate the cell-type diversity of the native tissue; apical-out organoids in which the orientation of the polarized epithelium is inverted for easier experimental access; two-dimensional organoid-derived monolayers; and organoid-derived microfluidic systems ( Sato et al., 2011 ; Fujii et al., 2018 ; Co et al., 2019 ; Kim et al., 2019 ; Sontheimer-Phelps et al., 2020 ).…”