Читать книгу Oral Biofilms - Группа авторов - Страница 58

Multiple in vitro biofilm models have emerged and been described in the last 2 decades. Oral biofilm models can be divided into three groups: constant depth film fermenter, flow cell chamber systems, and closed batch culture models. The constant depth film fermenter is a dynamic biofilm model that allows the control of environmental factors such as the substratum, the nutrient source, the gas flow, and especially biofilm thickness [12, 13]. The flow cell chamber system consists of a glass slide coated with saliva that is placed in a chamber and is crossed by a continuous flow of medium [14]. So far, this model has been used in order to test the effect of osteopontin, a glycosylated and highly phosphorylated whey protein in multispecies biofilms [15]. Furthermore, a flow chamber model was used to examine the effect of antibiotics on established biofilms and allows for the observation of biofilm formation under flow and shear force conditions [16]. With batch biofilm models, a biofilm is formed either on a plate wall, on the surface of discs, coupons or pegs, or on human/bovine enamel within the well. A closed system is used so that the environment inside the well changes during the test as nutrients are consumed and metabolic products accumulate unless the growth media are replaced [17]. While constant-depth film fermenter biofilm models and flow cell chamber systems work under flow conditions and closely mimic the in vivo situation or show real-time biofilm formation, respectively, and thus have contributed to our understanding of microbial adhesion and biofilm formation, their use has certain drawbacks. For instance, they can be cumbersome to construct and/or difficult to maintain over long periods of time. Since clearance of pulsed substances is a function of flow rate and volume, chemostats operating with low flow rates and relatively large volumes can have quite long mean residence times, rendering them impractical for studies of selected compounds with short-term exposure, as is common in oral hygiene procedures. Moreover, systems with working volumes of more than a few milliliters preclude the use of media constituted from natural substrates such as saliva.

Depending on the aim of biofilm analyses, the design of the model can vary considerably with regards to the substrate, medium, biofilm harvesting, and subsequent analysis. In some studies, glass or polystyrene surfaces are used as substrates for biofilm formation, whereas dentin, enamel, or artificial hydroxyapatite discs are also used in other reports. For biofilm growth, the medium used has to fulfill the complex nutritional requirements. Saliva or combinations of saliva with selective media can be applied as well. To identify biofilm microorganisms either cultivation-dependent or cultivation-independent approaches are applied.