posted on 2021-09-27, 20:13authored byGuang-Rong Tan, Chin-Ying Stephen Hsu, Yong Zhang
Engineering
highly sensitive nanomaterials to monitor spatiotemporal
pH changes has rather broad applications in studying various biological
systems. Intraoral/biofilm–tooth pH is the single parameter
that has demonstrated accurate assessment of dental caries risk, reflecting
the summative integrated outcome of the complicated interactions between
three etiological factors, namely, microorganisms/biofilm, diet/carbohydrates,
and tooth/saliva/host. However, there is little to no technology/system
capable of accurately probing simultaneously both the micro-pH profiles
in dentin tissues and acidogenic oral biofilms and examining the pathophysiologic
acid attacks with high spatial/temporal resolution. Therefore, a highly
sensitive pH-responsive hybrid nanoparticle (pH-NP) is developed and
coupled with an ex vivo tooth–biofilm caries
model to simulate and study the key cariogenic determinants/steps.
The pH-NP emits two distinct fluorescences with mutually inversely
proportional intensities that vary accordingly to the proximity pH
and with a ratiometric output sensitivity of 13.4-fold across a broad
clinically relevant pH range of 3.0–8.0. Using [H+], in addition to pH, to calculate the “area-under-curve”
corroborates the “minimum-pH” in semiquantifying the
demineralizing potential in each biofilm-dentin zones/depth. The data
mechanistically elucidates a two-pronged cariogenic effect of a popular-acidic-sweet-drink,
in inundating the biofilm/tooth-system with H+ ions from
both the drink and the metabolic byproducts of the biofilm.