Nicotine Effect on Hydrophobicity and Biofilm Formation of S. mutans

Methods: The effect of nicotine on the hydrophobicity of S. mutans was measured. Nicotine dilutions from 0.16-5 mg/ml were made in Tryptic Soy Broth without sucrose. Bacteria were grown in each of these dilutions for 16 h at 37^oC in 5% CO₂. The cells were washed three times in saline and hydrophobicity was measured using a hexadecane assay. Biofilm formation was measured using the same nicotine dilutions placed into the wells of 96 well sterile microtiter plates, and incubated for 16 h. The wells were rinsed, stained with crystal violet for 10 min, rinsed again with saline and the absorbance of the biofilm cells was measured at 490 nm.

Results: The results demonstrated that the hydrophobicity of S. mutans significantly increased (p<0.05) up to 2 fold as the nicotine concentration increased up to 1.25 mg/ml then hydrophobicity leveled off. The increase in hydrophobicity suggests that nicotine users will have increased S. mutans dental biofilm and caries. The biofilm data indicates that as the nicotine concentration increased, biofilm formation of the bacteria significantly increased between 2 and 4 fold.

Conclusion: This data suggests that the increase in hydrophobicity and biofilm formation of S. mutans to the tooth surface observed with nicotine is directly related. Nicotine plays a pivotal role in the caries process of smokers by increasing the ability of S. mutans to adhere to tooth surfaces.