Viscosity of Carboxymethylcellulose, Hydroxyethylcellulose and Polyethylene Glycol and Their Effect on Salivary Enzymes

Objectives Carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC) and polyethylene glycol (PEG) are commonly used polymers for oral health care products. This study aimed to identify the molecular weight (MW)–concentration combinations of these polymers with viscosities comparable to human whole saliva and to evaluate their influence on antimicrobial enzymatic activities. Methods Viscosity was measured with a cone-and-plate viscometer at 6 shear rates (11.3-450.0 s −1 ) for CMC and HEC (90 and 250 kDa) and PEG (1, 10, 20 and 35 kDa) at various concentrations. Their effects on hen egg-white lysozyme (HEWL), bovine lactoperoxidase (bLPO) and the glucose oxidase–peroxidase (GO–PO) system were examined. Human whole saliva was used for salivary enzyme source. The independent effects of polymer concentration and MW were also investigated. Results Seven MW–concentration combinations exhibited viscosities comparable to human whole saliva within physiological shear ranges. CMC inhibited HEWL activity but enhanced salivary lysozyme activity, whereas HEC and PEG enhanced both. All 3 polymers enhanced bLPO activity, but HEC and PEG decreased salivary peroxidase activity. All polymers inhibited the GO–PO activity. These effects were concentration-dependent, with most significant changes at concentrations well below those used in oral health care products. Polymers of higher MW resulted in greater inhibition of salivary peroxidase activity. Conclusions CMC, HEC and PEG differentially affected antimicrobial enzymatic activities, with the direction and magnitude of effects dependent on polymer type, MW, concentration and enzyme source. Clinical Relevance These findings provide useful information for the formulation of polymers in oral health care products.