Anti-dirt hand sanitizer: A zeolite-enhanced approach to hygiene and microbial protection

Children love to play with dirt and their outdoor activities oftentimes make their hands heavily soiled. Meanwhile, improper sanitation of the hands prior to making contact with food or bodily fluids can result in potentially dangerous infection. In situations where handwashing is not available, hand sanitizers present a common cleaning agent of choice. However, as it is shown here, standard sanitizers, albeit acting effectively against skin microbes, do not have the ability to remove the dirt deposits off children’s hands, where microbial colonies may remain protected against the antiseptic effect of the sanitizer. To circumvent this limitation, we designed and synthesized an antimicrobial hand sanitizer gel capable of removing such dirt deposits. This novel form of the hand sanitizer was created by adding a low-silica zeolite (M y z+ [Si 1-x Al x O 2 ] x- {x = 0.375, x=yz}) zeolite, a common environmental remediation agent, in three different weight fractions (1, 5 and 10 wt.%) to the base formulation containing ethanol and water at different volume ratios (60:40 and 70:30 v/v), alongside methylcellulose as the gelling agent and glycerin as the humectant. The dirt-removal efficiency of zeolite-containing formulations was significantly higher than that of the zeolite-free formulations and directly proportional to the amount of zeolite dispersed in them. Antibacterial assays demonstrated the evident antiseptic effect of all the formulations against cultivable bacteria sampled from the soiled hands. Fundamental and practical findings shared here can aid in the design of an anti-dirt hand sanitizer for the prevention of exposure of both pediatric and general populations to obligate or opportunistic pathogens residing in various environmental sources. • We demonstrate that standard alcoholic hand sanitizers have a limited ability to decontaminate hands containing solidified deposits of dirt or mud. • We have created a series of alcoholic-aqueous colloidal zeolite gel dispersions and tested them for their ability to decontaminate the soiled children’s hands. • The antiseptic effect of all the formulations was evident, while their capacity to remove the deposits of dirt from the hands increased in direct proportion with the amount of the zeolite. • The colloidal stability of the gels was compromised at elevated ethanol concentrations, in spite of the marginally higher antibacterial activity. • The presence of zeolite reduced the activity of the alcohol against aerobic and cultivable bacteria residing in the mud deposits.