76 HYGIENE
enveloped viruses, resulting in ‘full virucidal activity’. Such formulations can be thickened with plant-based polymers that can improve the sustainability profile of the product while improving the moisturisation and skin feel.
Ingredients Klucel™ hydroxypropylcellulose (hereafter referred to as HPC) is a non-ionic, water- soluble cellulose ether with a remarkable combination of properties. It combines organic solvent solubility, wide pH range stability and surface activity with the aqueous thickening and stabilising properties characteristic of other water-soluble cellulosic polymers. HPC is an efficient film former that spreads well on skin and leaves a distinct tactile signature. Benecel™ hydroxypropylmethylcellulose
(hereafter referred to as HPMC) is another remarkable non-ionic water-soluble cellulose ether. It combines organic solvent solubility, wide pH range stability, surface activity and good spreading on skin, with a distinct tactile signature. Various grades are available for both cellulosic polymers to cater to all hand sanitiser viscosity requirements.
Results Virucidal testing was conducted following standard protocols (Table 1). Efficacy against both enveloped and non-enveloped viruses was tested to claim full virucidal activity. The detail of viruses, the family they represent and the diseases they may cause are also listed in Table 1 for information. In this article, ‘full virucidal activity’ refers
to a pass on testing against both enveloped and non-enveloped viruses. In Table 1, one can also find reference to bacteria and yeast, which are the micro-organisms commonly killed by hand sanitisers. The improved performance proposed in this article goes beyond by also tackling viruses, which is the testing presented further. Table 2 summarises the results of the
virucidal testing for two formulations containing 70% ethanol, 2% lactic acid and a cellulosic thickener. The pH of the formulations is 3.5 and the viscosity falls within the range recognised as a gel hand sanitiser from consumers. The formulation thickened with HPC shows
activity against three non-enveloped viruses including human poliovirus, as poliovirus in
Formulation Type
Ethanol 70% Lactic acid 2% + Klucel H CS 1%
Ethanol 70% Lactic acid 2% + Benecel E10M 1.5%
Non-enveloped viruses
Enveloped viruses
Non-enveloped viruses
Human adenovirus Pass 60
Table 2: Summary of test results for two low pH hand sanitiser formulations. Both contain 70% ethanol and 2% lactic acid, one is thickened with 1% HPC (Klucel H CS), the other with 1.5% HPMC (Benecel E10M). The pH of both formulations is 3.5 and the viscosity typical of a gel sanitiser. The type/name of viruses tested against, results and contact time are listed
general is notoriously difficult to kill, usually requiring a high level of alcohol (>80%). The low pH increases the activity of the formulation allowing a pass with as little as 70% alcohol. This is an effect which has been measured
and recently reported in the scientific literature.1,2
For example, Kampf in the Journal
of Hospital Infections in 2018 reports a substantial improvement of ethanol virucidal activity against poliovirus.3 A contact time of 120 seconds was chosen
for testing as this is considered acceptable and challenging enough for human poliovirus. This formulation also passes testing against human adenovirus and murine norovirus with a contact time of 120 seconds. The same formulation was tested against
vaccinia virus representing enveloped viruses, hence a proxy for coronavirus. A contact time of 60 seconds was chosen and is considered more realistic for this test, as it represents a more reasonable kill time, as well as time the consumer keeps sanitiser on hands. This formulation containing HPC shows full virucidal activity, i.e. against both enveloped and non-enveloped viruses. To challenge the formulations further, a
contact time of 60 seconds was applied for testing against human adenovirus and murine norovirus. The formulation contains a HPMC thickener that showed passes against both viruses. Thickener has no activity against microorganisms, therefore the results from
TABLE 3: HAND SANITISER FORMULATION THICKENED WITH A SYNTHETIC POLYMER
Phase Ingredients
A Carbomer 980 Water
INCI Carbomer Water (Aqua)
Ethanol (99.9%) Ethyl Alcohol AMP (95%) Glycerin
2-amino 2-methyl-1-propanol Glycerin
M200-1294D w/w (%)
0.5 27.37
70.00 0.13
2.00
Table 3: The appearance is of a clear viscous gel, the viscosity is within the range 15000 - 20000 cP, measured with Brookfield RV spindle 4, speed 10 rpm at 25 °C. pH of formula is within the range 6.80 - 7.50
PERSONAL CARE October 2022
one formulation can be extrapolated to the other, showing either of these thickeners to be suitable in ethanol/acid combinations. Another advantage of using cellulosic
derivatives to thicken alcohol-based formulations is the nice feel they leave on skin after use. These molecules are efficient film formers, substantive enough to skin to provide a large coverage that acts as a protective barrier and gives a desirable tactile signature. Sensory studies, as well as technical
measurements on skin hydration and water retention, have been conducted on two formulations: one thickened with a market leader acrylate technology (Table 3) and one thickened with HPC (Table 4). Skin hydration was measured on human
skin, following a clinical protocol, developed internally: ■ Six panel members ■ Application on the inner forearm on skin patch with a size of 5 x 5cm ■ 2mg/cm2
product applied
■ Testing time points T0, T30, T60 and T90, numbers refer to the minutes after application The results of this test are shown in Figure
1. At all time points, the improvement on skin hydration is similar for the carbomer containing formula and the untreated skin - both are low, below 8%. In contrast, the improvement reaches a minimum of 40% for the HPC containing formula, statistically significantly above the control and the carbomer containing one.
TABLE 4: HAND SANITISER FORMULATION THICKENED WITH HPC (KLUCEL H)
Phase Ingredients INCI A Ethanol (99.9%) Ethanol Klucel H CS HPC Hydroxypropyl cellulose
B Deionized water Water (Aqua) Propylene glycol Propylene Glycol
C
M200-1330 w/w (%)
70.00 1.00
24.88 1.00
Table 4: The appearance is of a flowable liquid gel with a viscosity within the range 1500 - 2500 cP as measured by Brookfield LVT spindle 63, speed 12 rpm at 25 °C. The pH of the formulation is within the range 3.30 – 3.70
www.personalcaremagazine.com Virus tested
Human poliovirus Human adenovirus Murine norovirus
Vaccinia Human adenovirus Result
Pass Pass Pass
Pass Pass Contact time pH Viscosity cP #RV04 20 rpm 120 1940 60 3.5 60 1690
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