Colloid and Surface ScienceColloid and Surface Science Aspects of DisinfectantsAspects of Disinfectants

Reginald JacquesGarret LauCarla Ng

Pintu Saha

University at Buffalo, Department of Chemical Engineering

INTRODUCTION 3

PRODUCT AND CONSUMER CONSIDERATIONS 4

MARKETING 5

COMPONENTS AND COMPOSITIONS OF DISINFECTANTS FOR HOUSEHOLD USE 6

General Components of Cleaning Solutions 6

Common Disinfecting Chemicals 9

COLLOIDS IN DISINFECTANTS: SURFACTANTS 13

STRUCTURE-PROPERTY RELATIONSHIPS 18

Disinfectants of the Future: Current Research 23

2

Introduction

Disinfectants represent a wide range of substances that are used in various

applications. The food industry requires the use of disinfectants to sanitize food

preparation areas, and serve preservative functions. Chlorine and other organic oxidizers

are employed for the purification of drinking water. Hospitals and clinics rely on

disinfectants to sanitize their medical facilities. Disinfectants are even used for their

preservative abilities in paints, inks, cosmetics, and other industries. And of course, the

disinfectants most people are familiar with, household disinfectants, serve to help us with

controlling germ and bacteria levels in our kitchens, bathrooms, and bodies. Despite the

variety in disinfectant materials, they all strive for one desired characteristic: selective

toxicity. Disinfectants are engineered to kill bacteria, viruses, and mildew, yet be safe to

possible human contact.

In the United States, the primary regulations that disinfectants must abide by are

established by the Environmental Protection Agency (EPA) and the Food and Drug

Administration (FDA). The EPA regulates drinking water purification, finding ways to

limit or replace chlorine as a disinfectant, fearing the biological contamination of organic

chlorinated byproducts (w4). Household disinfectants found in soaps and other cleaners

are regulated by the FDA, where products are tested and examined for public health and

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safety (w6). While many disinfectants pass through government agencies for safety

approval, we chose to focus our scope on common household disinfectants.

Product and Consumer Considerations

Household disinfectants must meet several criteria. Besides having anti-microbial

properties and being safe to use around humans and the environment, household

disinfectants are almost exclusively incorporated into a cleaner that provides

multipurpose capabilities, aside from just killing germs. A 1996 Hard Surface Cleaner

Market Study determined that consumers desire cleaners that disinfect, cut grease,

deodorize, and at the same time be cost effective (14). Bathroom cleaners were expected

to remove soap scum and stains while leaving no film or residue (14). Cleaners must

possess a dispersive quality – the ability to be sprayed or spread onto a surface for the

necessary time required for disinfection and cleaning. This often means the incorporation

of surfactants and the use of colloidal properties. Soaps and detergents frequently contain

moisturizers to alleviate the harsh conditions on the skin. Despite these many

considerations in household cleaners, disinfectant and antibacterial properties are among

the most important aspects of cleaners consumers use most often.

While consumers worry about the sterilization capability of cleaners, a distinction

must be made between the degrees of sterilization. Many common household cleaners

are simply antibacterial. Hand soaps and liquid dish detergents contain triclosan, also

known by its trade name Microban, which is strictly an antibacterial (5). Salmonella, E.

coli, and bacteria that cause strep throat and staph infections are typically the common

targets of triclosan. A true disinfectant also kills viruses and other pathogens along with

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bacteria. Alcohols, bleach (sodium hypochlorite), quaternary ammonium compounds,

and certain oils comprise the most familiar household disinfectants. All disinfectants

used in household cleaners must meet EPA or FDA approval. Regulations outlined by

the EPA include stringent tests against Salmonella choleraesuis, Staphylococcus aureus

and other bacteria, along with a performance mandate that in order to be termed a

disinfectant for use on hard materials, the disinfectant must kill on 59 out of each set of

60 carriers and is required to provide effectiveness at the 95% confidence level (w5).

Marketing

The increasing popularity of disinfectants in common household products is a

recent trend. Between 1997 and 1999, manufacturers introduced 700 everyday products

claiming antibacterial or disinfectant properties (5). Disinfectant cleaners make up half of

the $2.1 billion cleanser market in the United States (15). Marketing household

disinfectants is not about convincing consumers to sterilize their homes – studies show

consumers already have this fear. Rather, the effectiveness of the cleaner in cleaning and

disinfecting as compared to other brands is important, along with its relative price

compared to other brands. Brand name cleaners may not necessarily provide a better

product – often generic brands contain the same concentration of active ingredients.

Final product considerations reside in packaging and sales factors. Typical

cleaners sell for $2-$4 for 32 ounces, representing the smaller sample size for household

use (5). Packaging of disinfectants mostly involves the chemically inert plastic bottles

that cleaners are supplied in. Variations exist in the aluminum spray cans for aerosol

cleaners, and now technology is finding ways to introduce disinfectants into other

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mediums. N-halamine structures have been polymerized with a grafting process into

cellulose containing and nylon fabrics, giving everyday materials anti-microbial

properties within themselves (16). Triclosan is also being incorporated into a polymer for

use in fabric seat covers, tables, chairs, and clothing sanitation (9). With so many

methods of incorporating disinfectants into the household and the relative

inexpensiveness of processing these materials, there seems no immediate decline to the

increasing market of disinfectant products.

Components and Compositions of Disinfectants for Household Use

General Components of Cleaning Solutions

There are seven main ingredients found in most household cleansers. These are (in order

of decreasing amount) (w12):

(1) Surfactants: these are amphiphilic molecules which serve several purposes in a

disinfecting cleaner:

a) they adsorb to surfaces, where they aid in loosening and removing soils

b) they hold particles in suspension and prevent redeposition on the surface

c) they cause “wetting” be reducing the surface tension of water and allows it

to spread over the surface

d) anionic (negatively charged) surfactants are best against particulate dirt

and oily soils, but can react with minerals in hard water to form scum

e) cationic (positively charged) surfactants are effective as germicides on

hard surfaces

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f) nonionic surfactants have no charge and therefore are able to work even in

hard water, are low foaming and well-suited for no-rinse applications ().

Surfactants will be treated in greater detail in later sections of this report.

(2) Builders: these compounds are primarily responsible for reacting with hardness

chemicals (such as calcium and magnesium) to keep them from interfering with

surfactant action; in other words, they are water softeners. They can also aid in

keeping soil particles in suspension, and are especially useful in all-purpose

cleaners. These are found in three types:

(a) sequestering builders form tightly-bound, water-soluble

complexes with Ca and Mg ions

(b) precipitating builders form insoluble calcium compounds, which

will then need to be removed from the surface as it is cleaned

(c) ion exchange builders “neutralize” hardness mineral through

electrical charge exchange.

(3) Abrasives: these particles are added to increase the mechanical cleaning ability of

a product. They usually consist of small hard particles. Some examples are

silica, calcite and feldspar.

(4) Acids: these are used to dissolve calcium and metal salts. They are common in

“tub-and-tile” type cleaners used in the bathroom.

(5) Alkalis: these chemicals give cleaning solutions a high pH and help remove solid

grease, as well as providing some building action. Mild alkaline chemicals, such

as baking soda, may be used in products formulated for contact with skin.

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(6) Antimicrobial agents: these are the focus of our report, and are chemicals that

destroy bacteria and viruses, as well as (in some cases) fungi. These agents must

be registered with the EPA before they can be sold. A description of the most

common disinfecting agents follows this section.

(7) Bleaching agents: these components attack dirt by chemical breakdown, normally

via oxidation. Stains are broken down into smaller, colorless forms that are easier

to remove. The most common bleaching agent is sodium hypochlorite, which is

capable of destroying bacteria, viruses and mold.

In addition to these major components, household disinfectant products may contain:

colorants, which provide a purely aesthetic effect; enzymes, which are capable of

breaking down specific organic soils; fragrances, to cover the base odor of the cleaning

solution as well as leave a pleasant, “clean” scent behind; polymers, which can be used in

floor cleaners to provide a shiny, dirt-repelling film after drying, or in more general

cleaners as building or thickening agents; processing aids, which keep the product from

separating during storage and helps give it the desired dispensing characteristics;

preservatives, which protect against bacterial attack; and solvents, which are particularly

useful in the removal of grease without leaving a residue, such as is desired with glass

cleaners.

In the following sections we will describe in greater detail disinfecting chemicals

and surfactants, the two key components in household disinfectants.

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Common Disinfecting Chemicals

Disinfectants for household use are divided into four main subcategories, as

follows: alcohol, chlorine compounds, iodine compounds and quaternary ammonium

compounds. These disinfectants are active at many pH levels. Iodines, for example, are

most effective in the lower pH ranges, from ~2-6, whereas chlorines work best at the

higher end, from 6-10. Quaternary ammonium compounds are the most versatile, with a

working range between 3 and 10.5 (2, Fig 23.1, p.477). For this reason, household products

containing disinfectants are similarly solutions at various pH levels.

Alcohols

One of the most common chemicals present in the

average person’s medicine cabinet is rubbing alcohol. It

is often used as an antiseptic to clean minor wounds, and

also as a hard surface cleaner. Like many chemical

disinfectants, alcohols are generally considered to be

nonspecific antimicrobials. They show a multiplicity of toxic effect mechanisms. This

has important implications for the spectrum, speed and overall effectiveness of alcohol as

a disinfectant. Not all alcohols show bactericidal effect; the amount of inhibition

increases with the chain length of the alcohol (see 10, Table1, p.800).

Chlorine Compounds

Chlorine compounds are some of the most active ingredients in

disinfectants. Use of chlorinated lime as a deodorant for sewage goes as far back

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as 1854 in Great Britain. Calcium hypochlorite has now largely replaced the older

chlorinated lime, and sodium hypochlorite is th emost active principle of many household

products. Various types of algae, bacteria, fungi, protozoa and viruses have shown

resistance to hypochlorites (2, Table 7.1, p.143). The bactericidal action of hypochlorites is

caused by the release of hypochlorous acid and contributions of hypochlorite ions (OCl-).

Hypochlorites are subject to gradual deterioration over a period of time, which depends

on three main factors. The most important factors are the pH and temperature of the

environment. The lower the pH, the less stable the solution, but the more germicidal its

action.

Chlorine dioxide is used a great deal for drinking water and wastewater treatment

(2). It has the ability to break down phenolic compounds and removes phenolic tastes and

odors from water. There are numerous antimicrobial chlorine compounds, but a major

advantage of this particular formulation is that is does not form trihalomethanes (THMs)

or chlorophenols, which are both harmful to the environment and have been coming

under scrutiny by environmentalists making groundwater studies.

The major advantages of chlorine compounds are that they have very fast reaction

times and are effective biocides for a broad spectrum of microorganisms. They are

inexpensive compounds that do not foam, are not temperature dependent, and can be used

in liquid or powder form. The main disadvantages are that chlorine is unstable in

concentrate. It reacts strongly with organic materials and is corrosive to metals. More

importantly, it is unfriendly to the environment.

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IodinesIodine, the heaviest of the common halogens (126.9 g.mol), melts

at 113.5ºC to a black liquid, and is a valuable ingreadient in

antiseptics. Iodine is a highly reactive substance combining with

proteins partly by chemical reations and adsorption. Iodine-based

disinfectants can be divided into three main groups according to the

solvent and substances interacting with the iodine species: pure

aqueous solutions, alcoholic solutions and iodophoric preparations.

They exhibit essential differences in their chemical and microbiocidal properties. The

iodine compounds not only kill microorganisms but also interact with the materials to be

disinfected. To understand these interactions, knowledge about the particular species,

solvent, equilibrium concentrations and individual reactivity is essential.

Iodine ions are often added to increase the solubility of iodine in water. This

increase takes place by the formation of triiodide, I3-. Pure aqueous solutions, for the

iodine-water system, produce at least ten iodine species:

I-, I2, I3-, I5

-, I6-, HOI, OI-, HI2O-, I2O2

-, H2OI+, and IO3-.

The ratio of their formation depends on the concentration of iodine.

Iodophors are polymeric organic molecules, such as alcohols, amides and sugar,

which are capable of forming iodine species. This results in reduced equilibrium

concentrations of species compared with those of pure aqueous solutions with the same

total iodine and iodide concentrations. Since iodophoric preparation always contains

appreciable iodide, the relevant species tat must be considered are restricted to I-, I2 and

I3-, for the following simplified reactions (2, p.168):

I2 + R R.I2

11

I3- + RR.I3

-

I-+ R R.I-

R represents the structural regions of the iodophor molecule capable of forming

complexes by electronic effects.

An important solubilizing agent and carrier for iodine is

poly(vinylpoyrrolidinone) (PVP). PVP-iodine is externally used on humans as an

antiseptic. Some commercial brands are Betadine and Isodine.

Quaternary Ammonium Compounds

Quaternary ammonium compounds are often used in

contact lens solutions for cleaning and preservative purposes.

The antibacterial precursors of the quaternary ammonium compounds (“quats”)

are aliphatic long-chain ammonium salts. The direct counter part of soap may be

considered as a primary ammonium salt. Both are surface-active substances. In soap, the

anion contributes the hydrophobic part and the primary ammonium salt (the cation) is

hydrophobic.

The primary long-chain ammonium salts are derived from the weakly basic

aliphatic amines. Their aqueous solutions require a pH low enough to counteract

hydrolysis and partial liberation of the amine base. Because quats ae salt bases, they

remain in solution in acidic as well as in basic media. Quaternary ammonium salts

produce bacteriostasis in very high dilutions. This property is associated with the

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inhibition of certain bacterial enzymes, especially those involved in respiration and

glycolysis.

Among the many quaternary ammonium salts available, only a small number are

of interest as antibacterial agents. Among them are: benzalkonium chloride,

alkylbenzyldimethylammonium chloride, methydimethyl ammonium chloride,

methylbenzethonium chloride, hexadecylpyridinium chloride, and alkylisoquinolinium

bromide (10).

It is evident from the varied examples of disinfectant chemicals above that we as

consumers have a wide range of products to choose from when it comes to ridding our

homes of germs. Each has specific properties, advantages and disadvantages and it is

important to keep this in mind, as well as the intended use, when choosing an appropriate

cleaning product.

Colloids in Disinfectants: Surfactants

Colloid science is concerned with the study of materials that exist as dispersions

in a medium of some other material. They are sometimes defined as particles that would

remain suspended in water for an extended amount of time. A colloid differs from a true

solution in that the dispersed particles are larger than normal molecules, though they are

too small to be seen with a regular microscope. The typical size of a dispersed particle is

from a few nanometers to several micrometers. One consequence of this small size is a

high surface area, so that the properties of the interfaces may become important. The

common element among all the types of colloids is the fact that they are held in

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suspension by electrostatic interaction with water molecules. Another important

parameter is the thermal motion, which dominates the dynamic properties. Crucial

examples include, food, paint, and household products (12).

Colloids in which the continuous phase is water are classified as follows:

hydrophilic colloids, hydrophobic colloids and association colloids. The first two types

differ from each other by their chemical configuration and/or composition.

Hydrophilic colloids are large molecules that contain functional groups as an

integral part of their structure. The functional groups form hydrogen bonds with water

molecules. Common examples of hydrophilic colloids are proteins and synthetic

polymers. Two examples of hydrophilic colloids are depicted below (11):

Figure 1: Hydrophilic colloids

Hydrophobic colloids are substances that have charged surfaces in water, and

form an electrical "double layer" that holds them in suspension. Clays form a negative

charge on their surface when placed in water, and remain in suspension by the

electrostatic interaction between the negative surface charge and positive charges from

14

cations in the water. The figure below depicts the colloidal clay particles that are

suspended in solution by electrostatic interaction (11).

Figure2: Hydrophobic Colloid

The third type of colloid is an

"association" colloid. These are

molecules that have two parts to their

molecular structure, a hydrophobic part and a hydrophilic part. They are also known as

surfactants. As they are often the most important component present in a cleaning

solution, they will be considered here in more detail.

Soaps and detergents form association colloids in water. Their molecular structure

is similar to the illustration below, where the carboxylic acid group is the hydrophilic

portion and the hydrocarbon chain is the hydrophobic part of the molecule (w8).

Figure3: 'association Colloid

Association colloids are the type that is used in the fabrication of disinfectants

because they possess some germicidal properties. They are also used in cationic

detergents. Association colloids form self-assembly systems. Some examples of these

systems are micelles, reverse micelles, vesicles, micro-emulsions and the monolayers and

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bilayers of some cell membranes. These monolayers and bilayers represent the building

blocks of biomembranes (w2).

The word surfactant describes the activity of the molecule. They are SURFace

ACTive AgeNTs; in other words a surfactant is a molecule that tends to align itself at a

surface or interface. Surfactants fall into four broad categories: anionic, nonionic,

cationic and amphoteric. They are described as being amphiphilic, in a sense that they

have strong attraction towards both polar solvents (hydrophilic) and non-polar solvents

(hydrophobic), and as a result they will concentrate at the interface between the two (11).

Surfactants are often portrayed as having a head and a tail. The head is said to be

hydrophilic, it can either be ionic or non-ionic, and it is usually depicted as a circle. The

tail is said to be hydrophobic and it is generally represented as a long hydrocarbon chain.

The hydrocarbon is “water-hating” which thus means it is “oil-loving”. Normally

surfactants lower the surface tension of water. Schematics commonly used to depict

surfactants are shown below, along with the formula for an actual surfactant (11):

Figure 4: Anionic Surfactant

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Surfactants are often characterized by their configurations. Sodium Oleate is an

example of a molecule that can be classified as surfactant. It is a type of surfactant that is

commonly used in the fabrication of disinfectants. The oleate ion is derived from

triolein, (a triglyceride), by the hydrolization process. It consists of a glycerol with three

ester linkages. Overall, anionic surfactants are the most used in household cleaners, often

in conjunction with non-anionic ones, in order to yield even greater stability in solutions.

Some types of surfactants that are used in disinfectants are:

Sodium palmitate

Sodium myristate

Sodium stearate

Note that the main difference between these surfactants is the carbon chain length. The

implications of this will be discussed in greater detail in the next section.

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Structure-Property Relationships

There are certain characteristics that a disinfectant must possess in order to be

effective. Soiled surfaces, from kitchen counters to bathroom sinks to skin often contain

oily residues. Germs are trapped within these residues, where they are impervious to

washing by water. The presence of organic matter may also impede the disinfectant

itself. Two of the most commonly used disinfecting chemicals are chlorine and

glutaraldehyde. While they have excellent germicidal properties, both are susceptible to

inactivation by organic material (w10). Such organic materials may be part of the “dirt”

itself that one is trying to clean off a surface, or it may be in the form of a biofilm, such

as forms inside of toilets and septic systems.

In order to design an effective disinfectant, one must understand how the

germicide will work in the environment where it will be used. This means that the

interaction between each component of the cleansing agent and the “target” must be

understood. Although the mechanism of germicide action has not been extensively

studied, most scientists hypothesize that the interaction of the chemical agent with the

cell membrane of the microbial species is key. The following an accepted sequence of

events for biocidal activity(19):

(1) adsorption onto cell surface

(2) diffusion through cell wall

(3) binding to the cytoplasmic membrane

(4) disruption of the cytoplasmic membrane

(5) release of cytoplasmic constituents

(6) cell death

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Taking this as a model for the way common germicides act, we would like to understand

how this mechanism is aided by the addition of colloidal components to disinfectant

solutions.

Glover, et al (7) lists several reasons why surfactants are commonly used in

household disinfectants. These include their ability to penetrate soil, solubilise fatty

materials, wet surfaces, and their contribution to the biocidal action of the disinfectant.

We may split these into two broad categories; one, encompassing the first three properties

above, can be termed surface action, the other, increasing germicidal activity. Although

it has been shown by some research groups that there is actually a relationship between

surface properties and germicidal activity (as will be discussed later), this is a convenient

way to separate the two main characteristics of interest.

Although we have made two distinct categories above, little is actually known

about how colloids, and surfactants in particular, act within cleaning solutions. Chen, et

al, showed that three surfactants commonly used in household products—SDS, Tween 20

and Triton X-100—are effective in the removal of biofilms from surfaces (3). The key to

their research was in studying how biofilms are removed, regardless of whether the

bacteria present within the film were killed. They conclude that biofilm cohesion is

governed by multiple forces, and suggest that the efficacy of surfactants to film removal

might be due to “the disruption of hydrophobic interactions involved in crosslinking the

biofilm matrix”(3). In addition, it was noted that the removal of a biofilm is distinct from

the killing of bacteria.

Chen’s findings are important in that they elucidate one important role a

surfactant can play in cleaning: the presence of organic residue or biofilms may make

19

bacteria impervious to many disinfecting chemicals, but by adding surfactants to these

chemicals the residues can be more easily penetrated or removed altogether.

Glover, et al (7), tackled the other side of the problem by studying how surfactants

affect bacterial cells. They looked at several classes of surfactants—cationic, anionic,

non-ionic and amphoteric—to try and determine how the surfactant structure affects its

interaction with microbes. Their hypothesis stemmed from knowledge about the action

of cationic surfactants. Quaternary ammonium compounds, which are extensively

researched surfactants with known bactericidal effects (7), are cationic. It has been

proposed that they kill cells by changing the permeability of the cell membrane. Starting

from this hypothesis, Glover sought to correlate changes in the cytoplasmic membrane to

the biocidal activity of surfactants.

As expected, it was found that all four types of surfactant increased the fluidity of

the cell membrane by a significant amount. However, they could find no correlation

between this increased fluidity and biocidal activity, which they found varied depending

on the type of organism involved (7). This led them to conclude: “perturbing the fluidity

of the cell membrane is not immediately responsible for cell death.” Therefore, when a

surfactant used in a disinfecting solution greatly increases the bactericidal activity of the

solution it is not necessarily because the surfactant is killing microbes. More likely,

when the surfactant disrupts the membrane of the cell, it makes it vulnerable to the action

of the accompanying disinfectant. This is in agreement with Glover’s conclusion that

amphoteric and non-ionic surfactants, which showed high membrane disruption but little

germicide activity, would show great adjutant ability with disinfectants.

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In addition to their conclusions about how surfactants disrupt cell function,

Glover et al made an important mechanistic conclusion about how the surfactant disrupts

the cell membrane structure; they proposed that the increase in membrane fluidity was

caused by the surfactant interfering with the packing of the phospholipid hydrocarbons

that form the membrane’s lipid bilayer. This conclusion is supported by Oros, et al (13),

who studied in much greater detail the structure-property relationship governing the

interaction of surfactants with cells.

It is believed that both the length of the polar chain and the type of hydrophobic

group affect the activity of surfactants in cell disruption (13). Oros, et al, sought to

explore this more thoroughly, noting that a large range of activity could be seen in

surfactants even when the hydrophobic group was the same. This would imply that the

chain length was as or more important to cell interaction than the hydrophobic moiety.

They compared surfactants containing polar ethylene oxide chains of varying lengths to

those having none. In their study, they found that the polar chain length was the primary

determinant of biocide activity. For surfactants containing no polar chain, the total length

of the surfactant was smaller than the width of the lipid bilayer in the cell, and any

surfactant reaching the membrane was enveloped with no apparent effect to the cell.

When the chain length was too long, it interacted strongly with water outside the cell and

therefore preferentially stayed in the solvent and did not enter the cell. The only

surfactants capable of effectively disrupting the cell membrane were those containing

ethylene oxide chains of the same length order as the membrane bilayer. These

molecules were readily incorporated into the membrane, where the hydrophobic end

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interacted with the alkyl chains of the fatty acids while the ethylene oxide chain

interacted with the phospholipid head groups (see figures below).

Figure 7a: Schematic of cell membrane showing lipid bilayer.

Figure 7b: Surfactants with small or no polar tail enter the lipid bilayer and are

contained without affecting membrane function.

Figure 7b: Surfactants with an ethylene oxide tail with length on the order of the bilayer interact

strongly with both polar and hydrophobic groups, resulting in membrane function disruption.

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Viscardi, et al, studied the properties of some novel cationic surfactants based on

glucose (17). Although the impetus for this study was an interest in environmentally

benign surfactants, they elucidated some important structure-property relationships.

They were able to show a correlation between a surface property of the surfactants,

namely, the critical micelle concentrations (cmc), and the biocidal activity. It was shown

that as the cmc decreases, the ability to kill bacteria increases. Their explanation was that

antibacterial activity is closely related to cell adsorption, and therefore to hydrophobicity.

The more hydrophobic the surfactant, the smaller the cmc, and the more “eagerly” it

attaches to the cell wall of the bacteria.

Another interesting property of glucose-containing surfactants is that by

modifying the number of glucose molecules that are added, one can tune the polarity of

the molecule. This will affect the surface properties by affecting the shape the micelle

can take, which in turn affects how the surfactant interacts with microbes.

The papers cited above have shown how surfactants can be important components

in household cleaning products, as the properties they possess due to their amphiphilic

nature can clearly aid the action of disinfectants.

Disinfectants of the Future: Current Research

As the public becomes more concerned with the environmental fate of widely

used household chemicals, the race is on in industry to find cheap, effective and

environmentally benign disinfecting chemicals. This is one reason knowing the

structure-property relations of all the components in a cleaning solution are so important.

In the case of biocide activity, some important research is currently going on to study

polymers as possible substitutes or modifiers of current disinfecting chemicals. The

main problem with disinfectants, from an ecological standpoint, is that they are low-

molecular weight compounds that are easily find their way into the soil and water supply

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and readily react to form toxic byproducts. Eknoian, et al, and E.R. Kenawy (18, 19) have

both published papers examining the modification of polymers with active groups that

lend the polymer biocidal action. This has two positive effects: first, the ecological

problem is removed. Polymers can be partially or not at all soluble in water, tend to be

non-volatile, chemically stable compounds and are slow to permeate the skin. Secondly,

they show promise in actually improving biocidal activity. Permanently bound bioactive

groups have been shown to be more effective, and polymers with such modifiers have

application not only in cleaning solutions, but also as coatings to various materials that

will act as a shield to prevent colonization by bacterial species. Some of these advances

are already being seen, one example being the “self-cleaning windows” set to go on the

market this year, which employ a polymer coating and photo-biocatalysis to raise the bar

on the ease and effectiveness of home cleaning.

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17. Viscardi, G, P. Quagliotto, C. Barolo, P. Savarino, E. Barni and E. Fisicaro, “Synthesis and Antimicrobial Properties of Novel Cationic Surfactants,” Journal of Organic Chemistry, 2000, 65, 8197-8203.

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18. Eknonian, M.W., J.H. Putman, and S.D. Worley, “Monomeric and Polymeric H-Halamine Disinfectants,” Industrial Engineering Chemical Research, 1998, 37, 2873-2877.

19. E. R. Kenawy, “Biologically Active Polymers. IV. Synthesis and Antimicrobial Activity of Polymers Containing 8-Hydroxyquinoline Moiety,” 2001, Journal of Applied Polymer Science, Vol. 82, 1364-1374.

Web References:w1. http://www.epa.gov/oppad001/sciencepolicy.htmw2. http://ehpnet1.niehs.nih.gov/docs/1995/103-1/focus1.html

w3. http://www.fda.gov/cdrh/ost/reports/fy98/INFECTION.HTMw4. http://www.messina-oilchem.com/Stimulation/Stimulation-S.html w5. http://www.ch.kcl.ac.uk/kclchem/staff/arr/abs.htm#Ref_P97w6. http://jan.ucc.nau.edu/~doetqp-p/courses/env440/env440_2/lectures/lec19/lec19.html

w7. “Biosecurity: Selection and Use of Surface Disinfectants”www.cdfa.ca.gov

w8. “Clean Smarter, Not Harder”www.clorox.com/health/cleansmart/cleansmart5.html

w9. www.microcideinc.com/silkyfaq.htm

w10. Biosafety Program, University of Virginiahttp://keats.admin.Virginia.edu/bio/disinfectant_summary.html

w11. J. Eliz, “How does chlorine added to drinking water kill bacteria and other harmful organisms?” Scientific American “Ask the Experts”www.sciam.com/askexpert/environment/environment22/environment22.html

w12. “Facts About Household Cleaning”http://www.cleaning101.com/house/fact/houseclean5.html

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