Colloid and Surface Science Aspects in Disinfectants Reginald Jacques Garret Lau Carla Ng Pintu Saha University at Buffalo, Department of Chemical Engineering

Overview Major Uses The Disinfectant Market Product Considerations Disinfecting Agents Colloids in Disinfectants Interactions and Structure-Property Relationships Disinfectants of the Future

What is a disinfectant? Agent that kills actively growing micro- organisms (bacteria, viruses, fungi, etc.) but does not kill their spores. Purpose – prevention of sickness caused by these microorganisms.

Application of Disinfectants Food industry – sanitize food preparation areas, preservative functions Drinking water – typically chlorine, other organic oxidizers Medical – sterilization of equipment, facilities Household – cleaners (kitchen, bathroom, multipurpose), soaps, detergents Other industries – paints, inks, cosmetics (serves as preservative)

Product Specifications Selective toxicity – want to kill bacteria, viruses, other pathogens; remain safe to humans and general environment Government regulations – must abide by rules and regulations imposed by EPA, FDA Household considerations  multipurpose products: disinfectant combined with surfactant for grease removal, or moisturizers as in soaps  dispersive quality: aerosol or spray for coverage and adhesion to hard surfaces (countertops, bath, toilet, etc)

Further Considerations Marketing - Between , manufacturers introduced 700 new antibacterial or disinfectant products; half of $2.1 billion cleanser market in US; bacterial resistance? Cost ($2-$4 for 32 oz. Shower cleaner) – compare active ingredient of brand names with generic Processing/Packaging – liquid detergents, soaps (plastic bottles); aerosol spray (aluminum cans); polymerized disinfectants (chemically incorporated into fabric or material)

Ingredients of Disinfecting Cleaners Builders: Tie up the hardness minerals in water so they do not interfere with the cleaning action of the surfactant  Builders are subdivided into into three categories: Sequestering, precipitating and Ion exchange builders. Abrasive: Contribute to the mechanical effectiveness of scouring cleanser; consist of small mineral particles. examples: Silica, feldspar, calcite Acids: Dissolve calcium and metal salt in tub, tile, sink and toilet bowl cleaners.  Type of acids: Phosphoric, Hydrochloric, hydroxyacetic acids Alkalis: maintain pH at a desirably high level during cleaning; play a crucial role in removing solid grease.  Types of alkalis are: sodium Hydroxide, Sodium metasilicate, sodium carbonate

Other important ingredients Antimicrobial agents: Destroy bacteria and viruses, by interfering with their metabolism or destroying their cell walls.  Examples: Alcohol, sodium hypochlorite, iodine, pine oil etcetera. Bleaching agents: Oxidize the soil and stain to a more easily removable form. Attack the soil and destroy bacterial viruses and mold.  Sodium hydroxide is very effective for that purpose. Colorants: Give an appealing characteristic to the product, can also be tracers. Enzymes: Break down the soil into a simpler form that can be removed. Polymer: They are very helpful in floor care product, they protect the surface and provide shine.

Other important ingredients Processing aids: keep the product homogeneous under different storage conditions.  Most used processing aids are: Clays, polymers, Sodium Silicate and Sodium Sulfate Preservatives: Protect the product against decay, discoloration,oxidation and bacterial attack  Typical preservatives include:butylated hydroxy toluene, glutaraldehyde and so on. Organic solvent: Help in removing spots without leaving any residue.

Type of colloids Hydrophobic Colloids: is a colloid in which there is a strong attraction between the dispersed phase and the continuous phase (water ) Hydrophilic Colloids: is a colloid in which there is a lack of attraction between the dispersed phase and the continuous phase (water) Association Colloids: They are described as molecule that has two part in their configuration., a hydrophobic part and a hydrophilic part

Association Colloids Mainly used in the fabrication of disinfectant Examples of this type of colloid: micelles, reverse micelles, vesicles, micro-emulsions.

SURFace ACTive AgeNT They are often portrayed as having a head and a tail. Molecule that adsorbs at the surface and/or interface. They are described as being amphiphilic. Types of surfactants : anionic, cationic, nonionic, amphoteric.

Anionic Surfactant Are used in the fabrication of disinfectant They are used all over the place, and their composition represent almost half of all the other surfactant are made of. They are sometimes used in conjunction with nonionic to provide greater stability. Type of nonionic surfactants that are used in disinfectant are :  Fatty acids (soaps): Sodium Oleate, Sodium Palmitate, Sodium Myristate etcetera.  Alkyl Sulfates: Sodium Dodecyl Sulfate (SDS)  Other commonly used Anionic Surfactant: Alkyl Benzene Sulfonates, 2-Alkyl Phosphate, Sodium di(2- ethylhexyl) Sulfosuccinate (Aerosol-OT) Long term exposure can lead to skin irritation

Main Components and Compositions of Disinfectants for Household Alcohol Compounds Chlorine Compounds Iodine Compounds Quaternary Ammonium Compounds

Alcohols Inhibition increases with the chain length. Methyl Alcohol –Not included in most household goods. Ethyl Alcohol –Effective germicide for vegetative pathogens Isopropyl Alcohol –Effective germicide for an antimicrobial agent Products Food Health Care Products

Chlorine Compounds Antibacterial action of chlorine compounds dependent upon their capacity for releasing “active” chlorine Sodium Hypochlorite Chlorine Dioxide Products Drinking Water Cleaners

Iodine Compounds Aqueous Solutions Alcoholic Solutions Iodophric Preparations Products Drinking Water Health Care Products {Antiseptic}

Quaternary Ammonium Compounds Aliphatic long-chain ammonium salt Owe their surface activity and antibacterial qualities primarily to the presence of aliphatic long-chain amino groups. Products Contact Lens Solution

Designing an Effective Disinfectant Know your dirt –What type of surface? Soil effect on disinfectant action: –Oily residues are impervious to water and often contain germs. –Bacteria can form biofilms to protect against attack. Consumer considerations –Fragrance –Irritants –Environmental Concerns

Overcoming Biofilms and Organic Residues Disinfectants disrupt bacterial cell function. Many common disinfectants are effective biocides, but are inactivated by organics. Components must be added to aid disinfectants in reaching and affecting bacterial cells  Surfactants

Mechanism of Antibacterial Activity Adsorption onto cell surface Diffusion through cell wall Binding to the cytoplasmic membrane Disruption of the cytoplasmic membrane Release of cytoplasmic constituents Cell death

How Surfactants Aid Disinfectants Surfactants can help by: –Removing surface residues and biofilms –Aiding the germicide action of disinfectants Some surfactants are biocides themselves. Surfactants can facilitate disinfectants by disrupting the bacterial cell membrane.

Structure-Property Relationship Structure of surfactant will dictate how it interacts with bacteria. Example: Surfactants containing polar ethylene oxide chain: –Chain too small, no disruption –Chain too long, no disruption –Chain same order as lipid bilayer, cell membrane disruption  cell death.

Structure-Property (continued) Critical Micelle Concentration (CMC) and germicidal activity are linked: CMC antibacterial properties CMC related to hydrophobicity, charge distribution, molecule shape. These characteristics affect the interaction of surfactant with microbial cell.

Disinfectants of the Future Understanding what makes disinfectants work leads to new improved formulations: –Environmentally friendly disinfectants glucose-based cationic surfactants –Polymers as disinfectants disinfectant coatings insoluble disinfectants

QUESTIONS?