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Science Fair Project
Transcript of Science Fair Project
Science Fair Project
Can Silver Nanoparticles Neutralize E. coli Bacteria?
Background Research Diagram/Model/Visual
Harmony Science Academy - Euless
8 - Harvard
2014 - 2015
Pictures of Procedures and Results
: •Graduated cylinder, 10 mL.
•Graduated cylinder, 25 mL.
•Filter papers/coffee filter papers
•Forceps or tweezers
•Nutrient agar, prepared media plates 100 x 15 mm (5 plates).
•Sterile cotton-tipped applicators, or swabs.
•Escherichia coli (E. coli) K12 (one tube).
•Disposable gloves (2 pairs).
•70% isopropyl rubbing alcohol
• Glass or plastic cups/jars
•Distilled water (90 mL).
•Natural Path Silver Wings Dietary Mineral Supplement, colloidal silver, 500 PPM (25 mL)
•10% bleach solution
•Optional: Digital camera and a sheet of black construction paper
1 - Find a clean counter or table to work on. Make sure you have everything you will need and that all of the items are clean.
2 - Put on a pair of disposable gloves.
3 - Make a paper towel damp with some 70% isopropyl rubbing alcohol. Wipe down the work surface with the rubbing alcohol-dampened paper towel.
4 - Using a permanent marker, label the five plastic cups #1 to #5.
5 - Perform a 1:10 serial dilution of the colloidal silver. The concentrations you will be making and testing are 500,000 µg/L (undiluted), 50,000 µg/L, 5,000 µg/L, 500 µg/L, and 50 µg/L.
6 - When you have finished preparing the serial dilutions, immediately start the next section of the procedure.
7 - Punch 15 circles from a filter paper (or coffee filter paper) with the hole punch.
8 - Using clean tweezers, place three filter paper circles (that you just punched with the hole punch) into each plastic cup (#1 through #5).
Let them soak until you need them in future steps.
9 - Lay out five of the nutrient-agar prepared media plates. Place the plates upside down on the clean counter or table and use the permanent marker to label the back of each one, #1 through #5.
10 - After labeling them, flip the plates over so that the lid is on top.
11 - Take off your gloves and put on a new pair of disposable gloves.
12 - Sterilize the tweezers by dipping them into 70% isopropyl rubbing alcohol for about 10 seconds. Then remove the tweezers from the alcohol and wave them in the air for about 20 seconds. Make sure the tweezers are completely dry before moving on to the next step.
13 - Using the tweezers, grab a cotton swab from a new, unopened box of cotton swabs. Only touch one end of it using the tweezers, and do not let the rest of the cotton swab touch anything else.
14 - If you are using standard-sized cotton swabs (which are about 8 centimeters [cm] long), continue to hold the cotton swab firmly by its end using the tweezers. If you are using extra-long, 6-inch cotton swabs, transfer one end of the cotton swab to your gloved hands (only ever touching one end of the cotton swab) and set the tweezers down.
15 - Use the cotton swab to streak the five labeled nutrient agar plates with the E. Coli K12 bacteria from the tube.
Procedure (Part 2)
10 - Place the three filter circles from each numbered cups onto the corresponding plate.
11 - Make sure all plates are closed (with the lids on top). Secure the lid on each agar plate using a few pieces of clear tape.
12 - Flip the plates so that they are upside down (with the agar on the top of each plate).
13 - Leave the plates in a clean, out-of-the-way place in a room where they will not be disturbed for a few days. A good place would be an unused part of a desk or counter. They should not receive direct sunlight, however.
14 - After moving the plates, clean up the area where you spread the E. coli K12 bacteria on the plates. Sterilize the countertop or table surface and anything that touched the E. coli.
15 - Check on the plates every day after starting the experiment. Look for any bacterial colonies. They should look like small, whitish spots.
16 - Look at each plate to see if there is a zone of inhibition around the filter circles.
17 - Flip the plates so that they are upside down and use a ruler to measure the width of any zones of inhibition you see on the plates.
18 - After you finish making observations, sterilize the plates by soaking them in a 10% bleach solution for at least 1 to 2 hours. You can then throw them in the trash.
19 - Analyze your results.
Keep your nose and mouth away from tubes, pipettes, or other tools that come in contact with bacterial cultures, in order to avoid ingesting or inhaling any bacteria.
Make sure to wash your hands thoroughly after handling bacteria.
Proper Disposal of Bacterial Cultures:
Bacterial cultures, plates, and disposables that are used to manipulate the bacteria should be soaked in a 10% bleach solution (1 part bleach to 9 parts water) for 1 to 2 hours.
Use caution when handling the bleach, as it can ruin your clothes if spilled, and any disinfectant can be harmful if splashed in your eyes.
After bleach treatment is completed, these items can be placed in your normal household garbage.
Cleaning Your Work Area
At the end of your experiment, use a disinfectant, such as a 10% bleach solution, to thoroughly clean any surfaces you have used.
Be aware of the possible hazards of disinfectants and use them carefully.
For centuries, silver has been used as a antibacterial agent. “ The Phoenicians stored water and other liquids in silver coated bottles to discourage contamination by microbes. Silver dollars used to be put into milk bottles to keep milk fresh, and water tanks of ships and airplanes that are "silvered" are able to render water potable for months . In 1884 it became a common practice to administer drops of aqueous silver nitrate to newborn's eyes to prevent the transmission of Neisseria gonorrhoeae from infected mothers to children during childbirth.” (Garduque, 2013).
Although the use of silver as a antibacterial agent decreased once antibiotics were discovered, recently its use has been renewed due to the availability of new laboratory technologies, such as radioactive isotopes and electron microscopy. These technologies have enabled researchers to investigate the antibacterial mechanism of silver in greater depth. “Scientists currently believe that silver ions (individually charged atoms) can interrupt important chemical bonds in bacteria, therefore disrupting important cellular functions that bacteria need to live.” (Rowland and Truong, 2014)
Many consumer products advertise that they contain silver nanoparticles (commonly known as nanosilver), silver salts, or silver zeolites, but silver nanoparticles are the most commonly used. A nanoparticle is usually only a few nanometers wide, and never exceed 100 nanometers in width. A nanometer is one billionth of a meter.
‘Consumer products containing nanosilver are labeled as containing “colloidal silver”, which is a mixture of silver nanoparticles and silver ions.’ (Rowland and Truong, 2014) Some of these products include wound dressings, endotracheal tubes, surgical masks, cotton fibers, drinking water, glass, and food packaging.
Terms and Concepts
Antibacterial - destructive to or inhibiting the growth of bacteria.
Antimicrobial - destructive to or inhibiting the growth of microorganisms.
Ions - an atom or molecule with a net electric charge due to the loss or gain of one or more electrons.
Nanoparticles - a microscopic particle of matter that is measured on the nanoscale, usually one that measures less than 100 nanometers.
Nanometer-one billionth of a meter.
Nanosilver-group of micro-sized (nano) bits of silver that are either covering or suspended in an item. A nano is about the size of 6 atoms lined up together.
Colloidal silver- a suspension of microscopic particles of silver, usually in water
Escherichia coli (E. coli)- a species of rod-shaped, facultatively anaerobic bacteria in the large intestine of humans and other animals, sometimes pathogenic.
Kirby-Bauer antibiotic testing method - a method for testing the antimicrobial susceptibility of bacteria based on the size of zones of inhibition of growth of a lawn culture around disks impregnated with the antimicrobial drug.
Zone of inhibition - a circular zone around a disc containing an antibiotic, for example, in which the growth of bacteria susceptible to the antibiotic is inhibited.
Serial dilutions - is the stepwise dilution of a substance in solution
Sterile technique - any health care procedure in which added precautions, such as use of sterile gloves and instruments, are used to prevent contamination of a person, object, or area by microorganisms.
Parts per million (PPM) and micrograms per liter (µg/L)
Nameth, Catherine, and Christine Truong. "Tiny Titans: Can Silver Nanoparticles Neutralize E. Coli Bacteria?" Tiny Titans: Can Silver Nanoparticles Neutralize E. Coli Bacteria? Ed. Teisha Rowland. N.p., n.d. Web. 13 Oct. 2014. <http://www.sciencebuddies.org/science-fair-projects/project_ideas/MicroBio_p031.shtml>
Garduque, Gian. "Silver as an Antimicrobial Agent." - MicrobeWiki. N.p., n.d. Web. 12 Oct. 2014 <http://microbewiki.kenyon.edu/index.php/Silver_as_an_Antimicrobial_Agent>
University of Alberta. (2010, April 16.) Nano-silver wound dressings earn Manning Innovation Award. Retrieved October 12, 2014, from
Benn, T. M., and Westerhoff, P. (2008, March 24.) Nanoparticle silver released into water from commercially available sock fabrics. Environmental Science & Technology. Retrieved October 12, 2012, from http://www.sludgenews.org/resources/documents/benn_nanosilver.pdf