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Document 4: Post-1950 Miscellaneous Sources

May 3, 2004

Robert C. Holladay, MS

Copyright 2004 Robert C. Holladay

 

(1) Yazar, Sahin and Erdal Basaran.  1994.  Efficacy of silver nitrate pencils in the treatment of common warts.  Journal of dermatology.  21: 329-333.

            “Therefore, this method appears to be an effective, economic, and easily applicable treatment for common warts”.

 

(2) Liau, S.Y.  1997.  interaction of silver nitrate with readily identifiable groups: relationship to the antibacterial action of silver ions.  Letters in Applied Microbiology.  25: 279-283.

            the results imply that interaction of Ag+ with thiol groups plays an essential role in bacterial inactivation”.

 

(3) Spadaro, J.A. et al.  1979.  Silver polymethyl methacrylate antibacterial bone cement.  Clinical Orthopaedics and Related Research.  143: 266-270.

            Four silver salts and chlorided silver were mixed with bone cement and tested for antibacterial effectiveness.  Ag2O and Ag2SO4 proved to be the most effective followed by Ag3PO4, AgCl, and chlorided silver.  Chlorided silver and AgCl were ineffective after 1 day, whereas Ag2O was effective after 4 days, Ag3PO4 was effective after 8 days, and Ag2SO4  remained effective for 49+ days.

           

(4) Brown, M.R.W. and R.A. Anderson.  1968.  The bactericidal effect of silver ions on Pseudomonas aeruginosa.  Journal of Pharmacy and Pharmacology.  20: Supplement 1S-3S.

            silver ions are less effective at lower pH suggesting competition between metal cations and hydrogen ions for anionic sites on the bacteria”.

 

(5) Ritchie, J.A. and C.L. Jones.  1990.  Antibacterial testing of metal ions using a chemically defined medium.  Letters in Applied Microbiology.  11: 152-154.

            In vitro tests using germicides can be significantly affected by the culture medium.  Agar has a negative charge and will bind to cations.  An experiment was performed in which bacteria cultured in two different mediums were exposed to silver ions.  The MIC of bacteria cultured in BHI was 40-300 times higher than the MIC of bacteria cultured in a chemically defined medium.

 

(6) Tilton, Richard C. and Bernard Rosenberg.  1978.  Reversal of silver inhibition of microorganisms by agar.  Applied and Environmental Microbiology.  35(6): 1116-1120.

            “Three common agar media were tested for their ability to neutralize the bacteriostatic effects of silver.  Results suggested that growth media differed in their neutralizing capacity; that is, the non-inhibitory media tryptone glucose agar and Trypticase soy agar showed more neutralizing capacity than eosin methylene blue agar.  Furthermore, the neutralizing effect appeared to be a function of the soluble component of the media and not of the agar itself…the neutralization of Ag+ activity is a function both of the chelating substances in the agar medium and of the thioneutralizer added to the inoculum before plating… Evidence now exists in a number of laboratories that other factors are involved in the neutralization of Ag+ subsequent to bacterial exposure.  They include: presence of amino acids, hardness of water, phosphate and chloride content, temperature of incubation, type of buffer, light, bacterial density, and salt content of the growth medium…Claims of silver resistance in microorganisms should now be examined in light of the effects of nutrient media on the ability of silver to inactivate bacteria”.

 

(7) Gravens, Daniel L. et al.  1969.  Silver and intestinal flora.  Archives of Surgery.  99: 454-458.

            Intestinal bacteria resistant to silver were found in patients who received silver sulfadiazine treatments.

 

(8) Pledger, Richard A. and Hubert Lechevalier.  1956.  Study of cross resistance between a mild silver protein and antibiotics.  Antibiotics and Chemotherapy.  6: 120-124.

            A study of cross resistance was performed with Staph. aureus, Ps. Flourescens, and Ps. Aeruginosa.  Mild silver protein, Neomycin, Bacitracin, and Polymyxin B were antibacterial agents used.  “It was more difficult to obtain strains resistant to mild silver protein than to the antibiotics.”  Cross resistance was seen.

 

(9) Gruen, L. Clem.  1975.  Interaction of amino acids with silver(I) ions.  Biochimica et Biophysica Acta.  386: 270-274.

            “The reactivity of silver(I) ions towards twenty amino acids has been studied in aqueous unbuffered solutions using an ion-selective electrode as a highly sensitive monitor.  Contrary to general belief, silver ions are not completely specific for cysteine, but also react with lysine, arginine, methionine and, to a minor extent, cystine.”

 

(10) Ziyaev, Sh. I.  1964.  The effects of intravenous administration of colloidal silver on the metastasis of Brown-Pearce carcinoma transplanted into the testicle.  Biulleten Eksperimental Noi Biologii I Meditsiny.  57: 92-93. 

            “Three-fold intravenous administration of colloidal silver produced an inhibitory effect on the process of Brown-Pearce carcinoma metastasis following its transplantation into the testicle.  Observations over rabbits were carried out for 20 and 30 days.”

Comment: Russian with English abstract.

 

(11) Marino, A.A. et al.  1974.  The effect of selected metals on marrow cells in culture.  Chemico-Biological Interactions.  9: 217-223.

            Mouse bone marrow was placed in silver, platinum, or stainless steel dishes.  Wires made of the same metal were placed in the dishes, and an electric current was applied to the wires.  “After 24 h, mouse marrow cultured on silver showed a significant decrease in the percentages of immature granulocytic and erythroid cells, and a significant increase in the percentage of mature granulocytic cells”.

 

(12) Yago, Ayako, Ryuko Shirasaka and Noriko Akagami.  1978.  [Effects of silver carbon on eliminating mouse hepatitis virus in water.]  Japanese Journal of Hygiene.  33: 647-652.

            Granules of carbon with an average diameter of 1 mm were injected into mice with mouse hepatitis virus, and the survival rate was increased.  Some granules of carbon were coated with silver and then injected into the mice with mouse hepatitis virus, and the survival rate was increased.  When the mouse hepatitis virus was filtered through 12 g of silver before it was injected into the mice, the survival rate was dramatically increased.

 

(13) Shi, yan and Kenneth L. Rock.  2002.  Cell death releases adjuvants that selectively enhance immune surveillance of particulate antigens.   European Journal of Immunology.  32: 155-162.

            Cell death and injury stimulate the immune system when foreign proteins can be detected.

 

(14) Shi, Yan, Wanyong Zheng and Kenneth L. Rock.  2000.  Cell injury releases endogenous adjuvants that stimulate cytotoxic T cell responses.  Proceedings of the National Academy of the Sciences.  97: 14590-14595.

            Cell death and injury stimulate the immune system.

 

(15) Galluci, Stefania, Martijn Lolkema and Polly Matzinger.  1999.  Natural adjuvants: endogenous activators of dendritic cells.  Nature Medicine.  5: 1249-1255.

            Cells which die as a result of necrosis stimulate the immune system, whereas cells which die from apoptosis do not.

 

(16) Antelman, Marvin S.  1994.  Silver (II, III) disinfectants.  Soap/Cosmetics/Specialties.  March: 52-59.

            Silver oxide, AgO, is commonly referred to as Ag(II) oxide.  Researchers in the 1960s determined that the actual molecular formula of silver oxide is Ag4O4 with 50% of the silver atoms having a charge of +1 and the other 50% having a charge of +3. 

            Experiments were performed in which Ag(II) and (III) disinfectants were shown to be 50-200 times as effective as Ag(I) compounds or metallic silver.  Ag(III) works 240 times faster than Ag(I).

 

(17) Antelman, Marvin S.  1994.  U.S. patent 5336499.

            According to the Merck Index (11th edition), silver oxide is designated as silver (II) oxide, AgO, but also states that it is a silver(I)-silver(III) oxide with a molecular weight of 123.88.

            Silver oxide is active against a wide variety of microbes.  An in vitro experiment  was performed in which 75% of AIDS viruses were killed in a solution of 10 ppm silver oxide.  Particle size was not mentioned.

 

(18) Antelman, Marvin S.  1997.  U.S. patent 5676977.

            40 ppm silver oxide was injected intravenously in AIDS patients.  White blood cell count was increased, and the patients suffered from enlarged livers, an increase in temperature, and fatigue. 

 

(19) Antelman, Marvin S.  2001.  U.S. patent 6258385.

            Silver oxide applied to the skin can be used on humans to treat eczema, psoriasis, dermatitis, ulcers, shingles, rashes, bedsores, cold sores, blisters, boils, herpes, acne, pimples and warts.

 

(20) Antelman, Marvin S.  2002.  U.S. patent 6485755.

            Silver and other metal oxides administered to humans through injections or topically can be used to successfully treat cancer.  Silver oxide concentrations of 10 ppm were obtained by intravenous injections lasting 10 minutes.        

 

Comment on the Antelman patents:  I am intrigued with the Antelman patents and I plan on pursuing the matter some time in the future. (sources in Document 5 describing the injection of colloidal lead were included to help asses the possibility of injecting CS)   It appears that none of the experiments listed in these patents have been published in the peer-reviewed literature (except for the Catalysis Today 1997 article summarized in Document 1, reference 4) and should be viewed with an appropriate degree of skepticism.  The patents can be viewed online using the U.S. patent database that can be found by going to most search engines and typing in “US patent database.”  In my literature review I have encountered numerous articles which indicate that prior to 1950, silver oxide was widely used as an antimicrobial agent.  Large portions of these patents would probably be declared invalid if they were challenged.  

 

(21) Hall, Richard Everett.  1984.  In vitro effects of silver salts and silver generated from electrodes by low intensity direct current (LIDC) silver on prokaryotic and eukaryotic cells.  Dissertation.  231 pages.

            Unless otherwise stated, the bacteria used in these experiments were cultured in Tryptone-Marmite-Glucose (TMG). 

            Silver generated by low intensity direct current (LIDC Ag) was generated by placing silver electrodes in a dish containing TMG medium, and electric current was applied to the electrodes.  The TMG medium with silver was then added to a different dish containing TMG until the desired silver concentration was attained.  Following that, the microbes were added to the mixture.

            (1.1) LIDC Ag, silver nitrate and silver sulfate were added to TMG medium containing various bacteria in concentrations of 0 ppm, 1 ppm, 5 ppm, 10 ppm, and 20 ppm.  LIDC Ag was usually bacteriostatic, but occasionally bactericidal.  Generally with 20 ppm concentrations, there was a period of “lag time” lasting 12 hours in which no growth of the organisms was seen.  After 48 hours the bacterial levels in each dish was nearly  identical.  LIDC Ag demonstrated a slightly longer “lag time” than the 2 silver salts on a consistent basis.

            (1.2) Minimum inhibitory levels (MIL) for up to 165 hours, and minimum lethal levels (MLL) were determined for 9 different bacteria using LIDC Ag.  The MLL for E. coli B and P. aeruginosa was greater than 50 ppm.  MLL levels for all other bacteria were less than 50 ppm.  MIL for all bacteria was less than 50 ppm.  Inhibitory levels were much higher than those seen by Berger.

            (1.3) Silver electrodes were placed in TMG medium containing bacteria and current was applied.  Antibacterial action of silver was more effective with concurrently applied electricity.

            (1.4) Methionine was added to LIDC and inhibited its antibacterial ability.

            (2.0) Experiments were performed which indicated that silver ions form complexes with organic medium constituents when silver ions are placed in organic medium such that very little or no free silver ions are left.

            (3.1) Experiments were performed which showed that bacterial cell membranes can absorb massive amounts of silver from silver nitrate.  Cells suspended in deionized water absorbed more silver than cells in TMG medium. 

            (3.2) Potassium is the most abundant intracellular cation.  When a cell membrane is ruptured, potassium flows out of the cell.  Bacterial exposure to 5 ppm silver nitrate in 0.1 M sodium phosphate buffer resulted in a 90% reduction of intracellular potassium, while 5 ppm exposure to LIDC Ag in TMG did not affect potassium levels.

            The addition of 1-10 ppm Ag from silver nitrate hindered bacterial protein synthesis while 20 ppm from silver nitrate essentially halted protein synthesis.  The addition of 20 ppm silver nitrate did not affect valine uptake, but it did inhibit incorporation of the amino acid into acid preciptable polymers.  These experiments were repeated with LIDC Ag and similar results were obtained.

            Regarding RNA synthesis, 20 ppm LIDC Ag inhibited uracil uptake by 50% after 30 minutes of incubation, while silver nitrate inhibited uracil uptake by over 90%.

            Incorporation of uracil into RNA was greatly hindered by 20 ppm LIDC Ag and silver nitrate.

            At 20 ppm, DNA synthesis was greatly inhibited by both LIDC Ag and silver nitrate after 20 minutes.

            (4.1) MIC of silver ions for yeast was similar to that of bacteria.

            (4.2) The protozoan tested was extremely sensitive to LIDC Ag and silver salts, with little difference between the two.  5 ppm yielded no survivors, and 1 ppm yielded very few survivors.  The cells were bizarrely shaped and many had undergone lysis.

            (4.3) Spadaro (1976) suggested that LIDC Ag can be highly cytotoxic to mammalian cells, whereas Berger (1974, 1976) suggested that mammalian cells are resistant to low level silver toxicity. 

            Attachment and growth of mouse 3T3 fibroblasts was inhibited by LIDC Ag and silver nitrate at concentrations of 2.5-3 ppm depending on culture medium.  Attachment and growth of mouse HeLa cells were inhibited by LIDC Ag and silver nitrate at concentrations of 4 ppm.

            1 ppm Ag from silver nitrate rendered 97% of mouse 3T3 fibroblasts non-viable after 24 hours.

            The cytotoxicity of LIDC Ag and silver nitrate varied with cell concentration.  When 1-5 x 105  3T3 and HeLa cells were exposed to silver, 1-2 ppm was required to produce cell death.  When 2-5 x 106 cells were used, 5.5 ppm Ag was required to produce cell death.

            Cells in fully grown monolayers are less sensitive to LIDC Ag than silver nitrate.

            These results substantiate the results of Berger (1976) that 4 ppm LIDC Ag has little effect on tissue culture cells.

            (4.4) Bacteria cultured in DMEM were far more sensitive to silver nitrate than TMG; many were inhibited at 1 ppm. 

            (4.5) 25% of fertilized frog eggs were resistant to 100 ppm Ag, possibly due to the jelly coating.

            The jelly coats of free-swimming frog larvae were removed and they were placed in water containing Ag.  They were sensitive to 0.0001 ppm Ag, and death was caused by 0.001 ppm Ag.

            (4.6) The function of human lymphocytes was affected in Ag levels of 1 ppm. Cytotoxicity was not seen at levels of 10 ppm.

            (5.1) Bacteria were cultured in Trypticase Soy Agar (TSA) and exposed to various levels of Ag from silver nitrate.  Silver resistance was rare, however several resistant strains were found.  The initial plates containing resistant strains had only one or two colonies out of 1010 bacteria streaked.  Resistant strains were exposed to Ag until they could grow in the presence of 1000 ppm Ag.  The resistant strains were surrounded by a narrow zone of clear agar (it appeared as if the silver was removed).The resistant cells were sensitive to mercury, but not cadmium.

            (5.2) Resistant strains did not have plasmids, and the genes responsible for resistance are presumably chromosomal.

            (5.3) If silver-accommodated cells were transferred to a non-silvered medium, allowed to grow, and then transferred back to a silvered medium, they demonstrated growth characteristics similar to those of bacteria exposed to silver for the first time.  Therefore the silver-accommodated cells probably adapt physiologically to the presence of silver. 

            Silver-accommodated bacteria were resistant to cadmium, and cadmium accommodated cells were resistant to silver.  Silver tolerance is probably due to physiological adaptation to heavy metals.  These results concur with the existing literature on the topic.  Metal tolerance may be due to metal induced synthesis of heavy metal proteins similar to metallothionenein.

            Bacteria cultured in TMG and fluid from silver-accommodated bacteria demonstrated less susceptibility to silver than cells cultured in TMG and fluid from unaccommodated bacteria.  Silver-accommodated cells probably release agents that protect against silver toxicity.

            When fluid from silver-accommodated and non silver-accommodated bacteria is concentrated and placed with bacteria in TMG, susceptibility to silver was less common in bacteria mixed with fluid from accommodated cultures. 

            Coward (1973, 1975) has proposed that cells can become resistant to silver by altering their external cell structures.  Unaccommodated cells, 10 ppm accommodated cells and 20 ppm accommodated cells were exposed to silver and the amount of silver bound to the cell was calculated.  Hall concludes that the outer surfaces of accommodated bacteria are not altered, and their alteration is not the basis for silver tolerance.

            Silver-accommodated cells appear to have lower levels of DNA synthesis than unaccommodated cells in unsilvered medium.  However, in a silvered medium, accommodated cells experience a decrease in DNA synthesis comparable to unaccommodated cells.  Therefore silver accommodation probably does not render the cell macromolecular synthesis silver resistant.

Discussion:

(1)  After discussing much of the published literature which has shown the antibacterial activity of silver, Hall states: “Unfortunately, it is very difficult to quantitate and compare the antibacterial activities of Ag salts and LIDC Ag from these studies because of the diverse methods and conditions used”.      

(3)  The literature concerning the mechanism of antibacterial action of Ag is extensively reviewed and discussed, particularly the effect on bacterial cell membranes.  Ag-membrane interaction is probably the basis for the antibacterial action of Ag.           

 

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