(12) United States Patent (10) Patent No.: US 6,706,855 B1 Collins Et Al
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USOO6706855B1 (12) United States Patent (10) Patent No.: US 6,706,855 B1 Collins et al. (45) Date of Patent: Mar. 16, 2004 (54) ANTIMICROBIAL POLYMER (56) References Cited (75) Inventors: Andrew Neale Collins, Manchester U.S. PATENT DOCUMENTS (GB); Brian David Bothwell, 5,235,045 A 8/1993 Lewis et al. Manchester (GB); Graham John 5,498,547 A 3/1996 Blake et al. McPherson, Manchester (GB) FOREIGN PATENT DOCUMENTS (73) Assignee: Avecia Limited, Manchester (GB) JP 56 167383 A 12/1981 SU 619 489 A 7/1978 (*) Notice: Subject to any disclaimer, the term of this WO WO 94/09357 4/1994 patent is extended or adjusted under 35 WO WO 94/09360 4/1994 U.S.C. 154(b) by 40 days. WO WO 98/02492 1/1998 (21) Appl. No.: 10/070,152 OTHER PUBLICATIONS (22) PCT Filed: Jul. 25, 2000 S.C. Chang et al., Bioorg. Med. Chem. Lett. (1993) vol. 3, (86) PCT No.: PCT/GB00/02864 No. 4, pp. 555-556. S371 (c)(1), Primary Examiner Duc Truong (2), (4) Date: Mar. 4, 2002 (74) Attorney, Agent, or Firm- Pillsbury Winthrop LLP (87) PCT Pub. No.: WO01/17356 (57) ABSTRACT An antimicrobial polymer, characterised in that it carries a PCT Pub. Date: Mar. 15, 2001 covalently bound chromophoric marker. The antimicrobial (30) Foreign Application Priority Data polymer is preferably a cationic antimicrobial polymer, especially a poly(hexamethylenebiguanide). Also claimed Sep. 3, 1999 (GB) ............................................. 992O774 are compositions containing the antimicrobial polymer, a (51) Int. Cl." ......................... C08G 73/00; CO8G 73/06 method for treating a medium using the antimicrobial poly (52) U.S. Cl. ....................... 528/422; 528/423: 528/425; mer and a method for detecting the antimicrobial polymer in 528/272; 528/288; 428/690; 428/917 a medium. (58) Field of Search ................................. 528/422, 423, 528/425, 272, 288; 428/690,917 23 Claims, No Drawings US 6,706,855 B1 1 2 ANTIMICROBIAL POLYMER been removed during the Washing process. Such detection therefore needs to be Sensitive to ppb concentrations of the CROSS REFERENCE TO RELATED antimicrobial material. APPLICATIONS However, the polymeric nature of polymeric antimicro bial compounds makes accurate determination of the con This application is a national phase application based on centration difficult and time consuming. This is especially PCT/GB00/02864, filed Jul 25, 2000, and which further true of cationic polymeric antimicrobial compounds because claims priority from British Application No. 992.0774.8, the cationic groups tend to associate themselves with a filed Sep. 3, 1999. These applications in their entirety are Surface to which they are applied. To determine the concen incorporated herein by reference. tration of the antimicrobial compound on a Surface, for The present invention relates to antimicrobial polymers example on the Surface of fruit, it is necessary to extract the which carry a chromophoric marker, more particularly to antimicrobial compound from the Surface and analyse the cationic antimicrobial polymers carrying a covalently bound extract, for example using gel permeation chromatography. chromophoric marker and to methods for detecting the However, because most antimicrobial polymers comprise a antimicrobial polymers on or in a medium. mixture of polymer chains of different lengths, this proce Antimicrobial polymeric compounds are used in a wide 15 dure often gives a misleading result of the concentration range of media to control or eliminate micro-organisms, for because the extraction method tends to preferentially extract example industrial media Such as cooling water, metal the shorter polymer chains. working fluids, latices, Surface coatings, and geological Furthermore, polymeric antimicrobial compounds are drilling fluids, recreational waterS Such as Swimming pools often used in media which contain numerous other compo and Spas, and in personal care formulations Such as Soaps nents which can interfere with the analysis method used to and cosmetics. The antimicrobial polymers are used in Such estimate the concentration of the polymeric antimicrobial media as preservatives, disinfectants, Slimicides and algi compound. For example, in Swimming pools poly cides. Antimicrobial polymers, especially cationic antimi (hexamethylenebiguanide) (PHMB) is commonly used as a crobial polymers are particularly useful and offer a number primary Sanitizer. A known calorimetric method for estimat of advantages over molecular quaternary ammonium 25 ing the PHMB in the pool is based on, the interaction of compounds, because they are of relatively low toxicity and PHMB with bromophenol blue or Eosin dyestuffs. However, exhibit reduced foaming when added to a liquid medium this test also detects quaternary ammonium compounds Such as water. which are often present in Swimming pools and thereby To prevent the proliferation of microorganisms in or on a gives a false measure of concentration of the PHMB. medium containing an antimicrobial compound it is neces There is therefore a need for a polymeric antimicrobial Sary to ensure that the concentration of antimicrobial com material which provides good protection against the growth pound is Sufficient to give an antimicrobial effect In the of undesirable micro-organisms and which can be readily medium. However, in most media, especially Swimming detected In or a medium to which it has been applied. pools, the concentration of antimicrobial compound reduces 35 We have found that by covalently binding a chromophoric with time through a number of mechanisms, for example marker on, or in, an antimicrobial polymer enables the adsorption; chemical break down caused by interaction of antimicrobial compounds to be detected with greater, the antimicrobial compound with micro-organisms or with accuracy, especially at low concentration without adversely other components present in the medium; and in the case of affecting the antimicrobial properties of the polymer. recirculating water Systems Such as Swimming pools and 40 According to a first aspect of the present invention there Spas by dilution when fresh water is added to the System. is provided an antimicrobial polymer, characterised in that it This can result in loss of the antimicrobial protection pro carries a covalently bound chromophoric marker Vided by the antimicrobial compound and the Subsequent (hereinafter “The Polymer”). proliferation of micro-organisms. Preferably The Polymer is a cationic antimicrobial To ensure that a medium remains protected by the anti 45 polymer, more preferably a poly(quaternary ammonium) microbial compound it is therefore important that the con compound, a polymeric guanide or especially a polymeric centration of antimicrobial compound in, or on, a medium biguanide. can be accurately determined to ensure that Sufficient con The chromophoric marker comprises a chromophoric centration of the antimicrobial; compound is maintained. group which absorbs and/or emits radiation at wavelengths Antimicrobial compounds are typically used at very low 50 characteristic of the chromophoric group. The wavelength of concentrations, often less than 10 ppm. Therefore, the SyS absorbtion and/or emission provides a reproducible "Signa tem used to measure the concentration of antimicrobial ture' associated with The Polymer by means of which it is compound must be able to detect ppm levels of the possible to detect the presence of The Polymer using a compound, otherwise inaccurate readings will be obtained Suitable optical or spectroscopic detection method. This leading to incorrect dosage levels of the antimicrobial mate 55 Signature is preferably different from any absorption or rial. emission bands inherent in the antimicrobial polymer which In Some applications there is a need to detect the presence does not contain the chromophoric marker, because this of the antimicrobial compound at even lower levels. For enables more accurate detection of the chromophoric example antimicrobial compounds are often used to protect marker, particularly at low concentrations of The Polymer in fruit against microbial degradation during Storage and trans 60 a medium portation. However, before the fruit is sold to consumers it Preferably the chromophoric group has a major absorp is necessary to wash the fruit to remove the antimicrobial tion and/or emission band in the UV, visible or near infrared compounds from the fruit. Typically the Washing process is range of the electromagnetic spectrum. A Suitable absorption required to reduce the concentration of the antimicrobial and/or emission range is from 275 to 1500 nm, preferably compounds to about 1 to 10 ppb. In this application there is 65 from 390 to 1100 nm, more preferably from 400 to 800 nm. a need for accurate detection of the antimicrobial compound When the chromophoric group emits radiation, it may do to ensure that all or Substantially all of the compound has So via phosphorescence or more preferably fluorescence. US 6,706,855 B1 3 4 Suitable chromophoric groups comprise an azo, When the chromophoric marker is present as a pendant or anthraquinone, pyrroline, phthalocyanine, polymethine, terminal group on the polymer chain, the covalent bond aryl-carbonium, triphenodioxazine, diarylmethane, between the polymer and the marker is preferably formed by triarylmethane, anthraquinone, phthalocyanine, methine, means of a reactive functional group on the chromophoric polymethine, rhodamine, indoaniline, indophenol, Stilbene, marker which is capable of forming a covalent bond with the Squarilium, coumarin, aminoketone, Xanthene,