Antimicrobial polymer

Details Antimicrobial polymer Antimicrobial polymer

2002-03-04

2004-03-16

Truong, Duc (Department: 1711)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Nitrogen-containing reactant

C528S423000, C528S425000, C528S272000, C528S288000, C428S690000, C428S917000

Reexamination Certificate

active

06706855

ABSTRACT:

The present invention relates to antimicrobial polymers which carry a chromophoric marker, more particularly to cationic antimicrobial polymers carrying a covalently bound chromophoric marker and to methods for detecting the antimicrobial polymers on or in a medium.
Antimicrobial polymeric compounds are used in a wide range of media to control or eliminate micro-organisms, for example industrial media such as cooling water, metal working fluids, latices, surface coatings, and geological drilling fluids; recreational waters such as swimming pools and spas; and in personal care formulations such as soaps and cosmetics. The antimicrobial polymers are used in such media as preservatives, disinfectants, slimicides and algicides. Antimicrobial polymers, especially cationic antimicrobial polymers are particularly useful and offer a number of advantages over molecular quaternary ammonium compounds, because they are of relatively low toxicity and exhibit reduced foaming when added to a liquid medium such as water.
To prevent the proliferation of microorganisms in or on a medium containing an antimicrobial compound it is necessary to ensure that the concentration of antimicrobial compound is sufficient to give an antimicrobial effect In the medium. However, in most media, especially swimming pools, the concentration of antimicrobial compound reduces with time through a number of mechanisms, for example adsorption; chemical break down caused by interaction of the antimicrobial compound with micro-organisms or with other components present in the medium; and in the case of recirculating water systems such as swimming pools and spas by dilution when fresh water is added to the system. This can result in loss of the antimicrobial protection provided by the antimicrobial compound and the subsequent proliferation of micro-organisms.
To ensure that a medium remains protected by the antimicrobial compound it is therefore important that the concentration of antimicrobial compound in, or on, a medium can be accurately determined to ensure that sufficient concentration of the antimicrobial; compound is maintained. Antimicrobial compounds are typically used at very low concentrations, often less than 10 ppm. Therefore, the system used to measure the concentration of antimicrobial compound must be able to detect ppm levels of the compound, otherwise inaccurate readings will be obtained leading to incorrect dosage levels of the antimicrobial material.
In some applications there is a need to detect the presence of the antimicrobial compound at even lower levels. For example antimicrobial compounds are often used to protect fruit against microbial degradation during storage and transportation. However, before the fruit is sold to consumers it is necessary to wash the fruit to remove the antimicrobial compounds from the fruit. Typically the washing process is required to reduce the concentration of the antimicrobial compounds to about 1 to 10 ppb. In this application there is a need for accurate detection of the antimicrobial compound to ensure that all or substantially all of the compound has been removed during the washing process. Such detection therefore needs to be sensitive to ppb concentrations of the antimicrobial material.
However, the polymeric nature of polymeric antimicrobial compounds makes accurate determination of the concentration difficult and time consuming. This is especially true of cationic polymeric antimicrobial compounds because the cationic groups tend to associate themselves with a surface to which they are applied. To determine the concentration of the antimicrobial compound on a surface, for example on the surface of fruit, it is necessary to extract the antimicrobial compound from the surface and analyse the extract, for example using gel permeation chromatography. However, because most antimicrobial polymers comprise a mixture of polymer chains of different lengths, this procedure often gives a misleading result of the concentration because the extraction method tends to preferentially extract the shorter polymer chains.
Furthermore, polymeric antimicrobial compounds are often used in media which contain numerous other components which can interfere with the analysis method used to estimate the concentration of the polymeric antimicrobial compound. For example, in swimming pools poly(hexamethylenebiguanide) (PHMB) is commonly used as a primary sanitizer. A known calorimetric method for estimating the PHMB in the pool is based on, the interaction of PHMB with bromophenol blue or Eosin dyestuffs. However, this test also detects quaternary ammonium compounds which are often present in swimming pools and thereby gives a false measure of concentration of the PHMB.
There is therefore a need for a polymeric antimicrobial material which provides good protection against the growth of undesirable micro-organisms and which can be readily detected In or a medium to which it has been applied.
We have found that by covalently binding a chromophoric marker on, or in, an antimicrobial polymer enables the antimicrobial compounds to be detected with greater, accuracy, especially at low concentration without adversely affecting the antimicrobial properties of the polymer.
According to a first aspect of the present invention there is provided an antimicrobial polymer, characterised in that it carries a covalently bound chromophoric marker (hereinafter “The Polymer”).
Preferably The Polymer is a cationic antimicrobial polymer, more preferably a poly(quaternary ammonium) compound, a polymeric guanide or especially a polymeric biguanide.
The chromophoric marker comprises a chromophoric group which absorbs and/or emits radiation at wavelengths characteristic of the chromophoric group. The wavelength of absorbtion and/or emission provides a reproducible “signature” associated with The Polymer by means of which it is possible to detect the presence of The Polymer using a suitable optical or spectroscopic detection method. This signature is preferably different from any absorption or emission bands inherent in the antimicrobial polymer which does not contain the chromophoric marker, because this enables more accurate detection of the chromophoric marker, particularly at low concentrations of The Polymer in a medium
Preferably the chromophoric group has a major absorption and/or emission band in the UV, visible or near infra red range of the electromagnetic spectrum. A suitable absorption and/or emission range is from 275 to 1500 nm, preferably from 390 to 1100 nm, more preferably from 400 to 800 nm.
When the chromophoric group emits radiation, it may do so via phosphorescence or more preferably fluorescence.
Suitable chromophoric groups comprise an azo, anthraquinone, pyrroline, phthalocyanine, polymethine, aryl-carbonium, triphenodioxazine, diarylmethane, triarylmethane, anthraquinone, phthalocyanine, methine, polymethine, rhodamine, indoaniline, indophenol, stilbene, squarilium, coumarin, aminoketone, xanthene, fluorine, acridene, acridan, acridinium, quinolene, thiazole, azine, nigrosine, oxazine, thiazine, indigoid quininold, quinacridone, lactone, pyrroline, luciforyl, indacene, benzodifuranone, indolene, or an aromatic fluorescent group or a combination of such groups.
In a preferred embodiment of the present invention the chromophoric group is a fluorescent group which emits radiation in a specific fluorescence band at a wavelength which is longer than that of the absorption band. Preferably the fluorescent group has its major absorption band of in the range of from 300 to 100 nm, more preferably 390 to 1100 nm and especially from 400 to 800 nm. Preferably the fluorescence band is from 350 to 1550 nm more preferably from 400 to 800 nm, especially from 430 to 600 nm and more especially from 440 to 460 nm.
Preferred fluorescent groups have a quantum efficiency of at least 0.01, more preferably at least 0.1 and especially 0.5. The quantum efficiency of a fluorescent material is defined as the number of photons emitted by the fluorescent material at the peak wavelength of the emission band divide

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