WO2018087222A1

WO2018087222A1 - Photodynamic disinfection of cooling lubricants

Info

Publication number: WO2018087222A1
Application number: PCT/EP2017/078749
Authority: WO
Inventors: Jochen Arentz
Original assignee: Jochen Arentz
Priority date: 2016-11-10
Filing date: 2017-11-09
Publication date: 2018-05-17
Also published as: DE102016222124A1

Abstract

The invention relates to a method and means for the photodynamic inactivation of microorganisms in a cooling lubricant using of a photosensitizer having an absorption maximum in a range of more than 700 nm, increased by an anionic surfactant. Increasing the absorption maximum of the photo-sensitizer in the long-wave range to above 700nm allows the radiation exciting the photosensitizer to penetrate deeper into the cooling lubricant and thus also the photodynamic inactivation of microorganisms in said lower-lying ranges of the cooling lubricant.

Description

Photodynamic disinfection of cooling lubricants

The invention relates to the field of disinfection of cooling lubricants (KSS).

KSS are used in the manufacturing industry for processes of machining and forming materials. In the prior art is distinguished according to DIN 51385 between non-water-miscible, water-miscible and water-mixed KSS whose water component in combination with the organic components ^¬ share (eg mineral oil) in KSS an ideal breeding ground for microorganisms. This raises the problem of unwanted contamination with microorganisms, especially in the water-miscible KSS. In order to prevent infestation of the KSS by microorganisms or to disinfect KSS already contaminated with microorganisms, a biocide can be added to the KSS. Biocide KSS offset, however, are problematic ^¬ table as they represent a permanent danger for the user. The problem arises, for example, in of ^¬ fenen production techniques, in which the mixed with the biocide KSS outgassing and harming people and persons who are exposed to occurring vapors and aerosols. Also a re-sharpening or redosing of biocides to the KSS to maintain the antimicrobial effect in the KSS need special care and professional use to prevent risks to the environment and operating personnel. For good reason, biocides are therefore subject to strict legal regulations [eg Biocidal Products Regulation (EU) No. 528/2012]. In addition, the biocide or its reaction products with biomolecules adversely affect the materials used in the manufacturing process and the work ^¬ machine tools. The invention has for its object to provide a way to disinfect or prevent contamination of the KSS with microorganisms in which microorganisms inactivated with sufficient certainty and the aforementioned disadvantages are largely avoided.

This object is achieved by the features defined in the appended Ansprü ^¬ Chen method, KSS and components used in the invention in the KSS, in particular anionic surfactants in combination with photosensitizers. The latter, in contrast to the biocides mentioned in the introduction, advantageously have negligible substance toxicity.

First, some Be ^¬ handles used in the context of the invention will be explained.

Photosensitizers are compounds which can absorb electromagnetic radiation, for example visible light, and can generate the formation of radicals and / or singlet oxygen from triplet oxygen under the influence of said radiation. A variety of commercially available compounds which are suitable for the present purpose are available to the person skilled in the art. Particularly suitable for use in the present invention are methylene blue [3,7-bis (dimethylamino) -phenothiazinium chloride] and toluidine blue [3-amino-7- (dimethylamino) -2-methylphenothiazine].

Microorganisms, also referred to as microbes, in the sense of the present invention are microscopically small organisms and include, in particular, bacteria, fungi, algae, protozoa and viruses. According to the invention, these microorganisms are at least partially inactivated photodynamically. The term inactivation also includes neutralization of the microorganisms. This includes, in particular, the destruction or dissolution (lysis) or prevention of the multiplication of the microorganism or the prevention of microorganism-related biofilm formation. A cooling lubricant (KSS) in the context of the present invention is any fluid medium which can be used in manufacturing technology during cutting and forming on machine tools and usually the heat dissipation and reduction of friction between the tool and workpiece by lubrication is used. The KSS used in the method of the present invention, in addition to the KSS own water component (and ge ^¬ optionally also present oil component) as an OF INVENTION ^¬ dung essential components, an anionic surfactant and spe ^¬-specific photosensitizers that permit the KSS when irradiated in the long wavelength region above of 700nm reactive oxygen species (ROS) to generate and thus in the KSS existing microorganisms to inactivate photodynamically. In detail: The invention is essential feature of the combination of at ^¬ nonionic surfactant with the photosensitizer that own the photosensitizer Absorptionsspekt ^¬ rum pushes its way through the surfactant component in the long-wave range of the electromagnetic spectrum above 700nm comparable. Through this described as a "bathochromic effect"

Phenomenon can for the first time specifically targeted long-wave radiation above 700nm for the deeper, that is not only at the Surface of the irradiated fluid caused by kurzwelligere Strah ^¬ treatment, photodynamic inactivation of microorganisms ^¬ be used effectively. In this connection, it should be mentioned that in order to achieve a photodynamic inactivation of microorganisms in a fluid by generating ROS, in particular singlet oxygen, in addition to the photosensitizer, an important parameter is a sufficient energy density even below the fluid surface. The production of ROS ^¬ tion is directly dependent on the energy density, which is calculated with surface irradiation after known from the prior art formula energy density = power * irradiation time / irradiation area. Penetration of the radiation penetrating several millimeters or even several centimeters to initiate the photodynamic reaction by means of a photosensitizer below the surface of the fluid

Target conflict with the use of commercially available sensitizers such as methylene blue or toluidine blue whose Absorpti ^¬ onsspektrum below 700nm and therefore must be irradiated with a coordinated radiation spectrum to trigger the photodynamic processes, on the other hand a corresponding short-wave radiation below 700nm due to lack of penetration depth can only initiate photodynamic Pro ^¬ processes on the surface of the irradiated fluid. This conflict of objectives overcomes present invention. Illustrated by way of example, this is in figure 1 the present Appli ^¬ dung, can be seen from that the absorption maximum sibilisator for the photosensitizing methylene blue known substantially below 700nm (664nm in NaCl and 655 nm in 96% ethanol) by the addition of the anionic surfactant sodium dodecyl sulfate in the infrared wavelength range above 700nm shifts. A similar effect with a bathochromic shift of the absorption spectrum, and more particularly Absorpti ^¬ onsmaximums in the long wavelength region above 700nm can be observed for other photosensitizers, for example toluidine blue with an absorption maximum in NaCl at 630nm and in 96% ethanol at 626nm. With the Invention ^¬ proper components, ie, the anionic surfactant in combination with photosensitizers, and taking advantage of the bathochromic effect, as mentioned above using long wavelength light also be made far below the fluid surface photodynamic inactivation of existing there micro ^¬ organisms. It is thus possible, for example, to achieve a light penetration depth of up to 4 cm in the case of irradiation of the fluid in the near infrared range with a wavelength of 810 nm. Apart from the fact that the infrared range used in the present invention above 700nm high quantum efficiency light sources can be used, which have particular energy efficiency, there are a number of other advantages, which are briefly summarized below:

- The long-term stability of the photosensitizer is improved considerably at Anre ^¬ supply in the infrared region above 700 nm compared to a short-wave excitation below 700nm, as the photon energy "is tosensibilisatormoleküle the binding energy of the photon;

- Adverse "seif shielding" effects and saturation effects ("photobleaching") can be avoided as far as possible. The latter is explained below starting with the basics of photodynamic application mechanisms.

The basis of photodynamic inactivation of microorganisms in a fluid is the generation of ROS by photosensitizers with sufficient supply of oxygen in the

Fluid. The photosensitizers are excited by light of corresponding wavelength from the ground state via the singlet state in the excited triplet state. Both subsequent reactions can be distinguished between two photooxidative processes (type I, type II). The Type I reaction is a chemical reaction in which radicals are formed. In this reaction, there is a charge transfer between the excited photosensitizer in the triplet state and a substrate molecule, wherein an electron or a hydrogen atom is transferred. The result is superoxide anion radicals and hydroxyl radicals. When Re ^¬ action of type II it is, however, not a chemical reaction but rather a pure energy transfer in which the energy of the photosensitizer is transferred directly to the sour ^¬ material and the highly reactive singlet oxygen is produced which is provided with reacts to the target structures of the nearby microorganisms. The photosensitizer returns to its relaxed state. In the photodynamic inactivation of microorganisms, the type II reaction in particular with the formation of singlet oxygen plays a decisive role. The activated oxygen triggers the oxidation of molecules of the nearby microorganisms, destroys in particular cell ^¬ organelles, membranes and nucleic acids of the microorganisms, so that the microorganisms are inactivated.

Normally, the above-described process of photodynamic see generation of singlet oxygen is catalytic and the photosensitizer regenerates the above-described energy release to the oxygen and is thus ready for a wei ^¬ teren cycle. However, with high energy input or by reac ^¬ tions with radials may lead to a destruction of the photosensitizer. Especially for those used in the prior art photosensitizers methylene blue and To- is luidinblau known that these in at higher energies from ^¬ bleach ( "photobleaching"), so that disadvantageously Consumption of the stock of photosensitizer in the fluid decreases the efficiency of generating reactive oxygen species, particularly singlet oxygen. Above it ^¬ imagines this adverse effect is surprisingly largely avoided when using the components and radiation inventive above 700nm.

According to one embodiment of the invention, the KSS in addition to its water (and optionally also present Ö1-) component further comprises

a photosensitizer, wherein the photosensitizer is selected from the group consisting of methylene blue [3.7-bis (dimethylamino) phenothiazinium chloride] and toluidine blue [3-amino-7- (dimethylamino) -2-methylphenothiazine], and

- at least one anionic surfactant, wherein the surfactant from the absorption maximum of the photosensitizer ^¬ moves into a region of the radiation spectrum above 700nm.

According to a preferred embodiment of the invention, the KSS is a KSS according to DIN 51385. Furthermore, the KSS may have a pH of 3-12, preferably 4-10, more preferably 5-9, more preferably 6-8, further preferably 6, 5 to 7.5, preferably 7.0 be ^¬ Sonders comprise or be set to the aforesaid pH values.

According to the invention, this KSS can be obtained from a kit comprising the corresponding components essential to the invention, i.

- a photosensitizer, preferably selected from the group consisting of methylene blue [3,7-Bis (dimethylamino) - phenothiazinium] and toluidine [3-amino-7- (dime ^¬ methylamino) -2-methylphenothiazine], and - at least one anionic surfactant, wherein the surfactant shifts the absorption maximum of the photosensitizer from ^¬ into a region of the radiation spectrum above 700nm can be produced. This kit can be marketed as an additive for a KSS to be treated accordingly.

Suitable cationic surfactants that can shift the absorption maximum of the photo ^¬ sensitizer in a region of the radiation spectrum above ^¬ half of 700nm, in particular Al come kylcarboxylate, alkyl benzene sulfonates (eg Natriumdodecylben- zolsulfonat), alkylsulfonates, fatty alcohol sulfates (for example sodium lauryl sulfate), alkyl ether ( For example, sodium dodecyl poly (oxyethylene) sulfate) and taurides into consideration.

With respect to the proportions of the photosensitizer and anionic surfactant preferred execution ^¬ forms are summarized below:

The proportion of the photosensitizer is based on the total weight of the KSS 0.001 to 0.01 wt. ~6, preferably 0.002 to 0.008 wt%, more preferably 0.003 to 0.007 wt%, more preferably 0.004 to 0.005 wt%, most preferably 0.005 wt%.

The weight % Ratio of the surfactant to the photosensitizer in the KSS is 1: 1000 to 1: 10,000, preferably 1: 2000 to 1: 8000, more preferably from 1: 3000 to 1: 6000, further be ^¬ vorzugt 1: 3500 to 1: 4500 , more preferably 1: 4000.

The subject of the present invention is furthermore a process for the at least partial photodynamic inactivation of microorganisms in a cooling lubricant comprising the steps

a) providing a hydrous KSS contaminated with microorganisms; b) adding an anionic surfactant and a photosensitizer, preferably as a mixture, to the KSS, wherein the photo ^¬ sensitizer has a bathochromic group and the Ten ^¬ sid the absorption maximum of the photosensitizer ver ^¬ pushes in a region of the radiation spectrum above 700nm, and wherein said photosensitizer is further preferably selected from the group consisting of methylene blue ^¬ [3,7-bis (dimethylamino) -phenothiaziniumchlorid] [3-amino-7- (dimethylamino) -2-methylphenothiazine] and To- luidinblau; c) irradiation of the surfactant and the photosensitizer containing KSS having a wavelength above 700nm, preferably 700-1000nm, more preferably 750-950nm, over a period of time and with an intensity, which allow the presence of microorganisms in the cooling lubricant at least in part ^¬ be photodynamically inactivate and wherein said irradiation is more preferably carried out with monochromatic radiation; and

d) optional enrichment of the KSS before and / or during the treatment of the KSS in step c) with oxygen.

The subject matter of the present invention is furthermore a method for preventing contamination of a cooling lubricant with microorganisms, in which targeted ROS is generated in the cooling ^lubricant . The method comprises the following steps

a) provision of a hydrous KSS;

b) adding an anionic surfactant and a Photosensibilisa ^¬ tors, preferably as a mixture, to the KSS, the Pho ^¬ tosensibilisator has a bathochromic group and the surfactant, the absorption maximum of the photosensitizer moves into a region of the radiation spectrum above 700nm, and wherein said photosensitizer is more preferably selected from the group consisting of Methyl ^¬ lenblau [3,7-bis (dimethylamino) -phenothiaziniumchlorid] and Toluidine blue [3-amino-7- (dimethylamino) -2-methylphenothiazine];

c) Irradiating the KSS containing the surfactant and the photosensitizer at a wavelength above 700 nm, preferably 700-1000 nm, more preferably 750-950 nm, for a time and at an intensity that allows it in the KSS by the excited photosensitizer photooxidative ROS selected from the group consisting of oxygen radicals and singlet oxygen to form, which can react with microorganisms and inactivate them, and wherein said irradiation further preferably takes place with monochromatic radiation ^¬ ; and

With regard to the optional step d) in both aforementioned methods, it should be noted at this point that the efficiency of the desired singlet oxygen formation depends on the oxygen partial pressure prevailing in the fluid (KSS). The production of singlet oxygen and the subsequent oxidative inactivation of the microorganisms lead locally to an oxygen consumption. This can be counteracted by the additional enrichment or replenishment of oxygen, as described in process step d), for example via the injection or predispersing of oxygen-containing air.

In the context of the present invention, suitable light sources include, in particular, lasers which are monochromatic (all wave trains have the same wavelength), coherent (ie temporally and spatially in-phase wave trains) and collimated (light beams run parallel as beam bundles and scarcely expand even over long distances on) light with high power. A uniform, homogeneous Intensity distribution in the illumination of the irradiated KSS field can be achieved, for example, by means of illumination by means of microlens fibers, in which a lens is firmly attached to the fiber end. Suitable light sources likewise deuterium and Tungsten-halogen lamps in considered in which a desired monochromatic wavelength can be selected by use of a corresponding Ver ^¬ grating monochromator. The absorption spectra described in the present application can be measured by means of methods and measuring devices known from the prior art. Examples include conventional spectrophotometers (eg UV / VIS spectrometer UV-160 Shimadzu p / N 204-04550), which is intended for measurements in the wavelength range of 190-1100 nm.

The invention will now be further in an embodiment with reference to the accompanying figures be ^{¬ written} , without being limited thereto.

example

In a 1 percent aqueous solution of methylene blue, sodium dodecyl sulfate was added in a ratio of 1: 4000 (i.e., one four-thousandth of a weight percent anionic surfactant) in 15 minutes

Stir in with a stir bar. The measured bat-hochrome effect, ie the surfactant-related shift of Ab ^¬ sorptionswellenlänge of methylene blue in the infrared Wel ^¬ lenlängenbereich above 700nm is shown in Figure 1, measured both for here described 1-percent wäs ^¬ serige solution of methylene blue, as also for 0.1 and 0.5 percent aqueous solutions of methylene blue in combination with the surfactant. A microorganism contaminated aqueous KSS for which a colony forming size using plate count (CFU - Colony forming unit) was determined by 10 ⁷ (. S colony formation on the Kulturmediumgel according to Figure 2) was charged with above be ^¬ prescribed 1-percent aqueous solution of Methylene blue and sodium dodecylsulfate mixed. . The wt% - Percentage of methyl ^¬ enblau in this mixture was 0.005. Subsequently, this mixture was irradiated with monochromatic light of a wavelength of 760 nm, generated with 100 LEDs at 100 lumens / watt, and taken samples after 60 minutes and 90 minutes of irradiation and their CFU index was determined. During the irradiation, 400 liters of air / h were pumped into the mixture. The CFU count the 60 minutes, the irradiated sample was 10 ³ -10 ⁴ (see FIG. Colony formation on the Kulturmediumgel ge ^¬ Mäss Figure 3), while the 90 minute sample irradiated fully ^¬ constantly was aseptically (s. The colonies free Kulturmediumgel according FIG. 4).

Claims

claims

Coolant lubricant (KSS) comprising

i) water and optionally oil,

ii) a photosensitizer, wherein said photosensitizer is selected from the group consisting of Methyl ^¬ lenblau [3,7-bis (dimethylamino) -phenothiaziniumchlo- chloride] and toluidine [3-amino-7- (dimethylamino) -2-me- thylphenothiazin ] , and

iii) at least one anionic surfactant, wherein the surfactant is the absorption maximum of the photosensitizer shifts in egg ^¬ NEN range of the radiation spectrum above 700nm.

Use of a kit comprising

i) a photosensitizer, preferably selected from the group consisting of methylene blue [3,7-bis (dime ^¬ methylamino) -phenothiaziniumchlorid] and toluidine [3-amino-7- (dimethylamino) -2-methylphenothiazine], and ii) at least one anionic surfactant wherein the surfactant pushes the absorption maximum of the photosensitizer into a region of the radiation spectrum above 700nm ver ^¬,

as an additive for a water-containing KSS, preferably as an additive for a contaminated with microorganisms water KSS.

Use of the kit according to claim 2 for the photodynamic inactivation of said microorganisms in the KSS upon irradiation of the KSS having a wavelength above 700nm, preferably 700-1000nm, more preferably 750-950nm and said irradiation is more preferably monochromatic. Process for the at least partial photodynamic inactivation of microorganisms in a cooling lubricant comprising the steps

a) providing a hydrous KSS contaminated with microorganisms;

b shifts) adding an anionic surfactant and a photosensitizer lisators, preferably as a mixture, to the KSS, wherein the photosensitizer comprises a bathochromic group and the surfactant, the absorption maximum of the photosensitizer lisators in a region of the radiation spectrum above ^¬ half of 700nm, and wherein is the Photosensibili ^¬ sator more preferably selected from the group consisting of methylene blue [3,7-bis (dimethylamino) -Phe- nothiaziniumchlorid] and toluidine [3-amino-7- (dime ^¬ methylamino) -2-methylphenothiazine];

c) Irradiating the KSS containing the surfactant and the photosensitizer at a wavelength above 700nm, preferably 700-1000nm, more preferably 750-950nm, for a time and at an intensity that allows the microorganisms present in the KSS to be at least partially photodynamic inactivate and wherein said irradiation further preferably takes place with mono ^¬ chromatic radiation; and

Method for the targeted generation of reactive oxygen species (ROS) in a cooling lubricant for the prevention of contamination with microorganisms comprising the steps of a) providing a water-containing cooling lubricant;

b) adding an anionic surfactant and a Photosensibi- lisators, preferably as a mixture, to the KSS, wherein comprising the photosensitizer is a bathochromic group and the surfactant, the absorption maximum of the photosensitizer lisators in a region of the radiation spectrum above ^¬ half of 700nm moves, and wherein the Photosensibili ^¬ sator is more preferably selected from methylene blue [from the group 3.7-Bis (dimethylamino) nothiaziniumchlorid -Phe-] and toluidine [3-amino-7- (dime ^¬ methylamino) -2-methylphenothiazine];

c) irradiating the KSS containing the surfactant and the photosensitizer at a wavelength above 700nm, preferably 700-1000nm, more preferably 750-950nm, for a time and at an intensity that allows in the KSS the photooxidative ROS photosensitizer excited selected from the group consisting of oxygen radicals and singlet oxygen that can react with and inactivate microorganisms, and wherein said irradiation is more preferably monochromatic; and

KSS according to claim 1, use according to claim 2-3 or process according to claims 4-5, characterized in that the anionic surfactant is selected from the group consisting of

carboxylates,

Alkylbenzenesulfonates, preferably sodium dodecylbenzenesulfonate,

AIkylsulfonaten,

Fatty alcohol sulfates, preferably sodium lauryl sulfate, alkyl ether sulfates, preferably sodium dodecyl poly (oxyethylene) sulfate, Taurids.

KSS according to claim 1, use according to claim 2-3 or method according to claim 4-5, characterized in that the KSS is a KSS according to DIN 51385.

KSS according to claim 1, Use according to claim 2-3 or method of claim 4-5, characterized in that the proportion of the photosensitizer by weight, based on the weight of the KSS Gesamtge ^¬ 0.001 to 0.01.%, Preferably 0.002 to 0.008 wt. , more preferably from 0.003 to 0.007 wt%.%, is more preferably 0.004 to 0.005 wt.%, particularly before Trains t ^¬ 0.005 wt.%.

KSS according to claim 1, use according to claim 2-3 or method according to claims 4-5, characterized in that the wt. % Ratio of the surfactant to the photosensitizer in the KSS 1: 1000 to 1: 10000, preferably 1: 2000 to 1: 8000, more preferably 1: 3000 to 1: 6000, further preferably 1: 3500 to 1: 4500, more preferably 1: 4000.

KSS according to claim 1, use according to claim 2-3 or method according to claim 4, characterized in that the KSS a pH of 3-12, preferably 4-10, further preferably ^¬ 5-9, more preferably 6-8 , more preferably 6.5 to 7.5, particularly preferably 7.0 or is adjusted to before ^¬ said pH values.