Not sure if this has been posted before, but below is the patent...

Not sure if this has been posted before, but below is the patent application for our ENDOSCOPE CLEANING WITH VISCOELASTIC LIQUID (posted on 23 April 2020). (source: https://worldwide.espacenet.com/). GLTAH - hope we get more info on this asap and market release. Large complex market to automate and replace a manual process.

[0003] Thisinvention relates to methods for reducing biocontaminant on contaminatedsurfaces, more specifically contaminated surfaces which are difficult to cleanby conventional cleaning methods, such as the interior cavities and lumens ofdevices, and in particular for cleaning the lumens, cylinders, valve socketsand connectors of contaminated medical instruments. However, it will beappreciated that the invention is not limited to this particular field of use.

BACKGROUND

[0005] An endoscopeis an elongated tubular instrument that may be rigid or flexible and whichincorporates an optical or video system and light source. Typically, anendoscope is configured so that one end can be inserted into the body of apatient via a surgical incision or via one of the natural openings of the body.Internal structures near the inserted end of the endoscope can be thus beviewed by an external observer.

[0006] As well asbeing used for investigation, endoscopes are also used to carry out diagnosticand surgical procedures. Endoscopic procedures are increasingly popular astheir minimally invasive nature provides a better patient outcome (throughreduced healing time and exposure to infection) enabling hospitals and clinicsto achieve higher patient turnover. Endoscopestypically take the form of a long tube-like structure with a‘distal tip’ at oneend for insertion into a patient and a‘connector end’ at the other with acontrol handle located near the centre of the length. Typically, the connectorend is hooked up to a supply of light, water, suction and pressurised air. Thecontrol handle is held by the operator during the procedure to control theendoscope via valves and control wheels. The distal tip contains the cameralens, lighting, nozzle exits for air and water, exit point for suction andforceps. All endoscopes have internal channels used either for delivering airand/or water, providing suction or allowing access for forceps and othermedical equipment required during the procedure. Some of these channels runfrom one end of the endoscope to the other while others run via valve socketsat the control handle. Some channels bifurcate while others join from two intoone. Endoscopes used for diagnostic or surgical purposes contain a long, narrowlumen (sometimes referred to as a forceps channel) through which surgicalapparatus can pass. The apparatus can be used to remove diseased tissue orcollect tissue samples for diagnosis. The collected tissue is then removed fromthe endoscope by drawing it outwards through the lumen. As a consequence, thelumen can become contaminated with traces of tissue from the patient. Blood,mucus and faecal matter, which are all forms of biocontaminant and can harbourbioburden, can also readily find their way into the lumen.

[0008] The high costof endoscopes means they must be re-used. Because of the need to avoid crossinfection from one patient to the next, each endoscope must be thoroughlycleaned and disinfected or sterilised after each use. This involves thecleaning of not only the outer skin of the endoscope, but also cleaning anddisinfecting the lumen. Endoscopes used for colonoscopic procedures areapproximately two meters long and have one or more lumen channels of diameterno more than a few millimetres. Ensuring that such long narrow channels areproperly cleaned and disinfected between patients presents a considerablechallenge. The challenge of cleaning is also made more difficult by the factthat there is not just one configuration for endoscopes. There are a variety ofendoscopic devices suited to the particular cavity to be investigated i.e.colonoscopes inserted into the colon, bronchoscopes inserted into the airwaysand gastroscopes for investigation of the stomach. Gastroscopes, for instance,are smaller in diameter than colonoscopes; bronchoscopes are smaller again andshorter in length while duodenoscopes have a different tip design to access thebile duct. Some endoscopes, such as duodenoscopes, also possess a“blind lumen”,closed at one end which can be even more difficult to clean.

[0009] A variety ofoptions are available to mechanically remove biological residues from the lumenwhich is the first stage in the cleaning and disinfection process. By far themost common procedure for cleaning the lumens uses small brushes mounted onlong, thin, flexible lines. Brushing is the mandated means of cleaning thelumen in some countries. These brushes are fed into the lumens while theendoscope is submerged in warm water and a cleaning solution. The brushes arethen pushed / pulled through the length of the lumens in an effort to scrub offthe soil / biocontaminant. Manual back and forth scrubbing is required. Waterand cleaning solutions are then flushed down the lumens. These flush-brushprocesses are repeated three times or until the endoscope reprocessingtechnician is satisfied that the lumen is clean. At the end of this cleaningprocess air is pumped down the lumens to dry them. A flexible pull-throughhaving wiping blades may also be used to physically remove material. A liquidflow through the lumen at limited pressure can also be used. In general, onlythe larger suction/biopsy lumens can be cleaned by brushing or pull throughs.Air/water channels are too small for brushes, so these lumens are usually onlyflushed with water and cleaning solution.

[0010] Aftermechanical cleaning, a chemical clean is carried out to remove the remainingbiological contaminants. Because endoscopes are sensitive and expensiveapparatus, the biological residues cannot be treated at high temperatures orwith strong chemicals. For this reason, the mechanical cleaning needs to be asthorough as possible. In many cases, the current mechanical cleaningmethodologies fail to fully remove biofilm from lumens, particularly wherecleaning relies on liquid flow alone. Regardless of how good the conventionalcleaning processes are it is almost inevitable that a small microbial load willremain in the channel of the lumen. There has been significant research to showthat the method of cleaning with brushes, even when performed as prescribed,does not completely remove biofilm in endoscope lumens.

[0011] Biofilms area particularly challenging from of biocontaminant and start to form when afree- floating microorganism attaches itself to a surface and surrounds itselfwith a protective polysaccharide layer. The microorganism then multiplies, orbegins to form aggregates with other microorganisms, increasing the extent ofthe polysaccharide layer. Multiple sites of attachment can in time join up, formingsignificant deposits of biofilm. Once bacteria or other microorganisms areincorporated in a biofilm, they become significantly more resistant to chemicaland mechanical cleaning than they would be in their free-floating state. Theorganisms themselves are not inherently more resistant, rather, resistance isconferred by the polysaccharide film and the fact that microorganisms can bedeeply embedded in the film and isolated from any chemical interaction. Anyresidual biofilm remaining after an attempt at cleaning quickly returns to anequilibrium state and further growth of microorganisms within the filmcontinues.

[0012] As well aslacking in efficacy, particularly in respect of biofilms, the current manualbrushing procedures suffer from other drawbacks. The large number of differentendoscope manufacturers and models results in many minor variations of themanual cleaning procedure. This has led to confusion and ultimately poorcompliance in cleaning processes. The current system of brushing is also hazardousto the endoscope reprocessing staff who clean them. Brushing can disperse smallparticles or aerosols of biocontaminant into the air which can be accidentallyingested or inhaled. The chemicals that are currently used to clean endoscopescan adversely affect the reprocessing staff. The current system of manualbrushing is also labour intensive, leading to increased cost. Thus, the currentapproaches to cleaning and disinfecting the lumens in medical apparatus arestill inadequate and residual microorganisms are now recognised as asignificant threat to patients and staff exposed to these devices.

[0013] There isevidence of bacterial transmission between patients from inadequate cleaningand disinfection of internal structures of endoscopes which in turn has led topatients acquiring mortal infections. Between 2010 and 2015 more than 41hospitals worldwide, most in the U.S., reported bacterial infections linked tothe scopes, affecting 300 to 350 patients(http://www.modemheaithcare.com/article/20160415/NEWS/160419937). It would beexpected that a reduction in the biocontaminant in various medical deviceswould produce a concomitant overall reduction in bioburden (the amount ofpathogens) and ultimately reduce infection rates and mortality. In addition, ifan endoscope is not properly cleaned and dried, biofilm can form on theinterior surfaces of the device. Endoscope lumens are particularly prone tobiofilm formation. They are exposed to significant amounts of biocontamination,and subsequent cleaning of the long narrow lumens is quite difficult due toinaccessibility and the inability to monitor the cleaning process. There isconsiderable pressure in medical facilities to reprocess endoscopes as quicklyas possible. Because endoscopes are cleaned by hand, the training and attitudeof the technician are important in determining the cleanliness of the device.Residual biofilm on instruments can result in a patient acquiring an endoscopeacquired infection. Typically, these infections occur as outbreaks and can havefatal consequences for patients.

[0014] Biofilm canbe problematic in other areas, such as in the food, beverage andair-conditioning fields. Although not subject to high loads of biocontaminantsin the manner of endoscopes, fluid lines are often provided with high volumesof nutrients under ideal conditions for the formation and growth of biofilms.

[0015] Biocontaminationas used herein refers to any king of material of biological origin such asbiofilms and related polysaccharide matrices, blood, mucous, faeces, andproteinaceous matter, including hardened denatured proteinaceous matter and thelike, or other material which is capable of harbouring bioburden or microbialmaterial such as bacteria, viruses, fungi, spores, prions and other pathogens.

[0016] Oneembodiment of the present invention allows to overcome or ameliorate at leastone of the disadvantages of the prior art, or to provide a useful alternative.

SUMMARY OF THE INVENTION

[0017] According toa first aspect the invention provides a method of reducing biocontaminant on asurface contaminated therewith comprising contacting the surface withviscoelastic liquid having a low lubricity, and flowing said viscoelasticliquid along said surface thereby to remove contaminant from the surface. Theviscoelastic liquid is such that the flow is plug flow, rather than liquidflow.

[0018] Preferably,the viscoelastic liquid is flowed under conditions of controlled shear rateand/or strain.

[0019] According toa second aspect, the invention provides a viscoelastic liquid having a lowlubricity.

[0020] In the aboveaspects of the invention, the viscoelastic liquid preferably has the followingrheological and tribological properties at 21 °C:

[0021] a rotationalyield point between 140% strain and 300% strain;

[0022] a peakviscosity between 550 Pa s and 2000 Pa s;

[0023] anoscillatory flow point between 250 and 700 % strain; and

[0024] a coefficientof friction m which has a maximum value in the viscoelastic liquid’selastohydrodynamic region.

[0025] Therotational yield point may be for example between 170% strain and 270% strainor between 200% strain and 250% strain.

[0026] The peakviscosity may be for example between 600 Pa s and 1200 Pa s.

[0027] Theoscillatory flow point may be for example between 250 and 700 % strain.

[0028] Thecoefficient of friction m may for example have a maximum value in the range0.005-1 .0 m/s. or 0.01 -0.3 m/s or 0.5 to 0.15 m/s.

[0029] The maximumvalue for the coefficient of friction m is independently 0.06 or greater (forinstance 0.06-1) or 0.1 or greater (for instance 0.1 -1) or 0.12 or greater(for instance 0.12 or greater)

[0030] In certainembodiments, the surface cleaned by the present method may be a contaminatedsurface of a medical instrument.

[0031] The surfaceof a medical instrument may be an interior surface of a medical instrument,such as an endoscope. The interior surface may be, for example, an elongatelumen, suction valve cylinder, air/water cylinder or biopsy port.

[0032] In otherembodiments, the surface may be for example the inner surface of a dental lineor a line used in the preparation or dispensation of food or beverage.

[0033] Thebiocontaminant may be one or more of flesh, blood, mucous, faeces, biofilm orlubricant.

[0034] Theviscoelastic liquid may be flowed continuously in a single direction, or theflow of the viscoelastic liquid may be pulsed. The viscoelastic liquid may beflowed alternately in different directions.

[0035] Preferably,the viscoelastic liquid has a flow rate which is at or below the maximumallowable pressure rating of the medical instrument.

[0036] Preferably,the viscoelastic liquid has a flow rate such that the elastic modulus (also sometimesreferred to as the storage modulus) G’ of the viscoelastic liquid exceeds theviscous modulus (also sometimes referred to as the loss modulus) G” of theviscoelastic liquid. That is, for any given viscoelastic fluid, G’>G”. It isalso preferred that the viscoelastic liquid is passed along the surface (orthrough the lumen) at a flow rate such that the shear rate of the viscoelasticliquid is below the flow point of the viscoelastic liquid.

[0037] In the caseof cleaning a lumen or line, the flow rate is predetermined based upon thelumen diameter being cleaned. In general, the relationship is that for anendoscope lumen of x mm diameter, the flow rate should be in the range of 0.5 xml/min - 2 x ml/min.

[0038] Thus, forinstance, for a 0.9mm diameter lumen, the flow rate is between 0.45ml/min and 1.8ml/min, for a 1 .45 mm diameter lumen the flow rate is between 0.8ml/min and2.9ml//min and for a 4mm lumen the flow rate is between 2ml/min and 8ml/min

[0039] The methodsof the present invention may further include one or more pre-rinsing orpostrinsing steps with water and/or enzymatic detergent.

[0040] Preferably,the viscoelastic liquid comprises one or more cationic, amphoteric, anionic ornonionic polymers dispersed in a solvent, which for preference is water. Theviscoelastic liquid may contain a dispersed high-surface area inorganic and/ororganic material, for instance, a high-surface area material having a surfacearea of 50-600 m2 /g.

[0041] Theviscoelastic liquid may contain dispersed abrasive particles of inorganicand/or organic materials.

[0042] However, itis important that the viscoelastic liquid of the present invention excludesmicrofibrils or other additives that may affect the rheology and result in theviscoelastic liquid having a liquid flow rather than a cohesive plug flow as inthe case of the present invention.

[0043] In oneembodiment, the contaminant is biofilm and the viscoelastic liquid containssilica particles, which may be silica nanoparticles. These are for preferencehydrophilic fumed silica nanoparticles. The silica nanoparticles preferablyhave a particle size of 10-1 OOnm, more preferably 20- 70 nm. The primarynanoparticles of fumed Silica may in some cases be agglomerated in micron-sizedclusters. In some embodiments, the Silica content is in the range of 0.5 to 20%by weight.

[0044] Theviscoelastic liquid may contain dispersing agents and or one or moresurfactants and/or emulsifiers. It may contain one or more inorganic and/ororganic rheology modifiers.

[0045] Forpreference the polymer used in the viscoelastic liquid is carbomer,crosspolymer, acrylic polymer, Guar Gum or mixture thereof. Preferably, thepolymer is Polyacrylate crosspolymer-6 or carbomer, or a mixture of both.

[0046] The polymermay be synthetic or natural. The solid content of the viscoelastic liquid isbetween 0.1 and 40% by weight, for example, between 0.5 and 35% by weight orbetween 1 and 20% by weight or between 1 and 10% by weight or between 2 and 7%by weight or between 3 and 6% by weight. The polymer content is preferably inthe range of 0.1 to 20% by weight, for example, between 0.1 and 5% by weight orbetween 0.2 and 4% by weight or between 0.5 and 3% by weight. If water is thesolvent for the viscoelastic liquid, it is preferably present in an amount of0.1 -99.9%, for example between 90 and 98% by weight or between 95 and 97% byweight.

[0047] Theterm“viscoelastic liquid” as used herein is a mixture of one or more polymersin a solvent or carrier fluid, which in some embodiments is water, although anyother suitable solvent or carrier fluid may be used. Unless the context clearlyrequires otherwise, throughout the description and the claims, thewords“comprise”,“comprising”, and the like are to be construed in an inclusivesense as opposed to an exclusive or exhaustive sense; that is to say, in thesense of“including, but not limited to”.

[0048] Theterm“cleaning” as used herein is intended to refer to the removal of inorganicand organic matter, including but not limited to bio burden, microorganisms,biofilm and lubricants.

[0049] BRIEFDESCRIPTION OF THE DRAWINGS

[0050] Figure 1shows a mechanism of viscoelastic liquid action.

[0051] Figure 2shows a schematic diagram of the bench-top cleaning process of the endoscopemodel with the viscoelastic liquid.

[0052] Figure 3shows the viscosity in Pa s against shear strain in % for cleaning compositionsof the present invention.

[0053] Figure 4shows a typical graph of a formulations of the present invention illustratingthe relationship between elastic modulus G’, viscous modulus G” and viscosityh.

[0054] Figure 5shows a device for measuring tribological properties of the cleaningcompositions of the present invention.

[0055] Figure 6shows the operation of the device for measuring tribological properties.

[0056] Figure 7shows the Stribeck curve, relating hydrodynamic viscosity with linear velocity.

[0057] Figure 8shows the region of importance for determining the significance of tribologicalproperties on cleaning ability for compositions of the present invention.

[0058] Figure 9shows an aggregate plot of all the tribiological curves of the embodiments ofthe present invention and comparative examples.

[0059] Figures 10 to14 show test arrangements used in the present invention to measure the efficacyof endoscope cleaning.

[0060] DESCRIPTIONOF THE INVENTION

[0061] Embodimentsof the present disclosure relate to passing a viscoelastic liquid along acontaminated surface to remove contaminant from the surface. For instance, theviscoelastic liquid may be passed through the lumen, cylinder, valve socket orconnector of an endoscope for the purposes of cleaning the endoscope channel ofbiocontaminant, which includes residual tissue such as flesh, blood, mucous andfaeces remaining after diagnostic or surgical procedures.

[0062] In anembodiment the viscoelastic liquid comprises dissolved and/or dispersedchemicals in a carrier fluid— The carrier fluid is selected to provide asuitably stable formulation. Suitable carrier fluids include water, alcohols,glycols or their mixtures, or any other suitable fluids.

[0063] Thisviscoelastic liquid can be a viscoelastic polymeric water-based system or anyother viscoelastic system. It may also contain additional functional additives,like rheology modifiers, high surface area inorganic materials, dispersingagents, surfactants, emulsifiers, solvents or other functional ingredients toenhance the cleaning efficacy. These can include abrasive particles orparticles with adsorbent properties. The formulations of the present inventionhave been shown to demonstrate cleaning efficiency which results from theirrheological and tribological properties. The chemistry of each formulation hasbeen found to be not relevant to the cleaning efficacy. As can be seen in theexamples and comparative examples given below, a number of formulations weretested and it was not predictable from the composition of the formulationsalone which formulations would be effective cleaning agents. For example, polyacrylatewas found to be effective with fumed silica and fumed alumina, but ineffectivewith activated carbon. Guar gum was effective with g-alumina, or on its own,but not when added to Carbopol, which was a component of many other effectivecleaning formulations. Thus, looking solely at the chemistries of the cleaningmixtures, it is impossible to establish a coherent model for predictingcleaning.

[0064] The rheologyof each sample provides some level of predictive capacity; however, it wasfound that there were a number of samples that possessed the rheologicalprofile of effective cleaning formulations but which nevertheless were notparticularly effective. The present inventors have established a specifichitherto unknown rheology/tribology profile that consistently provides goodcleaning of lumens, as established by biological testing.

[0065] In someembodiments, the viscoelastic liquid contains other functional ingredients likerheology modifiers, high surface area adsorbing materials, surfactants,dispersing agents, emulsifiers, solvents or suspended inorganic/organicparticles. This viscoelastic liquid behaves largely as fluid with the elasticmodulus (G’) dominating.

[0066] In oneembodiment, the viscoelastic liquid is a water-based system with optimisedrheology containing dispersed polymers and high surface area hydrophilic fumedsilica. Nanoparticles of silica have been shown in some cases to be useful inthe removal of biofilm. The process is a complex physico-chemical one andinvolves more than simple mechanical action. Nevertheless, other suspendedsolid particles, for instance crystalline silica (greater than nanoscale),calcium carbonate, activated carbon or other abrasive materials and theirmixtures may be used to enhance the mechanical action of the viscoelasticliquid. Other functional additives like surfactants, solvents, emulsifiers ordispersing agents can be used as well.

[0067] The presentinvention also relates to the use of viscoelastic liquid to remove biofilm.

[0068] The inventionwill be described with reference to the use of a flowable, conveyableviscoelastic liquid for endoscope cleaning. Based on the teaching of thepresent invention it will be understood by those skilled in the art that theinvention may be embodied in other forms and may utilise other liquids,suspensions or emulsions in the cleaning of endoscopes and other instrumentswithout departing from the concepts herein described. For instance, the methodsof the present invention are useful in cleaning other lines or surfacessusceptible to contamination. Particularly, the methods of the presentinvention are useful in cleaning waterlines, such as those used in the food,cosmetic, dental and beverage industries. Such lines are very susceptible tobiofilm contamination.

[0069] The inventionusing viscoelastic liquid is described with reference to specific examples,however, it will be appreciated by those skilled in the art that the processis, in very large part, a physical process rather than a chemical process, so theexact chemical nature of the components is not critical but, rather, theresultant physical properties of the mixture that arise from theinterrelationship of the components. Nevertheless, if reasonably practicable,physical action of the viscoelastic liquid can be enhanced with some chemicalprocesses. E.g. the enzymatic detergent can be used in combination with theviscoelastic liquid to achieve some specific claims like the removal of fixedprotein.

[0070] The physicalproperties of the mixture that give rise to the desirable cleaning effectinclude the rotational yield point, the peak viscosity, the oscillatory flowpoint and the friction factor.

[0071] The cleaningformulations of the present invention preferably have the following rheologicaland tribological properties at 21 °C:

[0072] a rotationalyield point between 140% strain and 300% strain;

[0073] a peakviscosity between 550 Pa s and 2000 Pa s;

[0074] anoscillatory flow point between 250 and 700 % strain; and

[0075] coefficientof friction m which has a maximum value in the viscoelastic liquid’selastohydrodynamic region.

[0076] Thecoefficient of friction is preferably in the range of 0.06 to 0.15 at avelocity of 0.1 m/s

[0077] Being pumpedat shear rates below the flow point, the viscoelastic liquid moves in itspredominantly elastic state providing mechanical forces to the internalsurfaces of the endoscope and pushing soils out. The viscoelastic liquid byitself has no abrasion properties. As mentioned above, other functionalingredients, e.g. hydrophilic fumed silica can be used to further optimiserheology and/or enhance cleaning efficacy via the adsorption of soils due totheir high surface area, provide additional scrubbing due to their abrasivenature (such as provided by suspended crystalline inorganic materials) or workas solubilising/emulsifying ingredients (like surfactants or solvents) for theresidues of lubricants in the endoscope. To achieve the desired cleaningefficacy, the flow rate of viscoelastic liquid along the surface is controlledsuch that the viscoelastic liquid’s elastic modulus G’ exceeds the viscousmodulus G”. If excessive shear or stress is applied to a viscoelastic liquid,it turns from an elastic state to a viscous state (G”>G’) and in doing soflows more like a Newtonian fluid. In such a case, there is a loss of structureand a loss of cleaning efficiency.

[0078] The peakviscosity between 550 Pa s and 2000 Pa s is optimised for lumens having ID'sbetween 0.9 and 3.7mm. Viscosities outside this range, i.e. those with higherviscosities can still provide good cleaning, however, there may be issuesregarding pumpability. A cleaning agent with a peak viscosity above 2000 Pa swill be suitable for 3.7 mm lumens or larger, but may have limited pumpabilitythrough a 0.9 mm lumen if remaining within the pressure range specified by theendoscope manufacturer. In the case of a viscoelastic liquid, any combinationof chemicals that serves to provide the desired viscoelastic rheology profile(G’/G” ratio, yield point, viscosity, thixotropy, recovery time after the shearstress) may be used.

[0079] The tribologyof the formulations of the present invention is also important. Particularly,it is important that each formulation of the present invention showed a maximumin their coefficient of friction when the mixture was in a condition ofelastohydrodynamic friction. This particular region is well understood by thosefamiliar with tribology and the information is typically presented in aStribeck curve, as discussed in more detail below.

[0080] Incombination with other functional ingredients, the preferable solid content isin the range of 0.1 to 40% by weight. The viscoelastic liquid can be waterbased or other media can be used to disperse/dissolve the polymers and functionalingredients. The viscoelastic liquid may include just one polymer or acombination of several polymers or contain in addition any inorganic/organicrheology modifiers to change one or more properties such as G’ (elasticmodulus), G” (viscous modulus), yield point, viscosity, thixotropic properties,lubricating properties, recovery time after the shear stress, temperaturesensitivity of the rheology properties, shear thinning or shear thickeningbehaviour. The polymer may have anionic, cationic, nonionic or amphotericnature and be, for example, any carbomer or cross-linked acrylic polymer. Otherinorganic and/or organic materials, for example hydrophilic fumed Silica, canalso be used as rheology modifiers to achieve the desired viscoelastic profile.

[0081] In anotherembodiment of the present invention the viscoelastic liquid cleaning can becombined with a chemical and/or enzymatic clean to complement the physicalcleaning of the viscoelastic liquid. The chemical and/or enzymatic cleaning maybe conducted before and/or after pumping the viscoelastic liquid or may involveintermediate rinsing. Additional rinsing with water and/or drying steps may becarried out as necessary.

[0082] The nature ofadditives, including the surface area, morphology, crystallinity, particlesize, particle size distribution, emulsification properties and suspendingproperties have also been shown to contribute to the cleaning effect. Theadditives may be for example hydrophilic fumed silica grades (nanocrystallineor larger sized) or suspended insoluble particles (like crystalline silica,crystalline alumina, crystalline zirconia, activated carbon, calcium carbonate,or ceramics), sodium acrylate, anionic, amphoteric and non-ionic surfactants ortheir mixtures. Again, the density, nature, size, morphology and concentrationof additives can be selected for optimal cleaning. For example, wettingbehaviour of viscoelastic fluids can be tuned with ethoxylated fatty alcohols.On the other hand, an additional efficacy in the removal of oils and lubricantscan be granted with non-ionic or anionic emulsifiers. And the use of suspendedinorganic crystalline abrasive particles can enhance the cleaning efficacy inremoval of fixed protein. Importantly, the abrasion properties will depend stronglyon particle sizes and hardness of suspended particles.

[0083] The inventionwill be described with reference to the conveyable viscoelastic liquid beingconveyed by pumping (i.e. pushed) but a conveyable viscoelastic liquid mayequally be conveyed by way of reduced pressure or suction (i.e. pulled).

[0084] Whenviscoelastic liquid is used, the solid fraction is between 0.1 and 40% w/w,more particularly between 0.2 and 15% w/w and even more particularly between0.4 and 5% w/w. The viscoelastic liquid needs to flow through all lumens of theendoscope independently on their internal diameter and it is desirable to havea viscosity and yield value that allows good flowability and pumpability incombination with a suitable viscoelastic profile, absorption, emulsificationand abrasive properties. 550 to 2000 Pa s peak viscosity at ambient temperature(as measured with Anton Paar MCR 102 modular compact rheometer) is a suitableviscosity. The desired rotational yield point at 21 °C is in the range of 140to 300% of strain. If necessary different rheology modifiers such as fumedSilica, clays, polymers, gums, dispersing agents, electrolytes or solvents canbe used to change the rheological profile of the viscoelastic liquid, such as,by modifying its viscoelastic profile, flowability, pumpability or to assist inthe formation of a stable system. It is also important that the viscoelasticliquid have the correct tribology, or friction, in combination with the correctrheology. A high friction viscoelastic liquid is desirable, for example, thevicoelastic liquid has a coefficient of friction of 0.06 or greater in theelastohydrodynamic region (the elastohydrodynamic region for any given fluid isclearly identifiable from its Stribeck curve. Typically, the elastohydrodynamicregion for the viscoelastic fluids of the present invention is considered as asliding velocity in the range between 0.004 m/s to 1 .0 m/s. An overly highfriction viscoelastic liquid will require higher pumping pressures, and sowhile useful for cleaning, may only be pumpable at pressures that exceed themanufacturer’s pressure ceilings in endoscopes. The coefficient of friction mmay for example have a maximum value in the range 0.005-1 .0 m/s or 0.01 -0.3m/s or 0.5 to 0.15 m/s. The maximum value for the coefficient of friction m isindependently 0.06 or greater (for instance 0.06-1) or 0.1 or greater (forinstance 0.1 -1) or 0.12 or greater (for instance 0.12 or greater).

[0085] For instance,the coefficient of friction m may for example have a maximum value 0.06 orgreater (for instance 0.06-1) in the range 0.005-1 .0 m/s. Alternatively, thecoefficient of friction m may for example have a maximum value 0.1 or greater(for instance 0.06-1) in the range 0.01 -0.3 m/s or alternatively thecoefficient of friction m may for example have a maximum value 0.12 or greater(for instance 0.06-1) in the range 0.5 to 0.15 m/s.

[0086] Typically,the coefficient of friction would usually be in the range of 0.06 to 0.15 at avelocity of

[0087] 0.1 m/s.

[0088] It isnecessary that the viscoelastic liquid flow across the surface in order for thesurface to be cleaned. However, beyond that, it is advantageous that theviscoelastic liquid be flowed across the surface as slowly as practicable. Thepresent inventors have established that the lower the flower rate, the betterthe cleaning efficacy that can be achieved. Increasing the flow rate isundesirable as it decreases the contact time available for cleaning and alsobecause increasing the flow rate contributes overshearing of the formulationwhich means that at a certain point it will stop working.

[0089] It has beenestablished that 3 ml/min is an optimal flow rate for 3.7 mm lumens in order toachieve a suitable compromise between the cleaning efficacy/cleaning agentvolume and cleaning cycle time. Under standard conditions, to clean a 10 cmlength of 3.7 mm lumen it is necessary to pump 30 ml of the viscoelastic liquidat 3 ml/min to get the desired cleaning efficacy. If more viscoelastic liquidis pumped, or if the flow rate is reduced the cleaning efficacy will improvebut the cleaning cycle time will increase significantly. On the other hand,increased flow rate can be compensated to a certain extent by increasedviscoelastic liquid volume. Also, it needs to be kept in mind that in the caseof endoscopes, a manufacturer pressure ceiling exists. In practical terms, forsmaller lumens (0.9 mm) the pressure ceiling is reached even at very slow flowrates of 1 -2 ml/min. In general, the relationship is that for an endoscopelumen of x mm diameter, the flow rate should be in the range of 0.5 x ml/min -2 x ml/min.

[0090] It would beexpected that those skilled in the art would readily be able to optimise theflow rate for any given lumen size taking into account the factors mentionedabove.

[0091] Those skilledin the art will also be aware that pumping viscoelastic liquids and so on athigh velocities will lead to overshearing. In the field of endoscopy,overshearing is unlikely since adherence to the pressure ceilings (as describedabove) would mitigate against high speed, high pressure pumping of the paste. Assumingthe agent is not flowed at an oversheared velocity, the total material flowacross the surface is not the main parameter driving cleaning efficiency. It isimportant that the cleaning agent is pumped under plug flow conditions (in therange between the yield point and flow point). Figure 1 illustrates thedifference between the plug flow of the present invention (where the fluid actsas plug or plunger to mechanically clean the lumen), and liquid flow, where thefluid simply flows around the soil with little or no interaction. For example,pumping 30 ml of paste at 3 ml/min will provide a certain cleaning efficacy,but a similar cleaning efficacy can be achieved by pumping less cleaning agentat e.g. 2 ml/min or pump more cleaning agent at e.g. 4 ml/min, for example,thus, the mass flow in all three cases will be different but cleaning efficacycan be the same.

[0092] In oneembodiment, the viscoelastic liquid is premixed and provided as stable andready to use material in a cartridge, flexible bag, bottle, canister or anyother suitable packaging. The packaging containing the viscoelastic liquid isplaced in line with the endoscope and the viscoelastic liquid is simply pumpedfrom the packaging with the controlled flow rate with suitable pumps, e.g. peristalticpumps, into lumens, cylinders, valve sockets and connectors of the endoscope asshown on figure 2. The viscoelastic liquid is passed through the endoscope fora suitable time to remove the biological material, depending upon the initiallevel of contamination and the construction of the endoscope.

[0093] Theembodiment in figure 2 shows the bench-top model of the endoscope when theviscoelastic liquid is pumped simultaneously or sequentially through all valvesockets and connectors of the suction biopsy line. The same setup is used forthe bench-top testing of air/water and auxiliary lines of the endoscope. Whilepumping the viscoelastic liquid the pressure sensors are used to ensure thatthe specified pressure ceiling is not exceeded during the endoscope cleaningprocess. These pressure sensors can be connected to a feedback or controlmechanism to shut off the pumps should the pressure begin to approach levelsthat may damage the endoscope. The viscoelastic liquid flows down the desiredendoscope channel and may be discharged via an exit line into a drain.

[0094] The samepumps and pressure sensors are used to provide a wash with water and/orenzymatic detergent before and/or after the physical cleaning with theviscoelastic liquid. The pre-flush and/or post-flush with water and/orenzymatic detergent is optional but it may enhance further the cleaningefficacy achieved with the viscoelastic liquid by itself, especially in thepresence of hard soils like fixed proteins and/or any dry soils. The temperatureof water and/or enzymatic detergent can be independently optimised by theinclusion of a thermostatic mixer, in-line heater or any other type of heater.The enzymatic detergent passes through the channels of the endoscope and may bedischarged via an exit line into a drain. Once the cleaning cycle has finished,the endoscope can be purged with air or dried in any other suitable manner.

[0095] Theviscoelastic liquid may also contain functional chemicals to tune itscharacteristics. For example, broad spectrum preservative, e.g. PhenoxyEthanol, can be used to achieve the desired shelf life and preventmicrobiological contamination of the viscoelastic liquid during handling,storage and transportation. Different absorbing materials, e.g. high surfacearea fumed Silica or activated Carbon can be used to enhance the cleaningefficacy via physical absorption of the soil. Surfactants, solvents oremulsifiers can be used to modify wetting behaviour and surface tension tosupport the removal of lubricants from the endoscope. Also suspended abrasivematerials, can be used to enhance the efficacy of viscoelastic liquid inremoval of hard soils like fixed proteins. For example, dispersedmicrocrystalline Silica (20-200 mhi) supports the removal of fixed protein dueto its additional abrasion properties.