Patent Description:
The present subject matter relates to the technical field of surface coatings for solid and porous surfaces, and specifically to coating materials possessing a combination of antimicrobial, contact-killing and anti-adhesion properties. The details of the methods of preparation, as well as the properties and performances of the coating, are also disclosed.

Globally, according to the World Health Organization, waterborne disease and water related disease are leading killers resulting in more than <NUM> million deaths annually. Water sources and surfaces exposed to water are susceptible to contamination and fouling, even in closed systems, from the development of biofilms which act as key reservoirs for microbial contaminations. Water filtration membranes employed for water purification and to safeguard drinking water from contaminants are easily affected, because microbes present in the water can colonize the membrane resulting in biofouling. Biofouling can lead to a serious and significant loss in performance and a shortening of operational lifetime of the membrane, and contaminated membranes can become reservoirs for opportunistic pathogens. As a result, filtration membranes designed with anti-fouling properties have been widely investigated.

<CIT> (<CIT>) describes a complex, hydrophilic-like composition made mainly of hydrophilic polymer, polyphenolic compound and surfactant coated on perm-selective membrane designed to resist fouling from waterborne contaminants. <CIT> (<CIT>) describes a process for chemically modifying a preformed polybenzimidazole semipermeable membrane based on sulfonating the membrane resulting in an increased resistance to fouling. <CIT> (<CIT>) describes a reverse osmosis composite membrane with a high fouling tolerance provided by coating aromatic polyamide with polyvinyl alcohol. <CIT> (<CIT>) describes a composite membrane with a porous support and a crosslinked polyamide surface having polyalkylene oxide groups grafted thereto exhibiting improved resistance to fouling. <CIT> (<CIT>) describes a composite membrane with a cross-linkable polymer comprising a poly(meth)acrylate and/or poly(meth)acrylamide backbone and a multi-functional acid halide crosslinking agent with anti-fouling properties. <CIT> (<CIT>) describes a filtration membrane coated with a polymer comprising a benzenediol or a substituted phenol with anti-fouling properties requiring repetitive cleaning and reapplication for long-term use. <CIT> (<CIT>) describes a selective membrane with high fouling resistance using hydrophilic coatings on reverse-osmosis membranes.

Other surfaces at risk for biofouling and microbial growth include municipal drinking water distribution pipe networks and holding tanks. Sewers and drainage systems, heat exchangers and cooling towers also provide environments favorable to the formation of biofilms. A <NUM> thick microbial surface layer is estimated to result in <NUM>% energy loss in cooling tower systems. Accordingly, protective coatings for these solid surfaces have been developed.

<CIT> describes an antifouling paint composed mainly of copper and zinc ions. <CIT> (<CIT>) describes an anti-biofouling coating for use in contact with water composed of a macromolecular scaffold containing reactive groups capable of undergoing a Michael-type reaction. <CIT> (<CIT>) describes an anti-biofouling coating containing a polysiloxane-based polymer and cylindrical nanofiller released particles into the water. <CIT> (<CIT>) describes a biomimetic agent for anti-biofouling composed of an anchoring moiety allowing for surface attachment and a zwitterionic moiety exhibiting anti-biofouling activity.

Moreover, <CIT> is drawn to an antimicrobial coating according to the prior art, where the antimicrobial coating includes inorganic-organic shells formed from a combination of nonionic polymers and inorganic materials.

Further, <CIT> is drawn to an antimicrobial composition according to the prior art, where the antimicrobial composition includes metallic nanoparticles encapsulated in chitosan.

Furthermore, <CIT> is drawn to anti-fouling treatments applied to polymer substrates according to the prior art, where the anti-fouling treatment includes an anti-biofilm agent in a hydrogel polymer, where the anti-biofilm agent is further encapsulated in a polymer.

In addition, <CIT> is drawn to a generalized production method for microcapsules according to the prior art, where one of the reactants used in an interfacial reaction to form a membrane includes anhydride moieties.

Currently, there remains a need in the art for antimicrobial and anti-biofouling coatings with long term activities which are capable of application to both solid and nonsolid surfaces. The present subject matter is directed to colloidal antimicrobial and anti-biofouling coatings for both reversible and irreversible coating on solid and porous surfaces affording wide-spectrum antimicrobial properties, arresting microbial biofilm formation and preventing biofouling. The present coating is designed for a variety of applications, and especially ideal for coating water filtration membranes, pipes, tubing and other surfaces in contact with water, as well as textiles and other porous media including air particulate filters. The present compositions are also effective as antimicrobial and anti-biofouling coatings for solid and porous surfaces exposed to air. The colloidal antimicrobial and anti-biofouling coatings are capable of storing and releasing disinfectants, biocides and fragrances.

The present subject matter relates to an antimicrobial and anti-biofouling coating formulation, comprising:.

In another aspect, the present subject matter relates to a method of producing antimicrobial and anti-biofouling coating for application to nonporous surfaces, porous membranes or porous materials, comprising:.

The compositions and methods of the present subject matter address the problems and issues of the prior art compositions and methods, as provided in more detail accordingly.

The present chemical compositions are colloidal antimicrobial and anti-biofouling coatings, having ideal physical characteristics for application to solid and porous surfaces exposed to air and water/liquid environments. Biofouling or biological fouling is generally defined as the accumulation of microorganisms, plants, algae, or animals on wetted surfaces.

The present coating is a colloidal suspension of hollow, round particles comprising at least two or more polymers such as functionalized biopolymers, phosphatidylcholine as well as polymer chains containing primary, secondary and/or tertiary amines and zwitterionic groups. The preparation of the coating compositions is such that the polymers self-assembled into hollow round particles at a given concentration and pH. The particle size can be controlled with the use of a stabilizer and/or also through cross-linking. The hollow, round particles can contain cores of either inert or active ingredients. An inert (non-antimicrobial) core may contain, for example, water or an inert solvent. An active (antimicrobial) core may contain, for example, one or more disinfectants, biocides-and fragrances.

The stabilizer can be selected from polyvinyl alcohol (PVA) and/or polyethylene glycol (PEG) derivatives, as well as polymers with PVA or PEG groups can be applied. In the present invention, the stabilizers are present as about <NUM>-<NUM>% (w/v) of PVA mw <NUM>,<NUM>-<NUM>,<NUM>/mol; about <NUM>-<NUM>% (w/v) of PEGMA Mn=<NUM>-<NUM>, preferably <NUM>; and about <NUM>-<NUM>% (w/v) of MPEGMAMn=<NUM>-<NUM>, preferably <NUM>.

The coating of surfaces can be accomplished by spray-coating, dip-coating, wash-coating and wiping, or via use of chemical linkers. Complex coatings can be assembled using a layer-by-layer coating method. Furthermore, paint and epoxy resin coatings containing the instant colloids can directly applied on surfaces. In all case, the instant coatings are stable in air and water, and resist erosion by water flow. The coating is designed to be safe and effective for industrial, commercial, municipal and household usage.

Colloidal antimicrobial and anti-biofouling coatings comprise polymers include, but are not limited to, active polymers such as polyethylenimine (PEI), poly(diallyldimethylammonium chloride) (PDDA), polyhexamethylene biguanide (PHMB). It is contemplated that specific active polymers are defined as those having low adhesion properties and/or beneficial antimicrobial properties.

Chemical cross-linking can attach L-α-phosphatidylcholine (EGG), <NUM>-(diethylamino)ethylmethacrylate (NR3), [<NUM>-(methacryloylamino)propyl)dimethyl -(<NUM>-sulfopropyl)ammonium hydroxide (NR4) and <NUM>-sulfopropyl methacrylate (SO3) onto the main polymer materials. Detailed methods of preparation are described in Examples <NUM>-<NUM> as described after discussion regarding the Figures.

The following discussion of the Figures references the Examples as described in the following section. Reference is made to specific Examples. It is to be noted that all Figures and Examples are not meant to be limiting to the subject matter claimed in the appended claims.

The colloids of the instant coatings can range in size to accommodate different coating functions. For example, increasing colloid size can increase water flux when the coatings are used in a filtering application as shown in <FIG>. Various factors influence the size of the colloid particles. For example, the size of the colloidal particles can be controlled by adjusting the molecular weight of the constituent polymers. <FIG> shows a series of optical microscopy images of PEI colloidal antimicrobial and anti-biofouling coating formulations: <NUM>% PEI (Mn <NUM>,<NUM>), <NUM>% PEI (Mn <NUM>,<NUM>) and <NUM>% PEI (Mn <NUM>,<NUM>). PEI with lower molecular weight (ca. <NUM>,<NUM>/mol) formed <NUM> micron colloids, whereas PEI with higher molecular weight (ca. <NUM>,<NUM>/mol) formed <NUM> micron colloids. Increasing the amount of constituent polymer, in <FIG>% PEI (mw <NUM>,<NUM>), also modifies the size of the colloidal particles. In the case of polymers, molecular weight (mw) means average molecular weight. Varying the compositional ratios of active polymers also varies the particle size. From left to right, the particle sizes were <NUM>, <NUM>, <NUM> and <NUM>. In <FIG>, the colloidal PEI-PHMB antimicrobial and anti-biofouling coating, was prepared with different compositional ratios of PEI and PHMB ((a) <NUM>:<NUM>, (b) <NUM>:<NUM>, (c) <NUM>:<NUM> and (d) <NUM>:<NUM>), thereby varying the colloidal particle size from <NUM>-<NUM> microns. Specifically, in <FIG>, the particle sizes achieved were (a) <NUM>, (b) <NUM>-<NUM>, (c) <NUM>-<NUM> and (d) <NUM>.

The particle size can be controlled with cross-linking, which increases the polymer length and grafts different functional moieties or polymers to create new properties and functions. This approach can be used to incorporate zwitterionic molecules, metal biocides and biocidal proteins and enzymes to the primary polymer. For example, PEI can be cross-linked according to the general reaction shown in <FIG>.

Colloidal particle size can also be controlled with the use of stabilizer and is also influenced to a lesser extent by the pH and concentration. Table <NUM> shows colloidal antimicrobial and anti-biofouling coating comprising of different concentrations of PEI and PHMB.

The colloid particle size may further be varied to accommodate an active core material. Microscopy images (<FIG> and <FIG>) confirm that the instant colloidal particles of the antimicrobial and anti-biofouling coating are round and hollow, and thereby capable of containing an active core material. An active core material can be, for example, essential oils, fragrances, biocides and/or disinfectants. Biocides include with polyols, such as farnesol, cinnamaldehyde, and thyme oil, as well as mixed biocides (thyme oil, cinnamaldehyde and farnesol). Some active cores may be essential oils, which are active as fragrances, disinfectants and biocides. Methods of preparing colloidal particles containing, storing and releasing essential oil, fragrance, biocide and disinfectant in formulated coatings are found in Examples <NUM>-<NUM>. <FIG> and <FIG> show the colloidal antimicrobial and anti-biofouling coating formulation containing thyme oil. PEI, PHMB and PEI-PHMB colloids and thyme oil were successfully formulated (Examples <NUM>-<NUM>). The particle sizes, in <FIG>, were (a) <NUM>-<NUM> and (b) <NUM>. In <FIG>, the particle sizes were (a) <NUM>-<NUM>, (b) <NUM>-<NUM> and (c) <NUM>-<NUM>. When active cores are employed, the instant coating can be a stable colloid suspension form (<FIG>) for PEI with cinnamaldehyde, farnesol and mixed biocides (thyme oil, cinnamaldehyde and farnesol) as non-limiting examples. Other active core combinations possible according to the instant subject matter utilize the hollow region of the colloidal particles for containing, encapsulating, storing and releasing active materials that include ions, molecules and biomolecules for the purpose of disinfection and inhibition of microbial contaminations.

An example coating formulation comprises, by weight:.

Accordingly, a particular range of total active polymer is <NUM>-<NUM>% (w/v). Ideally, the active polymers are present at <NUM>-<NUM> w% in a ratio of <NUM>-<NUM>:<NUM>-<NUM>.

<FIG> shows the bactericidal properties of PEI (Example <NUM>), PDDA and PEI-PDDA (Example <NUM>) for S. aureus and P. aeruginosa. A <NUM>% (<NUM> Log) reduction in viable S. aureus was obtained from the PEI-PDDA coating (<NUM>% for PEI and <NUM>% for PDDA), and a modest <NUM>% reduction for the P. aeruginosa. <FIG> describes similar bactericidal test on PHMB, PDDA and PHMB-PDDA (Example <NUM>) for S. aureus and P. aeruginosa. A <NUM>% (<NUM> Log) reduction in viable S. aureus was obtained from PHMB-PDDA coating (<NUM>% for PHMB and <NUM>% for PDDA), and a modest <NUM>% reduction for the P. aeruginosa (<NUM>% for PHMB and <NUM>% for PDDA). <FIG> shows the results for PEI, PHMB and PEI-PHMB (Example <NUM>) for S. aureus and P. aeruginosa. A <NUM>% (<NUM> Log) reduction in viable S. aureus was obtained from PEI-PHMB coating (<NUM>% for PEI and <NUM>% for PHMB), and a similar <NUM>% (<NUM> Log) reduction in the P. aeruginosa biofilm-forming (<NUM>% for PEI and <NUM>% for PHMB). In the latter case, a synergistic effect of the combination of PEI-PHMB is shown. <FIG> plots the bactericidal activities of PEI, PHMB, PEI-PHMB coatings (Examples <NUM>-<NUM>) for S. subtilis, E. coli and P. aeruginosa. PEI-PHMB coatings maintained <NUM> % (<NUM> Log) reduction in viable bacteria.

<FIG> illustrates one approach for coating water filtration membranes, such as reverse osmosis (Example <NUM>), nanofiltration (Example <NUM>), ultrafiltration (Example <NUM>) and microfiltration membranes (Example <NUM>) with the instant colloidal antimicrobial and anti-biofouling coating. The method comprises introducing the coating to the membrane through the retentate stream, depositing the colloidal particles via filtration onto the membrane surface and subsequently attached. This method imparts antimicrobial and anti-biofouling properties to the coated membrane. An advantage of this method is that the coating can be simply carried out even in operating membrane system without interruption. The coating can be dislodged by acidic backwashing. Table <NUM> shows the retention of colloidal antimicrobial and anti-biofouling coating on nanofiltration membranes.

<FIG> compares the antimicrobial properties of two commercial tin-based anti-biofoulants (<NUM>,<NUM>-dibromo-<NUM>-nitrilopropionamide (DBNPA) aqueous solutions with different concentrations, Dow) and two PEI coatings (Example <NUM>) on a nanofiltration membrane. Membranes treated with the commercial anti-biofoulants had low bactericidal properties (<NUM>% and <NUM>% reduction in activity), whereas the instant colloidal PEI coatings can achieve better than <NUM>% reduction in viable bacteria. <FIG> shows the instant colloidal PEI-PHMB coating (Examples <NUM> and <NUM>) can maintain better than <NUM>% reduction in bacteria compared to uncoated nanofiltration membrane even at very low coating amount. <FIG> includes a series of SEM images taken over <NUM>-day period of membrane samples immersed in bacterial culture. The microbial attachment on the nanofiltration membrane coated with the instant colloidal PEI (Example <NUM>) is negligible compared to uncoated membrane and membrane treated with commercial anti-biofoulant (DBPNA, Dow). These studies confirmed that the colloidal coating is both antimicrobial and anti-biofouling. <FIG> follows the biofilm growth on nanofiltration membrane for both uncoated and PEI-PHMB coated samples (Examples <NUM> and <NUM>) at estimated E. coli concentrations of <NUM> CFU/cm<NUM> and <NUM> for uncoated and coated samples. The coated membrane was free of E. coli bacteria. <FIG> shows the effects of the colloidal PEI-PHMB coatings on water flux. A <NUM>% reduction in viable E. coli was maintained in all three formulations, but the size of the colloid particles was increased from <NUM> to <NUM> and <NUM> microns. Using larger colloids with the same amount of coating can ameliorate the effect of coating on water flux. Table <NUM> shows that the membrane rejection/retention rate was improved with the coating. Rejection data of uncoated and coated membranes shown in Table <NUM> was produced using methyl orange solution.

<FIG> plots the bactericidal properties of colloidal PEGDA crosslinked with unmodified chitosan (CHIT), L-α-phosphatidylcholine (EGG), <NUM>-(diethylamino)ethylmethacrylate (NR3), [<NUM>-(methacryloylamino)propyl)dimethyl -(<NUM>-sulfopropyl)ammonium hydroxide (NR4), <NUM>-sulfopropyl methacrylate (SO3), and lysozyme (LYN) (Example <NUM>). PEGDA served as an inert polymer in these samples to which different antimicrobial, anti-adhesion and anti-biofouling molecules could be crosslinked to. <FIG> shows the results of further bactericidal studies on EGG, NR3, NR4, and LYN at different compositions. NR3 performed best compared to EGG and LYN. NR4 had lower bactericidal activity, but exhibited excellent anti-adhesion properties. Uniform surface coating can be achieved by simply brush coating the colloidal antimicrobial and anti-biofouling coating (Example <NUM>) as indicated by the ToF-SIMS mapping images of the nanofiltration membrane surface in <FIG>.

<FIG> and <FIG> plot the antimicrobial and anti-biofouling results for an uncoated nanofiltration membrane, and nanofiltration membranes coated with colloidal PEGDA-NR3, PEGDA-NR4 and the PEGDA-NR3/NR4. <FIG> shows that nanofiltration membranes coated with colloidal PEGDA-NR3 and PEGDA-NR3/NR4 maintained <NUM>-<NUM>% less viable bacteria than an uncoated membrane even after multiple uses. <FIG> shows that although PEGDA-NR4 has significantly lower bactericidal activity, it prevented the adhesion of the bacteria on the membrane surface. The colloidal PEGDA-NR3/NR4 afforded a two-level antimicrobial activity through "contact-killing" and "anti-adhesion". <FIG> plots that water flux and dye rejection for the uncoated nanofiltration membrane and nanofiltration membrane coated with colloidal PEGDA-NR3/NR4. The water flux as shown in <FIG> was improved over the uncoated membrane due to increased surface hydrophilicity from NR4 without affecting the separation properties of the membrane as shown by the dye rejection experiment in <FIG>. Deliberate fouling of the membranes showed that the nanofiltration membrane coated with colloidal PEGDA-NR3/NR4 antimicrobial and antibiofouling coating was more resistant to biofouling. <FIG> plots the water flux and bacterial filtration by an uncoated microfiltration membrane and coated microfiltration membrane (Example <NUM>). It can be seen from the study that the coating did not alter the filtration properties of the membrane. Similarly, the microfiltration membrane coated with colloidal PEGDA-NR3/NR4 antimicrobial and antibiofouling coating was more resistant to biofouling. Accordingly, the instant coatings incorporate these and similar antimicrobial, anti-adhesion and anti-biofouling molecules and moieties into active polymers such as PEI, PHMB, PDDA, PQAC and similar antimicrobial polymers to construct colloidal multilevel antimicrobial and anti-biofouling coatings for surfaces.

The use of dopamine and similar materials as adhesion layer for the instant coating on surfaces is described in Example <NUM> and shown in the illustration of <FIG>. The dopamine adhesion layer binds with the colloidal coating via a Schiff based reaction between catechol groups and the amine or thiol groups of the polymers. Other molecular linkers, such as vinyl sulfone, can be attached the colloidal antimicrobial and anti-biofouling coating to the subject via "click chemistry". <FIG> shows the colloidal antimicrobial and anti-biofouling coating on substrates with dopamine adhesion layers including stainless steel, plastic PVC and glass (Example <NUM>). X-ray photoelectron spectroscopy of the stainless steel and plastic PVC samples in Table <NUM> shows that coating was successfully attached to the surfaces by the increased nitrogen content from the colloidal PEI-PHMB. Specifically, Table <NUM>(a) shows elemental analysis results by X-ray photoelectron spectroscopy of colloidal coating on stainless steel with dopamine adhesion layer after washing in water; and Table <NUM>(b) shows elemental analysis results by X-ray photoelectron spectroscopy of colloidal coating on plastic PVC with dopamine adhesion layer after washing in water.

There was no measurable decrease in nitrogen content on the surface after <NUM> days of water immersion during which the substrates were placed in distilled and deionized (DDI) water at <NUM> under rapid agitations to simulate flow environment. The results indicated that the coating is compatible for use in aquatic environment and is resistant to water corrosion and erosion.

<FIG> plots the bactericidal properties of colloidal antimicrobial and anti-biofouling coating (Example <NUM>) on substrate with dopamine adhesion layer. The plot shows the effects of the amount of coating per unit area on the bactericidal properties of the surface against Gram positive and Gram negative bacteria. The coating can attain better than <NUM>% reduction of viable bacteria at coating level of <NUM>/cm<NUM> (wet basis) or <NUM>/cm<NUM> PEI and <NUM>/cm<NUM> PHMB (dry basis). A <NUM>% (<NUM> Log) reduction of viable bacteria can be obtained at <NUM>/cm<NUM> (wet basis) or <NUM>/cm<NUM> PEI and <NUM>/cm<NUM> PHMB (dry basis). <FIG> plot the results of accelerated ageing on the coating and the resultant effects of the bactericidal properties on S. aureus and E. coli, respectively. Each experimental day was equivalent to <NUM> days immersion in water. The results show that the bactericidal activity can be maintained for a prolonged period of time, such as <NUM>-<NUM> days, more than <NUM> days and/or <NUM>-<NUM> days.

The anti-biofouling properties of colloidal antimicrobial and anti-biofouling coating (Example <NUM>) attached to dopamine adhesion layers on stainless steel and plastic PVC surfaces were evaluated by scanning electron microscopy in <FIG> and <FIG>, fluorescence microscopy in <FIG> and <FIG> and direct enumeration of viable bacteria by standard microbiology method in <FIG>. The coated and uncoated samples were immersed in <NUM><NUM> CFU/ml E. coli culture for <NUM> days. The results consistently show that there are less bacteria attachments on coated stainless steel and plastic PVC surfaces compared to the uncoated substrate as shown in <FIG> and <FIG>, and these bacteria display a difference in gross morphology compared to healthy E. <FIG> and <FIG> show significant colonization by microbial biofilm on uncoated surfaces of stainless steel and plastic PVC. The biofilms contained an organic matrix of both dead and viable bacteria cells. The coated surfaces displayed mainly fluorescence from the coating materials even after <NUM> days in bacteria culture. Viable bacteria were recovered from the surfaces, cultured and enumerated. The results shown in <FIG> indicate <NUM>% less bacteria from coated stainless steel and plastic PVC compared to the uncoated samples. These results confirmed the long-term antimicrobial and anti-biofouling properties of the in coating in a water environment.

The colloidal antimicrobial and anti-biofouling coating was applied to porous media including textiles and nonwoven fabrics. <FIG> shows the performance of the coated fabric against common environmental pathogens found in hospital environment under accelerated ageing. The ageing was carried out by exposing the fabric to high temperature (<NUM>) for a given duration followed by direct challenge with <NUM><NUM> CFU/ml bacterial solution for <NUM> contact time. The results show that the coated fabric retained high bactericidal activity after <NUM> days of accelerated ageing study. <FIG> shows the fabrics coated with low concentration of colloidal antimicrobial and anti-biofouling coating compared well to fabric treated with alcohol and bleach solution. The fabric can attain more than a <NUM>% reduction in viable bacteria in <NUM> contact time. <FIG> shows the fabric remained bactericidal following exposure to water under rapid agitation. Compared to fabric treated with ethanol, it maintained a better than <NUM>% bacterial reduction.

<FIG> shows a HEPA filter used in the air filtration study with half of the filter coated with the colloidal antimicrobial and anti-biofouling coating and the other half uncoated. Table <NUM>(a) shows that the micellar coating on air filter can reduce more than <NUM>% of bacteria via contact killing over a period of <NUM> days.

The antimicrobial performance reduces to <NUM>% over a period of <NUM> days, which may result from covered coating layer by dirt. <FIG> and Table <NUM>(b) also reports that the HEPA filter coated with thyme oil encapsulated by PEI-PHMB can reduce more than <NUM>% of bacteria via contact killing and release killing over a period of <NUM> days.

Compared to non-coated air filter sections, the coating layer can render bacteria nonviable when contacted with the coated surface.

The preparation of the epoxy-polymer coating materials was made on the basis of a normal anti-corrosion paint described in patent <CIT>. It complies with the relevant specification listed in Distribution equipment and protective materials for domestic and drinking water safety evaluation standard (<NUM>) and can be used for ship water containers, water distribution pipes, and food contacting containers. Table <NUM> shows the basic formula of an epoxy coating material:.

The amount of polymer coating on the stainless steel substrates is <NUM>/cm<NUM> (<FIG>). <FIG> shows the effect of the coating amount applied on the bactericidal properties of the coating. The bactericidal performance can achieve greater than <NUM>% when the coating is over <NUM>/cm<NUM>. <FIG> shows the adhesion of bacteria on uncoated stainless steel compared to the absence of bacteria on stainless steel coated with epoxy coating-<NUM> (Example <NUM>) and coating-<NUM> (Example <NUM>).

<FIG> confirmed both coatings can attain <NUM>% reduction of bacterial attachment over a period of <NUM> days. An accelerated ageing study carried out after immersion of the coated stainless steel in water showed that the coating eroded slowly and that bactericidal activity can be maintained for a prolonged period of time.

Only examples which describe a formulation containing a hollow round colloidal structure that comprises at least two active polymers selected from PEI, PDDA and PHMB, and stabilizers as defined in claim <NUM> are illustrative of the invention. The remaining ones are to be considered as reference examples.

Polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was used to prepare a colloidal antimicrobial and anti-biofouling coating. Briefly, the polymer was dissolved in distilled water to prepare a PEI solution with concentration of <NUM> wt% to <NUM> wt%. The PEI solution was then added to a polyvinyl alcohol (PVA) solution containing <NUM> wt% to <NUM> wt% polymer in volume ratios from <NUM>:<NUM> to <NUM>:<NUM>. Drop-by-drop addition under rapid stirring followed by ultrasonic treatment for <NUM> produces the colloidal materials shown in <FIG>.

The biopolymer chitosan and functionalized chitosan of molecular weight <NUM> to <NUM>/mol were used to prepare a colloidal antimicrobial and anti-biofouling coating. Briefly, the polymer was dissolved in distilled water to prepare a biopolymer solution with concentration of <NUM> wt% to <NUM> wt%. The biopolymer solution was then added to a polyvinyl alcohol (PVA) solution containing <NUM> wt% to <NUM> wt% polymer in volume ratios from <NUM>:<NUM> to <NUM>:<NUM>. Drop-by-drop addition under rapid stirring followed by ultrasonic treatment for <NUM> produces the colloidal material.

Polyquaterniums including hydroxyethylcellulose ethoxylate, poly[(<NUM>-ethyldimethyl-ammonioethyl methacrylate ethyl sulfate)-co-(<NUM>-vinylpyrrolidone)], and poly[(<NUM>-methyl-<NUM>-vinylimidazolium chloride)-co-(<NUM>-vinylpyrrolidone)] of molecular weights ranging from <NUM> to <NUM>/mol were used to prepare a colloidal antimicrobial and anti-biofouling coating. Briefly, the polymer was dissolved in distilled water to prepare the polyquaternium solution with concentration of <NUM> wt% to <NUM> wt%. The polyquaternium solution was then added to a polyvinyl alcohol (PVA) solution containing <NUM> wt% to <NUM> wt% polymer in volume ratios from <NUM>:<NUM> to <NUM>:<NUM>. Drop-by-drop addition under rapid stirring followed by ultrasonic treatment for <NUM> produces the colloidal material.

The shape and size of the colloid was adjusted by cross-linking the active polymers (<FIG>) with a third polymer such as poly(ethylene glycol) methacrylate or Poly(ethylene glycol) methyl ether methacrylate of molecular weight <NUM> to <NUM>/mol for PEI-based colloidal antimicrobial and anti-biofouling coating.

The polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The poly(diallyldimethylammonium chloride) (PDDA) with molecular weight of <NUM> - <NUM>/mol was dissolved in water to prepare a PDDA solution with concentrations of <NUM> wt% to <NUM> wt%. Equal volumes of PEI and PDDA solutions of same concentrations were rapidly mixed together followed by <NUM> ultrasonication to produce a colloidal PEI: PDDA of <NUM>:<NUM> ratio.

The polyhexamethylene biguanide (PHMB) with molecular weight of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. The poly(diallyldimethylammonium chloride) (PDDA) with molecular weight of <NUM> - <NUM>/mol was dissolved in water to prepare a PDDA solution with concentrations of <NUM> wt% to <NUM> wt%. Equal volumes of PHMB and PDDA solutions of same concentrations were rapidly mixed together followed by <NUM> ultrasonication to produce a colloidal PHMB: PDDA of <NUM>:<NUM> ratio.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. Equal volumes of PEI and PHMB solutions of same concentrations were rapidly mixed together followed by <NUM> ultrasonication to produce a colloidal PEI: PHMB of <NUM>:<NUM> ratio. The colloid was diluted to obtain a final PEI (<NUM>-<NUM> wt%) and PHMB (<NUM>-<NUM> wt%) concentrations of <NUM>-<NUM> wt%.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. Equal volumes of PEI and PHMB solutions were rapidly mixed together followed by <NUM> ultrasonication to produce a colloidal PEI: PHMB of <NUM>:<NUM> ratio as shown in <FIG>. The colloid was diluted to obtain a final PEI of <NUM>-<NUM> wt% and PHMB of <NUM>-<NUM> wt%.

The polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. Equal volumes of PEI and PHMB solutions were rapidly mixed together followed by <NUM> ultrasonication to produce a colloidal PEI: PHMB of <NUM>:<NUM> ratio. The colloid was diluted to obtain a final PEI of <NUM>-<NUM> wt% and PHMB of <NUM>% -<NUM>%.

The polyhexamethylene biguanide (PHMB) with molecular weight of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of thyme oil was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PHMB and thyme oil/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PHMB-encapsulated thyme oil. Tween <NUM> was added to stabilize the resulting colloid as shown in <FIG>.

The polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of thyme oil was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PEI and thyme oil/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PEI-encapsulated thyme oil. Tween <NUM> was added to stabilize the resulting colloid as shown in <FIG>.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of thyme oil was added to <NUM> to <NUM> wt% PVA solution and emulsified. A given amount of PEI solution was added followed by <NUM> ultrasonication, and the appropriate volume of PHMB solution was then added followed by another <NUM> ultrasonication to produce colloidal PEI: PHMB: thyme oil materials shown in <FIG>. Tween <NUM> was added to stabilize the resulting colloid.

The polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of cinnamaldehyde was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PEI and cinnamaldehyde/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PEI-encapsulated cinnamaldehyde. Tween <NUM> was added to stabilize the resulting colloid as shown in <FIG>.

The polyhexamethylene biguanide (PHMB) with molecular weight of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of cinnamaldehyde was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PHMB and cinnamaldehyde/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PHMB-encapsulated cinnamaldehyde. Tween <NUM> was added to stabilize the resulting colloid.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM>-<NUM>/mole was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of cinnamaldehyde was added to <NUM> to <NUM> wt% PVA solution and emulsified. A given amount of PEI solution was added followed by <NUM> ultrasonication, and the appropriate volume of PHMB solution was then added followed by another <NUM> ultrasonication to produce colloidal PEI: PHMB: cinnamaldehyde materials. Tween <NUM> was added to stabilize the resulting colloid.

The polyethylenimine (PEI) with molecular weight of <NUM> to <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of farnesol dissolved in DMSO/water solution to obtain <NUM> wt% to <NUM> wt%. The farnesol solution was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PEI and farnesol/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PEI-encapsulated farnesol. Tween <NUM> was added to stabilize the resulting colloid as shown in <FIG>.

The polyhexamethylene biguanide (PHMB) with molecular weight of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of farnesol dissolved in DMSO/water solution to obtain <NUM> wt% to <NUM> wt%. The farnesol solution was added to <NUM> to <NUM> wt% PVA solution and emulsified. Equal volumes of PHMB and farnesol/PVA solutions were rapidly mixed together followed by <NUM> ultrasonication to produce PHMB-encapsulated farnesol. Tween <NUM> was added to stabilize the resulting colloid.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A measured amount of farnesol dissolved in DMSO/water solution to obtain <NUM> wt% to <NUM> wt%. The farnesol solution was added to <NUM> to <NUM> wt% PVA solution and emulsified. A given amount of PEI solution was added followed by <NUM> ultrasonication, and the appropriate volume of PHMB solution was then added followed by another <NUM> ultrasonication to produce colloidal PEI: PHMB: farnesol materials. Tween <NUM> was added to stabilize the resulting colloid.

The polyethylenimine (PEI) with molecular weight of <NUM>/mol was dissolved in distilled water to prepare a PEI solution with concentrations of <NUM> wt% to <NUM> wt%. The polyhexamethylene biguanide (PHMB) with molecular of <NUM> - <NUM>/mol was dissolved in distilled water to prepare a PHMB solution with concentrations of <NUM> wt% to <NUM> wt%. A mixed biocide containing thyme oil, cinnamaldheyde and farnesol was prepared. The mixed biocides solution was added to <NUM> to <NUM> wt% PVA solution and emulsified. A given amount of PEI solution was added followed by <NUM> ultrasonication, and the appropriate volume of PHMB solution was then added followed by another <NUM> ultrasonication to produce colloidal PEI: PHMB: mixed biocides shown in <FIG>. Tween <NUM> was added to stabilize the resulting colloid.

The colloidal antimicrobial and anti-biofouling coating was coated on water filtration membranes by filtration. The process was carried out under <NUM> MPa transmembranepressure and the coating can be adjusted from <NUM> to <NUM> wt%. Coating can also be carried out via spray coating, wash-coating and dip-coating methods.

The colloidal antimicrobial and anti-biofouling coating was coated on RO membranes by dead-end filtration. The process was carried out under <NUM> MPa transmembrane pressure and the coating can be adjusted from <NUM> to <NUM> wt%. Coating can also be carried out via spray coating, wash-coating and dip-coating methods.

The colloidal antimicrobial and anti-biofouling coating was coated on nanofiltration membranes by dead-end filtration. The process was carried out under <NUM> MPa transmembranepressure and the coating can be adjusted from <NUM> to <NUM> wt%. Coating can also be carried out via spray coating, wash-coating and dip-coating methods.

The colloidal antimicrobial and anti-biofouling coating was coated on ultrafiltration membranes by dead-end filtration. The process was carried out under <NUM> MPa transmembrane pressure and the coating can be adjusted from <NUM> to <NUM> wt%. Coating can also be carried out via spray coating, wash-coating and dip-coating methods.

The colloidal antimicrobial and anti-biofouling coating was coated on microfiltration membranes by dead-end filtration. The process was carried out under <NUM> MPa transmembrane pressure and the coating can be adjusted from <NUM> to 10wt %. Coating can also be carried out via spray coating, wash-coating and dip-coating methods.

A colloidal antimicrobial and anti-biofouling coating prepared from cross-linking PEGDA polymer with L-α-phosphatidylcholine (EGG), <NUM>-(diethylamino)ethylmethacrylate (NR3), [<NUM>-(methacryloylamino)propyl)dimethyl(<NUM>-sulfopropyl)ammonium hydroxide (NR4), <NUM>-sulfopropyl methacrylate (SO3) and Lysozyme (LYN). The bactericidal activities of colloidal PEGDA-EGG, PEGDA-NR3, PEGDA-NR4, PEGDA-SO3, PEGDA-LYN as well as cross-linked with unmodified chitosan, PEGDA-CHI are reported in <FIG>. The colloidal coating was brush-coated onto nanofiltration membranes, but other coating methodologies including filtration, spray-coating, wash-coating and dip-coating techniques could also be used. The performance of PEGDA-NR3, PEGDA-NR4 and PEGDA-NR3/NR4 coated on nanofiltration membranes was plotted in <FIG>.

A colloidal antimicrobial and anti-biofouling coating prepared from cross-linking PEGDA polymer with L-α-phosphatidylcholine (EGG), <NUM>-(diethylamino)ethylmethacrylate (NR3), [<NUM>-(methacryloylamino)propyl)dimethyl(<NUM>-sulfopropyl)ammonium hydroxide (NR4), <NUM>-sulfopropyl methacrylate (SO3) and Lysozyme (LYN). The colloidal coating was spray-coated onto microfiltration membranes, but other coating methodologies including filtration, brush-coating, wash-coating and dip-coating techniques could also be used. The performance of PEGDA-NR3/NR4 coated on MF membranes was reported in <FIG>.

The colloidal antimicrobial and anti-biofouling coating was coated on surfaces with dopamine or similar molecular adhesion layer. A <NUM>/ml dopamine solution was prepared from tris-Hcl buffer (pH <NUM>) solution. The adhesion layer was coated on surface by spray-coating, brush-coating, wash-coating and dip-coating or similar methods. Excess dopamine was removed by rinsing and the sample was dried before coating with the colloidal antimicrobial and anti-biofouling coating as illustrated in <FIG>.

The colloidal antimicrobial and anti-biofouling coating was coated on surface with dopamine adhesion layer deposited on stainless steel, plastic PVC and glass (<FIG>). The coating on the surfaces was resistant to water even under agitation as indicated in an accelerated study in <FIG>. The antimicrobial and anti-biofouling properties were maintained even under high microbial contamination as indicated in <FIG>.

The colloidal antimicrobial and anti-biofouling coating was diluted by <NUM> and <NUM> times and applied onto textile materials via wet coating process. The coating can also be applied by spray-coating, dip-coating, and related coating methods. Furthermore, the coating can be added during the rinse cycle in machine washing of the textile fabrics.

The colloidal antimicrobial and anti-biofouling coating was coated onto hospital bed partition fabrics. <FIG> and <FIG> summarizes the bactericidal properties of the coated fabric against a range of Gram-positive and Gram-negative bacteria including pathogens and drug-resistant microorganisms. The result of accelerated ageing in <FIG> showed that the coated fabric remain bactericidal for long period of time. Repeated immersion in water under rapid agitation did not affect the bactericidal properties of the coated fabric (cf.

The colloidal antimicrobial and anti-biofouling coatings given in examples <NUM>-<NUM> and examples <NUM>-<NUM> were coated on particulate air filters including HEPA by a spray-coating method. Electrospraying method, dip-coating, wash-coating and related methods could also be used as an alternative. <FIG> is a picture of a HEPA filter spray coated with the colloidal <NUM> PEI: <NUM> PHMB coating and its antimicrobial properties for airborne bacteria.

A typical formulation was prepared by mixing <NUM> parts by volume of epoxy resin with <NUM>-<NUM> parts by volume of curing agent and <NUM>-<NUM> parts by volume of a colloidal antimicrobial and anti-biofouling coating in example <NUM>. A <NUM>-<NUM> parts by volume of solvent was added followed by rapidly mixing.

The epoxy coatings described in examples <NUM> & <NUM> were coated onto stainless steel chucks as shown <FIG> and used for antimicrobial studies (<FIG>).

SEM images of initial membrane, membrane with antimicrobial formulation, initial substrates and substrates coated with antimicrobial formulations were made using JEOL JSM-<NUM> and JEM-6300F scanning electron microscopes equipped with energy dispersive X-ray detectors.

Analyses of element composition on initial substrates and substrates coated with antimicrobial formulation were made using Model PHI <NUM> (Physical Electronics), equipped with multi- technique system (AES, SAM, XPS).

Analyses of distribution of biofouling on initial substrates and substrates coated with antimicrobial formulation were made using Nikon TE2000E-PFS. • Dual-View Micro-imager.

Bacteria prepared from re-culture were diluted to <NUM><NUM> CFU/mL. <NUM>µL of the diluent was dropped on each of the carrier. A timer was used to monitor the contact time of the carrier with bacteria. Afterwards, the carriers were transferred to a sterile bottle containing <NUM> of neutralizer solution; <NUM>% (W/V) NaCl, <NUM>% w/v tween <NUM> and <NUM> sodium thiosulphate. It was allowed for incubation for <NUM> minutes.

Bacteria were serially diluted with sterilized saline solution if necessary. <NUM>µL of the solution was inoculated into TSA agar and cultured for <NUM> hours. The plates were taken out and enumerated by counting the colony forming unit (CFU).

In the anti-adhesion test, coated and uncoated membranes were exposed to <NUM><NUM> CFU/ml E. coli in nutrient broth under static batch conditions simulating worse possible scenario over a period of <NUM> days. After incubation, the membranes were gently washed with sterile DDI water to remove the suspended microbes. The washed membranes were then observed under scanning electron microscope (SEM) to search and estimate the density of adhered bacteria on the membrane surface. The SEM used was model JEOLJSM 6300F.

Water permeation was measured with a membrane in a dead-end filtration cell. Under the pressure of <NUM> kPa and at the feed temperature of <NUM>, the flux of deionized water was obtained from the volume of the permeated water within <NUM>. The acridine orange sieving tests were conducted on the membrane using the same device. Feed solutions with concentration of <NUM>/L were prepared. Under the pressure of <NUM> kPa and at the feed temperature of <NUM>, permeates were collected within <NUM>. The concentration of acridine orange in the feeds and permeates was measured by UV-vis. Rejection (R) before and after modification was calculated according to the equation R = <NUM> - Cp / Cf, where Cp and Cε are the UV-vis concentrations in permeate and feed, respectively.

The stain used to dye biofilms was Filmtracer™ LIVE/DEAD® Biofilm Viability Kit. The staining protocol followed the manufacturers' instructions. Briefly, the polymer micellar solution coated stainless steel and PVC samples were put into petri dish which contained <NUM> nutrient broth with E. coli of <NUM><NUM> CFU/ml. After culture, PBS was used to wash the non-attached bacteria off the substrate surface and transferred the rinsed substrates into a <NUM>-well plate. The working solution of stain was prepared by adding <NUM>µl of SYTO <NUM> and <NUM>µl of propidium iodide stain to <NUM> of filtered-sterilized water. Then add <NUM>µl stains which is mixed according to the manufacturer. The staining dish was incubated for <NUM>-<NUM> minutes in dark. After staining, the samples were rinsed with filtered-sterilized water for three times in order to remove all excess stain.

Tests were carried out to investigate the stability of the treated membrane. The treated membrane was installed in the cross-flow membrane filtration cell shown in <FIG> and retentate flow at <NUM> bar was maintained. The retentate was collected and analyzed for eluted anti-biofoulant by a colorimetric method using UV-Vis spectrometer. The results showed that the membrane retained better than <NUM> % of the filtered anti-biofoulant.

Claim 1:
An antimicrobial and anti-biofouling coating formulation, comprising:
a hollow round colloidal structure, comprising:
an active polymer shell; and
an active or inert core;
wherein the active polymer shell comprises two or more polymers with antimicrobial and anti-biofouling activities selected from the group consisting of polyethylenimine (PEI), poly(diallyldimethylammonium chloride) (PDDA) and polyhexamethylene biguanide (PHMB);
wherein either the core is active and contains one or more disinfectants, biocides and fragrances; or the core is inert and contains water or an inert solvent; and
wherein the hollow round colloidal structure further comprises stabilizers and is stable for at least <NUM> months, and wherein the stabilizers are present in concentrations of <NUM>-<NUM>% (w/v) of polyvinyl alcohol (PVA) having a mw of <NUM>,<NUM>-<NUM>,<NUM>/mol; <NUM>-<NUM>% (w/v) of poly(ethylene glycol) methacrylate (PEGMA) having a Mn of <NUM>-<NUM>; and <NUM>-<NUM>% (w/v) of methoxypoly(ethylene glycol) methacrylate (MPEGMA) having a Mn of <NUM>-<NUM>.