Developing antibacterial nanocoatings for textiles in health care

Martin Bennink1, Henk Gooijer2, Ger Brinks2

1 NanoBio research group 2 Smart Functional Materials research group

Saxion University of Applied Sciences, Enschede, The Netherlands

Contents

- Bacterial infections in health care (the problem)

- Goal of this project Synthesis of

nanomaterials

Application to textile

Testing antibacterial

property

Assessing toxicity

Abrasion by wear and washing

Implemen-tation in practice

- Conclusions and what’s next - Acknowledgements

The problem

- Bacterial infections are one of the most important challenges hospitals and other health care institutions are faced with.

- The chance of acquiring an infections with an hospital within the Netherlands is about 5.5 % (RIVM report 2014).

- Additional costs per year related with these bacterial infections is 136 M€ (in the Netherlands)

- Contamination occurs during transfer via personnel and is enhanced by bacteria growing in wounds of patients.

Medisch Spectrum Twente, Enschede

Goal of the project

Develop and apply a coating with nanomaterials on the textile that reduces the growth of bacteria.

Focus is on: - Doctor’s uniform - Separation curtains - Surgery jacket Doctor’s uniform

Washing cloth

Bed and cushion sheets

Separation curtains

Bacteria in textiles

Textiles Apparels, clothing

Home textiles (mattresses, floor coverings, show linings)

Outdoor textiles

Textiles provide an excellent environment, because of their:

- Large surface area

- Ability to retain moisture

- Additives which are a source of nutrition for bacteria (lubricants, antistatics, …)

(Natural textiles are more prone to be infected with bacteria than synthetic one)

Survey of compounds

EU regulations

Charge Water solubility

Application Antibacterial mechanism

Toxicity

Silver Biocidal product regulation

Cation 80% insoluble

Medicine, industry and home use

Cell are lysed Genotoxic, cytotoxic,

Titanium dioxide

Biocidal product regulation

Anion Not soluble

UV-protection in cremes and coatings

UV activated TiO2 forms radi-cals that oxidize organic materials

Carcinogenic when inhaled, toxic for aquatic life

Zink oxide Biocidal product regulation

Anion Not soluble in water

UV-protection and pigment (in plastics, ceramics)

Reacts with enzymes and forms radicals

Toxic for aquatic life, when inhaled damage to togans, allergan

Phosphotungstic acid hydrate

REACH Anion Soluble in water

Antibacterial, antitumoral, antiviral appls

Oxidizes organic materials

Irritant for eyes and lungs (when inhaled)

Silicotungstic acid

REACH Anion Soluble in water

Antibacterial, antitumoral, antiviral appls

Oxidizes organic materials

Irritant for eyes and lungs (when inhaled)

Triclosan Biocidal product regulation

Anion Not soluble in water

Desinfectant Biocide with multiple biological targets

Allergant, produces water dioxines. Toxic for aquatic life

Antibacterial nanoparticles coatings

Nano-silver Antibacterial properties

Refridgerators Sport socks Wound dressing

Antibacterial socks

Sport socks

1-5 out of 100 fibrils is darker (Ag coated)

Only the bottom part of the sock was found to contain Ag-containing fibers.

Ag is present as a continuous layer of thickness 100-200 nm (EDX)

From: Report “Nanoparticles in consumer products”, RIVM

BUT: Nanosilver is very difficult to firmly attach to

textiles and has been shown to be harmful for aquatic environment.

Survey of compounds

EU regulations

Charge Water solubility

Application Antibacterial mechanism

Toxicity

Silver Biocidal product regulation

Cation 80% insoluble

Medicine, industry and home use

Cell are lysed Genotoxic, cytotoxic,

Titanium dioxide

Biocidal product regulation

Anion Not soluble

UV-protection in cremes and coatings

UV activated TiO2 forms radi-cals that oxidize organic materials

Carcinogenic when inhaled, toxic for aquatic life

Zink oxide Biocidal product regulation

Anion Not soluble in water

UV-protection and pigment (in plastics, ceramics)

Reacts with enzymes and forms radicals

Toxic for aquatic life, when inhaled damage to togans, allergan

Phosphotungstic acid hydrate

REACH Anion Soluble in water

Antibacterial, antitumoral, antiviral appls

Oxidizes organic materials

Irritant for eyes and lungs (when inhaled)

Silicotungstic acid

REACH Anion Soluble in water

Antibacterial, antitumoral, antiviral appls

Oxidizes organic materials

Irritant for eyes and lungs (when inhaled)

Triclosan Biocidal product regulation

Anion Not soluble in water

Desinfectant Biocide with multiple biological targets

Allergant, produces water dioxines. Toxic for aquatic life

Polyoxometalates

- Polyoxometalates (POMs) are discrete anions of early transition oxides, such as molybdenum (Mo), tungsten (W) and vanadium (V) oxides.

- They can have a variety of structures

- In this project we use the following two polyoxotungstates:

Phosphotungstic acid

Si

Silicotungstic acid

SiW12O40 PW12O40

Polymeric oxoanions, that form a 3D network, around Si or P

Synthesis of silicotungstic acid

12 Na2WO4 2 H2O + Na2SiO3 + 26 HCl

H4SiW12O40 (x)H2O + (13-x)H2O + 26NaCl

Si

Silicotungstic acid

End product

(82% yield)

AFM characterization

Silicotungstic acid

Deposited on mica

Imaged in tapping mode

0.7 nm

Monolayer of POMs

SEM characterization

Crystallinity of the material is clearly visible

Applying the POMs to textile

For health care applications, mostly used textiles are:

- Cotton (100%)

- Polyester (100%)

- Blend cotton/polyester (35%/65%)

(standard test cloths are used to overcome fluctuations in textile quality)

CHALLENGE:

To apply the nanomaterial such that it is durable and can withstand washing cycles.

Vanderwaals interaction Ionic interaction

Textile needs be cationized (cotton is negatively charged, polyester is neutral)

Application methods

Foulard process:

allows thorough impregnation, no affinity with textile required

Extrusion process:

allows thorough impregnation, affinity with textile is required

Inkjet printing:

allows local application, no affinity required

Application methods

Foulard process:

allows thorough impregnation, no affinity with textile required

Extrusion process:

allows thorough impregnation, affinity with textile is required

Inkjet printing:

allows local application (one-sided), no affinity required

- Ink prepared from 1 and 2% nanomaterials was too viscous.

- Printheads got clogged - Applying

nanomaterials through spraying

Application methods

Foulard process:

allows thorough impregnation, no affinity with textile required

Extrusion process:

allows thorough impregnation, affinity with textile is required

Inkjet printing:

allows local application, no affinity required

- No control over concentration that is applied to the textile, dependent on affinity of the POM to the textile surface

Application methods

Foulard process:

allows thorough impregnation, no affinity with textile required

Extrusion process:

allows thorough impregnation, affinity with textile is required

Inkjet printing:

allows local application, no affinity required

- Accurate control over amount of nanomaterials applied. Fluid pick-up after impregnation is constant.

Quantifying amount of nano-material on textile (SEM/EDS)

EDS = energy-dispersive X-ray spectroscopy

Si

Si

W

Cotton treated with 2% Silicotungstic acid (padding with Foulard)

Quantifying antibacterial activity

(1-3 105 CFU/ml)

Method

(1-3 108 CFU/ml)

Definition antibacterial activity

t=0 and t=24h

C : control textile

T : treated textile

A < 2: not antibacterial

A = 2-3 significant inhibition

A > 3: strong inhibition

We aim for A > 3 (i.e. more then 1000 fold reduction in growth rate)

Textile is pressed against agar surface for a certain time using standard weight to transfer the bacteria 200 L

Is added to the textile diluted

Antibacterial activity

- Both cotton and blend show strong inhibition (A>3) with 1 and 2%.

- PET appears to show no difference

0

2

4

6

8

10

12

1% 2%

An

tib

acte

rial

act

ivit

y A

POM %

Cotton phospho

Blend phospho

PET phospho

Cotton tungsto

Blend tungsto

PET tungsto

against Klebsiella pneumonia

(Gram negative)

Antibacterial activity

0

2

4

6

8

10

12

1% 2%

An

tib

acte

rial

act

ivit

y A

POM %

Cotton phospho

Blend phospho

PET phospho

Cotton tungsto

Blend tungsto

PET tungsto

against Staphylococcus aureus (Gram positive)

- Both cotton and blend at 1% show not sufficient antibacterial effect.

- At 2% the blend and cotton with silicotungstic acid are sufficient.

Toxicity of nanomaterials

The nanomaterials are supposed to kill bacteria (bactericidal) or reduce the growth of bacteria (bacteriostatic).

But how do cells respond to the nanomaterials ???

Cytotoxicity to POMs in solution

Cytotoxicity to POM coated textile

Cytotoxicity of POMs in solution

Si

Morphology of MDA-MB-231 cells as a function of concentration of POM:

Cell shape changes and more aggregation is observed

Quantification of this is done with AlamarBlue test (LD50).

Cytotoxicity of POMs in solution

Si

Silicotungstic acid

Cytotoxicity of POMs in solution

Phosphotungstic acid

3T3 cells show very similar results

Cytotoxicity of treated textile

(is work in progress)

- Main challenge here is to find a good protocol (How do you press the textile onto the cell culture)

- Some results do not show a decrease in % of living cells as concentration increases and results turn out to be not so reproducible.

- Cell appear to stick to the textile, making it difficult to get reliable data.

- Transwell experiments in which the textile is below the membrane, does not result in any toxicity, but how representative is this experiment.

More work needs to be done here

And how representative are these cell lines for the skin ?

Effect on skin flora

Skin is your largest organ (surface is 1.8 m2, mass 10 kg) Skin flora = micro-organisms that live on the skin (transient and resident skin flora) Question is whether the antimicrobial activitity of the nanomaterial on S. epidermis and P. acnes is the same as for the pathogenic bacteria. P. Elsner, "Antimicriobials and the Skin Pysiological and Pathological Flora," Current Problems in Dermatology, vol. 33, pp. 35-41, 2006

Abrasion of nanomaterial

Abrasion of the nanomaterial is measured using a “crock”-device. The textile is worn against a test sample using standard conditions. (ISO 105X12) Then we use SEM/EDS to determine how much nanomaterial is transferred

Abrasion of nanomaterial

Example of 1% phosphotungstic acid on cotton in dry conditions

Not detectable

Abrasion of nanomaterial

W Dry conditions (% mass)

W Wet conditions (% mass)

Cotton 1% Phospho Non detectable Non detectable

Cotton 1% Silicic Non detectable Non detectable

Cotton 2% Phospho Non detectable Non detectable

Cotton 2% Silicic Non detectable 0,99

Blend 1% Phospho Non detectable 0,58

Blend 1% Silicic 0,09 1,55

Blend 1% Phospho Non detectable 1,48

Blend 1% Silicic Non detectable Non detectable

PET 1% Phospho 0,72 Non detectable

PET 1% Silicic Non detectable Non detectable

PET 1% Phospho Non detectable Non detectable

PET 1% Silicic 1,11 Non detectable

Amount of abrasion is low

Abrasion by washing

Textiles in healthcare are washed very often and therefore the abrasion by washing is investigated (95 C)

Most of the nanomaterial appears to be removed from the textile !

Conclusions

- POMs can be synthesized in large quantities.

- Using various methods we can apply these POMs to textile materials

- Strong antibacterial activity of silicotungstic acid (1% and 2%) on cotton and blend.

- LD50 values are 0.2 to 0.5% for POMs in solution.

- Abrasion by friction is minimal.

- Washing at 95 C removes most of the nanomaterials from the textile.

What still needs to be done

Next steps:

- Test abrasion by washing at other washing conditions.

- Repeat the toxicity studies on cells, but also apply this to a skin model system (is ongoing right now)

- Measure toxicity of the treated textiles directly (not that of free POMs)

- Rethink the strategy of attaching the POMs (but if they are immobilized, this might affect the antibacterial effect of the textile).

- Study the effect on the skin flora

- Consider other application fields (floor coverings).

More work needs to be done here

Nanostructured surfaces

Bio-inspired nanostructured surfaces Antibacterial properties

Dragonfly

Ivanova et al., Nature Communications 4: 2838 (2013)

SEM image of forewing (scale bar = 200 nm)

Can we create a similar structure onto textile fibers ?

Acknowledgements

Nicole Zeijen Rick Hobert Ger Brinks Henk Gooijer Paul Borm Johan Molling Hasan Mashhadani Michelle Lukas Robin Verwijs Erwin Nijhuis

RAAK-mkb grant

Thank you

Martin Bennink

Lector NanoBio Saxion University of Applied Sciences Enschede, NL

m.l.bennink@saxion.nl

Other activities in NanoBio …

Textiles in health care (SIA, RAAK-MKB)

Antibacterial nanostructured surfaces

(TFF) “Nano meets forensics” (TFF)

Heart-on-a-Chip (SIA, RAAK-MKB)

in preparation

Labelfree sensing of small proteins (insulin)

(TFF)