Development of plasma enhanced antiviral surgical gown for healthcare workers

Surgical gown should be made out of liquid proof fabric to protect the blood-borne infectious microbes from penetrating through the fabric. Risks of patients are contamination from both endogenous and exogenous microorganisms and risk of healthcare workers are contamination from various blood-borne pathogens due to occupational exposure to patient blood and body fluids (Unsal et al. 2005). Surgical gowns should provide an effective protective barrier against the transfer of microorganisms, particulates and fluids, in addition to acting as an aseptic barrier for the patient’s protection, in order to minimize strike-through and the potential for personnel contamination (Rutala and Weber 2001). Due to the prevalence of HIV and hepatitis B and C viruses in the patient population, the barrier efficacy of protective surgical gowns have gained importance. During surgery, in an operating room, a patient’s blood can penetrate surgical gown material and possibly contaminate the surgeon’s skin, if not well protected. Several blood borne pathogens have the potential to spread in this manner, the most important being the HIV and the hepatitis B virus, which are related to AIDS and hepatitis (Loveday et al. 2007).

Surgical gown materials should have antimicrobial properties and blood repellency properties in order to protect patients from contamination by surgical staff during operations and also to protect the surgical team from infectious blood and other body fluids (Mews 2009). Commercial available polyester, polyester-cotton and cotton plain woven fabrics were treated with fluropolymer and found that polyester and cotton twill fabrics have high protection (Midha et al. 2014). To apply both antimicrobial and flurochemical repellent finishes to nonwoven surgical gown fabrics, a one-bath process was investigated by Huang and Karen (2007). Etching of fabrics with functional groups from a gas based plasma treatment can impart functionality, such as grafting polar surface groups to impart hydrophilicity on a hydrophobic fibre surface. There have even been studies conducted on greige fabric treated with plasma and research was made to allow greige fabric to be dyed without the requirement of fabric preparation such as desizing, scouring, and bleaching. The research found that exposing a greige fabric to plasma altered the surface so that it became hydrophilic. Through the formation of polar groups on the fabric surface, during plasma treatment, the increas hydrophilicity was studied for use in pretreating textiles (Gawish et al. 2008; Rajpreet et al. 2004).

This research work aims to develop plasma enhanced fluorocarbon treated surgical gown to protect the healthcare workers from pathogens spreading from patients as well as reverse contamination. Liquid barrier properties of surgical performance were analyzed by viral penetration, antibacterial, spray impact penetration, hydrostatic resistance, tensile properties and moisture vapour permeability.

Spun bond polypropylene and polyester nonwoven fabrics were obtained from Mogul nonwoven industry, Turkey. The diameter of the individual polypropylene filament was approximately 0.2 microns and diameter of the individual polyester filament was 0.8 microns. The basis weights of the both nonwoven fabrics were 25 grams per square meter. The prime components of this research are polypropylene and polyester nonwoven fabrics. As polypropylene fibre has stereo-regular isotactic molecular structure, due to its high degree of crystallinity, good handling, strength and a high enough melting point for normal use, it is being used in many industrial applications, as well as in healthcare protective clothing. It has non polar and hydrophobic nature which is a good liquid repellent property. Considering its liquid barrier protection PP nonwoven is used as an outer layer in the developed surgical gown. Polyester nonwoven fabric is used as an inner layer in the developed surgical gown because of its wickability characteristics. The wickability nature of polyester nonwoven transfer the moisture from inner to outer layer through capillary action which makes the wearer comfort.

Figure 1 shows the plasma experiments conducted on the samples. Prototype downstream Atmospheric Pressure Plasma Reactor is equipped with a controlled stage and a solid state power generator. The stage was cooled using a chiller. The monomer was pumped into a lab designed heated evaporator through an equipped tube. The fluorocarbon gas used to provide hydrophobicity was C₃F₆. The radio frequency required to build the electromagnetic field was 600 watts. The electrode applicator height was 3 mm. The flow rate monomer was maintained as 0.6 ml/min and the exposure time was 10 seconds.

Fabric was cut into 15 cm square samples. The samples were ironed to reduce wrinkling and to give an even surface height for treatment. Samples were then mounted on the stage using double sided sticky tape. Sample surface was made as smooth as possible, and loose yarns were removed or taped down. Once stable plasma was generated, stage was turned on to move sample into the plasma field for the desired exposure time for the pre-deposition surface activation treatment. After the sample passed out of the plasma field, it passed beneath the applicator, which deposited the monomer to condense and graft activated species on the fabric surface. Monomer flow was then turned off. Stage direction was reversed, and the sample passed through the plasma field for second time to induce free radical polymerization of the monomer on the fabric surface. Fabric sample was then removed from the stage and the treatment was done on both the sides.

A schematic of the flurocarbon plasma reaction mechanism is shown in Figure 2, in which I⁺ refers to an ion, I* refers to a hot neutrals, the dashed lines represent energy transfer through the polymer and the curved lines represent species diffusion through the polymer. Through the deposition of a flurocarbon as an overlayer, etching of surface proceeds. C_xF_y radicals are the precursors to polymerize deposition followed by ion activation of surface sites. The polymer layer is formed by energetic ion sputtering and F atom etching. The polymer layer is the main inhibitor for the transport of species and delivery of activation energy to the surface. The oxygen reacts with the flurocarbon species to release etch product such as COFx. Finally by this reaction lower surface energy to the polypropylene nonwoven surface was imparted.

For the application of synthesized Titanium nano dispersion, the most widely used method of application pad-dry-cure process was used. The plasma treated polypropylene nonwoven fabric was coated with 1% nano dispersion with material to liquor ratio of 1:20 and 0.5% anionic binder. The fabric samples were immersed in the bath followed by padding through squeezed rollers at a pressure of 147 N/cm² to remove the excess liquid. Each fabric sample was padded with the solution twice to ensure even distribution of solution. After padding, the fabric was dried naturally and then cured at 150°C for 2 min. The wet pick up was 89%. The add-on of the titanium nanoparticles was 87%. Pore size of the plasma enhanced nano finished outer nonwoven fabric was characterized using tri-nocular microscope.

The plasma enhanced fluorocarbon treated fabric samples were characterized using scanning electron microscope. Tri-laminate gown with plasma enhanced flurocarbon treated nano finished polypropylene as an outer layer, PTFE film as a middle layer and polyester nonwoven fabric as an inner layer were bonded together using a fusing machine at a temperature of 165°C with pressure of 98 N/cm². The developed plasma treated surgical gown was tested and analyzed for the following properties such as Viral penetration analysis, antibacterial, tensile, Spray impact penetration, hydrostatic resistance and moisture vapour permeability.

Risks of healthcare workers are contamination from various blood-borne pathogens due to occupational exposure to patients’ blood and body fluids. So the antibacterial testing was performed for the developed surgical gown. Light activate antibacterial mechanism which involves interaction with and transferring energy to oxygen so as to provide a source of an active or excited oxygen species known as singlet oxygen. Singlet oxygen is an activated form of the usual triplet state molecular oxygen. Upon exposure to normal light, the dyes used in the present invention generate singlet oxygen that kills microorganisms. Bacteria require less light though they are more sensitive to the singlet oxygen generated by the light activated dye. Surgical room illumination of about 2000 foot candles is more than sufficient. Test swatches of this plasma treated nonwoven were tested for microbiological kill by inoculating the swatches.

The antimicrobial substrate so made comprises of a light activatable singlet oxygen generating substance to inhibit the growth of bacteria selected from the group consisting of Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Mycobacterium bovis, methicillin resistant Staphylococcus aureus and Proteus vulgaris. The bacterial concentration was 0.5%.

Swatches with a 0.5% concentration of bacteria were exposed to light of 2000 foot candles or dark for a given period of time. After exposure for the required time, the number of live bacteria remaining on the test swatches was determined. The log of the remaining live bacteria versus the exposure time to light of 2000 foot candles and dark were determined. After a suitable incubation, bacterial colonies were counted, percent kill calculated. Recovery procedure started with transfer of samples into a sterilized capped tube containing about a dozen 3 mm glass beads and 5 ml of sterile phosphate buffered saline. After sealing the cap, the tube was shaken vigorously for one minute and then placed for 30 seconds in a low intensity ultrasonic cleaning bath. One ml of the recovery fluid was also placed directly in a 100 mm Petri plate. For one to two days the plates were incubated at 30°C., until countable. The zero time counts recovered from the swatches were compared with the inoculum count. To obtain and average log zero time reading, all of the zero time contents were combined by averaging their base 10 logarithms. Log reduction was calculated as the difference between the samples and average zero time logarithms. Percent kill was calculated as 100(1- Log₁₀).

Viral penetration testing of surgical gown using ASTM F 1671 was carried out to investigate the antiviral property. ASTM F1671 is the test method used to measure the resistance of materials used in protective clothing for penetration by blood borne pathogens, using bacteriophage under the condition of continuous liquid contact. The test system has been designed for measuring penetration of surrogate microbe for hepatitis B virus (HBV), hepatitis C virus (HCV) and HIV. The protective clothing materials to be tested are intended to provide protection against blood, body fluids and other potentially infectious materials. The surface tension range for blood and body fluids is approximately 42 – 60 dynes/cm. In order to simulate the wetting characteristics of blood and body fluids, the surface tension of the ΦX174 bacteriophage suspension is adjusted to approximate lower end of this surface tension range (42 dynes/cm).

The ΦX174 bacteriophage was selected as the most appropriate surrogate for the blood borne pathogens mentioned because it satisfies all of these criterias. The ΦX174 bacteriophage is a non-enveloped 25 – 27 nm virus (similarly to HCV, the smallest pathogen) with an icosahedral or nearly spherical morphology and excellent environmental stability. It is non-infectious to humans, has a limit of detection which approaches a single virus particle, grows rapidly, and can be cultivated to reach high titers similar to HBV (the most concentrated pathogen mentioned). Test samples are prepared by randomly cutting the protective clothing material into approximately 75×75 mm swatches. Test samples are exposed to approximately 60 ml of the ΦX174 bacteriophage suspension. At the conclusion of the test, the observed side of the test sample is rinsed with a sterile assay medium and then analyzed for the presence of the ΦX174 bacteriophage. Surgical protective clothing ‘pass/fail’ determinations are based on detection of penetration.

Plasma enhanced fluorocarbon treated single, dual and tri-laminate surgical gowns have been used to study their suitability for antiviral surgical gowns. Pore size of plasma treated polypropylene nonwoven is smaller than untreated polypropylene, thereby influencing antibacterial resistance. Both the tri-laminate and dual layer plasma treated PTFE gowns passed in viral penetration analysis whereas plasma treated single layer surgical gown and dual laminated plasma polypropylene with polyester failed in viral penetration analysis due to absence of PTFE film. Impact penetration of Plasma treated single and dual layer gown offers level 1 protection and plasma tri-laminate gown has level 2 protection. Hydrostatic resistance of plasma treated tri-laminate gown offers level 2 protection. Tri-laminate plasma gown has better impact and hydrostatic resistance as compared single and dual laminate gowns. MVTR of plasma treated tri-laminate gown decreased by 21% in comparison with untreated nonwoven gown. The developed plasma enhanced fluorocarbon treated surgical confirms level 4 protection according to AAMI barrier classifications.