Tuesday, December 21, 2021

Iris Publishers-Open access Journal of Otolaryngology and Rhinology | ‘POLIDON’ Approach-A Novel Approach of Mastoidectomy in the COVID-19 Pandemic

 


authored by Mostafa Kamal Arefin*

Abstract

Background: WHO declared COVID-19 outbreak as pandemic in March, 2020, which was started from Wuhan of china. Mastoidectomy is an aerosol generating procedure. If a patient of COVID-19, either confirmed, suspected or asymptomatic career, requires mastoidectomy urgently, it’s a critical issue for the health care professionals for the highly contagious nature of this novel corona virus. Here, some simple, but novel and very effective measures will be discussed for protection of all health care providers (HCPs). Polythene sheet and Povidone Iodine are the change makers in this novel approach of mastoidectomy, mentioned in this article. So, we named the technique as ‘POLIDON approach’ of mastoidectomy.

Material and method: Placement of a transparent, sterile polythene sheet which acts as an interface between patient and surgeons and all other OR staffs is an important issue. Meanwhile, extended use of Povidone Iodine (PVP-I) is recommended in different way. Mouthwash for gargling and nasal application either by spray or nasal irrigation or drop will reduce viral load from nose and mouth of patient. HCPs should use PVP-I prophylactically also. Thus, the chance of transmissibility of novel coronavirus is reduced. Meanwhile, Povidone Iodine should be mixed with irrigating fluid to help in reduction of contamination by bone dust mixed with fluid, produced during surgery.

Conclusion: As mastoidectomy is an aerosol generating procedure, and novel coronavirus is highly contagious, so higher level of protection is required. A simple and cheap polythene sheet as barrier drape as well as rational and novel use of Povidone Iodine, i.e. the proposed ‘POLIDON’ approach can significantly reduce the chance of corona virus transmission among the health care professionals working in the operation theatre.

Keywords: POLIDON; Mastoidectomy; COVID-19; Povidone Iodine; Polythene

Abbreviations: PVP-I: Povidone Iodine; HCP: Health care provider

Background

WHO declared COVID-19 outbreak as pandemic in March 2020, which was started from Wuhan of China. During this pandemic, (every person or patient has chance of being infected with corona virus,) nobody is immune of being infected with coronavirus or being asymptomatic career of this [1]. Mastoidectomy is an important surgical procedure in which all the accessible mastoid air cells are accenterated with an aim to make the ear safe [2-4]. CSOM with extracranial and intracranial complications are indications of emergency or urgent mastoidectomy. The indications of urgent or emergency mastoidectomy are a bit changed recently [5,6]. In the last few decades brain abscess due to CSOM was advocated and practised to be treated in two stage, at first incision and drainage of brain abscess, then 2-4 weeks later mastoid exploration. But recently single stage urgent otological procedure is advocated (and it is without any delay) for minimizing mortality and morbidity. In a developing country- like Bangladesh, lot of patients present to the hospitals at advanced stage usually with complications, like mastoiditis (not responsive to conservative treatment), facial palsy, labyrinthitis, extradural abscess, brain abscess, meningitis, lateral sinus thrombosis, otitic hydrocephalus which warrants urgent surgery [5-7]. In our context, emergency mastoidectomy is not uncommon, especially in our centre, i.e. Dhaka Medical College Hospital, a tertiary level hospital [8].

Mastoidectomy is an aerosol generating procedure. If a patient of COVID-19, either confirmed, suspected or asymptomatic career, requires mastoidectomy for any of those indications, it’s a critical and alarming issue for the health care professionals, including doctor, nurse, other OR (operating room) staff for the highly contagious nature of this virus [9]. In current situation prior to any (routine) surgery report of RT-PCR test for coronavirus is mandatory. Negative results do not preclude SARS-CoV-2 infection and should not be used as the sole basis for patient management decisions. Negative results must be combined with clinical observations, patient history, and epidemiological information [10]. In a developing country- like Bangladesh, patient presents to the hospitals at advanced stage usually with complications, like mastoiditis, facial palsy, labyrinthitis, extradural abscess, brain abscess, meningitis, lateral sinus thrombosis, otitic hydrocephalus [8,11].

RT-PCR test for detection of coronavirus is not available throughout the country, due to lack of laboratory facility, kit, technologist and other support. Due to partial or complete lockdown state mobility for the patient is also not easy rather very difficult. So, confirmation of COVID-19 by RT-PCR test can’t be done instantly everywhere. Prior to surgery it’s recommended to do a CT scan of chest to find clue regarding COVID-19 [12]. But sometimes situation is unfavourable for doing it also. Few days or even hours are demarcating line between life and death or overall morbidity. For this reason health care professionals should take maximum protections for their own safety within lots of limitation, seeming every patient as a COVID-19 patient. Though the government, local authorities, personally all HCPs are trying to provide or collect adequate personal protective equipment (PPE) or other measures, throughout the world there is deficiency of it. In a resource constraint country, like us, we need to have cheap, affordable, easily available measures for protection. Here, some simple, but novel and very effective measures will be discussed for protection of all health care providers (HCPs) in this aerosol generating procedure. Polythene and Povidone Iodine are the change makers in this novel technique of mastoidectomy, mentioned in this article. So, we named the technique as ‘POLIDON technique’ of mastoidectomy.

Material and Method

In our setting, placement of a transparent, sterile polythene sheet which acts as an interface between patient and surgeons and all other OR staffs is the most important issue. Meanwhile, extended use of Povidone Iodine (PVP-I) is recommended in different way. Mouthwash for gargling and nasal application either by spray or nasal irrigation or drop will reduce viral load from nose and mouth of patient. HCPs should use PVP-I prophylactically also. Thus the chance of transmissibility of novel coronavirus is reduced [13-15]. Meanwhile, Povidone Iodine should be mixed with irrigating fluid to help in reduction of contamination by bone dust mixed with fluid, produced during surgery. This technique was innovated by the corresponding author and applied in Dhaka Medical College Hospital and Taqwa General Hospital (, a private hospital) in three emergency/ urgent mastoid surgeries.

Povidone Iodine

In 1955 Povidone-iodine (iodine with water-soluble polymer polyvinylpyrrolidone, PVP-I) was invented. The active moiety, non PVP‐bound (free) iodine is released into solution from the PVP‐I complex. PVP delivers the free iodine to target cell membranes. Free iodine, that mediates the basic mechanism of action (oxidation of amino acids and nucleic acids in biological structures), which is difficult to counteract. This basic mechanism of action leads to strong microbicidal activity expressed by multiple modes of action that include the disruption of microbial metabolic pathways, as well as destabilisation of the structural components of cell membranes, causing irreversible damage to the pathogen. Consumed free iodine is then replaced by PVP‐bound iodine. The concentration of free iodine is the determining factor of the microbicidal action of PVP‐I. In a study investigating the virucidal activity of different disinfectants, Electron micrographic study revealed that, exposure of iodine led to destruction of nucleoproteins of viral particle-which is the main mechanism of action [16, 17]. However, disruption of surface proteins essential for the spread of enveloped viruses has also been noted [16, 18]. Furthermore, Iodine is a scavanger of free radical oxygen species, contributing to anti-inflammatory properties [16, 19]. This interaction ultimately results in microbial death [16-26].

Virucidal activity of PVP-I

Povidone‐iodine has been reported as having the highest virucidal activity profile among several antiseptics such as Chlorhexidine (CHG), Benzalkonium chloride (BAC), BEC and Alkyldiaminoethyl‐glycine hydrochloride (AEG) [16, 20]. PVP-I has been shown to be active in vitro against the coronaviruses that have caused epidemics in the last two decades, namely SARS-CoV causing the severe acute respiratory syndrome (SARS) epidemic of 2002-3 and MERS-CoV the agent responsible for causing the Middle East respiratory syndrome (MERS) epidemic of 2012-13. SARS-CoV-2 is highly homologous with SARS-CoV, and as such it is considered a close relative of SARS-CoV1015. In his study Egger et al suggests that, upto 0.23% concentration of PVP-I is virucidal [17, 18]. Kariwa showed that treatment in vitro of SARS-CoV with various preparations of PVP-I for 2 minutes was enough to reduce viral activity to undetectable levels [14]. The lowest concentration used was 0·23%, found in an over the counter throat spray [18]. Recent studies conclude that SARS-CoV-2 should behave similarly 21[16-26].

Plastic/Polythene

Modern healthcare would not be possible without the use of plastic materials. Polythene is one type of it, which is popular for its greater flexibility, comfort and mobility. Polythene, with its exceptional barrier properties, light weight, low cost, durability, biocompatibility and transparency, is ideal for medical applications.

Today’s most innovative medical procedures are dependent on plastics

We designed a technique to use it like ototent (please see Figure) [27].

Proposed Steps of Mastoidectomy in COVID-19 pandemic:

1. Consent- written informed consent is mandatory.

2. Preparation of patient

a) Prior to surgery, patient is to gargle with 10-15 ml PVP-I 1% (undiluted) or 30 ml 0.5% (diluted with same amount of water) mouthwash solution

b) Nasal irrigation with PVP-I (0.5%) is to be given, in case of difficulty or inconvenience of patient PVP-I nasal spray or drop should be applied.

3. Preparation of members of surgical team

a) Sterile surgical gown should be put over impermeable gown or protective apron.

b) FFP3 or FFP2 or N95 mask or PAPR on face

c) Eye protective goggles

d) Hood cap is preferable than simple cap forehead protection.

e) Double gloves is preferable.

f) All health care professionals are proposed to use PVP-I for gargling and applying in nose in same manner as proposed for patient for protection as adjunct to PPE before and/ or after mastoidectomy.

g) During induction of anaesthesia and intubation full surgical team, except anaesthetist and one or two staff, necessary for this step, is to stay outside the OT. 5minutes later full team is to enter into the OT.

4. Positioning of the patient.

5. Skin should be prepared with PVP-I 10% solution.

6. PVP-I is to be mixed with irrigating fluid in atleast 1:10, i.e. 100 ml in 1litre of normal saline.

7. Draping is to be done properly.

8. Infiltration of local anaesthesia with Lignocaine with adrenaline.

9. A postauricular incision (usually) is to be made.

10. Skin, subcutaneous tissues are to be dissected.

11. Temporalis fascia is to be harvested.

12. Posteriorly or superiorly based flaps are to be made.

13. Another incision in external auditory canal 1 to 4 o’clock (traditionally 6 to 12 O’clock) position is to be made.

14. Mastoid retractors are to be fixed in position so that whole tympanic membrane (TM) could be visualized.

15. Margin of perforation is to be freshened.

16. Tympanomeatal flap is to be elevated.

17. Prior to start of drilling one or two additional, transparent, sterile polyethene sheet is to place and fix over the operative field, like an extra drapping sheet and a tent, where the apex is formed at microscope objective eye piece. This step can be performed prior to incision also.

Hands of surgeons and all necessary instruments kept inside the polythene sheet, the tent. Surgeons hands are to be fixed with the polythene sheet with adhesive tape.

Some ports in polythene sheet like microscope drape, for entry of surgeon and assistant’s hand can be made.

18. Mastoid drilling is to be started targeting the triangle of attack.

19. Drilling is to be continued for complete disease removal and completion of surgery

20. Cartilage or TORP or PORP is to be used for ossiculoplasty or other type of reconstruction.

21. Temporalis fascia is to be placed properly.

22. Wound is to be closed in layers after proper haemostasis.

23. Ototent made by polythene is to be removed.

24. Mastoid bandage is to be applied.

25. Anesthesiologist is to start the reversal process.

During extubation full surgical team, like before, is to stay outside OT again. Five minutes after extubation they should enter inside OT.

26. Proper doffing is to be done after the operative session [2- 4].

Preparation of Application of Povidone Iodine or PVP-I Prior to Surgery

For gargling and mouthwash

For fully conscious patient

a) PVP-I 1% solution (undiluted) 10 ml for 30 sec to 1 minute or 0.5% solution (diluted by mixing same amount of water, i.e. 10 ml PVP-I with 10ml water) 20ml for 1-2 minutes.

b) For patient with altered consciousness - A sponge swab or similar is soaked in 2-5 ml of 1% PV P-I and this is carefully wiped around all oral mucosal surface.

For nasal application

Nasal spray: 2-3 puff in each nostril with a standard atomizing devise with 0.5% solution of PVP-I or

Nasal irrigation: Irrigate or wash through both nostril with 200-300 ml (100-150 ml in each nostril) of 0.5% PVP-I solution or

Nasal drop: If nasal spray or irrigation facility is not available apply nasal drop 3-4 drops in each nostril [13, 14, 28].

Preparation of PVP-I mixed irrigating fluid

ml of PVP-I 10% solution is to be mixed with 900ml of Normal saline to make a PVP-I 1% solution. 50 ml of PVP-I 10% solution can be mixed with 950 ml of Normal saline also.

Polythene: Simple, transparent polythene.

The plastic/polythene sheet allows good mobility of the hands of the surgeons. In spite of being transparent or translucent, there may have some degree of glare. Several modifications can be done. Our focus is on the simplest method. Any positive modification is appreciable. We designed a technique to use it like ototent (please see Figure) [27]. Microscope drape is an alternative, relatively expensive, but not available everywhere, especially in developing or any resource constraint country [9, 22].

Special considerations

1) Number of health care professionals in the OT should be minimum. In an ear surgical procedure, only one or two surgeons is/are needed to be in the OR and all observers should be excluded. This is important to reduce potential exposures, but also to limit use of PPE (mainly N95 masks).

2) Experienced and skilled surgical team is must.

3) If facility and time allows mastoidectomy should be done under general anaesthesia in a negative pressure room.

4) Electrocauterization by monopolar diathermy should be avoided, otherwise minimized.

5) For educators, making a video recording of the surgery is to be suggested to share with trainees, if possible, rather trained them under direct guidance [24] (Figures 1-5).

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Monday, December 20, 2021

Iris Publishers-Open access Journal of Complementary & Alternative Medicine | Herbal Pharmacy

 


authored by M’Lou Barnett*

Opinion

With 50% of Americans utilizing Complementary Alternative Medicines, knowledge of herbal supplements is limited among the general population. Unfortunately, most Americans rely on the advice of health food store employees to select botanical supplements.

The top Herbal supplements will be presented to educate nurses. These include Aloe Vera, Ashwagandha, Black Cohosh, Butterbur, California Poppy, Capsicum, Chamomile, Cinnamon, Dandelion, Echinacea, Elderberry, Evening Primrose, Fennel, Feverfew, Garlic, Ginger, Ginkgo, Ginseng, Goldenseal, Green Tea, Hibiscus, Horse Chestnut, Kava, Lemon Balm, Licorice, Milk Thistle, Peppermint, Red Yeast Rice, St. John’s Wort, Saw Palmetto, Skullcap, Soy, Tea Tree Oil, Turmeric, Uva Ursi & Valerian.

Each herb topics will include: Common Latin Binomial Name, Part Used, Active Ingredient, Primary Uses, Preparation & Dose, Pregnancy & Lactation, Contraindications, Adverse Effects, Duration, Toxicity & Drug Interactions.

European countries far exceed the United States in standardizing, determining indications for usage & have developed formularies for herbal supplements. The German Commission E approves botanical supplements for primary uses. Even the textbooks about herbal medicine have been translated from German to English.

Since many Americans are turning to Complementary Alternative Medicines, nurses need to have the knowledge base to advise patients. United States physicians are not schooled in herbal medicine and are unable to advise patients. Most physicians advise patients to not take herbal supplements because they are only schooled in medicine (pharmacotherapy) and surgery. There are more natural modalities that can benefit patients.

Nurses have traditionally been open to new modalities to assist patient on health promotion & health maintenance. Medication & Surgery does not cure or benefit all illnesses, as nurses astutely know. Nurses & health professionals will have a better knowledge of Herbal Pharmacy to better inform their patients.

GAIA Herbs are the Best Brands of Herbal Medicine

Aloe Vera-RX: Gel soothes pain & Promotes healing of wounds.

Ashwagandha-RX: Calming adaptogen for anxiety, Stress, insomnia & Improving Cognitive function.

Black Cohosh-RX: Menopausal Symptoms (hot flashes, night sweats, sleep disturbances, irritability); Premenstrual Syndrome & Dysmenorrhea.

Butterbur-RX: Allergies & migraine prophylaxis.

California Poppy-RX: Insomnia, Sedation, Aches, Nervous Agitation, Prolong sleep & Anxiolytic.

Capsicum-RX: Topically for pain of Shingles, OA, RA, Post- Herpetic Neuralgia, Trigeminal Neuralgia, Diabetic Neuropathy & Back pain.

Chamomile-RX: Calmative, Carminative, GI Antispasmotic & Anti Inflammatory.

Cinnamon-RX: Type 2 Diabetics, Flatulence, GI Spasms, Prevent N/V. Diarrhea Infections. Add Cinnamon to small container of Applesauce to prevent Diarrhea.

Dandelion-RX: Diuretic, Laxative, Flatulence, Gallstones, Bile Stimulation, Circulatory tonic.

Echinacea-RX: Supportive therapy for colds & infections of respiratory & lower urinary tracts. Take at beginning of cold symptoms for 4 weeks, 8 weeks maximum.

Elderberry-RX: Treatment for influenza, stimulates immune function. Great for upper respiratory symptoms.

Evening primrose-RX: PMS, RA, mastalgia, atopic eczema, diabetic neuropathy & Osteoporosis.

Fennel-RX: Diuretic, respiratory infections, flatulence, bloating & colic for infants.

Feverfew-RX: Migraine prophylaxis. Butterbur is better.

Garlic-RX: Lipid lowering, reduces cholesterol 5-12%.

Ginger-RX: Motion sickness, chemo induced N/V & hyperemesis gravidarum.

Ginkgo-RX: Mild to moderate dementia, intermittent claudication, vertigo, tinnitus & migraine prophylaxis.

Ginseng-RX: Stimulation adaptogen. SE: Hypertension, Nervousness.

Goldenseal-RX: Treatment for infectious diarrhea; Giardia, entamoeba histolytica, trichomonas vaginialis, cholera & E. Coli.

Green tea-RX: Improves cognitive performance; mental alertness, vomiting, diarrhoea, H/A, hyperlipidaemia, type 2 diabetes & parkinson’s disease.

Hibiscus-RX: HTN, diuretic, effective as captopril & lisinopril, hypercholesterolemia, increased HDL & laxative.

Horse chestnut-RX: Chronic venous insufficiency, varicose veins, haemorrhoids & phlebitis.

Kava-RX: Anxiety, stress, ADHD, insomnia & restlessness.

Lemon balm-RX: Anxiety, insomnia, restlessness, dyspepsia, bloating flatulence, colic & dementia.

Licorice-RX: Upper respiratory tract, gastric/duodenal ulcers, GERD, IBD & topically for herpetic lesions (will heal lesions in one day with repeated applications).

Milk thistle-Hepatoprotectant: Treats cirrhosis, chronic hepatitis & liver cancer.

Peppermint-RX: IBS-Diarrhea dominant, cramps of GI tract, myalgias, neuralgias & common cold.

Red yeast rice-RX: hyperlipidmia, indigestion & diarrhea.

St. john’s wort-RX: Mild to moderate depression, anxiety & nervous unrest.

Saw palmetto-RX: Benign prostatic hyperplasia.

Skullcap-RX: Insomnia & anxiety.

Soy-RX: Hyperlipidemia, menopausal symptoms, prevents osteoporosis & breast cancer.

Tea tree oil-RX: Topically only-RX: Onychomycosis, Tinea pedis, antiseptic for cuts & abrasions.

Turmeric-RX: Most potent anti-inflammatory in food. Dyspepsia, OA, RA, H/A, bronchitis, URI & fibromyalgia.

Uva Ursi-RX: UTIs, cystitis, urethritis, diuresis, dysuria, pyelonephritis, BPH & bronchitis.

Valerian-RX: restlessness, mild sleep promoting agent, nervous or anxiety induced sleep disturbances.

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Friday, December 17, 2021

Iris Publishers-Open access Journal of Biomedical Engineering & Biotechnology | Low-Pressure Plasma Treated Polyetheretherketone for Biomedical Application- A Comparative Study on Surface Chemistry and Storage Stability

 


authored by  Svea Petersen1*

Abstract

The surface chemistry of different plasma-treated PEEK was characterized by contact angle measurements and X-ray photoelectron spectroscopy and the results of the different methods were compared. In addition, the physicochemical changes on the surface were documented and evaluated within the course of the aging/recovery of the surface within one week. All plasma treatments had serious effects on the aromatic basic structure of the polymer, but at the same time increase the nitrogen and oxygen content of the surface up to a maximum of 28.2 % by means of oxygen plasma. Regardless of the process gas, the surface energy increases to >63 mN/m what results in a clearly hydrophilic surface. Overall, three phases of hydrophobic recovery were observed, in two of which the degradation of functional groups was shown by a decreasing surface energy. The changes in the acid properties could be quantified by Berger’s method. The treatment in the oxygen plasma leads to an acidic surface with a Dshort value of 1.6. In nitrogen plasma, on the other hand, a slightly alkaline surface is generated with a shortened Berger parameter of -0.3. Regardless of the process gas and the initial nature of the surface, a slightly more acidic surface is formed during storage compared to the reference. The elemental composition of the plasma-treated PEEK appears to be relatively constant over the storage time, but with significant changes in the binding states. The double bonds induced during the plasma treatment are degraded and with them also the induced carboxylic acid.

Introduction

Its excellent temperature and chemical resistance, its outstanding mechanical properties and its thermoplastic processability characterize the semi-crystalline, aromatic highperformance polymer polyetheretherketone (PEEK). Because of this property profile, it has tremendous potential in many areas of the high technology industry. The fields of application range from load-bearing components to abrasion and corrosion protection coatings, ball bearings, high-pressure and vacuum components to implant applications in biomedical engineering [1-4]. Particularly in the latter field, this type of polymer offers numerous possibilities to substitute metallic materials. This is especially interesting because PEEK offers some additional benefits, such as X-ray transparency and bone-like strength, preventing stress shielding effects. In addition, the tensile strength of the resulting composite material can be adjusted within a range of 3.6 to 18 GPa by the implementation of glass or carbon fiber and thus adapted to the application [5,6]. Unfortunately, the chemical resistance results in a general inertness of the surface and a hydrophobic character of PEEK. This can be challenging not only for the joining of PEEK components by gluing or the coating on other materials, but also for the acceptance of possible PEEK implants in biological systems. However, modification of the surface would significantly improve the applicability of this promising high-performance polymer in biomedical fields as dentistry or implantology. In particular, plasma technology could play a primary role as it combines advantages such as cleaning, nanostructuring, the establishment of functional groups, depending on the process gas used, and an enormous improvement of the wetting behavior in one process step [7,8]. These three factors alone have a serious impact on the bondability as well as the biocompatibility of materials [9,10]. Due to its free availability, a frequently used process gas represents air, but pure nitrogen, oxygen, hydrogen and many more are also used for the process [11]. Especially low-pressure plasma technology offers great potential due to the easily controllable process parameters and the resulting reproducibility. Thus, Pawson et al. and Ha et al.demonstrated the formation of carboxylic acid groups on the PEEK surface by treatment in oxygen plasma using XPS and To F-SIM [12,13]. Due to its reactivity towards biomolecules present in the human body, this functional group can be used for the mediation of the biomaterials surface-biological system interaction. For the same reasons, amino groups are relevant whose formation on the PEEK surface is achieved by a nitrogen plasma treatment, as reported by Terpilowski et al. [14]. As a mixture of oxygen and nitrogen with varying composition, air is a more complex process gas in which the processes occurring in the plasma state are difficult to predict. Meanwhile, due to its free availability and associated cost savings, it is frequently used in industrial applications. However, regardless of the process gas, plasma modifications are not stable because implemented groups often show a volatile character. In addition, the rearrangement of the macromolecules leads to a recovery of the surface and thus additional time-related changes in the surface chemistry [7,15]. Taking this into account, Rymuszka et al. carried out studies on the long-term stability of air plasma modifications to PEEK, which showed that the number of functional groups is reduced during storage due to atmospheric contact, which also has a particularly negative influence on the wettability of the surface [16]. Since there is currently insufficient data for the long-term stability of other plasma-modified surfaces, an essential goal of this work is the characterization of the surface chemistry of PEEK over the storage time. Furthermore, the recovery of the surface should be described by means of contact angle measurements. From the determined contact angles, the surface chemistry of the PEEK surfaces will be characterized by using different evaluation methods and compared with XPS data.

Experimental

Materials

The PEEK sample material was obtained by Evonik Industries AG (Essen, Germany) in the form of a 100 μm thin, translucent foil which is marketed as VESTAKEEP 4000G. For the contact angle measurements, samples in the size of 5x10 cm were cut out of the foil. After being washed with distilled water, it was cleaned with isopropanol in an ultrasonic bath for 3 minutes. The drying was carried out by evaporation of the isopropanol at room temperature for at least 15 minutes. As sample for the XPS-measurements discs of 12 mm in diameter were prepared the same way. The plasma treatment of the samples was carried out with air, as well as with nitrogen (N2, 99.999 %) and oxygen (O2, 99.995 %) from the manufacturer Westfalen AG (Münster, Germany). To minimize contact with the atmosphere prior to XPS measurements, the plasma chamber was vented with argon (Ar, 99.999 %) after the treatment. One part of the samples was directly transferred to the XPS under argon atmosphere for the initial measurements while the other part was stored for a defined time within covered Petri dishes, which prevented the contamination with particles from the environment and at the same time allowed an exchange of air and thus the direct influence of the atmosphere.

Low-pressure plasma treatment

The plasma treatment was carried out by using a commercial low-pressure plasma system MiniFlecto® from plasma technology GmbH (Herrenberg-Gültstein, Germany) which has a variable frequency of 20-50 kHz and a maximum power of 80 W. The experiments were carried out at maximum power. The process was performed pressure-controlled with a fixed pressure of 0.2 mbar and a resulting gas flow of about 2 sccm. Before the plasma was ignited, the chamber was purged with the process gas for 90 seconds to ensure stable atmospheric conditions. The parameters were previously optimized with regard to the greatest influence on the water contact angle, since this parameter is crucial for subsequent coating or use in biological systems. The pressure inside the vacuum chamber was measured by a Pirani sensor, the gas flow control via mass-flow-controller. The surface treatment was performed by direct exposure of the sample to the plasma for 180 seconds, the distance between the sample and the electrode was 40 mm. The sample transfer into the XPS was performed under argon atmosphere with minimal atmospheric contact, the transfer from the process chamber into the transport vessel was realized under constant argon flow. XPS measurements were performed initially and after seven days of storage while the water contact angle was monitored daily.

Surface characterization methods
Contact angle measurement

The contact angles of the differently treated PEEK samples were measured using an OCA20 goniometer by dataphysics (Filderstadt, Germany). In addition, the manufacturer’s SCA20 software was used to perform drop contour analysis, define a baseline, and determine the resulting angles. The test liquids used were water, formamide, diiodomethane, n-dodecane; ethylene glycol and glycerol. To determine the contact angle, the sessile drop method was used. For this purpose, a droplet of 5μL was dosed onto the surface and after 10 seconds the contact angle at the three-phase point was measured. The surface tensions (γltotal) taken from the literature, as well as their polar (γlp) and disperse (γld) respectively acidic (γla) and alkaline (γlb) components as well as the lewis-component (γlLW), needed for the subsequent calculation of the surface energy, are listed in (Table 1).

Surface energy determination according to Owens, Wendt, Rabel and Kaelble

The method by Owens, Wendt, Rabel, and Kaelble (OWRK) was used for determining surface free energy and is based on the Young equation (1).

γ_sv=γsl+γlv*cosϴ (1)

This equation establishes a relationship between the surface tension of the liquid, the interfacial tension between the solid and the liquid, the surface free energy of the solid and the resulting measurable contact angle and is fundamental to many approaches in surface free energy calculation. In the OWRK method, the solidvapor and liquid-vapor-interactions are split into a polar and a dispersive component (2) and the interfacial tension is interpreted as a geometric mean of the disperse and polar component, see (3).

γ_sv=γ_sv^d+γ_sv^p and γ_sv=γ_lv^d+γ_lv^p (2)

γ_sl=γ_sv+γ_lv-2√(γ_sv^d*γ_lv^d )-2√(γ_sv^p*γ_lv^p ) (3)

Thus, in addition to the calculation of the surface free energy, the division into polar, including hydrogen-bonding, and disperse interactions is also possible by using in minimum two different liquids 17,18. For the experiments carried out, the surface energy was calculated taking into account the contact angles of all 6 test liquids (see above).

Characterization of Acid/Base Properties

For the characterization of the acid/base properties two different methods were applied, namely the method by van Oss, Chaudhury and Good (vOCG) and the Berger method.

Van Oss, chaudhury and good

The method by van Oss, Chaudhury and Good is also based on Young`s equation (1) but divides the surface tensions into an apolar component and an acid/base component (4).

γ_sv=γ_sv^LW+γ_sv^AB and γ_lv=γ_lv^LW+γ_lv^AB (4)

This is further subdivided into electron acceptors or donors according to the acid/base definition of Lewis under use of the geometric mean, see (5). Thereby it is assumed that hydrogen bonds are also included into σAB:

γ_sv^AB=2√(γ_sv^+*γ_sv^- ) and γ_lv^AB=2√(γ_lv^+*γ_lv^- ) (5)

γ_sl=γ_sv+γ_lv-2√(γ_sv^LW*γ_lv^LW)-2√(γ_sv^+*γ_lv^- )-2√(γ_sv^-*γ_lv^+ ) ( 6 )

Following the theory of Lewis, an interaction takes place exclusively between the acid/base pairs with each other, as well as between the apolar Lifshitz-van der Waals fractions of solids and liquids (6). Due to the sometimes-critical reviews regarding this method, Volpe et al published additional instructions for using the method. Accordingly, the set of test liquids used in this work consisted of water, diiodomethane and formamide [17–19].

Berger-Method

Furthermore, the Berger method was used in order to characterize the influence of the plasma treatment on the PEEK surface chemistry. Due to the different contact angles of test liquids with similar disperse and polar components, e.g. formamide and glycerol, Berger extended the usual graphical method by Fowkes. The deviations between the contact angles and therefore in the performed work of adhesion (7) of the liquids led back to the different acid-base properties of the liquids.

W_a=γ_lv*(〖1+cos〗ϴ ) (7)

Assuming that all non-disperse interactions are covered by acid-base interactions, their contribution to adhesion work is calculated by subtracting the liquids’ disperse component from the total adhesion work, see Equation 8. In the case that no acidbase interactions take place, 2√(γ_lv^p ) determined by Equation 9 would be identical for all test liquids.

W_a^AB=W_a-W_a^d=W_a-(2*√(γ_lv^d*γ_s^d )) (8)

2√(γ_s^p )=(W_a^AB)/√(γ_lv^p ) (9)

Since this is not the case, the difference between the base pairs of equal surface tensions can be considered as a measure of the acidity of the solid surface. The acidity parameter D introduced by Berger, originally calculated according to equation (10), indicates the character of the surface. Positive values stand for an acidic character, whereas negative values indicate an alkaline character of the surface. Due to the extreme spreading of phenol and aniline on high energetic substrates with surface energies beyond 40 mN/m and the associated limitation of this method, Kraus et al. introduced the shortened acidity parameter Dshort (11) which also found application in this work [10,20,21].

D=2[√(γ_s^p (aniline) )+√(γ_s^p (formamide))]-2[√(γ_s^p (phenol) )+√(γ_s^p (glycerol))]

D_short=2√(γ_s^p (formamide))-2√(γ_s^p (glycerol)) (11)

X-ray photoelectron spectroscopy

The analysis of the PEEK surfaces was carried out with an XPS system from the manufacturer Physical Electronics GmbH (Ismaning, Germany) with the type designation “PHI 5600-CI”. Monochromatic aluminum Kα radiation with an energy of 1486 eV was used. In order to counteract the insulating effect of the PEEK-polymer samples, the electron deficiency of the surface during the measurement was compensated by using an electron emitter. The measurement was carried out under UHV conditions at a pressure of <10-8 Pa, at a 45° angle, the analyzed area was 800μm2. The initial measurements were carried out immediately after the plasma treatment, the transfer of the samples was carried out under an argon atmosphere. Data acquisition and evaluation of the resulting survey spectra were performed using the device manufacturer’s software. Fitting the detail peaks was done using Raymund Kwok’s freeware software XPSPeak 4.1 using a Tougaard background.

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