Surfaces Of Medical Devices Research Articles

Design and evaluation of a skin-like sensor with high stretchability for contact pressure measurement

This paper presents the development of a new type of skin-like tactile pressure sensor array. The sensor array is scalable, flexible and stretchable and can measure pressure up to 250kPa within 30% stretching rate without damaging its mechanical structure. It can also conform to irregular three-dimensional surfaces. The sensor array consists of three layers. The top and bottom layers are formed by the array of parallel conductive strips made of silver nanowires (AgNWs) embedded in polydimethylsiloxane (PDMS) thin films. The AgNWs/PDMS conductor strips are used as stretchable interconnections to transmit electrical signals. The middle layer is made of PDMS. This film is pre-molded with holes filling with cylinder-shaped conductive elastomer for pressure measurement. In this paper, the characteristic of the AgNWs/PDMS conductor strips as stretchable interconnections is studied. The piezoresistive properties of the sensels (one sensing element is called a sensel) were measured and discussed. The performance of the tactile sensor array under stretching was also tested. With the associated scanning power-supply circuit and data acquisition system, it is demonstrated that the system can successfully capture the tactile images induced by objects of different shapes. Such sensor system could be applied on curved or non-planar surfaces in robots or medical devices for force detection and feedback.

DEVELOPMENT OF PEG-CONTAINING BRUSH COPOLYMER: THEIR EFFECT ON RESISTANCE TO PROTEIN ADSORPTION BEHAVIORS

Polyethylene glycol (PEG) has been grafted onto surface of many medical devices to reduce or eliminate protein adsorption that often leads to infection or inflammatory responses. Besides commonly used surface activation strategies, here in this work, the novel functional brush copolymer poly (vinyl alcohol)-g-PEG-co-polyurethane (PVA-g-(PEG-co-PU)) was first synthesized, characterized, and evaluated. PVA is used here as a versatile backbone platform for grafting functional molecules. On the one hand, the PU molecules can attach to the surface of desired PU-based implants, on the other hand, the presence of densely grafted PEG at the materials–tissue interface effectively impedes nonspecific protein adsorption. These copolymers with various grafting ratio of PEG and PU were analyzed by Fourier transform infrared spectroscopy and gel permeation chromatography. The brush copolymers that were obtained were further coated on the PU surface and contact angle measurements were performed. It was found that the brush copolymers turn the surface more hydrophilic with increasing PEG grafting density. Furthermore, the effects of PEG ratio on protein adsorption-resistant behavior were investigated. Protein adsorption was found to be the lowest on the surfaces with the highest PEG grafting density on PVA backbone. The study demonstrated unique brush copolymer to work as a potentially useful coating material.

Inhibition of biofilm formation and antibacterial properties of a silver nano-coating on human dentine

The survival of pathogenic bacteria in the oral cavity depends on their successful adhesion to dental surfaces and their ability to develop into biofilms, known as dental plaque. Bacteria from the dental plaque are responsible for the development of dental caries, gingivitis, periodontitis, stomatitis and peri-implantitis. Certain metal nanoparticles have been suggested for infection control and the management of the oral biofilm. Here, it is shown that application of a silver nano-coating directly on dentine can successfully prevent the biofilm formation on dentine surfaces as well as inhibit bacterial growth in the surrounding media. This silver nano-coating was found to be stable (>98.8%) and to maintain its integrity in biological fluids. Its antibacterial activity was compared to silver nitrate and the widely used clinical antiseptic, chlorhexidine. The bacterial growth and cell viability were quantitatively assessed by measuring the turbidity, proportion of live and dead cells and lactate production. All three bioassays showed that silver nanoparticles and silver nitrate dentine coatings were equally highly bactericidal (>99.5%), while inhibiting bacterial adhesion. However, the latter caused significant dentine discolouration (ΔE* = 50.3). The chlorhexidine coating showed no antibacterial effect. Thus, silver nanoparticles may be a viable alternative to both chlorhexidine and silver nitrate, protecting from dental plaque and secondary caries when applied as a dentine coating, while they may provide the platform for creating anti-biofilm surfaces in medical devices and other biomedical applications.

Dose‐dependent surface endothelialization and biocompatibility of polyurethane noble metal nanocomposites

Surface pre-endothelialization is a promising approach to improve the hemocompatibility of implants, medical devices, and artificial organs. To promote the adhesive property of thermoplastic polyurethane (TPU) for endothelial cells (ECs), up to 1 wt % of gold (Au) or platinum (Pt) nanoparticles, fabricated by pulsed laser ablation in polymer solution, were embedded into the polymer matrix. The analysis of these nanocomposites showed a homogenous dispersion of the nanoparticles, with average diameters of 7 nm for Au or 9 nm for Pt. A dose-dependent effect was found when ECs were seeded onto nanocomposites comprising different nanoparticle concentrations, resulting in a fivefold improvement of proliferation at 0.1 wt % nanoparticle load. This effect was associated with a nanoparticle concentration-dependent hydrophilicity and negative charge of the nanocomposite. In dynamic flow tests, nanocomposites containing 0.1 wt % Au or Pt nanoparticles allowed for the generation of a confluent and resistant EC layer. Real-time polymerase chain reaction quantification of specific markers for EC activation indicated that ECs cultivated on nanocomposites remain in an inactivated, nonthrombogenic and noninflammatory state; however, maintain the ability to trigger an inflammatory response upon stimulation. These findings were confirmed by a platelet and leukocyte adhesion assay. The results of this study suggest the possible applicability of TPU nanocomposites, containing 0.1 wt % Au or Pt nanoparticles, for the generation of pre-endothelialized surfaces of medical devices.

Surface characterisation of ASTM F139 stainless steel marked by laser and mechanical techniques

The surfaces of implantable medical devices should present proper corrosion and mechanical resistance properties to fulfil their functions. Marking techniques are used for identification and traceability purposes but often generate surface modifications. Because surface defects affect corrosion resistance, the effects of marking processes must be investigated. This paper presents the effects of pulsed Nd:YAG laser marking techniques on the corrosion resistance of ASTM F139 austenitic stainless steel compared to that of mechanical marking techniques. The corrosion resistance was evaluated by electrochemical methods, and the surface was analysed by scanning electron microscopy with a field emission gun (SEM-FEG) coupled to an energy dispersive X-ray spectrometer. The surface characterisation showed the occurrence of microstructure variation due to the high temperatures involved in the laser melting process. Compared to the mechanical method, the laser marking technique had a deleterious effect on the resistance of ASTM F139 stainless steel to localised corrosion, increasing its susceptibility to pitting corrosion. These results were related to changes in the passive film properties, surface morphology and chemical composition.

Development of a pantograph based micro-machine for nano-scratching

Micro-nano patterned surfaces possess unique adhesion, wetting and dewetting properties, prompting their growing applications ranging from water repellant windshields of automobiles, antibacterial surfaces of medical devices to algae cultivation for biodiesel generation. The current need is manufacturing systems and processing protocols to create highly controlled patterns directly on solid substrates over large area. In this paper, a pantograph-based desktop micro machine has been designed to create micro-nano scale patterns over 25 mm × 25 mm area directly over solid surfaces by nano-scratching/scribing process. It is designed to achieve precision positioning of scratching tool (tip) and to retain its orientation such that effective rake angle remains unaltered, unlike in atomic force microscopy based scratching techniques. The design of the mechanism and micro-motion analysis achieved by integrating unique design for revolute joints are described. The machine performance in generating micro-patterns over copper and aluminium substrates has been studied.

Cleaning assessment of disinfectant cleaning wipes on an external surface of a medical device contaminated with artificial blood or Streptococcus pneumoniae

Improperly cleaned, disinfected, or sterilized reusable medical devices are a critical cause of health care-associated infections. More effective studies are required to address the improvement of cleaning and disinfection instructions, as well as selection of cleaning and disinfecting agents, for surfaces of reusable devices and equipment. Six commercially available disinfectant cleaning wipes were evaluated for their effectiveness to remove a coagulated blood test soil or Streptococcus pneumoniae bacteria from the surface of a reusable medical device. Liquid aliquots of the coagulated blood or bacteria were dried onto the surface of the device and removed with the wipes. Effectiveness of the wipes was assessed by 3 methods: residual protein debris by o-phthaldialdehyde analysis, bacterial survival by adenosine triphosphate measurement, and force required to remove the dried debris by force measurement. A sodium hypochlorite wipe was most effective in removing protein debris from the device surface. All tested wipes were equivalent in disinfecting bacterial contamination from the device surface. The active ingredient, wipe design, and wipe wetness are important factors to consider when selecting a disinfectant cleaning wipe. Additionally, achieving conditions that effectively clean, disinfect, and/or inactivate surface bacterial contamination is critical to preventing the spread of health care-associated infections.

Fiber-optic Fourier transform infrared spectroscopy for remote label-free sensing of medical device surface contamination

As a potential major source of biochemical contamination, medical device surfaces are of critical safety concerns in the clinical practice and public health. The development of innovative sensing methods for accurate and real-time detection of medical device surface contamination is essential to protect patients from high risk infection. In this paper, we demonstrate an alternative fiber-optic Fourier Transform Infrared (FTIR) spectroscopy based sensing approach for remote, non-contact, and label-free detection of biochemical contaminants in the mid-infrared (mid-IR) region. The sensing probe is designed using mid-IR hollow fibers and FTIR measurements are carried out in reflection mode. Bovine Serum Albumin (BSA) and bacterial endotoxin of different concentrations under thoroughly dry condition are used to evaluate the detection sensitivity. The devised system can identify ≤0.0025% (≤4 × 10(11) molecules) BSA and 0.5% (0.5 EU/ml) endotoxin concentration. The developed sensing approach may be applied to detect various pathogens that pose public health threats.

The role of biofilms in reprocessing medical devices

Biofilms are communities of microorganisms within extracellular polymeric material attached to surfaces. Within a biofilm, cells have some protection from drying and other stress factors in their environment, including antimicrobial agents. In this article, the challenges to medical device reprocessing posed by biofilms are addressed. Biofilm formation on reusable medical device surfaces is a risk that can be controlled. By ensuring prompt device cleaning and reprocessing either by high-level disinfection or sterilization and proper drying, biofilms will not have a chance to form. Reusable medical devices like flexible endoscopes that are promptly cleaned and disinfected, rinsed and dried pose little risk to patients.

Antibiofilm Activity of Scutellaria baicalensis through the Inhibition of Synthesis of the Cell Wall (1, 3)-β-D-Glucan Polymer

Candida biofilms are self-organized microbial communities growing on the surfaces of host tissues and medical devices. These biofilms have been displaying increasing resistance against conventional antifungal agents. The roots of Scutellaria baicalensis have been widely used for medicinal purpose throughout East Asia. The aim of the present study was to evaluate the effect of S. baicalensis aqueous extract upon the preformed biofilms of 10 clinical C. albicans isolates, and assess the mechanism of the antibiofilm activity. Its effect on preformed biofilm was judged using an XTT reduction assay and the metabolic activity of all tested strains were reduced (%) at MIC values. The S. baicalenis extract inhibited (1, 3)--D-glucan synthase activity. The effect of S. baicalensis on the morphology of C. albicans was related to the changes in growth caused by inhibiting glucan synthesis; most cells were round and swollen, and cell walls were densely stained or ruptured. The anticandidal activity was fungicidal, and the extract also arrested C. albicans cells at . The data suggest that S. baicalensis has multiple fatal effects on target fungi, which ultimately result in cell wall disruption and killing by inhibiting (1, 3)--D-glucan synthesis. Therefore, S. baicalensis holds great promise for use in treating and eliminating biofilm-associated Candida infections.

Removal of a Natural Toxin Surrogate from Water, Material Surfaces, and Reusable Medical Devices

Water and reusable medical device surfaces can be contaminated by natural toxins such as ricin either accidentally or intentionally. This report focuses on the removal of peanut lectin (PL), a ricin surrogate, from water and reusable medical devices and materials. An ELISA assay was used to determine if commercially available water filters could remove peanut lectin from water, and if commercially available cleaning/disinfecting wipes could denature peanut lectin from the surfaces of various medical device materials. Several medical devices and materials were tested to evaluate their surface retention of peanut lectin following cleaning. Reverse osmosis, ion exchange, and combination mechanical barrier systems were effective in removing peanut lectin from water. Wipes containing sodium hypochlorite were most effective in completely denaturing peanut lectin within 2 minutes of contact. The efficacy of removal of peanut lectin from the surfaces of six medical device materials and three medical devices ranged from 76% to 102% and 64% to 103%, respectively.

The Intervention of Nanotechnology Against Epithelial Fungal Diseases

Fungal infections can attack epithelial tissues and, according to the immunological state of the patient, some of them invade deeper organs, becoming seriously life compromising. Besides, bloodstream and local infections associated with intravascular devices constitute a significant problem associated with increased mortality. Topical therapy is desirable since, in addition to targeting the site of infection, it reduces the risk of systemic side effects and increases patient compliance. In this review we describe the pros and cons of using nano-objects that being toxic in nature could be used to cover surfaces of medical devices, or can act as carriers for targeted delivery of antifungals to skin. Non-toxic nano-objects were also included because they improve the ocular delivery of antifungals, classically suffering from ineffective topical administration, difficult access for systemic medication or local invasive administration. The new preclinical developments of nanoparticulate agents against cutaneous and ocular mycosis are grouped in three main sections: (1) In vitro antifungal activity of metallic nanoparticles, (2) In vitro and in vivo antifungal activity of non metallic nanoparticles (3) Ocular delivery of non metallic nanoparticles.

Reduced adhesion of Staphylococcus aureus to ZnO/PVC nanocomposites

In hospitals and clinics worldwide, medical device surfaces have become a rapidly growing source of nosocomial infections. In particular, patients requiring mechanical ventilation (and, thus, intubation with an endotracheal tube) for extended lengths of time are faced with a high probability of contracting ventilator-associated pneumonia. Once inserted into the body, the endotracheal tube provides a surface to which bacteria can adhere and form a biofilm (a robust, sticky matrix that provides protection against the host immune system and antibiotic treatment). Adding to the severity of this problem is the spread of bacterial genetic tolerance to antibiotics, in part demonstrated by the recent and significant increase in the prevalence of methicillin-resistant Staphylococcus aureus. To combat these trends, different techniques in biomaterial design must be explored. Recent research has shown that nanomaterials (materials with at least one dimension less than 100 nm) may have the potential to prevent or disrupt bacterial processes that lead to infections. In this study, polyvinyl chloride (PVC) taken from a conventional endotracheal tube was embedded with varying concentrations of zinc oxide (ZnO) nanoparticles. S. aureus biofilms were then grown on these nanocomposite surfaces during a 24-hour culture. Following this, biofilms were removed from the surfaces and the number of colony forming units present was assessed. Bacterial proliferation on the samples embedded with the highest concentration of ZnO nanoparticles was 87% less when compared to the control, indicating that this technique is effective at reducing biofilm formation on PVC surfaces without the use of antibiotics.

Nanostructured polyurethane-poly-lactic-co-glycolic acid scaffolds increase bladder tissue regeneration: an in vivo study.

Although showing much promise for numerous tissue engineering applications, polyurethane and poly-lactic-co-glycolic acid (PLGA) have suffered from a lack of cytocompatibility, sometimes leading to poor tissue integration. Nanotechnology (or the use of materials with surface features or constituent dimensions less than 100 nm in at least one direction) has started to transform currently implanted materials (such as polyurethane and PLGA) to promote tissue regeneration. This is because nanostructured surface features can be used to change medical device surface energy to alter initial protein adsorption events important for promoting tissue-forming cell functions. Thus, due to their altered surface energetics, the objective of the present in vivo study was to create nanoscale surface features on a new polyurethane and PLGA composite scaffold (by soaking the polyurethane side and PLGA side in HNO3 and NaOH, respectively) and determine bladder tissue regeneration using a minipig model. The novel nanostructured scaffolds were further functionalized with IKVAV and YIGSR peptides to improve cellular responses. Results provided the first evidence of increased in vivo bladder tissue regeneration when using a composite of nanostructured polyurethane and PLGA compared with control ileal segments. Due to additional surgery, extended potentially problematic healing times, metabolic complications, donor site morbidity, and sometimes limited availability, ileal segment repair of a bladder defect is not optimal and, thus, a synthetic analog is highly desirable. In summary, this study indicates significant promise for the use of nanostructured polyurethane and PLGA composites to increase bladder tissue repair for a wide range of regenerative medicine applications, such as regenerating bladder tissue after removal of cancerous tissue, disease, or other trauma.

Comparison of Test Methods To Screen For Residual Chemical Contamination On Medical Device Surfaces

Reprocessing medical devices involves several steps including cleaning and disinfection or sterilization. Chemical residuals can occur at various stages of reprocessing. These residues could interfere with device function and potentially harm patients. These solutions are composed of a combination of various chemicals and their residues are highly diluted post rinsing, therefore, it is difficult to find a sensitive and rapid method to detect toxicity due to chemical residues. This study focused on (1) finding the levels of residues that are cytotoxic using two mammalian cell lines and Daphnia magna, and (2) evaluating two test methods, Total Organic Carbon (TOC) and the Luminescent Bacteria Test (LBT), to measure residual chemicals levels. The two mammalian cell lines were equal in their cytotoxicity responses. However, Daphnia were more sensitive to some chemical residue than the two mammalian cell lines. TOC and LBT were able to detect the presence of residue well below the levels that were determined to cause mammalian cytotoxicity. LBT was more sensitive for some chemicals and TOC for others, both in solution and in simulated cleaning and rinsing for the limited number of solutions tested in this study.

Blooming of Irganox 3114® antioxidant onto a medical grade elastomer. Impact of the recrystallization conditions on the antioxidant polymorphism, on the film wettability and on the antioxidant leachability

Studying the blooming and recrystallization of additives onto the surface of polymer medical devices is of a great interest because it can affect the biocompatibility of the material. The polymorphism of a phenolic antioxidant (Irganox 3114(®)) used as an additive in medical devices and pharmaceutical packaging was studied: two different polymorphs were characterized by differential scanning measurements, FTIR and X-ray diffraction analyses. Then, the behavior of the additive in medical grade polyurethane films was described: a recrystallization into the stable polymorphic form was observed onto the polymer surface after annealing at different temperatures. The morphology observed depends not only on the additive/polymer ratio but also on the whole amount of additive in the polymer film. Depending on the recrystallization morphology, the wettability with water could be lowered and the leachability of the additives into aqueous media could be favored.

Nanostructured selenium for preventing biofilm formation on polycarbonate medical devices

Biofilms are a common cause of persistent infections on medical devices as they are easy to form and hard to treat. The objective of this study was for the first time to coat selenium (a natural element in the body) nanoparticles on the surface of polycarbonate medical devices (such as those used for medical catheters) and to examine their effectiveness at preventing biofilm formation. The size and distribution of selenium coatings were characterized using scanning electron microscopy and atomic force microscopy. The strength of the selenium coating on polycarbonate was assessed by tape-adhesion tests followed by atomic absorption spectroscopy. Results showed that selenium nanoparticles had a diameter of 50-100 nm and were well distributed on the polycarbonate surface. In addition, more than 50% of the selenium coating survived the tape-adhesion test as larger nanoparticles had less adhesion strength to the underlying polycarbonate substrate than smaller selenium nanoparticles. Most significantly, the results of this in vitro study showed that the selenium coatings on polycarbonate significantly inhibited Staphylococcus aureus growth to 8.9% and 27% when compared with an uncoated polycarbonate surface after 24 and 72 h, respectively. Importantly, this was accomplished without using antibiotics but rather with an element (selenium) that is natural to the human body. Thus, this study suggests that coating polymers (particularly, polycarbonate) with nanostructured selenium is a fast and effective way to reduce bacteria functions that lead to medical device infections. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 100A: 3205-3210, 2012.

Progress in stenotrophomonas maltophilia

Stenotrophomonas maltophilia(SMA) is a emerging opportunistic pathogen that can cause difficult-to-treat infections and exhibits significant degrees of poorly understood multidrug resistance,especially in irnmunocompromised patients.SMA is not an inherent virulent pathogen,but it can colonize in respiratorytract epithelial cells and surfaces of medical devices make it an important colonizer in hospitalized patients.Management of SMA infection is hampered because of its high-level intrinsic resistance to many antibiotics and the increasing occurrence of acquired resistance to the first-line drug such as co-trimoxazole.The prevention and treatment of SMA infection attract more and more attention in recent years. Key words: Stenotrophomonas maltophilia; Infection; Drug-resistance

3‐dimensional imaging and quantification of cell adherence on curved surfaces of medical grade devices using confocal lasers‐canning microscopy

3‐D confocal laser‐scanning microscopy is an ideal way to visualize a sample with a curved surface. An application of this method involves the quantification of activated blood leukocytes and platelets adhering to the surface of medical grade catheters. Human blood was perfused across treated and untreated catheters using a microperfusion system and fixed with paraformaldehyde. Portions of each catheter were immunostained and 5 random fields were imaged using a Leica SP2 microscope (20× objective; 2× optical zoom). Image stacks were loaded into image analysis software and transformed into a max intensity projection. From this 2‐D projection, area occupied by fluorescence was calculated by implementing a binary threshold layer above isotypic control. Area fluorescence was divided by the mean area of a single cell, generating a cell count per unit area. Results are presented as adherent cells/mm2 ± SEM. The treated surface showed reduced adherent cell counts (monocytes: 0.67 ± 1.03, polymorphs: 1.33 ± 3.99, lymphocytes: 0.62 ± 1.86, platelets: 1.33 ± 3.99) compared to the untreated surface (monocytes: 302.43 ± 215.55, polymorphs: 1647.56 ± 615.54, lymphocytes: 38.46 ± 29.59, platelets: 4076.23 ± 2867.3). This method can be used to capture and quantify large amounts of data that may be obscured or otherwise unavailable when imaging curved surfaces, such as in biocompatibility assessment of medical devices.

Efficacy of acidic and basic electrolyzed water in eradicating Staphylococcus aureus biofilm

Staphylococcus aureus is a major pathogen. It can form biofilm on the surfaces of medical devices and food equipment, which makes it more difficult to eradicate. To develop a novel method to eradicate S. aureus biofilm, the effects of electrolyzed water on removing and killing S. aureus biofilm were investigated in this study. By using a biofilm biomass assay with safranin staining and visualization of biofilm architecture with scanning electron microscopy, it was shown that basic electrolyzed water (BEW) could effectively remove established biofilm. The pH of electrolyzed water affected removal efficacy. Using a biofilm viability assay with 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide staining, acidic electrolyzed water (AEW) efficiently killed biofilm-imbedded S. aureus. The available chlorine in AEW may be a main contributing factor for bactericidal activity. Additionally, BEW had a removal efficacy for S. aureus biofilm equivalent to 2% NaOH, and AEW had a bactericidal capability for S. aureus in biofilm equivalent to 2% HCl. These data suggested that AEW and BEW could be applied as a bactericide and removing agent for S. aureus in biofilm, respectively.