Efficacy of silver/hydrophilic poly(p-xylylene) on preventing bacterial growth and biofilm formation in urinary catheters

Electrosprayed zein nanoparticles as antibacterial and anti-thrombotic coatings for ureteral stents

Ureteral stents are among the most frequently used human implants, with urothelium trauma, blood clots, and bacterial colonization being their main reasons for failure. In this study, berberine-loaded zein (ZB) nanoparticles with high drug encapsulation efficiency (>90 %) were fabricated via electrospray on flat and 3D stainless steel structures. Physico-chemical characterization revealed that the ZB nanoparticles created a highly hydrophilic, antioxidant, and scratch-resistant continuous coating over the metal structure. Results showed that the drug release rate was faster at neutral pH (i.e., PBS pH 7.4) than in an artificial urine medium (pH 5.3) due to the different swelling behavior of the zein polymeric matrix. In vitro evaluation of ZB particles onto human dermal fibroblasts and blood cells demonstrated good cell proliferation and enhanced anti-thrombotic properties compared to bare stainless steel. The ability of the electrosprayed zein particles to resist bacterial adherence and proliferation was evaluated with Gram-negative (Escherichia coli) bacteria, showing high inhibition rates (-29 % and -46 % for empty and berberine-loaded particles, respectively) compared to the medical-grade metal substrates. Overall, the proposed composite coating fulfilled the requirements for ureteral applications, and can advance the development of innovative biocompatible, biodegradable, and antibacterial coatings for drug-eluting stents.

Effect of DMPEI coating against biofilm formation on PVC catheter surface

Urinary tract infections (UTIs) are a significant cause of morbidity in healthcare systems and are prominently associated with applying urethral catheters, particularly in surgeries. Polyvinyl chloride (PVC) is extensively utilized in the fabrication of catheters. Biofilms, complex polymeric constructions, provide a protective milieu for cell multiplication and the enhancement of antibiotic resistance. Strategies to counteract biofilm development on medical apparatuses' surfaces incorporate antimicrobial agents such as N,N-dodecyl, and methyl polyethylenimine (DMPEI). This research endeavored to characterize the morphology of PVC and PVC-DMPEI surfaces utilizing Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) and to gauge hydrophobicity through contact angle measurements. Employing Escherichia coli, Staphylococcus aureus, and Candida albicans in adhesion assays enabled the assessment of DMPEI's efficacy in preventing microbial adherence to PVC. Butanol successfully solubilized 2 mg.mL-1 DMPEI without altering the PVC structure. SEM results substantiated the formation of a DMPEI layer on the PVC surface, which led to decreased surface roughness, as validated by AFM, and increased hydrophilicity, as demonstrated by contact angle evaluations. E. coli, S. aureus, and C. albicans exhibited significant adhesion reduction, 89.3%, 94.3%, and 86.6% on PVC-DMPEI surfaces. SEM visualizations confirmed reduced cellular colonization on PVC-DMPEI and highlighted considerable morphological modifications in E. coli. Consequently, DMPEI films effectively minimize the adhesion of E. coli, S. aureus, and C. albicans on PVC surfaces. DMPEI, with its potential as a protective coating for innovative medical devices, promises to inhibit biofilm adherence effectively.

Current material engineering strategies to prevent catheter encrustation in urinary tracts

Catheters and ureteric stents have played a vital role in relieving urinary obstruction in many urological conditions. With the increasing use of urinary catheters/stents, catheter/stent-related complications such as infection and encrustation are also increasing because of their design defects. Long-term use of antibiotics and frequent replacement of catheters not only increase the economic burden on patients but also bring the pain of catheter replacement. This is unfavorable for patients with long indwelling catheters or stents but inconvenient to replace. In recent years, some promising technologies and mechanisms have been used to prevent infection and encrustation, mainly drug loading coatings, functional coatings, biodegradable polymers and metallic materials for urinary devices. Obvious effects in anti-encrustation and anti-infection experiments of the above strategies in vivo or in vitro have been conducted, which is very helpful for further clinical trials. This review mainly introduces catheter/stent technology and mechanisms in the past ten years to address the potential impact of anti-encrustation coating of catheter/stent materials for the prevention of encrustation and to analyze the progress made in this field.

Interactive Effects of Copper-Doped Urological Implants with Tissue in the Urinary Tract for the Inhibition of Cell Adhesion and Encrustation in the Animal Model Rat

The insertion of a ureteral stent provides acute care by restoring urine flow and alleviating urinary retention or dysfunction. The problems of encrustation, bacterial colonization and biofilm formation become increasingly important when ureteral stents are left in place for a longer period of time. One way to reduce encrustation and bacterial adherence is to modify the stent surface with a diamond-like carbon coating, in combination with copper doping. The biocompatibilities of the Elastollan^® base material and the a-C:H/Cu-mulitilayer coating were tested in synthetic urine. The copper content in bladder tissue was determined by atomic absorption spectroscopy and in blood and in urine by inductively coupled plasma mass spectrometry. Encrustations on the materials were analyzed by scanning electron microscopy, energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy. A therapeutic window for copper ions of 0.5–1.0 mM was determined to kill bacteria without affecting human urothelial cells. In the rat animal model, it was found that copper release did not reach toxic concentrations in the affecting tissue of the urinary tract or in the blood. The encrustation behavior of the surfaces showed that the roughness of the amorphous carbon layer with the copper doping is probably the causal factor for the higher encrustation.

In vitro and in vivo studies on bacteria and encrustation resistance of heparin/poly-L-lysine-Cu nanoparticles coating mediated by PDA for ureteral stent application

Ureteral stents are commonly utilized as a medical device to aid the flow of urine. However, biofilm formation and encrustation complications have been clinical problems. To overcome this challenge, heparin/poly-L-lysine-copper (Hep/PLL-Cu) nanoparticle was immobilized on a dopamine-coated polyurethane surface (PU/NPs). The stability and structural properties of the nanoparticles were characterized by Zeta potential, poly dispersion index, transmission electron microscopy, atom force microscopy and contact angle. The surface composition, antibacterial potency, encrustation resistance rate and biocompatibility of PU/NPs were investigated by scanning electron microscope, X-ray photoelectron spectroscopy, antibacterial assay and MTS assay, respectively. In addition, the anti-encrustation property was studied by implanting coated NPs stents in the rat bladder for 7 days. It was shown that the size and distribution of Hep/PLL-Cu nanoparticles were uniform. PU/NPs could inhibit Proteus mirabilis proliferation and biofilm formation, and exhibit no cytotoxicity. Less encrustation (Ca and Mg salt) was deposited both in vitro and in vivo on samples, demonstrating that the NPs coating could be a potential surface modification method of ureteral material for clinical use.

Internal Coating of Ureteral Stents with Chemical Vapor Deposition of Parylene

Ureteral balloon catheters and ureteral stents are implanted in large quantities on a daily basis. They are the suspected cause for about a quarter of all the nosocomial infections, which lead to approx. 20,000 deaths in Germany alone. To fight these infections, catheters should be made antibacterial. A technique for an antibacterial coating of catheters exhibiting an aspect ratio of up to 200 consists of a thin silver layer, which is deposited out of an aqueous solution, which is followed by a second step: chemical vapor deposition (CVD) of an organic polymeric film, which moderates the release rate of silver ions. The main concern of the second step is the longitudinal evenness of the film. For tubes with one opening as balloon catheters, this issue can be solved by applying a descendent temperature gradient from the opening to the end of the catheter. An alternative procedure can be applied to commercially available ureteral stents, which exhibit small drainage openings in their middle. The same CVD as before leads to a longitudinal homogeneity of about ±10%—at very low costs. This deposition can be modeled using viscous flow.

Plasma Enhanced Chemical Vapor Deposition of Organic Polymers

Chemical Vapor Deposition (CVD) with its plasma-enhanced variation (PECVD) is a mighty instrument in the toolbox of surface refinement to cover it with a layer with very even thickness. Remarkable the lateral and vertical conformity which is second to none. Originating from the evaporation of elements, this was soon applied to deposit compound layers by simultaneous evaporation of two or three elemental sources and today, CVD is rather applied for vaporous reactants, whereas the evaporation of solid sources has almost completely shifted to epitaxial processes with even lower deposition rates but growth which is adapted to the crystalline substrate. CVD means first breaking of chemical bonds which is followed by an atomic reorientation. As result, a new compound has been generated. Breaking of bonds requires energy, i.e., heat. Therefore, it was a giant step forward to use plasmas for this rate-limiting step. In most cases, the maximum temperature could be significantly reduced, and eventually, also organic compounds moved into the preparative focus. Even molecules with saturated bonds (CH4) were subjected to plasmas—and the result was diamond! In this article, some of these strategies are portrayed. One issue is the variety of reaction paths which can happen in a low-pressure plasma. It can act as a source for deposition and etching which turn out to be two sides of the same medal. Therefore, the view is directed to the reasons for this behavior. The advantages and disadvantages of three of the widest-spread types, namely microwave-driven plasmas and the two types of radio frequency-driven plasmas denoted Capacitively-Coupled Plasmas (CCPs) and Inductively-Coupled Plasmas (ICPs) are described. The view is also directed towards the surface analytics of the deposited layers—a very delicate issue because carbon is the most prominent atom to form multiple bonds and branched polymers which causes multifold reaction paths in almost all cases. Purification of a mixture of volatile compounds is not at all an easy task, but it is impossible for solids. Therefore, the characterization of the film properties is often more orientated towards typical surface properties, e.g., hydrophobicity, or dielectric strength instead of chemical parameters, e.g., certain spectra which characterize the purity (infrared or Raman). Besides diamond and Carbon Nano Tubes, CNTs, one of the polymers which exhibit an almost threadlike character is poly-pxylylene, commercially denoted parylene, which has turned out a film with outstanding properties when compared to other synthetics. Therefore, CVD deposition of parylene is making inroads in several technical fields. Even applications demanding tight requirements on coating quality, like gate dielectrics for semiconductor industry and semi-permeable layers for drug eluting implants in medical science, are coming within its purview. Plasma-enhancement of chemical vapor deposition has opened the window for coatings with remarkable surface qualities. In the case of diamond and CNTs, their purity can be proven by spectroscopic methods. In all the other cases, quantitative measurements of other parameters of bulk or surface parameters, resp., are more appropriate to describe and to evaluate the quality of the coatings.

Impact of DMPEI on Biofilm Adhesion on Latex Urinary Catheter

BACKGROUND

Microorganisms can migrate from the external environment to the patient's organism through the insertion of catheters. Despite being indispensable medical device, the catheter surface can be colonized by microorganisms and become a starting point for biofilm formation. Therefore, new technologies are being developed in order to modify surfaces to prevent the adhesion and survival of microorganisms. Patents with the use of DMPEI have been filed.

OBJECTIVE

In the present work, we coated latex catheter surfaces with 2 mg mL-1 DMPEI in different solvents, evaluated the wettability of the surface and the anti- biofilm activity of the coated catheter against Escherichia coli, Staphylococcus aureus, and Candida albicans.

METHODS

We coated the inner and outer catheter surfaces with 2 mg mL-1 of DMPEI solubilized in butanol, dimethylformamide, and cyclohexanone and the surfaces were analyzed visually. Contact angle measurement allowed the analysis of the wettability of the surfaces. The CFU mL-1 count evaluated E. coli, S. aureus, and C. albicans adhesion onto the control and treated surfaces.

RESULTS

The contact angle decreased from 50.48º to 46.93º on the inner surface and from 55.83º to 50.91º on the outer surface of latex catheters coated with DMPEI. The catheter coated with DMPEI showed anti-biofilm activity of 83%, 88%, and 93% on the inner surface and 100%, 92%, and 86% on the outer surface for E. coli, S. aureus, and C. albicans, respectively.

CONCLUSION

Latex catheter coated with DMPEI efficiently impaired the biofilm formation both on the outer and inner surfaces, showing a potential antimicrobial activity along with a high anti-biofilm activity for medical devices.

Silicone Oil Decreases Biofilm Formation in a Capacitance-Based Automatic Urine Measurement System

Capacitance-based automatic urine measurement is a validated technique already implemented in clinical practice. However, albuminuria and free hemoglobinuria cause progressive biofilm buildup on the capacitance sensors of the urinometers. The aim of this experimental study is to investigate the influence of albumin and free hemoglobin on the capacitance signal of an automatic urinometer with and without the addition of silicone oil. A solution of Ringer’s acetate mixed with either albumin or free hemoglobin was run through an automatic urinometer containing either a water-soluble capsule with silicone oil or not. In total, around 500 capacitance measurements were retrieved from the albumin and free hemoglobin group, respectively. The mean increase in capacitance in the albumin 3 g/L group was 257 ± 100 pF without and 105 ± 30 pF with silicone oil, respectively, during 24 h. After ten hours of recording, differences between the two albumin groups reached statistical significance. For the free hemoglobin groups (0.01 g/L), the mean increase in capacitance was 190 ± 170 pF with silicone oil, and 324 ± 80 pF without, with a significant difference between the groups after 20 h and onwards. Coating of the capacitance measurement membrane of the automatic urinometer by albumin or free hemoglobin was significantly decreased by silicone oil, prolonging the functionality of the device.

Colorimetric and electrochemical detection of pathogens in water using silver ions as a unique probe

The manuscript highlights the efficacy of silver ions to act as a unique probe for the detection of bacterial contamination in water samples. The bacterial cell membrane adherence property of the silver ions was employed to develop two different bacterial detection assays employing colorimetric and electrochemical techniques. In one of the schemes, silver ion was used directly as a detector of bacteria in a colorimetric assay format, and in the other scheme surface-functionalized antibodies were used as a primary capture for specific detection of Salmonella enterica serovar Typhi. The colorimetric detection is based on silver-induced inhibition of urease activity and silver ion utilization by bacteria for the rapid screening of enteric pathogens in water. The specific detection of bacteria uses an antibody-based electrochemical method that employs silver as an electrochemical probe. The ability of silver to act as an electrochemical probe was investigated by employing Anodic Stripping Voltammetry (ASV) for targeted detection of Salmonella Typhi. For further insights into the developed assays, inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) studies were performed. The sensitivity of the developed assay was found to be 100 cfu mL⁻¹ for colorimetric and 10 cfu mL⁻¹ for electrochemical assay respectively.

Making medical devices safer: impact of plastic and silicone oil on microbial biofilm formation

BACKGROUND

Medical devices face the challenge of microbial biofilm attached to the surface. Ultimately, this may jeopardize the function of the device and increase the patient's risk of infection. However, reliable methods to prevent biofilm are lacking.

AIM

To investigate the effect of silicone oil-coated polypropylene plastic, used in a new automatic urinometer, on biofilm formation; furthermore, to explore the impact of silicone oil viscosity and compare polypropylene with polystyrene, another common medical plastic.

METHODS

Common pathogens, including extended-spectrum beta lactamase (ESBL) -producing and multi-drug-resistant bacteria, as well as Candida albicans, were investigated. Isogenic Escherichia coli strains deficient in the important biofilm forming factors curli, cellulose and type 1 fimbriae (fim D) were used to determine the possible mode of action by silicone oil. Clear flat-bottomed polypropylene or polystyrene wells were pretreated with either low- or medium-viscosity silicone oil and microbes were added. After 72 h, biofilm formation was quantified using crystal violet assay.

FINDINGS

Silicone oil-coated polypropylene plastic surfaces, regardless of the oil viscosity, significantly inhibited biofilm formation of all tested Gram-negative and Gram-positive bacteria, including ESBL-producing and multi-drug resistant strains, as well as C. albicans. Silicone oil did not affect bacterial or candida growth and curli fimbriae were found to be the main target of silicone oil. Polypropylene plastic itself without oil had a better effect in preventing biofilm formation than polystyrene.

CONCLUSION

These findings suggest a new strategy to decrease microbial biofilm formation, which may reduce hospital-acquired infections and prevent dysfunction of medical devices.

The Use of Copper as an Antimicrobial Agent in Health Care, Including Obstetrics and Gynecology

Health care-associated infections (HAIs) are a global problem associated with significant morbidity and mortality. Controlling the spread of antimicrobial-resistant bacteria is a major public health challenge, and antimicrobial resistance has become one of the most important global problems in current times. The antimicrobial effect of copper has been known for centuries, and ongoing research is being conducted on the use of copper-coated hard and soft surfaces for reduction of microbial contamination and, subsequently, reduction of HAIs. This review provides an overview of the historical and current evidence of the antimicrobial and wound-healing properties of copper and explores its possible utility in obstetrics and gynecology.

Tailored antimicrobial activity and long-term cytocompatibility of plasma polymer silver nanocomposites

The deposition of coatings enabling antibacterial properties in combination with cytocompatibility remains a challenge for biomaterial applications, such as in medical devices. Silver is one of the most utilized antibacterial surface components, due to its efficacy and extensive applicability. In this work, silver-containing plasma polymer nanocomposites (single layer and multilayers) were developed and tested, with a focus on cytotoxicity and bactericidal function, on the NIH3T3 mammalian cell line as well as Gram-negative ( Pseudomonas aeruginosa) and Gram-positive ( Staphylococcus aureus) bacterial strains. The data demonstrate that a tuneable Ag⁺ release is required, allowing sufficient antimicrobial activity while retaining appropriate cytocompatibility over the entire testing period of up to eight days.

Archaeal tetraether lipid coatings-A strategy for the development of membrane analog spacer systems for the site-specific functionalization of medical surfaces

The primary goal of our investigation was the development of a versatile immobilization matrix based on archaeal tetraether lipids that meets the most important prerequisites to render an implant surface bioactive by binding specific functional groups or functional polymers with the necessary flexibility and an optimal spatial arrangement to be bioavailable. From this point of view, it appears obvious that numerous efforts made recently to avoid initial bacterial adhesion on catheter surfaces as an important prerequisite of material associated infection episodes have shown only a limited efficiency since the bioactive entities could not be presented in an optimal conformation and a stable density. A significant improvement of this situation can be achieved by highly specific biomimetic modifications of the catheter surfaces. The term "biomimetic" originates from the fact that specific archaeal tetraether lipids were introduced to form a membrane analog monomolecular spacer system, which (1) can be immobilized on nearly all solid surfaces and (2) chemically modified to present a tailor-made functionality in contact with aqueous media either to avoid or inhibit surface fouling or to equip any implant surface with the necessary chemical functionality to enable cell adhesion and tissue integration. Ultrathin films based on tetraether lipids isolated from archaea Thermoplasma acidophilum were used as a special biomimetic immobilization matrix on the surface of commercial medical silicon elastomers. A complete performance control of the membrane analog coatings was realized in addition to biofunctionality tests, including the proof of cytotoxicity and hemocompatibility according to DIN EN ISO 10993. In order to make sure that the developed immobilization matrix including the grafted functional groups are biocompatible under in vivo-conditions, specific animal tests were carried out to examine the in vivo-performance. It can be concluded that the tetraether lipid based coating systems on silicone have shown no signs of cytotoxicity and a good hemocompatibility. Moreover, no mutagenic effects, no irritation effects, and no sensitization effects could be demonstrated. After an implantation period of 28 days, no irregularities were found.

Bi-layer sandwich film for antibacterial catheters

Background: Approximately one quarter of all nosocomial infections can be attributed to the urinary tract. The infections are supposed to be mainly caused by implantations of urethral catheters and stents. A new catheter design is introduced with the aim to lower the high number of nosocomial urethral infections. In order to avoid limitations to use, the design is first applied to conventional commercially available balloon catheters. Results: The main feature of the design is a sandwich layer on both sides of the catheter wall, which is composed of a fragmented base layer of silver capped by a thin film of poly(p-xylylene). This top layer is mainly designed to release a controlled amount of Ag⁺ ions, which is bactericidal, but not toxic to humans. Simultaneously, the lifetime is prolonged to at least one year. The base layer is electrolessly deposited applying Tollens' reagens, the cap layer is deposited by using chemical vapor deposition. Conclusion: The three main problems of this process, electroless deposition of a fragmented silver film on the surface of an electrically insulating organic polymer, irreproducible evaporation during heating of the precursor, and exponential decrease of the layer thickness along the capillary, have been solved trough the application of a simple electrochemical reaction and two standard principles of physics: Papin's pot and the principle of Le Chatelier.