An Evaluation of Parylene Thin Films to Prevent Encrustation for a Urinary Bladder Pressure MEMS Sensor System.

Recent developments in urological implants have focused on preventive strategies to mitigate encrustation and biofilm formation. Parylene, a conformal, pinhole-free polymer coating, has gained attention due to its high biocompatibility and chemical resistance, excellent barrier properties, and low friction coefficient. This study aims to evaluate the effectiveness of parylene C in comparison to a parylene VT4 grade coating in preventing encrustation on a urinary bladder pressure MEMS sensor system. Additionally, silicon oxide (SiOx) applied as a finish coating was investigated for further improvements. An in vitro encrustation system mimicking natural urine flow was used to quantify the formation of urinary stones. These stones were subsequently analyzed using Fourier transform infrared spectrometry (FTIR). Encrustation results were then discussed in relation to coating surface chemical properties. Parylene C and VT4 grades demonstrated a very low encrustation mass, making them attractive options for encrustation prevention. The best performance was achieved after the addition of a hydrophilic SiOx finish coating on parylene VT4 grade. Parylene-based encapsulation proved to be an outstanding solution to prevent encrustation for urological implants.

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.

Urinary Stent Development and Evaluation Models: In Vitro, Ex Vivo and In Vivo-A European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS) Initiative.

Background: When trying to modify urinary stents, certain pre-clinical steps have to be followed before clinical evaluation in humans. Usually, the process starts as an in silico assessment. The urinary tract is a highly complex, dynamic and variable environment, which makes a computer simulation closely reflecting physiological conditions extremely challenging. Therefore, the pre-clinical evaluation needs to go through further steps of in vitro, ex vivo and in vivo assessments. Methods and materials: Within the European Network of Multidisciplinary Research to Improve Urinary Stents (ENIUS), the authors summarized and evaluated stent assessment models in silico, in vitro, ex vivo and in vivo. The topic and relevant sub-topics were researched in a systematic literature search in Embase, Scope, Web of Science and PubMed. Clinicaltrials.gov was consulted for ongoing trials. Articles were selected systematically according to guidelines with non-relevant, non-complete, and non-English or Spanish language articles excluded. Results: In the first part of this paper, we critically evaluate in vitro stent assessment models used over the last five decades, outlining briefly their strengths and weaknesses. In the second part, we provide a step-by-step guide on what to consider when setting up an ex vivo model for stent evaluation on the example of a biodegradable stent. Lastly, the third part lists and discusses the pros and cons of available animal models for urinary stent evaluation, this being the final step before human trials. Conclusions: We hope that this overview can provide a practical guide and a critical discussion of the experimental pre-clinical evaluation steps needed, which will help interested readers in choosing the right methodology from the start of a stent evaluation process once an in silico assessment has been completed. Only a transparent multidisciplinary approach using the correct methodology will lead to a successful clinical implementation of any new or modified stent.

Potential strategies to prevent encrustations on urinary stents and catheters - thinking outside the box: a European network of multidisciplinary research to improve urinary stents (ENIUS) initiative.

Introduction: Urinary stents have been around for the last 4 decades, urinary catheters even longer. They are associated with infections, encrustation, migration, and patient discomfort. Research efforts to improve them have shifted onto molecular and cellular levels. ENIUS brought together translational scientists to improve urinary implants and reduce morbidity.Methods & materials: A working group within the ENIUS network was tasked with assessing future research lines for the improvement of urinary implants.Topics were researched systematically using Embase and PubMed databases. Clinicaltrials.gov was consulted for ongoing trials.Areas covered: Relevant topics were coatings with antibodies, enzymes, biomimetics, bioactive nano-coats, antisense molecules, and engineered tissue. Further, pH sensors, biodegradable metals, bactericidal bacteriophages, nonpathogenic uropathogens, enhanced ureteric peristalsis, electrical charges, and ultrasound to prevent stent encrustations were addressed.Expert opinion: All research lines addressed in this paper seem viable and promising. Some of them have been around for decades but are yet to proceed to clinical application (i.e. tissue engineering). Others are very recent and, at least in urology, still only conceptual (i.e. antisense molecules). Perhaps the most important learning point resulting from this pan-European multidisciplinary effort is that collaboration between all stakeholders is not only fruitful but also truly essential.

Prevention of Encrustation on Ureteral Stents: Which Surface Parameters Provide Guidance for the Development of Novel Stent Materials?

Encrustations of ureteral stents are one of the biggest problems with urological implants. Crystalline biofilms can occur alone or in combination with bacterial biofilms. To identify which surface parameters provide guidance for the development of novel stent materials, we used an in vitro encrustation system. Synthetic urine with increasing pH to simulate an infection situation was pumped over the polymer samples with adjusted flow rates at 37 °C to mimic the native body urine flow. Chemical surface features (contact angle, surface charge), as well as encrustations were characterized. The encrustations on the materials were analyzed quantitatively (dry mass) and qualitatively using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR). The aim of this comparative study was to identify crucial surface parameters that might predict the quantity and type of mineral deposits in vitro and provide guidance for the development and screening of new polymer-based biomaterials for ureteral stent design. For the first time, we could identify that, within the range of our polymers, those materials with a slight hydrophilicity and a strong negative zeta potential (around -60 mV) were most favorable for use as ureteral stent materials, as the deposition of crystalline biofilms was minimized.

Upper Urinary Tract Tumors: Which Diagnostic Methods Are Needed?

OBJECTIVES: We reviewed the data of patients with upper urinary tract (UUT) tumors to evaluate the effectiveness of diagnostic procedures. METHODS: This retrospective study evaluated tumor characteristics, imaging procedures, epidemiological and follow-up data of 113 patients. We analyzed the importance of non-invasive and endoscopic diagnosis in addition to imaging as well as the influence of stage and grade on recurrence rate. RESULTS: Most tumors were urothelial carcinomas (92.9%). The cardinal symptoms were hematuria (40.7%), flank pain (2.7%), and urinary obstruction (14.2%). Forty-seven patients received intravenous urograms (IVUs), 57 retrograde ureteropyelography (RUP), 89 CTs, 6 an MRI. The correct positive tumor identification was reached by IVU in 27/47 patients, by RUP in 50/57, by CT in 74/89, and by MRI in 3/6 patients representing sensitivities of 57.4% (IVU), 87.7% (RUP), 83.1% (CT), and 50% (MRI). Sixty-four patients had urine cytology, which was correctly positive in 60.9% and 56 had a diagnostic ureterorenoscopy, which was correctly positive in 83.9%. During follow-up more than 20% of patients developed a recurrence. CONCLUSION: In patients with hematuria and flank pain, UUT must be considered a differential diagnosis. UUT to the extent of 76.6% showed more invasive growth (>Ta). Thus, rapid and efficient diagnosis based primarily on imaging is required. Contrast CT scan seems to be the imaging modality with the best performance. However, often only a combination of diagnostic procedures gives a certain diagnosis. Due to the high recurrence rate, close follow-up is needed.

Ureteral stent encrustation. Pathophysiology / Incrustacion de cateteres ureterales. Fisiopatología

Ureteral stents are the most commonly used urological implants. They are used for temporary as well as for long-term ureteral stenting. Amongst others, complications of ureteral stenting are encrustation and cellular adherence which, in turn, promotes urinary tract infection and can induce impaired healing in case of ureteral damage. Biofilm formation on urological implants leads to the protection of persisting bacteria from local defense mechanisms, thereby rendering persistent urinary tract infections more common. It seems clear that antibiotics cannot penetrate into biofilms adequately. Also, bacteria persist in biofilms in a state of reduced metabolism which further reduces antibiotic efficacy. Furthermore, bacteria develop resistance more quickly in biofilms. This paper tries to give an overview of the complex pathophysiological mechanisms that underlie stent encrustation as far as we know to date

Los catéteres ureterales son los implantes urológicos más utilizados. Se utilizan de forma temporal o a largo plazo. Entre otras complicaciones la utilización de catéteres ureterales incluye la incrustación y la adherencia celular que a su vez promueven la infección del tracto urinario y pueden empeorar la cicatrización en caso de lesión ureteral. La formación de biofilms en los implantes urológicos conlleva la protección de las bacterias persistentes de los mecanismos de defensa locales, haciendo de ese modo mas común la infección urinaria. Parece claro que los antibióticos no pueden penetrar adecuadamente en los biofilms. Además, las bacterias en los biofilms persisten en un estado de metabolismo reducido que disminuye más aún la eficacia de los antibióticos. Asimismo, las bacterias en los biofilms desarrollan resistencias más rápido. Este artículo intenta ofrecer una visión de conjunto sobre los mecanismos fisiopatológicos complejos que subyacen a la incrustación de catéteres hasta donde se conoce hoy en día

Development of a rat model for investigation of experimental splinted uretero-ureterostomy, ureteral stenting and stenosis.

BACKGROUND AND AIM: The objective of this study was to establish a rat model to develop hypertrophic fibrosis for subsequent safe application of ureteral stents in order to investigate new treatment options for ureteral strictures. MATERIALS AND METHODS: Thirty-two male Sprague-Dawley rats were used. Group 1: Sham surgery; group 2: surgery with uretero-ureteral anastomosis and stenting. Histopathological evaluation was carried out using 5-bromo-2-deoxyuridine administration before the animals were sacrificed. RESULTS: A total of thirty-one animals reached the final end-point. The most common surgical complications were urine extravasation and stent dislocations. Histological examination showed full regeneration of urothelium after 28 days and development of a scarring process. With stent insertion, moderate hypertrophia was seen. In contrast, the sham group had no evidence of significant scarring or stricture formations. CONCLUSION: Our rat model allows for investigation of the wound healing processes of urothelium of the ureteral wall and the study of the application of new miniature stents as drainage and drug carriers.