Polyethyleneimine brushes effectively inhibit encrustation on polyurethane ureteral stents both in dynamic bioreactor and in vivo

In vitro and in vivo study of antibacterial and anti-encrustation coating on ureteric stents

OBJECTIVES

To investigate the ability of propolis-coated ureteric stents to solve complications, especially urinary tract infections (UTIs) and crusting, in patients with long-term indwelling ureteric stents through antimicrobial and anti-calculus activities.

MATERIALS AND METHODS

Polyurethane (PU) ureteric stents were immersed in the ethanol extract of propolis (EEP), a well-known antimicrobial honeybee product, and subjected to chemical, hydrophilic, and seismic tests. The antimicrobial activity of the EEP coating was then examined by in vitro investigation. Proteus mirabilis infection was induced in rats within uncoated and EEP-coated groups, and the infection, stone formation, and inflammation were monitored at various time points.

RESULTS

The characterisation results showed that the hydrophilicity and stability of the EEP surface improved. In vitro tests revealed that the EEP coating was biocompatible, could eliminate >90% of bacteria biofilms attached to the stent and could maintain bacteriostatic properties for up to 3 months. The in vivo experiment revealed that the EEP-coating significantly reduced the amount of bacteria, stones, and salt deposits on the surface of the ureteric stents and decreased inflammation in the host tissue.

CONCLUSIONS

Compared with clinically used PU stents, EEP-coated ureteric stents could better mitigate infections and prevent encrustation. Thus, this study demonstrated that propolis is a promising natural dressing material for ureteric stents.

Surface Modification of Zn-Cu Alloy with Heparin Nanoparticles for Urinary Implant Applications

In this work, an investigation on the Zn-Cu alloy coated with heparin was conducted in order to explore the potentiality of its application as a feasible alternative for biodegradable implants, with the specific goal of addressing the issue of encrustation in the urinary system. The stability of the nanoparticles were characterized by dynamic light scattering. Typical surface characterization such as X-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy were used to demonstrate a successful immobilization of the NPs. The in vitro corrosion behavior was studied by potentiodynamic polarization and immersion tests in artificial urine (AU) at 37 °C. The 8 weeks in vivo degradation, encrustation resistance, hemocompatibility, and histocompatibility were investigated by means of implantation into the bladders of rats. Both in vitro and in vivo degradation tests exhibited a higher degradation rate for Zn-Cu and NPs groups when compared to pure Zn. Histological evaluations and hemocompatibility revealed that there was no tissue damage or pathological alterations caused by the degradation process. Furthermore, antiencrustation performance and urinalysis results confirmed that the modified alloy demonstrated significant encrustation inhibitory properties and bactericidal activity compared to the pure Zn control. Our findings highlight the potential of this modified alloy as an antiencrustation biodegradable ureteral stent.

Size-Controlled Ammonium-Based Homopolymers as Broad-Spectrum Antibacterials

Ammonium group containing polymers possess inherent antimicrobial properties, effectively eliminating or preventing infections caused by harmful microorganisms. Here, homopolymers based on monomers containing ammonium groups were synthesized via Reversible Addition Fragmentation Chain Transfer Polymerization (RAFT) and evaluated as potential antibacterial agents. The antimicrobial activity was evaluated against Gram-positive (M. luteus and B. subtilis) and Gram-negative bacteria (E. coli and S. typhimurium). Three polymers, poly(diallyl dimethyl ammonium chloride), poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), and poly(vinyl benzyl trimethylammonium chloride), were examined to explore the effect of molecular weight (10 kDa, 20 kDa, and 40 kDa) on their antimicrobial activity and toxicity to mammalian cells. The mechanisms of action of the polymers were investigated with dye-based assays, while Scanning Electron Microscopy (SEM) showed collapsed and fused bacterial morphologies due to the interactions between the polymers and components of the bacterial cell envelope, with some polymers proving to be bactericidal and others bacteriostatic, while being non-hemolytic. Among all the homopolymers, the most active, non-Gram-specific polymer was poly([2-(methacryloyloxy)ethyl]trimethylammonium chloride), with a molecular weight of 40 kDa, with minimum inhibitory concentrations between 16 and 64 µg/mL, showing a bactericidal mode of action mediated by disruption of the cytoplasmic membrane. This homopolymer could be useful in biomedical applications such as surface dressings and in areas such as eye infections.

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.

Polymers showing intrinsic antimicrobial activity

Pathogenic microorganisms are considered to a major threat to human health, impinging on multiple sectors including hospitals, dentistry, food storage and packaging, and water contamination. Due to the increasing levels of antimicrobial resistance shown by pathogens, often caused by long-term abuse or overuse of traditional antimicrobial drugs, new approaches and solutions are necessary. In this area, antimicrobial polymers are a viable solution to combat a variety of pathogens in a number of contexts. Indeed, polymers with intrinsic antimicrobial activities have long been an intriguing research area, in part, due to their widespread natural abundance in materials such as chitin, chitosan, carrageen, pectin, and the fact that they can be tethered to surfaces without losing their antimicrobial activities. In addition, since the discovery of the strong antimicrobial activity of some synthetic polymers, much work has focused on revealing the most effective structural elements that give rise to optimal antimicrobial properties. This has often been synthesis targeted, with the generation of either new polymers or the modification of natural antimicrobial polymers with the addition of antimicrobial enhancing modalities such as quaternary ammonium or guanidinium groups. In this review, the growing number of polymers showing intrinsic antimicrobial properties from the past decade are highlighted in terms of synthesis; often based on post-synthesis modification and their utilization. This includes as surface coatings, for example on medical devices, such as intravascular catheters, orthopaedic implants and contact lenses, or directly as antibacterial agents (specifically as eye drops). Surface functionalisation with inherently antimicrobial polymers is highlighted and has been achieved via various techniques, including surface-bound initiators allowing RAFT or ATRP surface-based polymerization, or via physical immobilization such as by layer-by-layer techniques. This article also covers the mechanistic modes of action of intrinsic antimicrobial polymers against bacteria, viruses, or fungi.

Contact-Active Layer-by-Layer Grafted TPU/PDMS Blends as an Antiencrustation and Antibacterial Platform for Next-Generation Urological Biomaterials: Validation in Artificial and Human Urine

Urinary tract infections and urinary encrustation impede the long-term clinical performance of urological implants and medical devices. Together, biofilm formation and encrustation constitute serious complications, driving the development of next-generation urological biomaterials. The currently available bioengineered solutions have limited success during long-term usage in the urinary environment. In addressing this unmet clinical challenge, contact-active, antiencrustation surface grafting were conceived onto a dynamically cross-linked polydimethylsiloxane (PDMS) modified thermoplastic polyurethane (TPU) blend using the layer-by-layer (LbL) assembly route. To the best of the authors' knowledge, the present study is the first to investigate the LbL grafting in developing an antiencrustation platform. These multilayered assemblies strategically employed covalent cross-linking and electrostatic interaction-assisted progressive depositions of branched polyethyleneimine and poly(2-ethyl-2-oxazoline). While polyethyleneimine conferred the contact-killing bactericidal activity, the much-coveted antiencrustation properties were rendered by incorporating a partially hydrolyzed derivative of poly(2-ethyl-2-oxazoline). The performance of the resultant surface-modified TPU/PDMS blends was benchmarked against the conventional urological alloplasts, in a customized lab-scale bioreactor-based dynamic encrustation study and in human urine. After 6 weeks of exposure to an artificial urine medium, simulating urease-positive bacterial infection, the surface-modified blends exhibited a remarkable ability to suppress Ca and Mg encrustation. In addition, these blends also displayed superior grafting stability and antibacterial efficacy against common uropathogens. As high as 4-fold log reduction in the planktonic growth of Gram-negative P. mirabilis and Gram-positive MRSA was recorded with the LbL platform vis-à-vis medical-grade TPU. In conjunction, the in vitro cellular assessment with human keratinocytes (HaCaT) and human embryonic kidney cells (HEK) established the uncompromised cytocompatibility of the multilayered grafted blends. Finally, the physiologically relevant functionality of the LbL grafting has been validated using clinical samples of human urine collected from 129 patients with a broad spectrum of disease conditions. The phase-I pre-clinical study, entailing 6 week-long incubation in human urine, demonstrated significantly improved encrustation resistance of the blends. The collective findings of the present work clearly establish the success of LbL strategies in the development of stable, multifunctional new-generation urological biomaterials.

Mussel-Inspired Clickable Antibacterial Peptide Coating on Ureteral Stents for Encrustation Prevention

Long-term indwelling catheters or stents often cause complications like infection, encrustation, hematuria, pain, and so on. The source of these problems is bacteria, which can form biofilms on the stents to reduce antibiotic sensitivity and produce urease to form encrustation by increasing the urine pH. Urinary tract infection (UTI) can aggravate the body damage and even seriously endanger lives, and the encrustation will block the stents, which can cause hydronephrosis and renal function damage. Therefore, the prevention of UTI and encrustation represents a great challenge in clinical ureteral stent uses. In this work, a clickable mussel-inspired peptide and antimicrobial peptide (AMP) were used to functionalize the commercial stents' surfaces to inhibit long-term infection and encrustation caused by bacteria. Copper (Cu) ions were used to coordinate the mussel-inspired peptide to improve the stability. The AMP with an azido group was clicked to the mussel-inspired Cu-coordinated peptide coating through click chemistry. The bio-inspired antibacterial coating was constructed with excellent stability, bactericidal properties, and improved biological compatibility. In in vitro and in vivo experiments, it was further found that the coating showed bactericidal and encrustation reduction abilities. This study thus developed an effective, safe, and stable AMP coating on urinary stents/catheters capable of long-term antibacterial and encrustation inhibition.

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.

Biomaterials assisted reconstructive urology: The pursuit of an implantable bioengineered neo-urinary bladder

Urinary bladder is a dynamic organ performing complex physiological activities. Together with ureters and urethra, it forms the lower urinary tract that facilitates urine collection, low-pressure storage, and volitional voiding. However, pathological disorders are often liable to cause irreversible damage and compromise the normal functionality of the bladder, necessitating surgical intervention for a reconstructive procedure. Non-urinary autologous grafts, primarily derived from gastrointestinal tract, have long been the gold standard in clinics to augment or to replace the diseased bladder tissue. Unfortunately, such treatment strategy is commonly associated with several clinical complications. In absence of an optimal autologous therapy, a biomaterial based bioengineered platform is an attractive prospect revolutionizing the modern urology. Predictably, extensive investigative research has been carried out in pursuit of better urological biomaterials, that overcome the limitations of conventional gastrointestinal graft. Against the above backdrop, this review aims to provide a comprehensive and one-stop update on different biomaterial-based strategies that have been proposed and explored over the past 60 years to restore the dynamic function of the otherwise dysfunctional bladder tissue. Broadly, two unique perspectives of bladder tissue engineering and total alloplastic bladder replacement are critically discussed in terms of their status and progress. While the former is pivoted on scaffold mediated regenerative medicine; in contrast, the latter is directed towards the development of a biostable bladder prosthesis. Together, these routes share a common aspiration of designing and creating a functional equivalent of the bladder wall, albeit, using fundamentally different aspects of biocompatibility and clinical needs. Therefore, an attempt has been made to systematically analyze and summarize the evolution of various classes as well as generations of polymeric biomaterials in urology. Considerable emphasis has been laid on explaining the bioengineering methodologies, pre-clinical and clinical outcomes. Some of the unaddressed challenges, including vascularization, innervation, hollow 3D prototype fabrication and urinary encrustation, have been highlighted that currently delay the successful commercial translation. More importantly, the rapidly evolving and expanding concepts of bioelectronic medicine are discussed to inspire future research efforts towards the further advancement of the field. At the closure, crucial insights are provided to forge the biomaterial assisted reconstruction as a long-term therapeutic strategy in urological practice for patients' care.

Cationic Alternating Polypeptide Fixed on Polyurethane at Multiple Sites for Excellent Antibacterial and Antifouling Properties

Bacterial infection and blockage are severe problems for polyurethane (PU) catheters and there is an urgent demand for surface-functionalized polyurethane. Herein, a cationic alternating copolymer comprising allyl-substituted ornithine and glycine (allyl-substituted poly(Orn-alter-Gly)) with abundant carbon-carbon double bond functional groups (C═C) is designed. Polyurethane is prepared with a large quantity of C═C groups (PU-D), and different amounts of allyl-substituted poly(Orn-alter-Gly) are grafted onto the PU-D surface (PU-D-2%AMPs and PU-D-20%AMPs) via the C═C functional groups. The chemical structures of the allyl-substituted poly(Orn-alter-Gly) and polyurethane samples (PU, PU-D, PU-D-2%AMPs, and PU-D-20%AMPs) are characterized and the results reveal that allyl-substituted poly(Orn-alter-Gly) is decorated on the polyurethane. PU-D-20%AMPs shows excellent antibacterial activity against Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus because of the high surface potential caused by cationic allyl-substituted poly(Orn-alter-Gly), and it also exhibits excellent long-term antibacterial activity and antibiofilm properties. PU-D-20%AMPs also has excellent antifouling properties because the cationic copolymer is fixed at multiple reactive sites, thus avoiding the formation of movable long chain brush. A strong surface hydration barrier is also formed to prevent adsorption of proteins and ions, and in vivo experiments reveal excellent biocompatibility. This flexible strategy to prepare dual-functional polyurethane surfaces with antibacterial and antifouling properties has large potential in biomedical implants.

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.

Alleviating the toxicity concerns of antibacterial cinnamon-polycaprolactone biomaterials for healthcare-related biomedical applications

Fibrous constructs with incorporated cinnamon-extract have previously been shown to have potent antifungal abilities. The question remains to whether these constructs are useful in the prevention of bacterial infections in fiber form and what the antimicrobial effects means in terms of toxicity to the native physiological cells. In this work, cinnamon extract containing poly (ε-caprolactone) (PCL) fibers were successfully manufactured by pressurized gyration and had an average size of ∼2 μm. Cinnamon extract containing PCL fibers were tested against Escherichia coli, Staphylococcus aureus, Methicillin resistant staphylococcus aureus, and Enterococcus faecalis bacterial species to assess their antibacterial capacity; it was found that these fibers were able to reduce viable cell numbers of the bacterial species up to two orders of magnitude lower than the control group. The results of the antibacterial tests were assessed by scanning electron microscopy (SEM). The constructs were also tested under indirect MTT tests where they showed little to no toxicity, similar to the control groups. Additionally, cell viability fluorescent imaging displayed no significant toxicity issues with the fibers, even at their highest tested concentration. Here we present a viable method for the production the non-toxic and naturally abundant cinnamon extracted fibers for numerous biomedical applications.

Preparation and Antifouling Property of Polyurethane Film Modified by PHMG and HA Using Layer-by-Layer Assembly

To reduce the possibility of bacterial infection and implant-related complications, surface modification on polyurethane (PU) film is an ideal solution to endow hydrophobic PU with antibacterial and antifouling properties. In this work, a variety of polyhexamethylene guanidine/ hyaluronic acid (PHMG/HA) multilayer films were self-assembled layer-by-layer on PU films using polyanions, carboxyl-activated HA, and polycations PHMG by controlling the concentration of these polyelectrolytes as well as the number of layers self-assembled. Attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) spectra, water contact angle (WCA), and A Atomic force microscope (AFM) of PU and modified PU films were studied. Protein adsorption and bacterial adhesion as well as the cytotoxicity against L929 of the film on selected PU-(PHMG/HA)₅/5-5 were estimated. The results showed that PU-(PHMG/HA)₅/5-5 had the best hydrophilicity among all the prepared films, possessing the lowest level of protein adsorption. Meanwhile, this film showed efficient broad-spectrum antibacterial performance as well as significant resistance of bacterial adhesion of more than a 99.9% drop for the selected bacteria. Moreover, almost no influence on cell viability of L929 enhanced the biocompatibility of film. Therefore, the modified PU films with admirable protein absorption resistance, antimicrobial performance, and biocompatibility would have promising applications in biomedical aspect.

Dual-functional antibiofilm polymer composite for biodegradable medical devices

Urinary tract infections (UTI) represent one of the most common problem within the urological disorders, and it is mainly caused by biofilm formation which leads to bacterial infection. Anti-adhesion and antibacterial agents are two primary mechanisms to prevent biofilm formation; however, current strategies are insufficiently effective. In this study, we developed an effective antibiofilm biodegradable polymer with high biocompatibility. Here we embedded silver nanoparticles (AgNPs) in poly(glycerol sebacate) acrylate (PGSA) followed by superhydrophilic modification on the polymer surfaces. The modified surfaces were characterized using SEM, AFM and contact angle measurements. This anti-adhesive surface prevented the adhesion of E. coli and limited the biofilm coverage percentage to less than 3% in 24 h. In the in vitro degradation, the long-term antibiofilm performance was evaluated in Nowatzki-Stoodley artificial urine (NSAU). The surface modified AgNPs embedded PGSA (sPGSA-AgNPs) was able to effectively inhibit the formation of biofilm by reducing the biofilm coverage to less than 0.01%, and it also showed low cytotoxicity with human bladder carcinoma cell. With the effective antibiofilm, biocompatibility and biodegradability, it is possible to be applied in urological devices to ameliorate the situation of UTIs.

Photothermal-Irradiated Polyethyleneimine-Polypyrrole Nanopigment Film-Coated Polyethylene Fabrics for Infrared-Inspired with Pathogenic Evaluation

Influenza, pneumonia, and pathogenic infection of the respiratory system are boosted in cold environments. Low temperatures also result in vasoconstriction, restraint of blood flow, and decreased oxygen to the heart, and the risk of a heart attack would increase accordingly. The present face mask fabric fails to preserve its air-filtering function as its electrostatic function vanishes once exposed to water. Therefore, its filtering efficacy would be decreased meaningfully, making it nearly impracticable to reuse the disposable face masks. The urgent requirement for photothermal fabrics is also rising. Nanobased polyethyleneimine-polypyrrole nanopigments (NPP NPs) have been developed and have strong near-infrared spectrum absorption and exceptional photothermal convertible performance. Herein, the mask fabric used PE-fiber-constructed membrane (PEFM) was coated by the binding affinity of the cationic polyethyleneimine component of NPP NPs forming NPP NPs-PEFM. To the best of our knowledge, no study has investigated NPP NP-coated mask fabric to perform infrared red (solar or body) photothermal conversion efficacy to provide biocompatible warming, remotely photothermally captured antipathogen, and antivasoconstriction in vivo. This pioneering study showed that the developed NPP NPs-PEFM could be washable, reusable, breathable, biocompatible, and photothermal conversable for active eradication of pathogenic bacteria. Further, it possesses warming preservation and antivasoconstriction.

A new hydrophilic biodegradable ureteral stent restrain encrustation both in vitro and in vivo

Ureteral stents have been widely used as biomedical devices to treat some urological diseases for several decades. However, the encrustation complications hamper the long-time clinical use of the ureteral stents. In this work, a new type of biodegradable material for the ureteral stents, methoxypoly(ethylene glycol)-block-poly(L-lactide-ran-Ɛ-caprolactone) (mPEG-PLACL), is evaluated to overcome this problem. The results show that the hydrophilicity and degradation rate in artificial urine of mPEG-PLACL are both significantly increased. It is worth noting that the mPEG-PLACL shows a lower amount of encrustation after immersing the stents in the dynamic urinary extracorporeal circulation (DUEC) model for 7 days. In addition, 71% Ca and 92% Mg are inhibited in vivo by quantitative analysis. Pathological analysis exhibit that the mPEG-PLACL cause less diffuse mucosal hyperplasia after 7 weeks of implantation. All the results indicate that this new type of biodegradable material had an excellent potential for the ureteral stents in the future.

A preliminary study on the role of Bacteroides fragilis in stent encrustation

OBJECTIVE

To preliminarily study the characteristics of bacterial flora distribution in the urine of ureteral stent encrustation patients as well as the relation between Bacteroides and stent encrustation.

METHODS

Patients undergoing ureteral stenting were included in the study and divided into encrustation group and non-encrustation group based on the condition of stent encrustation. The urine of patients was collected to undergo 16s DNA test to compare the bacterial flora distribution characteristics of the two groups. The bacterial genus with highest abundance in the urine of encrustation group was used for animal experiment. A rat model with a foreign body in the bladder was created, in which the rats were injected with the aforesaid bacterial genus. A control group injected with normal saline was also formed. The incidence of foreign body tube encrustation between the two groups was compared.

RESULTS

The urine collected from the patients in encrustation group contained a variety of bacteria, while dominant bacteria genera included g_Lactobacillus (23.1%), g_Bacteroides (18.8%) and g_norank_Bacteroides (17.1%). While the urine from the non-encrustation group was less diverse in bacteria flora, as the major bacteria genera were g_Escherichia-Shigella (32.2%), g_Enterococcus (24.9%) and g_Pseudomonas (18.2%). Bacteroidetes in the encrustation group were significantly higher, therefore Bacteroides fragilis in this genus was adopted for animal experiment, resulting in a higher incidence of foreign body tube encrustation in the bladder among rats.

CONCLUSION

The present study enriches our knowledge about ureteral stent encrustation and reveals that the target regulation of urine bacteria is worth further research and clinical application.

Facile coating of urinary catheter with bio-inspired antibacterial coating

Formation of bacterial biofilm on indwelling urinary catheters usually causes catheter-associated urinary tract infections (CAUTIs) that represent high percent of nosocomial infections worldwide. Therefore, coating urinary catheter with antibacterial and antifouling coating using facile technique is in great demand. In this study, commercial urinary catheter was coated with a layer of the self-polymerized polydopamine which acts as active platform for the in situ formation of silver nanoparticle (AgNPs) on catheter surface. The formed coating was intensively characterized using spectroscopic and microscopic techniques. The coated catheter has the potential to release silver ion in a sustained manner with a concentration of about 2-4 μg ml-1. Disk diffusion test and colony forming unites assay verified the significant bactericidal potential of the AgNPs coated catheter against both gram-positive and gram-negative bacteria as a consequence of silver ion release. In contrast to commercial catheter, the AgNPs coated catheter prevented the adherence of bacterial cells and biofilm formation on their surfaces. Interestingly, scanning electron microscope investigations showed that AgNPs coated catheter possess greater antifouling potential against gram-positive bacteria than against gram-negative bacteria. Overall, the remarkable antibacterial and antifouling potential of the coated catheter supported the use of such facile approach for coating of different medical devices for the prevention of nosocomial infections.

Current insights into the mechanisms and management of infection stones

Infection stones are complex aggregates of crystals amalgamated in an organic matrix that are strictly associated with urinary tract infections. The management of patients who form infection stones is challenging owing to the complexity of the calculi and high recurrence rates. The formation of infection stones is a multifactorial process that can be driven by urine chemistry, the urine microenvironment, the presence of modulator substances in urine, associations with bacteria, and the development of biofilms. Despite decades of investigation, the mechanisms of infection stone formation are still poorly understood. A mechanistic understanding of the formation and growth of infection stones - including the role of organics in the stone matrix, microorganisms, and biofilms in stone formation and their effect on stone characteristics - and the medical implications of these insights might be crucial for the development of improved treatments. Tools and approaches used in various disciplines (for example, engineering, chemistry, mineralogy, and microbiology) can be applied to further understand the microorganism-mineral interactions that lead to infection stone formation. Thus, the use of integrated multidisciplinary approaches is imperative to improve the diagnosis, prevention, and treatment of infection stones.

Evaluation of a ureteral catheter coating by means of a BioEncrustation in vitro model

Biomaterials for applications in the urinary tract are challenged with both biofilm formation and encrustation, two highly interconnected processes. While great effort has been achieved developing promising materials there is only a limited choice of sophisticated in vitro models that are available to analyse the performance of biomaterials prior to performing delicate and expensive in vivo studies. In this study we present a complex BioEncrustation model that imitates both the processes of multi-species biofilm formation and encrustation in vitro. The resulting crystalline biofilms are compared to the deposits found on explanted ureteral stent surfaces (in vivo situation) and to deposits formed in an experimental set up that does not contain bacteria (Encrustator®). Further focus of this study is dedicated to employing the developed BioEncrustation model to evaluate the effect multifunctional coatings impose on the processes of biofilm formation and encrustation under in vitro conditions. The investigated TANP coating combines unspecific and broad band specific antibacterial properties with a degrading polymer matrix that is intended to inhibit crystal formation. The coating was prepared on both polyurethane and silicone tubes and the subsequent results of the in vitro BioEncrustation analyses reveal a promising potential for employing the coating to render ureteral stent surfaces more biocompatible.

Biodegradation behavior of magnesium and ZK60 alloy in artificial urine and rat models

In this work, the biodegradable and histocompatibility properties of pure Mg and ZK60 alloy were investigated as new temporary implants for urinary applications. The corrosion mechanism in artificial urine was proposed using electrochemical impedance spectroscopy and potentiodynamic polarization tests. The corrosion potential of pure magnesium and ZK60 alloy were −1820 and −1561 mV, respectively, and the corrosion current densities were 59.66 ± 6.41 and 41.94 ± 0.53 μA cm⁻², respectively. The in vitro degradation rates for pure Mg and ZK60 alloy in artificial urine were 0.382 and 1.023 mm/y, respectively, determined from immersion tests. The ZK60 alloy degraded faster than the pure Mg in both artificial urine and in rat bladders (the implants of both samples are ø 3 mm × 5 mm). Histocompatibility evaluations showed good histocompatibility for the pure Mg and ZK60 alloy during the 3 weeks post-implantation in rat bladders, and no harm was observed in the bladder, liver and kidney tissues. The results provide key information on the degradation properties and corrosion mechanism of pure Mg and ZK60 alloy in the urinary system.

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ZK60 obtained loose corrosion product layer with poor corrosion resistance in AU.

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ZK60 showed a faster degradation rate than Mg in artificial urine and bladder of rat.

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Mg and ZK60 alloy showed good histocompatibility for the bladder model of rat.