Artificial Urine Solution Research Articles

Direct Contact Membrane Distillation of Artificial Urine and Its Application in Plasticizing Lunar Regolith

Direct Contact Membrane Distillation (DCMD) uses low heat sources to separate water from urea, which was then used as a plasticizer in regolith-based cement to make it more workable. The work investigated separating potable water and urea from artificial urine using DCMD and then characterizing the products. Water was successfully separated from the artificial urine solution as characterized by density, conductivity, pH, and substance concentrations. The concentrated urine solution was used in regolith-based cement cured under vacuum at temperatures that simulated temperatures that would be expected in construction on the Moon. Workability and other properties were improved by replacing water with concentrated urine solution in the mix.

Development of wearable textile-based moisture sensor for smart diaper applications and examination of its comfort properties

Urinary incontinence stands as a prevalent challenge encountered among elderly and sick individuals, necessitating the use of diapers for management. Despite existing systems that offer indicators for timely diaper changes upon wetness detection, there remains a demand for the development of wearable, facilely manufacturable, and unobtrusive solutions. Thus, this study presents the fabrication of wearable and flexible moisture sensors utilizing a pad printing technique employing silver and silver/nickel inks. Varied sintering processes with differing pass numbers were employed in sensor fabrication, subsequently subjecting them to evaluation for conductivity and surface morphology. Further, controlled applications of distilled water and artificial urine solutions were administered onto sensors integrated diapers to simulate urinary incontinence scenarios. When the sensors were exposed to the artificial urine solution, sensors’ resistance changes were more noticeable according to the water. Comparative analyses revealed that 5 pass silver sensor exhibited superior performance relative to other sensor configurations investigated. Ultimately, through physical testing, a comparative assessment between sensorless and sensor-integrated diapers was conducted, with findings indicating the promising potential of sensor-integrated diapers in enhancing user comfort and usability.

A novel near-infrared polymethine dye biosensor for rapid and selective detection of lithocholic acid

Lithocholic acid (LCA), a secondary bile acid, has emerged as a potential early diagnostic biomarker for various liver diseases. In this study, we introduce a novel near-infrared (NIR) polymethine dye-based biosensor, capable of sensitive and selective detection of LCA in phosphate buffer and artificial urine (AU) solutions. The detection mechanism relies on the formation of J-aggregates resulting from the interplay of 3,3-Diethylthiatricarbocyanine iodide (DiSC2(7)) dye molecules and LCA, which induces a distinctive red shift in both absorption and fluorescence spectra. The biosensor demonstrates a detection limit for LCA of 70 μM in PBS solution (pH 7.4), while in AU solution, it responds to an LCA concentration as low as ∼60 μM. Notably, the proposed biosensor exhibits outstanding selectivity for LCA, effectively distinguishing it from common interferents such as uric acid, ascorbic acid, and glucose. This rapid, straightforward, and cost-effective spectrometer-based method underscores its potential for early diagnosis of liver diseases by monitoring LCA concentrations.

Using urine FTIR spectra to screen autism spectrum disorder

Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder caused by multiple factors, lacking clear biomarkers. Diagnosing ASD still relies on behavioural and developmental signs and usually requires lengthy observation periods, all of which are demanding for both clinicians and parents. Although many studies have revealed valuable knowledge in this field, no clearly defined, practical, and widely acceptable diagnostic tool exists. In this study, 26 children with ASD (ASD+), aged 3–5 years, and 26 sex and age-matched controls are studied to investigate the diagnostic potential of the Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy. The urine FTIR spectrum results show a downward trend in the 3000–2600/cm region for ASD+ children when compared to the typically developing (TD) children of the same age. The average area of this region is 25% less in ASD+ level 3 children, 29% less in ASD+ level 2 children, and 16% less in ASD+ level 1 children compared to that of the TD children. Principal component analysis was applied to the two groups using the entire spectrum window and five peaks were identified for further analysis. The correlation between the peaks and natural urine components is validated by artificial urine solutions. Less-than-normal levels of uric acid, phosphate groups, and ammonium ({NH}_{4}^{+}) can be listed as probable causes. This study shows that ATR-FTIR can serve as a practical and non-invasive method to screen ASD using the high-frequency region of the urine spectrum.

Comparison of Ureteral Stent Biomaterials: Encrustation Profile in Lithogenic Artificial Urine Models.

Ureteral stent encrustation significantly limits indwelling time and can lead to downstream urological problems. However, no ideal polymeric biomaterials have been shown to completely resist encrustation in long-term urine exposure. Recently, 2-hydroxyethyl methacrylate (HEMA)-coated Pellethane was reported as a promising biomaterial resistant to encrustation. This study compared HEMA-coated Pellethane to commercially available stents under two different artificial urine environments. To evaluate the degree and composition of encrustation on HEMA-coated Pellethane, Boston Scientific Tria, Bard InLay Optima, Cook Universa Hydrogel, and Cook Black Silicone stents were used at various dwelling times in two different artificial urine environments. In a batch-flow model, samples of stents were suspended in an artificial urine solution (AUS) at 37 °C. Every 24 h for 11 weeks, 50% of the AUS would be replaced with fresh components using a programmable peristaltic pump system. The stent materials were removed at suitable time intervals and air-dried for 24 h under sterile conditions before follow-up analysis. SEM was used to assess the degree of encrustation, and inductively coupled plasma mass spectrometry (ICP-MS) was employed to quantify the encrusted compositions, specifically for calcium, magnesium, and phosphorus. We measured the weight gain over time due to encrusted deposits on the stents and quantified the amount of Ca, Mg, and P deposited on each encrusted stent. After the 11 week trial, HEMA-coated Pellethane showed the most average mass change. SEM showed that HEMA-coated Pellethane was fully encrusted in just 2 weeks in the AUS environments, and ICP-MS showed that Ca is the most abundant deposit. Among all the tested stents, Black Silicone performed the best. The two AUSs were formulated to encrust more rapidly than physiological conditions. HEMA-coated Pellethane is not an ideal stent material, while silicone is a promising material for advancing ureteral stents.

A comprehensive study on microstructure, in-vitro biodegradability, bacterial sensitivity, and cellular interactions of novel ternary Zn-Cu-xAg alloys for urological applications

Novel ternary Zn-Cu-xAg alloys are designed and fabricated by the casting method under a vacuum atmosphere and then homogenized at 350 °C for 15 h. The effect of Ag concentration (x: 0, 1, 2, 3, and 4 wt%) on microstructure, hardness, in vitro corrosion, biodegradability, and bacterial sensitivity was studied systematically. The structural analysis of the alloys was investigated by using a scanning electron microscope (SEM-EDS), and an optical microscope (OM). Besides, phase characterization of the samples was conducted using X-ray diffraction (XRD). The degradation behaviors of the alloys were determined under in vitro conditions, electrochemical polarization, and immersion tests (up to 21 days) in artificial urine (AU) solution. The maximum hardness value for Zn-1Cu-4Ag alloy was about 2.38 times higher than pure Zn due to solid-solution strengthening and precipitation hardening of (Ag, Cu)Zn4 phases. The highest and lowest Icorr values, reference also corrosion rate, were calculated in Zn-1Cu and Zn-1Cu-3Ag alloys as 17.13 and 1.318 mA·cm−2, respectively. The alloys' bacterial sensitivities were evaluated with the disc diffusion test for E. coli and S. aureus. The inhibition ratio of the Zn-1Cu-1Ag was higher than the inhibition rates of the other alloys on E. coli and S. aureus. In addition, the biological properties of the generated material were promising by altering cell survival/death ratio in both prostate epithelial and bladder cancer cells related to their use potential in urology.

Action of Urine on Stone-Built Heritage

Due to its resistance and durability, stone is the material most used in construction by humanity. The aim of this study was to investigate the action of urine on granites. Accelerated alteration tests were performed on Grey Itaquera, Pink Itupeva, and Black Piracaia granites – stones from the São Paulo State, Brazil, which were widely used in the historical built heritage of the São Paulo state. The test was performed with 30 cycles of partial immersion of nine samples in artificial urine solution and the sanitising of the specimens, totalling 60 consecutive days of testing. In the first 24 hours, the samples were partially immersed in urine; in the following 24 hours, the samples were sanitised in three different groups: A) without washing; B) washing with natural water; C) washing with a 5:1 solution of natural water with bleach. The alterations induced in the specimens were evaluated by spectrophotometry, P-wave velocity, and scanning electron microscopy. The main results obtained were chromatic alterations and crystallisation of salts on the three types of granite. The study concluded that urine is a substance that can cause moderate alterations in the aesthetics and structure of granitic stones.

Evaluation of absorbent sheet to prevent anticancer drugs contamination spread in urine

Medically, anticancer drugs contamination leading to human exposure has become an issue. The urine of patients receiving chemotherapy contains anticancer drugs. If urine containing anticancer drugs is excreted, the anticancer drugs are scattered around the toilet bowl, then adhere to slipper soles and spread. Therefore, we developed an absorbent sheet containing activated carbon that absorbs anticancer drugs and prevents anticancer drug contamination spread. In this article, we report the data on the sheet performance evaluation. In artificial urine solutions, 100 μL (20 drops) of cyclophosphamide (CPA; 2,000 μg/mL), methotrexate (MTX; 6,000 μg/mL), and paclitaxel (PTX; 200 μg/mL) were dropped onto the stainless plate of two commercially available medical sheets (Pitapa SheetⓇ; control product 1 and Absocare sheetⓇ; control product 2) and a newly developed sheet (HD Safe Sheet-Neo, test product). Polyvinyl chloride (PVC) slippers were placed on the sheets for 30 s, and anticancer drugs that adhered to the slippers were quantified. We compared the drug quantities that were transferred to the slippers from different sheets. An average of 31.5%, 38.7%, and 50.5% of each of the dropped anticancer agents (CPA, MTX, and PTX, respectively) adhered to the slipper sole. Compared to that of the control product 2, the average adhesion of CPA and MTX was significantly reduced in the test product containing activated charcoal (224 vs 2 μg, p < .050 and 2,235 vs 19 μg, p < .050). Contrastingly, there was no significant difference in the PTX mean adherence (35 vs 13 μg). Activated carbon adsorbs anticancer drugs in urine. The test product containing activated charcoal reduced the amount of scattered anticancer drugs that adhered to the slippers. The results suggest that the activated carbon sheet may prevent anticancer drugs contamination spread in urine.

Quantitative and rapid detection of iodide ion via electrolyte-gated IGZO thin-film transistors

In this study, rapid-detection iodide ion sensors based on sol-gel indium-gallium-zinc-oxide electrolyte gated thin-film transistors (IGZO-EGTFTs) have been examined. With a high electrical-double-layer capacitance (6.2 μF/cm2) at the interface between IGZO channel and physiological fluid (i.e., phosphate-buffered saline and artificial urine solution), the EGTFTs can be operated under 0.5 V with a high ON and OFF state current ratio above 108, and transconductance value of 1.14 mS. In addition to excellent electrical characteristics, the novel electrochemical reaction of IGZO-EGTFTs enables high selectivity and linear response over a wide detection range of iodide ions concentration (from 1 to 104 μM), the limit of detection as low as 1 μM, and response time below 0.1 s. The mechanism of iodide ions detection of IGZO-EGTFT was investigated based on electrochemical impedance spectroscopy analysis. We expect that IGZO-EGTFTs will contribute to the development of point-of-care rapid and reusable ion-sensors for human urine and serum.

Corrosion behavior of Mg wires for ureteral stent in artificial urine solution

Ureteral stents are a relatively new potential application for biodegradable Mg alloys. In this study, the corrosion behavior of Mg-1Zn wires and pure Mg wires in artificial urine solution (AUS) is investigated. It is found that AUS possesses a strong pH buffer effect. Hydrogen evolution measurement cannot be used for Mg corrosion test in this AUS due to the oxygen scavenging effect of sulfite, which is a component of AUS. The corrosion products consist of two layers, MgNH4PO4·6H2O and Mg(OH)2. The partially protective MgNH4PO4·6H2O slows down the Mg corrosion, but it indicates the encrustation risk on bare Mg-based ureteral stents.

Water Pollutants p-Cresol Detection Based on Au-ZnO Nanoparticles Modified Tapered Optical Fiber.

In this work, a localized plasmon-based sensor is developed for para-cresol (p-cresol) - a water pollutant detection. A nonadiabatic [Formula: see text] of tapered optical fiber (TOF) has been experimentally fabricated and computationally analyzed using beam propagation method. For optimization of sensor's performance, two probes are proposed, where probe 1 is immobilized with gold nanoparticles (AuNPs) and probe 2 is immobilized with the AuNPs along with zinc oxide nanoparticles (ZnO-NPs). The synthesized metal nanomaterials were characterized by ultraviolet-visible spectrophotometer (UV-vis spectrophotometer) and transmission electron microscope (HR-TEM). The nanomaterials coating on the surface of the sensing probe were characterized by a scanning electron microscope (SEM). Thereafter, to increase the specificity of the sensor, the probes are functionalized with tyrosinase enzyme. Different solutions of p-cresol in the concentration range of [Formula: see text] - [Formula: see text] are prepared in an artificial urine solution for sensing purposes. Different analytes such as uric acid, β -cyclodextrin, L-alanine, and glycine are prepared for selectivity measurement. The linearity range, sensitivity, and limit of detection (LOD) of probe 1 are [Formula: see text] - [Formula: see text], 7.2 nm/mM (accuracy 0.977), and [Formula: see text], respectively; and for probe 2 are [Formula: see text] - [Formula: see text], 5.6 nm/mM (accuracy 0.981), and [Formula: see text], respectively. Thus, the overall performance of probe 2 is quite better due to the inclusion of ZnO-NPs that increase the biocompatibility of sensor probe. The proposed sensor structure has potential applications in the food industry and clinical medicine.

Evaluation of a novel biodegradable ureteral stent produced from polyurethane and magnesium alloys.

Indwelling ureteral stents represent a very frequently used procedure in urological clinical practice that ensures the drainage of urine from the upper urinary tract. However, the stents could result in many stent-associated complications, such as encrustation and patient discomfort. We developed a new type of biodegradable ureteral stents produced from degradable polyurethane and magnesium alloys. In the present study, we investigated the biocompatibility and the property of degradation of the biodegradable ureteral stents. We evaluated the cytotoxicity of biodegradable ureteral stent by the MTT assay in vitro. The rabbit dorsal muscle embedding test was used to assess the biocompatibility of the degradable stents. Inflammation and fibrosis of muscle tissue were noted to evaluate compatibility at 1, 2, 4, 6 weeks after stents implanted in muscle. The degradation of the biodegradable ureteral stents was assessed by measuring the weight loss of the samples in AUS (artificial urine solution). For validating the degradation property of degradable stents in vivo, we inserted a degradable stent or a conventional biostable stent into Bama pigs. Furthermore, blood studies, liver function tests, renal function tests, urine studies, and computerized tomography (CT) were performed postoperatively. Our study confirms that the degradable polyurethane-based biodegradable ureteral stent has good biocompatibility. Our biodegradable ureteral stents were completely degraded within 4 weeks and provided a better ability of drainage than conventional stents. They hold promise for decreasing the need for a secondary procedure and stent related morbidity, such as infections.

Role of Au incorporation in the electrochemical behavior of Ag/a:C nanocomposite coatings

This work aims to study the electrochemical and the corrosion resistance of amorphous carbon coatings with metallic (Ag) and bimetallic (AgAu) nanoparticles deposited on stainless steel 316L by dc magnetron sputtering technique. These coatings were designed to coat ureteral stents and, accordingly, the Ag release measurement, morphological and electrochemical investigations were performed on the coatings immersed into artificial urine solution during 14 days to imitate the ureter electrolyte (urine) where the stents are inserted. These coatings are intended for insertion into the human body; then, in addition to the biocompatibility, they should not corrode since the resulting products can cause different adverse reactions.The Ag release study showed that the concentration of Ag+ release from the Ag-doped coating is much higher than the AgAu one over the measured time. Moreover, scanning electron microscopy analysis on the immersed and non-immersed coatings supported the Ag ion release assessment. From STEM analysis, the formation of AgAu nanoalloys in a wide size distribution was confirmed. Additionally, the electrochemical characteristics and corrosion resistance behavior of the coatings were investigated in artificial urine solution over immersion time by electrochemical impedance spectroscopy. The Nyquist plots were successfully fitted with a proper equivalent circuit based on a two-layer model representing a porous outer layer and a barrier inner layer for the coatings. The electrochemical measurements revealed that the coating doped with AgAu nanoparticles has improved corrosion resistance and less porosity compared to the Ag-doped one. The enhanced protective feature of the Ag-Au/a:C coatings can be attributed to the formation of AgAu nanoalloys that helps to block the solution penetration into the substrate.

Surface-Treated Pellethanes: Comparative Quantification of Encrustation in Artificial Urine Solution

Introduction: Encrustation of implanted urinary tract devices is associated with significant morbidity. Pellethane® is a polyether-based compound noted for its strength, porosity, and resistance to solvents. We assessed Pellethane thermoplastic polyurethane (TPU) with and without surface coatings 2-hydroxyethyl methacrylate (HEMA) and tetraethylene glycol dimethyl ether (TETRA) for the potential to resist encrustation in an artificial urine environment. Materials and Methods: Samples of Pellethane TPU, HEMA Pellethane TPU, TETRA Pellethane TPU, and hydrogel-coated ureteral stent (Cook®) were suspended in a batch-flow model with an artificial urine solution (AUS). Every 48 hours for 90 days, 40% of the solution was replaced with fresh AUS. All samples were stored in a 37°C incubator. Subsequently, the samples were thoroughly dried for 48 hours before weighing. Scanning electron microscopy was used to assess the degree of encrustation. Nu-Attom Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine the precise compositions of the encrustation specifically with regard to calcium, magnesium, and phosphate. Results: At the conclusion of the 90-day trial, the samples were analyzed, and the average mass changes were as follows: stent 63.78%, uncoated Pellethane TPU 11.50%, HEMA-coated Pellethane TPU 2.90%, and TETRA-coated Pellethane TPU 0.60%. Pellethane TPU products, and specifically those coated with HEMA and TETRA, exhibited less average mass increase and a lesser propensity to form encrustation than the traditional urinary tract stent. The mass increases noted on coated Pellethane devices were primarily ionic, whereas that of the stent was not. Conclusion: Pellethane, particularly with an HEMA-based preventative coating, may serve as a favorable alternative to traditional urinary stent material, providing its improved resistance to encrustation.

Magnesium-Impregnated Biochar for the Removal of Total Phosphorous from Artificial Human Urine

Biochar has an alkaline and porous structure that could be a potential material for recycling phosphorous (P) from urine. Sawdust (SD) was pyrolyzed to produce sawdust biochar (SDB), and then impregnated with magnesium (Mg) to produce Mg-impregnated biochar (SDBM). Artificial human urine (AHU) solution was used for a batch sorption study, and various sorption parameters (i.e., sorbent/solution ratio, pH of AHU, and initial total P concentration of AHU) were optimized. The concentration of total P was measured using an inductively coupled plasma-optical emission spectroscopy (ICP-OES). The surface morphology and elemental analysis for SDB, SDBM and the struvite-loaded SDBM (SMSDB) were investigated using scanning electron spectroscopy-energy dispersive x-ray spectroscopy (SEM-EDX). The total P sorption capacity for SDBM (32755 mg/g) was higher than that of SDB (7782 mg/g) and SD (10682 mg/g). The optimum total P removal for SDBM (21.2%) was achieved at a sorbent/solution ratio of 0.06g/L at pH 9. Sorption of total P may have occurred on the heterogeneous surface of SDBM. The presence of struvite crystals indicates that phosphate was adsorbed and then precipitated on the surface of SDBM.

The influence of nitrogen concentration and precipitation on fertilizer production from urine using a trickling filter

Planetary habitation requires technology to maintain natural microbial processes, which make nutrients from biowaste available for plant cultivation. This study describes a 646 day experiment, in which trickling filters were monitored for their ability to mineralize nitrogen when loaded with artificial urine solutions of different concentrations (40, 60, 80 and 100% v/v). Former studies have indicated that increasing urine concentrations slow nitrogen conversion rates and induce growing instability. In the current experiment, nitrogen conversion rates, measured as nitrate production/day, did not differ between concentration levels and increasing instability was not observed. Instead, the buffering capacity of the mussel shells added as buffer system (∼75% calcium carbonate) increased with increasing concentrations of synthetic urine possibly due to the higher phosphate content. The intensified precipitation of calcium phosphates seems to promote carbonate dissolution leading to improved buffering. For space applications, the precipitation of calcium phosphates is not desirable as for the phosphate to be available to the plants the precipitate must be treated with hazardous substances. With regard to terrestrial agriculture the process-integrated phosphate precipitation is a possibility to separate the macronutrients nitrogen and phosphate without addition of other chemicals. Thus, the described process offers a simple and cost-effective approach to fertilizer production from biogenic residues like slurry.

Green Tea and Struvite Crystals in Relation to Infectious Urinary Stones: The Role of (−)-Epicatechin

The influence of (−)-epicatechin, a component of green tea, on the nucleation and growth of struvite crystals, the main component of infectious urinary stones, is studied. The struvite crystallization process was performed in the solution of artificial urine, and the activity of urease−bacterial enzyme was simulated in a chemical way. The effect of the tested substance on the crystallization processes was monitored by spectrophotometric measurements and microscopic observations. The results obtained show that, in the presence of (−)-epicatechin, struvite nucleation occurs faster when compared with the control test. This means that its nucleation is shifted toward lower pH values. It has been also found that the presence of the tested substance can lead to an increase in the mass of struvite formed in artificial urine. The experimental results are explained on the basis of theoretical chemical speciation analysis of chemical complexes formed in artificial urine. This chemical speciation analysis demonstrat...

Short communication: Urea hydrolysis in dairy cattle manure under different temperature, urea, and pH conditions

The objective of the study was to quantify the rate of urea hydrolysis in dairy cattle manure under different initial urea concentration, temperature, and pH conditions. In particular, by varying all 3 factors simultaneously, the interactions between them could also be determined. Fresh feces and artificial urine solutions were combined into a slurry to characterize the rate of urea hydrolysis under 2 temperatures (15°C and 35°C), 3 urea concentrations in urine solutions (500, 1,000, and 1,500 mg of urea-N/dL), and 3 pH levels (6, 7, and 8). Urea N concentration in slurry was analyzed at 0.0167, 1, 2, 4, 6, 8, 12, 16, 20, and 24 h after initial mixing. A nonlinear mixed effects model was used to determine the effects of urea concentration, pH, and temperature treatments on the exponential rate of urea hydrolysis and to predict the hydrolysis rate for each treatment combination. We detected a significant interaction between pH and initial urea level. Increasing urea concentration from 1,000 to 1,500 mg of urea-N/dL decreased the rate of urea hydrolysis across all pH levels. Across all pH and initial urea levels, the rate of urea hydrolysis increased with temperature, but the effect of pH was only observed for pH 6 versus pH 8 at the intermediate initial urea concentration. The fast rates of urea hydrolysis indicate that urea was almost completely hydrolyzed within a few hours of urine mixing with feces. The estimated urea hydrolysis rates from this study are likely maximum rates because of the thorough mixing before each sampling. Although considerable mixing of feces and urine occurs on the barn floor of commercial dairy operations from cattle walking through the manure, such mixing may be not as quick and thorough as in this study. Consequently, the urea hydrolysis rates from this study indicate the maximum loss of urea and should be accounted for in management aimed at mitigating ammonia emissions from dairy cattle manure under similar urea concentration, pH, and temperature conditions reported in this experiment.

Drug-eluting biodegradable ureteral stent: New approach for urothelial tumors of upper urinary tract cancer

Upper urinary tract urothelial carcinoma (UTUC) accounts for 5–10% of urothelial carcinomas and is a disease that has not been widely studied as carcinoma of the bladder. To avoid the problems of conventional therapies, such as the need for frequent drug instillation due to poor drug retention, we developed a biodegradable ureteral stent (BUS) impregnated by supercritical fluid CO2 (scCO2) with the most commonly used anti-cancer drugs, namely paclitaxel, epirubicin, doxorubicin, and gemcitabine. The release kinetics of anti-cancer therapeutics from drug-eluting stents was measured in artificial urine solution (AUS). The in vitro release showed a faster release in the first 72h for the four anti-cancer drugs, after this time a plateau was achieved and finally the stent degraded after 9days. Regarding the amount of impregnated drugs by scCO2, gemcitabine showed the highest amount of loading (19.57μg drug/mg polymer: 2% loaded), while the lowest amount was obtained for paclitaxel (0.067μg drug/mg polymer: 0.01% loaded). A cancer cell line (T24) was exposed to graded concentrations (0.01–2000ng/ml) of each drugs for 4 and 72h to determine the sensitivities of the cells to each drug (IC50). The direct and indirect contact study of the anti-cancer biodegradable ureteral stents with the T24 and HUVEC cell lines confirmed the anti-tumoral effect of the BUS impregnated with the four anti-cancer drugs tested, reducing around 75% of the viability of the T24 cell line after 72h and demonstrating minimal cytotoxic effect on HUVECs.

Gelatin-based biodegradable ureteral stents with enhanced mechanical properties

A first generation of biodegradable ureteral stents based on natural origin polymers developed in a previous work has proven to be an interesting alternative to conventional stents, but it has however demonstrated to fail upon the first in vivo validation in a pig model. In this work, with the objective to overcome the low mechanical performance encountered and to make the biodegradable ureteral stents by origin polymers a success in vivo, four formulations with different concentrations of gelatin and alginate and different concentrations of crosslinking agent were tested in order to obtain higher mechanical properties. Bismuth was added to confer radiopaque properties to the stent. Not only a new formulation was developed but also the processing method to fabricate the stents was optimized. The biodegradable ureteral stents were coated with a biodegradable polymer. X-ray scan demonstrated the radiopacity of this second generation of biodegradable stents. The degradation of the biodegradable ureteral stents was assessed in artificial urine solution and it was observed that the degradation of the materials occurs in vitro between 9 and 15 days. Degradation was followed by weight loss of the samples and by chemical analysis of the solutions both by inductive couple plasma (ICP) and gel permeation chromatography (GPC). Formulation with highest amount of gelatin has shown good mechanical performance in terms of tensile properties when compared with the commercial stent (Biosoft® duo, Porges, Coloplast), and the crosslinking concentration has shown not to have a great influence on the mechanical behavior of the stents. The in vivo performance of this second-generation of the ureteral stents was herein validated. The biodegradable ureteral stents were placed in the ureters of a female pig, following the normal surgical procedure. The animals remained asymptomatic, with normal urine flow, the stents remain intact during the first 3 days and after 10 days the ureteral stents were totally degraded. This new formulation combined with a new production process overcomes the problems verified with the first generation of natural-based biodegradable stents.