Salt Heat Treatment and Passivation to Improve the Corrosion Resistance of Nitinol (Ni-Ti).

Corrosion of nitinol (NiTi) is a major factor in the failure of implantable materials. Recently, as the importance of corrosion of metals has increased, testing according to international guidelines is essential. The purpose of this study was to evaluate the corrosion resistance of NiTi wire through heat treatment and passivation process. In this study, NiTi wire used two commercially available products and a self-manufactured stent. Experimental consideration was carried out according to ASTM standards. Heat treatment was carried out in an air or a salt furnace, and the corrosion was measured after additional process, such as passivation and scratch tests. As a result, the metal potential was rapidly decreased in the air furnace group. On the other hand, the potential of wires was dramatically increased in the salt furnace group compared to the air furnace group. The dislocation decreased below the acceptance criteria (>600 mV) within 60 s of heat treatment time in the air furnace. Moreover, the potential was dramatically improved, even after only 20 min of passivation treatment (1076 mV, 442% compared to the non-passivated group), and it continued to rise until 180 min. This phenomenon was similarly observed in the group of self-manufactured stents. The potential slightly decreased by the scratch process (93.1%) was significantly reduced by the air furnace process (315 mV, 24.4% of the nontreated group). In the passivated group of the air furnace sample with reduced potential, the potential was restored to the level before the air furnace (scratch stage) (1032 mV). In conclusion, the heat treatment is preferably carried out in a salt furnace rather than an air furnace, and the passivation process can be an advantageous tool to improve corrosion resistance by suppressing the oxidation process.

A Novel High-Visibility Radiopaque Tantalum Marker for Biliary Self-Expandable Metal Stents.

Background/Aims: Radiopaque metal markers are required to improve X-ray absorption by self-expandable metal stents (SEMSs) to enable precise stent placement. A new tantalum radiopaque marker was recently developed using an ultrasonic spray technique. The aim of the present study was to evaluate the safety and visibility of tantalum markers. Methods: A total of three beagle dogs were used for a gastrointestinal tract absorption test. Five tantalum markers were placed in the stomach of each dog endoscopically. Excreted tantalum markers were collected, and their weights were compared to the original weights. In radiopacity tests, marker radiopacities on X-ray images were quantified using ImageJ software and compared with those of commercially available metal markers. Finally, the radiographic images of six patients who underwent biliary SEMS placement using tantalum marker Nitinol SEMSs (n=3) or gold marker Nitinol SEMSs (n=3) were compared with respect to marker brightness on fluoroscopic images. Results: Absorption testing showed that the marker structures and weights were unaffected. Radiopacity tests showed that the mean brightness and total brightness scores were greater for tantalum markers (226.22 and 757, respectively) than for gold (A, 209 and 355, respectively; B, 204.96 and 394, respectively; C, 194.34 and 281, respectively) or platinum markers (D, 203.6 and 98, respectively). On fluoroscopic images, tantalum markers had higher brightness and total brightness scores (41.47 and 497.67, respectively) in human bile ducts than gold markers (28.37 and 227, respectively). Conclusions: Tantalum markers were found to be more visible than other commercially available markers in X-ray images and to be resistant to gastrointestinal absorption.

A comparative reliability and performance study of different stent designs in terms of mechanical properties: foreshortening, recoil, radial force, and flexibility.

This study seeks to improve the mechanical performance of stents by conducting reliability performance testing and finite element method (FEM)-based simulations for coronary stents. Three commercially available stent designs and our own new design were tested to measure the factors affecting performance, specifically foreshortening, recoil, radial force, and flexibility. The stents used in the present experiments were 3 mm in working diameter and 18 mm of working length. The results of the experiments indicate that the foreshortening of stents A, B, C, and our new design, D, was equivalent to 2.25, 0.67, 0.46, and 0.41%, respectively. The recoil of stents A, B, C, and D was 6.00, 4.35, 3.50, and 4.36%, respectively. Parallel plate radial force measurements were A, 3.72 ± 0.28 N; B, 3.81 ± 0.32 N; C, 4.35 ± 0.18 N; and D, 4.02 ± 0.24 N. Radial forces determined by applying uniform pressure in the circumferential direction were A, 28.749 ± 0.81 N; B, 32.231 ± 1.80 N; C, 34.522 ± 3.06 N; and D, 42.183 ± 2.84 N. The maximum force of crimped stent at 2.2-mm deflection was 1.01 ± 0.08 N, 0.82 ± 0.08 N, 0.92 ± 0.12 N, and 0.68 ± 0.07 N for each of stents A, B, C and D. The results of this study enabled us to identify several factors to enhance the performance of stents. In comparing these stents, we found that our design, stent D, which was designed by a collaborative team from seven universities, performed better than the commercial stents across all parameter of foreshortening, recoil, radial force, and flexibility.

Suppression of post-angioplasty restenosis with an Akt1 siRNA-embedded coronary stent in a rabbit model.

Restenosis is the formation of blockages occurring at the site of angioplasty or stent placement. In order to avoid such blockages, the suppression of smooth muscle cells near the implanted stent is required. The Akt1 protein is known to be responsible for cellular proliferation, and specific inhibition of Akt1 gene expression results in the retardation of cell growth. To take advantage of these benefits, we developed a new delivery technique for Akt1 siRNA nanoparticles from a hyaluronic acid (HA)-coated stent surface. For this purpose, the disulfide cross-linked low molecular polyethyleneimine (PEI) (ssPEI) was used as a gene delivery carrier because disulfide bonds are stable in an oxidative extracellular environment but degrade rapidly in reductive intracellular environments. In this study, Akt1 siRNA showed efficient ionic interaction with the ssPEI carrier, which was confirmed by polyacrylamide gel electrophoresis. Akt1 siRNA/ssPEI nanoparticles (ASNs) were immobilized on the HA-coated stent surface and exhibited stable binding and localization, followed by time-dependent sustained release for intracellular uptake. Cellular viability on the nanoparticle-immobilized surface was assessed using A10 vascular smooth muscle cells, and the results revealed that immobilized ASNs exhibited negligible cytotoxicity against the adhering A10 cells. Transfection efficiency was quantified using a luciferase assay; the transgene expression of Akt1 suppression through the delivered Akt1 siRNA was measured using RT-PCR and western blot, demonstrating higher gene silencing efficiency when compared to other carriers. ASN coated on HA stents were deployed in the balloon-injured external iliac artery in rabbits in vivo. It was shown that the Akt1 released from the stent suppressed the growth of the smooth muscle at the peri-stent implantation area, resulting in the prevention of restenosis in the post-implantation phase.

Relationship of sex hormones and nocturia in lower urinary tract symptoms induced by benign prostatic hyperplasia.

OBJECTIVE: The study sought to clarify the relationship between sex hormone levels and lower urinary tract symptoms (LUTS) in patients with benign prostate hyperplasia. METHODS: Between 2007 and 2010, serum total testosterone (TT), free testosterone, and estradiol were prospectively measured in patients who were transferred to our university hospital. The 924 subjects were divided into two groups. Group I (n = 646) were treated with an alpha blocker only and group II (n = 278) were treated with an alpha blocker + a 5-alpha reductase inhibitor over 3 months before their visit. Clinical conditions were assessed by digital rectal examination, prostate-specific antigen, International Prostate Symptom Score (IPSS), transrectal ultrasonography and maximum urinary flow rate and postvoid residual urine. RESULTS: The mean age was 69.65 ± 6.56 years. The total IPSS and subscore (storage symptom) was significantly associated with age (p < 0.001/p < 0.05) and the TT level (p < 0.05/p < 0.05). TT level was significantly decreased in patients with ≥ 4 episodes of nocturia. The TT level was significantly related to the presence of severe LUTS (p < 0.05). CONCLUSIONS: Endogenous testosterone may have a beneficial effect on lower urinary tract function and that a high frequency of nocturia may induce testosterone deficiency.

Unusual presentation of bilateral adrenocortical carcinoma mimicking adrenal metastasis.

A 75-year-old female visited our hospital with bilateral adrenal masses that were detected incidentally during lumbar spine magnetic resonance imaging (MRI) for the evaluation of radiating flank pain. Consecutive computed tomography and MRI revealed bilateral adrenal masses with no evidence of lymph node enlargement or local invasion; 2[(18)F]fluoro-2-deoxyglucose (FDG)-positron emission tomography showed an intense FDG accumulation in both adrenal glands without abnormal FDG uptake in extra-adrenal regions. The laboratory test results were within normal ranges. We performed a bilateral adrenalectomy. The pathologic diagnosis of both adrenal masses was consistent with adrenocortical carcinoma. The patient recovered well with no complications.

Does bicycle riding impact the development of lower urinary tract symptoms and sexual dysfunction in men?

PURPOSE: This study was designed to determine whether men who engaged in recreational bicycle riding are more likely to be affected by lower urinary tract symptoms (LUTS) and sexual dysfunction than are man who exercised by amateur marathon running with less perineal impact. MATERIALS AND METHODS: A total of 22 healthy male amateur bicyclists and 17 healthy male amateur marathoners were enrolled in the study. We evaluated questionnaires including the International Prostate Symptom Score (IPSS) and the International Index of Erectile Function (IIEF), serum prostate-specific antigen (PSA), uroflowmetric values, postvoid residual (PVR) urine volume, and transrectal ultrasound of the prostate in all subjects. We also compared the prevalence of urination disorders (UD) and erectile dysfunction (ED). RESULTS: There were no significant differences between the two groups in age, body mass index, comorbidities, or exercise habits (p>0.05). Mean total and subscale scores of the IPSS and IIEF and the prevalence of UD (8/22 vs. 4/17, p=0.494) and ED (11/22 vs. 10/17, p=0.748) were not significantly different between the two groups. Also, there were no significant differences between the two groups in uroflowmetric parameters such as peak urinary flow rates, voided urine volume, PVR urine volume, prostate volume, or serum PSA level. CONCLUSIONS: Bicycle riding seems to have no measurable hazardous effect on voiding function or sexual function in men who cycled recreationally.

Ciprofloxacin-encapsulated poly(DL-lactide-co-glycolide) nanoparticles and its antibacterial activity.

The aim of this study was to prepare ciprofloxacin HCl (CIP)-encapsulated poly(dl-lactide-co-glycolide) (PLGA) copolymer nanoparticles and its antibacterial potential was evaluated with pathogenic bacteria, Escherichia coli (E. coli), in vitro and in vivo. CIP-encapsulated nanoparticles of PLGA were prepared by multiple emulsion solvent evaporation method. PLGA nanoparticles showed spherical shapes with particle sizes around 100-300 nm. Loading efficiency was lower than 50% (w/w) because of water-solubility properties of CIP. At drug release study, CIP showed initial burst effect for 12 h and then continuously released for 2 weeks. At in vitro antibacterial activity test, CIP-encapsulated nanoparticles showed relatively lower antibacterial activity compared to free CIP due to the sustained release characteristics of nanoparticles. However, CIP-encapsulated PLGA nanoparticles (doses: 25 mg CIP/kg of mice) effectively inhibited the growth of bacteria due to the sustained release characteristics of nanoparticles, while free CIP was less effective on the inhibition of bacterial growth. These results indicated that CIP-encapsulated PLGA nanoparticles have superior effectiveness to inhibit the growth of bacteria in vivo.

Retinol-encapsulated low molecular water-soluble chitosan nanoparticles.

This aim of this study was to encapsulate retinol into chitosan nanoparticles and reconstitute it into aqueous solution. Retinol-encapsulated chitosan nanoparticles were prepared for application of cosmetic and pharmaceutical applications. Retinol-encapsulated chitosan nanoparticle has a spherical shape and its particle sizes were around 50-200 nm according to the drug contents. Particle size was increased according to the increase of drug contents. Solubility of retinol is able to increase by encapsulation into chitosan nanoparticles more than 1600-fold. It was suggested that retinol was encapsulated into chitosan nanoparticles by ion complex as a result of FT-IR spectra. Specific peak of chitosan at 1590 cm(-1) was divided to semi-doublet due to the electrostatic interaction between amine group of chitosan and hydroxyl group of retinol. At (1)H NMR spectra, specific peaks of retinol disappeared when retinol-encapsulated chitosan nanoparticles were reconstituted into D(2)O while specific peaks both of retinol and chitosan appeared at D(2)O/DMSO (1/4, v/v) mixture. XRD patterns also showed that crystal peaks of retinol were disappeared by encapsulation into chitosan nanoparticles. Retinol-encapsulated nanoparticles were completely reconstituted into aqueous solution as same as original aqueous solution and zeta potential of reconstituted chitosan nanoparticles was similar to their original solution. At HPLC study, retinol was stably and efficiently encapsulated into chitosan nanoparticles.