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PubMed1996

[Iridium 192 brachytherapy of supra-tentorial high grade glioma recurring in irradiated areas: technique and preliminary results of the Pitié-Salpêtrière hospital group].

UNLABELLED: Our aim was to analyse feasibility and preliminary results obtained with iridium 192 re-irradiation of recurrent high grade gliomas. MATERIAL AND METHODS: a technique for implanting rigid plastic tubes afterloaded with iridium 192 wires was developed that utilised a stereotactic Leksell frame. Nineteen glioblastomas and one anaplastic glioma (12 males and 8 females: age: 20-69 years, median: 50) were implanted between January 1993 and December 1994. Previous treatments included surgery (18/20). 55-60 Gy external beam radiotherapy (20/20), and chemotherapy (16/20); interval between initial treatment and retreatment with iridium 192 was 6 to 39 months (median: 10). Maximum diameter of the tumour at the moment of implantation was 2.1-10.1 cm (median: 6.4 cm) and tumour volume 2.122 cm3 (median: 22 cm3). All tumours were supra-tentorial (right hemisphere: 9; left hemisphere: 11). Karnofsky index was 60-100 (median: 80). Implantation was carried out under local anaesthesia; tumour contours were visualised using either a CT-scan (16/20) or a MRI (4/20). Dosimetry was carried out using two orthogonal films and CT-scan images. Total dose on the reference isodose was 40-60 Gy (60 Gy: 9; 50 Gy: 7; 40 Gy: 4); dose-rate was 0.24-0.73 Gy/h (median: 0.38). RESULTS: probability of overall survival is 90% at 6 months, 55% at one year, and 26% at two years. Median survival is 56 weeks. Eleven patients died from local failure, and three from leptomeningeal metastasis. Six patients are alive, 15-30 months after the implantation. Two were reoperated for brain necrosis. Three patients showed evidence of bacterial meningitis, and three others of skin necrosis. CONCLUSION: according to this preliminary analysis, results obtained after reirradiation of high grade gliomas with iridium 192 are encouraging. More patients and longer follow-up are needed to draw definitive conclusions.

Adult↗
PubMed2001

Extraction of iridium (IV) from hydrochloric acid media with crown ether in chloroform, and its determination by ICP-AES.

A new method for the quantitative extraction and determination of trace amounts of iridium from hydrochloric acid media has been established based on the formation of an ion-association complex of iridium hexachloro anion IrCl6(2-) with dicyclohexyl-18-crown-6 (DC18C6) oxonium cation in chloroform, then determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). The effect of various factors (solvent, acid concentration, crown ether, reagent concentration, shaking time, composition of the extracted species, foreign ions, etc.) on the extraction and back-extraction of iridium has been investigated. The procedure was used to determine traces of iridium in palladium chloride and rhodium chloride.

Journal Article↗
PubMed2005

Blue and near-UV phosphorescence from iridium complexes with cyclometalated pyrazolyl or N-heterocyclic carbene ligands.

Two approaches are reported to achieve efficient blue to near-UV emission from triscyclometalated iridium(III) materials related to the previously reported complex, fac-Ir(ppz)(3) (ppz = 1-phenylpyrazolyl-N,C(2)'). The first involves replacement of the phenyl group of the ppz ligand with a 9,9-dimethyl-2-fluorenyl group, i.e., fac-tris(1-[(9,9-dimethyl-2-fluorenyl)]pyrazolyl-N,C(2)')iridium(III), abbreviated as fac-Ir(flz)(3). Crystallographic analysis reveals that both fac-Ir(flz)(3) and fac-Ir(ppz)(3) have a similar coordination environment around the Ir center. The absorption and emission spectra of fac-Ir(flz)(3) are red shifted from those of fac-Ir(ppz)(3). The fac-Ir(flz)(3) complex gives blue photoluminescence (PL) with a high efficiency (lambda(max) = 480 nm, phi(PL) = 0.38) at room temperature. The lifetime and quantum efficiency were used to determine the radiative and nonradiative rates (1.0 x 10(4) and 2.0 x 10(4) s(-1), respectively). The second approach utilizes N-heterocyclic carbene (NHC) ligands to form triscyclometalated Ir complexes. Complexes with two different NHC ligands, i.e., iridium tris(1-phenyl-3-methylimidazolin-2-ylidene-C,C(2)'), abbreviated as Ir(pmi)(3), and iridium tris(1-phenyl-3-methylbenzimidazolin-2-ylidene-C,C(2)'), abbreviated as Ir(pmb)(3), were both isolated as facial and meridianal isomers. Comparison of the crystallographic structures of the fac- and mer-isomers of Ir(pmb)(3) with the corresponding Ir(ppz)(3) isomers indicates that the imidazolyl-carbene ligand has a stronger trans influence than pyrazolyl and, thus, imparts a greater ligand field strength. Both fac-Ir(pmi)(3) and fac-Ir(pmb)(3) complexes display strong metal-to-ligand-charge-transfer absorption transitions in the UV (lambda = 270-350 nm) and phosphoresce in the near-UV region (E(0)(-)(0) = 380 nm) at room temperature with phi(PL) values of 0.02 and 0.04, respectively. The radiative decay rates for fac-Ir(pmi)(3) and fac-Ir(pmb)(3) (5 x 10(4) s(-1) and 18 x 10(4) s(-1), respectively) are somewhat higher than that of fac-Ir(flz)(3), but the nonradiative rates are two orders of magnitude faster (i.e., (2-4) x 10(6) s(-1)).

Journal Article↗
PubMed2006

Efficient green-blue-light-emitting cationic iridium complex for light-emitting electrochemical cells.

A highly luminescent novel cationic iridium complex [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 was synthesized and characterized using NMR, UV-visible absorption, and emission spectroscopy and electrochemical methods. This complex displays intense photoluminescence maxima in the green-blue region of the visible spectrum and exhibits unprecedented phosphorescence quantum yields, 80 +/- 10% with an excited-state lifetime of 2.2 mus in a dichloromethane solution at 298 K. Single-layer light-emitting electrochemical cells with the charged complex as conducting and electroluminescent material sandwiched between indium-tin oxide and Ag electrodes were fabricated, which emit green-blue light with an onset voltage as low as 2.5 V. Density functional theory calculations were performed to provide insight into the electronic structure of the [iridium bis(2-phenylpyridine)(4,4'-(dimethylamino)-2,2'-bipyridine)]PF6 complex, comparing these results with those obtained for [iridium bis(2-phenylpyridine)(4,4'-tert-butyl-2,2'-bipyridine)]PF6.

Journal Article↗
PubMed1996

Synthesis, Molecular Structure, and Vibrational Spectra of mer-Tris(carbonyl)iridium(III) Fluorosulfate, mer-Ir(CO)(3)(SO(3)F)(3).

Addition of carbon monoxide (0.5-2 atm) to iridium(III) fluorosulfate, Ir(SO(3)F)(3), dissolved in HSO(3)F over 4 days and at 60 degrees C, results in the quantitative formation of tris(carbonyl)iridium(III) fluorosulfate Ir(CO)(3)(SO(3)F)(3). Slow evaporation of the solvent produces single crystals of mer-Ir(CO)(3)(SO(3)F)(3). Crystal structure data for mer-Ir(CO)(3)(SO(3)F)(3): monoclinic, space group P2(1)/c, Z = 4, a = 8.476(1) Å, b = 12.868(2) Å, c = 12.588 (1) Å, beta = 108.24(1) degrees, V = 1304.0 Å(3), T = 200 K, R(F)() = 0.022 for 2090 data (I(o) >/= 2.5sigma(I(o))) and 200 variables. Vibrational spectra of the crystalline solid are consistent with a mer-isomer with CO stretching modes at 2249 (A(1)), 2208 (B(1)), and 2198 (A(1)) cm(-)(1) in the IR spectrum. In solution of HSO(3)F, additional CO stretching bands attributed to the fac-isomer are found in the FT-Raman and IR spectra at 2233 (A(1)) and 2157 cm(-)(1) (E). Additional evidence for a mixture of fac- and mer-isomers comes from (19)F NMR spectra. The vibrational spectra suggest strongly reduced iridium to CO pi-back-bonding. The crystal structure reveals significant intra- and intermolecular contacts between the electropositive C atom of the CO groups and O or F atoms of the fluorosulfate groups. Hence mer-tris(carbonyl)iridium(III) fluorosulfate becomes the first thermally stable, structurally characterized, and predominantly sigma-bonded carbonyl derivative of a metal in the +3 oxidation state.

Journal Article↗
PubMed2003

Optically active iridium imidazol-2-ylidene-oxazoline complexes: preparation and use in asymmetric hydrogenation of arylalkenes.

This work explores the potential of iridium complexes of the N-heterocyclic carbene oxazoline ligands 1 in asymmetric hydrogenations of arylalkenes. The accessible carbene precursors, imidazolium salts 2, and robust iridium complexes 5 facilitated a discovery/optimization approach that featured preparation of a small library of iridium complexes, parallel hydrogenation reactions, and automated analysis. Three of the complexes (5ab, 5ad, and 5dp) and a similar rhodium complex (6ap) were studied by single-crystal X-ray diffraction techniques. This revealed molecular features of 6ap, and presumably the corresponding iridium complex 5ap, that the others do not have. In enantioselective hydrogenations of arylalkenes complex 5ap was the best for many, but not all, substrates. The enantioselectivities and conversions observed were sensitive to minor changes to the catalyst and substrate structure. Ligands with aliphatic N-heterocyclic carbene substituents gave complexes that are inactive, and do not lose the 1,5-cyclooctadiene ligands under the hydrogenation conditions. Experiments to investigate this unexpected observation imply that it is of a steric, rather than an electronic, origin. Temperature and pressure effects on the conversions and enantioselectivities of these reactions had minimal effects for some alkenes, but profound effects for others. In one case, the enantioselectivities obtained at high-pressure/low-temperature conditions were opposite to those obtained under high-temperature/low-pressure conditions (-64% enantiomeric excess versus +89% enantiomeric excess); a transformation from one prevalent mechanism to another is inferred from this. The studies of pressure dependence revealed that many reactions proceeded with high conversions, and optimal enantioselectivities in approximately 2 h when only 1 bar of hydrogen was used. Deuterium-labeling experiments provide evidence for other types of competing mechanisms that lead to D-incorporation at positions that do not correspond to direct addition to the double bond.

Journal Article↗
PubMed2006

Triplet energy back transfer in conjugated polymers with pendant phosphorescent iridium complexes.

The nature of Dexter triplet energy transfer between bonded systems of a red phosphorescent iridium complex 13 and a conjugated polymer, polyfluorene, has been investigated in electrophosphorescent organic light-emitting diodes. Red-emitting phosphorescent iridium complexes based on the [Ir(btp)(2)(acac)] fragment (where btp is 2-(2'-benzo[b]thienyl)pyridinato and acac is acetylacetonate) have been attached either directly (spacerless) or through a -(CH(2))(8)- chain (octamethylene-tethered) at the 9-position of a 9-octylfluorene host. The resulting dibromo-functionalized spacerless (8) or octamethylene-tethered (12) fluorene monomers were chain extended by Suzuki polycondensations using the bis(boronate)-terminated fluorene macromonomers 16 in the presence of end-capping chlorobenzene solvent to produce the statistical spacerless (17) and octamethylene-tethered (18) copolymers containing an even dispersion of the pendant phosphorescent fragments. The spacerless monomer 12 adopts a face-to-face conformation with a separation of only 3.6 A between the iridium complex and fluorenyl group, as shown by X-ray analysis of a single crystal, and this facilitates intramolecular triplet energy transfer in the spacerless copolymers 17. The photo- and electroluminescence efficiencies of the octamethylene-tethered copolymers 18 are double those of the spacerless copolymers 17, and this is consistent with suppression of the back transfer of triplets from the red phosphorescent iridium complex to the polyfluorene backbone in 18. The incorporation of a -(CH(2))(8)- chain between the polymer host and phosphorescent guest is thus an important design principle for achieving higher efficiencies in those electrophosphorescent organic light-emitting diodes for which the triplet energy levels of the host and guest are similar.

Journal Article↗
PubMed2006

Scope and mechanism of the C-H bond activation reactivity within a supramolecular host by an iridium guest: a stepwise ion pair guest dissociation mechanism.

A chiral self-assembled supramolecular M(4)L(6) assembly has been shown to be a suitable host for a series of reactive monocationic half-sandwich iridium guests 1, 3, and 4 that are capable of activating C-H bonds. Upon encapsulation, selective C-H bond activation of organic substrates occurs. Precise size and shape selectivity are observed in the C-H bond activation of aldehydes and ether substrates. The reactions exhibit significant kinetic diastereoselectivities. Thermodynamic studies have shown that the iridium starting materials and products are bound strongly by the host assembly. The encapsulation process is largely entropy-driven. Kinetic investigations with water-soluble phosphine traps and added salts have provided evidence for a unique stepwise mechanism of guest dissociation for [4 subset Ga(4)L(6)]. Iridium guest 4 first dissociates from the host cavity to form an ion pair with the host exterior. This species then fully dissociates from the host exterior into the bulk solution. Model ion pair intermediates were characterized directly with (1)H NMR NOESY techniques. The rate of iridium guest dissociation is slower than the rate observed for the C-H bond activation processes, indicating that the selective C-H bond activation reactivity occurs within the cavity of the supramolecular host.

Journal Article↗
PubMed2003

Alkoxy/siloxy group exchange in the system vinyltrialkoxysilane-iridium(I) siloxide complex.

A study of reactions of dimeric siloxide iridium complex, [[(cod)Ir(mu-OSiMe3)]2] (1) with vinyltriethoxysilane and vinyltrimethoxysilane has revealed a new type of the reation--alkoxy group transfer from silicon to iridium with a simultaneous transfer of a siloxy group from iridium to silicon--as a result of which vinyldialkoxytrimethyldisiloxane and dimeric alkoxide iridium complex [[(cod)Ir(mu-OR)]2] (3) are formed. The structure of [[(cod)Ir(mu-OEt)]2] (3a) has been solved by X-ray diffraction.

Journal Article↗
PubMedDate not supplied

Electrogenerated chemiluminescence from polymer-bound ortho-metallated iridium(III) systems.

Three ortho-metallated iridium complexes whose emission maxima fall in different regions of the electromagnetic spectrum were bound in either Nafion or poly(9-vinylcarbazole) and their electrogenerated chemiluminescence (ECL) reported. The reaction of F(Ir)pic [bis(3,5-difluoro-2-(2-pyridyl)phenyl-(2-carboxypyridyl)-iridium III] with the oxidative-reductive co-reactant tri-n-propylamine (TPrA) resulted in ECL when the iridium complex was bound in Nafion. No significant ECL was observed for (btp)(2)Ir(acac) (bis[2,(2'-benzothienyl)-pyridinato-N,C3'](acetylacetonate)Ir(III)), and Ir(ppy)(3) (where ppy = 2-phenylpyridine) under these conditions. However, all three compounds displayed ECL with TPrA when bound in poly(9-vinylcarbazole).

Cations↗
PubMed2006

Synthesis and application of chiral N-heterocyclic carbene-oxazoline ligands: iridium-catalyzed enantioselective hydrogenation.

Two libraries of enantiomerically pure imidazolium salts bearing an oxazoline unit were synthesized. Deprotonation of the imidazolium salts and complexation of the resulting oxazoline-carbene ligands to iridium(I) was achieved in one step by mixing the imidazolium salts with NaOtBu and [(eta(4)-cod)IrCl](2) in THF at room temperature. The air-stable complexes were purified by flash chromatography. All complexes were analyzed by two-dimensional (2D) NMR methods and one compound from each family was characterized by X-ray structure analysis. The two libraries of iridium complexes were successfully tested in the asymmetric hydrogenation of unfunctionalized and functionalized olefins. Enantioselectivities of up to 90 % ee were obtained with trans-alpha-methylstilbene. Upon complexation of imidazolium salt 15 p with R(1) = phenyl, C-H bond activation of the phenyl ring gave rise to iridium(III) complex 17, which was fully characterized by NMR spectroscopy and X-ray structure analysis. Complex 17 proved to be catalytically inactive in the hydrogenation.

Catalysis↗
PubMed1994

Treatment of oral cancers using iridium-192 interstitial irradiation.

OBJECTIVE: To assess retrospectively the outcome and morbidity of Iridium-192 brachytherapy in the treatment of oral cancers. DESIGN: Retrospective audit of cases treated between 1981 and 1991. SETTING: Newcastle upon Tyne, England. SUBJECTS: 73 patients with oral cancer treated with Iridium-192. MAIN OUTCOME MEASURES: Local control, crude and cause specific survival, and local morbidity. RESULTS: Seventy four cases of squamous cell carcinoma of the oral cavity were treated using interstitial Iridium-192. The disease specific 5-year survival rates were 69% for T1, 67% for T2, and 0% for T3 tumours. Mortality from recurrent cancer was 20%, and from intercurrent disease was 28%. The incidence of major radiation induced morbidity was 11%, and the local control rate was 81% for T1, 69% for T2, and 50% for T3 tumours. CONCLUSION: Interstitial radiotherapy remains a viable and valuable mode of treatment for a small proportion of patients presenting with early (T1 and T2) oral cancers.

Adolescent↗
PubMed1984

Results of the treatment of 165 lid carcinomas by iridium wire implant.

A group of 160 adult patients with epithelial tumors of the lid and/or canthi treated by iridium 192 wire implant are presented. There were 165 epithelial tumors, most of them were basocellular type (85%). In all cases, a nonradioactive procedure was used with disposable angiocatheters before introducing active wires. Respectively, 111/114 (97.4%) of "new" lesions and 48/51 (94%) of previously treated tumors were definitively cured by iridium wire implant. Among the 6 local recurrences, 4 were salvaged by a second iridium implant, and the two others by extensive surgery. Local side effects were present in 30 patients (18%): impairment of the eyelid aperture 9, stenosis of lacrymal ducts 7, eversion of the lid 7, lack of substance 7. These postherapeutic complications were significantly more frequent in treating recurrent lesions (15/48, 31.2%) than in previously untreated tumors (15/112, 13.4%). No visual complication was observed even in the early patients of this series.

Adenocarcinoma↗
PubMed1987

Definitive radiation treatment for early stage carcinoma of the soft palate and uvula: the indications for iridium 192 implantation.

From 1971 to 1984 59 T1 and T2 carcinomas of the soft palate and uvula were treated definitively by irradiation at the Henri Mondor hospital. Included are ten patients previously irradiated to the oropharyngeal area for either a carcinoma of the soft palate or another malignancy. Sixteen patients were treated by external irradiation alone, 14 by Iridium 192 implantation, and 29 by a combination of the two. Two techniques of implantation were used: the guide gutter technique (33 patients) and the plastic tube technique (10 patients). Clinically negative neck nodes (51/59) either received prophylactic telecobalt therapy (39/51) or were surveilled (12/51). Clinically involved nodes (8/59) were managed either by external irradiation alone (4/8) or combined with neck dissection (4/8). Local failure was 25% (4/16) after exclusive telecobalt therapy, 18% (5/19) after combined telecobalt therapy and implantation, and 0% (0/14) after Iridium 192 implantation alone. No local failures were seen with the plastic tube technique (0/10) as compared to 15% (5/33) for guide gutters. Only two nodal failures were observed (2/59: 3%). Crude 5-year disease-free survival was 33%. Severe complications were limited to one osteonecrosis, one soft tissue necrosis, and one partial palatal incompetence. Salivary impairment was reduced when implantation was used for part or all of the treatment. We recommend 45 Gy external radiation followed by 30 Gy from Iridium 192 implantation using the plastic tube method unless there has been prior oropharyngeal irradiation, in which case we give 60 Gy from implantation alone. For clinically negative neck nodes, we recommend 45 Gy prophylactic external neck irradiation. For clinically positive lymph nodes, this should be followed by either a 25 to 30 Gy boost to the involved nodes or a neck dissection.

Brachytherapy↗
PubMed1991

Influence of dose rate on local control of breast carcinoma treated by external beam irradiation plus iridium 192 implant.

From 1971 to 1983, 20 T1, 267 T2, and 53 T3 biopsy-proven adenocarcinomas of breast were definitively managed by radiotherapy. The breast and regional nodes received 45 Gy of 60Co irradiation in 25 fractions over 5 weeks (45 Gy/25/5 wks). Electrons were used to deliver a further 15 Gy/7/1.5 weeks to the internal mammary chain and 25 Gy/11/2.5 weeks to the lower axilla. The primary tumor was boosted by Iridium 192 implant for a further 37 Gy prescribed at 85% of the basal dose rate (Paris system). Rigid needles were secured by templates in single plane (58/398) or double plane (340/398) geometry. Results of the 340 two-plane implants have been analyzed to look for a possible influence of dose rate on local control. Follow-up for patients free of local recurrence is 4-204 months (median: 92 months). The 340 tumors were divided into three groups according to dose rate: 0.32-0.49 Gy/hr (n = 95), 0.50-0.59 Gy/hr (n = 120), and 0.60-0.90 Gy/hr (n = 125). The three groups are statistically comparable according to age, tumor size, mean 60Co dose, mean Iridium dose, overall treatment time, and follow-up. The local failure rate in the three groups is 27% (26/95), 20% (24/120), and 13% (16/125) (p less than 0.03, Chi square). At 15 years the estimated local control (Kaplan Meier) is 60%, 72%, and 84% (p less than 0.02, Logrank), respectively. This analysis indicates that there is a significant effect of dose rate on local control for carcinoma of the breast treated by combined external beam (45 Gy) plus Iridium 192 implantation (37 Gy). To maximize local control the authors recommend an implant dose rate of greater than or equal to 0.6 Gy/hr.

Adenocarcinoma↗
PubMed1992

Transperineal percutaneous iridium-192 interstitial template implant of the prostate: results and complications in 321 patients.

A total of 321 patients with localized adenocarcinoma of the prostate treated by modified pelvic lymphadenectomy, Iridium-192 implant, and external beam iridium radiation were retrospectively reviewed. Analysis covered 8 years between 1981 and 1989 with a median population age of 72 (range 42 through 82 years). Disease-free survival for the entire group is 69% at 5 years with a median follow-up of 34 months (range 1.5 months to 98.5 months). As expected, both bulkier disease and positive nodal status adversely affected 5-year disease-free survival (p = 0.0001 for both). For tumors stage T1b (A2), T2a (B1), T2b (B2), T3 (C) the disease-free survival is 89.5%, 89.9%, 64.7%, and 48.8%, respectively; for NO disease 5-year disease-free survival is 76.5% versus N1/N2 disease with 5-year disease-free survival of 33.2%. Local control was excellent except for bulkier disease (p = 0.009). Tumors T1b, T2a, T2b, and T3 have 60-month local control rates of 95%, 93%, 83.6%, and 73.1%, respectively. Histologic grade also affected disease-free survival and local control with grade 1, grade 2, grade 3 showing 81.2%, 65.7%, and 45.1% disease-free survival at 5 years; and 93.6%, 82.2%, and 72.4% local control at 5 years. Estimates obtained using Kaplan-Meier method. Radiation induced morbidity was analyzed separately for all patients, there were 41 patients (13% of total) with 54 documented complications. There were no Grade 4 or 5 complications as per RTOG categories. Only 3 cases showed grade 3 complications (1%) and 51 cases showed grade 2 complications (15.9%). Grade 1 complications were not recorded. Of the grade 2 and grade 3 complications 30 were GU and 22 were rectal. The morbidity associated with combined interstitial implantation by transperineal percutaneous template and external beam iridium radiation for the localized prostate cancer is minimal with excellent local control and disease-free survival.

Adenocarcinoma↗
PubMed1975

Inhibition of enzymatic hydrolysis of end-phosphate DNA by iridium chlorocomplexes.

The enzymatic hydrolysis of end-phosphate DNA by calf intestine alkaline phosphatase is inhibited by iridium chlorocomplexes. The inhibitory effect is strongly influenced by the chemical form of iridium. While hexachloroiridate (IV) and hexachloroiridite (III) strongly inhibit the enzymatic activity of calf intestine alkaline phosphatase no inhibitory effect was observed when these chlorocomplexes were previously irradiated by light and transformed to their photochemical reaction products. Evidence is presented which suggests that the noncompetitive and irreversible inhibitory effect was due to an effective interaction of iridium with the protein without release of its metal constituent at a very low concentration of enzyme. The protective effects of various chemicals on the inhibitory action was also briefly investigated.

Alkaline Phosphatase↗
PubMed2002

Characterization of iridium film as a stimulating neural electrode.

Iridium films having near-bulk properties were formed by electron-beam evaporation with simultaneous bombardment of Ar ion beam. The charge-injection capabilities of Ir film were investigated, and the detrusor pressure induced by S2 stimulation with Ir-coated Pt electrode was measured and compared with the uncoated Pt electrode. The charge densities of Ir film were continuously increased with increase in the number of cycles in 0.1 M H2SO4 due to the accumulation of the iridium oxide phase. The iridium oxide formed contained nano-pores, and oxides had different dielectric properties. The Ir film could inject various amounts of charge in physiological solution under the identical stimulating condition depending on the degree of activation in 0.1 M H2SO4. S2 stimulation by Ir-coated Pt electrode caused more efficient bladder contraction of the male dog than the uncoated Pt electrode under the identical stimulus condition.

Alloys↗