[Cold Plasma to Treat Therapy-Refractive Corneal Ulcers]. / Kaltplasma zur Behandlung therapierefraktärer Hornhautulzera.

BACKGROUND: The integrity of the ocular surface and the transparency of the cornea is crucial to obtain a good visual acuity - a requirement to actively participate in both social and professional environments. The homeostasis of the ocular surface is constantly endangered by microbes and by intrinsic factors with negative influence on wound healing. Furthermore, widespread use of contact lenses obtain a risk of corneal infection even resulting in corneal perforation and loss of the eye. Current therapies include topical and systemic antibiotics and antimycotics, often applied in an in-ward setting. PATIENTS/MATERIALS AND METHODS: Some microbes can be therapy-resistent or -refractory and therefore cause a deterioration of the clinical aspect. In this study, the effects of cold plasma treatment of corneal ulcers on reduction of microbial load in vitro, in tissue ex vivo and in a therapy-refractory ulcer. RESULTS: In vitro, ex vivo and in the patient microbial load could be reduced or the clinical findings improved. CONCLUSIONS: Plasma medicine and its disinfective properties could open a novel approach to treat microbial infections of the cornea. The can result in reduced treatment times, a faster demission of the patients and overall in a reduction of health care costs.

Dexamethasone intravitreal implant in retinal vein occlusion: real-life data from a prospective, multicenter clinical trial.

PURPOSE: To evaluate the relationship between duration of macular edema associated with retinal vein occlusion (RVO) and the achievement of vision gain in patients receiving dexamethasone intravitreal implant (DEX implant) in real-world clinical practice, and to define patterns of use of DEX implant and its efficacy and safety in the treatment of patients with RVO in clinical practice. METHODS: This prospective, open-label, multicenter, 6-month observational phase IV study conducted at 70 sites in Germany enrolled patients diagnosed with macular edema following branch or central RVO (BRVO, CRVO) who were given DEX implant. Follow-up visits and evaluations occurred in accordance with normal clinical practice. Re-treatment with DEX implant and use of other RVO therapies was at the discretion of the treating physician. The primary endpoint was mean change in best-corrected visual acuity (BCVA) from baseline at week 12. RESULTS: The analysis population consisted of 573 patients (64 % BRVO, 36 % CRVO). Patients received a mean of 1.17 DEX implant treatments during the study period; 84.3 % of patients received a single DEX implant and 19.9 % received adjunctive other RVO treatment. Among patients with analyzable BCVA data at baseline and week 12 (n = 351), mean change from baseline BCVA at week 12 was -0.16 (standard deviation, 0.30) logMAR (+7.8 approximate Early Treatment Diabetic Retinopathy Study [ETDRS] letters) (p < 0.001), and 33.9 % of patients had gained at least 3 lines in BCVA from baseline. Mean change from baseline BCVA at week 12 was +9.5, +7.3, and +5.4 approximate ETDRS letters in patients with macular edema duration < 90 days, from 90 to 180 days, and >180 days respectively. Improvement in BCVA through week 24 and decreases in central retinal thickness were seen in both BRVO and CRVO. The most common adverse drug reaction was increased intraocular pressure. No glaucoma incisional surgeries were required. CONCLUSIONS: DEX implant was effective in improving BCVA and central retinal thickness in patients with BRVO and CRVO in real-world clinical practice. The largest gains in BCVA over 6 months occurred in patients with recent onset macular edema, confirming the benefit of early treatment. DEX implant was well tolerated and had an acceptable safety profile.

Nile red dye in aqueous surfactant and micellar solution.

The solubilization behavior of nile red dye in aqueous surfactant and micellar solutions was studied by optical spectroscopic techniques, dynamic light scattering, and atomic force microscopy. Nile red exhibits considerable absorption in the submicellar concentration region. When dispersed in aqueous surfactant and/or micellar solution, nile red molecules tend to form nonemissive dimers and/or H-type aggregates through π-π stacking interactions. This phenomenon may limit the use of nile red in solubilization studies. In the presence of ionic SDS and CTAB micelles, the solubilization of nile red appears to take place primarily at the charged micellar surface within the interfacial region. Similarly, spectra in micellar solution of nonionic Triton X-100 revealed that nile red dye penetrates the hydrophilic, interfacial poly(oxyethylene) region of the micelles but cannot reach the hydrophobic, innermost core. Our results therefore suggest that nile red dye must be chosen carefully when probing (micellar) hydrophobic environments and (micro)domains.

Prevalence of magnetic resonance imaging-defined atrophic and hypertrophic phenotypes of knee osteoarthritis in a population-based cohort.

OBJECTIVE: To describe the association of osteophytes with concomitant cartilage damage, assessed using semiquantitative magnetic resonance imaging (MRI), and to describe the prevalence of atrophic and hypertrophic phenotypes of tibiofemoral knee osteoarthritis (OA) in a population-based cohort. METHODS: Participants of the Framingham Knee Osteoarthritis Study were examined with a 1.5T MRI system using triplanar intermediate-weighted fat-suppressed sequences. Cartilage and osteophytes were assessed using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). Overall prevalence of knees with severe cartilage damage and concomitant osteophyte status were described. Odds ratios for the likelihood of having severe cartilage damage according to osteophyte size were estimated using a logistic regression model. An additional analysis assessed knees according to phenotype in relation to radiographic OA status, with the atrophic phenotype being defined as knees with absent or only tiny osteophytes (WORMS grade ≤2 on a 0-7 scale) in all 10 tibiofemoral subregions but exhibiting severe cartilage damage, and the hypertrophic phenotype being defined as knees with large osteophytes (WORMS grade ≥5 on a 0-7 scale) but lacking substantial cartilage damage. RESULTS: In this study, 1,597 knees of 1,248 subjects were included. Of the 67 knees with large osteophytes, 54 (80.6%) exhibited severe cartilage damage. The risk of severe cartilage damage increased markedly with increasing osteophyte size. Twenty-one knees (1.3%) showed an atrophic phenotype. Only 3 knees (0.2%) exhibited a hypertrophic phenotype. CONCLUSION: The majority of knees with severe tibiofemoral cartilage damage exhibited moderate to large osteophytes. The larger the osteophyte, the more likely was the presence of severe cartilage damage. A minority of knees exhibited the atrophic phenotype, which also included knees without radiographic OA. The hypertrophic phenotype was extremely rare.

Brilliant Blue G as protective agent against trypan blue toxicity in human retinal pigment epithelial cells in vitro.

BACKGROUND: Combinations of trypan blue (TB), Brilliant Blue G (BBG) and polyethyleneglycol had been shown before to be less toxic to ARPE retinal pigment epithelial cells than TB alone. We studied systematically the influence of combinations of dyes on cell damage. METHODS: ARPE cells were exposed to TB (concentration range 0.025 to 1 %), BBG (0.0025 to 0.5 %), and combinations of the two dyes, dissolved in phosphate buffered saline (PBS), for periods between 5 and 60 min. Cell damage was monitored with the WST-1 assay. The effect of different salt concentration was measured in the same way. RESULTS: TB in concentrations of 0.075 % and higher was toxic to the cells already after 30 min incubation. BBG was toxic after 30 min in concentration of 0.1 % and higher, but had a protective effect on cells with incubation time of 5 min and concentrations up to 0.1 %. BBG at concentrations of 0.025 % protected against TB-induced damage at 5 min and 30 min incubation. Salt concentrations between 113 and 225 mM did not influence cell survival even after 30 min. In the presence of TB, propidium iodide bound strongly to the cells. CONCLUSIONS: BBG acts as a protecting agent against TB toxicity.

Dyes for Eyes™: hydrodynamics, biocompatibility and efficacy of 'heavy' (dual) dyes for chromovitrectomy.

As epiretinal membranes (ERMs), the internal limiting membrane (ILM) and the vitreous cortex are essentially transparent tissues, or translucent structures, nontraumatic removal may be challenging in various types of macular surgery. Vital dyes stain these thin tissues, thus allowing for better visualization of these structures during vitrectomy and selective 'membrane peeling' from the underlying retina. To avoid swirling of the dye within the fluid-filled vitreous cavity, and to better target the dye onto the macula, a fluid-air exchange is commonly performed. However, this may jeopardize visualization of the macula during peeling due to clouding of the posterior lens capsule, and may lead to postoperative visual field defects. Recently, a new dye solution for staining the ERM and ILM simultaneously has been developed that circumvents the need for fluid-air exchange, i.e. MembraneBlue-Dual™. This paper will focus on the hydrodynamics and biocompatibility of this 'heavy' dual dye and its efficacy for staining of the ILM and/or ERMs during posterior segment surgery in a multicenter clinical setting.

Advances in switchable supramolecular nanoassemblies.

Supramolecular nanoassemblies are gaining increasing importance as promising new materials with considerable potential for novel and promising applications. Within supramolecular nanoassemblies the connectivity of the monomeric units is based on reversible noncovalent interactions, like van der Waals interactions, hydrogen bonding, or ionic interactions. As the strength of these interactions depends on the molecular surrounding, the formation of nanoassemblies in principle can be controlled externally by changing the environment and/or the molecular shape of the underlying monomer. This way it is not only possible to switch the self-assembly on or off, but also to change between different aggregation states. In this minireview we present some recent selected approaches to supramolecular stimuli-responsive nanoassemblies.

Glycine-terminated dendritic amphiphiles for nonviral gene delivery.

Development of nonviral vectors for the successful application of gene therapy through siRNA/DNA transfection of cells is still a great challenge in current research. (1, 2) In the present study, we have developed multivalent polyglycerol dendron based amphiphiles with well-defined molecular structures that express controlled glycine arrays on their surfaces. The structure-activity relationships with respect to the siRNA complexation, toxicity, and transfection profiles were studied with synthesized amphiphilic polycations. Our findings revealed that a second-generation amphiphilic dendrimer (G2-octaamine, 4) that has eight amine groups on its surface and a hydrophobic C-18 alkyl chain at the core of the dendron, acts as an efficient vector to deliver siRNA and achieve potent gene silencing by investigating the knockdown of luciferase and GAPDH gene activity in HeLa cells. Interestingly, the amphiphilic vector is nontoxic even at higher ratio of N/P 100. To the best of our knowledge this is the first example of successful in vitro siRNA transfection using dendritic amphiphiles. We believe that this supramolecular complex may serve as a new promising alternative for nonviral siRNA delivery systems and will be investigated for in vivo siRNA delivery in the future.

PBF-LB/M of Low-Alloyed Steels: Bainite-like Microstructures despite High Cooling Rates.

Laser-based powder bed fusion of metals (PBF-LB/M) is an emerging technology with enormous potential for the fabrication of highly complex products due to the layer-wise fabrication process. Low-alloyed steels have recently gained interest due to their wide potential range of applications. However, the correlation between the processing strategy and the material properties remains mostly unclear. The process-inherent high cooling rates support the assumption that a very fine martensitic microstructure is formed. Therefore, the microstructure formation was studied by means of scanning electron microscopy, hardness measurements, and an analysis of the tempering stability. It could be shown that additively manufactured Bainidur AM samples possess a bainitic microstructure despite the high process-specific cooling rates in PBF-LB/M. This bainitic microstructure is characterized by an excellent tempering stability up to temperatures as high as 600 °C. In contrast to this, additively manufactured and martensitic-hardened specimens are characterized by a higher initial hardness but a significantly reduced tempering stability. This shows the potential of manufacturing products from Bainidur AM for high-temperature applications without the necessity of a post-process heat treatment for achieving the desired bainitic microstructure.

New dual dye for vitreoretinal surgery with increased transparency.

OBJECTIVES: To develop a new dye formulation for vitreoretinal surgery, which shows increased transparency for better intraoperative handling with better parameters important for use. METHODS AND ANALYSIS: A new blue dye, DDG, was synthesised and tested for toxicity and staining. Diglycerol as new density-increasing additive was identified, and its toxicity and lack of influence of the staining with trypan blue (TB) on a collagen membrane as model for the epiretinal membrane was determined. Transparency of the dye solution was evaluated. RESULTS: DDG is as alternative to Brilliant Blue G (BBG), with good staining properties for interna limitans models, and a good safety profile. Diglycerol is a new non-toxic additive replacing PEG3350, with reduced viscosity and no reduction in staining, allowing the reduction of TB to achieve the same staining level of the collagen membrane by 40%, with greater transparency of the dye solution and reduced viscosity. Both factors should facilitate a safe removal during surgery. CONCLUSION: A new dye preparation with improved performance in comparison to marketed combinations of BBG and TB was developed. Its reduced TB concentration and viscosity with maintained density allow better tolerance and handling.

Biocatalytic route to sugar-PEG-based polymers for drug delivery applications.

Sugar-PEG-based polymers were synthesized by enzymatic copolymerization of 4-C-hydroxymethyl-1,2-O-isopropylidene-ß-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-benzylidene-ß-L-threo-pentofuranose/4-C-hydroxymethyl-1,2-O-isopropylidene-3-O-pentyl-ß-L-threo-pentofuranose with PEG-600 dimethyl ester using Novozyme-435 (Candida antarctica lipase immobilized on polyacrylate). Carbohydrate monomers were obtained by the multistep synthesis starting from diacetone-D-glucose and PEG-600 dimethyl ester, which was in turn obtained by the esterification of the commercially available PEG-600 diacid. Aggregation studies on the copolymers revealed that in aqueous solution those polymers bearing the hydrophobic pentyl/benzylidene moiety spontaneously self-assembled into supramolecular aggregates. The critical aggregation concentration (CAC) of polymers was determined by surface tension measurements, and the precise size of the aggregates was obtained by dynamic light scattering. The polymeric aggregates were further explored for their drug encapsulation properties in buffered aqueous solution of pH 7.4 (37 °C) using nile red as a hydrophobic model compound by means of UV/vis and fluorescence spectroscopy. There was no significant encapsulation in polymer synthesized from 4-C-hydroxymethyl-1,2-O-isopropylidene-ß-L-threo-pentofuranose because this sugar monomer does not contain a big hydrophobic moiety as the pentyl or the benzylidene moiety. Nile red release study was performed at pH 5.0 and 7.4 using fluorescence spectroscopy. The release of nile red from the polymer bearing benzylidene moiety and pentyl moiety was observed with a half life of 3.4 and 2.0 h, respectively at pH 5.0, whereas no release was found at pH 7.4.

Phenotypic characterization of skeletal abnormalities of Osteopotentia mutant mice by micro-CT: a descriptive approach with emphasis on reconstruction techniques.

PURPOSE: The novel protein osteopotentia (Opt) has recently been described as an essential regulator of postnatal osteoblast maturation and might possibly be responsible for some of the rarer types of osteogenesis imperfecta. Our aim was the evaluation of micro CT for the qualitative morphological assessment of skeletal abnormalities of Osteopotentia-mutant mice in comparison to radiography and histology. MATERIALS AND METHODS: Four homozygous mice with insertional mutations in the Opt gene and three wild-type controls were examined ex vivo using radiography and micro-CT. Two of the homozygous animals were evaluated histologically (trichrome reagent). For the micro-CT evaluation three-dimensional (3D) surface reconstructions and two-dimensional (2D) multiplanar reformations (MPRs) were applied. RESULTS: The Opt-homozygous mice exhibited severe growth. The radiographic examinations showed osteopenia and fractures with hypertrophic callus formation and pseudarthroses of the forelimbs and ribs. Micro-CT confirmed these findings and was able to demonstrate additional fractures especially at smaller bones such as the metacarpals and phalanges. Additional characterization and superior delineation of cortices and fracture fragments was achieved by 2D MPRs. Histological correlation verified several of these imaging findings. CONCLUSION: Micro-CT is able to screen Opt-mutant mice for osseous pathologies and furthermore characterize these anomalies. The modality seems superior to conventional radiography, but is not able to demonstrate cellular pathology. However, histology is destructive and more time- and material-consuming than micro-CT. Additional information may be gathered by 2D MPRs.

A new family of nonionic dendritic amphiphiles displaying unexpected packing parameters in micellar assemblies.

In this paper we report on the synthesis of a new family of nonionic dendritic amphiphiles that self-assemble into defined supramolecular aggregates. Our approach is based on a modular architecture consisting of different generations of hydrophilic polyglycerol dendrons [G1-G3] connected to hydrophobic C(11) or C(16) alkyl chains via mono- or biaromatic spacers, respectively. All amphiphiles complex hydrophobic compounds as demonstrated by solubilization of Nile Red or pyrene. The structure of the supramolecular assemblies as well as the aggregation numbers are strongly influenced by the type of the dendritic headgroup. While the [G1] amphiphiles form different structures such as ringlike and fiberlike micelles, the [G2] and [G3] derivatives aggregate toward spherical micelles of low polydispersity clearly proven by transmission electron microscopy (TEM) measurements. In the case of the biaromatic [G2] derivative, the structural persistence of the micelles allowed a three-dimensional structure determination from the TEM data and confirmed the aggregation number obtained by static light scattering (SLS) measurements. On the basis of these data, molecular packing geometries indicate a drastic mass deficit of alkyl chains in the hydrophobic core volume of spherical micelles. It is noteworthy that these highly defined micelles contain as little as 15 molecules and possess up to 74% empty space. This behavior is unexpected as it is very different from classical detergent micelles such as sodium dodecyl sulfate (SDS), where the hydrophobic core volume is completely filled by alkyl chains.

Cost of transfusion-dependent myelodysplastic syndrome (MDS) from a German payer's perspective.

No curative treatment exists for patients with myelodysplastic syndrome (MDS) besides allogeneic stem cell transplantation. Hence, palliative treatment is provided for a life time accruing high health care cost. As no study in cost of MDS exists in Germany, the objective of this study was to assess and analyze costs of transfusion-dependent low/intermediate-1-risk MDS in Germany from a payers' perspective. From seven centers, 116 low/intermediate-1-risk transfusion-dependent MDS patients with and without isolated 5q-deletion were identified. Claims data and patient records of the previous 5 years were used to collect health care utilization data retrospectively. Publicly available tariff books and remuneration schemes were applied to evaluate mean costs per year in Euro with 2007 as base year. The annual cost of MDS patients was estimated at 14,883. Subgroup analyses showed differences in patient's characteristics and outcomes among patients treated at a hospital-based vs. an office-based setting. Patients treated at the hospital-based registry show higher cost, whereas the reasons for that still need to be detected. Overall, per annum direct costs range from 12,543 (SD 12,967) to 24,957 (SD 36,399) in different subgroups of patients. In both groups, patients with 5q-deletion use more medication than those without deletion. Mean costs for medication in the office-based setting are 5,902 for patients with isolated 5q-deletion vs. 3,932 for patients with no deletion, respectively. MDS leads to a high health care utilization and resulting costs for the health care system which requires a detailed analysis of underlying services.

Localization of hydrophobic N-diazeniumdiolates in aqueous micellar solution.

The interaction of phenyl-substituted zwitterionic N-diazeniumdiolates PhCH(2)N[N(O)NO](-)(CH(2))(2)NH(3)(+) (1) and PhCH(2)N[N(O)NO](-)(CH(2))(2)NH(2)(+)CH(2)Ph (2) with aqueous micellar solutions of prototypal surfactants was investigated by means of UV/vis and (1)H NMR spectroscopy in order to establish the localization of hydrophobic N-diazeniumdiolates in micelles as a model for the binding of the NO donors in biological membranes. In the presence of sodium dodecyl sulfate (SDS), significant shifts of the apparent pK(a) values of 1 and 2 were observed, suggesting strong electrostatic interaction between the diazeniumdiolates and the negatively charged SDS micelles. No effect on both pK(a) and rate of NO release was found in the presence of Triton X-100. The solubilization site of micellar bound N-diazeniumdiolates was established by (1)H NMR spectroscopic studies, taking advantage of the spectroscopic effects induced by CH-pi interactions. The spectra indicate that in alkaline solutions of SDS 1 resides preferably at the micellar surface within the interfacial region, whereas the more hydrophobic NO donor 2 penetrates into the apolar region of the micelle. This suggests hydrophobic interaction as the main driving force for micellar binding of 2 in alkaline solution. Similar studies in presence of Triton X-100 indicate that 1 and 2 are adsorbed within the poly(oxyethylene) layer of the micellar surface rather than penetrating the palisade layer of the micelles. In alkaline solutions of hexadecyltrimethylammonium bromide (CTAB), 1 and 2 bind to the cationic micellar aggregates, whereby the solubilization site strongly depends on the hydrophobicity of the substrate. Up to a moderate pH of 8, the hydrophobic NO donor 2 penetrates the hydrocarbon region of the micelles. As a result, the rate of NO release from 2 is noticeably inhibited by the micellar aggregates due to the higher local concentration of hydroxide ions along the micelle-water interface. From solubilization studies, guidelines for the development and application of future NONOates can be derived. The rate of NO release from micellar bound diazeniumdiolates is determined by the surface charge of the micelles. This ability to tune stability is significant for the design and selection of potential NO delivery systems (drug formulations).

New stains for anterior capsule surgery.

PURPOSE: To investigate whether new dyes and dye combinations can give equivalent or better staining in anterior capsule surgery than existing dyes with a low degree of toxicity on relevant cells. SETTING: University laboratory of Jacobs University Bremen, Germany. DESIGN: Laboratory experimental study. METHODS: Pig eyes were collected post mortem. Cataract was induced by microwave irradiation. Access to the lens capsule was through open-sky surgery. Staining was performed and results were documented by photography. The toxicity of the dyes was evaluated in 3 different cell lines immediately after exposure and with a delay of 24 hours, with exposure in the dark or subsequent strong illumination. RESULTS: A new cyanine dye, BIP (2-[5-[3,3-dimethyl-1-(4-sulfobutyl)-1,3-dihydro-indol-2-ylidene]-penta-1,3-dienyl]-3,3-dimethyl-1-(4-sulfobutyl)-3H-indolium sodium), was found to lead to green staining, with reduced toxicity on corneal endothelial cells. Staining could be further enhanced by combining it with trypan blue. Methylene blue was very toxic, whereas its combination with trypan blue was much less toxic. CONCLUSIONS: With BIP alone or in combination with trypan blue, safe staining of the capsule can be achieved, resulting in a green color.

Early effects of triamcinolone on vascular endothelial growth factor and endostatin in human choroidal neovascularization.

OBJECTIVE: To evaluate the early effects of triamcinolone acetonide as monotherapy or as an adjuvant to ocular verteporfin photodynamic therapy (PDT) on angiogenesis in human choroidal neovascularization (CNV) secondary to age-related macular degeneration. METHODS: Retrospective review of an interventional series of 55 patients who underwent CNV extraction. Eleven patients were treated with intravitreal triamcinolone acetonide (4 mg) monotherapy (triamcinolone-treated CNV group [n = 5]) or with PDT-triamcinolone combination therapy (PDT-triamcinolone-treated CNV group [n = 6]) 3 to 9 days before surgery. Forty patients who underwent CNV extraction without previous therapy (control CNV group) and 4 patients who underwent CNV extraction 3 days after PDT (PDT CNV group) served as control subjects. The CNV samples were stained for CD34, endostatin, cytokeratin 18, and vascular endothelial growth factor (VEGF). RESULTS: Vascular endothelial growth factor expression was stronger in the PDT CNV samples (P < .001), triamcinolone CNV samples (P = .01), and PDT-triamcinolone CNV samples (P = .007) compared with the control CNV samples. There were no statistically significant differences in VEGF expression among the PDT CNV samples, triamcinolone CNV samples, and PDT-triamcinolone CNV samples. Endostatin expression was weaker in the PDT CNV samples than in the control CNV samples (P = .008). Endostatin expression was stronger in the triamcinolone CNV samples and the PDT-triamcinolone CNV samples compared with the control CNV samples (P = .001 and P < .001, respectively) and the PDT CNV samples (P < .001 for both). CONCLUSION: To some extent, triamcinolone monotherapy seems to exert its angiogenesis inhibitory effects on CNV by enhancing endostatin expression rather than by suppressing VEGF expression.

Hydrophobic N-diazeniumdiolates and the aqueous interface of sodium dodecyl sulfate (SDS) micelles.

Zwitterionic diazeniumdiolates of the form RN[N(O)NO(-)](CH(2))(2)NH(2) (+)R, where R=CH(3) (1), (CH(2))(3)CH(3) (2), (CH(2))(5)CH(3) (3), and (CH(2))(7)CH(3) (4) were synthesized by reaction of the corresponding diamines with nitric oxide. Spectrophotometrically determined pK(a)(O) values, attributed to protonation at the terminal oxygen of the diazeniumdiolate group, show shifts to higher values in dependence of the chain lengths of R. The pH dependence of the decomposition of NO donors 1-3 was studied in buffered solution between pH 5 and 8 at 22 degrees C, from which pK(a)(N) values for protonation at the amino nitrogen, leading to release of NO, were estimated. It is shown that the decomposition of these diazeniumdiolates is markedly catalyzed by anionic SDS micelles. First-order rate constants for the decay of 1-4 were determined in phosphate buffer pH 7.4 at 22 degrees C as a function of SDS concentration. Micellar binding constants, K(SM), for the association of diazeniumdiolates 1-3 with the SDS micelles were also determined, again showing a significant increase with increasing length of the alkyl side chains. The decomposition of 1-3 in micellar solution is quantitatively described by using the pseudo-phase ion-exchange (PIE) model, in which the degree of micellar catalysis is taken into account through the ratio of the second-order rate constants (k(2m)/k(2w)) for decay in the micelles and in the bulk aqueous phase. The decay kinetics of 1-3 were further studied in the presence of cosolvents and nonionic surfactants, but no effect on the rate of NO release was observed. The kinetic data are discussed in terms of association to the micelle-aqueous phase interface of the negatively charged micelles. The apparent interfacial pH value of SDS micelles was evaluated from comparison of the pH dependence of the first-order decay rate constants of 2 and 3 in neat buffer and the rate data obtained for the surfactant-mediated decay. For a bulk phase of pH 7.4, an interfacial pH of 5.7-5.8 was determined, consistent with the distribution of H(+) in the vicinity of the negatively charged micelles. The data demonstrate the utility of 2 and 3 as probes for the determination of the apparent pH value in the Stern region of anionic micelles.