Evaluation of the capacitive behavior of 3D carbon electrodes for sub-retinal photovoltaic prosthesis

Here, we evaluate if microfabricated 3D pyrolytic carbon electrodes are suitable for application in sub-retinal photovoltaic prosthesis. This is done by measuring the charge storage capacity (CSC) and the maximum injectable charge, which indicate if the electrodes allow accumulation of sufficiently high charges in the charge cycle and are able to provide sufficiently fast discharge to stimulate neurons, respectively. The CSC was determined to 10.9 mC/cm2 for carbon pillars and 6.4 mC/cm2 for planar carbon electrodes. These values are comparable with values obtained for state-of-the-art electrode materials applied for retinal stimulation such as iridium oxide (IrOx). The maximum injectable charge was determined from cyclic voltammograms (CV) with values of 1.0 and 1.7 mC/cm2 for planar and pillar carbon electrodes, respectively. The measured contact resistance between carbon and n + doped Si confirms that pyrolytic carbon is a possible candidate for integration as a 3D electrode material on photovoltaic silicon retinal implants. The elemental composition of the fabricated pyrolytic carbon pillars was analyzed by X-ray photoelectron spectroscopy (XPS). The analysis showed that the Al2O3 passivated sample with fabricated pyrolytic carbon pillars only contained aluminum, oxygen and carbon, indicating a successful pyrolysis process without any unwanted elements. The study shows promising potential for pyrolytic carbon as a material for 3D electrodes in retinal, photovoltaic implants. Keywords: Retinal prosthesis, Photovoltaic, 3D electrodes, Pyrolytic carbon, Sub-retinal stimulatio

In vivo regulation of interleukin 1β in patients with cryopyrin-associated periodic syndromes

The investigation of interleukin 1β (IL-1β) in human inflammatory diseases is hampered by the fact that it is virtually undetectable in human plasma. We demonstrate that by administering the anti–human IL-1β antibody canakinumab (ACZ885) to humans, the resulting formation of IL-1β–antibody complexes allowed the detection of in vivo–produced IL-1β. A two-compartment mathematical model was generated that predicted a constitutive production rate of 6 ng/d IL-1β in healthy subjects. In contrast, patients with cryopyrin-associated periodic syndromes (CAPS), a rare monogenetic disease driven by uncontrolled caspase-1 activity and IL-1 production, produced a mean of 31 ng/d. Treatment with canakinumab not only induced long-lasting complete clinical response but also reduced the production rate of IL-1β to normal levels within 8 wk of treatment, suggesting that IL-1β production in these patients was mainly IL-1β driven. The model further indicated that IL-1β is the only cytokine driving disease severity and duration of response to canakinumab. A correction for natural IL-1 antagonists was not required to fit the data. Together, the study allowed new insights into the production and regulation of IL-1β in man. It also indicated that CAPS is entirely mediated by IL-1β and that canakinumab treatment restores physiological IL-1β production

Absolute quantification of monoclonal antibodies in biofluids by liquid chromatography-tandem mass spectrometry.

The development of a quantification method for monoclonal antibodies in serum has been accomplished by high-performance liquid chromatography multiple reactions monitoring mass spectrometry. A human monoclonal antibody (HmAb) was used as the model protein for method development and validation. A peptide from the CDR3-region of its heavy chain was selected and used for quantifying the entire mAb. This signature peptide served as a template for the internal standard. Prior to mass spectrometric analysis approximately 50% of the total serum protein content was removed by albumin depletion. The accuracy of the method ranged between 99 and 112% in cynomolgus monkey serum. The intra-assay coefficient of variation (CV) was lower than 4% at 4 microg/mL and 200 microg/mL HmAb (n = 3). The CV at 400 microg/mL corresponded to 9% (n = 3). In addition, the interassay variation was investigated in a male cynomolgus serum pool and in a female cynomolgus serum pool. The CV for the male cynomolgus pool at 4 microg/mL HmAb was 7% (n = 3). The CV obtained from the female pool was 8% (n = 3), at 4 microg/mL. The dynamic range of the method was 3 orders of magnitude. After albumin depletion of 25 microL of serum, a lowest limit of quantification of 2 microg/mL HmAb was reached in both human and cynomolgus monkey samples

The Fatty Acid Desaturation Index in Human Plasma: Comparison of Different Analytical Methodologies for the Evaluation of Dietary Effects

Abstract (252 words) Background: Stearoyl-CoA Desaturase (SCD1) plays a role in the development of obesity and related conditions, such as insulin resistance, and potentially also in neurological and heart diseases. The activity of SCD1 can be monitored using the desaturation index (DI), the ratio of product (16:1n-7 and 18:1n-9) to precursor (16:0 and 18:0) fatty acids. Here we analyzed the DI in the plasma total triglyceride fraction and very low density lipoproteins (VLDL) in volunteers on a high carbohydrate diet using a dual ultra-high pressure liquid chromatography – mass spectrometry (UHPLC-MS) strategy. Methods: One assay was based on a simple extraction followed by neutral loss triglyceride – fatty acid analysis, the other on saponification of triglycerides followed by fatty acid analysis (specific for the position of the double bond within monosaturated fatty acids (MUFA). Both assays were applied to the isolated VLDL or to the plasma total triglyceride fraction. Assays were compared using plasma from a study in which 8 lean and obese healthy individuals received a high carbohydrate diet for 3 days. Results: All assays showed acceptable accuracies (75-125) and precisions (<20%) for the analysis of fatty acids in VLDL and plasma. Analysis of human plasma samples revealed increased DI (up to 136% of control, p< 0.05 after a high carbohydrate diet of 3 days. Conclusion: Only the specific fatty acid UHPLC-MS analysis of human plasma VLDL samples reflects the complete biological pathway and showed that a significant increase in DI and associated SCD1 activity –in healthy individuals after just 3 days of high carbohydrate diet

Early changes in gene expression and inflammatory proteins in systemic juvenile idiopathic arthritis patients on canakinumab therapy

Background: Canakinumab is a human anti-interleukin-1 beta (IL-1 beta) monoclonal antibody neutralizing IL-1 beta-mediated pathways. We sought to characterize the molecular response to canakinumab and evaluate potential markers of response using samples from two pivotal trials in systemic juvenile idiopathic arthritis (SJIA)