Influence of calcium on glucose biosensor response and on hydrogen peroxide detection

International audienceOf small species capable of reaching a platinum working electrode from biological samples, calcium cations have been found to inhibit significantly glucose biosensor responses. The sensitivities to glucose of sensors immersed in carbonate buffer saline solutions decreased when 0.5 mM calcium chloride was added. The degree of inhibition was proportional to the glucose response in the absence of calcium (0-17% of the normalized current). Likewise, sensor sensitivities to hydrogen peroxide decreased, in the 5-90% range, in the presence of 0.5 mM calcium. Bare Pt-Ir wires show a reversible inhibition of hydrogen peroxide sensitivity. This reversible inhibition is directly related to the decrease of hydrogen peroxide oxidation rate at the platinum anode: this has been evidenced, using rotating disk electrodes, by plotting Koutecky-Levich plots. Such inhibition has been found both for free and chelated calcium cations at levels below 1 mM. Several hypotheses for possible reactions between platinum, hydrogen per-oxide and calcium are discussed

A prospective, international phase 2 study of bortezomib retreatment in patients with relapsed multiple myeloma

Multiple myeloma (MM) typically follows a relapsing course with many patients requiring multiple therapies. This single-arm phase 2 study prospectively evaluated the efficacy and safety of bortezomib retreatment in MM patients who had relapsed after achieving at least a partial response (PR) to prior bortezomib-based therapy. Patients aged 18years, with measurable, secretory MM, who relapsed 6months after prior bortezomib treatment were eligible. Patients received up to eight cycles of bortezomib (+/- dexamethasone). The primary endpoint was best confirmed response at retreatment; secondary endpoints included duration of response (DOR), time to progression (TTP), and safety. Adverse events (AEs) were graded by National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0. A total of 130 patients (median of two prior lines of therapy) were enrolled and received retreatment. At retreatment, 28% and 72% of patients received bortezomib and bortezomib-dexamethasone, respectively. Overall response rate was 40%. In patients who achieved PR, median DOR and TTP were 6 center dot 5 and 8 center dot 4months, respectively. Thrombocytopenia was the most common grade 3 AE (35%). Forty percent of patients experienced neuropathy events, which improved and resolved in a median of 1 center dot 5 and 8 center dot 9months, respectively. In conclusion, bortezomib retreatment was effective and tolerable in relapsed MM patients, with no evidence of cumulative toxicities