Anna-Maria Spehar

Heterogeneous and homogeneous electrochemiluminoimmunoassays of hTSH at disposable oxide-covered aluminum electrodes

Heterogeneous and homogeneous immunoassays of human thyroid stimulating hormone (hTSH) were developed on immunometric basis using aromatic Tb(III) chelates as electrochemiluminescent labels and varied types of disposable oxide-covered aluminum electrodes as the solid phase of the immunoassays. The long luminescence lifetime of the present labels allows the use of time-resolved electrochemiluminescence detection and provide the low detection limits of these labels and, thus, sensitive immunoassays. The primary antibody of immunometric immunoassays was coated upon aluminum oxide surface by physical absorption. In homogeneous immunoassays using 66l cell and 15 min incubation time, a linear calibration range of 0.25-324U/ml was obtained by applying only a single cathodic excitation pulse in the detection step of the assay.

Time-resolved electrochemiluminescence of platinum(II) coproporphyrin

Cathodic pulse polarisation of oxide-covered aluminium electrodes can generate electrochemiluminescence (ECL) from metalloporphyrins. This is based on the tunnel emission of hot electrons into aqueous electrolyte solution, which probably results in the generation of hydrated electrons as reducing mediators. These tunnel emitted electrons allow the production of highly reactive radicals, such as sulfate radicals from peroxodisulfate ions, which can induce strong redox luminescence from various organic chemiluminophores including metalloporphyrins. The work presented here illustrates the generation of ECL from platinum(II) coproporphyrin (PtCP) and its bovine serum albumin (BSA) conjugate. This allows the detection of these molecules below nanomolar concentrations and over several orders of magnitude of concentration. The relatively long luminescence lifetime of PtCP allows discrimination from the background ECL signal using time resolved measurements, leading to higher sensitivity and the detection of PtCP-BSA indicates the potential use of metalloporphyrins as labels in ECL-based bioassays such as immunoassays and DNA-binding assays.