Immobilization of silver ions onto paramagnetic particles for binding and release of a biotin-labeled oligonucleotide

Paramagnetic particles with amino functional groups can be derivatized usin g glutaraldehyde and thiourea in order to immobilize silver ions. The silve r immobilization procedure did not alter the surface morphology of the part icles according to Tapping mode AFM imaging. Rutherford backscattering show ed that silver resides on the particle surface while iron is present throug hout the particle. Particle-Induced X-Ray Emission spectroscopy determined that the derivatized particles have a silver capacity of 7 wt%. Paramagneti c particles containing immobilized silver ions have an affinity binding con stant of the order 10(8) for mono- and tri-biotin-labeled oligonuceotide wi th primary sequence 3'-GCCCCTTTTTAAAAACCCCG-5' while the original amino par ticles have little affinity for the oligonucleotide. Measurement of binding and release was enabled by attaching either fluorescein isothioocyanate (F ITC) to the 3'-end or Texas Red or fluorescein phosphoramidite (FAM) to the 5'-end of the oligonucleotide. Up to a 97% release of the FAM labeled biot inylated oligonucleotide from the particle surface can be achieved using an aqueous solution of thiodiglycol. (C) 2000 Elsevier Science B.V. All right s reserved.