Magneto-impedance based detection of magnetically labeled cancer cells and bio-proteins

A magnetic biosensor with enhanced sensitivity and immobilized magnetic markers is essential for a reliable analysis of the presence of a biological entity in a fluid. Based on conventional approaches, however, it is quite challenging to create such a sensor. We report on a novel magnetic biosensor using the magneto-impedance (MI) effect of a Co-based amorphous ribbon with a microhole-patterned surface that fulfils these requirements. The sensor probe was fabricated by patterning four microholes, each of diameter 2 $\mu $m and depth 2 $\mu $m, on the ribbon surface using FIB lithography. The magnetically labeled Luis Lung Carcinoma (LLC) cancer cells and Bovine serum albumin (BSA) proteins were drop-casted on the ribbon surface, and MI was measured over 0.1 -- 10 MHz frequency range. As the analytes were trapped into the microholes, their physical motion was minimized and interaction among the magnetic fields was strengthened, thus yielding a more reliable and sensitive detection of the biological entities. The presence of magnetically labeled LLC cells (8.25x10$^{\mathrm{5}}$ cells/ml, 10 $\mu $l) and BSA proteins (2x10$^{\mathrm{11}}$ particles/ml, 10 $\mu $l) were found to result in a $\sim$ 2{\%} change in MI with respect to the reference signal.