Proliferation assay on a silicon chip applicable for tumors extirpated from mammalians

We describe a novel anticancer drug sensitivity assay on a silicon chip applicable for tumors extirpated from in vivo mammalians. Human promyelocytic leukemia (HL-60) cells were subcutaneously (s.c.) inoculated in SCID mice, then removed 31 days after the inoculation. The cells were embedded in a small volume (18 nL) of a collagen-gel matrix on a pyramid-shaped silicon microstructure for further cultivation. The respiration activity of the cells on the chip was measured by scanning electrochemical microscopy (SECM). The proliferation behavior was continuously monitored for 6 days. It seemed that the proliferation rate of the cells removed from the mice was lower than that cultured in a flask and conformed to that in mice. The effects of cisplatin (CDDP) and etoposide (VP-16) on the HL-60 cultured in vivo were in good agreement with those obtained by a conventional colorimetric assay. Our results suggest that the SECM-based assay is appropriate for biopsy specimens in a relatively short-time evaluation.