In this paper we present a CMOS capacitive sensor array as a compact and low-cost platform for high-throughput cell growth monitoring. The proposed biosensor, consists of an array of 8 × 8 CMOS fully differential charge-based capacitive measurement sensors. A DC-input Σ∆ modulator is used to convert the sensors' signals to digital values for reading out the biological/chemical data and further signal processing. To compensate the mismatch variations between the current mirror transistors, a calibration circuitry is proposed which removes the output voltage offset with less than 8.2% error. We validate the chip functionality using various organic solvents with different dielectric constants. Moreover, we show the response of the chip to different concentrations of Polystyrene beads that have the same electrical properties as the living cells. The experimental results show that the chip allows the detection of a wide range of Polystyrene beads concentrations from as low as 10 beads/ml to 100 k beads/ml. In addition, we present the experimental results from H1299 (human lung carcinoma) cell line where we show that the chip successfully allows the detection of cell attachment and growth over capacitive electrodes in a 30 h measurement time and the results are in consistency with the standard cell-based assays. The capability of proposed device for label-free and real-time detection of cell growth with very high sensitivity opens up the important opportunity for utilizing the device in rapid screening of living cells.
This paper presents a novel method for monitoring drug cytotoxicity using a hybrid microfluidic CMOS platform. This platform consists of an array of 8x8 capacitive sensors integrated with a readout circuit on the same chip. In this paper, we present a layer-by-layer (LBL) polyelectrolyte deposition technique to coat the surface of microelectrodes realized in the top most metal layer in 0.35 μm CMOS process. This process successfully enhances the biocompatibility of sensing microelectrodes and consequently increases the cell viability over a three-day period. Herein we demonstrate and discuss the advantage of the proposed platform for drug cytotoxicity as well as cellular growth monitoring. This CMOS sensing platform possesses a wide output dynamic range and allows tracking cell growth at initial cell concentrations ranging from 10 to 200 kCells/ml. We also use a standard Alamarblue cell-based assay and Geneticin selective antibiotic (G418) as control and cytotoxic drugs introduced to non-resistant H1299 and resistant Hek293 cell lines respectively. Furthermore, a low complexity microfluidic packaging technique is presented to create and bond micro-wells on CMOS chip for rapid test and characterization. With the potential to perform label free cellular analysis, the proposed platform opens an avenue to transition from traditional to smart cellular analysis techniques suitable for a variety of biological applications, in particular high throughput cell-based drug testing.
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