LTCC Packaged Ring Oscillator Based Sensor for Evaluation of Cell Proliferation.

A complementary metal-oxide-semiconductor (CMOS) chip biosensor was developed for cell viability monitoring based on an array of capacitance sensors utilizing a ring oscillator. The chip was packaged in a low temperature co-fired ceramic (LTCC) module with a flip chip bonding technique. A microcontroller operates the chip, while the whole measurement system was controlled by PC. The developed biosensor was applied for measurement of the proliferation stage of adherent cells where the sensor response depends on the ratio between healthy, viable and multiplying cells, which adhere onto the chip surface, and necrotic or apoptotic cells, which detach from the chip surface. This change in cellular adhesion caused a change in the effective permittivity in the vicinity of the sensor element, which was sensed as a change in oscillation frequency of the ring oscillator. The sensor was tested with human lung epithelial cells (BEAS-2B) during cell addition, proliferation and migration, and finally detachment induced by trypsin protease treatment. The difference in sensor response with and without cells was measured as a frequency shift in the scale of 1.1 MHz from the base frequency of 57.2 MHz. Moreover, the number of cells in the sensor vicinity was directly proportional to the frequency shift.

High resolution monitoring of chemotherapeutic agent potency in cancer cells using a CMOS capacitance biosensor.

Monitoring cell viability and proliferation in real-time provides a more comprehensive picture of the changes cells undergo during their lifecycle than can be achieved using traditional end-point assays. Particularly for drug screening applications, high-temporal resolution cell viability data could inform decisions on drug application protocols that might lead to better treatment outcomes. We describe a CMOS biosensor that monitors cell viability through high-resolution capacitance measurements of cell adhesion quality. The system consists of a 3 × 3 mm2 chip with an array of 16 sensors, on-chip digitization, and serial data output that can be interfaced with inexpensive off-the-shelf components. An imaging system was developed to provide ground-truth data of cell coverage concurrently with data recordings. Results showed the sensor's ability to detect single-cell binding events, track cell morphology changes, and monitor cell motility. A chemotherapeutic assay was conducted to examine dose-dependent cytotoxic effects on drug-resistant and drug-sensitive cancer cell lines. Concentrations higher than 5 µM elicited cytotoxic effects on both cell lines, while a dose of 1 µM allowed discrimination of the two cell types. The system demonstrates the use of real-time capacitance measurements as a proof-of-concept tool that has potential to hasten the drug development process.

Correlation of Capacitance and Microscopy Measurements Using Image Processing for a Lab-on-CMOS Microsystem.

We present a capacitance sensor chip developed in a 0.35-µm complementary metal-oxide-semiconductor process for monitoring biological cell viability and proliferation. The chip measures the cell-to-substrate binding through capacitance-to-frequency conversion with a sensitivity of 590 kHz/fF. In vitro experiments with two human ovarian cancer cell lines (CP70 and A2780) were performed and showed the ability to track cell viability in realtime over three days. An imaging platform was developed to provide time-lapse images of the sensor surface, which allowed for concurrent visual and capacitance observation of the cells. The results showed the ability to detect single-cell binding events and changes in cell morphology. Image processing was performed to estimate the cell coverage of sensor electrodes, showing good linear correlation and providing a sensor gain of 1.28 ± 0.29 aF/µm2, which agrees with values reported in the literature. The device is designed for unsupervised operation with minimal packaging requirements. Only a microcontroller is required for readout, making it suitable for applications outside the traditional laboratory setting.

Real-Time Measurements of Cell Proliferation Using a Lab-on-CMOS Capacitance Sensor Array.

We describe a capacitance sensor array that has been incorporated into a lab-on-CMOS system for applications in monitoring cell viability. This paper presents analytical models, calibration results, and measured experimental results of the biosensor. The sensor has been characterized and exhibits a sensitivity of 590 kHz/fF. We report results from benchtop tests and in vitro experiments demonstrating on-chip tracking of cell adhesion as well as monitoring of cell viability. Human ovarian cancer cells were cultured on chip, and measured capacitance responses were validated by comparison with images from photomicrographs of the chip surface. Analysis was performed to quantify cell proliferation and adhesion, and responses to live cells were estimated to be 100 aF/cell.