Fabricating Medical Devices at the Micro- and Nano- Scale

Siyang Zheng and his students use micro- and nano-fabrication technology to create devices to study fundamental biological processes, to improve diagnosis of diseases, and to treat patients in more convenient and economical ways by using miniaturized devices and systems. This all happens in the Micro and Nano Integrated Biosystem Laboratory (MINIBio) in the Department of Bioengineering at The Pennsylvania State University, University Park, PA.

Although Zheng’s lab is equipped with some fabrication tools, he relies on the wider range of tools available in the user facilities of the Penn State Nanofab. The Nanofab is part of the National Nanotechnology Infrastructure Network (NNIN), which is a National Science Foundation-sponsored nationwide network of user facilities to enable rapid advancements in science, engineering, and technology at the nanoscale.


Cancer Detection
Most cancer deaths occur when cancer cells break loose from the original tumor site and migrate through the blood or lymph system to form a new metastatic tumor elsewhere in the body. Starting from his early years at Caltech, Zheng’s recent work has involved creating filters to capture those circulating cells in cancer patients and portable devices to analyze the cells on-chip.

The miniaturized system for viable circulating tumor cell capture.The device consists of a parylene membrane filter sandwiched between two PDMS (plastic) layers. Portholes in the top and bottom allow for syringe inlet and outlet of fluids. Uniformly shaped and spaced 8µ pores capture the circulating cancer cells based on size. In tests using blood samples from patients with various types of cancer – breast, bladder, prostate, colorectal – the micro-device proved superior to the CellSearch system, the only current FDA-approved device on the market. The micro-device detected cancer cells in 27 out of 28 prostate cancer patients, versus 14 for CellSearch, and was similarly better at detecting breast, colorectal, and bladder cancer cells. The device can also identify therapeutic targets directly on the captured cancer cells.


Implantable Micro-Device
A major focus in Zheng’s lab is developing technologies to make implantable micro-devices. One example is a blood pressure sensor to be attached to the left ventricular assist device (LVAD) developed at Penn State Hershey Medical Center. The LVAD helps maintain the pumping action of a heart that is too weak to pump blood on its own. However, sometimes, if a patient’s blood pressure falls too low, the LVAD can become obstructed or cause arrhythmias. One of Zheng’s students, Mingda Zhou, has been working with the Medical Center’s artificial heart team and Dr. Zhiwen Liu’s lab in electrical engineering on a prototype pressure sensor that uses an optical sensing method called a Fabry-Pérot interferometer to help accurately control the pumping of the device.

Zheng is working at the forefront of a field that could help slow the rising tide of medical costs while providing rapid testing for a number of diseases, not the least of which is cancer. His devices will help make possible the dream of personalized medicine, based on a drop of a patient’s blood on a one-centimeter square chip.


Penn State University
University Park, PA
mri.psu.edu

As appeared in the Spring 2011 Focus on Materials bulletin from the Materials Research Institute of Penn State University.