In what is being described as a major breakthrough in microfluidics, researchers have created a device that could soon lead to stand alone, self powered chips that can diagnose diseases within minutes.
The technology, developed by researchers from the University of California, Berkeley, Dublin City University and Universidad de Valparaíso Chile, is able to process whole blood samples without the use of external tubing and extra components. The researchers have dubbed the device SIMBAS, which stands for Self powered Integrated Microfluidic Blood Analysis System.
"The dream of a true lab on a chip has been around for a while, but most systems developed thus far have not been truly autonomous," said Ivan Dimov, UC Berkeley post doctoral researcher in bioengineering. "By the time you add tubing and sample prep setup components required to make previous chips function, they lose their characteristic of being small, portable and cheap. In our device, there are no external connections or tubing required, so this can truly become a point of care system."
Schematic of the tether free SIMBAS chip that shows some of the functional elements, such as the blood loading area, the plasma separation microtrenches, detection sites and the suction flow structures.
Professor Luke Lee, the study's principal investigator, added: "This is a very important development for global healthcare diagnostics. Field workers would be able to use this device to detect diseases such as HIV or tuberculosis in a matter of minutes. The fact that we reduced the complexity of the biochip and used plastic components makes it much easier to manufacture in high volume at low cost. Our goal is to address global health care needs with diagnostic devices that are functional, cheap and truly portable."
For the new SIMBAS biochip, the researchers took advantage of the laws of microscale physics to speed up processes that can sometimes take days in a traditional lab. They noted, for example, that the sediment in red wine that usually takes days or years to settle can occur in mere seconds on the microscale.
"The SIMBAS biochip uses trenches patterned underneath microfluidic channels that are about the width of a human hair," said Prof Lee. "When whole blood is dropped onto the chip's inlets, the relatively heavy red and white blood cells settle down into the trenches, separating from the clear blood plasma. The blood then moves through the chip in a process called degas driven flow."
Photograph of the stand alone 1 x 2in SIMBAS chip simultaneously processing five separate whole blood samples by separating the plasma from the blood cells and detecting the presence of biotin, or vitamin B7.
Lee explained that for degas driven flow, air molecules inside the porous polymeric device are removed by placing the device in a vacuum sealed package. When the seal is broken, the device is brought to atmospheric conditions, and air molecules are reabsorbed into the device material. This generates a pressure difference, which drives the blood fluid flow in the chip.
In experiments, the researchers were able to capture more than 99% of the blood cells in the trenches and selectively separate plasma using this method. "This prep work of separating the blood components for analysis is done with gravity, so samples are naturally absorbed and propelled into the chip without the need for external power," said Lee.
The team demonstrated the proof of concept by placing into the chip's inlet a 5microliter sample of whole blood that contained biotin (vitamin B7) at a concentration of about 1 part per 40billion. "That can be roughly thought of as finding a fine grain of sand in a 1700gallon sand pile," said Lee. "We believe the SIMBAS platform could create an effective molecular diagnostic biochip platform for cancer, cardiac disease, sepsis and other diseases in developed countries as well."
