New ‘lab-on-a-chip’ set to revolutionize early diagnosis of cancer.


Researchers from The University of Kansas have just published an opensource breakthrough paper in the Royal Society of Chemistry journal describing their invention of a miniaturized biomedical testing device for exosomes. The lab-on-a-chip device promises faster result times, reduced costs, minimal sample demands and better sensitivity of analysis when compared with the conventional bench-top instruments now used to examine the tiny biomarkers.

Scientists have been labouring to detect cancer and a host of other diseases in people using promising new exosome biomarkers.  Exosomes are minuscule membrane vesicles, or sacs, released from most, if not all, cell types, including cancer cells.  First described in the mid-’80s, they were once thought to be ‘cell dust,’ or trash bags containing unwanted cellular contents.

However, in the past decade scientists realized that exosomes play important roles in many biological functions through capsuling and delivering molecular messages in the form of nucleic acids and proteins from the donor cells to affect the functions of nearby or distant cells. In other words, this forms a crucial pathway in which cells talk to others.  Exosomes could lead to less invasive, earlier detection of cancer, and sharply boost patients’ odds of survival.

Exosomes run just 30 to 150 nanometers in size. Because of this, exosomes are hard to separate out and test, requiring multiple-step ultracentrifugation, a tedious and inefficient process requires long stretches in the lab, according to scientists.  There aren’t many technologies out there that are suitable for efficient isolation and sensitive molecular profiling of exosomes.  Current exosome isolation protocols are time-consuming and difficult to standardize. Second, conventional downstream analyses on collected exosomes are slow and require large samples, which is a key setback in clinical development of exosomal biomarkers.

A lab-on-a-chip shrinks the pipettes, test tubes and analysis instruments of a modern chemistry lab onto a microchip-sized wafer.  Also referred to as microfluidics technology, it was inspired by revolutionary semiconductor electronics and has been under intensive development since the 1990s. Essentially, it allows precise manipulation of minuscule fluid volumes down to one trillionth of a liter or less to carry out multiple laboratory functions, such as sample purification, running of chemical and biological reactions, and analytical measurement.

In the current study the researchers developed a lab-on-a-chip for early detection of lung cancer, the number-one cancer killer in the U.S. Today, lung cancer is detected mostly with an invasive biopsy, after tumours are larger than 3 centimeters in diameter and even metastatic, according to the KU researchers.  In contrast, their blood-based test is minimally invasive, inexpensive, and more sensitive, thus suitable for large population screening to detect early-stage tumors.  Using the lab-on-a-chip, lung cancer could be detected much earlier, using only a small drop of a patient’s blood.

The prototype lab-on-a-chip is made of a widely used silicone rubber called polydimethylsiloxane and uses a technique called ‘on-chip immunoisolation’.  The team used magnetic beads of 3 micrometers in diameter to pull down the exosomes in plasma samples.  In order to avoid other interfering species present in plasma, the bead surface was chemically modified with an antibody that recognizes and binds with a specific target protein, for example, a protein receptor, present on the exosome membrane. The plasma containing magnetic beads then flows through the microchannels on the diagnostic chip in which the beads can be readily collected using a magnet to extract circulating exosomes from the plasma.

Beyond lung cancer, the team state that the lab-on-a-chip could be used to detect a range of potentially deadly forms of cancer. Adding that the technique provides a general platform to detecting tumour-derived exosomes for cancer diagnosis.

In addition to lung cancer, the researchers also tested for ovarian cancer. In theory, it should be applicable to other types of cancer. The team’s long-term goal is to translate this technology into clinical investigation of the pathological implication of exosomes in tumour development. Such knowledge would help develop better predictive biomarkers and more efficient targeted therapy to improve the clinical outcome.

Source:  The University of Kansas

Integrated microfluidic exosome analysis directly from human plasma. (A) Image of the prototype PDMS chip containing a cascading microchannel network for multi-stage exosome analysis. (B) Streamlined workflow for on-chip immunomagnetic isolation, chemical lysis, and intravesicular protein analysis of circulating exosomes. #1–4 indicates the inlet for exosome capture beads, washing/lysis buffer, protein capture beads, and ELISA reagents, respectively. (C, D) Typical TEM images of exosomes from NSCLC (C) and ovarian cancer plasma (D) isolated by the microfluidic immunomagnetic method. The magnetic beads were conjugated with anti-EpCAM and anti-CA125 antibodies for NSCLC and ovarian cancer, respectively. (E, F) TEM images showing large aggregates (E) and other membranous particles (F) observed in the ultracentrifugation-purified vesicles, as indicated by the white arrows.  Integrated immunoisolation and protein analysis of circulating exosomes using microfluidic technology.  Godwin et al 2014.

Integrated microfluidic exosome analysis directly from human plasma. (A) Image of the prototype PDMS chip containing a cascading microchannel network for multi-stage exosome analysis. (B) Streamlined workflow for on-chip immunomagnetic isolation, chemical lysis, and intravesicular protein analysis of circulating exosomes. #1–4 indicates the inlet for exosome capture beads, washing/lysis buffer, protein capture beads, and ELISA reagents, respectively. (C, D) Typical TEM images of exosomes from NSCLC (C) and ovarian cancer plasma (D) isolated by the microfluidic immunomagnetic method. The magnetic beads were conjugated with anti-EpCAM and anti-CA125 antibodies for NSCLC and ovarian cancer, respectively. (E, F) TEM images showing large aggregates (E) and other membranous particles (F) observed in the ultracentrifugation-purified vesicles, as indicated by the white arrows. Integrated immunoisolation and protein analysis of circulating exosomes using microfluidic technology. Godwin et al 2014.

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