‘Dirt cheap’ seaweed chips spot disease

RICE (US) — Microsponges derived from seaweed are a key component of a tiny programmable chip designed to sniff out diseases such as HIV and cancer.

The microsponges are 280-micrometer beads of agarose, a cheap, common, lab-friendly material made from seaweed and often used as a matrix for growing live cells or capturing proteins.

“We create an ultrahigh-surface-area microsponge that collects a large amount of material,” says John McDevitt, a professor in bioengineering and chemistry at Rice University. “The sponge is like a jellyfish with tentacles that capture the biomarkers.”

The technology is the focus of six human clinical trials. Details of the work are reported in the journal Small.

The agarose bead is engineered to become invisible in water. “That makes it an ideal environment to capture biomarkers, because the matrix doesn’t get in the way of visualizing the contents. This is a nice use of novel biomaterials that are cheap as dirt, yet yield powerful performance,” McDevitt says.

The beauty of agarose is its ability to capture a wide range of targets from relatively huge protein biomarkers to tiny drug metabolites. In the lab, agarose starts as a powder, like Jell-O. When mixed with hot water, it can be formed into gels or solids of any size. The size of the pores and channels in agarose can be tuned down to the nanoscale.

The chips—called programmable bio-nano-chips, or PBNCs— capture biomarkers found in blood, saliva, and other bodily fluids. The biomarkers are sequestered in the tiny sponges set into an array of inverted pyramid-shaped funnels in the microprocessor heart of the credit card-sized PBNC.

When a fluid sample is put into the disposable device, microfluidic channels direct it to the sponges, which are infused with antibodies that detect and capture specific biomarkers. Once captured, they can be analyzed within minutes with a sophisticated microscope and computer built into a portable, toaster-sized reader.

The challenge, McDevitt says, in developing the technology was defining a new concept to quickly and efficiently capture and detect biomarkers within a microfluidic circuit.

The solution was this network of microsponges with tailored pore sizes and nano-nets of agarose fibers. The sponge-like quality allows a lot of fluid to be processed quickly, while the nano-net provides a huge surface area that can be used to generate optical signals 1,000 times greater than conventional refrigerator-sized devices. The mini-sensor ensembles, he says, pack maximum punch.

McDevitt and colleagues found that agarose beads with a diameter of about 280 micrometers are ideal for real-world applications and can be mass-produced in a cost-effective way. These agarose beads retain their efficiency at capturing biomarkers, are easy to handle and don’t require specialized optics to see.

The agarose bead is engineered to become invisible in water. “That makes it an ideal environment to capture biomarkers, because the matrix doesn’t get in the way of visualizing the contents. This is a nice use of novel biomaterials that are cheap as dirt, yet yield powerful performance,” McDevitt says.

They tested beads with pores up to 620 nanometers and down to 45 nanometers wide. (A sheet of paper is about 100,000 nanometers thick.) Pores near 140 nanometers proved best at letting proteins infuse the beads’ internal nano-nets quickly, a characteristic that enables PBNCs to test for disease in less than 15 minutes.

The team reported on experiments using two biomarkers, carcinoembryonic antigens and Interleukin-1 beta proteins (and matching antibodies for both), purchased by the lab. After soaking the beads in the antibody solutions, the researchers tested their ability to recognize and capture their matching biomarkers. In the best cases, they showed near-total efficiency (99.5 percent) in the detection of bead-bound biomarkers.

Quick and cheap
McDevitt has expected for some time that a three-dimensional bead had greater potential to capture and hold biomarkers than the standard for such tests, the enzyme-linked immunosorbent assay (ELISA) technique. ELISA analyses fluids placed in an array of 6.5-millimeter wells that have a layer of biomarker capture material spread out at the bottom. Getting results through ELISA requires a lab full of equipment, he says.

“The amount of optical signal you get usually depends on the thickness of a sample,” McDevitt says. “Water, for example, looks clear in a small glass, but is blue in an ocean or a lake. Most modern clinical devices read signals from samples in flat or curved surfaces, which is like trying to see the blue color of water in a glass. It’s very difficult.”

By comparison, PBNCs give the researchers an ocean of information. Ultimately, he says, PBNCs will enable rapid, cost-effective diagnostic tests for patients who are ailing, whether they’re in an emergency room, in an ambulance or even while being treated in their own homes. Even better, the chips may someday allow for quick and easy testing of the healthy to look for early warning signs of disease.

Co-authors include researchers at Stanford University, the University of Texas at Austin, and Xavier University. The work was funded by the National Institutes of Health.

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  1. Dr. Wright

    This is great, I hope it continues to be of low cost and available for most people and not something only the elite super rich can have.

  2. Mike Williams

    Dr. Wright, our greatest hope is that this technology will be available at low cost to everyone! We intend for it to revolutionize both the quality and cost of healthcare. Ideally, in the not-too-distant future, people won’t think twice about getting diagnostic tests via PBNCs as part of a routine checkup to find early warning signs of disease, when it’s still highly treatable.

  3. Alex

    Wow! That is phenomenal and life saving!!! Keep up the good work, Dr. McDevitt!

  4. John T. McDevitt

    Dr. Letitia S. Wright, and Alex,

    Thanks for your words of support and encouragement. We are indeed committed to providing better and cheaper healthcare to all sectors of our society as well as on a global basis.

    The field of electronics has already done this type of thing. Thus, we expect and demand better and faster computers and smart cell phones each year at less cost. Unfortunately, the opposite is true for our healthcare. It consumes nearly 17% of our economy and is on the rise.

    We really have no choice but to make healthcare more affordable. Better, cheaper, faster. It won’t happen overnight, but I am confident it will happen if we work together.

    The exciting new science in this area will make it happen soon.

    Thanks again for your interest.

    All the best, John

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