Of Biomarkers and Biosensors
Doctors treating patients with
life-threatening injuries or illnesses need to know practically
at a moment’s notice the presence of certain biomarkers in the
blood that can indicate imminent organ failure of the liver,
kidneys, or heart. The standard procedure to determine these
biomarkers is to draw blood from the patient and perform
extensive testing, sometimes taking up to 90 minutes, as
reported in a recent article in the MIT Technology Review.
Although accurate, the current testing methods do not provide
the immediate results needed for patients whose conditions may
be rapidly deteriorating.
What’s required is a system that can detect
multiple biomarkers simultaneously in the blood and provide the
results in real time at the patient’s bedside. This will enable
doctors to quickly implement necessary life-saving procedures
and treatments based on the patient’s changing conditions. Vista
Therapeutics, a startup company in New Mexico with licensing
agreements from Nanosys and Harvard University, is actively
pursuing such a system based on nanotechnology.
Detecting the biomarkers is accomplished
using sensitive biosensors made up of extremely fine nanowires
having diameters of less than 10 nanometers. The nanowires can
be functionalized or processed to detect any form of bimolecular
interaction that involves proteins or nucleic acids, as stated
on Vista’s website at www.vistatherapeutics.org.
Processing requires the pre-attachment
through covalent bonding of capture molecules such as antibodies
to the nanowire. Charged target molecules in the fluid are
attracted to the capture molecules, producing a change in the
electric field around the nanowire. The resultant current flow
in the nanowire corresponds to the binding and unbinding of
target molecules depending upon their concentration in the
fluid. Each nanowire serves as the gate of an FET. Since
conductance of the nanowire varies with the number of charged
target molecules, monitoring this conductance provides an
accurate indication of the level of the specific functionalized
biomarker. Target molecules can be detected in the range of tens
of proteins/ml.
Sets of nanowires can be processed into
microfluidic chips that have input and output ports for the
fluid to pass through. The chips are manufactured in much the
same way as standard ICs. For bedside use, these chip biosensors
will be located in the patient’s IV line to allow continuous
detection and monitoring of multiple biomarkers.
According to Vista Therapeutics, the market for biosensor
technology currently is estimated to be greater than $3B spread
over a number of commercial and military applications. Topping
the list at $2B is point-of-care clinical settings, followed by
clinical research and trials, and military and bioweapons at
$500M each. Preclinical safety assessment is pegged at $300M
with drug discovery and development at $250M. In terms of
hardware, it is estimated that 7B microfluidic chips will be
needed for patient monitoring and 1B for academic research. In
light of this growing market, combining engineering with
biomedicine could well be an exciting field to consider, not
only for recent graduates, but seasoned professionals as well.
Paul Milo
Editorial Director
pmilo@evaluationengineering.com