Biomedical Engineering Reference
In-Depth Information
Fig. 7.14
Detection characteristics and readout of the handheld magnetic biosensor. (
a
) Real-time
binding curves of diluted HIV p24 protein at concentrations ranging from 100 ng/mL to 32 pg/mL.
The sensors, functionalized with bovine serum albumin (BSA) as a negative control, gave minimal
signal indicating negligible nonspecific binding of the wash-free assay. (
b
) Calibration curves
for each marker of interest were generated after 15 min of incubation time. The final curve is
subsequently divided into four predetermined concentration ranges and will be presented via color
coded LEDs to the end user. If the signal is undetectable, the indicator light will not be lit. If the
signal is low, medium, or high, then the light indicator will display green, orange, or red light,
respectively. (
c
) To demonstrate the specificity and readout of the device, we functionalized each
of the eight sensors with a different capture antibody. For example, sensor S3 was functionalized
with anti-p24 antibody. When 10 ng/mL of p24 antigen was spiked into the reaction well, only
sensor S3 lit up in the medium concentration regime [
17
]
and the LED for sensor 3 (on the device labeled S3) turned orange, indicating
a moderate level of protein content (Fig.
7.14
b and c). As appropriate, all the other
sensors, functionalized with noncomplementary antibodies, registered no signal.
Similar experiments have been demonstrated with detection of hepatitis C virus
(HCV) capsid protein [
22
], presented in Fig.
7.15
. The combination of a rapid, wash-
free assay and user-friendly display system can help facilitate the rapid adoption of
this platform in both urban centers as well as remote field settings.
Another important consideration for POC applications is that the platform should
be cost-effective. The total cost of each disposable stick (including the antibodies,
magnetic tags, sensors, and assembly) in high volume is less than $3.50 (Table
7.1
),
which means that this diagnostic tool is sufficiently cost-effective to be used in
both developing and developed nations. Furthermore, we believe the cost could be
substantially reduced to less than $1 with slight changes to the sensor array and by
preparing the MNPs in-house.
