While chemiluminescent
optical-fiber sensors present essential
advantages for immunoassays of biomarkers, an inherent limitation
hampering their detection sensitivity is the low collection efficiency
of chemiluminescent emission induced by samples, owing to the microspatial
scale of an optical fiber for transmission of light via total internal
reflection. Here we present a robust approach to overcome this limitation,
based on a uniquely designed all-optical chemiluminescent collection
vial (CC vial) by using a concave mirror and a coaxial tubular mirror
as its bottom and wall, respectively. Using cardiac troponin I (cTnI),
a highly specific but low abundance cardiac biomarker, as the test
sample, we show that accurate assays can be achieved in a wide linear
range of 1–80000 pg/mL. The limit of detection is as low as
0.31 pg/mL, which is about 2 orders of magnitude lower than that obtained
by a normal chemiluminescent optical fiber sensor. The method is successfully
applied for determination of cTnI in real human serum samples with
good accuracy and repeatability. Our study shows that the method can
perform an all-directional collection of the chemiluminescent emission,
thus, greatly enhancing the collection efficiency and improving the
sensitivity of the immunoassays. It is also worth mentioning that
the proposed strategy requires neither complex equipment nor additional
chemicals, making it a cost-effective and universal approach for ultrasensitive
detection of trace biomarkers.