Page 120 - Read Online

Page 2 of 15 Cheng et al. Soft Sci. 2026, 6, 36

absorption, collectively enhancing the sensing performance. Consequently, the electrospun yarns exhibit a high
sensitivity of 2.08 μA·dec , and the limit of detection (LOD) is theoretically calculated to be 0.4 nmol/L. This
-1
synergistic strategy combines core-shell dual-function nanomaterials with a one-step continuous conjugate
electrospinning technique. It provides an innovative pathway for developing integrated wearable biosensing textiles
for personal real-time stress monitoring and telehealth applications.

INTRODUCTION
Cortisol, a key glucocorticoid hormone , serves as a crucial biomarker for stress and overall homeostatic
[1]
regulation . The increasing global burden of chronic stress highlights the urgent necessity for continuous
[2]
monitoring of cortisol dynamics . Traditional cortisol assessment mainly depends on invasive blood
[3]
sampling, which is inadequate for capturing the fluctuations of cortisol secretion or for achieving long-term
and patient-centered monitoring . Sweat, as a non-invasively accessible biofluid, has attracted substantial
[4]
attention as an alternative analyte for cortisol detection .
[5,6]

Various recognition strategies have been explored for cortisol sensors in sweat analysis, such as antibodies,
DNA aptamers , and molecularly imprinted polymers (MIPs) . Cortisol-antibodies and cortisol-DNA
[7,8]
[9]
aptamers usually suffer from high production costs, susceptibility to denaturation, and limited shelf-life.
MIPs feature molecular-scale cavities that exhibit spatial and chemical complementarity to target analytes,
thereby conferring lock-and-key specificity. This specificity has led to their designation as synthetic
antibodies . Their densely cross-linked polymeric structure imparts high physicochemical robustness,
[10]
enabling stability under extreme pH, in organic solvents, at elevated temperatures, and under high pressure.
The fabrication process involves a single-step copolymerization of functional monomers, cross-linkers, and
template molecules, thereby eliminating the need for animal immunization or cell culture, while offering
considerable cost advantages over biological antibodies and DNA aptamers. The fabrication process relies on
a single-step copolymerization of functional monomers, cross-linkers, and template molecules. Therefore, it
eliminates the need for animal immunization or cell culture. Moreover, this approach offers considerable
cost advantages over biological antibodies and DNA aptamers.

Early MIP-based electrochemical sensors required external, solution-phase redox probes for signal
transduction, such as adding the ferricyanide/ferrocyanide couple into electrolyte solutions . This reliance
[11]
confined their use to laboratory conditions, precluding their applications in continuous monitoring. A
pivotal advancement involved integrating a stable internal transducer with the molecularly imprinted
polymer (MIP). Typical examples include Prussian blue (iron hexacyanoferrate, FeHCF) and its analogues,
such as nickel, copper, and cobalt hexacyanoferrates (named NiHCF, CuHCF, and CoHCF, respectively).
These materials contain the ferricyanide/ferrocyanide redox couple [12,13] .

In this architecture, MIPs are subsequently deposited onto Prussian blue (or its analogues) layers . For
[14]
example, in 2021, Wang et al. pioneered flexible and wearable electrochemical patch-type sensors by
screen-printing Prussian blue slurry onto stretchable Perme-Roll Lite films and then electrodepositing
cortisol-MIP . The flexible patch-type sensors can monitor cortisol secretion in fingertip sweat. The limit of
[15]
detection (LOD) is 0.9 nmol/L, and the sensitivity is 38.8 nA·dec . This breakthrough has enabled
-1
continuous laboratory-free detection of biofluids. High-resolution patterning techniques, such as screen
printing, intaglio transfer printing , and inkjet printing, offer distinct fabrication pathways for biosensors.
[16]

Even so, a key challenge remains in developing truly comfortable, soft, large-scale wearable MIP-based sweat
cortisol sensors. Existing types are mainly presented as patch-type devices , which can cause discomfort,
[17]
hinder natural skin breathability, and exhibit poor long-term adhesion. To overcome these limitations, there