Description
Surface-functional biosensor recognition ligand designed for selective detection of cortisol, supplied as a thiol-modified DNA aptamer for direct immobilization on gold and thiol-reactive sensor surfaces. Engineered for controlled probe orientation, high binding specificity, and stable integration into electrochemical and microfluidic biosensor platforms. For Research Use Only (RUO).
Product Description
The ProbeSeq Cortisol BiosensorProbe™ is a thiol-functionalized single-stranded DNA aptamer engineered for selective recognition and capture of cortisol, a steroid hormone widely used as a biomarker for stress response, endocrine function, circadian rhythm monitoring, and metabolic regulation. The probe incorporates a terminal sulfhydryl (–SH) functional group enabling controlled covalent immobilization on gold and thiol-reactive sensor interfaces while preserving aptamer folding and target-binding activity.
Cortisol is a small hydrophobic steroid molecule with molecular weight ~362.46 Da secreted by the adrenal cortex. Physiological concentrations typically range from 80–700 nM in serum depending on circadian cycle and may increase significantly under stress conditions. The BiosensorProbe™ enables sensitive surface-based detection of cortisol across physiologically relevant concentration ranges.
The probe is optimized for surface-immobilized sensing environments, enabling dense probe packing (~10¹²–10¹³ molecules/cm² on gold surfaces), controlled orientation, and stable signal generation in electrochemical, optical, and impedance-based detection platforms.
Recognition Mechanism
Target recognition is mediated by a sequence-engineered single-stranded DNA aptamer (~40–60 nucleotides) that forms a defined binding pocket for cortisol through hydrophobic interactions, hydrogen bonding, and conformational folding. Binding induces structural changes suitable for label-free and signal-amplified detection.
Typical equilibrium dissociation constant (Kd): 1–20 nM
Association kinetics: rapid binding within seconds to minutes
Detection capability: nM to µM range depending on sensor platform
The aptamer provides reversible binding suitable for quantitative biosensing and continuous monitoring applications.
Specificity and Selectivity
The Cortisol BiosensorProbe™ demonstrates high molecular specificity toward cortisol with minimal cross-reactivity toward structurally related steroid hormones including cortisone, progesterone, testosterone, and estradiol.
Cross-reactivity: <5% against related steroid hormones
Non-specific adsorption reduction: >90% compared to non-functionalized DNA controls
Matrix compatibility: serum, saliva, sweat, and buffer systems
Sequence-driven recognition enables selective detection in complex biological samples.
Molecular Format and Functionalization
Synthetic single-stranded DNA aptamer containing a terminal thiol (–SH) functional group introduced through controlled chemical modification.
Aptamer length: ~40–60 nucleotides
Functional group incorporation: ≥95% thiol modification
Purity: ≥95% (HPLC verified)
End modification: 5′ or 3′ thiol linker (C6 or equivalent)
The probe is chemically stabilized to preserve structural folding and functional group reactivity.
Surface Immobilization Chemistry
The terminal thiol group supports direct immobilization on gold electrodes through formation of self-assembled monolayers via Au–S bonding.
Surface binding strength: ~40–50 kcal/mol Au–S interaction
Typical immobilization time: 30–120 min
Recommended surface density: 1–10 pmol/cm²
Operating pH range after immobilization: 6.5–8.5
Compatible with nanostructured gold, planar gold electrodes, gold nanoparticles, and maleimide-functionalized surfaces.
Compatible Sensor Surfaces
Gold electrodes and nanostructured gold substrates
Gold nanoparticle-modified interfaces
Thiol-reactive polymer coatings
Maleimide-functionalized surfaces
Electrochemical and impedance sensors
Microfluidic lab-on-chip platforms
Wearable sensing interfaces
Performance Characteristics
Binding affinity (Kd): 1–20 nM
Surface coverage: 10¹²–10¹³ molecules/cm²
Operating temperature range: 4–45°C
Low non-specific adsorption on gold surfaces
Stable signal response over repeated measurement cycles
Stability
The Cortisol BiosensorProbe™ is chemically stabilized to maintain aptamer conformation and thiol reactivity.
Shelf stability: ≥12 months at −20°C
Working stability after immobilization: ≥7–14 days depending on surface conditions
Thermal stability: stable up to ~60°C for short exposure
Storage
Store at −20°C in supplied buffered formulation (10 mM Tris, 1 mM EDTA, pH 7.4 or equivalent). Avoid repeated freeze–thaw cycles and prolonged exposure to oxidizing conditions. Store protected from light.
Applications
Stress biomarker detection
Wearable biosensor development
Endocrine monitoring research
Salivary and sweat biomarker sensing
Electrochemical biosensor platforms
Microfluidic diagnostic devices
Continuous health monitoring systems
