An aptamer based competition assay for protein detection using CNT activated gold-interdigitated capacitor arrays

Area of Science:

• Biotechnology
• Biosensor Technology
• Molecular Recognition

Background:

• Aptamers exhibit specific binding to target molecules or complementary strands.
• Target-bound aptamer complexes show reduced hybridization with complementary strands.
• This property can be leveraged for affinity separation-based protein detection.

Purpose of the Study:

• To develop a sensitive, label-free aptasensor for C-reactive protein (CRP) detection.
• To exploit the competitive binding of aptamers with CRP and complementary RNA (cRNA).
• To immobilize RNA aptamers on carbon nanotube-activated gold interdigitated electrodes for capacitance-based sensing.

Main Methods:

• Immobilization of CRP-specific RNA aptamers on CNT-activated gold electrodes.
• Measurement of capacitance changes upon competitive binding with CRP and cRNA.
• Analysis of binding affinities and sensor response across varying CRP:cRNA ratios.
• Determination of the dynamic detection range for CRP.

Main Results:

• Significant capacitance changes observed with pure CRP/cRNA, decreasing with co-mixtures due to binding competition.
• Capacitance response dramatically lost at a CRP:cRNA ratio of 2:1 due to aptamer dissociation.
• Immobilized aptamers showed strong affinity for pure CRP (Kd=2.4 μM) and cRNA (Kd=1.98 μM), with reduced affinity at a 2:1 ratio (Kd=8.58 μM).
• Dynamic detection range for CRP established as 1-8 μM.

Conclusions:

• The developed aptasensor provides a sensitive, label-free method for protein detection.
• The affinity separation principle based on competitive binding is effective for biosensing.
• This approach has potential for probing molecular interactions and developing diagnostic tools.