HIgG detection by histidine carrying AFM tips (cantilevers)

Area of Science:

• Biotechnology
• Nanotechnology
• Analytical Chemistry

Background:

• Accurate detection of Human Immunoglobulin-G (HIgG) is crucial for diagnosing various medical conditions.
• Existing detection methods may lack sensitivity or require complex sample preparation.
• Atomic Force Microscopy (AFM) offers high-resolution imaging and force measurements at the nanoscale.

Purpose of the Study:

• To develop and characterize a novel AFM-based immunosensor for sensitive HIgG detection.
• To immobilize histidine as a pseudo-specific ligand onto AFM cantilevers.
• To quantify the interaction between the functionalized AFM tips and HIgG in aqueous solutions.

Main Methods:

• AFM cantilevers were functionalized with amino groups via silanization after HNO(3) treatment.
• Histidine molecules were immobilized onto the AFM tips using glutaraldehyde crosslinking.
• Immobilization was confirmed using optical and confocal laser scanning microscopy.
• HIgG detection was performed by measuring the separation distance changes using AFM.
• An alternative Modified Lowry method was used for comparative analysis.

Main Results:

• Optimal conditions for histidine immobilization on AFM tips were established.
• A clear linear correlation was observed between HIgG concentration and the measured separation distance by AFM.
• The developed AFM immunosensor achieved a detection limit as low as 0.055 pmol/µl (8 mg/dl) for HIgG.
• Results from the Modified Lowry method corroborated the AFM-based findings.

Conclusions:

• Histidine-functionalized AFM tips can serve as effective pseudo-specific ligands for HIgG detection.
• The novel AFM immunosensor provides a sensitive and quantitative method for analyzing HIgG concentrations in aqueous media.
• This approach holds potential for developing advanced biosensing platforms for biomolecule detection.