Comparison Between Colloidal Gold and Fluorescence Immunochromatography

• Colloidal Gold (CG): The colloidal gold particles are coupled with antibodies primarily through electrostatic adsorption. This physical binding process is relatively straightforward.

• Fluorescence (FIA): The fluorescent materials (e.g., fluorescent microspheres, quantum dots) are typically coupled with antibodies via chemical conjugation (e.g., covalent bonding). The specific coupling method depends on the properties of the fluorescent substance used. Consequently, the preparation of fluorescent probes is generally more complex and costly than that of colloidal gold probes.

• CG: Relies on the aggregation of gold particles to produce a visible color signal (red/pink). Its sensitivity is limited, usually suitable for qualitative or semi-quantitative detection at the μg/mL to ng/mL level.

• FIA: Utilizes fluorescent signals emitted upon excitation. Fluorescence, being a type of "penetrating light" with signal amplification characteristics, offers significantly higher sensitivity—often at least an order of magnitude higher than CG (potentially reaching pg/mL levels). This makes FIA suitable for semi-quantitative or even fully quantitative analysis when paired with a detector.

• CG: The electrostatic adsorption is susceptible to interference from sample matrices. Factors like overly acidic/alkaline conditions or high salt concentrations can affect the coupling, potentially leading to reduced specificity.

• FIA: The more stable chemical conjugation offers greater resistance to matrix effects, resulting in better specificity for certain detection items.

• CG: Typically produces a single color (red). While different antibodies can be labeled, the similar color signal limits its capability for multiplex detection (simultaneously detecting multiple indicators), usually to a maximum of 2-3 targets due to significant mutual interference.

• FIA: Different fluorescent materials can emit light at different wavelengths (displaying different colors). This allows for multiplex detection using multiple markers on a single test strip, greatly expanding its application range, such as in multi-indicator joint testing panels.

Summary