A highly specific and sensitive sandwich enzyme immunoassay for human hemoglobin A

Area of Science:

• Biochemistry
• Immunology
• Forensic Science

Background:

• Accurate identification of human hemoglobin A (Hb A) is crucial for forensic applications.
• Existing methods may lack the specificity or sensitivity required for trace evidence analysis.

Purpose of the Study:

• To develop and validate a highly specific and sensitive sandwich enzyme immunoassay for human hemoglobin A (Hb A).
• To assess the assay's ability to differentiate human Hb A from animal hemoglobins in various sample types, including aged bloodstains.

Main Methods:

• Utilized a sandwich enzyme immunoassay format employing rabbit anti-human Hb A IgG-coated polystyrene balls.
• Employed affinity-purified anti-human Hb A Fab'-horseradish peroxidase conjugates, pre- and post-absorption with animal hemoglobin-Sepharose.
• Quantified bound peroxidase activity via fluorimetry using 3-(4-hydroxyphenyl)propionic acid as a substrate.

Main Results:

• Achieved detection limits of 0.65 pg/tube (3 x 10^10-fold dilution) and 2.0 pg/tube (1 x 10^10-fold dilution) for human Hb A.
• Successfully discriminated human Hb A from various animal hemoglobins based on differential peroxidase activity.
• Demonstrated reliable differentiation of human Hb A in bloodstains, even after multiple washings and high dilutions (up to 220,000-fold).

Conclusions:

• The developed sandwich enzyme immunoassay provides a highly specific and sensitive method for human Hb A detection.
• The assay is effective in distinguishing human Hb A from animal hemoglobins in forensic contexts, including challenging sample matrices.
• This technique holds significant potential for the accurate identification of human blood evidence in forensic investigations.