Fluorescence immunoassay system based on the use of a pH-sensitive phase-separating polymer

Area of Science:

• Polymer Chemistry
• Biochemistry
• Analytical Chemistry

Background:

• Immunoassays require efficient separation of reaction products.
• Traditional methods like ELISA can be time-consuming.
• Novel separation carriers are needed to improve assay efficiency.

Purpose of the Study:

• To synthesize and evaluate Poly(N-isopropylacrylamide-co-methacrylic acid) [P(NIPAAm-co-MAA)] as a novel separation carrier for immunoassays.
• To demonstrate the application of this pH-sensitive polymer in competitive and sandwich immunoassays.
• To assess the speed and sensitivity of the P(NIPAAm-co-MAA) based immunoassay.

Main Methods:

• Synthesis of a linear water-soluble, pH-sensitive, phase-separating polymer P(NIPAAm-co-MAA).
• Utilizing the polymer's precipitation below pH 5.8 and redissolution above pH 6.2 at 37°C for reactant separation.
• Application in competitive immunoassay for alpha-fetoprotein determination and sandwich immunoassay for hepatitis B surface antigen determination.

Main Results:

• The P(NIPAAm-co-MAA) polymer facilitated rapid separation of immunoassay products.
• Assay time for alpha-fetoprotein determination was reduced from 100-120 minutes to 30 minutes.
• Sensitivity for alpha-fetoprotein detection was comparable to traditional ELISA, at 0.04 ng/mL.
• Successful application in both competitive and sandwich immunoassay formats.

Conclusions:

• pH-sensitive P(NIPAAm-co-MAA) is an effective and rapid separation carrier for immunoassays.
• This method offers significant time reduction compared to traditional ELISA.
• The technique is versatile and applicable to various immunoassay formats and other separation processes.