Design of highly functional antiferritin-immunolatex by hybridization of antiferritin/mixed-PEG polymers onto polystyrene submicroparticles

Pentaethylenehexamine-ended poly(ethylene glycol), N6-PEG comprising N6-PEG-5k (M_n = 6000 g/mol) and N6-PEG-2k (M_n = 2000 g/mol), was employed as a novel blocking agent to formulate stable and highly functional antiferritin-immunolatex (LAmP-s, s denotes antiferritin load). In comparison with the immunolatex complex (LAB-s), which were prepared in a similar manner except for using bovine serum albumin (BSA) as a blocking agent, the LAmP-s complex showed a difference only in the surface charge property, because of the altered surface treatment in the case of the LAmP-s (PEGylation) and LAB-s complexes (BSA covering). However, the nonspecific deposition level of BSA-FITC molecules was remarkably low for the LAmP-s complex. Simultaneously, the LAmP-s complex showed significantly higher reactivity (i.e., a high response yield and a low detention limit) compared to that of the LAB-s complex, not only in phosphate buffer (10 mM, pH = 7.4) but also in 100 % fetal bovine serum (FBS), as measured by the turbidimetric monitoring method. The electrical repulsion between the negatively charged LAB-s complex and the anionic antigen was the primary obstacle in the former case, and the overwhelming nonspecific deposition of contaminants from FBS onto the LAB-s complex, was the main reason in the latter case. Moreover, the PEGylation treatment allowed the LAmP-s complex to possess invariable size and reactivity for at least one month at 4°C without salt, obviously demonstrating that the PEGylation technique is a promising method for constructing sensitive immunoassay systems.