A sensitive and specific direct competitive enzyme-linked immunosorbent assay (dc-ELISA) was studied in this paper for the detection of di-(2-ethylhexyl) phthalate (DEHP) based on an antigen-coating format. The DEHP-specific polyclonal antibody was raised in rabbits and used to construct the dc-ELISA for the measurement of DEHP. The conjugates of the antibody with horseradish peroxidase (HRP) were used as the detection probe. Under optimal conditions, the assay had a detection limit (LOD) of about 0.0042 ng mL À1 , with an apparent linear range of 10 À3 À10 3 ng mL À1 (R 2 ¼ 0.998). The cross-reactivity with six other structurally related phthalate esters was below 1%. The recoveries of DEHP ranged from 80.8% to 119.2% indicating that the method was successfully applied for the determination of DEHP in infant supplies.

In antibody preparation, the immunogenicity of small molecules is limited due to the instability of adjuvant/hapten emulsions. Nanoparticle-based adjuvants overcome instability and effectively improve immune responses. Immunogenicity and antigenicity are fundamentally important, yet understudied, facets of nanoparticle formulations themselves. Herein, we studied the immunogenicity and antigenicity of nanoparticle formulations. In experiments in a rabbit model, simple inorganic nanoparticle (e.g., gold nanoparticle (AuNP) and silver nanoparticle (AgNP)) immunogens induced higher titers of antiserum. Moreover, several promising nanoparticle drug carrier immunogens (e.g., SiO2, oleylamine graft polysuccinimide (PSIOAm), oleylamine and N-(3-aminopropyl)­imidazole cograft polysuccinimide (PSIOAm‑NAPI), Fe3O4@O-dextran, etc.) showed excellent immunogenicity. Cross-reactivity calculations revealed that the antigenicity properties of AgNP and AuNP antigens are highly size-dependent. Meanwhile, four nanoparticle drug carriers generate antibody-specific immune responses to their antigens. The reactivity of the anti-NP antibodies with nanoparticle antigens was confirmed using immunoassays. This study systematically identified the immunogenicity and antigenicity of the nanoparticle formulation itself. These findings provide insights into the immunological properties of the nanoparticle formulation itself in an organism.