Unveiling specific nanoparticle-protein interactions via evaporated drops: From molecular recognition to allergen...

Unveiling specific interactions between nanoparticles (NPs) and proteins could benefit a better control of NPs' performance in recognition-based detection, imaging and drug delivery. Herein, we investigated the specific recognition between an aptamer modified gold nanoparticle (Apt-AuNP) and its target protein arginine kinase (AK) through a coffee-ring effect (CRE)-based approach. The evaporated droplets of the Apt-AuNP with AK featured a ring-disk-ring transition with elevated AK concentration and a disk pattern was found when the Apt was saturated by AK. Moreover, the AK concentration versus ring thickness curve below the saturation point was proved to fit in an exponential function, indicating the strong association between the Apt-AuNP and AK. In contrast, the ring thickness above the saturation point fitted in a Gompertz growth model that was similar with the Apt-AuNPs incubated with the nonspecific protein (bovine serum albumin, BSA), suggesting that AK was nonspecifically adsorbed onto the AuNPs. The impact of the specific NP-protein interaction on the translation of CRE into macroscopic patterns was further utilized to identify target food allergen AK by the Apt-AuNPs over nontarget allergens (tropomyosin, ovalbumin and β-lactoglobulin). This work provided new insight into the general NP-protein association process and demonstrated the feasibility of employing CRE as an effective tool to profile the specific interactions between NPs and proteins.