Synthesis of size-controlled poly(vinyldiaminotriazine) nanoparticles for enhanced hydrogen bonding adsorption of horseradish peroxidase

Physically adsorbing proteins through functional polymeric nanoparticles hold great potential for a variety of applications. Achieving strong and stable adsorption via hydrogen bonding in aqueous phases is challenging due to the interference from water molecules. The monomer 2-vinyl-4,6-diamino-1,3,5-triazine (VDAT) not only provides donor and receptor sites for hydrogen bonding but also possesses an apolar nature that can help prevent water molecules from interfering with these bonding sites. In this work, poly(vinyldiaminotriazine) nanoparticles (PVDAT) with sizes ranging from approximately 50 nm to 240 nm were synthesized through semi-continuous precipitation polymerization in water. The formation mechanism of PVDAT, including particle nucleation and growth stages, was investigated. VDAT oligomers aggregated to form a core and subsequently grew by adsorbing additional VDAT oligomers. Adsorption studies of PVDAT on horseradish peroxidase (HRP) demonstrated stable physical adsorption facilitated by hydrogen bonding between PVDAT and the enzyme in the aqueous phase. The adsorption of HRP by PVDAT followed the Langmuir model of single-layer adsorption, with a maximum adsorption capacity of 13.80 mg/g and a retention of enzymatic activity of ∼74.99 %. This innovative approach aims to enhance the precision and efficacy of protein separation and extraction, as well as the efficiency of enzyme immobilization.