Protein-Derived Carbon Dots: Effects of Synthesis Parameters on Retained Protein Function

Novel-protein-derived carbon dots have recently been reported with high biocompatibility, superior spatial resolution, photobleaching resistance, customizability, and no post-synthesis conjugation requirement. These nanoparticles bring new capabilities in bioimaging and targeted therapeutics. Protein-based carbon dots contain a carbon core and surface groups from the protein that can retain molecular recognition properties. In this work, a systematic study of synthesis conditions to tune nanoparticle protein function is presented. Bovine serum albumin is used as the model protein to simulate what synthesis parameter alterations yield valuable changes to nanoparticles such as red-shifted photoluminescence, specific size distribution, and surface chemistry functionalization. The dissociation constant, K_D is also calculated, for model BSA-derived NPs and simulated the 1:1 protein-ligand binding at equilibrium. It is found that increased temperatures generally led to higher quantum yields and more red-shifted CDs believed to be due to larger diameters, while nitrogen doping decreased. However, when using microwave radiation, generally NPs are larger and has a 2.5–4.4% increase in nitrogen, resulting in the most red-shifted and highest quantum yield samples. Oven samples possessed 1.6–17.5x lower K_D compared to microwave samples. Understanding the effects of these parameters on CD characteristics enables scientists to rationally design CDs properties for specific applications.