Abstract
A fluorescent probe for specific biorecognition was prepared by a facile method in which amphiphilic random copolymers were encapsulated with hydrophobic upconversion nanoparticles (UCNPs). This method quickly converted the hydrophobic UCNPs to hydrophilic UNCPs. Moreover, the self-folding ability of the amphiphilic copolymers allowed the formation of molecular imprinting polymers with template-shaped cavities. LiYF4:Yb3+/Tm3+@LiYF4:Yb3+ UCNP with up-conversion emission in the visible light region was prepared; this step was followed by the synthesis of an amphiphilic random copolymer, poly(methacrylate acid-co-octadecene) (poly(MAA-co-OD)). Combining the UCNPs and poly(MAA-co-OD) with the templates afforded a micelle-like structure. After removing the templates, UCNPs encapsulated with the molecularly imprinted polymer (MIP) (UCNPs@MIP) were obtained. The adsorption capacities of UCNPs@MIP bound with albumin and hemoglobin, respectively, were compared. The results showed that albumin was more easily bound to UCNPs@MIP than to hemoglobin because of the effect of protein conformation. The feasibility of using UCNPs@MIP as a fluorescent probe was also studied. The results showed that the fluorescence was quenched when hemoglobin was adsorbed on UCNPs@MIP; however, this was not observed for albumin. This fluorescence quenching is attributed to Förster resonance energy transfer (FRET) and overlap of the absorption spectrum of hemoglobin with the fluorescence spectrum of UCNPs@MIP. To our knowledge, the encapsulation approach for fabricating the UCNPs@MIP nanocomposite, which was further used as a fluorescent probe, might be the first report on specific biorecognition.
Highlights
The encapsulation approach for fabricating the upconversion nanoparticles (UCNPs)@molecularly imprinted polymer (MIP) nanocomposite, which was further used as a fluorescent probe, might be the first report on specific biorecognition
We propose a strategy that utilizes an amphiphilic random copolymer to encapsulate hydrophobic UCNPs, which does not interfere with the original ligands and can self-fold into water-soluble imprint polymers within the cavities of the template
The LiYF4 :Yb3+ /Tm3+ @LiYF4 :Yb3+ UCNPs were synthesized via thermal decomposition
Summary
The results showed that albumin was more bound to UCNPs@MIP than to hemoglobin because of the effect of protein conformation. The results showed that the fluorescence was quenched when hemoglobin was adsorbed on UCNPs@MIP; this was not observed for albumin. 1. Introduction with regard to jurisdictional claims in Upconversion nanoparticles (UCNPs) are trivalent lanthanide (Ln3+ )-doped nanoparticles, which can up-convert two or more lower-energy photons into one high-energy photon [1,2,3,4]. The most common strategies for synthesizing small, monodisperse, and bright UCNPs are coprecipitation, thermal decomposition, and solvothermal syntheses [1,5]. Among these strategies, using oleic acid to cap the UCNP is the most common approach.
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