Adsorption of Phosphate and Polyphosphate on Nanoceria Probed by DNA Oligonucleotides

Abstract

Phosphate-containing molecules exist in many forms in biology and the environment, and their interaction with metal oxides is an important aspect of their chemistry and biochemistry. In this work, phosphates with different degrees of polymerization (e.g., orthophosphate, pyrophosphate (PPi), sodium triphosphate (STPP), sodium trimetaphosphate (STMP), and polyphosphate with 25 phosphate units) and phosphates with one or two capping groups were studied. CeO nanoparticles (nanoceria) were used as a model metal oxide. DNA is also a polyphosphate, and a fluorescently labeled DNA oligonucleotide was mixed with nanoceria. These phosphate species were individually added to displace the adsorbed DNA. Longer phosphate chains were more efficient when each molecule was used at the same molar concentration, whereas PPi and STPP were most efficient at the same total phosphorus atom concentration. By capping the phosphate with organic groups, the affinity was significantly decreased. Isothermal titration calorimetry (ITC) was also performed to quantitatively measure thermodynamic parameters. Although STMP was very slow at displacing DNA, it was still adsorbed very strongly by nanoceria from ITC, indicating kinetic effects likely due to its ring structure. This observation allowed us to use the DNA as a probe to study the hydrolysis of STMP to form STPP. In summary, this study provides a systematic understanding of phosphate species interacting with metal oxides, and interestingly, it demonstrates an analytical application as well.

Self‐limited Phosphatase‐mimicking CeO2 Nanozymes

“…Since cerium is a hard metal, it also has a strong affinity to phosphate. For example, nanoceria has been used for adsorbing DNA oligonucleotides, and various phosphate containing species . In addition, its phosphatase‐like activity was reported .…”

Phosphate Assay Kit in One Cell for Electrochemical Detection of Intracellular Phosphate Ions at Single Cells

“…These values exhibit the limited conversion of phosphate ions by multiple enzymes, and thus, the control of the egression and the following detection time are critical to obtain the reproducible result. For the specificity of our measurement, various phosphate-containing species, such as pyrophosphate, hexametaphosphate, tripolyphosphate, and ATP, are measured successively using the nanocapillaries (Wang et al, 2018). As shown in Figure S2 (supporting information), no significant charge increase is observed at all these species, exhibiting good specificity of our assay.…”

Isothermal titration calorimetry as a useful tool to examine adsorption mechanisms of phosphate on gibbsite at various solution conditions

“…It is widely used to determine the thermodynamics of biological interactions and has become the gold standard for dissecting the thermodynamics of a biomolecular binding process within a single experiment (Schwarz, Reinisch, Hinz, & Surolia, 2008). However, only very few studies have employed this method to examine the thermodynamics of P adsorption (Appel, Rhue, Kabengi, & Harris, 2013;Miltenburg & Golterman, 1997;Penn & Warren, 2009;Wang, Lopez, & Liu, 2018b). An early related work was reported by Miltenburg and Golterman (1997) who observed an exothermic adsorption of P on ferric hydroxide by using a home-made isothermal calorimetry.…”

“…isothermal titration calorimetry (ITC), Penn and Warren (2009) found both exothermic and endothermic reactions during P adsorption onto kaolinite at pH 4.3 but only exothermic reaction at pH 6.3. Recently, an ITC investigation showed a ΔH of −30 kJ mol −1 and a ΔS of 2.81 J (mol K) −1 for P adsorption on CeO 2 nanoparticles at pH 7.4 with 200 mM NaCl as supporting electrolyte (Wang et al, 2018b). Despite these initial efforts, there is little information available about the thermodynamics of P adsorption on Al (hydr)oxides which are important for P-fixing minerals in soils and sediments.…”

“…The endothermic ΔH indicates an entropy-driven reaction for surface precipitation [i.e., the mechanism (c)]. The P association with mineral surface seem to decrease the number of particles in solution, thus imparting the order of the system and leading to an entropy loss (Wang et al, 2018b). However, an increase in the disorder and entropy due to release of the structured water molecules during ion adsorption (Alam et al, 2018;Wang et al, 2018b) may overcompensate the entropy loss, thereby causing a positive ΔS (Table 1).…”