Novel Ti⁴⁺-Chelated Polyoxometalate/Polydopamine Composite Microspheres for Highly Selective Isolation and Enrichment of Phosphoproteins

Abstract

Selective isolation and enrichment of phosphoproteins play critical roles for identification of biomarkers in biological applications. Herein, a kind of polyoxometalate (P5W30)/polydopamine (PDA) composite microspheres is readily synthesized via an in situ polymerization way, followed by immobilization of Ti4+ on the surface of the microspheres to obtain P5W30/PDA-Ti4+. Due to metal affinity and π stacking interaction, this novel material exhibits high selectivity to β-casein (β-ca), and the theoretical maximum adsorption capacity is as high as 1250 mg g–1, fitting well with the Langmuir model. The captured β-ca can be collected by using Britton–Robinson (B–R) buffer at pH 7.0, and a recovery of 81.5% is acquired. The enrichment factor is over 150 at a mass ratio of BSA/β-ca = 100:1, indicating that phosphoproteins can be purified by P5W30/PDA-Ti4+. Moreover, the application of P5W30/PDA-Ti4+ as sorbent in real biological samples has been investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis, and the consequences show that this kind of material is able to selectively isolate phosphoproteins from complex samples such as drinking milk and chicken egg white.

Titanium dioxide‐functionalized dendritic mesoporous silica nanoparticles for highly selective isolation of phosphoproteins

“…As shown in Supporting information Fig. S1B, two peaks at 458.7 and 464.4 eV are attributed to Ti 2p 3/2 and Ti 2p 1/2 , respectively [10]. The above results demonstrate the successful preparation of DMSNs‐TiO 2 .…”

“…As shown in the SDS‐PAGE results (Fig. 5), the protein bands identified in the original diluted defatted milk (Lane 2) are mainly ascribed to phosphoproteins (α‐casein [α‐ca] and β‐ca) and nonphosphoproteins (BSA, β‐lactoglobulin (β‐Lg) and α‐lactalbumin [α‐La]) [10, 46]. After treatment with DMSNs‐TiO 2 , a distinct decrease in the bands of α‐ca and β‐ca are observed, while the other coexisting nonphosphoproteins bands exhibit no obvious changes (Lane 3).…”

“…5), the protein bands identified in the original diluted defatted milk (Lane 2) are mainly ascribed to phosphoproteins (α-casein [α-ca] and β-ca) and nonphosphoproteins (BSA, β-lactoglobulin (β-Lg) and α-F I G U R E 5 SDS-PAGE assay results of defatted milk. Lane 1: protein marker (kDa); lane 2: defatted milk after diluted for 25-fold; lane 3: the supernatant of 25-fold diluted defatted milk after treatment with DMSNs-TiO 2 ; lane 4: the eluent; lane 5: standard β-ca of 150 mg/L lactalbumin [α-La]) [10,46]. After treatment with DMSNs-TiO 2 , a distinct decrease in the bands of α-ca and β-ca are observed, while the other coexisting nonphosphoproteins bands exhibit no obvious changes (Lane 3).…”

“…For this purpose, various strategies have been applied for phosphorylated biomolecules separation and enrichment including strong ion-exchange chromatography [6][7][8], immobilized metal ion affinity chromatography (IMAC) [9][10][11][12], and metal oxide affinity chromatography (MOAC) [13][14][15][16]. Among these, MOAC materials have gained increasing popularity due to their excellent structural stability and the reversible chemisorption of phosphate groups on their amphoteric surface with remarkable specificity and less nonspecific binding [17].…”

Polyoxometalate‐Containing Supramolecular Gels

“…[48,49] As a relative strong supramolecular interaction, a coordination bond is also powerful for building POM-containing gels in the presence of transition or rareearth metal ions. [50,51] In this case, the coordination bonds not only form between metal ions with O atoms on the surface of the cluster but also existing metal ions with N atom sourcing from functional groups anchoring on the cluster. At last, in the system possessing host and guest molecules, host-guest inclusion would be the main supramolecular interaction in the POMcontaining supramolecular gels.…”