Ethylene glycol assisted preparation of Ti4+-modified polydopamine coated magnetic particles with rough surface for capture of phosphorylated proteins

Profiling the differential phosphoproteome between breast milk and infant formula through a titanium (IV)-immobilized magnetic nanoplatform

Breast milk (BM) fulfills the nutritional needs of infants and sets the standard for infant formula (IF). However, profiling the differential phosphoproteome between BM and IF remains unclear. Herein, a titanium (IV) (Ti4+)-immobilized magnetic nanoplatform (Fe3O4@GO@PDA-Ti4+) was constructed by self-assembly polymerization of dopamine on magnetic graphene oxide, followed by immobilizing Ti4+ through chelation for phosphopeptide enrichment. Fe3O4@GO@PDA-Ti4+ possessed outstanding selectivity (1/1000, a molar ratio of β-casein digests to bovine serum albumin digests) and favorable sensitivity (2.5 fmol/μL), along with rapid magnetic separation. Excellent phosphopeptide capture efficiencies were obtained for BM and IF using Fe3O4@GO@PDA-Ti4+ as an adsorbent coupled with liquid chromatography-mass spectrometry/mass spectrometry. There were 191 and 239 phosphopeptides found in BM and IF, respectively, with 36 phosphoproteins identified in both. However, BM and IF shared only 17 phosphopeptides and 4 phosphoproteins. The variation in the phosphoproteome between BM and IF provides valuable insights into the optimization of IF humanization.

Ionic liquid modification of metal-organic framework endows high selectivity for phosphoproteins adsorption

Zr-based metal-organic framework, UiO-66-NH₂, provides favorable adsorption capacity to phosphoproteins, however, it exhibits obvious nonspecific adsorption to other proteins. In the present work, we report a facile strategy to reduce the nonspecific adsorption of nonphosphoproteins by modifying UiO-66-NH₂ with imidazolium ionic liquids (ILs). With respect to bare UiO-66-NH₂, the modified counterpart, UiO@IL, exhibits much improved selectivity to phosphoproteins while maintains comparable adsorption performance. The surface of UiO@IL presents a strong hydrophilicity due to the modification of ILs. Hydrophobic and electrostatic interaction between the absorbent and nonphosphoprotein is significantly reduced. In addition, the interaction between imidazole group of ILs moiety and phosphate group in phosphoprotein ensures the favorable adsorption capacity of UiO@IL for phosphoproteins. Anionic moieties of ILs, i.e., Cl^-, Br^-, BF₄^-, CF₃SO₃^-, play negligible effect in the adsorption process. As a representative, phosphoprotein β-casein (β-ca) is selectively enriched at a mass ratio of BSA:β-ca = 100:1. UiO@IL was further applied for the selective enrichment of phosphoprotein in milk.

Preparation and Swelling Behaviors of High-Strength Hemicellulose-g-Polydopamine Composite Hydrogels

Hemicellulose-based composite hydrogels were successfully prepared by adding polydopamine (PDA) microspheres as reinforcing agents. The effects of PDA microsphere size, dosage, and nitrogen content in hydrogel on the mechanical and rheological properties was studied. The compressive strength of hydrogel was increased from 0.11 to 0.30 MPa. The storage modulus G’ was increased from 7.9 to 22.0 KPa. The gaps in the hemicellulose network are filled with PDA microspheres. There is also chemical cross-linking between them. These gaps increased the density of the hydrogel network structure. It also has good water retention and pH sensitivity. The maximum cumulative release rate of methylene blue was 62.82%. The results showed that the release behavior of hydrogel was pH-responsive, which was beneficial to realizing targeted and controlling drug release.

Isolation methods for particle protein corona complexes from protein-rich matrices

Background: Nanoparticles become rapidly encased by a protein layer when they are in contact with biological fluids. This protein shell is called a corona. The composition of the corona has a strong influence on the surface properties of the nanoparticles. It can affect their cellular interactions, uptake and signaling properties. For this reason, protein coronae are investigated frequently as an important part of particle characterization. Main body of the abstract: The protein corona can be analyzed by different methods, which have their individual advantages and challenges. The separation techniques to isolate corona-bound particles from the surrounding matrices include centrifugation, magnetism and chromatographic methods. Different organic matrices, such as blood, blood serum, plasma or different complex protein mixtures, are used and the approaches vary in parameters such as time, concentration and temperature. Depending on the investigated particle type, the choice of separation method can be crucial for the subsequent results. In addition, it is important to include suitable controls to avoid misinterpretation and false-positive or false-negative results, thus allowing the achievement of a valuable protein corona analysis result. Conclusion: Protein corona studies are an important part of particle characterization in biological matrices. This review gives a comparative overview about separation techniques, experimental parameters and challenges which occur during the investigation of the protein coronae of different particle types.

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

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.

Facile synthesis of titanium (IV) ion immobilized adenosine triphosphate functionalized silica nanoparticles for highly specific enrichment and analysis of intact phosphoproteins

Analysis of phosphoproteins always faces the challenge of low stoichiometry, which demands highly selective and efficient enrichment in the initial sample preparation. Here we report our synthesis of the novel titanium (IV) ion immobilized adenosine triphosphate functionalized silica nanoparticles (Ti⁴⁺-ATP-NPs) for efficient enrichment of intact phosphoproteins. The average diameter of Ti⁴⁺-ATP-NPs was about 128 nm with good dispersibility and the saturated adsorption capacity for β-casein was 1046.5 mg/g. In addition, Ti⁴⁺-ATP-NPs exhibited high specificity and selectivity in enriching phosphoproteins from both standard protein mixtures and complex biological samples (non-fat milk, chicken egg white and mouse heart tissue extract) as demonstrated by SDS-PAGE.

A porous graphene sorbent coated with titanium(IV)-functionalized polydopamine for selective lab-in-syringe extraction of phosphoproteins and phosphopeptides

A novel polydopamine coated three-dimensional porous graphene aerogel sorbent carrying immobilized titanium(IV) ions (denoted as Ti⁴⁺@PDA@GA) was fabricated without using an organic solvent. The material is shown to be a viable carbon foam type of monolithic sorbent for selective lab-in-syringe enrichment of phosphoproteins and phosphopeptides. The phosphoproteins can be separated from a sample by aspiration and then bind to the sorbent. The analytes then can be dispensed within 5 min. The weight percent of titanium in the monolith typically is 14%, and the absorption capacities for the model proteins β-casein and κ-casein are 1300 and 1345 mg g^-1, respectively. The absorption capacities for nonphosphoproteins are much smaller, typically 160 mg g^-1 for β-lactoglobulin, 125 mg g^-1 for bovine serum, and 4.8 mg g^-1 for lysozyme. The results demonstrate that the selectivity for phosphoproteins was excellent on multiple biological samples including standard protein mixtures, spiked human blood serum, and drinking milk. The selective enrichment of phosphopeptides also makes the method a promising tool in phosphoproteomics. Graphical abstract Schematic of a polydopamine coated three-dimensional porous graphene aerogel for immobilization of titanium(IV) ions. The material served as a monolithic sorbent for selective enrichment of phosphopeptides and phosphoproteins from biological samples. The enrichment process can be carried out conveniently using a lab-in-syringe way.

Magnetic Nanoparticles: From Design and Synthesis to Real World Applications

The increasing number of scientific publications focusing on magnetic materials indicates growing interest in the broader scientific community. Substantial progress was made in the synthesis of magnetic materials of desired size, morphology, chemical composition, and surface chemistry. Physical and chemical stability of magnetic materials is acquired by the coating. Moreover, surface layers of polymers, silica, biomolecules, etc. can be designed to obtain affinity to target molecules. The combination of the ability to respond to the external magnetic field and the rich possibilities of coatings makes magnetic materials universal tool for magnetic separations of small molecules, biomolecules and cells. In the biomedical field, magnetic particles and magnetic composites are utilized as the drug carriers, as contrast agents for magnetic resonance imaging (MRI), and in magnetic hyperthermia. However, the multifunctional magnetic particles enabling the diagnosis and therapy at the same time are emerging. The presented review article summarizes the findings regarding the design and synthesis of magnetic materials focused on biomedical applications. We highlight the utilization of magnetic materials in separation/preconcentration of various molecules and cells, and their use in diagnosis and therapy.