Fabrication and Characterization of Polyelectrolyte Coatings by Polymerization and Co-Deposition of Acrylic Acid Using the Dopamine in Weak Acid Solution

Existing medical materials (such as silicone rubber, glass slides, etc.) fail to meet the functional requirements of biosensing, cell culture, and drug delivery due to their poor wettability. The preparation of polyelectrolyte coatings with excellent wettability and protein adsorption helps broaden the application of medical materials. Poly(acrylic acid) (PAA) is a common polyelectrolyte with stronger protein adsorption, but the existing methods for obtaining PAA coating have certain shortcomings to limit their industrial applications. In this study, dopamine (DA) was used to polymerize and co-deposit acrylic acid (AA) in weak acid solution to functionalize the surface of materials, and the effects of different mass ratios of DA/AA on the wettability and protein adsorption of the coating were deeply investigated. The results demonstrate that PDA/PAA coating is successfully prepared on the surface of four substrates and greatly reduces the water contact angle of these surfaces. Moreover, these coatings show excellent protein adsorption, and the amount of adsorbed protein on the coated QCM chip is increased by 57.74% than the uncoated QCM chip. In addition, the coating has a certain pH responsiveness, and its wettability and protein adsorption are closely related to the pH of the solution. The preparation strategy proposed is simple and substrate-independent, which provides valuable insights into the application of the one-step polymerization and co-deposition strategy under weak acid conditions.

Dual detection high-speed capillary electrophoresis for simultaneous serum protein analysis and immunoassays

Serum protein electrophoresis (SPE) separates serum proteins into bands whose shape and amplitude can alert clinicians to a range of disorders. This is followed by more specific immunoassays to quantify important antigens and confirm a diagnosis. Here we develop a high-speed capillary electrophoresis (HSCE) platform capable of simultaneous SPE and immunoassay measurements. A single laser excitation source is focused into the detection zone of the capillary to measure both refractive index (SPE) and fluorescence signals (immunoassays). The refractive index signal measures characteristic SPE profiles for human serum separated in 100 mM boric acid (pH 10), 100 mM arginine (pH 11), and 20 mM CHES (pH 10). For the immunoassay, the fluorescence electropherograms reveal that CHES provides the optimal buffer for measuring the immunocomplex and separating it from the free antigen. Immunoassays in CHES yield a LOD of 23 nM and a LOQ of 70 nM for the detection of fluorescein. The high pH reduces protein adsorption but reduces antibody affinity. Preliminary studies carried out in 50 mM barbital at pH 8 show improved stability of the immunocomplex and better separation for immunoassay quantification. Further optimization will open new capabilities for measuring orthogonal diagnostic signals in seconds with HSCE.

Superamphiphilic TiO2 Composite Surface for Protein Antifouling

Unwanted protein adsorption deteriorates fouling processes and reduces analytical device performance. Wettability plays an important role in protein adsorption by affecting interactions between proteins and surfaces. However, the principles of protein adsorption are not completely understood, and surface coatings that exhibit resistance to protein adsorption and long-term stability still need to be developed. Here, a nanostructured superamphiphilic TiO2 composite (TiO2 /SiO2 ) coating that can effectively prevent nonspecific protein adsorption on water/solid interfaces is reported. The confined water on the superamphiphilic surface enables a low adhesion force and the formation of an energy barrier that plays a key role in preventing protein adsorption. This adaptive design protects the capillary wall from fouling in a harsh environment during the bioanalysis of capillary electrophoresis and is further extended to applications in multifunctional microfluidics for liquid transportation. This facile approach is not only perfectly applied in channels with complicated configurations but may also offer significant insights into the design of advanced superwetting materials to control biomolecule adhesion in biomedical devices, microfluidics, and biological assays.

On-line polydopamine coating as a new way to functionalize polypropylene fiber sorbent for solid phase extraction

Effective process, including a cartridge packing polypropylene fiber sorbent modified by following on-line polydopamine coating, for on-line solid phase extraction in 2D UHPLC system has been developed. Hydrophobic surface of mechanically stable polypropylene fibers was hydrophilized using an automated and reproducible in situ coating process to enable good wettability and effective extraction of polar compounds. Polymerization mixture consisting dopamine and TRIS buffer was circulated through the cartridge containing polypropylene fibers using a peristaltic pump to achieve polymerization. This process was optimized in terms of dopamine amount in the polymerization mixture, its flow rate, and polymerization time. Best results were obtained with 25 mL polymerization mixture containing 20 mg dopamine circulated through the cartridge at a flow rate of 2.07 mL min^-1 for 60 min. Prepared cartridges were evaluated via measurement of the recovery and reproducibility using chlorogenic acid as a model compound. Overall reproducibility of our multistep process including eight cartridges in 2D UHPLC system, each measured in triplicate, was 3.61% (n = 24).

Dopamine-assisted co-deposition: An emerging and promising strategy for surface modification

Mussel-inspired chemistry based on polydopamine (PDA) deposition has been developed as a facile and universal method for the surface modification of various materials. However, the inherent shortcomings of PDA coatings still impede their practical applications in the development of functional materials. In this review, we introduce the recent progress in the emerging dopamine-assisted co-deposition as a one-step strategy for functionalizing PDA-based coatings, and improving them in the aspects of deposition rate, morphology uniformity, surface wettability and chemical stability. The co-deposition mechanisms are categorized and discussed according to the interactions of dopamine or PDA with the introduced co-component. We also emphasize the influence of these interactions on the properties of the resultant PDA-based coatings. Meanwhile, we conclude the representative potential applications of those dopamine-assisted co-deposited coatings in material science, especially including separation membranes and biomaterials. Finally, some important issues and perspectives for theoretical study and applications are briefly discussed.

Recent advances in protein analysis by capillary and microchip electrophoresis

This review article describes the significant recent advances in the analysis of proteins by capillary and microchip electrophoresis during the period from mid-2014 to early 2017. This review highlights the progressions, new methodologies, innovative instrumental modifications, and challenges for efficient protein analysis in human specimens, animal tissues, and plant samples. The protein analysis fields covered in this review include analysis of native, reduced, and denatured proteins in addition to Western blotting, protein therapeutics and proteomics.