Non-specific protein binding from human plasma and serum has severely hindered the full capabilities of biosensors concerned with cancer biomarker detection. Currently, there is a strong desire for developing new materials which allow for the convenient attachment of an ultra-low fouling and functionalizable surface coating which can be used for highly sensitive and label-free detection of target analytes directly from complex media. In this work, a short 20 min in situ "graft to" protocol using Tris pH 8.5 buffer was developed for zwitterionic carboxybetaine methacrylate (CBMA) polymer conjugates containing the adhesive biomimetic moiety, 3,4-dihydroxy-L-phenylalanine (DOPA), on SiO(2) substrates. Using a surface plasmon resonance (SPR) biosensor, different buffers, pH values, salt concentrations, and temperatures were investigated for determining the "graft to" conditions that yield dense polymer films which both minimize non-specific protein adsorption and maximize antibody immobilization. The optimized surface coatings were shown to be highly protein resistant to 100% human blood plasma and serum. Subsequent antibody functionalized surfaces without any blocking agents enabled the specific detection of the cancer biomarker ALCAM directly from undiluted human serum down to 64 ng/mL. The successful use of this zwitterionic surface coating for detection from complex media on SiO(2) surfaces indicates its potential for broad impacts in the development of implantable medical devices, in vivo diagnostics, and nano-scale biosensors.
"Biofouling or nonspecific protein adsorption remains a challenging problem in biomedical applications, such as bio-separation membranes, biosensors, bio-implants, and drug carriers (Anderson, Rodriguez, & Chang, 2008; Brault et al., 2010; Sun, Yue, Huang, & Meng, 2003). This ubiquitous problem can result in the adhesion of microorganisms or cells in the formation of biofilms on the surface of biomedical devices which can cause microbial infections or thrombosis. "
[Show abstract][Hide abstract] ABSTRACT: Non-fouling materials bind water molecules via either hydrogen bonding or ionic solvation to form a hydration layer which is responsible for their resistance to protein adsorption. Three ionic starch-based polymers, namely a cationic starch (C-Starch), an anionic starch (A-Starch) and a zwitterionic starch (Z-Starch), were synthesized via etherification reactions to incorporate both hydrogen bonding and ionic solvation hydration groups into one molecule. Further, C-, A- and Z-Starch hydrogels were prepared via chemical crosslinking. The non-fouling properties of these hydrogels were tested with different proteins in solutions with different ionic strengths. The C-Starch hydrogel had low protein resistance at all ionic strengths; the A-Starch hydrogel resisted protein adsorption at ionic strengths of more than 10 mM; and the Z-Starch hydrogel resisted protein adsorption at all ionic strengths. In addition, the A- and ZStarch hydrogels both resisted cell adhesion. This work provides a new path for developing non-fouling materials using the integration of polysaccharides with anionic or zwitterionic moieties to regulate the protein resistance of materials.
"One example is to use 3,4-dihy- droxy-L-phenylalanine (DOPA) as the surface anchor group to graft zwitterionic pCB Figure 3. Three approaches to immobilize pCBs onto materials surfaces. to the surface for cancer biomarker detection. Another convenient 'graft-to' strategy was to use hydrophobic–hydrophobic interactions to immobilize polymers onto the substrate, using a triblock copolymer containing a poly(propylene oxide) hydrophobic block and two hydrophilic CB blocks. "
[Show abstract][Hide abstract] ABSTRACT: Zwitterionic polycarboxybetaine (pCB)-based materials have drawn special attention due to their outstanding properties of resisting proteins adsorption, biofilm formation and cell attachment on a variety of substrates and surfaces, reducing the uptake of pCB-coated nanosized materials, as well as providing the capability of further functionalization. Zwitterionic pCBs have been proven to be excellent choices for many applications, not only limited to the field of antifouling. This review will summarize the recent progress on the development of pCB materials and the understanding of the structure-function-property relationships of carboxybetaine materials.
[Show abstract][Hide abstract] ABSTRACT: We show that optimizing EUV yield from laser-heated droplet targets requires matching the pulsewidth to the droplet size if the emission feature is from collisional excitation; it can be longer if the feature is from recombination.
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