| Nonspecific protein adsorption has been a crucial issue for many biomedical applications, such as medical implants, drug delivery vehicles and biosensors. At present, there are a very limited number of effective nonfouling biomaterials available to meet the challenges of practical applications. Here, zwitterionic materials such as sulfobetaine methacrylate (SBMA), carboxybetaine acrylamide (CBAA) and carboxybetaine methacrylate (CBMA) were systematically introduced, optimized and investigated for their applications as biosensors.Firstly, protein adsorption from single protein solutions and complex media such as 100% blood serum and plasma onto polySBMA-grafted surfaces via atom transfer radical polymerization (ATRP) at varying film thicknesses was investigated. It is interesting to observe that protein adsorption exhibits a minimum at a medium film thickness. Results show that the surface with 62 nm polySBMA brushes presents the best nonfouling character in 100% blood serum and plasma although all of these surfaces are highly resistant to nonspecific protein adsorption from single fibrinogen and lysozyme solutions. Surface resistance to 100% blood serum or plasma is necessary for many applications from blood-contacting devices to drug delivery. This work provides a new in vitro evaluation standard for the application of biomaterials in vivo.Secondly, a zwitterionic polyCBAA biomimetic material was employed to create a unique biorecognition coating with an ultralow fouling background, enabling the sensitive and specific detection of proteins in blood plasma. Conditions for surface activation, protein immobilization, and surface deactivation of the carboxylate groups in the polyCBAA coating were determined. An antibody-functionalized polyCBAA surface platform was used to detect a target protein in blood plasma using a sensitive surface plasmon resonance (SPR) sensor. A cancer biomarker (ALCAM) was directly detected from 100% human blood plasma with extraordinary specificity and sensitivity. The total nonspecific protein adsorption on the functionalized polyCBAA surface was very low (<3 ng/cm2 for undiluted blood plasma). Furthermore, functionalization on polyCBMA-grafted gold or silicon dioxide surfaces was also investigated.Thirdly, nonspecific protein adsorption from single protein solutions and complex media such as undiluted human blood serum and plasma onto polyCBAA-grafted surfaces was investigated. The polyCBAA grafting was done via ATRP with varying film thicknesses at different temperatures. The objective is to create a surface that experiences"zero"protein adsorption from complex undiluted human blood serum and plasma. Results show that protein adsorption from undiluted blood serum, plasma, and aged serum on the polyCBAA-grafted surface is undetectable at both 25°C and 37°C by a SPR sensor. This was achieved with a film thickness of ~20 nm. Further it is demonstrated that the polyCBAA surfaces after antibody immobilized maintain undetectable protein adsorption from undiluted human blood serum.Finally, a new surface platform presenting an abundance of functional groups for ligand immobilization in an ultra-low fouling background necessary for targeted drug delivery and diagnostics was introduced. It is demonstrated that this surface platform, made from zwitterionic polyCBAA coated nanoparticles, is not only stable in undiluted human blood serum, but also can be conjugated to bio-molecules conveniently and effectively. In addition, a practical application was demonstrated by showing the amount of antibodies to a candidate cancer biomarker immobilized onto polyCBAA-coated nanoparticles can be easily adjusted. Results also indicate that 10% serum commonly used to evaluate the stability of nanoparticles is not sufficient and undiluted blood serum is recommended to screen nanoparticles before their in vivo experiments.
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