(IMCS First Place Best Poster Award) Encapsulation through Photoinitiated Chemical Vapor Phase Deposition (piCVD) for Obtaining Antifouling and Stabilized Biosensing Interface
Authors: Fan Ruolan , Andrew Trisha L. 
Published: July 2021

Biorecognition elements based biosensing devices have been applied in a broad range of clinical applications and are considered of great potential for being transformed into on-site portable techniques due to their high selectivity and sensitivity. Yet, given the success of immobilization methodologies adapted for various sensing platforms, the drive for enhanced surface microenvironments including constant reaction conditions and suppression of nonspecific binding remains. Considering the complexity of the real sensing scenario with various biofoulants (proteins, cells, polysaccharides, etc.), the fast analytes build-up at the interface would cause sensing accuracy to be either false positive or false negative in a short time. While the concern may be alleviated regarding disposable usage, the fragile biocomponent may degrade even on common storage conditions since the temperature, humidity, as well as air quality, keep varying.

Great emphasis has been put on encapsulation techniques to create surface barriers that may simultaneously produce a stable inner environment at the proper humidity and temperature zone and less complicated outer surroundings arising from fouling. However, to compensate for deactivation induced by surface pretreatments and organic solvent used in many widely adopted antifouling techniques, such as spin-coating, layer-by-layer assembly (LbL), surface grafting, etc., high biocomponent loadings are always required. Besides, without precise control over obtaining thin and uniform encapsulation layers, such techniques usually fail to ensure quick mass transfer and accurate data acquisition. Chemical vapor deposition (CVD), on the other hand, is a solvent-free process in which vapor-phase precursors chemically react on a substrate surface to generate uniform films with varying thickness. Previous studies have demonstrated that specific protein-resistant hydrogels can be synthesized via photoinitiated chemical vapor deposition (piCVD) on optical sensors without sacrificing sensitivity and accuracy. However, antifouling layers deposited directly on immobilized biomolecules and used for screening more complicated analytes, such as lysate, have not been investigated.

Herein, antifouling and stabilized interfaces capable of sensitively assaying cell lysate were constructed by depositing ultrathin encapsulation layers on silicon wafers with immobilized nanobodies via piCVD. Since an antifouling mechanism can be either interpreted as solvation barrier induced by hydrophilic groups or presented as easy foulants removal given by the low surface energy nature of hydrophobic materials, poly(hydroxyethyl acrylate) (pHEA) and poly(1H,1H,2H,2H-perfluorooctyl acrylate) (pTFOA) are selected and studied as the representatives of the two groups due to their biocompatibility and multiple synthetic routes. Interestingly, despite significant fouling reduction and stabilized local environments under harsh conditions were achieved by both materials, the compatibility of pTFOA with piCVD was much better than pHEA, which was observed as being more sensitive to the environmental humidity and thus exhibited poor repeatability. Consequently, the piCVD was successfully applied to form an encapsulation layer on “sensitive” substrates to reject unwanted binding and provide constant storage microenvironments, indicating great promise for enhanced biosensing interface fabrication