Plasma Deposition\nof Parylene-like Films with Chemical\nFunctional Groups for Immunoassays

Parylene-like films obtained via the plasma decomposition\nof parylene\nprecursors with functional groups (amino and formyl) are proposed\nas an alternative to those obtained via the thermal method. To analyze\nthe chemical functional groups after plasma deposition, a surface\nanalysis of the parylene films using the two different deposition\nmethods was performed via Fourier transform infrared (FT-IR) and X-ray\nphotoelectron spectroscopy (XPS). The FT-IR analysis revealed that\nthe featured peaks of the chemical functional groups were maintained\nin the parylene-like films obtained via the plasma deposition method.\nThe XPS analysis revealed that the featured chemical functional groups\nof parylene-AM and parylene-H were maintained after plasma deposition.\nThe surface energy of the parylene films was estimated by using contact\nangle measurements. The plasma-deposited\nparylene films were then employed for protein immobilization via the\nfunctional groups using horseradish peroxidase (44 kDa) and green\nfluorescent protein (25 kDa) as model proteins. The parylene-AM and\nparylene-H films obtained via plasma deposition exhibited higher immobilization\nefficiencies than did the same parylene films obtained via thermal\ndeposition. Finally, a competitive immunoassay was obtained by immobilizing\nthe Fv-antibodies on plasma-deposited parylene-AM and parylene-H films\nvia covalent bonding. Using heat-deactivated SARS-CoV-2 as a real\nsample, the limit of detection at the feasible level for the medical\ndiagnosis of COVID-19 was achieved using a competitive immunoassay\nbased on immobilized Fv-antibodies on plasma-deposited parylene films.