In vitro plasma protein adsorption on omega-functionalized alkanethiolate self-assembled monolayers

Functionalized self-assembled monolayers (SAMs) of alkanethiolates on gold were used to study citrated human plasma protein adsorption by ellipsometry and antibody techniques in vitro. The aspiration is to gain knowledge about how surface properties affect such events like coagulation and complement activation, which in turn influence cell activation at an implant site. Five functionalities, methyl(-CH3), trifluoromethyl ester (-O(C=O)CF3), sulfate (-OSO3H), carboxyl (-COOH), and hydroxyl (-OH), were subject to characterization by ellipsometry, contact angle measurements, scanning force microscopy (SFM), and Fourier transform infrared reflection-absorption spectroscopy(IRAS). The low-energy surfaces, with methyl and trifluoromethyl ester terminations, showed affinity for fibrinogen. The trifluoromethyl ester also deposited lipoprotein (LP). The sulfate and the carboxyl surfaces deposited the coagulation proteins high molecular weight kininogen (HMWK), factor XII (F XII), and prekallikrein (PK), indicating contact activation of coagulation. Hydroxyl-functionalized SAMs showed low deposition of plasma proteins in general, although a low binding of antibodies against the contact activation proteins, complement factor 3c (C3c), and lipoproteins was observed. The morphology of the formed plasma protein layers was studied using scanning force microscopy. On the low-energy surfaces the proteins tended to cluster into large formations. In the case of the methylated surface the formations had the appearance of dendrite-like networks. On the high-energy surfaces the proteins retained a more uniform spreading in small rounded clusters.