In Situ One-Step Direct Loading of Agents in Acrylic-Based Coatings Deposited by Aerosol-Assisted Open-Air Plasma for Controlled Release Application

In biotechnology, coatings containing bioactive agents are used to modulate biomaterials surface properties while sustaining their bulk properties. Furthermore, the possibility of controlling the loaded agent and its release kinetic makes these coatings attractive platforms to trigger specific interactions, as cell-growth control or antibacterial properties. Such systems are commonly produced by “wet” chemistry. However, innovative chemical vapor deposition processes remain actively studied for producing more rapidly and cost-efficiently these coatings with further an enhanced stability. In this context, aerosol-assisted atmospheric pressure plasma deposition has emerged as a promising strategy for directly depositing coating containing bioactive agents [1]. In a previous study, the feasibility of a direct agents loading in a polymeric coating deposited by aerosol-assisted open-air plasma has been demonstrated [2]. In fact, by using an original strategy of precursors injection, aerosols of precursor are mixed <i>in-situ</i>, in an argon flow, with aqueous aerosols, and injected into an open-air dielectric barrier discharge, inducing the plasma polymerization. This in-flight loading of water droplets inside precursor ones allows fine-tuning of the coating morphology and loaded agent quantity, by controlling several parameters, <i>e.g.</i> flow rate, treatment time.<br/>In this work, the deposition of such coatings was investigated using various promising precursors for drug release system such as acrylic acid (AA), methacrylic anhydride (MA), and 1,4-butanediol diacrylate (BDA). The impact of adding ethanol to the precursor solutions on the deposition and agent entrapment was investigated. The coating morphology was observed by scanning electron microscopy, and the surface wettability assessed by contact angle. The deposition and agent entrapment were evaluated by dissolving CuSO₄ or fluorescent Lucifer Yellow (LY) in the aqueous aerosols. The compounds distributions in the coatings were observed by energy-dispersive X-ray spectrometry and confocal microscopy, respectively. The coatings loaded with LY were also immersed in water and the progressive LY release quantified by fluorescence measurements. The LY total released was used to estimate the initial entrapped LY amount, whereas the Cu one was estimated by thermogravimetric analysis.<br/>Results showed that, for all precursors used herein, the agents dissolved in the aqueous aerosol, were successfully entrapped in the final coatings. The quantifications evidenced that using water-soluble precursor promoted the amount of entrapped agents. However, ethanol addition has allowed to use hydrophobic precursors and to entrap more agents, while also affecting the coating morphology, when comparing to deposition done without ethanol. The release behavior has been further investigated over time up to 4 weeks. The results displayed that the release kinetic was strongly dependent on the precursors. In fact, releases from over minutes to weeks have been achieved for AA and MA, respectively, while almost no release was found with BDA. These different behaviors regarding the release kinetic were correlated to the coating degradation rates, wettability, and degree of crosslinking.<br/>All these results demonstrated that this innovative approach has the potential to entrap a tunable amount of any water-soluble agent without altering its activity. Furthermore, this strategy allowed to control the kinetic release by using different acrylate-based precursors or plasma parameters. Therefore, this <i>in-situ</i> one-step direct loading of agents in polymeric coating deposited by open-air plasma appears as a promising and powerful process to deposit coating for drug-release application.<br/>[1] Palumbo, et. al – Coatings 10 (2020) 440<br/>[2] Morand, et. al – Polymers 13 (2021) 1931