Plasma deposited APTES: A potential film for biomedical application
Graphical abstract
Introduction
In order to endow good mechanical property, tribological property, and biocompatibility to the biomedical implants consisted of metals, polymers or ceramics, the surface modification of such substrates has been widely studied in the past years. Surface functionalization by APTES containing high density of primary amino groups was reported to be a reliable way to bound a protective film with good biocompatibility e.g. (graphene oxide [1], silk fibroin [2], poly(lactic-co-glycolic acid) [3], polylactide [4], CaP composite [5], laminin [6]), construct a biosensor [7], or build a drug delivery system [8], [9]. Due to the protonation of amino groups, bioactive matters, or drug carrying nano/micro-structures could be firmly immobilized on the surface through zwitterionic pairs [10]. Although such chemical has been employed for numerous applications in the biomedical area, scholars seldomly pay attention to the biomedical properties of APTES film. Especially, its biocompatibility including hemolysis, cytotoxicity and so on has not been systematically studied until today.
The most commonly used protocol to functionalize with APTES is to treat the surface in a wet-chemical way [11]. Alternatively, plasma deposition method is reported to show advantages e.g. high reproducibility, high efficiency, higher adhesion strength, etc. [12], [13], [14]. Especially, it has been evidenced in our previous work that higher deposition rate, shorter deposition time and more amino groups were achieved in the plasma deposition [15].
In this work, the APTES film was deposited using the plasma deposition method. A high density of amino groups was achieved by adjusting the gas flow rate of Ar. Furthermore, the biomedical properties of the as-deposited film were investigated.
Section snippets
Deposition of APTES films
A homemade plasma device was used for APTES deposition. The details of such device were described elsewhere [16]. Silicon wafers with a dimension of 8 × 8 × 1 mm were used as substrates. The samples were pre-treated (Ar flow: 10 sccm, voltage: 20 W, pressure: 0.7 mbar, duration: 5 s). Then, a gaseous mixture consisted of 30–90 sccm of active gas Ar and 10 sccm of vector gas Ar carrying APTES was injected into the reaction chamber. The deposition was carried out using a voltage of 40 W and a gas
Results and discussion
FTIR spectra were shown in Fig. 1a, the absorption peak at about 1050, 1450, 1620 and 1750 cm−1 could be indexed to Si-O-/Si-O-Si [18], C-N [12], NH2/NH/CC and CO [19], [20], confirming a successful APTES deposition using plasma. An obvious drop of peak intensity at 1620 cm−1 was seen when Ar flow was higher than 50 sccm, indicating the density of primary amino groups on the surface was decreased. The results of the ellipsometry measurement were demonstrated in Fig. 1b, showing that the film
Conclusions
In conclusion, APTES films were successfully deposited via a plasma deposition method. The density of amino groups was changed by varying Ar flow and the maximum density of 9.03% was achieved at 50 sccm. The as-deposited APTES film could induce the formation of apatite in 14 days’ immersion and show highly stable hydrophilicity (WCAAPTES≈ 21° → WCARinse ≈ 30°–38°), low cytotoxicity level (0), and low hemolysis rate (1.03%), indicating such films could be potentially used to improve the
CRediT authorship contribution statement
Zilin Chen: Formal analysis, Investigation, Writing - original draft, Visualization. Junjie Zhao: Data curation. Chen Jin: Data curation. Yidie Yuan: Funding acquisition. Yongping Zhang: Validation, Supervision. Michaël Tatoulian: Methodology, Resources. Xi Rao: Conceptualization, Methodology, Software, Formal analysis, Investigation, Resources, Writing - original draft, Visualization, Supervision, Project administration, Funding acquisition.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors acknowledge support from National Natural Science Foundation of China (Grant 51801164), the Venture & Innovation Support Program for Chongqing Overseas Returnees (Grant cx2018080) and National Training Program of Innovation and Entrepreneurship for Undergraduates (Grant 201810635068).
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