Silicalite-1 Layers as a Biocompatible Nano- and Micro-Structured Coating: An In Vitro Study on MG-63 Cells

Abstract

Silicalite-1 is a purely siliceous form of zeolite, which does not contain potentially harmful aluminum in its structure as opposed to ZSM-5 aluminosilicate types of zeolite. This paper reports on a study of a silicalite-1 film, deposited on a silicon Si(100) substrate, as a potential anti-corrosive and biocompatible coating for orthopaedic implants. Silicalite-1 film was prepared in situ on the surface of Si(100) wafers using a reaction mixture of tetrapropyl-ammonium hydroxide (TPAOH), tetraethyl-orthosilicate (TEOS), and diH2O. The physico-chemical properties of the obtained surface were characterized by means of X-ray photoelectron spectroscopy, water contact angle measurement, atomic force microscopy, and scanning electron microscopy. The biocompatibility was assessed by interaction with the MG-63 cell line (human osteosarcoma) in terms of cell adhesion, morphology, proliferation, and viability. The synthesized silicalite-1 film consisted of two layers (b- and a, b-oriented crystals) creating a combination of micro- and nano-scale surface morphology suitable for cell growth. Despite its hydrophobicity, the silicalite-1 film increased the number of initially adhered human osteoblast-like MG-63 cells and the proliferation rate of these cells. The silicalite-1 film also improved the cell viability in comparison with the reference Si(100) substrate. It is therefore a promising candidate for coating of orthopaedic implants.

Heat treatment dependent cytotoxicity of silicalite-1 films deposited on Ti-6Al-4V alloy evaluated by bone-derived cells

“…The contact angle values are summarized in Table 2. The contact angle estimated for SF-RT is in good agreement with the previously published value of SFs on the Si(100) substrate 31 . The relatively high value of WCA observed for SF-RT is caused by the enrichment of hydrophobic C-containing species on the outer surface of the sample, as observed by XPS (Table 1).…”

“…While no decrease in the number of Saos-2 cells grown on all SF samples was found, the spreading of cells on all SF samples was slightly but significantly lower than on the reference GS and on stainless steel. Similarly, another study of ours, performed on a different osteosarcoma cell line (MG-63), showed a markedly lower spreading area without a lower density of cells grown on SF-RT than on the reference GS and on reference Si(100) substrates 31 . The lower spreading of both osteosarcoma cell lines grown on SF samples is in accordance with the lower spreading of the non-tumor osteoblastic cell line in the present study.…”

“…As shown in Fig. 1, and from our previous publications, SFs consist of two layers of b-oriented and a, b-oriented crystals forming a combination of the nano-scale and the submicro-scale surface morphology 31 . Nano-structured surfaces in particular, and often also submicro-structured surfaces, are generally preferred Table 2.…”

“…The overall surface morphology of the SFs is therefore the superposition of the surface irregularities of layers I and II. SFs with an analogous morphology were characterized in our previous paper by atomic force microscopy (AFM) 31 . The roughness of the b-oriented crystals of layer I was 11-21 nm (RMS).…”

“…In order to completely eliminate the possibility of aluminum ion release from orthopedic implants into the host body over time, an aluminum-free coating, such as pure-silica MFI (silicalite-1), should be used. Our previous studies have shown good biocompatibility of a silicalite-1 film (SF) deposited on an Si(100) wafer and on stainless steel substrates [30][31][32] . Since the parameters of SFs (e.g.…”