Effects of Dicationic Imidazolium-Based Ionic Liquid Coatings on Oral Osseointegration of Titanium Implants: A Biocompatibility Study in Multiple Rat Demographics

Abstract

Dicationic imidazolium-based ionic liquids with amino acid anions, such as IonL-phenylalanine (IonL-Phe), have been proposed as a multifunctional coating for titanium (Ti) dental implants. However, there has been no evaluation of the biocompatibility of these Ti coatings in the oral environment. This study aims to evaluate the effects of IonL-Phe on early healing and osseointegration of Ti in multiple rat demographics. IonL-Phe-coated and uncoated Ti screws were implanted into four demographic groups of rats to represent biological variations that could affect healing: young males (YMs) and females (YFs), ovariectomized (OVXFs) females, and old males (OMs). Samples underwent histopathological and histomorphometric analysis to evaluate healing at 7 and 30 days around IonL-coated and uncoated Ti. The real-time quantitative polymerase chain reaction was also conducted at the 2- and 7-day YM groups to evaluate molecular dynamics of healing while the IonL-Phe was present on the surface. IonL-coated and uncoated implants demonstrated similar histological signs of healing, while coated samples’ differential gene expression of immunological and bone markers was compared with uncoated implants at 2 and 7 days in YMs. While YMs presented suitable osseointegration for both uncoated and IonL-Phe-coated groups, decreased success rate in other demographics resulted from lack of supporting bone in YFs and poor bone quality in OVXFs and OMs. Overall, it was found that IonL-coated samples had increased bone-to-implant contact across all demographic groups. IonL-Phe coating led to successful osseointegration across all animal demographics and presented the potential to prevent failures in scenarios known to be challenged by bacteria.

Exogenous Protein Delivery of Ionic Liquid-Mediated HMGB1 Coating on Titanium Implants

“…More cations were observed on the surface due to the net negative charge of the protein (Figure d and e); in particular, more cations are found around the acidic C-terminal tail (see Figure b,c). Figures f,g shows that more anions form hydrogen bonds with the protein compared to cations . From MD contact frequency calculations, it was observed that the atoms of the carboxyl groups of Glu and Asp protein residues are more prevalent around the aromatic regions of the IonL cation (Figure S10–S14).…”

“…Fluids present in biological environments could potentially dissolve an implant coating prior to any beneficial outcomes toward healing. Based on the stability of IonL-coated Ti in a previous subcutaneous rat model study, 72 we can predict that the coating will be temporarily present during the acute inflammatory response that lead to healing. Although previous studies have demonstrated both the biocompatibility and stability of IonL-Phe and IonL-Met in Lewis rats, 72 there have not been any previous studies using IonL as an anchoring thin film for HMGB1.…”

“…Based on the stability of IonL-coated Ti in a previous subcutaneous rat model study, 72 we can predict that the coating will be temporarily present during the acute inflammatory response that lead to healing. Although previous studies have demonstrated both the biocompatibility and stability of IonL-Phe and IonL-Met in Lewis rats, 72 there have not been any previous studies using IonL as an anchoring thin film for HMGB1. To fully understand the impact of IonLs with HMGB1 as coatings (toxicity, biocompatibility, stability, durability, etc.…”

“…Figures 6f,g shows that more anions form hydrogen bonds with the protein compared to cations. 72 From MD contact frequency calculations, it was observed that the atoms of the carboxyl groups of Glu and Asp protein residues are more prevalent around the aromatic regions of the IonL cation (Figure S10 The interaction energy calculated by focusing on electrostatic and van der Waals interactions between IonL ions and protein residues in Figure 6h,i further confirms that the cations strongly interact with the acidic residues of the protein, such as Glu and Asp and the anions strongly interact with the basic residues in the protein, such as Lys and Arg. This indicates that both the cations and anions of IonL distributed around the protein were involved in interactions with oppositely charged amino acid residues.…”

Biological Effects of New Titanium Surface Coatings Based on Ionic Liquids and HMGB1: A Cellular and Molecular Characterization in Lewis Rats

“…Peptide coatings have been used to functionalize surfaces and harness the immune system . Thus, a well-characterized, multifunctional IonL ,,,− , was used as a method to immobilize key immunomodulatory proteins, such as HMGB1, which was previously studied in vitro and in silico by our group. , However, the behavior of this coating after in vivo implantation is still not well known.…”