Towards MRI Study of Biointegration of Carbon-Carbon Composites with Ca-P Coatings

Abstract

The development of specific MRI criteria to monitor the implantation process may provide valuable information of individual tissue response. Using MRI and histological methods, the biointegration of carbon-carbon (C-C) composites into the subcutaneous tissues of BDF1 mice and their biocompatibility were investigated. The study focused on autopsy specimens containing C-C composite implants, both uncoated and coated with synthetic hydroxyapatite (Ca-P) via electrodeposition or detonation techniques, assessed at 6 and 12 weeks post-implantation. The results revealed that the radiological characteristics of the connective tissue capsule surrounding the implants allowed for the differentiation between loose and dense connective tissues. Fat-suppressed T1-weighted MRI scans showed that the volume of both loose and dense connective tissue in the capsule increased proportionally at 6 and 12 weeks, with distinct ratios observed between the coated and uncoated specimens. The proposed MRI criteria provided a strategy for evaluating the density and homogeneity of the connective tissue capsule. This approach could be valuable for further non-invasive in vivo studies on implant biointegration.

Keywords: MRI; carbon-carbon medical composites; detonation spraying; electrophoretic deposition; fibrous capsule; hydroxyapatite coatings; radiology studies; tissue response.

Figure 1

SEM images of C-C composite substrate captured at varied magnifications: (A) ×65; (B) ×800; (C) ×500; (D) ×1000.

Figure 2

Ca-P coatings on C-C composite (detonation deposition): (A–C) SEM images; (D) their cross-section; (E) EDX data in indicated spots.

Figure 3

Ca-P coatings on C-C composite (electrophoretic deposition): (A–D) SEM images; (E) EDX data in indicated spots.

Figure 4

Pseudocolored mapping of T1w-TI MR-images (TI prepulse = 100 ms) of the C-C composites: (A) uncoated, 6 weeks; (B) uncoated, 12 weeks; (C) Ca-P coated (electrophoretic deposition), 6 weeks; (D) Ca-P coated (electrophoretic deposition), 12 weeks; (E) Ca-P coated (detonation spraying), 6 weeks; (F) Ca-P coated (detonation spraying), 12 weeks. Fire color filter (Image J/Fiji).

Figure 5

Averaged area of loose (LCT) and dense (DCT) connective tissue of fibrous capsule in autopsy samples taken at 6-week (A) and 12-week (B) post-implantation, with different coatings (uncoated, electrophoretic deposition, detonation spraying) (4 mice per group, number of all analyzed sections N = 18–21). p value < 0.05 is statistically significant for differentiation of loose and dense connective tissue in all samples.

Figure 6

The features of the fibrous capsule for uncoated C-C composites (control) at 6 weeks (A–F) and 12 weeks (G–K) post-implantation are as follows: (A,G) T1-weighted (T1w) MR image of the central section; (B,H) T2-weighted (T2w) MR image of the central section; (C,I) T1w-TI MR image of the central section; (D,E,J,K) hematoxylin and eosin staining of the post-implantation autopsy sample (magnification ×400), where 1 = loose tissue, 2 = dense tissue with fragments of C-C composites, 3 = site of tissue contacts with the implant; (F,L) diagram representing the ratio of loose connective tissue (LCT) to dense connective tissue (DCT) for the entire autopsy sample (number of slices N = 18–21).

Figure 7

The features of the fibrous capsule for C-C composites coated with Ca-P via electrophoretic deposition at 6 weeks (A–F) and 12 weeks (G–K) post-implantation are as follows: (A,G) T1-weighted (T1w) MR image of the central section; (B,H) T2-weighted (T2w) MR image of the central section; (C,I) T1w-TI MR image of the central section; (D,E,J) hematoxylin and eosin staining of the post-implantation autopsy sample (magnification ×400), where 1 = loose tissue, 2 = dense tissue, 3 = site of tissue contacts with the implant; (F,K) diagram representing the ratio of loose connective tissue (LCT) to dense connective tissue (DCT) for the entire autopsy sample (number of slices N = 18–21).

Figure 8

The features of the fibrous capsule surrounding C-C composites coated with Ca-P via detonation spraying at 6 weeks (A–F) and 12 weeks (G–K) post-implantation are as follows: (A,G) T1-weighted (T1w) MR image of the central section; (B,H) T2-weighted (T2w) MR image of the central section; (C,I) T1w-TI MR image of the central section; (D,E,J,K) hematoxylin and eosin staining of the post-implantation autopsy sample (magnification ×400), where 1 = loose tissue, 2 = dense tissue with fragments of C-C composites; (F,L) diagram illustrating the ratio of loose connective tissue (LCT) and dense connective tissue (DCT) for the entire autopsy sample (namber of slices N = 18–21).