**3. Results**

#### **3.1. Ion implantation changes the surface roughness and zeta potential of SR**

After ion implantation, SEM, AFM, FTIR, XPS, XRD, water contact angle measure instrument, zeta potential detection instrument, shore A durometer, and an electronic universal testing machine were used to investigate the change in properties of carbon ion silicone rubber. The SEM results failed to find any significant differences between virgin SR and three C-SRs (**Figure 1**), indicating that carbon ion implantation did not change the macroscale surface of SR.

At the same time, there is no any significant differences or the difference was very small on the results of FTIR (**Figure 2**), XRD (**Figure 3**), shore hardness (**Figure 4A**), and tear strength (**Figure 4B**).

**Figure 1.** Representative scanning electron microscopic images of virgin silicone rubber and carbon ion-implanted silicone rubber.

**Figure 2.** The Fourier transform infrared spectroscopy results of virgin silicone rubber and carbon ion-implanted silicone rubber.

**Figure 3.** The XRD results of virgin silicone rubber and carbon ion-implanted silicone rubber.

**Figure 4.** The results of Shore A hardness and tear strength of virgin silicone rubber and carbon ion-implanted silicone rubber. A, Shore A hardness. B, Tear strength.

From the results of water contact angle, we found that carbon ion implantation significantly decreased the water contact angle of SR, and big doses carbon ions had lowest water contact angle among all C-SRs (**Figure 5**).

Besides, the XPS results showed that carbon ion implantation significantly changed the surface silicone oxygen rate and chemical-element distribution of SR (**Figure 6**) (**Table 1**); we noted

**Figure 5.** Water contact angle of virgin silicone rubber and carbon ion-implanted silicone rubber (\*P < 0.05 compared with silicone rubber).

**Figure 6.** XPS results of virgin silicone rubber and carbon ion-implanted silicone rubber.

**Figure 3.** The XRD results of virgin silicone rubber and carbon ion-implanted silicone rubber.

rubber. A, Shore A hardness. B, Tear strength.

silicone rubber.

132 Ion Implantation - Research and Application

**Figure 4.** The results of Shore A hardness and tear strength of virgin silicone rubber and carbon ion-implanted silicone

**Figure 2.** The Fourier transform infrared spectroscopy results of virgin silicone rubber and carbon ion-implanted


**Table 1.** Chemical composition (in at.%) from the XPS analysis.

that with the ion implantation dose increasing, the carbon content in the material increased, while the Si content decreased, suggesting that implanted carbon atom may replace the Si of virgin SR, interrupting the original Si-O assemble, increasing the surface free energy, and, thereby, theoretically decreasing material's water contact angle.

Furthermore, AFM images revealed that the surfaces of C-SRs were composed of larger irregular peaks and deeper valleys, while virgin SR exhibited a relatively smooth and more homogeneous surface (**Figure 7A**). The surface roughness of the C3-SR, which underwent most carbon ion implantation, was highest among all three C-SRs (**Figure 7B**).

In addition, all samples exhibited negative zeta potentials and reflect that the surfaces of all samples were negatively charged. The absolute value of the zeta potential increased with the ion dose (**Figure 8**). Considering the influence of surface roughness on contact angle, we propose that ion implantation can change the surface roughness of the material and increase the surface potential of the material.

#### **3.2. Ion implantation inhibits bacterial adhesion on SR**

Preventing bacterial adhesion and biofilm formation by improving the surface antibacterial adhesion property of the silicone rubber is critical for eliminating various types of infections.

**Figure 7.** AFM results of virgin silicone rubber and carbon ion-implanted silicone rubber. A, Representative atomic force microscope images. B, Surface roughness (\*P < 0.01 compared with silicone rubber).

**Group Si 2p C 1s O 1s** SR 28.82 47.57 23.65 C1-SR 18.94 58.40 22.67 C2-SR 18.96 58.44 22.60 C3-SR 18.13 61.49 20.38

that with the ion implantation dose increasing, the carbon content in the material increased, while the Si content decreased, suggesting that implanted carbon atom may replace the Si of virgin SR, interrupting the original Si-O assemble, increasing the surface free energy, and,

Furthermore, AFM images revealed that the surfaces of C-SRs were composed of larger irregular peaks and deeper valleys, while virgin SR exhibited a relatively smooth and more homogeneous surface (**Figure 7A**). The surface roughness of the C3-SR, which underwent most

In addition, all samples exhibited negative zeta potentials and reflect that the surfaces of all samples were negatively charged. The absolute value of the zeta potential increased with the ion dose (**Figure 8**). Considering the influence of surface roughness on contact angle, we propose that ion implantation can change the surface roughness of the material and increase

Preventing bacterial adhesion and biofilm formation by improving the surface antibacterial adhesion property of the silicone rubber is critical for eliminating various types of infections.

**Figure 7.** AFM results of virgin silicone rubber and carbon ion-implanted silicone rubber. A, Representative atomic force

microscope images. B, Surface roughness (\*P < 0.01 compared with silicone rubber).

**Table 1.** Chemical composition (in at.%) from the XPS analysis.

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the surface potential of the material.

thereby, theoretically decreasing material's water contact angle.

**3.2. Ion implantation inhibits bacterial adhesion on SR**

carbon ion implantation, was highest among all three C-SRs (**Figure 7B**).

**Figure 8.** The zeta potential of virgin silicone rubber and carbon ion-implanted silicone rubber (\*P < 0.05 compared with silicone rubber; \*\*P < 0.01 compared with silicone rubber).

After ion implantation, we used Gram-negative *Escherichia coli* (American Type Culture Collection 25922) to evaluate the ability to resist bacteria adhesion. From the result, after 1 h of incubation, the rate of *E. coli* adherence on the carbon ion silicone rubber (1 × 1015 carbon ions/cm<sup>2</sup> ; 3 × 10<sup>15</sup> carbon ions/cm<sup>2</sup> ; and 1 × 10<sup>16</sup> carbon ions/cm<sup>2</sup> ) increased to approximately 11, 25, and 33%, respectively, and that on carbon ion silicone rubber increased significantly after 1 h of incubation (**Figure 9**) (*P* < 0.05).

After 24 h of incubation, the rates of bacterial adherence were slightly lower, but did not significantly decrease compared with that after 1 h of incubation (*P* > 0.05). The ability of carbon ion silicone rubber to prevent viable bacteria colonization was also verified by fluorescence staining. The results had shown that the amount of bacterial adhesion to the surface of carbon ion silicone rubber was reduced compared with the virgin silicone rubber (**Figure 10**). Scanning electron microscopy was performed to examine the attached bacteria. As the results

**Figure 9.** The antiadhesion rates (%) of virgin silicone rubber and carbon ion-implanted silicone rubber. After all samples were cultured in bacterial suspension for 1 and 24 h, bacteria on the surface of all samples were recultured on the plate, and bacterial colonies were subsequently counted. According to the number of colonies, the antiadhesion rates (%) for *E. coli* were calculated. The data are presented as the mean ± SD (n = 3); \**P* < 0.05 compared with silicone rubber.

**Figure 10.** Representative images of fluorescence staining and scanning electron microscopy observation of virgin silicone rubber and carbon ion-implanted silicone rubber. Representative images showing bacteria viability on SR and CSR after 24 h of incubation, as indicated by staining with a LIVE/DEAD BacLight Bacterial Viability Kit (Thermo Fisher Scientific, Waltham, Mass). The live bacteria appear green, whereas the dead bacteria are red (original magnification, × 200). Representative scanning electron microscopic images of the bacteria on SR and CSR after incubation for 24 h.

have shown that bacteria were observed on surfaces of all samples, but there were differences in quantity (**Figure 10**).

#### **3.3. Carbon ion‐implanted silicone rubber triggers thinner and weaker tissue capsules**

After ion implantation, the host responses were evaluated by surveying inflammation and fibber capsule formation that developed after subcutaneous implantation in Sprague-Dawley rats for 7, 30, 90, and 180 days. The thickness values of tissue capsules around the implants were identified from hematoxylin and eosin-stained sections of the peri-implant soft tissues and were analyzed as one of the physiologic responses to implantation. At 7 days after implantation, silicone rubber had the thinnest tissue capsules, and carbon ion silicone rubber had thicker (**Figure 11**) (*P* > 0.05) and weaker tissue capsules. Interestingly, the thickness decreased with longer implantation and increasing carbon ion doses (**Figure 11**). At 180 days after implantation, silicone rubber and C3-SR had the thickest and the thinnest tissue capsules, respectively (**Figure 11**).

In addition, collagen deposition was revealed using Masson trichrome staining. Our results show that collagen gradually became sparser over time and with increasing carbon ion doses. Carbon ion silicone rubber had obviously lower collagen deposition than silicone rubber (**Figure 12**) (*P* < 0.05).

To gain insight into inflammatory foreign body responses and capsule contracture to the samples, major biomarkers CD68, CD4, tumor necrosis factor-α, elastin, and α-smooth muscle Surface Modification of Silicone Rubber by Ion Implantation to Improve Biocompatibility http://dx.doi.org/10.5772/intechopen.68298 137

**Figure 11.** The capsule thicknesses around the implants.

**Figure 10.** Representative images of fluorescence staining and scanning electron microscopy observation of virgin silicone rubber and carbon ion-implanted silicone rubber. Representative images showing bacteria viability on SR and CSR after 24 h of incubation, as indicated by staining with a LIVE/DEAD BacLight Bacterial Viability Kit (Thermo Fisher Scientific, Waltham, Mass). The live bacteria appear green, whereas the dead bacteria are red (original magnification, × 200). Representative scanning electron microscopic images of the bacteria on SR and CSR after incubation for 24 h.

have shown that bacteria were observed on surfaces of all samples, but there were differences

After ion implantation, the host responses were evaluated by surveying inflammation and fibber capsule formation that developed after subcutaneous implantation in Sprague-Dawley rats for 7, 30, 90, and 180 days. The thickness values of tissue capsules around the implants were identified from hematoxylin and eosin-stained sections of the peri-implant soft tissues and were analyzed as one of the physiologic responses to implantation. At 7 days after implantation, silicone rubber had the thinnest tissue capsules, and carbon ion silicone rubber had thicker (**Figure 11**) (*P* > 0.05) and weaker tissue capsules. Interestingly, the thickness decreased with longer implantation and increasing carbon ion doses (**Figure 11**). At 180 days after implantation, silicone rubber and C3-SR had the thickest and the thinnest tissue

In addition, collagen deposition was revealed using Masson trichrome staining. Our results show that collagen gradually became sparser over time and with increasing carbon ion doses. Carbon ion silicone rubber had obviously lower collagen deposition than silicone rubber

To gain insight into inflammatory foreign body responses and capsule contracture to the samples, major biomarkers CD68, CD4, tumor necrosis factor-α, elastin, and α-smooth muscle

**3.3. Carbon ion‐implanted silicone rubber triggers thinner and weaker tissue capsules**

in quantity (**Figure 10**).

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capsules, respectively (**Figure 11**).

(**Figure 12**) (*P* < 0.05).

**Figure 12.** The collagen density around the implants.

actin were detected using immunohistochemistry. As shown in **Table 2**, all samples present lower expression of CD68, with no significant differences.

The distribution of CD4 in the inflammatory infiltrate, which was induced by the samples, was investigated to further understand the local immunomodulation against these types of materials. The results show that there were many positive staining areas of CD4 in silicone


**Table 2.** Semiquantitative evaluation of CD68 in peri-implant tissue.

rubber after 90 days, but positive staining in the carbon ion silicone rubber decreased with time. After 90 days, CD4 significantly decreased compared with silicone rubber (**Table 3**).

In addition, the expression results of proinflammatory cytokine tumor necrosis factor-α by macrophage cells show that silicone rubber had an obviously positive staining area (**Table 4**).

Furthermore, the positive staining areas of α-smooth muscle actin and elastin have no difference; the positive staining area of α-smooth muscle actin appeared predominantly in silicone rubber than in carbon ion silicone rubber (**Table 5**). Elastin was intensely expressed in silicone rubber, particularly after 30 days (**Table 6**).


**Table 3.** Semiquantitative evaluation of CD4 in peri-implant tissue.




**Table 5.** Semiquantitative evaluation of α-SMA in peri-implant tissue.


**Table 6.** Semiquantitative evaluation of elastin in peri-implant tissue.
