Reduced bacterial growth and increased osteoblast proliferation on titanium with a nanophase TiO2 surface treatment

Abstract

Background: The attachment and initial growth of bacteria on an implant surface dictates the progression of infection. Treatment often requires aggressive antibiotic use, which does not always work. To overcome the difficulties faced in systemic and local antibiotic delivery, scientists have forayed into using alternative techniques, which includes implant surface modifications that prevent initial bacterial adhesion, foreign body formation, and may offer a controlled inflammatory response.

Objective: The current study focused on using electrophoretic deposition to treat titanium with a nanophase titanium dioxide surface texture to reduce bacterial adhesion and growth. Two distinct nanotopographies were analyzed, Ti-160, an antimicrobial surface designed to greatly reduce bacterial colonization, and Ti-120, an antimicrobial surface with a topography that upregulates osteoblast activity while reducing bacterial colonization; the number following Ti in the nomenclature represents the atomic force microscopy root-mean-square roughness value in nanometers.

Results: There was a 95.6% reduction in Staphylococcus aureus (gram-positive bacteria) for the Ti-160-treated surfaces compared to the untreated titanium alloy controls. There was a 90.2% reduction in Pseudomonas aeruginosa (gram-negative bacteria) on Ti-160-treated surfaces compared to controls. For ampicillin-resistant Escherichia coli, there was an 81.1% reduction on the Ti-160-treated surfaces compared to controls. Similarly for surfaces treated with Ti-120, there was an 86.8% reduction in S. aureus, an 82.1% reduction in P. aeruginosa, and a 48.6% reduction in ampicillin-resistant E. coli. The Ti-120 also displayed a 120.7% increase at day 3 and a 168.7% increase at day 5 of osteoblast proliferation over standard titanium alloy control surfaces.

Conclusion: Compared to untreated surfaces, Ti-160-treated titanium surfaces demonstrated a statistically significant 1 log reduction in S. aureus and P. aeruginosa, whereas Ti-120 provided an additional increase in osteoblast proliferation for up to 5 days, criteria, which should be further studied for a wide range of orthopedic applications.

Keywords: electrophoretic deposition; infection; nanotopography; titanium dioxide.

Figure 1

SEM images of the (A) untreated titanium, (B) Ti-120, and (C) Ti-160 as well as AFM of (D) untreated titanium, (E) Ti-120, and (F) Ti-160 illustrating the nanoscale surface topography. Abbreviations: SEM, scanning electron microscopic; AFM, atomic force microscopy; RMS, root-mean-square.

Figure 2

S. aureus colony-forming units per milliliter on plain titanium and treated titanium. Notes: Data are expressed as the mean ± standard error of the mean; N=3; *P<0.01 compared with Ti-120 and **P<0.01 compared with Ti-120 and Ti-160. Abbreviation: S. aureus, Staphylococcus aureus.

Figure 3

P. aeruginosa colony-forming units per milliliter on plain titanium and treated titanium. Notes: Data are expressed as the mean ± standard error of the mean; N=3; *P<0.01 compared with Ti-120 and **P<0.01 compared with Ti-120 and Ti-160. Abbreviation: P. aeruginosa, Pseudomonas aeruginosa.

Figure 4

Ampicillin-resistant E. coli colony-forming units per milliliter on plain titanium and treated titanium. Notes: Data are expressed as the mean ± standard error of the mean; N=3; *P<0.01 compared with Ti-120 and **P<0.01 compared with Ti-120 and Ti-160. Abbreviation: E. coli, Escherichia coli.

Figure 5

The root-mean-square (RMS) roughness (as obtained by AFM) of the surface-treated samples plotted against the number of bacterial colonies for all three strains of bacteria; (A) S. aureus, (B) P. aeruginosa and (C) Ampicillin resistant E. coli after 16 hours of culture. Abbreviations: AFM, atomic force microscopy; P. aeruginosa, Pseudomonas aeruginosa; S. aureus, Staphylococcus aureus; E. coli, Escherichia coli.

Figure 6

Osteoblast adhesion and proliferation on Ti-120, Ti-160, and untreated titanium surfaces. Notes: Data are expressed as the mean ± standard error of the mean. *P<0.01 compared with Ti-120 on days 1 and 3 and **P<0.01 compared with Ti-120 and Ti-160 on days 1 and 3.