Eradicating Infecting Bacteria while Maintaining Tissue Integration on Photothermal Nanoparticle-Coated Titanium...

Area of Science:

• Biomaterials Science
• Nanotechnology
• Infectious Diseases

Background:

• Photothermal nanoparticles (e.g., polydopamine nanoparticles, PDA-NP) release heat upon near-infrared (NIR) irradiation, with applications expanding from tumor treatment to bacterial infection control.
• Biomaterial-associated infections, such as peri-implantitis in dental implants, pose a significant clinical challenge.
• Collateral thermal damage to surrounding tissues is a potential complication of photothermal therapy, especially on implantable biomaterials.

Purpose of the Study:

• To evaluate the efficacy and safety of photothermal polydopamine nanoparticle (PDA-NP) coatings on titanium surfaces for treating bacterial infections while minimizing collateral tissue damage.
• To determine optimal NIR irradiation parameters for eradicating *Staphylococcus aureus* on titanium surfaces with varying tissue integration models.

Main Methods:

• Titanium surfaces were coated with PDA-NP (200 μg/cm²).
• Coculture models involving *Staphylococcus aureus* and human gingival fibroblasts or keratinocytes were used to simulate clinical scenarios.
• NIR irradiation was applied at different durations to assess bacterial killing, fibroblast/keratinocyte viability, and surface coverage.

Main Results:

• NIR irradiation of PDA-NP-coated titanium effectively killed *Staphylococcus aureus* within approximately 3 minutes.
• Short NIR irradiation (around 3 min) preserved fibroblast coverage on titanium surfaces.
• Preventing bacterial contamination from reducing fibroblast coverage required longer NIR irradiation (≥5 min) prior to fibroblast adherence.
• Protecting established fibroblast and keratinocyte layers from bacterial challenge necessitated longer NIR irradiation (10 min) due to increased heat absorption by the tissue layers.
• Extended irradiation times beyond optimal parameters led to collateral fibroblast damage.

Conclusions:

• Photothermal treatment using PDA-NP coatings on titanium shows promise for managing biomaterial-associated bacterial infections.
• Precise control over NIR irradiation duration is essential to balance bacterial eradication with the preservation of surrounding host tissues.
• The required irradiation time is influenced by the specific bacterial challenge and the presence of host cells, necessitating tailored treatment protocols.