Gold Nanorod-Doped Acrylic Bone Cement: Mechanical Stability and Feasibility of Photothermal Therapy

Photothermal therapy (PTT) involves the conversion of electromagnetic radiation into heat to achieve targeted destruction of cells or tissue. Gold nanorods (GNRs) are commonly used nanoparticles in PTT due to their efficient photothermal conversion properties. The purposes of this biomechanical study were 1) to evaluate the in vitro feasibility of PTT using GNR-doped acrylic bone cement and 2) to assess the mechanical properties of the GNR-doped bone cement before and after PTT exposure.

Forty-eight polymethyl methacrylate (PMMA) bone cement tensile specimens were prepared, with groups representing GNR concentrations of 0, 10, 50, and 100 µg/mL (irradiated: six specimens/group; non-irradiated: six specimens/group). A 1064 nm laser with a fluence of 2.85 W/cm² was used to irradiate the specimens. Heat generation and the time required to reach the target temperature (70°C on the non-irradiated surface) were recorded using two thermal imaging cameras. Mechanical tensile testing to failure was performed, and ultimate tensile strength (UTS) and elastic modulus (E) were subsequently measured for each sample.

An increase in GNR concentration within PMMA samples resulted in faster and greater heat generation on the irradiated surface of the specimens, regardless of whether irradiation time or posterior (non-irradiated) surface temperature was held constant. No statistically significant differences in UTS or E were observed between irradiated and non-irradiated specimens at any GNR doped concentration (p > 0.05). However, a statistically significant difference in E was found when comparing the non-irradiated control group to both irradiated and non-irradiated GNR-doped samples. The magnitude of this reduction was less than 0.23 GPa, suggesting limited clinical relevance.  Conclusion: GNR-doped PMMA bone cement demonstrates significant potential as a platform for PTT, achieving temperatures well above those reported in the literature as effective for therapeutic purposes. Importantly, GNR doping PMMA does not produce any appreciable changes in UTS or E before or after PTT exposure. Statement of clinical significance: The findings of this study contribute valuable insight to the limited body of evidence on GNR-doped PMMA. These results support the potential feasibility of using PTT through a novel delivery platform, which may ultimately be applied in the treatment of bone tumors and prosthetic joint infection. Future research should focus on elucidating the specific PTT parameters necessary for anti-tumor and bactericidal efficacy.