Biosynthesis of CuTe Nanorods with Large Molar Extinction Coefficients for NIR-II Photoacoustic Imaging

Photoacoustic imaging (PAI) in the second near-infrared region (NIR-II), due to deeper tissue penetration and a lower background interference, has attracted widespread concern. However, the development of NIR-II nanoprobes with a large molar extinction coefficient and a high photothermal conversion efficiency (PCE) for PAI and photothermal therapy (PTT) is still a big challenge. In this work, the NIR-II CuTe nanorods (NRs) with large molar extinction coefficients ((1.31 ± 0.01) × 10⁸ cm^-1·M^-1 at 808 nm, (7.00 ± 0.38) × 10⁷ cm^-1·M^-1 at 1064 nm) and high PCEs (70% at 808 nm, 48% at 1064 nm) were synthesized by living Staphylococcus aureus () cells as biosynthesis factories. Due to the strong light-absorbing and high photothermal conversion ability, the in vitro PA signals of CuTe NRs were about 6 times that of indocyanine green (ICG) in both NIR-I and NIR-II. In addition, CuTe NRs could effectively inhibit tumor growth through PTT. This work provides a new strategy for developing NIR-II probes with large molar extinction coefficients and high PCEs for NIR-II PAI and PTT.