Temperature governs the reactivity of a wide range of biomolecules in the cellular environment dynamically. The complex cellular pathways and molecules in solid
tumors substantially produce temperature gradients in the tumor microenvironment (TME). Hence, visualization of these temperature gradients at the cellular level would give physiologically relevant spatio-temporal information about solid
tumors. This study used fluorescent polymeric nano-
thermometers (FPNTs) to measure the intratumor temperature in co-cultured 3D
tumor spheroids. A temperature-sensitive
rhodamine-B dye and
Pluronic F-127 were conjugated through hydrophobic and hydrophobic interactions and then cross-linked with
urea-
paraformaldehyde resins to form the FPNTs. The characterization results exhibit monodisperse nanoparticles (166 ± 10 nm) with persistent fluorescence. The FPNTs exhibit a linear response with a wide temperature sensing range (25-100 °C) and are stable toward pH, ionic strength, and oxidative stress. FPNTs were utilized to monitor the temperature gradient in co-cultured 3D
tumor spheroids and the temperature difference between the core (34.9 °C) and the periphery (37.8 °C) was 2.9 °C. This investigation demonstrates that the FPNTs have great stability, biocompatibility, and high intensity in a biological medium. The usage of FPNTs as a multifunctional adjuvant may demonstrate the dynamics of the TME and they may be suitable candidates to examine thermoregulation in
tumor spheroids.