Abstract
Non-contact, self-referenced and near-infrared luminescent nanothermometers have been recognized as emerging tools in the fields of nanomedicine and nanotechnology due to their great capability of precise temperature readout at the nanoscale and real-time deep-tissue imaging. However, the development of multifunctional and biocompatible luminescent nanothermometers operating within the optically transparent biological windows with high thermal sensitivity (>2.0%/K) remains challenging. Here, we present (Gd0.98Nd0.02)2O3 nanothermometers operated effectively within the first and second biological windows upon continuous-wave laser diode excitation at 808 nm. Ratiometric thermometric parameters are defined by the relative changes in the emission intensities originating from the two Stark components of the 4F3/2 level (R2 and R1) to the 4I9/2 (900–1000 nm), 4I11/2 (1035–1155 nm) and 4I13/2 (1300–1450 nm) multiplets. The thermometric parameters are evaluated for colloidal samples in a cell culture medium and powder samples, and the highest thermal sensitivity (2.18%/K at 298 K) is attained for the former in the first biological window (both the excitation and emission in the 800–965 nm range). The repeatability and temperature uncertainty are 99% and 1.2 K, respectively. The nanothermometers are biocompatible with human MNT-1 melanoma and HaCaT cells for 24 h of exposure and nanoparticle concentration up to 0.400 mg/mL, showing their potential for applications in nanomedicine, e.g., intracellular imaging and temperature mapping.
Highlights
In the last five years, significant progress has been made in the development of biocompatible, efficient and accurate nanoprobes for applications in nanomedicine and nanotechnology,[1,2,3,4] such as intracellular temperature sensing,[5] in vivo/in vitro imaging,[6] clinical diagnosis,[7] drug delivery,[8] and cancer therapy.[9]
The thermometric parameters were evaluated and compared for powder samples and colloidal nanoparticles in cell culture medium (Dulbecco's modified Eagle's medium, DMEM) using the integrated intensity ratio between the emissions originated from the 4F3/2 Stark sublevels (R1 and R2) to the 4I9/2, 4I11/2 and 4I13/2 multiplets: i) 4F3/2(R2)→4I9/2(Z5)/4F3/2(R1) →4I9/2(Z5), ii) 4F3/2(R2)→4I11/2(Y1)/4F3/2(R1)→4I11/2(Y1), and iii) 4F3/2(R2)→4I13/2(X2)/4F3/2(R1)→4I13/2(X2)
The thermometric performance of (Gd0.98Nd0.02)2O3 nanothermometers was evaluated in the physiological temperature range 298–338 K for powder samples and in cell culture medium (Dulbecco's modified Eagle's medium, DMEM)
Summary
In the last five years, significant progress has been made in the development of biocompatible, efficient and accurate nanoprobes for applications in nanomedicine and nanotechnology,[1,2,3,4] such as intracellular temperature sensing,[5] in vivo/in vitro imaging,[6] clinical diagnosis,[7] drug delivery,[8] and cancer therapy.[9]. The Nd3+ NIR emission lines enable non-contact luminescent thermometry operating within the referred biological windows with remarkable temperature sensitivity and resolution.[21, 22] We wish to report nanothermometers effectively operative within the first and second optically transparent BWs based on (Gd0.98Nd0.02)2O3 spherical particles under laser diode excitation at 808 nm in the physiological temperature range (298–338 K).
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