CdSe-ZnS quantum dots as temperature sensors during thermal coagulation of bovine serum albumin (BSA) solder

Laser tissue soldering (LTS) has variously interesting applications such as wound closure, anastomosis of blood vessels, and sealing corneal wounds. Since tissue properties such as optical absorption or thermal conductivity may differ, temperature control is essential to obtain full coagulation and to minimize thermal side effects. In this article, a non-invasive technique is proposed for temperature sensing by using CdSe-ZnS quantum dots (QDs) dissolved in protein solder, namely bovine serum albumin (BSA). The temperature measurement is conducted by monitoring the change in the photoluminescence spectra of the QDs. It is shown that the peak emission wavelength of about 653 nm of CdSe-ZnS QDs shifts linearly in a temperature range from 30 A degrees C to 70 A degrees C, with a coefficient of 0.153 nm A degrees C-1 with increasing temperature. The wavelength shift can be determined by applying a small spectrometer with a CCD-array detector. The uncertainty associated with this method is estimated to be less than 6 A degrees C in temperature. As the temperature increases, the measured signal strength initially remains constant and then falls off abruptly when exceeding 55 A degrees C. The signal drop correlates with a phase change from a clear, low-scattering protein solution to strong-scattering solid material.