Dextran based pH-sensitive near-infrared nanoprobe for in vivo differential-absorption dual-wavelength photoacoustic imaging of tumors

A dextran based pH-sensitive near-infrared nanoprobe was prepared and applied as a contrast agent for photoacoustic imaging to identify a tumor in vivo. The nanoprobe has two resonance absorption peaks in the near-infrared region and the cleavage of hydrazone bonds in the low pH value environment can cause their coefficients to change, making a different ratio of photoacoustic signal output. By comparing the photoacoustic signal ratio under the two wavelengths, in vitro photoacoustic images show that the nanoprobe has the capacity to distinguish cancer cells and normal cells. Moreover, an in vivo mouse breast tumor model (EMT-6 cells) can be identified from peripheral normal tissues by dual-wavelength photoacoustic imaging. These results suggest the potential application of this pH-sensitive near-infrared nanoprobe as a contrast agent to noninvasively detect tumors in their early stage with high optical contrast by dual-wavelength photoacoustic imaging based on the tunable absorbance ratio in normal physiological and tumor acidic microenvironments.