Amino-functionalized fluorescent carbon dots have been prepared by hydrothermal treatment of glucosamine with excess pyrophosphate. The produced carbon dots showed stabilized green emission fluorescence at various excitation wavelengths and pH environments. Herein, we demonstrate the surface energy transfer between the amino-functionalized carbon dots and negatively charged hyaluronate stabilized gold nanoparticles. Hyaluronidase can degrade hyaluronate and break down the hyaluronate stabilized gold nanoparticles to inhibit the surface energy transfer. The developed fluorescent carbon dot/gold nanoparticle system can be utilized as a biosensor for sensitive and selective detection of hyaluronidase by two modes which include fluorescence measurements and colorimetric analysis.

Photothermal therapy (PTT) using near-infrared (NIR) light for tumor treatment has triggered extensive attentions because of its advantages of noninvasion and convenience. The current research on PTT usually uses lasers in the first NIR window (NIR-I; 700–900 nm) as irradiation source. However, the second NIR window (NIR-II; 1000–1700 nm) especially NIR-IIa window (1300–1400 nm) is considered much more promising in diagnosis and treatment as its superiority in penetration depth and maximum permissible exposure over NIR-I window. Hereby, we propose the use of laser excitation at 1275 nm, which is approved by Food and Drug Administration for physical therapy, as an attractive technique for PTT to balance of tissue absorption and scattering with water absorption. Specifically, CuS-PEG nanoparticles with similar absorption values at 1275 and 808 nm, a conventional NIR-I window for PTT, were synthesized as PTT agents and a comparison platform, to explore the potential of 1275 and 808 nm lasers for PTT, especially in deep-tissue settings. The results showed that 1275 nm laser was practicable in PTT. It exhibited much more desirable outcomes in cell ablation in vitro and deep-tissue antitumor capabilities in vivo compared to that of 808 nm laser. NIR-IIa laser illumination is superior to NIR-I laser for deep-tissue PTT, and shows high potential to improve the PTT outcome.

Although antibodies are well developed and widely used in cancer therapy and diagnostic fields, some defects remain, such as poor tissue penetration, long in vivo metabolic retention, potential cytotoxicity, patent limitation, and high production cost.

Photoacoustic imaging (PAI) is a new and attractive imaging modality, and it has strong potential for application in the early detection of tumors through the use of optically absorbing targeted contrast agents. Ag₂S quantum dots (QD) are a promising bionanomaterial and have attracted significant attention in the field of bioimaging. In this study, water-soluble and carboxylic acid group-coated Ag₂S QDs with an ultrasmall size (∼8 nm) were synthesized via a one-step method. Their surface plasmon resonance wavelength was determined to be ∼800 nm, which is ideal for PAI. Ag₂S QDs were then modified with the epidermal growth factor receptor 1 (EGFR) targeted small protein affibody Z_EGFR:1907. The resulted nanoprobe, Z_EGFR:1907-Ag₂S QDs, was then used for targeted PAI of EGFR-overexpressed tumors. The biodistribution of the nanoprobe was further measured by ex vivo near infrared fluorescence (NIRF) imaging of the dissected tissues. The PAI results showed that Z_EGFR:1907-Ag₂S QDs specifically image EGFR positive tumors. The biodistribution study revealed that the nanoprobe mainly accumulated in the liver, spleen and tumors; tissue H&E staining studies indicated that the probe has good biocompatibility. Overall, the affibody-functionalized Ag₂S QDs are a novel targeted nanoprobe that can be used for specific PAI of tumors.