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Cancer theranostics is of great significance in the personalized therapy. In this work, stable Janus nanoparticles (JNPs) containing PEG and two kinds of DNAs were prepared by means of "click chemistry". In response to ATP or acid condition, the prepared JNPs could form Au NP dimers, which facilitate in situ SERS detection and SERS imaging analysis of cancer cells due to the formation of "hot spots" in the nanogap between the Au NP dimers. A detection limit of 2.3 × 10 -9 M was obtained for ATP. As for a pH sensor, the SERS signals increased with the decrease of pH value from 8.0 to 4.0. In situ monitoring of ATP or acid condition in cancer cells by SERS can improve the accuracy and sensitivity of diagnosis. Moreover, drugs and photosensitizers loaded on the other side of JNPs led to the chemotherapy/photodynamic therapy synergistic antitumor effect, which was verified by in vitro and in vivo experiments. Given the excellent performance in SERS detection and cancer therapy, the developed JNPs hold considerable potential in cancer theranostics.

A cathodic photoelectrochemical sensor has been developed for the determination of exosomes, based on a dual-signal reduction strategy. A heterostructure of NiO/BiOI/Au NP/CdSe was synthesized as a photoelectrochemical sensing interface, which is able to suppress the recombination of electron-hole pairs and produce a higher photocurrent. The obtained materials were characterized, and the mechanism for the generation of the cathodic photocurrent was proposed. CdSe QDs (quantum dots) modified with DNA 2 were assembled on the electrode through the hybridization with EpCAM aptamer on the surface of ITO/NiO/BiOI/Au NP. The introduction of CdSe QDs to the electrode increases the photocurrent.The recognition of exosomes with aptamer DNA led to the separation of CdSe QDs from the electrode, which in turn caused the decrease of photocurrents. Meanwhile, the big volume of exosomes hinders the electron transfer between the electrode and electrolyte. Due to the dual reduction effect, a sensitive PEC sensor was obtained with a detection limit of 1.2 × 10 2 particles/μL exosomes (λ ex  = 430 nm, bias voltage = - 0.1 V). The cathodic photoelectrochemical sensor showed good selectivity, performed well in a complex biological environment and could be used to distinguishbreast cancer patients from healthy individuals.

The Raman probe plays an essential role in sensitive surface-enhanced Raman scattering (SERS) assay. Here, a novel Raman probe was developed by assembling gold nanoparticles in triangular pyramid DNA (TP-Au NPs). Such probe with intense electromagnetic hot spots can provide dramatically enhanced Raman scattering. Through assembling recognition DNA on one corner of the TP-DNA, the recognition event is definite and designable. The probe was characterized through TEM, and its SERS superiority was investigated. As models, circulating tumor cells and exosomes were detected with high sensitivity and selectivity by using this probe. Meanwhile, the developed SERS probe can also perform well in real world samples.