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Currently, functional single-stranded oligonucleotide probes, termed aptamers, generated by an iterative technology, Systematic Evolution of Ligands by Exponential Enrichment (SELEX), are utilized to selectively target molecules or cells with high affinity. Aptamers hold considerable promise as multifunctional molecules or conjugates for challenging nanotechnologies or bioapplications now and in the future. In this review, we first describe recent endeavors to select aptamers towards live cancer cells via cell-SELEX. We then introduce several characteristic applications of selected aptamers, especially in imaging, drug delivery and therapy. In part, these advances have been made possible via synthesis of aptamer-based nanomaterials, which, by their sizes, shapes, and physicochemical properties, allow such aptamer-nanomaterial complexes to function as signal reporters or drug carriers. We also describe how these aptamer-based molecular tools contribute to cancer biomarker discovery through high-affinity recognition of membrane protein receptors.

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We developed a novel Ru(bpy)-based electrochemiluminescence (ECL) immunosensor utilizing palladium nanoparticle (Pd NP)-functionalized graphene-aerogel-supported FeO (FGA-Pd) for real-sample analysis of prostate specific antigen (PSA). 3D nanostructured FGA-Pd, as a novel ECL carrier, was prepared by in situ reduction. Large amounts of Ru(bpy) could combine with FGA-Pd via electrostatic interaction to establish a brand-new ECL emitter (Ru@FGA-Pd) for improving ECL efficiency. The obtained Ru@FGA-Pd composite was utilized to label the secondary antibody, which generated strong ECL signals with tripropylamine (TPrA) as a coreactant. Furthermore, we demonstrated that the participation of Pd NPs endowed FGA with favorable electrocatalytic ability in the luminescence process to produce more excited state [Ru(bpy)]* for realizing desirable signal amplification. In addition, the primary antibody was captured by gold nanoparticle (Au NP)-functionalized FeO nanodendrites (Au-FONDs), which possessed good electrical conductivity and favorable biocompatibility. Under optimum conditions, the fabricated sandwich-type ECL immunosensor showed a sensitive response to PSA with a low detection limit of 0.056 pg/mL (S/N = 3) and a calibration range of 0.0001-50 ng/mL. Featuring favorable selectivity, stability, and repeatability, the proposed immunosensor is expected to blaze a novel trail for the real sample detection of PSA and other biomarkers.

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A high-sensitivity electrochemiluminescence (ECL) sensor was conducted to detect carcinoembryonic antigen (CEA). Nanocomposites of graphene oxide/carboxylated multiwall carbon nanotubes/gold/cerium oxide nanoparticles (GO/MWCNTs-COOH/Au@CeO2) were used as antibody carriers and sensing platforms to modify on glassy carbon electrodes (GCE). CeO2 nanoparticles were first exploited as an ECL luminescent material and the possible ECL mechanism was proposed in this work. GO/MWCNTs-COOH was used as a loading matrix for CeO2 nanoparticles because of the superior conductivity and large specific surface area. Au nanoparticles were further deposited on this matrix to attach anti-CEA and enhance the sensitivity of immunosensor. The proposed sensing platform showed excellent cathodic ECL performance and sensitive response to CEA. The effects of experimental conditions on the ECL performance were investigated. The proposed immunosensor showed the broad linear range (0.05-100 ng/mL) and the low detection limit (LOD, 0.02 ng/mL, signal-to-noise ratio = 3) according to the selected experimental conditions. The excellent analysis performance for determination of CEA in the human serum samples simplied this immunosensor displayed high sensitivity and excellent repeatability. More importantly, this conducted immunosensor broadens the use scope of CeO2 nanoparticles.

We have developed a photoelectrochemical (PEC) cytosensor for ultrasensitive detection of RAW264.7 cells by the signal change of a TiO nanoneedles (NNs)@MoO array. For the first time, a TiO NNs@MoO array was adopted for the fabrication of the cytosensor for the signal output. The well-matched alignment of TiO NNs and MoO efficiently suppresses the recombination of photogenerated electron and hole (e/h) pairs for improved photon-to-current conversion efficiency. The RAW264.7 cell and F4/80 antibody could form the biocomplexes because of the specific recognition between each other. The constructed PEC cytosensor based on the TiO NNs@MoO array displayed good PEC property for detection of RAW264.7 cells. The numbers of RAW264.7 cells are directly detected through the decrement of photocurrent intensity, due to the increased steric hindrance when RAW264.7 cells are captured. The PEC cytosensor showed an ultrasensitive response to RAW264.7 cells with a linear range of 50-15 000 cells/mL and a detection limit of 50 cells/mL. The designed cytosensor based on a TiO NNs@MoO array offers an ideal platform to detect RAW264.7 cells with excellent stability, reproducibility, and selectivity and served as a model for the fabrication of cytosensors for other cells.