Divalent Aptamer-Functionalized Nanochannels for Facile Detection of Cancer Cell-Derived Exosomes.

Exosomes are considered potential biomarkers for early screening and accurate non-invasive diagnosis of cancer, so development of innovatively facile approaches for the detection of cancer cell-derived exosomes has become increasingly important. Herein, we propose a facile electrochemical biosensor based on divalent aptamer-functionalized nanochannels for highly efficient detection of cancer cell-derived exosomes. The aptamer against transmembrane receptor protein CD63 and the aptamer targeting membrane protein EpCAM are simultaneously immobilized on the nanochannels to construct the divalent aptamer-functionalized nanochannels. Thus, the target exosomes can be recognized and selectively captured by the functionalized nanochannels in a divalent collaborative manner. The combined exosomes overlay the ion channel effectively and hinder the ionic flow through the nanochannels, resulting in an evidently varied ionic transport behavior corresponding to the abundance of exosomes. The divalent aptamer-functionalized nanochannels can substantially promote the binding stability and enhance the detection specificity, while the sensitivity of detection is improved greatly by virtue of the amplified response of array channels synergized with the electrochemical technique. Therefore, the developed biosensor provides a highly specific, sensitive, and accurate approach for the detection of cancer cell-derived exosomes, which may hold great potential for application in early clinical cancer diagnosis.

In situ peptide self-assembly on ionic nanochannel for dynamic monitoring of MMPs in extracellular matrix.

The extracellular matrix (ECM) of tumor mediates malignant transformation and distant metastasis with extracellular proteinases, especially the matrix metalloproteinases (MMPs). However, there is no assay method to trace the dynamic content of MMPs in ECM. In this work, we have proposed a strategy by assembling peptide scaffold on ionic nanochannels to monitor the target proteinases. The short peptide unit is designed to induce self-assembly with good stability, biocompatibility and programmability, while ion nanochannels can provide electrochemical response upon the MMP activities. Taking MMP-2 as an example, the peptide unit includes two regions, one for self-assembly and one for bio-recognition, so the assembly region (KLVFF) can self-assemble to nanofiber networks. In the meantime, since the reactive region (PLGVR) has MMP-2 recognition site, the peptide assembly on nanochannel can thus be used for the detection of active MMP-2 in tumor microenvironment, with a wide linear detection range (10 fg/mL-10 ng/mL) and 6.6 fg/mL limit of detection. Moreover, the availability of the established ECM mimic is able to distinguish active MMP-2 from latent proMMP-2 in tumor samples. By designing different peptide units for self-assembly on the ionic nanochannel, the assay platform can be promisingly used for other proteinases in ECM, so this work may provide a useful approach to trace the dynamic content of the MMPs in tumor microenvironment (TEM).