Direct investigations of interactions between nucleolins and aptamers on pancreatic cancer and normal cells by atomic force microscopy.

Nucleolin is overexpressed on the surface of pancreatic cancer cells and are regarded as the remarkable therapeutic target. Aptamers are capable of binding the external domain of nucleolin on the cell surface with high affinity and specificity. But nucleolin has not been localized on pancreatic cancer cells at very high spatial resolution, and the interactions between nucleolin and aptamers have not been investigated at very high force resolution level. In this work, nucleolin was localized on pancreatic cancer and normal cells by aptamers (9FU-AS1411-NH2, AS1411-NH2 and CRONH2) in Single Molecule Recognition Imaging mode of Atomic Force Microscopy. There are plenty of nucleolin on the surfaces of pancreatic cancer cells (area percentage about 5 %), while there are little nucleolin on the surfaces of normal cells. The interactions between three types of aptamers and nucleolins on the surfaces of pancreatic cancer cells were investigated by Single Molecule Force Spectroscopy. The unbinding forces of nucleolins-(9FU-AS1411-NH2) are larger than nucleolins-(AS1411-NH2). The dissociation activation energy on nucleolin-(9FU-AS1411-NH2) is higher than nucleolin-(AS1411-NH2), which indicates that the former complex is more stable and harder to dissociate than the later complex. There are no unbinding forces between nucleolin and CRONH2. All these demonstrate that nucleolin was localized on pancreatic cancer and normal cells at single molecule level quantitatively, and the interactions (unbinding forces and kinetics) between nucleolin and aptamers were studied at picoNewton level. The approaches and results of this work will pave new ways in the investigations of nucleolin and aptamers, and will also be useful in the studies on other proteins and their corresponding aptamers.

Multifunctional Probe Based on "Chemical Antibody-Aptamer" for Noninvasive Detection of PD-L1 Expression in Cancer.

Immune checkpoint inhibitors (ICIs) therapy based on programmed cell death ligand 1 (PD-L1) has shown significant development in treating several carcinomas, but not all patients respond to this therapy due to the heterogeneity of PD-L1 expression. The sensitive and accurate quantitative analysis of in vivo PD-L1 expression is critical for treatment decisions and monitoring therapy. In the present study, an aptamer-based dual-modality positron emission tomography/near-infrared fluorescence (PET/NIRF) imaging probe was developed, and its specificity and sensitivity to PD-L1 were assessed in vitro and in vivo. The probe precursor NOTA-Cy5-R1 was prepared by using automated solid-phase oligonucleotide synthesis. PET/NIRF dual-modality probe [68Ga]Ga-NOTA-Cy5-R1 was successfully synthesized and radiolabeled. The binding specificity of [68Ga]Ga-NOTA-Cy5-R1 to PD-L1 was evaluated by flow cytometry, fluorescence imaging, and cellular uptake in A375-hPD-L1 and A375 cells, and it showed good fluorescence properties and stability in vitro. In vivo PET/NIRF imaging studies illustrated that [68Ga]Ga-NOTA-Cy5-R1 can sensitively and specifically bind to PD-L1 positive tumors. Meanwhile, the rapid clearance of probes from nontarget tissues achieved a high signal-to-noise ratio. In addition, changes of PD-L1 expression in NCI-H1299 xenografts treated with cisplatin (CDDP) were sensitivity monitored by [68Ga]Ga-NOTA-Cy5-R1 PET imaging, and ex vivo autoradiography and western blot analyses correlated well with the change of PD-L1 expression in vivo. Overall, [68Ga]Ga-NOTA-Cy5-R1 showed notable potency as a dual-modality PET/NIRF imaging probe for visualizing tumors and monitoring the dynamic changes of PD-L1 expression, which can help to direct and promote the clinical practice of ICIs therapy.

Two Birds with One Stone: A Novel Dithiomaleimide-Based GalNAc-siRNA Conjugate Enabling Good siRNA Delivery and Traceability.

For the first time, a novel dithiomaleimides (DTM) based tetra-antennary GalNAc conjugate was developed, which enable both efficient siRNA delivery and good traceability, without incorporating extra fluorophores. This conjugate can be readily constructed by three click-type reactions, that is, amidations, thiol-dibromomaleimide addition and copper catalyzed azide-alkyne cycloaddition (CuAAC). And it also has comparable siRNA delivery efficiency, with a GalNAc L96 standard to mTTR target. Additionally, due to the internal DTMs, a highly fluorescent emission was observed, which benefited delivery tracking and reduced the cost and side effects of the extra addition of hydrophobic dye molecules. In all, the simple incorporation of DTMs to the GalNAc conjugate structure has potential in gene therapy and tracking applications.