A minireview on multiparameter-activated nanodevices for cancer imaging and therapy.

Tumor microenvironment (TME)-responsive nanodevices are essential tools for cancer imaging and therapy. Exploiting the advantages of molecular engineering, nanodevices are emerging for biomedical applications. In order to reach targeted cancer areas, activated nanodevices first respond to the TME and then serve as an actuator for sensing, imaging and therapy. Most nanodevices depend on a single parameter as an input for their downstream activation, potentially leading to inaccurate diagnostic results and poor therapeutic outcomes. However, in the TME, some biomarkers are cross-linked, and such correlated biomarkers are potentially useful for cancer imaging and theranostic applications. Based on this phenomenon, researchers have developed approaches for the construction of multiparameter-activated nanodevices (MANs) to improve accuracy. This minireview summarizes the recent advances in the development of MANs for cancer imaging including fluorescence imaging, photoacoustic (PA) imaging, magnetic resonance imaging (MRI) and computed tomography (CT) imaging, as well as cancer therapy including radiotherapy, chemotherapy, photoinduced therapy and immunotherapy. We highlight different approaches for improving the specificity and precision of cancer imaging and therapy. In the future, MANs will show promise for clinical work in multimodal diagnosis and therapeutics.

Conformational Conversion Enhances Cellular Uptake of F Base Double-Strand-Conjugated Oligonucleotides.

Artificial bases have emerged as a useful tool to expand genetic alphabets and biomedical applications of oligonucleotides. Herein, we reported that the conformation conversion enhances cellular uptake of hydrophobic 3,5-bis(trifluoromethyl)benzene (F) base double-strand-conjugated oligonucleotides. The formation of the F base double-strand caged the hydrophobic F base in the duplex strand, thus preventing F base from interacting with cells to some extent. However, upon conversion of F base double-strand-conjugated oligonucleotide to F base single-strand-conjugated oligonucleotide, F bases then were allowed to interact with cells by stronger hydrophobic interactions, followed by cellular uptake. The results were concluded as a pairing-induced cage effect of F base and have the potential for the construction of stimuli-responsive cellular uptake of functional nucleic acids.

Monitoring Telomerase Activity in Living Cells with High Sensitivity Using Cascade Amplification Reaction-Based Nanoprobe.

Human telomerase has been considered as a promising tumor marker for early cancer diagnosis and tumor progression monitoring. Current methods for detection of telomerase mainly rely on in vitro assays using cell lysate, which cannot provide information on telomerase activities in living systems. Only the few reported intracellular probes possess high telomerase selectivity but involve no signal amplification process, which potentially limits their use in application scenarios requiring high sensitivity. The development of an ultrasensitive intracellular telomerase probe is of high demand but challenging, because of the difficulty in designing a robust amplification process in living cells. Inspired by the mechanism of telomerase primer binding and extension, we introduce a cascade amplification reaction-based nanoprobe for intracellular telomerase detection by incorporating DNAzyme and catalytic hairpin assembly onto MnO2 nanosheets. The MnO2 nanosheets can deliver and release multicomponent signal amplification motifs with designed ratio at the same intracellular position, thereby enabling the cascade process in cells to occur. The released Mn2+ ions from degraded MnO2 nanosheets can activate DNAzyme as a metal cofactor and facilitate endosomal escape, because of the ion sponge effect. We used the nanoprobe to successfully monitor the dynamic change of telomerase activity in the HeLa cell, as well as in three other types of cells. This cascade amplification nanoprobe provides ultrasensitive detection of telomerase activity, indicating its use as a promising bioassay for early cancer diagnosis.

Sequential Protein-Responsive Nanophotosensitizer Complex for Enhancing Tumor-Specific Therapy.

A major challenge in cancer treatment is the development of effective tumor-specific therapeutic methods that have minimal side effects. Recently, a photodynamic therapy (PDT) technique using activatable photosensitizers (aPSs) has shown great potential for cancer-specific treatment. Here, we develop a sequential protein-responsive aPS (PcC4-MSN-O1) that is based on zinc(II) phthalocyanine derivative (PcC4)-entrapped mesoporous silica nanoparticles (MSNs) and a wrapping DNA (O1) as a biogate. Inside the nanostructure of PcC4-MSN-O1, PcC4 shows self-quenching photoactivity. However, when PcC4-MSN-O1 sequentially reacts with telomerase and albumin, its photoactivity is dramatically turned on. Therefore, PcC4-MSN-O1 displays selective phototoxicity against cancer cells ( e.g., HeLa) over normal cells ( e.g., HEK-293). Following systemic PcC4-MSN-O1 administration, there is an obvious accumulation in HeLa tumors of xenograft-bearing mice, and laser irradiation clearly induces the inhibition of tumor growth. Moreover, the time-modulated activation process in tumors and the relatively fast excretion of PcC4-MSN-O1 indicate its advantages in reducing potential side effects.

Engineering of Bioinspired, Size-Controllable, Self-Degradable Cancer-Targeting DNA Nanoflowers via the Incorporation of an Artificial Sandwich Base.

In this article, we used an artificial DNA base to manipulate the formation of DNA nanoflowers (NFs) to easily control their sizes and functionalities. Nanoflowers have been reported as the noncanonical self-assembly of multifunctional DNA nanostructures, assembled from long DNA building blocks generated by rolling circle replication (RCR). They could be incorporated with myriad functional moieties. However, the efficacy of these DNA NFs as potential nanocarriers delivering cargo in biomedicine is limited by the bioavailability and therapeutic efficacy of their cargo. Here we report the incorporation of metal-containing artificial analogues into DNA strands to control the size and the functions of NFs. We have engineered bioinspired, size-controllable, self-degradable cancer-targeting DNA nanoflowers (Sgc8-NFs-Fc) via the incorporation of an artificial sandwich base. More specifically, the introduction of a ferrocene base not only resulted in the size controllability of Sgc8-NFs-Fc from 1000 to 50 nm but also endowed Sgc8-NFs-Fc with self-degradability in the presence of H2O2 via Fenton's reaction. In vitro experiments confirmed that Sgc8-NFs-Fc/Dox could be selectively taken up by protein tyrosine kinase 7 (PTK7)-positive cancer cells and subsequently cleaved via Fenton's reaction, resulting in rapid release kinetics, nuclear accumulation, and enhanced cytotoxicity of their cargo. In vivo experiments further confirmed that Sgc8-NFs-Fc has good tumor-targeting ability and could significantly improve the therapeutic efficacy of doxorubicin in a xenograft tumor model. On the basis of their tunable size and on-demand drug release kinetics upon H2O2 stimulation, the Sgc8-NFs-Fc nanocarriers possess promising potential in drug delivery.

An MTH1-targeted nanosystem for enhanced PDT via improving cellular sensitivity to reactive oxygen species.

Herein, we developed a strategy to attack the cancer cell defense system against reactive oxygen species to improve photodynamic therapy efficacy with a Ce6@MSN@MTH1 siRNA nanosystem, which was demonstrated to improve cellular sensitivity to reactive oxygen species through suppressing MTH1 protein in cancer cells.

Engineering Stability-Tunable DNA Micelles Using Photocontrollable Dissociation of an Intermolecular G-Quadruplex.

Because of their facile preparation, small size (<100 nm), programmable design, and biocompatibility, lipid-based DNA micelles show enormous potential as a tool to monitor biological events and treat human diseases. However, their structural stability in biological matrices suffers from spatiotemporal variability, thus limiting their in vivo use. Herein, we have engineered stability-tunable DNA micelle flares using photocontrollable dissociation of intermolecular G-quadruplexes, which confers DNA micelle flares with robust structural stability against disruption by serum albumin. However, once exposed to light, the G-quadruplex formation is blocked by strand hybridization, resulting in the loss of stability in the presence of serum albumin and subsequent cellular uptake. This programmable regulation to stabilize lipid-based micelles in the presence of fatty-acid-binding serum albumin should further the development of biocompatible DNA micelles for in vivo applications.

Using modified aptamers for site specific protein-aptamer conjugations.

Conjugation of DNAs to defined locations on a protein surface will offer powerful tools for positioning functional groups and molecules in biological and biomedical studies. However, tagging protein with DNA is challenging in physiological environments, which requires a bioorthogonal approach. Here we report a chemical solution to selectively conjugate DNA aptamer with a protein by protein-aptamer template (PAT)-directed reactions. Since protein-aptamer interactions are bioorthogonal, we exploit PAT as a unique platform for specific DNA-protein cross-linking. We develop a series of modified oligonucleotides for PAT-directed reactions and screen out F-carboxyl as a suitable functionality for selective and site-specific conjugation. The functionality is incorporated into aptamers by our F-carboxyl phosphoramidite with easy synthesis. We also demonstrate the necessity of a linker between the reactive functionality and the aptamer sequences.

STIP overexpression confers oncogenic potential to human non-small cell lung cancer cells by regulating cell cycle and apoptosis.

Sip1/tuftelin-interacting protein (STIP), a multidomain nuclear protein, is a novel factor associated with the spliceosome, yet its role and molecular function in cancer remain unknown. In this study, we show, for the first time, that STIP is overexpressed in non-small cell lung cancer (NSCLC) tissues compared to adjacent normal lung tissues. The depletion of endogenous STIP inhibited NSCLC cell proliferation in vitro and in vivo, caused cell cycle arrest and induced apoptosis. Cell cycle arrest at the G2/M phase was associated with the expression and activity of the cyclin B1-CDK1 (cyclin-dependent kinase 1) complex. We also provide evidence that STIP knockdown induced apoptosis by activating both caspase-9 and caspase-3 and by altering the Bcl-2/Bax expression ratio. RNA sequencing data indicated that the MAPK mitogen-activated protein kinases, Wnt, PI3K/AKT, and NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signalling pathways might be involved in STIP-mediated tumour regulation. Collectively, these results suggest that STIP may be a novel potential diagnostic and therapeutic target for NSCLC.

DNA Aptamer Selected against Pancreatic Ductal Adenocarcinoma for in vivo Imaging and Clinical Tissue Recognition.

In this work, we have developed a truncated DNA aptamer, termed XQ-2d, with high affinity and specificity for pancreatic ductal adenocarcinoma (PDAC). Aptamer XQ-2d selectively binds to PL45 cells with a dissociation constant in the nanomolar range, as determined by its recognition of PL45 tumor cells in mice. Moreover, XQ-2d shows better recognition ratio for 40 tissue sections of clinical PDAC samples (82.5%) compared to the initial cell-SELEX selection library (5%). Therefore, XQ-2d can be considered a promising candidate as a tool for PDAC diagnosis and treatment.

Activatable fluorescence/MRI bimodal platform for tumor cell imaging via MnO2 nanosheet-aptamer nanoprobe.

A novel dual-activatable fluorescence/MRI bimodal platform is designed for tumor cell imaging by using a redoxable manganese dioxide (MnO2) nanosheet-aptamer nanoprobe. The redoxable MnO2 nanosheet acts as a DNA nanocarrier, fluorescence quencher, and intracellular glutathione (GSH)-activated MRI contrast agent. In the absence of target cells, neither fluorescence signaling nor MRI contrast of the nanoprobe is activated. In the presence of target cells, the binding of aptamers to their targets weakens the adsorption of aptamers on the MnO2 nanosheets, causing partial fluorescence recovery, illuminating the target cells, and also facilitating the endocytosis of nanoprobes into target cells. After endocytosis, the reduction of MnO2 nanosheets by GSH further activates the fluorescence signals and generates large amounts of Mn(2+) ions suitable for MRI. This platform should facilitate the development of various dual-activatable fluorescence/MRI bimodalities for use in cells or in vivo.

Aptamer TY04 inhibits the growth of multiple myeloma cells via cell cycle arrest.

The aptamer TY04 is a single-stranded DNA. However, its biological function has not been elucidated. Here, we found that TY04 specifically bound to multiple myeloma cells MM.1S, and some membrane proteins on the surface of MM.1S cells constituted the target molecules of TY04. TY04 inhibited the growth of multiple myeloma cell lines, induced cell cycle arrest in mitosis, and resulted in a significant accumulation of binucleated cells. Following TY04 treatment, a concomitant increase in CDK1 and cyclin B1 expression occurred. In addition, TY04 treatment also resulted in a significant downregulation of γ-tubulin. Considering the unique advantages of aptamers, TY04 shows great potential as a drug candidate to treat multiple myeloma.

A superquenched DNAzyme-perylene complex: a convenient, universal and low-background strategy for fluorescence catalytic biosensors.

Taking advantage of the super-quenching effect of the cationic perylene derivative on adjacent fluorophores, we for the first time reported a DNAzyme-perylene complex-based strategy for constructing fluorescence catalytic biosensors with improved sensitivity.