A Telomerase-Specific Doxorubicin-Releasing Molecular Beacon for Cancer Theranostics

Nanoscale octopus guiding telomere entanglement: An innovative strategy for inducing apoptosis in cancer cells

Telomere length plays a crucial role in cellular aging and the risk of diseases. Unlike normal cells, cancer cells can extend their own survival by maintaining telomere stability through telomere maintenance mechanism. Therefore, regulating the lengths of telomeres have emerged as a promising approach for anti-cancer treatment. In this study, we introduce a nanoscale octopus-like structure designed to induce physical entangling of telomere, thereby efficiently triggering telomere dysfunction. The nanoscale octopus, composed of eight-armed PEG (8-arm-PEG), are functionalized with cell penetrating peptide (TAT) to facilitate nuclear entry and are covalently bound to N-Methyl Mesoporphyrin IX (NMM) to target G-quadruplexes (G4s) present in telomeres. The multi-armed configuration of the nanoscale octopus enables targeted binding to multiple G4s, physically disrupting and entangling numerous telomeres, thereby triggering telomere dysfunction. Both in vitro and in vivo experiments indicate that the nanoscale octopus significantly inhibits cancer cell proliferation, induces apoptosis through telomere entanglement, and ultimately suppresses tumor growth. This research offers a novel perspective for the development of innovative anti-cancer interventions and provides potential therapeutic options for targeting telomeres.

Telomerase-Responsive CRISPR System-Regulated Nanobomb for Triggering Research on Telomerase "Self-Detonation"

Targeting tumor markers is one of the most important approaches to tumor therapy, and the "suicide" pattern of tumor marker response is a very challenging study. Telomerase, as one of the key factors associated with human longevity and cancer progression, is considered to be an emerging biomarker for cancer diagnosis. The targeted drug delivery nanobomb─BIBR1532@HSN/FQDNA/MUC1 aptamer (B@HDA) is prepared in this study based on hollow silica nanoparticles (HSN) and CRISPR systems. Amino-modified FQDNA and amino-modified MUC1 aptamer are covalently attached to the surface of carboxyl-functionalized HSN. The modified MUC1 aptamer directs the nanobomb to specifically target breast cancer cells (MCF-7) and FQDNA sequesters the telomerase inhibitor (BIBR1532) within the HSN. Telomerase primers (TPs) is recognized by the highly expressed telomerase in MCF-7 cells and is elongated to form DNA substrates. The substrate pairs with crRNA bases to effectively activate CRISPR-Cas12a. The activated CRISPR-Cas12a precisely cut FQDNA, releasing BIBR1532, which inhibits telomerase activity. This strategy achieves telomerase "suicide". The nanobomb described above has the following advantages. (1) The "closing" effect of FQDNA contributes to reducing the nonspecific release of BIBR1532. (2) B@HDA, combined with CRISPR, regulates mitochondrial dysfunction and cell senescence in MCF-7 cells. (3) In the tumor-bearing mouse model, B@HDA, combined with CRISPR, exhibits good biocompatibility and an obvious tumor ablation effect on MCF-7 tumors, suggesting potential application prospects across a wide range of cancer cell lines. In summary, the proposed nanobomb provides a tunable switch approach for the specific inhibition of telomerase and the reduction of tumor cell growth, representing a promising avenue for promoting senescence and treating cancer.

Influencing inter-cellular junctions with nanomaterials

Cell-cell junctions are essential for maintaining tissue integrity and regulating a wide range of physiological processes. While the disruption of intercellular junctions may lead to pathological conditions, it also presents an opportunity for therapeutic interventions. Nanomaterials have emerged as promising tools for modulating cell-cell junctions, offering new avenues for innovative treatments. In this review, we provide a comprehensive overview of the various nanomaterials interaction with cell-cell junctions. We discussed their underlying mechanisms, heterogenous effects on cellular behavior, and the therapeutic strategies of applying nanomaterial-induced intercellular junction disruption. Additionally, we address the challenges and opportunities involved in translating these strategies into clinical practice and discuss future directions for this rapidly advancing field.

Construction of Smart DNA-Based Drug Delivery Systems for Cancer Therapy

Due to the disadvantages of poor targeting, slow action, and low effectiveness of current commonly used cancer treatments, including surgery, chemotherapy, and radiotherapy, researchers have turned to DNA as a biomaterial for constructing drug delivery nanocarriers. DNA is favored for its biocompatibility and programmability. In order to overcome the limitations associated with traditional drug delivery systems (DDSs), researchers have developed smart-responsive DNA DDSs that can control drug release in response to specific physical or chemical stimuli at targeted sites. In this review, a summary of multiple targeted ligand structures is provided, various shapes of stable DNA nanomaterials, and different stimuli-responsive drug release strategies in DNA DDSs. Specifically, targeted cell recognition, in vivo stable transport, and controlled drug release of smart DDSs are focused. Finally, the further development prospects and challenges of clinical application of DNA nanomaterials in the field of smart drug delivery are discussed. The objective of this review is to enhance researchers' comprehension regarding the potential application of DNA nanomaterials in precision drug delivery, with the aim of expediting the clinical implementation of intelligent DDSs.

Hairpin DNA-Based Nanomaterials for Tumor Targeting and Synergistic Therapy

Background

While nanoplatform-based cancer theranostics have been researched and investigated for many years, enhancing antitumor efficacy and reducing toxic side effects is still an essential problem.

Methods

We exploited nanoparticle coordination between ferric (Fe2+) ions and telomerase-targeting hairpin DNA structures to encapsulate doxorubicin (DOX) and fabricated Fe2+-DNA@DOX nanoparticles (BDDF NPs). This work studied the NIR fluorescence imaging and pharmacokinetic studies targeting the ability and biodistribution of BDDF NPs. In vitro and vivo studies investigated the nano formula's toxicity, imaging, and synergistic therapeutic effects.

Results

The enhanced permeability and retention (EPR) effect and tumor targeting resulted in prolonged blood circulation times and high tumor accumulation. Significantly, BDDF NPs could reduce DOX-mediated cardiac toxicity by improving the antioxidation ability of cardiomyocytes based on the different telomerase activities and iron dependency in normal and tumor cells. The synergistic treatment efficacy is enhanced through Fe2+-mediated ferroptosis and the β-catenin/p53 pathway and improved the tumor inhibition rate.

Conclusion

Harpin DNA-based nanoplatforms demonstrated prolonged blood circulation, tumor drug accumulation via telomerase-targeting, and synergistic therapy to improve antitumor drug efficacy. Our work sheds new light on nanomaterials for future synergistic chemotherapy.

Telomerase: a nexus between cancer nanotherapy and circadian rhythm

Cancer represents a complex disease category defined by the unregulated proliferation and dissemination of anomalous cells within the human body. According to the GLOBOCAN 2020 report, the year 2020 witnessed the diagnosis of approximately 19.3 million new cases of cancer and 10.0 million individuals succumbed to the disease. A typical cell eventually becomes cancerous because of a long-term buildup of genetic instability and replicative immortality. Telomerase is a crucial regulator of cancer progression as it induces replicative immortality. In cancer cells, telomerase inhibits apoptosis by elongating the length of the telomeric region, which usually protects the genome from shortening. Many nanoparticles are documented as being available for detecting the presence of telomerase, and many were used as delivery systems to transport drugs. Furthermore, telomere homeostasis is regulated by the circadian time-keeping machinery, leading to 24-hour rhythms in telomerase activity and TERT mRNA expression in mammals. This review provides a comprehensive discussion of various kinds of nanoparticles used in telomerase detection, inhibition, and multiple drug-related pathways, as well as enlightens an imperative association between circadian rhythm and telomerase activity from the perspective of nanoparticle-based anticancer therapeutics.

Targeting Telomere Dynamics as an Effective Approach for the Development of Cancer Therapeutics

Telomere is a protective structure located at the end of chromosomes of eukaryotes, involved in maintaining the integrity and stability of the genome. Telomeres play an essential role in cancer progression; accordingly, targeting telomere dynamics emerges as an effective approach for the development of cancer therapeutics. Targeting telomere dynamics may work through multifaceted molecular mechanisms; those include the activation of anti-telomerase immune responses, shortening of telomere lengths, induction of telomere dysfunction and constitution of telomerase-responsive drug release systems. In this review, we summarize a wide variety of telomere dynamics-targeted agents in preclinical studies and clinical trials, and reveal their promising therapeutic potential in cancer therapy. As shown, telomere dynamics-active agents are effective as anti-cancer chemotherapeutics and immunotherapeutics. Notably, these agents may display efficacy against cancer stem cells, reducing cancer stem levels. Furthermore, these agents can be integrated with the capability of tumor-specific drug delivery by the constitution of related nanoparticles, antibody drug conjugates and HSA-based drugs.

Regulator-carrying dual-responsive integrated AuNP composite fluorescence probe for in situ real time monitoring apoptosis progression

Apoptosis is a typical programmed death mode with complex molecular regulation mechanisms. Developing advanced strategies to monitor apoptosis progression is conducive to disease treatment related with apoptosis. Herein, we developed a regulator-carrying dual-responsive integrated AuNP composite fluorescence probe for in situ real time monitoring apoptosis progression. The nanoprobe is constructed by modifying specially designed double-stranded DNA (dsDNA) and caspase 3-specific cleavable peptides (pep) to the surface of AuNP. After uptake by cells, the nanoprobe recognizes miRNA 21 and triggers fluorescence recovery, enabling silencing and imaging of the upstream signaling molecule miRNA 21. Once miRNA 21 is silenced, the downstream signaling molecule caspase 3 is activated and cleaves the substrate peptides, and fluorescence is restored for in situ imaging of caspase 3. The apoptosis induced by silencing miRNA 21 has been successfully implemented in HeLa and A549 cells. The expression level of miRNA 21 and corresponding changes of caspase 3 have also been effectively monitored. These results suggested this nanoprobe will be a potential tool for apoptosis-related biomedical research and clinical application.

Fluorescence Biosensing Based on Bifurcated DNA Scaffold-Aggregated Ag Nanocluster via Responsive Conformation Switch of Quasi-Molecular Beacon

To address the limitations of typical hairpin-structural molecular beacons, exploring the ability of a quasi-molecular beacon (qMB) to create label-free fluorescence biosensors is intriguing and remains a challenge. Herein, we propose the first example of modular qMB with the feature of a stimulation-responsive conformation switch to develop an aggregated Ag nanocluster (aAgNC) in a bifurcated DNA scaffold for fluorescently sensing a specific initiator (I*). This qMB was well designed to program four functional modules: I*-recognizable element adopting metastable stem-loop bihairpin structure and two DNA splits (exposed C3GT4 and locked C4AC4T) of aAgNC template that is separated by a tunable hairpin spacer for the customized combination of selective recognition and signaling readout. When presenting I* in an assay route, the specific hybridization induces the directional disassembly of the bihairpin unit, on which the qMB is configurationally switched to liberate the locked split. Thus, the bifurcated parent template pair of C3GT4/C4AC4T is proximal, affording in situ nucleation and clustering of emissive aAgNC. By collecting the fluorescence signal, the quantitative detection of I* is achieved. Benefiting from the ingenious programming of qMB, the recognizing and signaling integration actuates the construction of a facile and convenient fluorescent biosensor featuring rapid reaction kinetics, a wide linear range, high sensitivity, and specificity. This would provide a new paradigm to exploit versatile qMB-based biosensing platforms via stimulation-responsive conformation switches for developing various DNA-scaffolded Ag clusters.

CuS quantum dots activated DNAzyme for ratiometric electrochemical detection of telomerase activity

Telomerase activity detection has attracted much attention concerning its importance for early cancer diagnosis. Here, we established a ratiometric electrochemical biosensor for telomerase detection based on CuS quantum dots (CuS QDs) dependent DNAzyme-regulated dual signals. The telomerase substrate probe was used as the linker to combine the DNA fabricated magnetic beads and CuS QDs. In this way, telomerase extended the substrate probe with repeated sequence to from hairpin structure, releasing CuS QDs as an input to DNAzyme modified electrode. DNAzyme was cleaved with high current of ferrocene (Fc) and low current of methylene blue (MB). On the basis of the obtained ratiometric signals, telomerase activity detection was achieved in the range of 1.0 × 10^-12-1.0 × 10^-6 IU/L, with the limit of detection down to 2.75 × 10^-14 IU/L. Moreover, telomerase activity from HeLa extracts was also tested to verify the clinical application.

Entropy-Driven Three-Dimensional DNA Nanofireworks for Simultaneous Real-Time Imaging of Telomerase and MicroRNA in Living Cells

Real-time monitoring of different types of intracellular tumor-related biomarkers is of key importance for the identification of tumor cells. However, it is hampered by the low abundance of biomarkers, inefficient free diffusion of reactants, and complex cytoplasmic milieu. Herein, we present a stable and general method for in situ imaging of microRNA-21 and telomerase utilizing simple highly integrated dual tetrahedral DNA nanostructures (TDNs) that can naturally enter cells, which could initiate to form the three-dimensional (3D) higher-order DNA superstructures (DNA nanofireworks, DNFs) through a reliable target-triggered entropy-driven strand displacement reaction in living cells for remarkable signal amplification. Importantly, the excellent biostability, biocompatibility, and sensitivity of this approach benefited from (i) the precise multidirectional arrangement of probes with a pure DNA structure and (ii) the local target concentration enhanced by the spatially confined microdomain inside the DNFs. This strategy provides a pivotal molecular toolbox for broad applications such as biomedical imaging and early precise cancer diagnosis.

Nanomaterials in anticancer applications and their mechanism of action - A review

The current challenges in cancer treatment using conventional therapies have made the emergence of nanotechnology with more advancements. The exponential growth of nanoscience has drawn to develop nanomaterials (NMs) with therapeutic activities. NMs have enormous potential in cancer treatment by altering the drug toxicity profile. Nanoparticles (NPs) with enhanced surface characteristics can diffuse more easily inside tumor cells, thus delivering an optimal concentration of drugs at tumor site while reducing the toxicity. Cancer cells can be targeted with greater affinity by utilizing NMs with tumor specific constituents. Furthermore, it bypasses the bottlenecks of indiscriminate biodistribution of the antitumor agent and high administration dosage. Here, we focus on the recent advances on the use of various nanomaterials for cancer treatment, including targeting cancer cell surfaces, tumor microenvironment (TME), organelles, and their mechanism of action. The paradigm shift in cancer management is achieved through the implementation of anticancer drug delivery using nano routes.

DNA-enabled fluorescent-based nanosensors monitoring tumor-related RNA toward advanced cancer diagnosis: A review

As a burgeoning non-invasive indicator for reproducible cancer diagnosis, tumor-related biomarkers have a wide range of applications in early cancer screening, efficacy monitoring, and prognosis predicting. Accurate and efficient biomarker determination, therefore, is of great importance to prevent cancer progression at an early stage, thus reducing the disease burden on the entire population, and facilitating advanced therapies for cancer. During the last few years, various DNA structure-based fluorescent probes have established a versatile platform for biological measurements, due to their inherent biocompatibility, excellent capacity to recognize nucleic and non-nucleic acid targets, obvious accessibility to synthesis as well as chemical modification, and the ease of interfacing with signal amplification protocols. After decades of research, DNA fluorescent probe technology for detecting tumor-related mRNAs has gradually grown to maturity, especially the advent of fluorescent nanoprobes has taken the process to a new level. Here, a systematic introduction to recent trends and advances focusing on various nanomaterials-related DNA fluorescent probes and the physicochemical properties of various involved nanomaterials (such as AuNP, GO, MnO2, SiO2, AuNR, etc.) are also presented in detail. Further, the strengths and weaknesses of existing probes were described and their progress in the detection of tumor-related mRNAs was illustrated. Also, the salient challenges were discussed later, with a few potential solutions.

Fast detection, a precise and sensitive diagnostic agent for breast cancer

Background

Breast cancer targeting diagnostic agent with effective imaging ability is important in guiding plan formulation, prediction, and curative effect evaluation of tumors in clinic. A tumor-targeting nanoprobe based on the functional and programmable Liquid–Liquid phase separation of AS1411 promoted by Ru(II) complex RuPEP may develop into a potential phosphorescence probe to detect breast cancer cells, where AS1411 act as a tumor-targeting guidance moiety to distinguish tumor cells from normal cells and RuPEP act as a light-emitting element to highlight breast cancer cells.

Methods

Here we designed and constructed a nanoprobe AS1411@RuPEP, and the physicochemical and biochemical properties were characterized by TEM, AFM and EDS. The breast cancer targeting diagnostic capacity was evaluated by normal/tumor cell co-culture assay, tumor cells targeting tracking in xenograft model and cancerous area selectively distinguishing in human patient tissue.

Results

Further studies indicated that the nanoprobe exhibits excellent tumor-targeting imaging ability in vitro and in vivo by effectively recognize the over-expressed nucleolin (NCL) on the breast cancer cells membrane. Intriguingly, we discovered that the selectively enrichment of nanoprobe particles in tumor cells is related to ATP-dependent NCL transport processes that rely on the AS1411 component of nanoprobe to recognize NCL. Furthermore, preferential accumulation of nanoprobe is clearly differentiating the human breast cancer tissue surrounding non-cancerous tissue in histological analysis.

Conclusion

This study produce a potent nanoprobe can be used as a convenient tool to highlight and distinguish tumor cells in vivo, and indicate the tumorous grading and staging in human breast cancer patient pathological section, which provides an effective way for breast cancer diagnostic imaging by targeting recognize NCL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13046-022-02393-3.

Outward Movement of Targeting Ligands from a Built-In Reserve Pool in Nuclease-Resistant 3D Hierarchical DNA Nanocluster for in Vivo High-Precision Cancer Therapy

Nanostructures made entirely of DNAs display great potential as chemotherapeutic drug carriers but so far cannot achieve sufficient clinic therapy outcomes due to off-target toxicity. In this contribution, an aptamer-embedded hierarchical DNA nanocluster (Apt-eNC) is constructed as an intelligent carrier for cancer-targeted drug delivery. Specifically, Apt-eNC is designed to have a built-in reserve pool in the interior cavity from which aptamers may move outward to function as needed. When surface aptamers are degraded, ones in reserve pool can move outward to offer the compensation, thereby magically preserving tumor-targeting performance in vivo. Even if withstanding extensive aptamer depletion, Apt-eNC displays a 115-fold enhanced cell targeting compared with traditional counterparts and at least 60-fold improved tumor accumulation. Moreover, one Apt-eNC accommodates 5670 chemotherapeutic agents. As such, when systemically administrated into HeLa tumor-bearing BALB/c nude mouse model, drug-loaded Apt-eNC significantly inhibits tumor growth without systemic toxicity, holding great promise for high precision therapy.

Aptamer-Gold Nanocage Composite for Photoactivated Immunotherapy

Immune checkpoint blockade (ICB) has been hailed as the hope for conquering cancer as ICB could produce a significant and durable response to tumor cells. However, the high cost and severe side effects of ICB drugs limited their application for further anticancer therapy. Here, we developed a photoactivated immunotherapy nanoplatform (Apt@AuNC). This nanoplatform could target tumor tissues via enhanced penetration retention (EPR) effect and the aptamer (Apt) could be released from Apt@AuNC in tumor sites via illumination. The immune system in the tumor area was then activated after the combination of Apt and PD-1 protein. The heat generated from AuNC was able to continue killing tumor cells. This nanoplatform could not only achieve the precise immunotherapy but also significantly facilitate the anticancer efficacy.

A primer extension activating 3D DNAzyme walker for in situ imaging and sensitive detection of telomerase activity

Acquiring information on telomerase activity at multiple levels contributes to a better understanding of its role in various physiological and pathological processes. Herein, a primer extension activating 3D DNAzyme walker is developed for in situ imaging and sensitive detection of telomerase activity. This walker is constructed via co-modifying specially designed hairpin structured walking strands and track strands on a gold nanoparticle (AuNP). The walking strand contains a pre-blocked DNAzyme sequence and a telomerase primer hybridized to its root. The track strand embeds at an RNA cleavage site and is labeled with the FAM group. After this walker is taken up by cells, the telomerase primer is extended under the action of endogenous telomerase to liberate DNAzyme. The liberated DNAzyme cuts track strands in the presence of the cofactor Mn²⁺ to drive the walker's processive operation, resulting in an enhanced fluorescence recovery of the AuNP-quenched FAM fluorophore. In situ imaging of telomerase activity in three different cell lines (MCF-7 cells, HeLa cells and HL-7702 cells) was well implemented. The discrimination of cancer cells from normal cells and the screening of telomerase inhibitors have been achieved. The sensitive detection of telomerase activity in HeLa cell lysate has also been realized with a detection limit of 10 cells. This walker performed a new approach for monitoring telomerase activity from different levels, providing a potential tool for clinical diagnosis, prognostic evaluation and drug screening.

Nucleic acid functionalized extracellular vesicles as promising therapeutic systems for nanomedicine

Extracellular vesicles (EVs), as natural carriers, are regarded as a new star in nanomedicine due to their excellent biocompatibility, fascinating physicochemical properties, and unique biological regulatory functions. However, there are still some challenges to using natural EVs, including poor targeting ability and the clearance from circulation, which may limit their further development and clinical use. Nucleic acid has the functions of programmability, targeting, gene therapy, and immune regulation. Owing to the engineering design and modification by integrating functional nucleic acid, EVs offer excellent performances as a therapeutic system in vivo. This review briefly introduces the function and mechanism of nucleic acid in the diagnosis and treatment of diseases. Then, the strategies of nucleic acid-functionalized EVs are summarized and the latest progress of nucleic acid-functionalized EVs in nanomedicine is highlighted. Finally, the challenges and prospects of nucleic acid-functionalized EVs as a promising diagnostic system are proposed.

Dynamic tracking of p21 mRNA in living cells by sticky-flares for the visual evaluation of the tumor treatment effect

Monitoring the expression level of the intracellular tumor suppressor gene p21 mRNA is essential to reveal the progress and prognosis of a tumor. Methods widely reported for the detection of p21 mRNA are the real-time polymerase chain reaction and Northern blot. However, these methods only detect mRNA in vitro and cannot realize the in situ monitoring of the p21 mRNA expression level in living cells. Additionally, the sensor for the real-time tracking and monitoring of the p21 mRNA location without the help of a transfection reagent in living cells is still limited. Herein, a novel sticky-flare was constructed for the dynamic monitoring of the temporal and spatial variations of p21 mRNA in living cells. The nanoprobe consists of AuNP, a recognition sequence modified with Cy5, and a thiol-modified DNA sequence. The thiol oligonucleotide strand could act partially complementary to the Cy5-modified oligonucleotide strand to form a double-stranded DNA linked to AuNP, resulting in the fluorescence quenching of Cy5 due to the energy transfer from Cy5 to the gold sphere. In the presence of p21 mRNA, the Cy5-modified recognition nucleic acid specifically bound to p21 mRNA to form a more stable double chain and escaped from the gold sphere, leading to the recovery of red fluorescence. Our method is better than other methods in its ability to quantify the spatial distribution and expression level of p21 mRNA in living cells and discriminate various tumor cell lines with different p21 mRNA expression levels by the naked eye. Particularly, the sticky-flare probe used in this assay could allow the visual evaluation of the tumor treatment effect and the determination of the tumor progression stage by enabling monitoring of the relative expression level of p21 mRNA in tumor cells after cisplatin treatment. The method reported here is accurate, reliable and needs no auxiliary tools (transfection reagent), and thereby provides a promising route for the prognostic evaluation and drug development of cancer treatment in the future.

A versatile fluorescent nanobeacon lighted by DNA-templated copper nanoparticles and the application in isothermal amplification detection

In this work, an environmentally-friendly and versatile nanobeacon was constructed by utilizing DNA-templated copper nanoparticles (CuNPs) as fluorescence signal source. As the key component of the nanobeacon, a hairpin DNA was designed to contain four segments: two segments for CuNPs template sequence, a target recognition segment and a blocking segment. At room temperature, the target recognition segment partly hybridizes with the blocking segment and thus prohibits the formation of double stranded DNA template, so that no CuNPs can be generated on the hairpin DNA. While a target is introduced, the specific binding of target with recognition sequence triggers off the conformational transformation of the hairpin DNA, which contributes to the formation of the CuNPs template. As a result, the in-situ generation of CuNPs gives birth to the fluorescence signal readout that can be used to identify the target. By reasonably varying the recognition sequence within hairpin DNA, a series of nanobeacons in response to corresponding targets, such as DNA, microRNA, thrombin, and ATP, were put forward with satisfactory sensitivity and selectivity. Moreover, this nanobeacon was also integrated with the strategy of enzyme-assisted target-recycling to realize signal amplification and ultrasensitive detection, which further demonstrated the versatility of the nanobeacon. This novel nanobeacon is expected to be a promising alternative to classical dye-labeled molecular beacon and provide new perspective on ultrasensitive fluorescence sensing.

Recent advances of fluorescent biosensors based on cyclic signal amplification technology in biomedical detection

The cyclic signal amplification technology has been widely applied for the ultrasensitive detection of many important biomolecules, such as nucleic acids, proteins, enzymes, adenosine triphosphate (ATP), metal ions, exosome, etc. Due to their low content in the complex biological samples, traditional detection methods are insufficient to satisfy the requirements for monitoring those biomolecules. Therefore, effective and sensitive biosensors based on cyclic signal amplification technology are of great significance for the quick and simple diagnosis and treatment of diseases. Fluorescent biosensor based on cyclic signal amplification technology has become a research hotspot due to its simple operation, low cost, short time, high sensitivity and high specificity. This paper introduces several cyclic amplification methods, such as rolling circle amplification (RCA), strand displacement reactions (SDR) and enzyme-assisted amplification (EAA), and summarizes the research progress of using this technology in the detection of different biomolecules in recent years, in order to provide help for the research of more efficient and sensitive detection methods.

Design and Preparation of "corn-like" SPIONs@DFK-SBP-M13 Assembly for Improvement of Effective Internalization

Purpose

Superparamagnetic iron oxide nanoparticles (SPIONs) have exhibited preeminent diagnosis and treatment performances, but their low internalization severely limits predesigned functions. The low cell internalization is now an urgent bottleneck problem for almost all nanomaterials. To achieve more internalization of SPIONS, recombinant M13 phage was designed for targeted delivery and smart release.

Methods

M13 phages were designed to co-express exogenous SPARC binding peptide (SBP) and cathepsin B cleavage peptide (DFK), formed recombinant DFK-SBP-M13. 3.37± 0.06 nm of SPIONs were modified by 3, 4-dihydroxyhydrocinnamic acid (DHCA) to gain 10.80 ± 0.21 nm of DHCA-coated SPIONs, i.e., DHCA@SPIONs. Upon adjusting the proportions of DHCA@SPIONs and DFK-SBP-M13, the multi-carboxyl SPIONs assembled onto recombinant M13 phages via covalent bonding. The assemblies were co-cultured with MDA-MB-231 cells to interpret their internalization and smart release.

Results

The “corn-like” SPIONs@DFK-SBP-M13 (261.47±3.30 nm) assemblies have not been reported previously. The assembly was stable, dispersible, superparamagnetic and biocompatible. After co-cultivation with MDA-MB-231 cells, the SPIONs@DFK-SBP-M13 assemblies quickly bond to the cell surface and are internalized. The enrichment rate of SPIONs@DFK-SBP-M13 assembly was 13.9 times higher than free SPIONs at 0.5 h, and intracellular Fe content was 3.6 times higher at 1 h. Furthermore, the DFK peptides favored cathepsin B to cleave SPIONs from the M13 templates resulting in release of SPIONs inside cells.

Conclusion

The novel SPIONs@DFK-SBP-M13 assembly can rapidly deliver SPIONs to the targeted sites and enabled smart release. The combination of genetic recombination and nanotechnology is beneficial for designing and optimizing some new nanomaterials with special functions to achieve wider applications.

A mismatch-suppressed, duplex-specific nuclease powered nanowalker for multiplexed sensing of microRNA

DNA molecular machines have attracted immense interest for their potential in biosensing, drug delivery, and cellular imaging. Herein, we report a duplex-specific nuclease (DSN) powered nanowalker that can autonomously and progressively move on a spherical three-dimensional track, which is constructed by functionalizing a 13 nm diameter gold nanoparticle (AuNP) with densely mismatched DNA duplexes. The motion is initiated by an RNA walking strand, and in its absence, the walker is suppressed because the DSN is inactive toward the mismatched DNA duplexes. Once the walking strand is added, perfectly matched DNA-RNA hybrid is formed via a toehold-mediated displacement reaction between the walking strand and mismatched duplex. Thereafter, the DNA-RNA hybrid is simultaneously cleaved by DSN, by releasing the walking strand, which autonomously moves on the track with the aid of DSN. The present study provides a novel energy input and power mechanism for the operation of 3-D nanowalker with high efficiency. Moreover, the proposed nanowalker can be designed in a target microRNA (miRNA)-specific manner by altering the mismatched duplexes, and it exhibits femtomole level sensitivity in both singleplexed and multiplexed sensing of three miRNA targets. In addition, multiplexed quantification of the three miRNAs in biological samples is achieved, further suggesting that the proposed nanowalker has immense potential in biomedical research and early diagnosis of clinical disorders.

Nucleic acid-driven aggregation-induced emission of Au nanoclusters for visualizing telomerase activity in living cells and in vivo

Visual monitoring of telomerase activity in living cancer cells and in vivo is essential for clinical diagnosis and treatment. However, most detection methods were performed in vitro due to the difficulty of probes entering cells and the interferences from complex biological environments. Herein, we developed a novel probe based on Au nanoclusters (AuNCs) with a nucleic acid-driven aggregation-induced emission (AIE) property for the first time. The probe was applied for detection of telomerase with high sensitivity. Importantly, the probe could achieve telomerase imaging in living cells and in solid tumor tissue in vivo. The study provided a specific connection fashion of metal nanoclusters for AIE generation. It holds great potential for the development of AIE-active metal nanoclusters as a diagnostic tool for disease detection in vitro as well as in vivo.

Facile Preparation of a Hairpin DNA-Gold Nanoparticle Monoconjugate with a Single-Dye Molecule and Lactobionic Acid as Targeting Ligand

We established a new design for a single molecular beacon-conjugated gold nanoparticle, named monoMB-GNP, which showed enhanced fluorescence emission only in the presence of the complementary DNA sequence. MonoMB-GNP also showed no apparent toxicity to NIH/3T3 cells at 1 nM, as determined by the water-soluble tetrazolium assay. Importantly, the lactobionic acid was successfully modified on the surface of monoMB-GNP. The proposed nanoparticle has prospects for use in several applications for targetable molecular beacon strategies.

Self-assembled nanomaterials for biosensing and therapeutics: recent advances and challenges

Self-assembled nanomaterials (SANs) exhibit designable biofunctions owing to their tunable nanostructures and modifiable surface. Various constituent units and multi-dimensional structures of SANs provide unlimited possibilities for numerous applications. This review emphasizes the recent development of SANs in the fields of biosensing, bioimaging, and nano-drug engineering. The unit type, design concepts, material advantages, assembly driving force, nanostructure effects, drug loading performance, etc. are discussed and summarized. Finally, we briefly summarize how to assemble unique nanomaterials and point out the key challenges in this field.

A stepwise recognition strategy for the detection of telomerase activity via direct electrochemical analysis of metal-organic frameworks

The detection of telomerase is of great significance for monitoring cell canceration. The conventional methods depend on the extension of telomerase towards its primer to conduct signal transduction. Herein, a specific and reliable detection strategy based on stepwise recognition was developed for tandem detection of metal ions and enzymes. We first synthesized an electrically active metal-organic framework (MIL-101(Fe)), which can act directly as a signal reporter in phosphate buffered saline after being modified with capture DNA (cDNA). When the zinc ion is added as a coenzyme factor, the modified hairpin DNA on the electrode is cleaved by DNAzyme to yield the activated primer. After the addition of telomerase, the cleaved DNA strand would be extended, and the resulting sequence will be hybridized with the signal label of MIL-101(Fe)-cDNA. Therefore, a signal-on strategy for the detection of telomerase was achieved based on the direct electrochemical analysis of MIL-101(Fe). Moreover, this electrochemical biosensor can discriminate telomerase activity among different cell lines. The stepwise recognition ensured the advantages of an electrochemical biosensor such as high sensitivity and specificity during the detection process, providing a novel method for monitoring and diagnosis of diseases.

Supramolecular cancer nanotheranostics

Among the many challenges in medicine, the treatment and cure of cancer remains an outstanding goal given the complexity and diversity of the disease. Nanotheranostics, the integration of therapy and diagnosis in nanoformulations, is the next generation of personalized medicine to meet the challenges in precise cancer diagnosis, rational management and effective therapy, aiming to significantly increase the survival rate and improve the life quality of cancer patients. Different from most conventional platforms with unsatisfactory theranostic capabilities, supramolecular cancer nanotheranostics have unparalleled advantages in early-stage diagnosis and personal therapy, showing promising potential in clinical translations and applications. In this review, we summarize the progress of supramolecular cancer nanotheranostics and provide guidance for designing new targeted supramolecular theranostic agents. Based on extensive state-of-the-art research, our review will provide the existing and new researchers a foundation from which to advance supramolecular cancer nanotheranostics and promote translationally clinical applications.

Different Approaches to Develop Nanosensors for Diagnosis of Diseases

The success of clinical treatments is highly dependent on early detection and much research has been conducted to develop fast, efficient, and precise methods for this reason. Conventional methods relying on nonspecific and targeting probes are being outpaced by so-called nanosensors. Over the last two decades a variety of activatable sensors have been engineered, with a great diversity concerning the operating principle. Therefore, this review delineates the achievements made in the development of nanosensors designed for diagnosis of diseases.

Intracellular Nonenzymatic In Situ Growth of Three-Dimensional DNA Nanostructures for Imaging Specific Biomolecules in Living Cells

Real-time in situ monitoring of low-abundance cancer biomarkers (e.g., miRNAs and proteins) in living cells by nonenzymatic assembly entirely from original DNA probes remains unexplored due to an extremely complex intracellular environment. Herein, a nonenzymatic palindrome-catalyzed DNA assembly (NEPA) technique is developed to execute the in situ imaging of intracellular miRNAs by assembling a three-dimensional nanoscale DNA spherical structure (NS) with low mobility from three free hairpin-type DNAs rather than from DNA intermediates based on the interaction of designed terminal palindromes. Target miRNA was detected down to 1.4 pM, and its family members were distinguished with almost 100% accuracy. The subcellular localization of NS products can be visualized in real time. The NEPA-based sensing strategy is also suitable for the intracellular in situ fluorescence imaging of cancer-related protein receptors, offering valuable insight into developing sensing protocols for understanding the biological function of vital biomolecules in disease pathogenesis and future therapeutic applications.

Periodically Ordered, Nuclease-Resistant DNA Nanowires Decorated with Cell-Specific Aptamers as Selective Theranostic Agents

DNA nanostructures have shown potential in cancer therapy. However, their clinical application is hampered by the difficulty to deliver them into cancer cells and susceptibility to nuclease degradation. To overcome these limitations, we report herein a periodically ordered nick-hidden DNA nanowire (NW) with high serum stability and active targeting functionality. The inner core is made of multiple connected DNA double helices, and the outer shell is composed of regularly arranged standing-up hairpin aptamers. All termini of the components are hidden from nuclease attack, whereas the target-binding sites are exposed to allow delivery to the cancer target. The DNA NW remained intact during incubation for 24 h in serum solution. Animal imaging and cell apoptosis showed that NWs loaded with an anticancer drug displayed long blood-circulation time and high specificity in inducing cancer-cell apoptosis, thus validating this approach for the targeted imaging and therapy of cancers.

Structure-Switchable DNA Programmed Disassembly of Nanoparticles for Smart Size Tunability and Cancer-Specific Drug Release

The size of the nanocarrier is considered one of the most important issues for its therapeutic effect. Thus, an intelligent nanocarrier with dynamic size has been explored as a promising approach to fulfill the requirements for both efficient accumulation according to the enhanced penetration and retention (EPR) effect and deep penetration into tumor tissue. Herein, structure-switchable triplex DNA was modified on gold nanoparticles (AuNPs) to investigate its potential to modulate the nanoparticle dynamic disassembly process among the tumor microenvironment. We report that the pH-sensitive triplex DNA exhibited outstanding sensitivity and size tunability in triggering the disassembly of AuNP clusters into smaller sizes among the tumor acidic environment, leading to better permeability both in vitro and in vivo. By further combination of the telomerase-sensitive hairpin DNA loaded with chemotherapy drug doxorubicin (DOX), a cancer-specific intracellular drug-release function was also realized, resulting in a precise treatment effect and lower toxicity on normal cells. Through comodification of these two structure-switchable DNA chains on AuNPs and construction of nanoparticle assemblies with proper size, programmed disassembly and drug-release function in tissue and cell level, respectively, were successfully combined and eventually facilitated a highly efficient nanodrug transportation process, from tumor accumulation to deep penetration and precise cancer chemotherapy. The study provided the prospect of utilizing functionalized DNA in optimization of nanocarrier delivery efficiency.

An intelligent nanodevice based on the synergistic effect of telomerase-triggered photodynamic therapy and gene-silencing for precise cancer cell therapy

The development of intelligent and precise cancer therapy systems that enable accurate diagnosis and specific elimination of cancer cells while protecting normal cells to improve the safety and effectiveness of the treatment is still a challenge. Herein, we report a novel activatable nanodevice for precise cancer therapy. The nanodevice is constructed by adsorbing a DNA duplex probe onto MnO2 nanosheets. After cellular uptake, the DNA duplex probe undergoes telomerase-triggered conformation switching, resulting in a Ce6 "turn-on" signal for the identification of cancer cells. Furthermore, Deoxyribozyme (DNAzyme) is activated to catalyse the cleavage of survivin mRNA, actualizing a precise synergistic therapy in cancer cells involving photodynamic therapy and gene-silencing. The MnO2 nanosheets provide Mn2+ for the DNAzyme and relieve hypoxia to improve the efficiency of the photodynamic therapy. Live cell studies reveal that this nanodevice can diagnose cancer cells and specifically eliminate them without harming normal cells, so making the treatment safer and more effective. The developed DNA-MnO2 nanodevice provides a valuable and general platform for precise cancer therapy.

Mannoside-Modified Branched Gold Nanoparticles for Photothermal Therapy to MDA-MB-231 Cells

Recently, gold nanoparticles (Au NPs) have been used to study the treatment of malignant tumors due to their higher biocompatibility and lesser toxicity. In addition, they can be excited through a specific wavelength to produce oscillating plasmonic photothermal therapy (PPTT) on the basis of the localized surface plasma resonance (LSPR) effect. Au NPs can be heated to kill cancer cells in specific parts of the body in a noninvasive manner. In this study, branched gold nanoparticles (BAu NPs) were prepared by mixing HAuCl₄ in a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) buffer solution in a molar ratio of 1:2000. The UV–vis absorption peak was detected in the range of 700–1000 nm. Subsequently, BAu NPs were chemically linked to a thiol-modified mannoside molecule via a stable sulfur–Au covalent bond (Man@BAu NPs). Due to the presence of abundant mannose receptors on human-breast-cancer cells, MDA-MB-231, Man@BAu NPs were found to be abundant inside cancer cells. After irradiating the Man@BAu NP-laden MDA-MB231 switch with a near-infrared (NIR) laser at 808 nm wavelength, the photothermal-conversion effect raised the surface temperature of Man@BAu NPs, thus inducing cell death. Our experiment results demonstrated the advantages of applying Man@BAu NPs in inducing cell death in MDA-MB-231.

Live-Cell Sensing of Telomerase Activity by Using Hybridization-Sensitive Fluorescent Oligonucleotide Probes

Live-cell sensing of telomerase activity with simple and efficient strategies remains a challenging target. In this work, a strategy for telomerase sensing by using hybridization-sensitive fluorescent oligonucleotide probes is reported. In the presence of telomerase and dNTPs, the designed supporting strand was extended and generated the hairpin structure that catalyzed the next telomerase extending reaction. The special extension mechanism increased the local concentration of another supporting strand and telomerase, which resulted in enhanced telomerase activity. The hybridization-sensitive oligonucleotide probes bound to the hairpin catalyst and generated turn-on fluorescence. This method realized the sensing of telomerase activity in HeLa cell extract with a detection limit below 1.6×10^-6  IU μL^-1 . The real-time in situ observation of telomerase extension was achieved in living HeLa cells. This strategy has been applied to monitor the efficiency of telomerase-targeting anticancer drugs in situ.

Tumor-Oriented Telomerase-Terminated Nanoplatform as Versatile Strategy for Multidrug Resistance Reversal in Cancer Treatment

Multidrug resistance is one of the major problems in chemotherapy, and exploiting impactful targets to reverse drug resistance of most tumors remains a difficult problem. In this study, the tumor-oriented nanoparticle, BIBR1532-loaded peptide dendrimeric prodrug nanoassembly (B-PDPN), is used to assist telomerase inhibition for multidrug resistance reversal. B-PDPN possesses the characteristics of an acid-activated histidine to promote cellular uptake, a redox-sensitive poly(ethylene glycol) (PEG) layer to actualize endosomal escape and telomerase inhibitor release, and an acid sensitive chemical bond to facilitate chemotherapeutic drug release. Telomerase termination weakens the protective effect of hTERT protein on mitochondria and enhances reactive oxygen species (ROS) production, which increases DNA damage and apoptosis. The tumor-oriented nanoparticle B-PDPN achieves a broad-spectrum telomerase inhibition to combat multidrug resistance. In vivo experiments support the evidence that B-PDPN accumulates in the tumor site and reduces the expression of hTERT in tumor tissues to inhibit drug resistant tumor growth. This work introduces an innovative strategy of utilizing features of tumor-activated nanoplatform to assist telomerase termination. The nanoplatform enhances intracellular drug concentration and nucleus delivery of doxorubicin (DOX), and promotes DNA damage to combat multidrug resistance.

Acid-Switchable DNAzyme Nanodevice for Imaging Multiple Metal Ions in Living Cells

Metal-assisted deoxyribozyme catalysis (DNAzyme) has been a general platform for constructing highly sensitive and selective detection sensors of metal ions. However, the "always on" mode of the traditional DNAzyme sensors greatly limits their application in the visual analysis of endogenous metal ions in a complex physiological microenvironment. To overcome this obstacle, a smart acid-switchable DNAzyme nanodevice is designed to control the DNAzyme activity in living cells and achieve simultaneous visualization of metal ions (Zn²⁺ and Pb²⁺) in situ. This nanodevice is built on DNAzyme precursors (DPs) and acid-switchable DNA (SW-DNA), precisely responding to pH variations in the range of 4.5-7.0, and the state of the three-strand hybridization of DPs successfully renders the DNAzymes inactive before being transported into cells. Once the nanodevice is taken up into living cells, the SW-DNA will change the configuration from linear to triplex in the acidic intracellular compartments (lysosomes, pH ∼4.5 to 5.0) and then the strands hybridized with the SW-DNA are liberated and subsequently react with DPs to form the active DNAzyme, which can further realize multi-imaging of intracellular metal ions. Moreover, this strategy has broad prospects as a powerful platform for constructing various acid-switchable nanodevices for visual analysis of multiple biomolecules in living cells.