Endogenous Enzyme-Operated Spherical Nucleic Acids for Cell-Selective Protein Capture and Localization Regulation

Tandem-Controlled Dynamic DNA Assembly Enables Temporally-Selective Orthogonal Regulation of cGAS-STING Stimulation

Despite advances in the controlled reconfiguration of DNA structures for biological applications, the dearth of strategies that allow for orthogonal regulation of immune pathways remains a challenge. Here, we report for the first time an endogenous and exogenous tandem-regulated DNA assembly strategy that enables orthogonally controlled stimulation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING) pathway. A DNA motif containing two palindromic sequences is engineered with an abasic site (AP)-connected blocking sequence to inhibit its self-assembly function, while apurinic/apyrimidinic endonuclease 1 (APE1)-triggered enzymatic cleavage of the AP site enables the reconfiguration and self-assembly of DNA motif into long double-stranded structures, thus realizing allosteric activation of the catalytic activity of cGAS to produce 2'3'-cyclic-GMP-AMP for STING stimulation. Importantly, we demonstrate that APE1-regulated DNA assembly allows for cell-selective activation of cGAS-STING signaling. Furthermore, by re-engineering the DNA motif with a photocleavable group, enzyme-triggered DNA assembly allows the cGAS-STING stimulation to operate (switched "ON"), whereas light-mediated fragmentation of the double-stranded DNA enables termination of such stimulation (switched "OFF"), thereby achieving orthogonal control over immune regulation. This work highlights an endogenous and exogenous tandem regulated strategy to modulate the cGAS-STING pathway in an orthogonally controlled manner.

Spherical DNA Nanomotors Enable Ultrasensitive Detection of Active Enzymes in Extracellular Vesicles for Cancer Diagnosis

Enzymes encapsulated in extracellular vesicles (EVs) hold promise as biomarkers for early cancer diagnosis. However, precise measurement of their catalytic activities within EVs remains a notable challenge. Here, we report an enzymatically triggered spherical DNA nanomotor (EDM) that enables one-pot, cascaded, and highly sensitive analysis of the activity of EV-associated or free apurinic/apyrimidinic endonuclease 1 (APE1, a key enzyme in base excision repair) across various biological samples. The EDM capitalizes on APE1-triggered activation of DNAzyme (Dz) and its autonomous cleavage of substrates to achieve nonlinear signal amplification. Using EDM, we demonstrate a strong correlation between APE1 activity in EVs and that of their parental cancer cells. Additionally, EV APE1 mirrors the fluctuation of cellular APE1 activity in response to chemotherapy-induced DNA damage. In a pilot clinical study (n=63), the EDM-based assay reveals that more than 80 % of active APE1 in serum samples is EV-encapsulated. Notably, EV APE1 can differentiate early prostate cancer (PCa) patients from healthy donors (HDs) with an overall accuracy of 92 %, outperforming free APE1 in sera. We anticipate that EDM will become a versatile tool for quantifying EV-associated enzymes.

From Structure to Application: The Evolutionary Trajectory of Spherical Nucleic Acids

Since the proposal of the concept of spherical nucleic acids (SNAs) in 1996, numerous studies have focused on this topic and have achieved great advances. As a new delivery system for nucleic acids, SNAs have advantages over conventional deoxyribonucleic acid (DNA) nanostructures, including independence from transfection reagents, tolerance to nucleases, and lower immune reactions. The flexible structure of SNAs proves that various inorganic or organic materials can be used as the core, and different types of nucleic acids can be conjugated to realize diverse functions and achieve surprising and exciting outcomes. The special DNA nanostructures have been employed for immunomodulation, gene regulation, drug delivery, biosensing, and bioimaging. Despite the lack of rational design strategies, potential cytotoxicity, and structural defects of this technology, various successful examples demonstrate the bright and convincing future of SNAs in fields such as new materials, clinical practice, and pharmacy.

Mirror-Image DNA Nanobox for Enhancing Environment Resistance of Nucleic Acid Probes

Degradation and interference of the nucleic acid probes in complex biological environments like cytoplasm or body fluid can cause obvious false-positive signals and inefficient bioregulation in biosensing and biomedicine. To solve this problem, here, we proposed a universal strategy, termed L-DNA assembly mirror-image box-based environment resistance (L-AMBER), to protect nucleic acid probes from degradation and maintain their responsive activity in complex biological environments. Strand displacement reaction (SDR), aptamer, or DNAzyme-based D-DNA probes were encapsulated into an L-DNA box by using an L-D-L block DNA carrier strand to construct different kinds of L-AMBER probes. We proved that the L-DNA box could effectively protect the encapsulated D-DNA probes by shielding the interference of complex biological environments and only allowing small target molecules to enter for recognition. Compared with the D-AMBER probes, the L-AMBER probes can realize DNase I-assisted amplification detection of biological samples, low false-positive bioimaging, and highly efficient miRNA silence in living cells. Therefore, L-AMBER provided a universal and effective strategy for enhancing the resistance to environmental interference of nucleic acid probes in biosensing and biomedicine applications.

A "dual-key-and-lock" DNA nanodevice enables spatially controlled multimodal imaging and combined cancer therapy

DNA-based theragnostic platforms have attracted more and more attention, while their applications are still impeded by nonspecific interference and insufficient therapeutic efficacy. Herein, we fabricate an integrated "dual-key-and-lock" DNA nanodevice (DKL-DND) which is composed of the inner Dox/Hairpin/Aptazyme-Au@Ag@Au probes and the outer metal-organic frameworks loaded with Fuel strand. Once internalized into human breast cancer cells (MCF-7), the DKL-DND is activated by cascaded endogenous stimuli (acidic pH in the lysosome and high expression of ATP in the cytoplasm), leading to spatially controlled optical/magnetic resonance multimodal imaging and gene/chemo/small molecule combined cancer therapy. By engineering pH and ATP-responsive units as cascaded locks on the DKL-DND, the operating status of the nanodevice and accessibility of encapsulated anti-tumour drugs can be precisely regulated in the specified physiological states, avoiding the premature activation and release during assembly and delivery. Both in vitro and in vivo assessments demonstrate that the DKL-DND with excellent stimuli-responsive ability, biocompatibility, stability and accumulation behaviour was capable of simultaneously affording accurate tumour diagnosis and efficient tumour growth inhibition. This integrated DKL-DND exhibits great promise in constructing self-adaptive nanodevices for multimodal imaging-guided combination therapy.

Engineering Assembly of Plasmonic Virus-Like Gold SERS Nanoprobe Guided by Intelligent Dual-Machine Nanodevice for High-Performance Analysis of Tetracycline

Accurate detection of trace tetracyclines (TCs) in complex matrices is of great significance for food and environmental safety monitoring. However, traditional recognition and amplification tools exhibit poor specificity and sensitivity. Herein, a novel dual-machine linkage nanodevice (DMLD) is proposed for the first time to achieve high-performance analysis of TC, with a padlock aptamer component as the initiation command center, nucleic acid-encoded multispike virus-like Au nanoparticles (nMVANs) as the signal indicator, and cascade walkers circuit as the processor. The existence of spike vertices and interspike nanogaps in MVANs enables intense electromagnetic near-field focusing, allowing distinct surface-enhanced Raman scattering (SERS) activity. Moreover, through the sequential activation between multistage walker catalytic circuits, the DLMD system converts the limited TC recognition into massive engineering assemblies of SERS probes guided by DNA amplicons, resulting in synergistic enhancement of bulk plasmonic hotspot entities. The continuously guaranteed target recognition and progressively promoted signal enhancement ensure highly specific amplification analysis of TC, with a detection limit as low as 7.94 × 10-16 g mL-1. Furthermore, the reliable recoveries in real samples confirm the practicability of the proposed sensing platform, highlighting the enormous potential of intelligent nanomachines for analyzing the trace hazards in the environment and food.

Ultrasensitive Detection Strategy of Norovirus Based on a Dual Enhancement Strategy: CRISPR-Responsive Self-Assembled SNA and Isothermal Amplification

Spherical nucleic acids (SNAs) have been used to construct various nanobiosensors with gold nanoparticles (AuNPs) as nuclei. The SNAs play a critical role in biosensing due to their various physical and chemical properties, programmability, and specificity recognition ability. In this study, CRISPR-responsive self-assembled spherical nucleic acid (CRISPR-rsSNA) detection probes were constructed by conjugating fluorescein-labeled probes to the surface of AuNPs to improve the sensing performance. Also, the mechanism of ssDNA and the role of different fluorescent groups in the self-assembly process of CRISPR-rsSNA were explored. Then, CRISPR-rsSNA and reverse transcription-recombinase polymerase amplification (RT-RPA) were combined to develop an ultrasensitive fluorescence-detection strategy for norovirus. In the presence of the virus, the target RNA sequence of the virus was transformed and amplified by RT-RPA. The resulting dsDNA activated the trans-cleavage activity of CRISPR cas12a, resulting in disintegrating the outer nucleic acid structure of the CRISPR-rsSNA at a diffusible rate, which released reporter molecules. Norovirus was quantitated by fluorescence detection. This strategy facilitated the detection of the norovirus at the attomolar level. An RT-RPA kit for norovirus detected would be developed based on this method. The proposed method would be used for the detection of different viruses just by changing the target RNA and crRNA of the CRISPR cas12a system which provided a foundation for high-throughput detection of various substances.

Spherical nucleic acids-based nanoplatforms for tumor precision medicine and immunotherapy

Precise diagnosis and treatment of tumors currently still face considerable challenges due to the development of highly degreed heterogeneity in the dynamic evolution of tumors. With the rapid development of genomics, personalized diagnosis and treatment using specific genes may be a robust strategy to break through the bottleneck of traditional tumor treatment. Nevertheless, efficient in vivo gene delivery has been frequently hampered by the inherent defects of vectors and various biological barriers. Encouragingly, spherical nucleic acids (SNAs) with good modularity and programmability are excellent candidates capable of addressing traditional gene transfer-associated issues, which enables SNAs a precision nanoplatform with great potential for diverse biomedical applications. In this regard, there have been detailed reviews of SNA in drug delivery, gene regulation, and dermatology treatment. Still, to the best of our knowledge, there is no published systematic review summarizing the use of SNAs in oncology precision medicine and immunotherapy, which are considered new guidelines for oncology treatment. To this end, we summarized the notable advances in SNAs-based precision therapy and immunotherapy for tumors following a classification standard of different types of precise spatiotemporal control on active species by SNAs. Specifically, we focus on the structural diversity and programmability of SNAs. Finally, the challenges and possible solutions were discussed in the concluding remarks. This review will promote the rational design and development of SNAs for tumor-precise medicine and immunotherapy.