Enhanced Targeted Gene Transduction: AAV2 Vectors Conjugated to Multiple Aptamers via Reducible Disulfide Linkages

DNA response element-based smart drug delivery systems for precise drug release

Smart drug delivery systems (DDSs) that respond to, interact with, or are actuated by biological signals or pathological abnormalities (e.g., the tumor microenvironment) for controllable drug release are appealing therapeutic platforms for cancer treatment. Owing to their inherent self-assembled nature, nucleic acids have emerged as programmable materials for the development of multifunctional structures. In response to external environmental stimuli, DNA response elements can serve as switches to trigger conformational changes in DNA structures. Their stimulus-responsive properties make them promising candidates for constructing smart DDSs, and advancements in DNA response element-based DDSs in the field of biomedicine have been made. This review summarizes different types of DNA response elements, including DNA aptamers, DNAzymes, disulfide bond-modified DNA, pH-responsive DNA motifs, and photocleavable DNA building blocks, and highlights the advancements in DNA response element-based smart DDSs for precise drug release. Finally, future challenges and perspectives in this field are discussed.

Negative Thermal Expansion in ABC(MoO4)3 Compounds

Negative thermal expansion (NTE) compounds provide a solution for the mismatch of coefficients of thermal expansion in highly integrated device design. However, the current NTE compounds are rare, and how to effectively design new NTE compounds is still challenging. Here, a new concept is proposed to design NTE compounds, that is, to increase the flexibility of framework structure by expanding the space in framework structure compounds. Taking the parent compound NaZr2(PO4)3 as a case, a new NTE system AIBIICIII(MoO4)3 (A = Li, Na, K, and Rb; B = Mg and Mn; C = Sc, In, and Lu) is designed. In these compounds, the large volume of MoO4 tetrahedron is used to replace the small volume of PO4 tetrahedron in NaZr2(PO4)3 to enhance structural space and NTE performance. Simultaneously, a joint study of temperature-dependent X-ray diffraction, Raman spectroscopy, and the first principles calculation reveals that the NTE in AIBIICIII(MoO4)3 series compounds arise from the coupled oscillation of polyhedral. Large-radius ions are conducive to enhancing the space and softening the framework structure to achieve the enhancement of NTE. The current strategy for designing NTE compounds is expected to be adopted in other compounds to obtain more NTE compounds.

Colorimetric and photothermal dual-mode aptasensor with redox cycling amplification for the detection of ochratoxin A in corn samples

Ochratoxin A (OTA) detection is critical for public health safety. This study proposes a G-quadruplex-Hemin/iodide (G4-Hemin/I-)-mediated non-enzyme redox cycling amplification (RCA) system for dual-modal (colorimetric and photothermal thermometer) OTA analysis. The proposed aptasensor platform for point-of-care testing employs a common thermometer for quantitative signal readouts. The OTA aptamer folds into a G4 structure, which significantly enhances the catalytic activity in the presence of I- after RCA reaction. Moreover, a notable temperature enhancement causes color changes, providing an ultrasensitive and label-free platform for OTA detection. Further, the designed sensor was applied to OTA content determination in corn samples and achieved satisfactory results compared to a commercial enzyme-linked immunoassay kit. The proposed dual-mode aptasensor is simple, highly sensitive (1 pg/mL for colorimetric method, 0.8 pg/mL for photothermal method), selective, and suitable for low-cost instrument-free bioanalysis in low-resource settings.

Tools and techniques for the discovery of therapeutic aptamers: recent advances

INTRODUCTION

The pursuit of novel therapeutic agents for serious diseases such as cancer has been a global endeavor. Aptamers characteristic of high affinity, programmability, low immunogenicity, and rapid permeability hold great promise for the treatment of diseases. Yet obtaining the approval for therapeutic aptamers remains challenging. Consequently, researchers are increasingly devoted to exploring innovative strategies and technologies to advance the development of these therapeutic aptamers.

AREAS COVERED

The authors provide a comprehensive summary of the recent progress of the SELEX (Systematic Evolution of Ligands by EXponential enrichment) technique, and how the integration of modern tools has facilitated the identification of therapeutic aptamers. Additionally, the engineering of aptamers to enhance their functional attributes, such as inhibiting and targeting, is discussed, demonstrating the potential to broaden their scope of utility.

EXPERT OPINION

The grand potential of aptamers and the insufficient development of relevant drugs have spurred countless efforts for stimulating their discovery and application in the therapeutic field. While SELEX techniques have undergone significant developments with the aid of advanced analysis instruments and ingeniously updated aptameric engineering strategies, several challenges still impede their clinical translation. A key challenge lies in the insufficient understanding of binding conformation and susceptibility to degradation under physiological conditions. Despite the hurdles, our opinion is optimistic. With continued progress in overcoming these obstacles, the widespread utilization of aptamers for clinical therapy is envisioned to become a reality soon.

Target-activated multivalent sensing platform for improving the sensitivity and selectivity of Hg2+ detection

Sensitivity and selectivity are critical parameters to evaluate the performance of sensors. For trace detection, it remains a challenge to design a new sensor that achieves high sensitivity and selectivity simultaneously. Here, we present a target-activated dual Mg²⁺-dependent DNAzyme (MNAzyme) that served as a simple sensing model to explore the multivalency in improving the analytical sensitivity and selectivity for target detection. Mercury ion (Hg²⁺), a notorious toxic metal ion, was selected as a model target. In the presence of Hg²⁺, the thymine-rich regions of the hairpin probe and primer could hybridize to form a stable duplex via the thymine-Hg²⁺-thymine structure. Then, an intact enzyme sequence was exposed and two separate enzyme fragments were close to each other, generating a dual MNAzyme. Benefiting from the localized high-concentration of the enzyme strand, the dual MNAzyme showed a remarkable improvement in binding stability. The catalytic rate constant of the dual MNAzyme was theoretically 1.60 times higher than that of the monomeric counterpart, and the sensitivity and selectivity had 4.50 and 1.44-fold enhancement, respectively. When the dual MNAzyme was used for sensor applications, the limit of detection was determined to be 0.04 and 0.2 nM via UV-vis spectrophotometer and naked eye, respectively. Meanwhile, the method offered desirable selectivity toward Hg²⁺ against other metal ions. With the advantages of simple operation, high sensitivity, and desirable selectivity, the developed multivalent sensing platform could be easily expanded in the future for the on-site detection of other low-abundance analytes.

Heteromultivalent scaffolds fabricated by biomimetic co-assembly of DNA-RNA building blocks for the multi-analysis of miRNAs

Heteromultivalent scaffolds with different repeated monomers have great potential in biomedicine, but convenient construction strategies for integrating various functional modules to achieve multiple biological functions are still lacking. Here, taking advantage of the heteromultivalent effect of dendritic nucleic acids and the specific biochemical properties of microRNAs (miRNAs), we assembled novel heteromultivalent nucleic acid scaffolds by biomimetic co-assembly of DNA-RNA building blocks. In our approach, two miRNAs were used to initiate and maintain dendritic structures in an interdependent manner; so, the heteromultivalent nanostructure can only form in the presence of both miRNAs. The proposed nanostructure can be used for one-step analysis of two miRNAs in an AND logic format. Taking miR-18b-5p and miR-342-3p which are associated with Alzheimer's disease as an example, a FRET sensing system was fabricated for the simultaneous analysis of two miRNAs within one hour at picomolar concentration. Further studies show that the designed device may have the potential to distinguish between AD patients and the healthy population by analysis of two miRNAs in CSF (cerebrospinal fluid) samples, suggesting its possible applicability in clinics.

Recent progress of aptamer‒drug conjugates in cancer therapy

Aptamers are single-stranded DNA or RNA sequences that can specifically bind with the target protein or molecule via specific secondary structures. Compared to antibody-drug conjugates (ADC), aptamer‒drug conjugate (ApDC) is also an efficient, targeted drug for cancer therapy with a smaller size, higher chemical stability, lower immunogenicity, faster tissue penetration, and facile engineering. Despite all these advantages, several key factors have delayed the clinical translation of ApDC, such as in vivo off-target effects and potential safety issues. In this review, we highlight the most recent progress in the development of ApDC and discuss solutions to the problems noted above.

Targeting treatment of bladder cancer using PTK7 aptamer-gemcitabine conjugate

BACKGROUND

Gemcitabine (GEM) is one of the first-line chemotherapies for bladder cancer (BC), but the GEMs cannot recognize cancer cells and have a low long-term response rate and high recurrence rate with side effects during the treatment of BC. Targeted transport of GEMs to mediate cytotoxicity to tumor and avoid the systemic side effects remains a challenge in the treatment of BC.

METHODS

Based on a firstly confirmed biomarker in BC-protein tyrosine kinase 7 (PTK7), which is overexpressed on the cell membrane surface in BC cells, a novel targeting system protein tyrosine kinase 7 aptamer-Gemcitabine conjugate (PTK7-GEMs) was designed and synthesized using a specific PTK7 aptamer and GEM through auto-synthesis method to deliver GEM against BC. In addition, the antitumor effects and safety evaluation of PTK7-GEMs was assessed with a series of in vitro and in vivo assays.

RESULTS

PTK7-GEMs can specifically bind and enter to BC cells dependent on the expression levels of PTK7 and via the macropinocytosis pathway, which induced cytotoxicity after GEM cleavage from PTK7-GEMs respond to the intracellular phosphatase. Moreover, PTK7-GEMs showed stronger anti-tumor efficacy and excellent biosafety in three types of tumor xenograft mice models.

CONCLUSION

These results demonstrated that PTK7-GEMs is a successful targeted aptamer-drug conjugates strategy (APDCs) to treat BC, which will provide new directions for the precision treatment of BC in the field of biomarker-oriented tumor targeted therapy.

Construction of Fast-Walking Tetrahedral DNA Walker with Four Arms for Sensitive Detection and Intracellular Imaging of Apurinic/Apyrimidinic Endonuclease 1

Herein, a novel tetrahedral DNA walker with four arms was engineered to travel efficiently on the 3D-tracks via catalyzed hairpin assembly autonomously, realizing the sensitive detection and activity assessment as well as intracellular imaging of apurinic/apyrimidinic endonuclease 1 (APE1). In contrast to traditional DNA walkers, the tetrahedral DNA walker with the rigid 3D framework structure and nonplanar multi-sites walking arms endowed with high collision efficiency, showing a fast walking rate and high nuclease resistance. Impressively, the initial rate of the tetrahedral DNA walker with four arms was 4.54 times faster than that of the free bipedal DNA walker and produced a significant fluorescence recovery in about 40 min, achieving a sensitive detection of APE1 with a low detection limit of 5.54× 10^-6 U/μL as well as ultrasensitive intracellular APE1 fluorescence activation imaging. This strategy provides a novel DNA walker for accurate identification of low-abundance cancer biomarker and potential medical diagnosis.

Multibranched Linear DNA-Controlled Assembly of Silver Nanoclusters and Their Applications in Aptamer-Based Cell Recognition

DNA-templated silver nanoclusters (DNA-AgNCs) are promising fluorescent materials and have been used in cancer diagnosis. Although many different DNA-AgNC applications have been realized, most of them rely on individual DNA-AgNCs or assembled DNA-AgNCs with limited recognition abilities, resulting in low detection sensitivity or off-target effects, in turn, hindering the performance of DNA-AgNCs in cancer cell recognition. As a solution, we assembled DNA-AgNCs by a multibranched linear (MBL) DNA structure formed through a trigger-initiated hybridization chain reaction (HCR) regarding the natural compatibility of DNA-AgNCs with DNA programmability and the advantages of DNA assembly in incorporating repetitive and functional moieties into one structure. By the specific modification of the trigger, MBL-AgNCs tethered with the targeting aptamer and partially hybridized duplex, which works as a component of DNA logic platform relying on the combination of cascade strand displacement reaction and specific recognition ability of aptamers, were obtained, respectively. DNA-AgNCs assembled by the aptamer-tethered MBL structure exhibited about 20-fold enhanced detection sensitivity in recognizing cancer cells compared to individual aptamer-tethered DNA-AgNCs. DNA-AgNCs assembled by the duplex-attached MBL exhibited logic performance in analyzing dual cell surface receptors with the assistance of "AND" logic platform, thus identifying cancer cells with high sensitivity and resolution. The facile conjugation of the MBL structure with different functional DNA structures makes it an ideal platform to assemble DNA-AgNCs used for aptamer-based cell recognition, thus broadening the potential applications of DNA-AgNCs.

Multivalent Aptamer Approach: Designs, Strategies, and Applications

Aptamers are short and single-stranded DNA or RNA molecules with highly programmable structures that give them the ability to interact specifically with a large variety of targets, including proteins, cells, and small molecules. Multivalent aptamers refer to molecular constructs that combine two or more identical or different types of aptamers. Multivalency increases the avidity of aptamers, a particularly advantageous feature that allows for significantly increased binding affinities in comparison with aptamer monomers. Another advantage of multivalency is increased aptamer stabilities that confer improved performances under physiological conditions for various applications in clinical settings. The current study aims to review the most recent developments in multivalent aptamer research. The review will first discuss structures of multivalent aptamers. This is followed by detailed discussions on design strategies of multivalent aptamer approaches. Finally, recent developments of the multivalent aptamer approach in biosensing and biomedical applications are highlighted.

Highly Effective Crosslinker for Redox-Sensitive Gene Carriers

Polyethyleneimine (PEI) has been extensively used as a common gene carrier due to its high gene transfection efficiency. PEI1.8k shows significantly lower cytotoxicity than its high molecular weight counterparts. However, it also has the problem of low gene transfection efficiency. To address the dilemma, a highly effective crosslinker (DTME) was synthesized to react with PEI1.8k to obtain CS-PEI1.8k. The reaction showed several advantages, such as a fast process in room temperature within nine hours with the product which can directly complex with DNA after removing the solvent. The ability of CS-PEI1.8k to agglomerate with DNA was proven by particle size, zeta potential, and gel retardation assays. The cytotoxic in vitro transfection ability and cell internalization capacity of CS-PEI1.8k were tested to verify the transfection capacity of CS-PEI1.8k. Moreover, we also studied the mechanism of the relatively high level of gene transfection by this binary complex compared with PEI25k.

Amplifiable ratiometric fluorescence biosensing of nanosilver multiclusters populated in three-way-junction DNA branches

To explore the fluorescence bio-responsiveness of emissive silver nanoclusters (AgNCs) populated in DNA-branched scaffolds is intriguing yet challenging. In response to a desired targeting model (T*) as a vehicle, herein a customized three-way-junction DNA construct (TWJDC) is assembled via competitive hybridizing cascade among three stem-loop hairpins with specific base sequences, where the repeated recycling of T* enables the exponentially amplifiable output of rigid TWJDC. As designed, these stable hybridization products are highly T*-stimulated responsive and constructing-directional. In the three branched-arms, the unpaired sticky ends provide isotropic binding sites for a signaling hairpin encoded with two C-rich templates of green- and red-AgNCs clustering. The identical ligation of signal probe with three arms of TWJDC liberates its locked stem, enabling the separate growth of red-clusters in three branches. As demonstrated, three clusters of red-AgNCs possess advantageous self-enhancing fluorescent performance relative to single or two cluster(s), good biocompatibility and low cytotoxicity. Utilizing the bicolor AgNCs as dual-emitters with reversely changed emission intensity, we developed an innovative ratiometric strategy displaying sensitively linear dose-dependence on variable T* down to 1.9 pM, which can afford a promising platform for biosensing, bioanalysis, cell imaging, or even clinical theranostics.

Aptamer-assisted tumor localization of bacteria for enhanced biotherapy

Despite bacterial-mediated biotherapies have been widely explored for treating different types of cancer, their implementation has been restricted by low treatment efficacy, due largely to the absence of tumor-specific accumulation following administration. Here, the conjugation of aptamers to bacterial surface is described by a simple and cytocompatible amidation procedure, which can significantly promote the localization of bacteria in tumor site after systemic administration. The surface density of aptamers can be easily adjusted by varying feed ratio and the conjugation is able to increase the stability of anchored aptamers. Optimal bacteria conjugated with an average of 2.8 × 105 aptamers per cell present the highest specificity to tumor cells in vitro, separately generating near 2- and 4-times higher accumulation in tumor tissue at 12 and 60 hours compared to unmodified bacteria. In both 4T1 and H22 tumor-bearing mouse models, aptamer-conjugated attenuated Salmonella show enhanced antitumor efficacy, along with highly activated immune responses inside the tumor. This work demonstrates how bacterial behaviors can be tuned by surface conjugation and supports the potential of aptamer-conjugated bacteria for both targeted intratumoral localization and enhanced tumor biotherapy.

Enhancing anti-PD-1 Immunotherapy by Nanomicelles Self-Assembled from Multivalent Aptamer Drug Conjugates

A tumor-targeting enhanced chemotherapy, enabled by aptamer-drug conjugate nanomicelles, is reported that boosts antitumor immune responses. Multivalent aptamer drug conjugate (ApMDC), an amphiphilic telodendrimer consisting of a hydrophilic aptamer and a hydrophobic monodendron anchored with four anticancer drugs by acid-labile linkers, was designed and synthesized. By co-self-assembly with an ApMDC analogue, in which aptamer is replaced with polyethylene glycol, the surface aptamer density of these nanomicelles can be screened to reach an optimal complementation between blood circulation and tumor-targeting ability. Optimized nanomicelles can enhance immunogenic cell death of tumor cells, which strikingly augments the tumor-specific immune responses of the checkpoint blockade in immunocompetent tumor-bearing mice. ApMDC nanomicelles represent a robust platform for structure-function optimization of drug conjugates and nanomedicines.

Dynamic Continuum of Nanoscale Peptide Assemblies Facilitates Endocytosis and Endosomal Escape

Alkaline phosphatase (ALP) enables intracellular targeting by peptide assemblies, but how the ALP substrates enter cells remains elusive. Here we show that nanoscale phosphopeptide assemblies cluster ALP to enable caveolae-mediated endocytosis (CME) and endosomal escape. Specifically, fluorescent phosphopeptides undergo enzyme-catalyzed self-assembly to form nanofibers. Live cell imaging unveils that phosphopeptides nanoparticles, coincubated with HEK293 cells overexpressing red fluorescent protein-tagged tissue-nonspecific ALP (TNAP-RFP), cluster TNAP-RFP in lipid rafts to enable CME. Further dephosphorylation of the phosphopeptides produces peptidic nanofibers for endosomal escape. Inhibiting TNAP, cleaving the membrane anchored TNAP, or disrupting lipid rafts abolishes the endocytosis. Decreasing the transformation to nanofibers prevents the endosomal escape. As the first study establishing a dynamic continuum of nanoscale assemblies for cellular uptake, this work illustrates an effective design for enzyme-responsive supramolecular therapeutics and provides mechanism insights for understanding the dynamics of cellular uptake of proteins or exogenous peptide aggregates.

Oligonucleotide-Based Therapies for Renal Diseases

The global burden of chronic kidney disease (CKD) is increasing every year and represents a great cost for public healthcare systems, as the majority of these diseases are progressive. Therefore, there is an urgent need to develop new therapies. Oligonucleotide-based drugs are emerging as novel and promising alternatives to traditional drugs. Their expansion corresponds with new knowledge regarding the molecular basis underlying CKD, and they are already showing encouraging preclinical results, with two candidates being evaluated in clinical trials. However, despite recent technological advances, efficient kidney delivery remains challenging, and the presence of off-targets and side-effects precludes development and translation to the clinic. In this review, we provide an overview of the various oligotherapeutic strategies used preclinically, emphasizing the most recent findings in the field, together with the different strategies employed to achieve proper kidney delivery. The use of different nanotechnological platforms, including nanocarriers, nanoparticles, viral vectors or aptamers, and their potential for the development of more specific and effective treatments is also outlined.

Targeted Delivery of DNA Framework-Encapsulated Native Therapeutic Protein into Cancer Cells

A protein-based therapy is significantly challenged by the successful delivery of native proteins into the targeted cancer cells. We address this challenge here using an all-sealed divalent aptamer tetrahedral DNA framework (asdTDF) delivery platform, in which the protein drug is encapsulated inside the cavity of the framework stoichiometrically via a reversible chemical bond. The ligase-assisted seal of the nicks results in highly enhanced TDF stability of the against nuclease digestion to effectively protect the therapeutic protein from degradation. In addition, the divalent aptamer sequences incorporated into the framework favor it with a target-specific and efficient delivery capability. Importantly, upon being readily delivered into the targeted cancer cells, endogenous glutathione can trigger the release of the native therapeutic protein from the TDF in a traceless fashion by cleaving the reversible chemical bond, thereby leading to effective apoptosis of the specific cancer cells.

Structural requirement of G-quadruplex/aptamer-combined DNA macromolecule serving as efficient drug carrier for cancer-targeted drug delivery

Photodynamic therapy (PDT) as a clinical cancer treatment method has been used to treat carcinomas in different organs, and G-quadruplex-based DNA nanocompartments serving as the carriers of cationic porphyrin photosensitizers, especially combined with cell-targeting aptamers, is considered to offer new opportunities for future cancer treatment. However, the structural features of G-quadruplex/aptamer complexes suitable for the capsulation of photosensitizers and target cell recognition is unexplored so far. In this study, unimolecular (UM), bimolecular (BM) and tetramolecular (TM) G-quadruplex structures were used as the drug loading compartments and grafted onto tumor cell-targeting aptamer Sgc8, constructing several targeting drug delivery vehicles (T-GMVs). Besides the binding affinity of resulting DNA architectures for target cells and cell recognition specificity were explored in a comparative fashion, the drug loading capability and cancer therapy efficacy were evaluated using TMPyP4 as the model porphyrin-based drug. The experimental results show that only TM G-quadruplex structure is suitable to combine with Sgc8 for the development of drug delivery vehicle and the as-prepared T-GMV- TMPyP4 complexes display the desirable cancer therapy efficacy, holding the potential application in the future cancer therapy. More importantly, T-GMV- TMPyP4 is expected to lay the scientific groundwork for the successful development of G-quadruplex-based photosensitizer drug delivery carriers for the targeted cancer therapy.

Materials promoting viral gene delivery

Therapeutic viral gene delivery is an emerging technology which aims to correct genetic mutations by introducing new genetic information to cells either to correct a faulty gene or to initiate cell death in oncolytic treatments. In recent years, significant scientific progress has led to several clinical trials resulting in the approval of gene therapies for human treatment. However, successful therapies remain limited due to a number of challenges such as inefficient cell uptake, low transduction efficiency (TE), limited tropism, liver toxicity and immune response. To adress these issues and increase the number of available therapies, additives from a broad range of materials like polymers, peptides, lipids, nanoparticles, and small molecules have been applied so far. The scope of this review is to highlight these selected delivery systems from a materials perspective.

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.

Tissue-Specific Delivery of Oligonucleotides

From the initial discovery of short-interfering RNA (siRNA) and antisense oligonucleotides for specific gene knockdown at the posttranscriptional level to the current CRISPR-Cas9 system offering gene editing at the genomic level, oligonucleotides, in addition to their biological functions in storing and conveying genetic information, provide the most prominent solutions to targeted gene therapies. Nonetheless, looking into the future of curing cancer and acute diseases, researchers are only cautiously optimistic as the cellular delivery of these polyanionic biomacromolecules is still the biggest hurdle for their therapeutic realization. To overcome the delivery obstacle, oligonucleotides have been encapsulated within or conjugated with delivery vehicles for enhanced membrane penetration, improved payload, and tissue-specific delivery. Such delivery systems include but not limited to virus-based vehicles, gold-nanoparticle vehicles, formulated liposomes, and synthetic polymers. In this chapter, delivery challenges imposed by biological barriers are briefly discussed; followed by recent advances in tissue-specific oligonucleotide delivery utilizing both viral and nonviral delivery vectors, discussing their advantages, and how judicious design and formulation could improve and expand their potential as delivery vehicles.

Bead-String-Shaped DNA Nanowires with Intrinsic Structural Advantages and Their Potential for Biomedical Applications

Due to high programmability and good biocompatibility, DNA has been recognized as a powerful building block for engineering of sophisticated nanostructures for different purposes. Herein, we present the first example of a bead-string-shaped DNA nanowire (BS-nanow) with long-range structural order for in vivo bioimaging and targeted drug delivery. BS-nanow is assembled from DNA tetrahedron units with precise nanometer-scale spatial control, capable of accommodating chemotherapeutic agents with high payload capacity (1204 binding sites) as well as possessing a 60-fold enhanced binding affinity for target cells. Confocal fluorescence imaging and in vivo experiments on CEM subcutaneous tumor-bearing mice show that specific bioimaging of living cells and even systemic delivery of drugs into internal tumor organs and tissues were accomplished, thereby achieving an efficient inhibition of tumor growth in the xenograft model without systemic toxicity. BS-nanow's show potential in vivo applications in accurate diagnosis and targeted therapy for human cancer.

Programming DNA Nanoassembly for Enhanced Photodynamic Therapy

Photodynamic therapy (PDT) has extraordinary promise for the treatment of many cancers. However, its clinical progress is impaired by the intrinsic hypoxic tumor microenvironment that limits PDT efficacy and the safety concern associated with biological specificity of photosensitizers or vehicles. Now it is demonstrated that rationally designed DNA nanosponges can load and delivery photosensitizer effectively, target tumor precisely, and relieve hypoxia-associated resistance remarkably to enhance the efficacy of PDT. Specifically, the approach exhibits a facile assembly process, provides programmable and versatile nanocarriers, and enables robust in vitro and in vivo anti-cancer efficacy with excellent biosafety. These findings represent a practical and safe approach by designer DNA nanoassemblies to combat cancer effectively and suggest a powerful strategy for broad biomedical application of PDT.

Tumor Targeting Strategies of Smart Fluorescent Nanoparticles and Their Applications in Cancer Diagnosis and Treatment

Advantages such as strong signal strength, resistance to photobleaching, tunable fluorescence emissions, high sensitivity, and biocompatibility are the driving forces for the application of fluorescent nanoparticles (FNPs) in cancer diagnosis and therapy. In addition, the large surface area and easy modification of FNPs provide a platform for the design of multifunctional nanoparticles (MFNPs) for tumor targeting, diagnosis, and treatment. In order to obtain better targeting and therapeutic effects, it is necessary to understand the properties and targeting mechanisms of FNPs, which are the foundation and play a key role in the targeting design of nanoparticles (NPs). Widely accepted and applied targeting mechanisms such as enhanced permeability and retention (EPR) effect, active targeting, and tumor microenvironment (TME) targeting are summarized here. Additionally, a freshly discovered targeting mechanism is introduced, termed cell membrane permeability targeting (CMPT), which improves the tumor-targeting rate from less than 5% of the EPR effect to more than 50%. A new design strategy is also summarized, which is promising for future clinical targeting NPs/nanomedicines design. The targeting mechanism and design strategy will inspire new insights and thoughts on targeting design and will speed up precision medicine and contribute to cancer therapy and early diagnosis.

Aptamer-based targeted therapy

Precision medicine holds great promise to harness genetic and epigenetic cues for targeted treatment of a variety of diseases, ranging from many types of cancers, neurodegenerative diseases, to cardiovascular diseases. The proteomic profiles resulting from the unique genetic and epigenetic signatures represent a class of relatively well accessible molecular targets for both interrogation (e.g., diagnosis, prognosis) and intervention (e.g., targeted therapy) of these diseases. Aptamers are promising for such applications by specific binding with cognate disease biomarkers. Nucleic acid aptamers are a class of DNA or RNA with unique three-dimensional conformations that allow them to specifically bind with target molecules. Aptamers can be relatively easily screened, reproducibly manufactured, programmably designed, and chemically modified for various biomedical applications, including targeted therapy. Aptamers can be chemically modified to resist enzymatic degradation or optimize their pharmacological behaviors, which ensured their chemical integrity and bioavailability under physiological conditions. In this review, we will focus on recent progress and discuss the challenges and opportunities in the research areas of aptamer-based targeted therapy in the forms of aptamer therapeutics and aptamer-drug conjugates (ApDCs).

PAMAM-Based Dendrimers with Different Alkyl Chains Self-Assemble on Silica Surfaces: Controllable Layer Structure and Molecular Aggregation

Amphiphilic poly(amidoamine) (PAMAM) dendrimers are a well-known dendritic family due to their remarkable ability to self-assemble on solid surface. However, the relationship between molecular conformation (or adsorption kinetics) of a self-assembled layer and molecular amphiphilicity of such kind of dendrimer is still lacking, which limits the development of modulating self-assembling structures and surface functionality. With this in mind, we synthesized a series of amphiphilic PAMAM-based dendrimers, denoted as G₁C _n, with different alkyl chains ( n = 8, 12, and 16), and investigated the molecular aggregation on silica surfaces by means of quartz crystal microbalance with dissipation, atomic force microscopy, and contact angle. After rinsing, remaining adsorption amounts of G₁C₁₂ were higher than those of G₁C₈ at high concentrations, suggesting that G₁C₁₂ adlayers were more stable due to the stronger intermolecular hydrophobic interactions, whereas it preferred to adopt the intramolecular hydrophobic interactions for G₁C₁₆, with low adsorption amounts and unstable adlayers. Bilayer-like structures were inferred in G₁C₈ and G₁C₁₂ adlayers with loose conformation, whereas monolayer structures were likely to exist in the sparse adsorption film of G₁C₁₆. Our results provided more detailed understanding of the effect of molecular structure on the self-assembled structures of amphiphilic dendrimers on solid surfaces, shedding light on the controlled microstructure and wettability of functional surface by modulating the length of hydrophobic chains of dendrimers and a potential application of dendrimer-substrate combinations.