DNA-Templated Silver Nanocluster/Porphyrin/MnO2 Platform for Label-Free Intracellular Zn2+ Imaging and Fluorescence-/Magnetic Resonance Imaging-Guided Photodynamic Therapy

Two-dimensional nanomaterials induced nano-bio interfacial effects and biomedical applications in cancer treatment

Two-dimensional nanomaterials (2D NMs), characterized by a large number of atoms or molecules arranged in one dimension (typically thickness) while having tiny dimensions in the other two dimensions, have emerged as a pivotal class of materials with unique properties. Their flat and sheet-like structure imparts distinctive physical, chemical, and electronic attributes, which offers several advantages in biomedical applications, including enhanced surface area for efficient drug loading, surface-exposed atoms allowing precise chemical modifications, and the ability to form hierarchical multilayer structures for synergistic functionality. Exploring their nano-bio interfacial interactions with biological components holds significant importance in comprehensively and systematically guiding safe applications. However, the current lack of in-depth analysis and comprehensive understanding of interfacial effects on cancer treatment motivates our ongoing efforts in this field. This study provides a comprehensive survey of recent advances in utilizing 2D NMs for cancer treatment. It offers insights into the structural characteristics, synthesis methods, and surface modifications of diverse 2D NMs. The investigation further delves into the formation of nano-bio interfaces during their in vivo utilization. Notably, the study discusses a wide array of biomedical applications in cancer treatment. With their potential to revolutionize therapeutic strategies and outcomes, 2D NMs are poised at the forefront of cancer treatment, holding the promise of transformative advancements.

Preparation of chitosan/SiO2 coated silver nanoclusters and its application in enhanced fluorescence detection of berberine hydrochloride

Although the synthesis and applications of the metal nanoclusters and silica coated metal noclusters were widely explored, however, the fluorescence sensing application of silica coated metal nanoclusters are still challenges. In this work, the composite nanoparticles (PEI-Ag NCs/CSNPs) were synthesized by coating polyethyleneimine capped silver nanoclusters (PEI-Ag NCs) with chitosan/silica through a reverse microemulsion method, and then used for fluorescence enhancement detection of berberine hydrochloride (BRH). UV-vis absorption spectra, fluorescence spectra, IR spectra, transmission electron microscope (TEM) and X-ray Photoelectron Spectroscopy (XPS) technique were used to reveal the possible binding relationship between PEI-AgNCs and chitosan/silica and fluorescence sensing mechanism of PEI-Ag NCs/CSNPs to BRH. The results showed that PEI-Ag NCs/CSNPs possess better sensing ability as compared to the free PEI- Ag NCs and can be successfully applied to evaluate the BRH content in actual medicine.

Redox double-switch cancer theranostics through Pt(IV) functionalised manganese dioxide nanostructures

Manganese dioxide (MnO₂)-based nanostructures have emerged as promising tumour microenvironment (TME) responsive platforms. Herein, we used a one-pot reaction to prepare MnO₂ nanostructures with Pt(IV) prodrugs as redox- (and thus TME-) responsive theranostics for cancer therapy, in which the Pt(IV) complexes act as prodrugs of cisplatin (Pt(II)), a clinical chemotherapeutic drug. The cytotoxicity of these MnO₂-Pt(IV) probes was evaluated in two and three dimensional (2D and 3D) A549 cell models and found to be as effective as active drug cisplatin in 3D models. Moreover, MnO₂-Pt(IV) nanoparticles exhibited strong off/ON magnetic resonance (MR) contrast in response to reducing agents, with the longitudinal relaxivity (r₁) increasing 136-fold upon treatment with ascorbic acid. This off/ON MR switch was also observed in (2D and 3D) cells in vitro. In vivo MRI experiments revealed that the nanostructures induce a strong and long-lasting T₁ signal enhancement upon intratumoral injection in A549 tumour-bearing mice. These results show the potential of MnO₂-Pt(IV) NPs as redox responsive MR theranostics for cancer therapy.

Biomedical applications of MnO2 nanomaterials as nanozyme-based theranostics

Manganese dioxide (MnO₂) nanoenzymes/nanozymes (MnO₂-NEs) are 1-100 nm nanomaterials that mimic catalytic, oxidative, peroxidase, and superoxide dismutase activities. The oxidative-like activity of MnO₂-NEs makes them suitable for developing effective and low-cost colorimetric detection assays of biomolecules. Interestingly, MnO₂-NEs also demonstrate scavenging properties against reactive oxygen species (ROS) in various pathological conditions. In addition, due to the decomposition of MnO₂-NEs in the tumor microenvironment (TME) and the production of Mn²⁺, they can act as a contrast agent for improving clinical imaging diagnostics. MnO₂-NEs also can use as an in situ oxygen production system in TME, thereby overcoming hypoxic conditions and their consequences in the progression of cancer. Furthermore, MnO₂-NEs as a shell and coating make the nanosystems smart and, therefore, in combination with other nanomaterials, the MnO₂-NEs can be used as an intelligent nanocarrier for delivering drugs, photosensitizers, and sonosensitizers in vivo. Moreover, these capabilities make MnO₂-NEs a promising candidate for the detection and treatment of different human diseases such as cancer, metabolic, infectious, and inflammatory pathological conditions. MnO₂-NEs also have ROS-scavenging and anti-bacterial properties against Gram-positive and Gram-negative bacterial strains, which make them suitable for wound healing applications. Given the importance of nanomaterials and their potential applications in biomedicine, this review aimed to discuss the biochemical properties and the theranostic roles of MnO₂-NEs and recent advances in their use in colorimetric detection assays of biomolecules, diagnostic imaging, drug delivery, and combinatorial therapy applications. Finally, the challenges of MnO₂-NEs applications in biomedicine will be discussed.

Bioactive inorganic nanomaterials for cancer theranostics

Bioactive materials are a special class of biomaterials that can react in vivo to induce a biological response or regulate biological functions, thus achieving a better curative effect than traditional inert biomaterials. For cancer theranostics, compared with organic or polymer nanomaterials, inorganic nanomaterials possess unique physical and chemical properties, have stronger mechanical stability on the basis of maintaining certain bioactivity, and are easy to be compounded with various carriers (polymer carriers, biological carriers, etc.), so as to achieve specific antitumor efficacy. After entering the nanoscale, due to the nano-size effect, high specific surface area and special nanostructures, inorganic nanomaterials exhibit unique biological effects, which significantly influence the interaction with biological organisms. Therefore, the research and applications of bioactive inorganic nanomaterials in cancer theranostics have attracted wide attention. In this review, we mainly summarize the recent progress of bioactive inorganic nanomaterials in cancer theranostics, and also introduce the definition, synthesis and modification strategies of bioactive inorganic nanomaterials. Thereafter, the applications of bioactive inorganic nanomaterials in tumor imaging and antitumor therapy, including tumor microenvironment (TME) regulation, catalytic therapy, gas therapy, regulatory cell death and immunotherapy, are discussed. Finally, the biosafety and challenges of bioactive inorganic nanomaterials are also mentioned, and their future development opportunities are prospected. This review highlights the bioapplication of bioactive inorganic nanomaterials.

A novel ratiometric fluorescence probe for the detection of copper (II) and silver(I) based on assembling dye-doped silica core-shell nanoparticles with gold nanoclusters

A creatively designed and constructed a multifunctional ratiometric fluorescence probe is reported by assembling glutathione (GSH)-protected gold nanoclusters (AuNCs) with fluorescein-doped mesoporous silica nanoparticle (FS) for the detection of Cu²⁺ and Ag⁺ ions, which could eliminate most interferences by self-calibration. Under the excitation at 450 nm, the fluorescence connected with AuNCs can rapidly respond by quenching or enhancement, respectively, for Cu²⁺ and Ag⁺ ions, while the fluorescein isothiocyante (FITC) fluorescence served as reference with negligible change. The fluorescence intensity ratio showed good linear relationships with Cu²⁺ and Ag⁺ concentrations in the range 0.5-10 μM and 0.1-8 μM, respectively. The detection limits were as low as 140 nM and 60 nM for Cu²⁺ and Ag⁺ ions, respectively. The color change induced by fluorescent intensity ratio variation could also be employed for visual discrimination. The AuNC-embedded FS (FS-Au) nanoprobe was successfully used for Cu²⁺ and Ag⁺ ion determination in drinking water and intracellular Cu²⁺ imaging, which exhibits promising prospects in cost-effective and rapid determination of both Cu²⁺ and Ag⁺ with good sensitivity and selectivity.

Recent advances in 2D material-based phototherapy

Phototherapy, which generally refers to photothermal therapy (PTT) and photodynamic therapy (PDT), has received significant attention over the past few years since it is non-invasive, has effective selectivity, and has few side effects. As a result, it has become a promising alternative to traditional clinical treatments. At present, two-dimensional materials (2D materials) have proven to be at the forefront of the development of advanced nanomaterials due to their ultrathin structures and fascinating optical properties. As a result, much work has been put into developing phototherapy platforms based on 2D materials. This review summarizes the current developments in 2D materials beyond graphene for phototherapy, focusing on the novel approaches of PTT and PDT. New methods are being developed to go above and beyond conventional treatment to fully use the potential of 2D materials. Additionally, the efficacy of cutting-edge phototherapy is assessed, and the existing difficulties and future prospects of 2D materials for phototherapy are covered.

Hypoxia-responsive nanomaterials for tumor imaging and therapy

Hypoxia is an important component of tumor microenvironment and plays a pivotal role in cancer progression. With the distinctive physiochemical properties and biological effects, various nanoparticles targeting hypoxia had raised great interest in cancer imaging, drug delivery, and gene therapy during the last decade. In the current review, we provided a comprehensive view on the latest progress of novel stimuli-responsive nanomaterials targeting hypoxia-tumor microenvironment (TME), and their applications in cancer diagnosis and therapy. Future prospect and challenges of nanomaterials are also discussed.

Intracellular miRNA Imaging Based on a Self-Powered and Self-Feedback Entropy-Driven Catalyst-DNAzyme Circuit

DNAzyme-based signal amplification circuits promote the advances in low-abundant miRNA imaging in living cells. However, due to the insufficient cofactor in living cells and unsustainable target utilization, self-powered and self-feedback DNAzyme amplification circuits have rarely been achieved. Here, a MnO₂ nanosheet-mediated self-powered and self-feedback entropy-driven catalyst (EDC)-DNAzyme nanoprobe (MnPFEDz) was demonstrated for sensitive imaging of intracellular microRNA (miRNA). In this strategy, MnPFEDz was formed by adsorbing EDC modules and substrate probes on MnO₂ nanosheets. The MnO₂ nanosheets acted not only as glutathione (GSH)-responsive nanocarriers for efficient delivery of DNA probes but also as a DNAzyme cofactor supplier to power the DNAzyme biocatalysis and promote signal transduction in a feedback way. When entering the cells, GSH could decompose MnO₂ nanosheets to generate numerous Mn²⁺ ion cofactors, leading to the release of DNA probes. Subsequently, the target miRNA initiated EDC cycles to generate amplified fluorescence signals and exposed the complete DNAzyme. Meanwhile, each of the exposed DNAzyme then cleaved the substrate probes with the help of Mn²⁺ ion cofactors and released a new trigger analogue for the next round of EDC cycles, initiating additional fluorescence signals in a feedback way. As a multiple signal amplification strategy, the MnPFEDz nanoprobe facilitated the effective detection of intracellular molecules with enhanced sensitivity and provided a versatile strategy for the construction of self-powered and self-feedback DNA circuits in living cells.

Manganese-based hollow nanoplatforms for MR imaging-guided cancer therapies

Theranostic nanoplatforms integrating diagnostic and therapeutic functions have received considerable attention in the past decade. Among them, hollow manganese (Mn)-based nanoplatforms are superior since they combine the advantages of hollow structures and the intrinsic theranostic features of Mn²⁺. Specifically, the hollow cavity can encapsulate a variety of small-molecule drugs, such as chemotherapeutic agents, photosensitizers and photothermal agents, for chemotherapy, photodynamic therapy (PDT) and photothermal therapy (PTT), respectively. After degradation in the tumor microenvironment (TME), the released Mn²⁺ is able to act simultaneously as a magnetic resonance (MR) imaging contrast agent (CA) and as a Fenton-like agent for chemodynamic therapy (CDT). More importantly, synergistic treatment outcomes can be realized by reasonable and optimized design of the hollow nanosystems. This review summarizes various Mn-based hollow nanoplatforms, including hollow Mn_xO_y, hollow matrix-supported Mn_xO_y, hollow Mn-doped nanoparticles, hollow Mn complex-based nanoparticles, hollow Mn-cobalt (Co)-based nanoparticles, and hollow Mn-iron (Fe)-based nanoparticles, for MR imaging-guided cancer therapies. Finally, we discuss the potential obstacles and perspectives of these hollow Mn-based nanotheranostics for translational applications.

HKUST-1 nano metal-organic frameworks combined with ZnGa2O4:Cr3+ near-infrared persistent luminescence nanoparticles for in vivo imaging and tumor chemodynamic and photothermal synergic therapy

The multifunctional theranostic nanoplatform based on the combination of persistent luminescent nanoparticles (PLNPs) and metal-organic frameworks (MOFs) has both in vivo imaging and tumor therapeutic drug-loading functions, providing a new strategy for accurate and effective tumor diagnosis and treatment. Herein, the near-infrared (NIR) PLNP SiO₂@Zn_1.05Ga_1.9O₄:Cr was combined with HKUST-1 MOFs to form a core-shell structure theranostic nanoplatform which possessed the triple function of autofluorescence-free NIR PersL bioimaging, tumor chemodynamic therapy (CDT), and tumor photothermal therapy (PTT). Also, the photothermal conversion efficiency reached 58.7%, which is superior to the reported nano metal-organic framework (NMOF) photothermal reagents. We demonstrated that the nanoplatform could enter the tumors of mice within 0.5 h and could be target-activated by H₂O₂ and H₂S in the tumor cells, resulting in effective PTT and CDT synergistic treatment. Tumor-bearing mice experiments showed that the tumor could be completely cured without harming normal tissue. This theranostic nanoplatform may provide a promising strategy showing imaging, PTT, and CDT synergistic treatment tri-mode for clinical cancer therapy.

Target Deoxyribonucleic Acid-Recycled Lighting-Up Amplifiable Ratiometric Fluorescence Biosensing of Bicolor Silver Nanoclusters Hosted in a Switchable Deoxyribonucleic Acid Construct

Ratiometric assays of label-free dual-signaling reporters with enzyme-free amplification are intriguing yet challenging. Herein, yellow- and red-silver nanocluster (yH-AgNC and rH-AgNC) acting as bicolor ratiometric emitters are guided to site-specifically cluster in two template signaling hairpins (yH and rH), respectively, and originally, both of them are almost non-fluorescent. The predesigned complement tethered in yH is recognizable to a DNA trigger (T_OC) related to SARS-CoV-2. With the help of an enhancer strand (G₁₅E) tethering G-rich bases (G₁₅) and a linker strand (LS), a switchable DNA construct is assembled via their complementary hybridizing with yH and rH, in which the harbored yH-AgNC close to G₁₅ is lighted-up. Upon introducing T_OC, its affinity ligating with yH is further implemented to unfold rH and induce the DNA construct switching into closed conformation, causing T_OC-repeatable recycling amplification through competitive strand displacement. Consequently, the harbored rH-AgNC is also placed adjacent to G₁₅ for turning on its red fluorescence, while the yH-AgNC is retainable. As demonstrated, the intensity ratio dependent on varying T_OC is reliable with high sensitivity down to 0.27 pM. By lighting-up dual-cluster emitters using one G₁₅ enhancer, it would be promising to exploit a simpler ratiometric biosensing format for bioassays or clinical theranostics.

An amplified fluorescence polarization assay for sensitive sensing of organophosphorus pesticides via MnO2 nanosheets

It is highly desirable to develop a simple, efficient and sensitive strategy for organophosphorus pesticides (OPs) in both environment pollution and human health. Herein, a novel amplified fluorescence polarization (FP) biosensor was established for highly sensitive detection of OPs using MnO₂ nanosheets as the signal enhancer. In this system, OPs can suppress the activity of acetylcholinesterase (AChE) efficiently, blocking the hydrolysis reaction of acetylthiocholine (ATCh) to generate thiocholine (TCh) by AChE. TCh can lead the decomposition of MnO₂ nanosheets to manganese ions. So, without the influence of TCh, MnO₂ nanosheets can maintain its original shape and form a stable complex with FAM-DNA, which greatly enhanced the FP signal. This method can tremendously improve the sensitivity of FP with a detection limit of 0.01 ng/mL for diazinon. In addition, it was also applicable to determine other four OPs and investigate the level of diazinon in real water samples. Consequently, the proposed approach provides a new promising platform for detection of OPs and is expected to be used in application of environmental monitoring.

A label-free cyclic amplification strategy for microRNA detection by coupling graphene oxide-controlled adsorption with superlong poly(thymine)-hosted fluorescent copper nanoparticles

Herein, based on a terminal deoxynucleotidyl transferase (TdT)-mediated superlong poly-T-templated-copper nanoparticles (poly T-CuNPs) strategy, a simple, universal and label-free fluorescent biosensor for the detection of miRNA was constructed by employing graphene oxide (GO) and DNase I. In this strategy, GO and DNase I were used as a switch and amplifier of the signal generation pathway, respectively, and the fluorescence of poly T-CuNPs was used as the signal output. In the presence of target miRNA, the DNA dissociated from the GO surface by forming a miRNA/DNA duplex and was degraded by DNase I. The short oligos with 3'-OH, the product of DNase I degradation, could be recognized by the TdT and added to a long poly-T tail. Finally, the fluorescence signal was output through the synthesis of poly T-CuNPs. As a proof of concept, let-7a was analyzed. The method showed good sensitivity and selectivity with a linear response in the 50 pM-10,000 pM let-7a concentration range and a 30 pM limit of detection (LOD = 30 pM, R² = 0.9954, the relative standard deviation were 2.79%-5.30%). It was also successfully applied to the determination of miRNA in spiked human serum samples. It showed good linearity in the range of 500-10000 pM (R² = 0.9969, the relative standard deviation were 1.61%-3.85%). Moreover, both the adsorption of GO and the degradation of DNase I are DNA sequence-independent; thus, this method can be applied to the detection of any miRNA simply by changing the assisted-DNA sequence.

Rosmarinic Acid-Capped Silver Nanoparticles for Colorimetric Detection of CN- and Redox-Modulated Surface Reaction-Aided Detection of Cr(VI) in Water

Rosmarinic acid-capped silver nanoparticles (Ro-AgNPs) were prepared and applied as a probe for selective colorimetric detection of cyanide (CN-) and chromium(VI) [Cr(VI)] under different conditions in aqueous media. The carbon atom of CN- interacts with the AgNPs, and the carbon atom donates electrons from the HOMO to the vacant orbitals of the coordinatively unsaturated surface atom (Ag0). After donating electrons, CN- attached onto the surface of the nanoparticles becomes very reactive and interacts with dissolved oxygen and generates reactive oxygen species (ROS) such as superoxide (O2 -), singlet oxygen (1O2), and so forth. In this process, Ag0 oxidizes to Ag+ and combines with CN- forming water-insoluble AgCN, and the ROS (O2 -) formed reacts with Ag/Ag+ to form Ag2O. The oxidation of Ag0 to Ag+ resulted in dissolution of AgNPs, which causes disappearance of the surface plasmon resonance band and color change from yellow to colorless. For detection of Cr(VI), ascorbic acid and CN- were added first; the ascorbic acid replaced the rosmarinic acid and then reduced the added Cr(VI) to Cr(III), and, in this process, ascorbic acid was oxidized to dehydroascorbic acid, which moved away from the nanoparticles' surface. CN- then interacted with the surface Ag0 atom, got activated, and interacted with dissolved oxygen forming Ag+ and ROS, which then followed the same process as described for CN- to form AgCN and Ag2O with a color change. The limits of detection were found to be 0.01 and 0.03 μM for CN- and Cr(VI), respectively. The material was also used for sensing CN- and Cr(VI) in real samples, and the results obtained were satisfactory. For field application, agarose-based strips were prepared by immobilizing the nanoparticles onto the agarose film and successfully used for the detection of CN- and Cr(VI) in water.

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.

Intelligent demethylase-driven DNAzyme sensor for highly reliable metal-ion imaging in living cells

The accurate intracellular imaging of metal ions requires an exquisite site-specific activation of metal-ion sensors, for which the pervasive epigenetic regulation strategy can serve as an ideal alternative thanks to its orthogonal control feature and endogenous cell/tissue-specific expression pattern. Herein, a simple yet versatile demethylation strategy was proposed for on-site repairing-to-activating the metal-ion-targeting DNAzyme and for achieving the accurate site-specific imaging of metal ions in live cells. This endogenous epigenetic demethylation-regulating DNAzyme system was prepared by modifying the DNAzyme with an m⁶A methylation group that incapacitates the DNAzyme probe, thus eliminating possible off-site signal leakage, while the cell-specific demethylase-mediated removal of methylation modification could efficiently restore the initial catalytic DNAzyme for sensing metal ions, thus allowing a high-contrast bioimaging in live cells. This epigenetic repair-to-activate DNAzyme strategy may facilitate the robust visualization of disease-specific biomarkers for in-depth exploration of their biological functions.

Recent Advances of Manganese-Based Hybrid Nanomaterials for Cancer Precision Medicine

Cancer precision medicine (CPM) could tailor the best treatment for individual cancer patients, while imaging techniques play important roles in its application. With the characteristics of noninvasion, nonionized, radiation-free, multidimensional imaging function, and real-time monitoring, magnetic resonance imaging (MRI) is an effective way for early tumor detection, and it has become a tower of strength in CPM imaging techniques. Due to linkage with nephrogenic systemic fibrosis (NSF), gadolinium (Gd)-based contrast agent (CA), which was long used in MRI, has been restricted by the Food and Drug Administration (FDA). In this review, we would like to introduce the manganese (Mn)-based CAs that could significantly increase the safety of MRI CAs by realizing more superior performance and functions simultaneously in the diagnosis and treatment of tumors. Also, recent advances in Mn-based hybrid nanomaterials for CPM are summarized and discussed.

Smart Catalyzed Hairpin Assembly-Induced DNAzyme Nanosystem for Intracellular UDG Imaging

Uracil DNA glycosylase (UDG) is one of the key initiators for the base excision repair pathway. Since abnormal UDG expression is associated with various diseases, sensitive detection of UDG activity is critical for early clinical diagnosis. Here, a smart catalyzed hairpin assembly (CHA)-DNAzyme nanosystem is developed for intracellular UDG imaging by incorporating CHA and DNAzyme onto MnO₂ nanosheets. In this strategy, the biodegradable MnO₂ nanosheets are employed as nanocarriers for efficiently adsorbing and delivering five DNA probes into cells by endocytosis. Then, the MnO₂ nanosheets are degraded by cellular glutathione to release the DNA modules at the same intracellular position. Liberated Mn²⁺, an indispensable DNAzyme cofactor, was used to promote catalytic cleavage for facilitating the cascade process in cells. Based on the uracil site-recognition and -excision operation of the target UDG, the activated CHA-DNAzyme nanosystem generates lots of DNAzyme-assisted CHA products, turning on the fluorescence resonance energy transfer response. This autocatalytic CHA-DNAzyme nanosystem provides a detectable minimum UDG concentration of 0.23 mU/mL, which is comparable to some reported UDG detection approaches. As a multiple signal amplification strategy, the CHA-DNAzyme nanosystem realizes the UDG imaging in living cells with enhanced sensitivity, indicating great promise in the prediction and diagnosis of early-stage cancer.

A novel fluorescent aptasensor based on exonuclease-assisted triple recycling amplification for sensitive and label-free detection of aflatoxin B1

Aflatoxins are the most toxic type of mycotoxins, which may cause serious carcinogenesis, teratogenesis, and mutagenesis to humans and animals. In this work, we demonstrate a novel label-free fluorescent aptasensor based on exonuclease-assisted triple recycling amplification for the sensitive detection of aflatoxin B1 (AFB1). With the close cooperation of T7 exonuclease and three elaborately designed hairpin probes, the target AFB1 can perform three consecutive cycles of amplification reactions. In this process, each hairpin probe is fully utilized, and the target AFB1, the secondary target and the tertiary target are recycled, thereby achieving a high amplification. Interestingly and importantly, the secondary and tertiary targets generated by amplification are also excellent DNA template sequences for silver nanoclusters (AgNCs). In the presence of NaBH₄ and AgNO₃, a great number of DNA-AgNCs are synthesized, thereby producing a strong fluorescent signal. Under optimal conditions, the developed aptasensor exhibited high sensitivity to AFB1 with a low detection limit of 0.19 pg mL^-1 and a wide dynamic range of 1 × 10^-6-1 μg mL^-1. In addition, the aptasensor also performed well in the determination of AFB1 in real samples.

In situ synthesis of fluorescent polydopamine on biogenic MnO2 nanoparticles as stimuli responsive multifunctional theranostics

Multifunctional nanocomposites have drawn great attention in clinical applications because of their ability to integrate diagnostic and therapeutic functions. Manganese dioxide (MnO₂), owing to its biocompatibility and magnetic resonance imaging (MRI) properties, has been widely applied in biomedical research. Our previous work on biogenic MnO₂ nanoparticles (Bio-MnO₂ NPs) revealed that intrinsic photothermal properties and stimuli-responsive MRI imaging are particularly promising for the development of theranostic systems. However, further improvement in the photothermal therapy (PTT) performance of Bio-MnO₂ NPs is still required. Herein, we have improved the PTT efficiency of Bio-MnO₂ NPs by in situ synthesis of fluorescent polydopamine (PDA) while generating additional stimuli responsive fluorescence properties in this system, thus further broadening the scope of their theranostic functions. These synthesis conditions are mild and green. The fluorescence of PDA was quenched by capping Bio-MnO₂ NPs and could be recovered upon degradation of Bio-MnO₂ NPs inside tumour cells. Additionally, Mn²⁺ released from the nanoparticles can support T₁-weighted MR imaging. Compared to the Bio-MnO₂ NPs alone, the integration of Bio-MnO₂ NPs and PDA significantly enhances the photothermal performance in vitro and in vivo. With their high biocompatibility, these multifunctional composite nanodevices hold great potential for fluorescence imaging and MRI-guided photothermal therapy.

Enzymatically synthesised MnO2 nanoparticles for efficient near-infrared photothermal therapy and dual-responsive magnetic resonance imaging

Manganese dioxide (MnO2) nanoparticles (NPs) are highly attractive for biomedical applications due to their biocompatibility, stimuli-responsive magnetic resonance imaging (MRI) properties and capability to modulate the hypoxic tumour microenvironment (TME). However, conventional MnO2 NPs do not possess photothermal therapy (PTT) functions except for hybrids with other photothermal materials. Herein, we first reveal the extraordinary photothermal conversion efficiency (44%) of enzymatically synthesised MnO2 NPs (Bio-MnO2 NPs), which are distinct from chemically synthesised MnO2 NPs. In addition, the Bio-MnO2 NPs revealed high thermal recycling stability and solubility as well as dual pH- and reduction-responsive MRI enhancement for tumour theragnosis. These NPs were prepared through a facile MnxEFG enzyme-mediated biomineralization process. The MnxEFG complex from Bacillus sp. PL-12 is the only manganese mineralization enzyme that could be heterologously overexpressed in its active form to achieve Bio-MnO2 NPs without a bacterial host. The hexagonal layer symmetry of the Bio-MnO2 NPs is the key feature facilitating the high photothermal conversion efficiency and TME-responsive T1-weighted MRI. Evaluations both in vitro at the cellular level and in vivo in a systematic tumour-bearing mouse xenograft model demonstrated the high photothermal ablation efficacy of the Bio-MnO2 NPs, which achieved complete tumour eradication with high therapeutic biosafety without obvious reoccurrence. Moreover, stimuli-responsive MR enhancement potentially allows imaging-guided precision PTT. With their excellent biocompatibility, mild synthesis conditions and relatively simple composition, Bio-MnO2 NPs hold great translational promise.

Smart Multivariate Spectrophotometric Assisted Techniques for Simultaneous Determination of Ephedrine Hydrochloride and Naphazoline Nitrate in the Presence of Interfering Parabens

Background:

PARTIAL Least Squares (PLS) and Principal Component Regression (PCR) are two well-known chemometric methods based on dimension reduction techniques. They can be very practical analyzing a large data set of multiple correlated predictor variables.

Objective:

In the presented work, the resolving power of spectrophotometric assisted mathematical techniques was implemented for the simultaneous determination of two active ingredients; ephedrine hydrochloride (EPH) and naphazoline nitrate (NAPH), in a matrix of excipients.

Methods:

To build the PLS and PCR models, a calibration set was prepared where the two drugs, in combination with the interfering parabens, were modeled by multilevel multifactor design. The proposed models successfully predicted the concentrations of both drugs in validation samples with low Root Mean Squared Error of Prediction (RMSEP).

Results:

The results revealed the ability of the mentioned multivariate calibration models to analyze EPH and NAPH in the presence of the interfering parabens with high selectivity in the concentration ranges of 4.00-20.00 μg mL-1 and 1.00-9.00 μg mL-1, respectively.

Conclusion:

A commercially available nasal spray was successfully analyzed using the developed methods without interfering with other dosage form additives.

Multifunctional MnO2 nanoparticles for tumor microenvironment modulation and cancer therapy

Tumor microenvironment (TME) is generally featured by low pH values, high glutathione (GSH) concentrations, overproduced hydrogen peroxide (H₂ O₂ ), and severe hypoxia. These characteristics could provide an interior environment for origination and residence of tumor cells and would lead to tumor progression, metastasis, and drug resistance. Therefore, the development of TME-responsive smart nanosystems has shown significant potential to enhance the efficacy of current cancer treatments. Manganese dioxide (MnO₂ )-based nanosystems have attracted growing attentions for applications in cancer treatment as an excellent TME-responsive theranostic platform, due to their tunable structures/morphologies, pH responsive degradation, and excellent catalytic activities. In this review, we mainly summarize the strategies of MnO₂ and its nanocomposites to modulate TME, such as tumor hypoxia relief, excessive GSH depletion, glucose consumption, and tumor immunosuppressive microenvironment moderation. Such MnO₂ -based TME modulation would be beneficial for a wide range of cancer therapies including photodynamic therapy, radiotherapy, sonodynamic therapy, chemodynamic therapy, starvation therapy, and immunotherapy. Next, some representative designs of MnO₂ -based nanoplatforms in other tumor therapies are highlighted. Moreover, we will discuss the challenges and future perspectives of these MnO₂ -based nanosystems for enhanced tumor treatment. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Recent Advances in Molecular Hydrogen Research Reducing Exercise-Induced Oxidative Stress and Inflammation

Physical exercise-induced oxidative stress and inflammation may be beneficial when exercise is a regular activity, but it is rather harmful when exercise is exhaustive and performed by unaccustomed organisms. Molecular hydrogen (H₂) has recently appeared as a potent antioxidant and anti-inflammatory molecule in numerous pathological conditions. However, its role is relatively unknown under physiological conditions such as physical exercise. Therefore, this review summarizes the current knowledge of the H₂, reducing oxidative stress and inflammation in physical exercise, reporting data from both animal and human studies.

A dual-functional magnetic microsphere for ICP-MS quantification and fluorescence imaging of matrix metalloproteinase 2 in cell secretion

Matrix metalloproteinase 2 (MMP2) plays an important role in tumor growth, invasion and metastasis. In this work, a dual-functional magnetic microsphere probe was designed for ICP-MS quantification and fluorescence imaging of MMP2 in cell secretion. In the designed probe, a NH₂-peptide (-FAM)-biotin was used as a bridge for the combination of carboxylated magnetic beads (MBs-COOH) and streptavidin functionalized gold nanoparticle (Au NP-SA). Initially, the fluorescence of FAM was quenched by Au NP. Since the NH₂-peptide (-FAM)-biotin had a MMP2-specifically recognized sequence, the peptide was specifically cleaved in the presence of MMP2, thus releasing Au NP for the ICP-MS quantification of MMP2 and turning on the fluorescence of FAM for the fluorescence imaging of MMP2. Under the optimal experimental conditions, a linear range of 0.05-50 ng mL^-1 and a limit of detection of 0.02 ng mL^-1 were obtained for MMP2. The relative standard deviation (n = 7, c = 0.1 ng mL^-1) of the proposed method was 5.4%. With good sensitivity and good accuracy, the proposed method realized the quantification and imaging of MMP2 in A549 cell secretion. The proposed method was applied to monitor the expression of MMP2 in the A549 cell secretion under the stimulation of Cd²⁺, providing a new detection strategy in the study of MMP2-related life process.

Development of General Methods for Detection of Virus by Engineering Fluorescent Silver Nanoclusters

Viruses have caused significant damage to the world. Effective detection is required to relieve the impact of viral infections. A biomolecule can be used as a template such as deoxyribonucleic acid (DNA), peptide, or protein, for the growth of silver nanoclusters (AgNCs) and for recognizing a virus. Both the AgNCs and the recognition elements are tunable, which is promising for the analysis of new viruses. Considering that a new virus such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) urgently requires a facile sensing strategy, various virus detection strategies based on AgNCs including fluorescence enhancement, color change, quenching, and recovery are summarized. Particular emphasis is placed on the molecular analysis of viruses using DNA stabilized AgNCs (DNA-AgNCs), which detect the virus's genetic material. The more widespread applications of AgNCs for general virus detection are also discussed. Further development of these technologies may address the challenge for facile detection of SARS-CoV-2.

DNA Transformations for Diagnosis and Therapy

Due to its unique physical and chemical characteristics, DNA, which is known only as genetic information, has been identified and utilized as a new material at an astonishing rate. The role of DNA has increased dramatically with the advent of various DNA derivatives such as DNA-RNA, DNA-metal hybrids, and PNA, which can be organized into 2D or 3D structures by exploiting their complementary recognition. Due to its intrinsic biocompatibility, self-assembly, tunable immunogenicity, structural programmability, long stability, and electron-rich nature, DNA has generated major interest in electronic and catalytic applications. Based on its advantages, DNA and its derivatives are utilized in several fields where the traditional methodologies are ineffective. Here, the present challenges and opportunities of DNA transformations are demonstrated, especially in biomedical applications that include diagnosis and therapy. Natural DNAs previously utilized and transformed into patterns are not found in nature due to lack of multiplexing, resulting in low sensitivity and high error frequency in multi-targeted therapeutics. More recently, new platforms have advanced the diagnostic ability and therapeutic efficacy of DNA in biomedicine. There is confidence that DNA will play a strong role in next-generation clinical technology and can be used in multifaceted applications.

Recent advances in templated synthesis of metal nanoclusters and their applications in biosensing, bioimaging and theranostics

As a kind of promising nanomaterials, metal nanoclusters (MNCs) generally composed of several to hundreds of metal atoms have received increasing interest owing to their unique properties, such as ultrasmall size (<2 nm), fascinating physical and chemical properties, and so on. Recently, template-assisted synthesis of MNCs (e.g., Au, Ag, Cu, Pt and Cd) has attracted extensive attention in biological fields. Up to now, various templates (e.g., dendrimers, polymers, DNAs, proteins and peptides) with different configurations and spaces have been applied to prepare MNCs with the advantages of facile preparation, controllable size, good water-solubility and biocompatibility. Herein, we focus on the recent advances in the template-assisted synthesis of MNCs, including the templates used to synthesize MNCs, and their applications in biosensing, bioimaging, and disease theranostics. Finally, the challenges and future perspectives of template-assisted synthesized MNCs are highlighted. We believe that this review could not only arouse more interest in MNCs but also promote their further development and applications by presenting the recent advances in this area to researchers from various fields, such as chemistry, material science, physiology, biomedicine, and so on.

A Label-free Electrochemical Immunosensor for Highly Sensitive Detection of TNF α, Based on Star Polymer-modified disposable ITO Electrode

Background:

Biomarkers are very important disease-related biomolecules which should be analyzed sensitive and selective in related physiological fluids or tissues. Tumor necrosis factor-α is a type of cytokine which plays vitlly important roles in different methabolic pathways such as cell death, survival, differentiation, proliferation and migration, and infectious and inflammatory diseases including rheumatoid arthritis, diabetes.

Objective:

In this study, it was aimed to develop a reliable tool based on star-shaped poly(glycidyl methacrylate) polymer coated disposable indium tin oxide electrode for determination of Tumor necrosis factor-α, an important disease biomarker.

Methods:

Star shaped polymer was used as an interface material for anti- Tumor necrosis factor α antibodies immobilization. The antibodies were immobilized covalently onto polymer coated indium tin oxide electrode. Electrochemical impedance spectroscopy and cyclic voltammetry techniques were used for all electrochemical measurements.

Results:

The suggested immunosensor exhibited a linear range between 0.02 and 4 pg/mL Tumor necrosis factor-α, and the detection limit was found as 6 fg/mL. Scanning electron microscopy and atomic force microscopy were used for electrode surface characterization. In addition, the suggested immunosensor was used for Tumor necrosis factor-α sensing in human serum samples. The results displayed recoveries between 97.07 and 100.19%. Moreover, this immunosensor had a simple fabrication procedure and a long storage-stability.

Conclusion:

A new biosensor based on a Star shaped polymer for the ultra sensitive determination of a biomarker Tumor necrosis factor-α was developed. The biosensor presented excellent repeatability and reproducubility, and also wide calibration range for Tumor necrosis factor- α.

Artificial Nanotargeted Cells with Stable Photothermal Performance for Multimodal Imaging-Guided Tumor-Specific Therapy

Organic-inorganic hybrid materials have drawn increasing attention as photothermal agents in tumor therapy due to the advantages of green synthesis, high loading efficiency of hydrophobic drugs, facile incorporation of theranostic iron, and excellent photothermal efficiency without inert components or additives. Herein, we proposed a strategy for biomimetic engineering-mediated enhancement of photothermal performance in the tumor microenvironment (TME). This strategy is based on the specific characteristics of organic-inorganic hybrid materials and endows these materials with homologous targeting ability and photothermal stability in the TME. The hybrid materials perform the functions of cancer cells to target homolytic tumors (acting as "artificial nanotargeted cells (ANTC)"). Inspired by the pH-dependent disassembly behaviors of tannic acid (TA) and ferric ion (Fe^III) and subsequent attenuation of photothermal performance, cancer cell membranes were self-deposited onto the surfaces of protoporphyrin-encapsulated TA and Fe^III nanoparticles to achieve ANTC with TME-stable photothermal performance and tumor-specific phototherapy. The resulting ANTC can be used as contrast agents for concurrent photoacoustic imaging, magnetic resonance imaging, and photothermal imaging to guide the treatment. Importantly, the high loading efficiency of protoporphyrin enables the initiation of photodynamic therapy to enhance photothermal therapeutic efficiency, providing antitumor function with minimal side effects.

Critical role of biosensing on the efficient monitoring of cancer proteins/biomarkers using label-free aptamer based bioassay

Cancer is the second most extended disease during the world with an improved death rate over the past several time. Due to the restrictions of cancer analysis methods, the patient's real survival rate is unknown. Therefore early stage diagnosis of cancer is crucial for its strong detection. Bio-analysis based on biomarkers may help to overcome this problem. Aptamers can be employed as high-affinity tools for cancer detection. The utilization of aptamer-based strategy in cancer investigation and strategy shows new opportunities in biotechnology. The label-free system is an important method to study biomolecules in different sizes, such as biomarkers in real-time because of their greatest sensitivity, selectivity, and multi examination. In this review (with 75 references), excellent features of the label-free aptasensors on the sensitive and accurate monitoring of cancer biomarkers were discussed. Also, the role of advanced of nanomaterials on the construction of label-free aptasensors were investigated. In addition, application of different detection methods such as electrochemical, optical, electronic, and photoelectrochemical (PEC), electrochemiluminescence (ECL) were surveyed. Finally, advantages and limitation of different strategies on the early stage diagnosis of cancer biomarkers were discussed. This article has been updated until July 2020.

Nanostructured manganese dioxide for anticancer applications: preparation, diagnosis, and therapy

Nanostructured manganese dioxide (MnO₂) has attracted extensive attention in the field of anticancer applications. As we all know, the tumor microenvironment is usually characterized by a high glutathione (GSH) concentration, overproduced hydrogen peroxide (H₂O₂), acidity, and hypoxia, which affect the efficacy of many traditional treatments such as chemotherapy, radiotherapy, and surgery. Fortunately, as one kind of redox-active nanomaterial, nanostructured MnO₂ has many excellent properties such as strong oxidation ability, excellent catalytic activity, and good biodegradability. It can be used effectively in diagnosis and treatment when it reacts with some harmful substances in the tumor site. It can not only enhance the therapeutic effect but also adjust the tumor microenvironment. Therefore, it is necessary to present the recent achievements and progression of nanostructured MnO₂ for anticancer applications, including preparation methods, diagnosis, and treatment. Special attention was paid to photodynamic therapy (PDT), bioimaging and cancer diagnosis (BCD), and drug delivery systems (DDS). This review is expected to provide helpful guidance on further research of nanostructured MnO₂ for anticancer applications.

An electrochemical aptasensor based on tetrahedral DNA nanostructures as a signal probe carrier platform for sensitive detection of patulin

In this work, we proposed an electrochemical aptasensor for patulin (PAT) based on tetrahedral DNA nanostructures (TDNs) and thionine (Thi)-labeled Fe₃O₄ nanoparticles (Fe₃O₄NPs)/rGO signal amplification strategy. The rigid structure of TDNs could effectively improve the binding efficiency. Fe₃O₄NPs/rGO with excellent electrical conductivity and large specific surface area was used as a label material, which could load more Thi and accelerate electron transfer. Besides, the unique catalytic properties of Fe₃O₄NPs could achieve active signal amplification. Once PAT existed, PAT aptamer was released from the capture probe, thereby introducing Fe₃O₄NPs/rGO with Thi onto the electrode surface. Therefore, a noticeable increase in Thi current intensity was observed. Under the optimized conditions, the proposed aptasensor showed superior performance with a linear range from 5 × 10^-8 to 5 × 10^-1 μg mL^-1 and a detection limit of 30.4 fg mL^-1. The obtained sensor showed reliable specificity, stability and reproducibility, and was successfully applied to the determination of real samples.

Computed tomography and photoacoustic imaging guided photodynamic therapy against breast cancer based on mesoporous platinum with insitu oxygen generation ability

Photodynamic therapy (PDT) has been widely used in cancer treatment. However, hypoxia in most solid tumors seriously restricts the efficacy of PDT. To improve the hypoxic microenvironment, we designed a novel mesoporous platinum (mPt) nanoplatform to catalyze hydrogen peroxide (H₂O₂) within the tumor cells in situ without an extra enzyme. During the fabrication, the carboxy terminus of the photosensitizer chlorin e6 (Ce6) was connected to the amino terminus of the bifunctional mercaptoaminopolyglycol (SH-PEG-NH₂) by a condensation reaction, and then PEG-Ce6 was modified onto the mPt moiety via the mercapto terminal of SH-PEG-NH₂. Material, cellular and animal experiments demonstrated that Pt@PEG-Ce6 catalyzed H₂O₂ to produce oxygen (O₂) and that Ce6 transformed O₂ to generate reactive oxygen species (ROS) upon laser irradiation. The Pt@PEG-Ce6 nanoplatform with uniform diameter presented good biocompatibility and efficient tumor accumulation. Due to the high atomic number and good near-infrared absorption for Pt, this Pt@PEG-Ce6 nanoplatform showed computed tomography (CT) and photoacoustic (PA) dual-mode imaging ability, thus providing an important tool for monitoring the tumor hypoxic microenvironment. Moreover, the Pt@PEG-Ce6 nanoplatform reduced the expression of hypoxia-inducible factor-1α (HIF-1α) and programmed death-1 (PD-1) in tumors, discussing the relationship between hypoxia, PD-1, and PDT for the first time.

Label-free detection of DNA by a dielectric modulated armchair-graphene nanoribbon FET based biosensor in a dual-nanogap setup

A Double-Gate Armchair-Graphene Nanoribbon FET is proposed to realize a high-sensitive and small-size biosensor in order to detect DNA without high-cost and time-consuming labeling process. Two nanogap cavities open inside the top and bottom gate oxides by the method of sacrificed layer etching. When the DNA biomolecule is introduced to the nanogap cavity, the hybridization event which is actually the formation of a double-strand of DNA will occur thus electrically modulating the GNR channel leading to a change in the drain current. The important report of this research is about attained high sensitivity of the proposed biosensor for a vast spectrum of the DNA biological samples. It is worth noting that a DNA sequence by 23 nucleotides extracted from Neisseria gonorrhoeae can be detected as a special case. An extensive numerical approach has been applied in order to characterize the proposed biosensor. The suggested biosensor has been evaluated by solving Schrödinger equation )SE( with Non-Equilibrium Green Function (NEGF) method in the mode-space coupled into Poisson solver in a self-consistent manner assuming ballistic limit. Two different expressions of sensitivity in terms of the threshold voltage and current have been defined giving a good metric for the sensitivity analysis. The results revealed a relative sensitivity of 1 mV/nm² by a filled area by the DNA about 120 nm² showing the excellent superiority for the proposed biosensor as compared to other counterparts. The effective area of the proposed biosensor obtains 240 nm² which is very small in comparison with other reports highlighting high capability of the biosensor in the detection. It has been shown that the proposed biosensor can be implemented in ultra-scaling domain resulting in considerable increase in the sensitivity promising a potent and reliable candidate for high-sensitive and small-size biosensors. Also, the technical issues on designing the suggested biosensor have been investigated to achieve a useful guideline in detection and identification of the target DNAs.

Tumor Microenvironment-triggered Nanosystems as dual-relief Tumor Hypoxia Immunomodulators for enhanced Phototherapy

Photodynamic therapy (PDT) is a promising strategy in cancer treatment that utilizes photosensitizers (PSs) to produce reactive oxygen species (ROS) and eliminate cancer cells under specific wavelength light irradiation. However, special tumor environments, such as those with overexpression of glutathione (GSH), which will consume PDT-mediated ROS, as well as hypoxia in the tumor microenvironment (TME) could lead to ineffective treatment. Moreover, PDT is highly light-dependent and therefore can be hindered in deep tumor cells where light cannot easily penetrate. To solve these problems, we designed oxygen-dual-generating nanosystems MnO2@Chitosan-CyI (MCC) for enhanced phototherapy. Methods: The TME-sensitive nanosystems MCC were easily prepared through the self-assembly of iodinated indocyanine green (ICG) derivative CyI and chitosan, after which the MnO2 nanoparticles were formed as a shell by electrostatic interaction and Mn-N coordinate bonding. Results: When subjected to NIR irradiation, MCC offered enhanced ROS production and heat generation. Furthermore, once endocytosed, MnO2 could not only decrease the level of GSH but also serve as a highly efficient in situ oxygen generator. Meanwhile, heat generation-induced temperature increase accelerated in vivo blood flow, which effectively relieved the environmental tumor hypoxia. Furthermore, enhanced PDT triggered an acute immune response, leading to NIR-guided, synergistic PDT/photothermal/immunotherapy capable of eliminating tumors and reducing tumor metastasis. Conclusion: The proposed novel nanosystems represent an important advance in altering TME for improved clinical PDT efficacy, as well as their potential as effective theranostic agents in cancer treatment.

Amylase-Protected Ag Nanodots for in vivo Fluorescence Imaging and Photodynamic Therapy of Tumors

BACKGROUND

Fluorescent metallic nanodots (NDs) have become a promising nanoprobe for a wide range of biomedical applications. Because Ag NDs have a high tendency to be oxidized, their synthesis and storage are a big challenge. Thus, the method for preparing stable Ag NDs is urgently needed. Surface modification and functionalization can enrich the capability of Ag NDs.

METHODS

In this work, fluorescent Ag NDs were synthesized in deoxygenated water by using porcine pancreatic α-amylase (PPA) as the stabilizing/capping agent. The absorption and fluorescence of PPA-protected Ag NDs (PPA@AgNDs) were measured with a spectrophotometer and a spectrofluorometer, respectively. The morphology of PPA@AgNDs was characterized by high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM). The biocompatibility of PPA@AgNDs was evaluated by tetrazolium (MTT)-based assay. PolyLys-Cys-SH (sequence: KKKKKKC) peptides were conjugated to PPA@AgNDs via heterobifunctional crosslinkers. PolyLys-Cys-linked PPA@AgNDs absorbed 5-aminolevulinic acid (ALA) by electrostatic interaction at physiological pH. The capability of tumor targeting was evaluated by intravenously injecting PPA@AgND-ALA into 4T1 breast cancer xenograft mouse models. Photodynamic therapy (PDT) against tumors was performed under 635 nm laser irradiation.

RESULTS

PPA@AgNDs emitted at 640 nm with quantum yield of 2.1%. The Ag NDs exhibited strong photostability over a long period and a fluorescence lifetime of 5.1 ns. PPA@AgNDs easily entered the cells to stain the nuclei, showing the capabilities of living cell imaging with negligible cytotoxicity. ALA-loaded PPA@AgNDs (PPA@AgND-ALA) presented the superiority of passive tumor targeting via the enhanced permeability and retention (EPR) effect. Tumors were visualized in the near-infrared (NIR) region with reduced background noise. ALA molecules released from PPA@AgND-ALA was converted into the photosensitizer (PS) of protoporphyrin IX (PpIX) intracellularly and intratumorally, which greatly improved the PDT efficacy.

CONCLUSION

Our approach opens a new way to design a novel theranostic nanoplatform of PPA@AgND-ALA for effective tumor targeting and fluorescence image-guided PDT.

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.

Green Layer-by-Layer Assembly of Porphyrin/G-Quadruplex-Based Near-Infrared Nanocomposite Photosensitizer with High Biocompatibility and Bioavailability

A simple and green layer-by-layer assembly strategy is developed for the preparation of a highly bioavailable nanocomposite photosensitizer by assembling near-infrared (NIR) light-sensitive porphyrin/G-quadruplex complexes on the surface of a highly biocompatible nanoparticle that is prepared via Zn²⁺-assisted coordination self-assembly of an amphiphilic amino acid. After being efficiently delivered to the target site and internalized into tumor cells via enhanced permeability and retention effect and interactions between aptamers and tumor markers, the as-prepared nanoassembly can be directly used as an NIR light-responsive photosensitizer for tumor photodynamic therapy (PDT) since the porphyrin/G-quadruplex complexes are exposed on the nanoassembly surface and kept in an active state. It can also disassemble under the synergistic stimuli of an acidic pH environment and overexpressed glutathione, leasing more efficient porphyrin/G-quadruplex composite photosensitizers while reducing the interference caused by glutathione-dependent ¹O₂ consumption. Since the nanoassembly can work no matter if it is disassembled or not, the compulsory requirement for in vivo photosensitizer release is eliminated, thus resulting in the great improvement of the bioavailability of the photosensitizer. The PDT applications of the nanoassembly were well demonstrated in both in vitro cell and in vivo animal experiments.

DNA Dumbbell and Chameleon Silver Nanoclusters for miRNA Logic Operations

Multiplex miRNA analysis is a fundamental issue for exploring a complex biological system and early diagnosis of miRNA-related diseases. Herein, we have developed a series of novel logic gates for miRNA analysis coupling DNA nanostructures and chameleon silver nanoclusters (AgNCs). DNA dumbbell structures are firstly designed with two independent nucleation sequences for AgNCs at the 5' and 3' ends, respectively. By introducing different miRNA inputs, separations of two AgNCs are controlled and the fluorescence property of AgNCs changes. By studying the ratiometric fluorescence responses, sensitive and selective analysis of multiple miRNAs can be achieved. The present work provides powerful tools for miRNA diagnostics and may also guide future DNA nanostructure-based logic gates.