Dual-Stimuli Regulation of DNAzyme Cleavage Reaction by Coordination-Driven Nanoprobes for Cancer Cell Imaging

Endowing current artificial chemical reactions (ACRs) with high specificity and intricate activation capabilities is crucial for expanding their applications in accurate bioimaging within living cells. However, most of the reported ACR-based evaluations relied on either single biomarker stimuli or dual activators without obvious biological relevance, still limiting their accuracy and fidelity. Herein, taking the metal-ion-dependent DNAzyme cleavage reaction as a model ACR, two regulators, glutathione (GSH) and telomerase (TE) activated DNAzyme cleavage reactions, were exploited for precise discrimination of cancerous cells from normal cells. DNA probe was self-assembled into the ZIF-90 nanoparticle framework to construct coordination-driven nanoprobes. This approach enhances the stability and specificity of tumor imaging by utilizing biomarkers associated with rapid tumor proliferation and those commonly overexpressed in tumors. In conclusion, the research not only paves the way for new perspectives in cell biology and pathology studies but also lays a solid foundation for the advancement of biomedical imaging and disease diagnostic technologies.

Magnetic Assembly of Eu-Doped NaYF4 Nanorods for Field-Responsive Linearly and Circularly Polarized Luminescence

Colloidal assembly has emerged as an effective avenue for achieving polarized light emission. Here, we showcase the efficacy and versatility of the magnetic colloidal assembly in enabling both linearly and circularly polarized luminescence. Colloidal europium-doped NaYF4 nanorods with surface-bound Fe3O4 nanoparticles are magnetically assembled into linear or chiral superstructures using corresponding fields created in permanent magnets. In a uniform magnetic field generated by opposing poles, the assemblies exhibit photoluminescence with intensity tunable in response to the magnetic field direction, which is higher when the nanorods are perpendicular to light propagation than when they are parallel. The obtained superstructures display strong linearly polarized luminescence when the nanorods are aligned vertically, exhibiting a high degree of polarization up to 0.61. In a quadrupole chiral field generated by permanent magnets, the assemblies emit left-handed or right-handed polarized light depending on the position of the sample placement, attaining a g-factor of 0.04. Furthermore, the superstructures immobilized in a hydrogel film are found to retain their chirality, exhibiting opposite chiroptical responses depending on the sample orientation. The magnetic colloidal assembly approach facilitates the convenient and efficient generation of polarized light emissions from nonmagnetic luminescent materials, thus creating opportunities for tailoring light behavior in developing innovative optoelectronic devices.

Mechanochemical Activation of DNAzyme by Ultrasound

Controlling the activity of DNAzymes by external triggers is an important task. Here a temporal control over DNAzyme activity through a mechanochemical pathway with the help of ultrasound (US) is demonstrated. The deactivation of the DNAzyme is achieved by hybridization to a complementary strand generated through rolling circle amplification (RCA), an enzymatic polymerization process. Due to the high molar mass of the resulting polynucleic acids, shear force can be applied on the RCA strand through inertial cavitation induced by US. This exerts mechanical force and leads to the cleavage of the base pairing between RCA strand and DNAzyme, resulting in the recovery of DNAzyme activity. This is the first time that this release mechanism is applied for the activation of catalytic nucleic acids, and it has multiple advantages over other stimuli. US has higher penetration depth into tissues compared to light, and it offers a more specific stimulus than heat, which has also limited use in biological systems due to cell damage caused by hyperthermia. This approach is envisioned to improve the control over DNAzyme activity for the development of reliable and specific sensing applications.

Recent Advances in the 3D Chiral Plasmonic Nanomaterials

From the view of geometry, chirality is that an object cannot overlap with its mirror image, which has been a fundamental scientific problem in biology and chemistry since the 19th century. Chiral inorganic nanomaterials serve as ideal templates for investigating chiral transfer and amplification mechanisms between molecule and bulk materials, garnering widespread attentions. The chiroptical property of chiral plasmonic nanomaterials is enhanced through localized surface plasmon resonance effects, which exhibits distinctive circular dichroism (CD) response across a wide wavelength range. Recently, 3D chiral plasmonic nanomaterials are becoming a focal research point due to their unique characteristics and planar-independence. This review provides an overview of recent progresses in 3D chiral plasmonic nanomaterials studies. It begins by discussing the mechanisms of plasmonic enhancement of molecular CD response, following by a detailed presentation of novel classifications of 3D chiral plasmonic nanomaterials. Finally, the applications of 3D chiral nanomaterials such as biology, sensing, chiral catalysis, photology, and other fields have been discussed and prospected. It is hoped that this review will contribute to the flourishing development of 3D chiral nanomaterials.

Green and Red Emissive N,O-Doped Chiral Carbon Dots Functionalized with l-Cysteine

Although chirality plays an important role in the natural world, it has also attracted much scientific attention in nanotechnology, in particular, spintronics and bioapplications. Chiral carbon dots (CDs) are promising nanoparticles for sensing and bioimaging since they are biocompatible, ecofriendly, and free from toxic elements. Herein, green and red emissive chiral CDs are fabricated via surface modification treatment of achiral CDs at room temperature. After modification with l-cysteine molecules, the treated CDs demonstrate an intense chiral signal in the region of 200-300 nm with a dissymmetry factor up to 2.3 × 10-4 and high photoluminescence quantum yields of 19% and 15% for green and red emission bands, respectively. These CDs preserve their chiral signal in different ion systems, such as those with pH changes or in the presence of metal ions, along with remarkably low cytotoxicity, making them potential candidates for use as photoluminescent labels for biological objects.

Chiral Plasmonic Hybrid Nanostructures: A Gateway to Advanced Chiroptical Materials

Chirality introduces a new dimension of functionality to materials, unlocking new possibilities across various fields. When integrated with plasmonic hybrid nanostructures, this attribute synergizes with plasmonic and other functionalities, resulting in unprecedented chiroptical materials that push the boundaries of the system's capabilities. Recent advancements have illuminated the remarkable chiral light-matter interactions within chiral plasmonic hybrid nanomaterials, allowing for the harnessing of their tunable optical activity and hybrid components. These advancements have led to applications in areas such as chiral sensing, catalysis, and spin optics. Despite these promising developments, there remains a need for a comprehensive synthesis of the current state-of-the-art knowledge, as well as a thorough understanding of the construction techniques and practical applications in this field. This review begins with an exploration of the origins of plasmonic chirality and an overview of the latest advancements in the synthesis of chiral plasmonic hybrid nanostructures. Furthermore, representative emerging categories of hybrid nanomaterials are classified and summarized, elucidating their versatile applications. Finally, the review engages with the fundamental challenges associated with chiral plasmonic hybrid nanostructures and offer insights into the future prospects of this advanced field.

Chiral probes for biosensing

Chiral inorganic nanomaterials have emerged as a highly promising area of research in nanoscience due to their exceptional light-matter interaction and vast potential applications in chiral sensing, asymmetric catalysis, enantiomer separation, and negative-index materials. We present an overview of the latest advances in chiral inorganic nanomaterials including chiral individual nanoparticles, chiral assemblies, and chiral film-based sensors over the past ten years. Additionally, we discuss the challenges and future perspectives for developing chiral nanomaterials in biosensing applications.

Dual-band chirality-selective absorbing by plasmonic metasurfaces with breaking mirror and rotational symmetry

In this work, we proposed a state-of-the-art metasurface model that breaks the mirror symmetry and rotation symmetry of the structure. It consists of two-layer rotating gold split rings, and has the capability of chirality-selective absorption for circularly polarized light (CPL) in two bands. The absorption peaks for left- and right- circularly polarized (LCP&RCP) light appeared at 989 nm and 1404 nm, respectively, with the maximum absorptivity of 98.5% and 96.3%, respectively. By changing the rotation angle of the two-layer gold split rings, it could also be designed as a single-band chiral metasurface absorber, which only absorbed RCP light but not LCP light, and the absorptivity of RCP light could be up to 97.4%. Furthermore, we found our designed absorbers had the characteristics of great circular dichroism (CD) and symmetric absorption. The physical mechanism of the selective absorption of CPL by the absorbers may be explained by the current vector analysis. In addition, the absorption peak could be tuned with the changing of the geometrical parameters of the structure. The proposed chirality-selective metasurface absorbers could be used in CD spectral detection, optical communication, optical filtering, and other fields.

Circularly Polarized Light Responsive Materials: Design Strategies and Applications

Circularly polarized light (CPL) with the end of optical vector traveling along circumferential trajectory shows left- and right-handedness, which transmits chiral information to materials via complicated CPL-matter interactions. Materials with circular dichroism respond to CPL illumination selectively with differential outputs that can be used to design novel photodetectors. Racemic or achiral compounds under CPL go through photodestruction, photoresolution, and asymmetric synthesis pathways to generate enantiomeric bias and optical activity. By this strategy, helical polymers and chiral inorganic plasmonic nanostructures are synthesized directly, and their intramolecular folding and subsequent self-assembly are photomodulable as well. In the aggregated state of self-assembly and liquid crystal phase, helical sense of the dynamic molecular packing is sensitive to enantiomeric bias brought by CPL, enabling the chiral amplification to supramolecular scale. In this review, the application-guided design strategies of CPL-responsive materials are aimed to be systematically summarized and discussed. Asymmetric synthesis, resolution, and property-modulation of small organic compounds, polymers, inorganic nanoparticles, supramolecular assemblies and liquid crystals are highlighted based on the important developments during the last decades. Besides, applications of light-matter interactions including CPL detection and biomedical applications are also referred.

Self-powered DNA nanomachines for fluorescence detection of lead

A versatile DNA nanomachine detection system has been developed via the combination of DNAzyme with catalytic hairpin assembly (CHA) technology for achieving accurate and sensitive detection of lead ions (Pb²⁺). In the presence of target Pb²⁺, capture DNA nanomachine formed by AuNP and DNAzyme recognized and reacted with Pb²⁺, which yielded an "active" DNAzyme, that induced the cleavage of substrate strand, and then released the initiator DNA (TT) for CHA. With the help of the initiator DNA TT, self-powered CHA was activated to achieve the signal amplification reaction in the detection of DNA nanomachine. Meanwhile, the initiator DNA TT was released and hybridized with the other H1 strand to initiate another CHA, replacement, and turnovers, producing enhanced fluorescence signal of fluorophore FAM (excitation 490 nm/emission 520 nm) for sensitive determination of Pb²⁺. Under the optimized conditions, the DNA nanomachine detection system revealed high selectivity toward Pb²⁺ in the concentration range 50-600 pM, with the limit of detection (LOD) of 31 pM. Recovery tests demonstrated that the DNA nanomachine detection system has excellent detection capability in real samples. Therefore, the proposed strategy can be extended and act as a basic platform for highly accurate and sensitive detection of various heavy metal ions.

Chiral-Selective Antigen-Presentation by Supramolecular Chiral Polymer Micelles

Chirality is ubiquitous in biological systems, which is closely related to biological functions, life processes, and even the pathogenesis of diseases. However, the interface between the chirality of synthetic materials and organisms, particularly the immune system, remains poorly understood. Here, supramolecular chiral polymer micelles (SCPMs) are prepared by complexing antigenic proteins with chiral amino acid-modified polyethyleneimine. The introduction of chirality not only reduces the toxicity of cationic polymer, but also benefits cell uptake and antigen presentation. Especially, D-chirality presents the lowest cytotoxicity, while promoting the highest expression level of costimulatory molecules on dendritic cells compared to L-chirality and achirality. The superiority of D-chirality to stimulate dendritic cell maturation is supported by immunization with D-SCPMs, which achieves significant antigen-specific proliferation of T cells in the spleen, lymph nodes, and tumor of mice. Chirality-mediated antigen processing and presentation are demonstrated by D-SCPMs self-assembled from chiral alkaline histidine or neutral phenylalanine modified polyethyleneimine and tumor associated ovalbumin or severe acute respiratory syndrome coronavirus 2 spike 1 antigenic protein. Immunoactivation enabled by D-chirality opens a window to prepare potent nanotherapeutics for disease prevention and treatment.

Circularly Polarized Light-Enabled Chiral Nanomaterials: From Fabrication to Application

For decades, chiral nanomaterials have been extensively studied because of their extraordinary properties. Chiral nanostructures have attracted a lot of interest because of their potential applications including biosensing, asymmetric catalysis, optical devices, and negative index materials. Circularly polarized light (CPL) is the most attractive source for chirality owing to its high availability, and now it has been used as a chiral source for the preparation of chiral matter. In this review, the recent progress in the field of CPL-enabled chiral nanomaterials is summarized. Firstly, the recent advancements in the fabrication of chiral materials using circularly polarized light are described, focusing on the unique strategies. Secondly, an overview of the potential applications of chiral nanomaterials driven by CPL is provided, with a particular emphasis on biosensing, catalysis, and phototherapy. Finally, a perspective on the challenges in the field of CPL-enabled chiral nanomaterials is given.

Charge-Transfer Complex Doped Photothermal Hydrogels for Discriminating Circularly Polarized Near-Infrared Light

Hydrogels behave as potential candidates to investigate circularly polarized light (CP)-matter interaction, which however suffer from small sensitivity towards circular polarization. Here we report a general protocol to build hydrogels from π-conjugated amino acids with coassembled charge-transfer (CT) complexes, covering a wide scope of donors and acceptors, which were incorporated into stable hydrogel matrices. CT complexes formed block coassemblies with gelators, induced the emergence of macroscopic chiral helices, where efficient chirality transfer occurs to realize tunable Cotton effects from visible light to NIR-I region depending on the structures of CT pairs. The hybrid hydrogels showed tunable photothermal performances with excellent heating-cooling cycling durability. Circularly polarized NIR light selectively triggered gel-solution phase transition at different timescales. Left- and right-CP illumination generates up to 2.5 folds difference in gel collapse time that allows for direct discrimination by naked eyes.

Chiral Au Nanorods: Synthesis, Chirality Origin, and Applications

Chiral Au nanorods (c-Au NRs) with diverse architectures constitute an interesting nanospecies in the field of chiral nanophotonics. The numerous possible plasmonic behaviors of Au NRs can be coupled with chirality to initiate, tune, and amplify their chiroptical response. Interdisciplinary technologies have boosted the development of fabrication and applications of c-Au NRs. Herein, we have focused on the role of chirality in c-Au NRs which helps to manipulate the light-matter interaction in nontraditional ways. A broad overview on the chirality origin, chirality transfer, chiroptical activities, artificially synthetic methodologies, and circularly polarized applications of c-Au NRs will be summarized and discussed. A deeper understanding of light-matter interaction in c-Au NRs will help to manipulate the chirality at the nanoscale, reveal the natural evolution process taking place, and set up a series of circularly polarized applications.

Plasmonic Chiral Metasurface-Induced Upconverted Circularly Polarized Luminescence from Achiral Upconversion Nanoparticles

Chirality induction, transfer, and manipulation have aroused great interest in achiral nanomaterials. Here, we demonstrate strong upconverted circularly polarized luminescence from achiral core-shell upconversion nanoparticles (UCNPs) via a plasmonic chiral metasurface-induced optical chirality transfer. The Yb³⁺-sensitized core-shell UCNPs with good dispersity exhibit intense upconversion luminescence of Tm³⁺ and Nd³⁺ through the energy transfer process. By spin-coating the core-shell UCNPs on this chiral metasurface, strong enhancement and circular polarization modulation of upconversion luminescence can be achieved due to resonant coupling between surface plasmons and upconversion nanoparticles. In the UCNPs-on-metasurface composite, a significant upconversion luminescence enhancement can be achieved with a maximum enhancement factor of 32.63 at 878 nm and an overall enhancement factor of 11.61. The luminescence dissymmetry factor of the induced upconverted circularly polarized luminescence can reach 0.95 at the emission wavelength of 895 nm. The UCNPs-on-metasurface composite yields efficient modulation for the emission intensity and polarization of UCNPs, paving new pathways to many potential applications in imaging, sensing, and anticounterfeiting fields.

Gold-Nanoparticle-Based Chiral Plasmonic Nanostructures and Their Biomedical Applications

As chiral antennas, plasmonic nanoparticles (NPs) can enhance chiral responses of chiral materials by forming hybrid structures and improving their own chirality preference as well. Chirality-dependent properties of plasmonic NPs broaden application potentials of chiral nanostructures in the biomedical field. Herein, we review the wet-chemical synthesis and self-assembly fabrication of gold-NP-based chiral nanostructures. Discrete chiral NPs are mainly obtained via the seed-mediated growth of achiral gold NPs under the guide of chiral molecules during growth. Irradiation with chiral light during growth is demonstrated to be a promising method for chirality control. Chiral assemblies are fabricated via the bottom-up assembly of achiral gold NPs using chiral linkers or guided by chiral templates, which exhibit large chiroplasmonic activities. In describing recent advances, emphasis is placed on the design and synthesis of chiral nanostructures with the tuning and amplification of plasmonic circular dichroism responses. In addition, the review discusses the most recent or even emerging trends in biomedical fields from biosensing and imaging to disease diagnosis and therapy.

Multistage Photoactivatable Zinc-Responsive Nanodevices for Monitoring and Regulating Dysfunctional Islet β-Cells

The dysfunctional islet β-cell triggered by excessive deposition of Zn²⁺ constituted a striking indicator of the occurrence of diabetic disease. However, it remained a formidable challenge to reflect the real-time function of β-cell by monitoring the Zn²⁺ content. Herein, multistage photoactivatable Zn²⁺-responsive nanodevice (denoted as AD2@USD1) was presented for sensing, regulating, and evaluating Zn²⁺ levels in dysfunctional islet β-cells. The photoactivated signatures on the satellite shell layer of the nanodevices and the internally loaded chelating factors effectively identified and intervened in the real-time concentration of Zn²⁺, the photothermal feedback component decorated on the inner core permitted the assessment of the post-intervention Zn²⁺ levels, achieving an integrated intervention and prognostic assessment in response to the abnormal islet β-cell function induced by Zn²⁺ deposition. In this way, one strategy for sensing and regulating islet β-cell function-oriented to Zn²⁺ was established. Our study introduced AD2@USD1 as a tool for effectively sensing, adjusting, and assessing the Zn²⁺ level in islet β-cells with abnormalities, gaining a potential breakthrough in the treatment of diabetes.

Chiroptical Transitions of Enantiomeric Ligand-Activated Nickel Oxides

Ligand-induced chirality in transition-metal oxide (TMO) nanostructures have great potential for designing materials with tunable chiroptical effects. Herein, a facile strategy is reported to prepare chiroptical active nickel-oxide hybrids combined with pH adjustment, and the redox treatment results in ligand transformation, which is attributable to multiple optical transitions in the TMO nanostructures. The theoretical calculation also explains the chiral origins based on their complex models based on empirical analysis. It is also shown that enantiomeric TMO nanoparticles can be used as chiral inducers for chiroptical sensitive polymerization. These results demonstrate that TMO nanostructures can provide rational control over photochemical synthesis and chiral transfer of inorganics nanoarchitecture chirality.

Biological applications of chiral inorganic nanomaterials

Chirality is common in nature and plays the essential role in maintaining physiological process. Chiral inorganic nanomaterials with intense optical activity have attracted more attention due to amazing properties in recent years. Over the past decades, many efforts have been paid to the preparation and chirality origin of chiral nanomaterials; furthermore, emerging biological applications have been investigated widely. This review mainly summarizes recent advances in chiral nanomaterials. The top-down and bottom-up preparation methods and chirality origin of chiral nanomaterials are introduced; besides, the biological applications, such as sensing, therapy, and catalysis, will be introduced comprehensively. Finally, we also provide a perspective on the biomedical applications of chiral nanomaterials.

Recent Advances on DNAzyme-Based Sensing

DNAzymes are functional nucleic acid with catalytic activity. Owing to the high sensitivity, excellent programmability, and flexible obtainment through in vitro selection, RNA-cleaving DNAzymes have attracted increasing interest in developing DNAzyme-based sensors. In this review, we summarize the recent advances on DNAzyme-based sensing applications. We initially conclude two general strategies to expand the library of DNAzymes, in vitro selection to discover new DNAzymes towards different targets of interest and chemical modifications to endue the existing DNAzymes with new function or properties. We then discuss the recent applications of DNAzyme-based sensors for the detection of a variety of important biomolecules both in vitro and in vivo . Finally, perspectives on the challenges and future directions in the development of DNAzyme-based sensors are provided.

Selectively Regulating the Chiral Morphology of Amino Acid-Assisted Chiral Gold Nanoparticles with Circularly Polarized Light

Chiral nanomaterials have attracted increasing attention due to their versatile optical properties. Although circularly polarized (CP) light can serve as an inducer, it has negligible effects because of the short lifetime of the plasmonic states. Here, we propose that the site-selective chirality regulation on the morphology of cysteine (cys) amino acid-assisted chiral gold nanoparticles (cys-chiral AuNPs) can be realized through CP light irradiation. This can result in the increased or decreased circular dichroism (CD) signal intensity. The site-selective growth mechanism of the cys-chiral AuNPs is elucidated with light-matter interactions through the opposite rotation of right(R)/left(L) CP light. The site-selective chirality growth of the cys-chiral AuNPs is ascribed to the morphology evolution induced by the synergy of cys and R/L-CP light, which is clearly analyzed and elucidated with high CD intensities. This work provides a promising alternative strategy to produce high-chirality nanomaterials that can be applied in biomedicine and enantiomer photocatalytic reaction.

Chiral nanomaterials for biosensing, bioimaging, and disease therapies

Chiral plasmonic nanomaterials for biosensing, bioimaging and disease therapy.

Ratiometric FRET Encoded Hierarchical ZrMOF @ Au Cluster for Ultrasensitive Quantifying MicroRNA In Vivo

Here, Zirconium metal-organic frameworks @ gold (ZrMOF @ Au) cluster architectures have been fabricated and then functionalized with two fluorescent dyes (Quasar [QS] and Cyanine5.5 [Cy5.5]) through deoxyribonucleic acid hybridization, to form a fluorescence resonance energy transfer (FRET) encoded ZrMOF  @  Au-QS/Cy5.5 complex. In the presence of the target intracellular microRNA (miR)-21, the fluorescence of Cy5.5 at 705 nm (F₇₀₅ ) decreases and the fluorescence of QS at 665 nm (F₆₆₅ ) increases when Cy5.5 is released from the surface of ZrMOF  @  Au-QS/Cy5.5. The change in the fluorescence ratio (F₇₀₅ /F₆₆₅ ) shows an outstanding linear range of 0.006-67.9 amol/ng_RNA , and the limit of detection is 4.51 zmol/ng_RNA in living cells. The high ratio loading of nucleic acid on surface of ZrMOF @ Au cluster and two fluorescence encoded signal enables better sensitivity and reliability. Zeptomolar sensitivity and good linearity against target affords distinct imaging-based monitoring of the cancer marker miR-21 both in living cells and in vivo. At the same time, the architecture displays remarkable photothermal conversion efficiency (53.7%) and gives rise to outstanding therapy ability in vivo. This strategy offers new avenues for the intelligent quantification of miRNAs for simultaneous diagnoses and treatments of early-stage cancers.

Super-Resolution Imaging With Lanthanide Luminescent Nanocrystals: Progress and Prospect

Stimulated emission depletion (STED) nanoscopy has overcome a serious diffraction barrier on the optical resolution and facilitated new discoveries on detailed nanostructures in cell biology. Traditional fluorescence probes employed in the super-resolution imaging approach include organic dyes and fluorescent proteins. However, some limitations of these probes, such as photobleaching, short emission wavelengths, and high saturation intensity, still hamper the promotion of optical resolution and bio-applications. Recently, lanthanide luminescent probes with unique optical properties of non-photobleaching and sharp emissions have been applied in super-resolution imaging. In this mini-review, we will introduce several different mechanisms for lanthanide ions to achieve super-resolution imaging based on an STED-like setup. Then, several lanthanide ions used in super-resolution imaging will be described in detail and discussed. Last but not least, we will emphasize the future challenges and outlooks in hope of advancing the next-generation lanthanide fluorescent probes for super-resolution optical imaging.

Programmable DNAzyme Computing for Specific In Vivo Imaging: Intracellular Stimulus-Unlocked Target Sensing and Signal Amplification

Molecular probe that enables in vivo imaging is the cornerstone of accurate disease diagnosis, prognostic estimation, and therapies. Although several nucleic acid-based probes have been reported for tumor detection, it is still a challenge to develop programmable methodology for accurately identifying tumors in vivo. Herein, a reconfigurable DNA hybridization-based reaction was constructed to assemble DNAzyme computing that contains an intracellular miRNA-unlocked entropy-driven catalysis module and an endogenous metal ion-responsive DNAzyme module for specific in vivo imaging. By reasonable design, the programmable DNAzyme computing can not only successfully distinguish tumor cells from normal cells but also enable tumor imaging in living mice. Due to its excellent operation with high specificity and sensitivity, this design may be broadly applied in the biological study and personalized medicine.

Exploring the use of upconversion nanoparticles in chemical and biological sensors: from surface modifications to point-of-care devices

Upconversion nanoparticles (UCNPs) have emerged as promising luminescent nanomaterials due to their unique features that allow the overcoming of several problems associated with conventional fluorescent probes. Although UCNPs have been used in a broad range of applications, it is probably in the field of sensing where they best evidence their potential. UCNP-based sensors have been designed with high sensitivity and selectivity, for detection and quantification of multiple analytes ranging from metal ions to biomolecules. In this review, we deeply explore the use of UCNPs in sensing systems emphasizing the most relevant and recent studies on the topic and explaining how these platforms are constructed. Before diving into UCNP-based sensing platforms it is important to understand the unique characteristics of these nanoparticles, why they are attracting so much attention, and the most significant interactions occurring between UCNPs and additional probes. These points are covered over the first two sections of the article and then we explore the types of fluorescent responses, the possible analytes, and the UCNPs' integration with various material types such as gold nanostructures, quantum dots and dyes. All the topics are supported by analysis of recently reported sensors, focusing on how they are built, the materials' interactions, the involved synthesis and functionalization mechanisms, and the conjugation strategies. Finally, we explore the use of UCNPs in paper-based sensors and how these platforms are paving the way for the development of new point-of-care devices.

Biosensing with DNAzymes

This article provides a comprehensive review of biosensing with DNAzymes, providing an overview of different sensing applications while highlighting major progress and seminal contributions to the field of portable biosensor devices and point-of-care diagnostics. Specifically, the field of functional nucleic acids is introduced, with a specific focus on DNAzymes. The incorporation of DNAzymes into bioassays is then described, followed by a detailed overview of recent advances in the development of in vivo sensing platforms and portable sensors incorporating DNAzymes for molecular recognition. Finally, a critical perspective on the field, and a summary of where DNAzyme-based devices may make the biggest impact are provided.

Enantiospecific Detection of D-Amino Acid through Synergistic Upconversion Energy Transfer

D-amino acids (DAAs) are indispensable in regulating diverse metabolic pathways. Selective and sensitive detection of DAAs is crucial for understanding the complexity of metabolic processes and managing associated diseases. However, current DAA detection strategies mainly rely on bulky instrumentation or electrochemical probes, limiting their cellular and animal applications. Here we report an enzyme-coupled nanoprobe that can detect enantiospecific DAAs through synergistic energy transfer. This nanoprobe offers near-infrared upconversion capability, a wide dynamic detection range, and a detection limit of 2.2 μM, providing a versatile platform for in vivo noninvasive detection of DAAs with high enantioselectivity. These results potentially allow real-time monitoring of biomolecular handedness in living animals, as well as developing antipsychotic treatment strategies.

DNA-based plasmonic nanostructures and their optical and biomedical applications

In the past few decades, DNA nanotechnology has been developed a lot due to their appealing features such as structural programmability and easy functionalization. In the emerging field of DNA nanotechnology, DNA molecules are regarded not only as biological information carriers but also as building blocks in the assembly of various two-dimensional and three-dimensional nanostructures, serving as outstanding templates for the bottom-up fabrication of plasmonic nanostructures. By arranging nanoparticles with different components and morphologies on the predesigned DNA templates, various static and dynamic plasmonic nanostructures with tailored optical properties have been obtained. In this review, we summarized recent advances in the design and construction of static and dynamic DNA-based plasmonic nanostructures. In addition, we addressed their emerging applications in the fields of optics and biosensors. At the end of this review, the open questions and future directions of DNA-based plasmonic nanostructure are also discussed.

Wavelength-Selective Activation of Photocaged DNAzymes for Metal Ion Sensing in Live Cells

RNA-cleaving DNAzymes are widely applied as sensors for detecting metal ions in environmental samples owing to their high sensitivity and selectivity, but their use for sensing biological metal ions in live cells is challenging because constitutive sensors fail to report the spatiotemporal heterogeneity of biological processes. Photocaged DNAzymes can be activated by light for sensing purposes that need spatial and temporal resolution. Studying complex biological processes requires logic photocontrol, but unfortunately all the literature-reported photocaged DNAzymes working in live cells cannot be selectively controlled by light irradiation at different wavelengths. In this work, we developed photocaged DNAzymes responsive to UV and visible light using a general synthetic method based on phosphorothioate chemistry. Taking the Zn²⁺-dependent DNAzyme sensor as a model, we achieved wavelength-selective activation of photocaged DNAzymes in live human cells by UV and visible light, laying the groundwork for the logic activation of DNAzyme-based sensors in biological systems.

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

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

Simultaneous detection and speciation of mono- and di-valent copper ions with a dual-channel fluorescent nanoprobe

Redox cyclings between mono-/di-valent copper oxidation states occur in electron transfer reactions that underlie their biological functions. We report herein a dual channel fluorescent nanoprobe for the detection of mono- and di-valent copper ions. The probe, BSA-CDs@RBH/BCS, is designed by decorating carbon dots (CDs) on BSA encapsulated rhodamine hydrazide (RBH) and conjugating with bathocuproine disulfonate (BCS). Cu²⁺ catalyzes the hydrolysis of RBH, and the formed rhodamine B (RhB) shows emission at λ_ex/λ_em = 360/575 nm which ensures Cu²⁺ detection. BSA reduces Cu²⁺ to Cu⁺ and the BCS-Cu⁺ chelate shows emission at λ_ex/λ_em 360/450 nm which ensures Cu⁺ assay. Thus, the dual-channel fluorescence enables speciation of Cu²⁺ and Cu⁺.

Carbon Nanohorns/Pt Nanoparticles/DNA Nanoplatform for Intracellular Zn2+ Imaging and Enhanced Cooperative Phototherapy of Cancer Cells

Superfluous zinc ion (Zn²⁺) in living cells has been identified as a potential tumor biomarker for early cancer diagnosis and cancer progression monitoring. In this paper, we developed a novel carbon nanohorns/Pt nanoparticles/DNA (CNHs/Pt NPs/DNA) nanoplatform based on the clamped hybridization chain reaction (c-HCR) process for intracellular Zn²⁺ imaging and enhanced cooperative phototherapy of cancer cells. Cross-shaped DNAzyme (c-DNAzyme), hairpin DNA1, hairpin DNA2, and aptamer DNA were adsorbed onto the surfaces of CNHs/Pt NPs, and the fluorescence of carboxytetramethyl-rhodamine was also quenched. After entering the living cells, the c-DNAzyme was cleaved to output trigger DNA in the existence of intracellular Zn²⁺ and initiate the c-HCR process for fluorescence amplification. Compared with the single HCR process triggered by a single DNAzyme, the c-HCR process could further improve the amplification efficiency and sensitivity. In addition, such a nanoprobe possesses a catalysis-enhanced photodynamic effect by Pt NP generation of oxygen in a tumor microenvironment and increases the photothermal effect by loading of Pt NPs on CNHs, indicating that this is a promising biological method for cancer diagnosis and cancer cell therapy.

Nucleic Acids Analysis

Nucleic acids are natural biopolymers of nucleotides that store, encode, transmit and express genetic information, which play central roles in diverse cellular events and diseases in living things. The analysis of nucleic acids and nucleic acids-based analysis have been widely applied in biological studies, clinical diagnosis, environmental analysis, food safety and forensic analysis. During the past decades, the field of nucleic acids analysis has been rapidly advancing with many technological breakthroughs. In this review, we focus on the methods developed for analyzing nucleic acids, nucleic acids-based analysis, device for nucleic acids analysis, and applications of nucleic acids analysis. The representative strategies for the development of new nucleic acids analysis in this field are summarized, and key advantages and possible limitations are discussed. Finally, a brief perspective on existing challenges and further research development is provided.

DNAzyme-Metal-Organic Framework Two-Photon Nanoprobe for In situ Monitoring of Apoptosis-Associated Zn2+ in Living Cells and Tissues

Monitoring Zn²⁺ in living cells is critical for fully elucidating the biological process of apoptosis. However, the quantitative intracellular sensing of Zn²⁺ using DNAzyme remains challenging because of issues related to penetration of the signal through tissue, targeted cellular uptake and activation, and susceptibility toward enzymatic degradation. In this study, we developed a novel phosphate ion-activated DNAzyme-metal-organic frameworks (MOFs) nanoprobe for two-photon imaging of Zn²⁺ in living cells and tissues. The design of this nanoprobe involved the loading of a Zn²⁺-specific, RNA-cleaving DNAzyme onto the MOFs through strong coordination between the phosphonate O atoms of the DNAzyme backbone and Zr atoms in the MOFs. This coordination restrained the extracellular activity of DNAzyme; however, after cell entry, the DNAzyme was released from the MOFs through a competitive binding by the phosphate ions present at a high intracellular concentration. Following their release, the two-photon (TP) fluorophore-labeled substrate strands of DNAzyme were cleaved with the aid of Zn²⁺, which resulted in a strong fluorescence signal. The incorporation of a TP fluorophore into the nanoprobe facilitated near-infrared excitation, which allowed the highly sensitive and specific imaging of Zn²⁺ in living cells and tissues at greater depths than possible previously. The TP-DNAzyme-MOFs nanoprobe achieved a low detection limit of 3.53 nM, extraordinary selectivity toward Zn²⁺, and a tissue signal penetration of 120 μm. More importantly, this nanoprobe was successfully used to monitor cell apoptosis, and this application of the DNAzyme-MOFs probe holds great potential for future use in biological studies and medical diagnostics.

Engineering of chiral nanomaterials for biomimetic catalysis

Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications. Especially, their active center similarity and substrate selectivity promoted their superior biocatalytic activity. Here, modification of critical elements, such as size, morphology, nanocrystal facets, chiral surface and active sites, for controlling the catalytic efficiency of individual chiral nanoparticles (NPs) and chiral nanoassemblies has been demonstrated, which had a synergistic effect on overcoming the defects of pre-existing nanocatalysts. Noticeably, application of external forces (light or magnetism) has resulted in obvious enhancement in biocatalytic efficiency. Chiral nanomaterials served as preferable biomimetic nanocatalysts due to their special structural configuration and chemical constitution advantages. Furthermore, the current challenges and future research directions of the preparation of high-performance bioinspired chiral nanomaterials for biological applications are discussed.

Chiral nanomaterial-based biomimetic catalysts can trigger a similar biological effect to natural catalysts and exhibit high performance in biological applications.

DNA-Based Plasmonic Heterogeneous Nanostructures: Building, Optical Responses, and Bioapplications

The integration of multiple functional nanoparticles into a specific architecture allows the precise manipulation of light for coherent electron oscillations. Plasmonic metals-based heterogeneous nanostructures are fabricated by using DNA as templates. This comprehensive review provides an overview of the controllable synthesis and self-assembly of heterogeneous nanostructures, and analyzes the effects of structural parameters on the regulation of optical responses. The potential applications and challenges of heterogeneous nanostructures in the fields of biosensors and bioanalysis, in vivo monitoring, and phototheranostics are discussed.

Chiral Transition Metal Oxides: Synthesis, Chiral Origins, and Perspectives

Transition metal oxides (TMOs) consist of a series of solid materials, exhibiting a wide variety of structures with tunability and versatile physicochemical properties. Such a statement is undeniably true for chiral TMOs since the introduction of chirality brings in not only active optical activities but also geometrical anisotropy due to the symmetry-breaking effect. Although progressive investigations have been made for accurately controlled synthesis and relevant explanations on the chirality origin of such materials, the overall field of chiral TMOs is still in its infancy with adequate space for interdisciplinary communications and development. Herein, therefore, recent advances in both experimental phenomena and theoretical calculations in this area are reviewed, to elucidate the underlying chiral origin with respect to their fabrications process, triggering new insights for further evolution of this field.

Catalytic Asymmetric trans-Selective Hydrosilylation of Bisalkynes to Access AIE and CPL-Active Silicon-Stereogenic Benzosiloles

Chirality widely exists in a diverse array of biologically active molecules and life forms, and the catalytic constructions of chiral molecules have triggered a heightened interest in the fields of chemistry and materials and pharmaceutical sciences. However, the synthesis of silicon-stereogenic organosilicon compounds is generally recognized as a much more difficult task than that of carbon-stereogenic centers because of no abundant organosilicon-based chiral sources in nature. Herein, we reported a highly enantioselective rhodium-catalyzed trans-selective hydrosilylation of silicon-tethered bisalkynes to access chiral benzosiloles bearing a silicon-stereogenic center. This protocol featured with chiral Ar-BINMOL-Phos bearing hydrogen-bond donors as a privileged P-ligand for catalytic asymmetric hydrosilylation that is operationally simple and has 100% atom-economy with good functional group tolerability as well as high enantioselectivity (up to >99:1 er). Benefiting from the trans-selective hydrosilylation with the aid of Rh/Ar-BINMOL-Phos-based asymmetric catalysis, the Si-stereogenic benzosiloles exhibited pronounced aggregation-induced emission (AIE) and circularly polarized luminescence (CPL) activity.

Photocaged functional nucleic acids for spatiotemporal imaging in biology

Imaging of species in living organisms with high spatiotemporal resolution is essential for understanding biological processes. While functional nucleic acids (FNAs), such as catalytic nucleic acids and aptamers, have emerged as effective sensors for a wide range of molecules, photocaged control of these FNAs has played a key role in translating them into bioimaging agents with high spatiotemporal control. In this review, we summarize methods and results of photocaged FNAs based on photolabile modifications, photoisomerization, and photothermal activation. Future directions, including strategies to improve the performance of these photocaged FNAs, are also described.