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In this feature article, properties of nanodiamonds in photophysics, surface modification and biocompatibility are discussed, followed by their applications in therapy and bioimaging.

In this study, we synthesized two phosphoramidites based on 2,7-bis-{4-nitro-8-[3-(2-propyl)-styryl]}-9,9-bis-[1-(3,6-dioxaheptyl)]-fluorene (BNSF) and 4,4'-bis-{8-[4-nitro-3-(2-propyl)-styryl]}-3,3'-di-methoxybiphenyl (BNSMB) structures as visible light-cleavable linkers for oligonucleotide conjugation. In addition to the commercial ultraviolet (UV) photocleavable (PC) linker, the BNSMB linker was further applied as a building component to construct photoregulated DNA devices as duplex structures, which are functionalized with fluorophores and quenchers. Selective cleavage of PC and BNSMB is achieved in response to ultraviolet (UV) and visible light irradiations as two inputs, respectively. This leads to controllable dissociation of pieces of DNA fragments, which is followed by changes of fluorescence emission as signal outputs of the system. By tuning the number and position of the photocleavable molecules, fluorophores, and quenchers, various DNA devices were developed, which mimic the functions of Boolean logic gates and achieve logic operations in AND, OR, NOR, and NAND gates in response to two different wavelengths of light inputs. By sequence design, the photolysis products can be precisely programmed in DNA devices and triggered to release in a selective and/or sequential manner. Thus, this photoregulated DNA device shows potential as a wavelength-dependent drug delivery system for selective control over the release of multiple individual therapeutic oligonucleotide-based drugs. We believe that our work not only enriches the library of photocleavable phosphoramidites available for bioconjugation but also paves the way for developing spatiotemporal-controlled, orthogonal-regulated DNA-based logic devices for a range of applications in materials science, polymers, chemistry, and biology.

Nucleic acids are emerging as powerful and functional biomaterials due to their molecular recognition ability, programmability, and ease of synthesis and chemical modification. Various types of nucleic acids have been used as gene regulation tools or therapeutic agents for the treatment of human diseases with genetic disorders. Nucleic acids can also be used to develop sensing platforms for detecting ions, small molecules, proteins, and cells. Their performance can be improved through integration with other organic or inorganic nanomaterials. To further enhance their biological properties, various chemically modified nucleic acid analogues can be generated by modifying their phosphodiester backbone, sugar moiety, nucleobase, or combined sites. Alternatively, using nucleic acids as building blocks for self-assembly of highly ordered nanostructures would enhance their biological stability and cellular uptake efficiency. In this review, we will focus on the development and biomedical applications of structural and functional natural nucleic acids, as well as the chemically modified nucleic acid analogues over the past ten years. The recent progress in the development of functional nanomaterials based on self-assembled DNA-based platforms for gene regulation, biosensing, drug delivery, and therapy will also be presented. We will then summarize with a discussion on the advanced development of nucleic acid research, highlight some of the challenges faced and propose suggestions for further improvement.

Photoacoustic imaging (PAI)-guided photothermal therapy (PTT) has drawn considerable attention due to the deeper tissue penetration and higher maximum permissible exposure. However, current phototheranostic agents are greatly restricted by weak absorption in the second near-infrared (NIR-II, 1000-1700 nm) window, long-term toxicity, and poor photostability. In this report, novel organic NIR-II conjugated polymer nanoparticles (CPNs) based on narrow bandgap donor-acceptor BDT-TBZ polymers were developed for effective cancer PAI and PTT. Characterization data confirmed the high photothermal conversion efficiency, good photostability, excellent PAI performance, and superior biocompatibility of as-obtained CPNs. In addition, in vitro and in vivo tests demonstrated the efficient PTT effect of CPNs in ablating cancer cells and inhibiting tumor growth under 1064 nm laser irradiation. More importantly, the CPNs exhibited rapid clearance capability through the biliary pathway and negligible systematic toxicity. Thus, this work provides a novel organic theranostic nanoplatform for NIR-II PAI-guided PTT, which advances the future clinical translation of biocompatible and metabolizable conjugated nanomaterials in cancer diagnosis and therapy.

Targeted transcriptional modulation in the central nervous system (CNS) can be achieved by adeno-associated virus (AAV) delivery of CRISPR activation (CRISPRa) and interference (CRISPRi) transgenes. To enable AAV packaging, we constructed minimal CRISPRa and CRISPRi transgenes by fusing catalytically inactive Staphylococcus aureus Cas9 (dSaCas9) to the transcriptional activator (VP64 and VP160) and repressor (KRAB and SID4X) domains along with truncated regulatory elements. We then evaluated the performance of these constructs in two reporter assays (bioluminescent and fluorescent), five endogenous genes (Camk2a, Mycn, Nrf2, Keap1, and PDGFRA), and two cell lines (neuro-2a [N2a] and U87) by targeting the promoter and/or enhancer regions. To enable systemic delivery of AAVs to the CNS, we have also generated an AAV1-PHP.B by inserting a 7-mer PHP.B peptide on AAV1 capsid. We showed that AAV1-PHP.B can efficiently cross the blood-brain barrier (BBB) and be taken up by the brain tissue upon lateral tail vein injection in mice. Importantly, a single-dose intravenous administration of AAV1-PHP.B expressing CRISPRa was shown to achieve targeted transgene activation in the mouse brain. This proof-of-concept study will contribute to the development of a non-invasive, specific and potent AAV-CRISPR system for correcting transcriptional misregulation in broad brain areas and multiple neuroanatomical structures., Graphical Abstract

Time-resolved fluorescence is a widely adopted technique for DNA detection due to its high sensitivity and selectivity. However, due to stringent requirements on optics and electronics, instrumentation with time-resolved capability is bulky and expensive, prohibiting their use in portable and point-of-care applications. In this work, a fully-integrated DNA biosensor based on liquid-core waveguide (LCW) optics for fluorescence lifetime analysis is presented. The DNA biosensor encompasses all-custom bioassay, optics and electronics into a microsystem, delivering a near sample-to-answer level of integration. Lifetime, rather than intensity, is exploited as the analytical signal from the V-carbazole probe for the first time. Excitation propagation within the LCW is investigated both analytically and in simulations to achieve high excitation rejection and low temporal dispersion, enabling the proposed LCW-based system with much smaller instrumentation size to deliver comparable lifetime measurement accuracy to traditional systems. Detection of DNA down to 15 base pairs at a low detection limit of 1.38 nM demonstrates the high applicability of the proposed biosensor for compact, application-specific, and low-cost diagnostics devices.

Small interfering RNA (siRNA) that mediates target gene silencing through RNA interference (RNAi) has attracted increasing interest in exploring gene functions as well as treating a variety of diseases. However, the inefficient delivery of the unstable and negatively charged siRNA into cells restricts the progress of the RNAi-based therapeutics. In this work, we describe the development of a nanoplatform based on conjugated polymer dots (Pdots) for efficient siRNA delivery. The cationic lipid G0C14 was introduced in the Pdots for siRNA complexing. The G0C14-containing polymer dots (G-Pdots) not only retained the outstanding fluorescence properties but also enhanced cellular uptake of siRNA. The positively charged G0C14 was able to interact with the negatively charged siRNA via electrostatic interactions, while the G-Pdot/siRNA complexes still remained negatively charged. A prominent property of this nanoplatform was the low cytotoxicity as compared to the commercial agent Lipofectamine, while the gene silencing efficiency was comparable. Our results indicate that biocompatible G-Pdots represent a promising platform for imaging-guided siRNA delivery.

Guanine tracts of human telomeric DNA sequences are known to fold into eight different four-stranded structures that vary by the conformation of guanine nucleotides arranged in the stack of G-tetrads in their core and by different kinds and orders of connecting loops, called G-quadruplexes. Here, we present a novel G-quadruplex structure formed in K+ solution by a human telomeric variant d[(GGGTTA)2GGGTTTGGG], htel21T18. This variant DNA is located in the subtelomeric regions of human chromosomes 8, 11, 17, and 19 as well as in the DNase hypersensitive region and in the subcentromeric region of chromosome 5. Interestingly, single A18T substitution that makes htel21T18 different from the human telomeric sequence results in the formation of a three-layer chair-type G-quadruplex, a fold previously unknown among human telomeric repeats, with two loops interacting through the reverse Watson–Crick A6·T18 base pair. The loops are edgewise; glycosidic conformation of guanines is syn·anti·syn·anti around each tetrad, and each strand of the core has two antiparallel adjacent strands. Our results expand the repertoire of known G-quadruplex folding topologies and may provide a potential target for structure-based anticancer drug design.

Short circulation lifetime, poor blood-brain barrier (BBB) permeability and low targeting specificity limit nanovehicles from crossing the vascular barrier and reaching the tumor site. Consequently, the precise diagnosis of malignant brain tumors remains a great challenge. This study demonstrates the imaging of photostable biopolymer-coated nanodiamonds (NDs) with tumor targeting properties inside the brain. NDs are labeled with PEGylated denatured bovine serum albumin (BSA) and tumor vasculature targeting tripeptides RGD. The modified NDs show high colloidal stability in different buffer systems. Moreover, it is found that discrete dcBSA-PEG-NDs cross the in vitro BBB model more effectively than aggregated NDs. Importantly, compared with the non-targeting NDs, RGD-dcBSA-PEG-NDs can selectively target the tumor site in U-87 MG bearing mice after systemic injection. Overall, this discrete ND system enables efficacious brain tumor visualization with minimal toxicity to other major organs, and is worthy of further investigation into the applications as a unique platform for noninvasive theragnostics and/or thermometry at different stages of human diseases in the brain.

Aptamers are exciting smart molecular probes for specific recognition of disease biomarkers. A number of strategies have been developed to convert target-aptamer binding into physically detectable signals. Since the aptamer sequence was first discovered, a large variety of aptamer-based biosensors have been developed, with considerable attention paid to their potential applications in clinical diagnostics. So far, a variety of techniques in combination with a wide range of functional nanomaterials have been used for the design of aptasensors to further improve the sensitivity and detection limit of target determination. In this paper, the advantages of aptamers over traditional antibodies as the molecular recognition components in biosensors for high-throughput screening target molecules are highlighted. Aptamer-target pairing configurations are predominantly single- or dual-site binding; the design of recognition modes of each aptamer-target pairing configuration is described. Furthermore, signal transduction strategies including optical, electrical, mechanical, and mass-sensitive modes are clearly explained together with examples. Finally, we summarize the recent progress in the development of aptamer-based biosensors for clinical diagnosis, including detection of cancer and disease biomarkers and in vivo molecular imaging. We then conclude with a discussion on the advanced development and challenges of aptasensors.

The development of biocompatible drug delivery vehicles for cancer therapy in the brain remains a big challenge. In this study, we designed self-assembled DNA nanocages functionalized with or without blood-brain barrier (BBB)-targeting ligands, d and we investigated their penetration across the BBB. Our DNA nanocages were not cytotoxic and they were substantially taken up in brain capillary endothelial cells and Uppsala 87 malignant glioma (U-87 MG) cells. We found that ligand modification is not essential for this DNA system as the ligand-free DNA nanocages (LF-NCs) could still cross the BBB by endocytosis inin vitro and in vivo models. Our spherical DNA nanocages were more permeable across the BBB compared with tubular DNA nanotubes. Remarkably, in vivo studies revealed that DNA nanocages could carry anticancer drugs across the BBB and inhibit the tumor growth in a U-87 MG xenograft mouse model. This is the first example showing the potential of DNA nanocages as innovative delivery vehicles to the brain for cancer therapy. Unlike other delivery systems, our work suggest that a DNA nanocage-based platform provides a safe and cost-effective tool for targeted delivery to the brain and therapy for brain tumors.

G-quadruplex structures are becoming useful alternative interaction modules for the assembly of DNA nanomaterials because of their unique inducibility by cations. In this study, we demonstrated a new strategy for the assembly of polymeric DNA nanoarchitectures in the presence of cations, such as K+ and Na+, by employing G-quartet toeholds at the edges of discrete mini-square DNA building blocks as adhesive units. In comparison with the Watson-Crick base-paired duplex linkers, G-quadruplex arrays embedded in the self-assembled DNA system exhibit higher thermal stability. The morphology of these doughnut-shaped or spherical-shaped DNA nanostructures is highly regulated by the orientation of the folded G-quadruplexes either in parallel or antiparallel orientation in response to different cations. Furthermore, this G-quadruplex-mediated assembly strategy is able to manipulate the cycling of DNA assemblies between discrete and polymeric states by means of introducing cations and chelating agents sequentially. This property enables the reversible manipulation of the DNA-based nanosystems for at least 4 cycles. The G-quadruplex array embedded in this self-assembled DNA system can become a scaffold for functional molecules, as a number of organic molecules and proteins exhibit specific binding to these G-quadruplex structures. Besides, embedded G-quadruplexes are also considered as functional components of nanoscale electronic materials due to their electron transport through the stacked orientation of the G-quartet. Therefore, this work is an important step towards obtaining reversible, responsive G-quadruplex-induced DNA-based nanomaterials with versatile functionalities which will be highly useful in further electronic, biomedical and drug-delivery applications.

Nuclear-targeting therapy is considered to be a promising strategy of disease treatment. So far, developing biocompatible and nucleus-permeable delivery systems remains a great challenge. Here, we report a nuclear-targeted delivery platform based on 30 nm nanodiamonds (NDs) which were coated with dual-function, cationic peptides consisting of the human immounodeficiency virus TAT protein and a nuclear localization signal (NLS) peptide in aqueous media. As compared to uncoated NDs, cationic peptide-functionalized NDs were confirmed as a small, safe, and efficient carrier which not only facilitates the enhanced cellular uptake and delivery of loaded cargos to the nucleus in a number of cell lines but also shows their advantages of low cytotoxicity and high affinity to antisense oligonucleotides. This peptide-based modification strategy does not contribute greatly to the size of the ND which is important in its use in constructing nuclear targeting vehicles. Compared with traditional gene silencing in cytopl...

Ruthenium(II) tris(bipyridyl) cationic complex (Ru(bpy)32+) incorporated UiO-67 (Universitetet i Oslo) nanoscale metal–organic frameworks (NMOFs) with an average diameter of ∼92 nm were developed as theranostic nanoplatform for in vitro two-photon fluorescence imaging and photodynamic therapy. After incorporation into porous UiO-67 nanoparticles, the quantum yield, luminescence lifetime, and two-photon fluorescence intensity of Ru(bpy)32+ guest molecules were much improved owing to the steric confinement effect of MOF pores. Benefiting from these merits, the as-synthesized nanoparticles managed to be internalized by A549 cells while providing excellent red fluorescence in cytoplasm upon excitation with 880 nm irradiation. Photodynamic therapeutic application of the Ru(bpy)32+-incorporated UiO-67 NMOFs was investigated in vitro. The Ru(bpy)32+-incorporated UiO-67 NMOFs exhibited good biocompatibility without irradiation while having good cell-killing rates upon irradiation. In view of these facts, the deve...

We design and synthesize a sequence-defined α-l-threose nucleic acid (TNA) polymer, which is complementary to certain nucleotide sites of target anti-apoptotic proteins, BcL-2 involving in development and progression of tumors. Compared to scramble TNA, anti-BcL-2 TNA significantly suppresses target mRNA and protein expression in cancerous cells and shows antitumor activity in carcinoma xenografts, resulting in suppression of tumor cell growth and induction of tumor cell death. Together with good biocompatibility, very low toxicity, excellent specificity features, and strong binding affinity toward the complementary target RNAs, TNAs become new useful biomaterials and effective alternatives to traditional antisense oligonucleotides including locked nucleic acids, morpholino oligomers, and peptide nucleic acids in antisense therapy. Compared to conventional cancer therapy such as radiotherapy, surgery, and chemotherapy, we anticipate that this TNA-based polymeric system will work effectively in antisense cancer therapy and shortly start to play an important role in practical application.

A ubiquitously expressed transcription factor, specificity protein 1 (Sp1), interacts with the amyloid precursor protein (APP) promoter and likely mediates APP expression. Promoter-interaction strengths variably regulate the level of APP expression. Here, we examined the interactions of finger 3 of Sp1 (Sp1-f3) with a DNA fragment containing the APP promoter in different ionic solutions using atomic force microscope (AFM) spectroscopy. Sp1-f3 molecules immobilized on an Si substrate were bound to the APP promoter, which was linked to the AFM tips via covalent bonds. The interactions were strongly influenced by Pb

Nanodiamond-gold nanoparticle (ND-AuNP) dimers constitute a potent tool for controlled thermal heating of biological systems on the nanoscale, by combining a local light-induced heat source with a sensitive local thermometer. Unfortunately, previous solution-based strategies to build ND-AuNP conjugates resulted in large nanoclusters or a broad population of multimers with limited separation efficiency. Here, we describe a new strategy to synthesize discrete ND-AuNP dimers via the synthesis of biotin-labeled DNA-AuNPs through thiol chemistry and its immobilization onto the magnetic bead (MB) surface, followed by reacting with streptavidin-labeled NDs. The dimers can be easily released from MB via a strand displacement reaction and separated magnetically. Our method is facile, convenient, and scalable, ensuring high-throughput formation of very stable dimer structures. This ligand-induced self-assembly approach enables the preparation of a wide variety of dimers of designated sizes and compositions, thus opening up the possibility that they can be deployed in many biological actuation and sensing applications.

Fabrication of DNA/Quantum Dot (QD) complexes making use of electrostatic adsorption forces has advantages of the cost-efficiency and simplicity. To obtain aggregation-free complexes, high molecular weight polymers or the purposefully designed ligands are commonly employed as a bridge between DNA and QDs, which limits their applications in practice. In this work, DNA/QDs complexes were obtained using electrostatic adsorption between cysteamine stabilized CdTe QDs and self-assembled DNA nanocages. Zeta potential, dynamic light scattering and gel electrophoresis measurements demonstrated their aggregation-free state, different from the cases where single-stranded and double-stranded DNAs were used. The appearance of aggregation-free complexes in the case of DNA nanocages was ascribed to their 3D rigid structure. Forster resonance energy transfer (FRET) was demonstrated for the complexes of Cy3 labeled DNA nanocages and QDs, pointing out on the close proximity of these building blocks.

A novel oNB based, double branched photosensitive prodrug 1, and a biphenyl counterpart 2 were designed and synthesized. Their photo-triggered drug release properties were studied by HPLC and UV–vis spectra. The isobestic points in UV–vis spectra of prodrug 1 indicated that homogeneous photolysis reaction happened upon xenon-based light irradiation. HPLC analysis confirmed that (antitumor) chlorambucil was released quickly accompanied with photobyproducts. Prodrug 1 has a half-time (t1/2) of 12.4 min, indicated a good sensitivity towards the light irradiation, making it a promising candidate for applications where UV light is limited.

We develop a versatile recognition system based on 3D triangular-shaped DNA nanotubes by integrating three different aptamer sequences along the three edges. This would allow multiple binding activities to be combined into a single system. The versatility of this nanotube platform can also provide a framework for spatial orientation and positioning of different aptamer-binding ligands in a 'pea-pod' architecture.

A ubiquitously expressed transcription factor, specificity protein 1 (Sp1), interacts with the amyloid precursor protein (APP) promoter and likely mediates APP expression. Promoter-interaction strengths variably regulate the level of APP expression. Here, we examined the interactions of finger 3 of Sp1 (Sp1-f3) with a DNA fragment containing the APP promoter in different ionic solutions using atomic force microscope (AFM) spectroscopy. Sp1-f3 molecules immobilized on an Si substrate were bound to the APP promoter, which was linked to the AFM tips via covalent bonds. The interactions were strongly influenced by Pb2+, considering that substituting Zn2+ with Pb2+ increased the binding affinity of Sp1 for the APP promoter. The results revealed that the enhanced interaction force facilitated APP expression and that APP overexpression could confer a high-risk for disease incidence. An increased interaction force between Sp1-f3 and the APP promoter in Pb2+ solutions was consistent with a lower binding free energy, as determined by computer-assisted analysis. The impact of Pb2+ on cell morphology and related mechanical properties were also detected by AFM. The overexpression of APP caused by the enhanced interaction force triggered actin reorganization and further resulted in an increased Young's modulus and viscosity. The correlation with single-force measurements revealed that altered cellular activities could result from alternation of Sp1-APP promoter interaction. Our AFM findings offer a new approach in understanding Pb2+ associated neurodegeneration.

Lead poisoning in drinking water is a serious threat to public health as it may cause permanent damage to the human nervous system and developmental disorders in children. Many detection methods were developed based on fluorometric, electrochemical, and chemiluminescent assays, but they require precise instruments for signal quantification, which limit the practicality in resource-limited sites. Here we provide a visual detection of lead ions based on nanoparticle-amplified magnetophoresis and Mie scattering. Lead ions first react with GR-5 DNAzyme to release a DNA fragment that can connect magnetic microparticles (MMPs) and gold nanoparticles (AuNPs) through DNA hybridization. Next, the connected AuNPs are collected by magnetic separation and then released. Benefit from the hundreds of oligonucleotides on the AuNPs, tiny amount of AuNPs, which represent low concentration of lead ions, can effectively connect a second pair of MMPs and polystyrene microparticles (PMPs). Upon magnetophoresis, it changes solution turbidity from milky to clear because of the reduction of Mie scattering when less free PMPs suspend in the solution. Our results achieved a limit of detection (LOD) at 55 pM in 100 μl (reaction concentration) and 1.108 nM in 5 μl (sample concentration), which is much lower than the prescribed level in drinking water suggested by Environmental Protection Agency (72 nM). In addition, it also achieves high selectivity against other metal ions (> 50,000 to 1) and is compatible with detection in tap water, providing a visual, sensitive detection without complicated instrument.

A DNA tetrahedron as the most classical and simplest three-dimensional DNA nanostructure has been widely utilized in biomedicine and biosensing. However, the existing assembly approaches usually require harsh thermal annealing conditions, involve the formation of unwanted by-products, and have poor size control. Herein, a facile strategy to fabricate a discrete DNA tetrahedron as a single, thermodynamically stable product in a quantitative yield at room temperature is reported. This system does not require a DNA trigger or thermal annealing treatment to initiate self-assembly. This DNA tetrahedron was made of three chemically ligated triangular-shaped DNAs in unconventional ladder-like arrangements, with measured heights of ∼4.16 ± 0.04 nm, showing extra protections for enzymatic degradation in biological environment. They show substantial cellular uptake in different cell lines via temperature, energy-dependent and clathrin-mediated endocytosis pathways. These characteristics allow our DNA tetrahedron to be used as vehicles for the delivery of very small and temperature-sensitive cargos. This novel assembly strategy developed for DNA tetrahedra could potentially be extended to other highly complex polyhedra; this indicated its generalizability.

We demonstrate the use of two different wavelength ranges of excitation light as inputs to remotely trigger the responses of the self-assembled DNA devices (D-OR). As an important feature of this device, the dependence of the readout fluorescent signals on the two external inputs, UV excitation for 1 min and/or near infrared irradiation (NIR) at 800 nm fs laser pulses, can mimic function of signal communication in OR logic gates. Their operations could be reset easily to its initial state. Furthermore, these DNA devices exhibit efficient cellular uptake, low cytotoxicity, and high bio-stability in different cell lines. They are considered as the first example of a photo-responsive DNA logic gate system, as well as a biocompatible, multi-wavelength excited system in response to UV and NIR. This is an important step to explore the concept of photo-responsive DNA-based systems as versatile tools in DNA computing, display devices, optical communication, and biology.

Visual detection of nucleic acids provides simple and rapid screening for infectious diseases or environmental pathogens. However, sensitivity is the current bottleneck, which may require enzymatic amplification for targets in low abundance and make them incompatible with detection at resource-limited sites. Here we report an enzyme-free amplification that provides a sensitive visual detection of ssDNA/RNA oligonucleotides on the basis of nano "sticky balls". When target oligonucleotides are present, magnetic microparticles (MMPs) and gold nanoparticles (AuNPs) were linked together, allowing the collection of AuNPs after magnetic attraction. Subsequently, the collected AuNPs, which carry many oligonucleotides, were used as the sticky balls to link a second pair of MMPs and polymer microparticles (PMPs). Thus, because the magnetic field can attract the MMPs as well as the linked PMPs to the sidewall, the reduction of suspended PMPs yields a change of light transmission visible by the naked eye. Our results demonstrate that the limit of detection is 10 amol for ssDNAs (228 fM in 45 μL) and 75 amol for ssRNAs (1.67 pM in 45 μL). This method is also compatible with the serum environment and detection of a microRNA, miR-155, derived from human breast cancer cells. With significantly improved sensitivity for visual detection, it provides great potential for point-of-care applications at resource-limited sites.

Two-photon-regulated, shape-changing DNA nanostructures are demonstrated by integrating a DNA nanotube with a two-photon photocleavable module that enables the opening of the cavities of tube, and becomes partially single-stranded in response to two-photon excitation under 800 nm fs laser pulses.

We report the first example of a novel two-photon active, biocompatible, and macrophage cell-membrane permeable carbazole-based cyanine fluorophore for the detection of three biologically important ROS, namely, ˙OH, O2(-) and OCl(-) in solution. This versatile probe shows cellular protection not only in stimulated macrophages from phorbol-12-myristate-13-acetate-induced morphological changes but also lipopolysaccharide-induced cytotoxicity by quenching with the O2(-) and OCl(-) production, respectively. Such protection could be visualized by a distinct change in the fluorescence intensity of the probe.

We demonstrate a nanotechnology approach for the development of cancer-cell-specific subcellular organelle-targeted drug nanocarriers based on photostable nanodiamonds (ND) functionalized with folic acid and mitochondrial localizing sequence (MLS) peptides. We showed that these multifunctional NDs not only distinguish between cancer cells and normal cells, and transport the loaded drugs across the plasma membrane of cancer cells, but also selectively deliver them to mitochondria and induce significant cytotoxicity and cell death compared with free Dox localized in lysosomes. Importantly, the cellular uptake of Dox was dramatically increased in a resistant model of MCF-7 cells, which contributed to the significant circumvention of P-glycoprotein-mediated drug resistance. Our work provides a novel method of designing nanodiamond-based carriers for targeted delivery and for circumventing drug resistance in doxorubicin-resistant human breast adenocarcinoma cancer cells.

Photoresponsive DNA nanomaterials represent a new class of remarkable functional materials. By adjusting the irradiation wavelength, light intensity, and exposure time, various photocontrolled DNA-based systems can be reversibly or irreversibly regulated in respect of their size, shape, conformation, movement, and dissociation/association. This Review introduces the most updated progress in the development of photoresponsive DNA-based system and emphasizes their advantages over other stimuli-responsive systems. Their design and mechanisms to trigger the photoresponses are shown and discussed. The potential application of these photon-responsive DNA nanomaterials in biology, biomedicine, materials science, nanophotonic and nanoelectronic are also covered and described. The challenges faced and further directions of the development of photocontrolled DNA-based systems are also highlighted.

The interaction between the zinc finger transcription factor (ZF–TF) and a specific DNA sequence is characterized by energy landscape parameters such as the dissociation rate constant and binding free energy. Heavy metals, such as lead (Pb) and cadmium (Cd), disturb transcription processes by changing the DNA-binding affinities of ZF–TF. To investigate the interference of heavy-metal ions with DNA transcription, we determined the unbinding force between ZF–TF and DNA by atomic force microscopy (AFM). The results suggest that the binding affinity of this complex is stronger in Pb(II) solution than under normal conditions, while the binding affinity in Cd(II) solution is weaker than under normal conditions. Thus, ZF–TF is an important target for heavy metal poisoning. Gold (Au) has a high affinity with cysteine residues, and so, it effectively coordinates with ZF–TF. AFM was employed to detect the molecular interaction force between ZF–TF and DNA in an Au(I) environment. Data analysis demonstrated that Au(I) helps restore normal binding affinity. The measurement of the unbinding force enabled us to quantify the binding free energy in the dissociation process. Alterations of kinetic parameters, which describe the energy landscape, are associated with metal poisoning disease and can be used to screen drugs for heavy-metal induced disease.The interaction between the zinc finger transcription factor (ZF–TF) and a specific DNA sequence is characterized by energy landscape parameters such as the dissociation rate constant and binding free energy. Heavy metals, such as lead (Pb) and cadmium (Cd), disturb transcription processes by changing the DNA-binding affinities of ZF–TF. To investigate the interference of heavy-metal ions with DNA transcription, we determined the unbinding force between ZF–TF and DNA by atomic force microscopy (AFM). The results suggest that the binding affinity of this complex is stronger in Pb(II) solution than under normal conditions, while the binding affinity in Cd(II) solution is weaker than under normal conditions. Thus, ZF–TF is an important target for heavy metal poisoning. Gold (Au) has a high affinity with cysteine residues, and so, it effectively coordinates with ZF–TF. AFM was employed to detect the molecular interaction force between ZF–TF and DNA in an Au(I) environment. Data analysis demonstrated that Au(I...

Tissue engineering combines biological cells and synthetic materials containing chemical signaling molecules to form scaffolds for tissue regeneration. Mesenchymal stem cells (MSCs) provide an attractive source for tissue engineering due to their versatility of multipotent differentiation. Recently, it has been recognized that both chemical and mechanical stimulations are essential mediators of adhesion and differentiation of MSCs. While significant progress has been made on the understanding of chemical regulatory factors within the extracellular matrix, the effects of mechanical stimulation exerted by nanomaterials on MSCs and the underlying mechanisms are less well-known. The present study showed that the adhesion, proliferation, and differentiation of MSCs cultured on vertically aligned silicon nanowire (SiNW) arrays were significantly different from those on flat silicon wafer and control substrates. The interactions between MSCs and the SiNW arrays caused the stem cells to preferentially differentiate toward osteocytes and chondrocytes but not adipocytes in the absence of supplementary growth factors. Our study demonstrated that Ca(2+) ion channels were transiently activated in MSCs upon mechanical stimulation, which eventually led to activation of Ras/Raf/MEK/ERK signaling cascades to regulate adhesion, proliferation, and differentiation of MSCs. The stretch-mediated transient Ca(2+) ion channel activation and cytoskeleton reorganization during stem cell-nanowire interaction may be early events of lineage-specific potentiation of MSCs in determining the fates of mesenchymal stem cells cultured on microenvironments with specific mechanical properties.

Peptide-functionalized DNA nano-objects selectively target mitochondria and the nucleus by means of nanoneedle-assisted delivery. This technology preserves the cell viability and structural integrity of nanostructures and assists the nano-objects in escaping degradation by endocytosis. This method opens up a new avenue for further in vitro studies of intracellular behaviors of DNA assemblies and their interactions in specific organelles.

Stimuli-responsive DNA-based materials represent a major class of remarkable functional nanomaterials for nano-biotechnological applications. In this review, recent progress in the development of stimuli-responsive systems based on self-assembled DNA nanostructures is introduced and classified. Representative examples are presented in terms of their design, working principles and mechanisms to trigger the response of the stimuli-responsive DNA system upon expose to a large variety of stimuli including pH, metal ions, oligonucleotides, small molecules, enzymes, heat, and light. Substantial in vitro studies have clearly revealed the advantages of the use of stimuli-responsive DNA nanomaterials in different biomedical applications, particularly for biosensing, drug delivery, therapy and diagnostic purposes in addition to bio-computing. Some of the challenges faced and suggestions for further development are also highlighted.

Soluble, thermally stable, and easily processable platinum(II) polyyne polymers of the form trans-[–Pt(PBu3)2C≡CRC≡C–]n (R = 2,8-disubstituted dibenzothiophene, 2,8-disubstituted and 3,7-disubstituted dibenzothiophene-S,S-dioxide units) have been prepared in good yields by CuI-catalyzed polymerization involving the dehydrohalogenating coupling of trans-[PtCl2(PBu3)2] and HC≡CRC≡CH. We report their optical absorption and photoluminescence spectra and compare the results with the monomeric model complexes trans-[Pt(Ph)(PEt3)2C≡CRC≡CPt(Ph)(PEt3)2]. The different electronic properties and linkage geometry of the central R group lead to new organometallic materials with distinct photophysical traits. The polymer with more conjugated 3,7-disubstituted dibenzothiophene-S,S-dioxide mainly displays fluorescence band, while its isomer with less conjugated 2,8-disubstituted spacer effectively enhances the intersystem crossing rate and strong phosphorescence emission can be detected even at room temperature.