A gold@polydopamine core-shell nanoprobe for long-term intracellular detection of microRNAs in differentiating stem cells

Remote Control of Heterodimeric Magnetic Nanoswitch Regulates the Adhesion and Differentiation of Stem Cells

Remote, noninvasive, and reversible control over the nanoscale presentation of bioactive ligands, such as Arg-Gly-Asp (RGD) peptide, is highly desirable for temporally regulating cellular functions in vivo. Herein, we present a novel strategy for physically uncaging RGD using a magnetic field that allows safe and deep tissue penetration. We developed a heterodimeric nanoswitch consisting of a magnetic nanocage (MNC) coupled to an underlying RGD-coated gold nanoparticle (AuNP) via a long flexible linker. Magnetically controlled movement of MNC relative to AuNP allowed reversible uncaging and caging of RGD that modulate physical accessibility of RGD for integrin binding, thereby regulating stem cell adhesion, both in vitro and in vivo. Reversible RGD uncaging by the magnetic nanoswitch allowed temporal regulation of stem cell adhesion, differentiation, and mechanosensing. This physical and reversible RGD uncaging utilizing heterodimeric magnetic nanoswitch is unprecedented and holds promise in the remote control of cellular behaviors in vivo.

A common anchor facilitated GO-DNA nano-system for multiplex microRNA analysis in live cells

The design of a nano-system for the detection of intracellular microRNAs is challenging as it must fulfill complex requirements, i.e., it must have a high sensitivity to determine the dynamic expression level, a good reliability for multiplex and simultaneous detection, and a satisfactory biostability to work in biological environments. Instead of employing a commonly used physisorption or a full-conjugation strategy, here, a GO-DNA nano-system was developed under graft/base-pairing construction. The common anchor sequence was chemically grafted to GO to base-pair with various microRNA probes; and the hybridization with miRNAs drives the dyes on the probes to leave away from GO, resulting in "turned-on" fluorescence. This strategy not only simplifies the synthesis but also efficiently balances the loading yields of different probes. Moreover, the conjugation yield of GO with a base-paired hybrid has been improved by more than two-fold compared to that of the conjugation with a single strand. We demonstrated that base-paired DNA probes could be efficiently delivered into cells along with GO and are properly stabilized by the conjugated anchor sequence. The resultant GO-DNA nano-system exhibited high stability in a complex biological environment and good resistance to nucleases, and was able to accurately discriminate various miRNAs without cross-reaction. With all of these positive features, the GO-DNA nano-system can simultaneously detect three miRNAs and monitor their dynamic expression levels.

Polydopamine-Derivated Hierarchical Nanoplatforms for Efficient Dual-Modal Imaging-Guided Combination in Vivo Cancer Therapy

Exploring multifunctional nanomaterials from biocompatible constituents, with integrated imaging and targeted combination therapeutic modalities of tumors in vivo, provides great prospects for clinical cancer theranostic applications. Here, we report a combination strategy for functionalization of polydopamine (PDA) nanohosts with magnetic response and stimuli-controlled drug release capabilities for in vivo cancer theranostic. The high processability of PDA as nanotemplates and surface coating layers as well as its natural affinity to metals facilitated the sandwich of a compact iron oxide nanoparticle layer into the PDA matrix, realizing enhanced near-infrared (NIR) photothermal conversion and strong superparamagnetic responsiveness. Additionally, the high reactivity of the PDA surface allowed facile linkage with reduction-responsive prodrugs and polyethylene glycol chains for in vivo chemotherapy of cancer. Under the magnetic resonance imaging/photoacoustic imaging dual-modal tumor imaging and active magnetic tumor targeting of the nanoagents in vivo, the effective tumor eradication was achieved via synergetic NIR photothermal ablation and anticancer drug delivery.

Chemo-photothermal therapy combination elicits anti-tumor immunity against advanced metastatic cancer

Photothermal therapy (PTT) is a promising cancer treatment modality, but PTT generally requires direct access to the source of light irradiation, thus precluding its utility against disseminated, metastatic tumors. Here, we demonstrate that PTT combined with chemotherapy can trigger potent anti-tumor immunity against disseminated tumors. Specifically, we have developed polydopamine-coated spiky gold nanoparticles as a new photothermal agent with extensive photothermal stability and efficiency. Strikingly, a single round of PTT combined with a sub-therapeutic dose of doxorubicin can elicit robust anti-tumor immune responses and eliminate local as well as untreated, distant tumors in >85% of animals bearing CT26 colon carcinoma. We also demonstrate their therapeutic efficacy against TC-1 submucosa-lung metastasis, a highly aggressive model for advanced head and neck squamous cell carcinoma (HNSCC). Our study sheds new light on a previously unrecognized, immunological facet of chemo-photothermal therapy and may lead to new therapeutic strategies against advanced cancer.

A Universal Upconversion Sensing Platform for the Sensitive Detection of Tumour-Related ncRNA through an Exo III-Assisted Cycling Amplification Strategy

Here, a sensitive and universal noncoding RNA (ncRNA) upconversion sensing nanoplatform is developed. Gold nanoparticles bearing one hairpin DNA (Hp) molecule are conjugated to the linker DNA modified NaYF₄ :Yb, Er@NaYF₄ upconversion nanoparticles by DNA hybridization, leading to quenching of the upconversion emission through fluorescence resonance energy transfer. A signal DNA (SDNA) sequence is designed to open Hp, recovering the upconversion emission. To achieve universality and high sensitivity of the nanoprobe, an exonuclease III (Exo III)-assisted cycling amplification strategy is introduced. A multifunctional hairpin DNA (mHp) containing ncRNA recognition sequence and SDNA sequence is designed to recognize ncRNA and trigger Exo III as a biocatalyst to stepwise disintegrate itself, releasing both ncRNA and SDNA. The released ncRNA can be reused to release more SDNA, which greatly improves the sensing sensitivity. By changing the recognition portion of mHp, various ncRNA can be detected. The sensitive detection of both homeobox (HOX) transcript antisense RNA segment and miR-21 is achieved with this novel strategy, even in human serum, indicating the universality and sensitivity of the proposed strategy. Additionally, the expression level of miR-21 in human breast cancer cell (MCF-7) lysate is successfully measured, suggesting its potential in clinical diagnosis.

A Highly Sensitive Strategy for Fluorescence Imaging of MicroRNA in Living Cells and in Vivo Based on Graphene Oxide-Enhanced Signal Molecules Quenching of Molecular Beacon

In situ imaging of microRNA (miRNA) in living cells and in vivo is beneficial for promoting the studies on miRNA-related physiological and pathological processes. However, the current strategies usually have a low signal-to-background ratio, which greatly affects the sensitivity and imaging performance. To solve this problem, we developed a highly sensitive strategy for fluorescence imaging of miRNA in living cells and in vivo based on graphene oxide (GO)-enhanced signal molecule quenching of a molecular beacon (MB). 2Cy5-MB was designed by coupling two Cy5 molecules onto the opposite ends of MB. The fluorescence intensities of two Cy5 molecules were reduced because of the self-quenching effect. After adsorbing on the GO surface, the fluorescence quenching of the molecules was enhanced by fluorescence resonance energy transfer. This double-quenching effect significantly reduced the fluorescence background. In the presence of one miRNA molecule, the fluorescence signals of two Cy5 molecules were simultaneously recovered. Therefore, a significantly enhanced signal-to-background ratio was obtained, which greatly improved the detection sensitivity. In the presence of miRNA, the fluorescence intensity of 2Cy5-MB-GO recovered about 156 times and the detection limit was 30 pM. Compared with 1Cy5-MB-GO, the elevated fluorescence intensity was enhanced 8 times and the detection limit was reduced by an order of magnitude. Furthermore, fluorescence imaging experiments demonstrated that 2Cy5-MB-GO could visually detect microRNA-21 in various cancer cells and tumor tissues. This simple and effective strategy provides a new sensing platform for highly sensitive detection and simultaneous imaging analysis of multiple low-level biomarkers in living cells and in vivo.

A Gold@Polydopamine Core-Shell Nanoprobe for Long-Term Intracellular Detection of MicroRNAs in Differentiating Stem Cells

MicroRNAs (miRNAs) represent an emerging class of biomarkers for studying and understanding biological events; the development of viable tools for detecting or monitoring the intracellular expression levels of specific miRNAs is of great interest to life scientists and biomedical engineers. Here, we describe the fabrication of a novel class of core-shell nanoprobes that comprise a gold nanoparticle core and a polydopamine (PDA) shell. Our nanoprobes can be used to specifically track the expression profiles of two miRNA markers of osteogenic differentiation (i.e., osteogenesis), namely, miR-29b and miR-31, in differentiating human mesenchymal stem cells (hMSCs). The newly designed nanoprobes may hold great promise in the noninvasive investigation of the long-term dynamics of cellular events such as stem cell differentiation.

Closer to the polydopamine structure: new insights from a combined 13C/1H/2H solid-state NMR study on deuterated samples

¹³C/¹H/²H ss-NMR on deuterated samples provide strong experimental evidence for the most probable monomer connectivity, π–π stacking, and the water dynamics in polydopamine.

Enhancing intracellular microRNA imaging: a new strategy combining double-channel exciting single colour fluorescence with the target cycling amplification reaction

Enhancing microRNA imaging in living cells using double-channel exciting single colour fluorescence coupled with the target cycling amplification reaction.

Optimized polydopamine coating and DNA conjugation onto gold nanorods for single nanoparticle bioaffinity measurements

The formation of a stable polydopamine layer on a nanorod surface depends on the underlying chemistry and optimization enables the formation of packed ssDNA monolayers for bioaffinity applications.

Polydopamine-assisted versatile modification of a nucleic acid probe for intracellular microRNA imaging and enhanced photothermal therapy

MicroRNAs play an important role in various biological processes, and their aberrant expression is closely associated with various human diseases, especially cancer. Real-time monitoring of microRNAs in living cells may help us to understand their role in cellular processes, which can further provide a basis for diagnosis and treatment. In this study, polydopamine was used to assist the versatile modification of a nucleic acid probe for intracellular microRNA imaging and enhanced photothermal therapy. Polydopamine can be covalently linked with a thiol-terminated nucleic acid probe through the Michael addition reaction under slightly alkaline conditions. This modification is mild and can be performed directly in an aqueous solution, which can better resist hydrolysis than the traditional modification processes, resulting in a nanoprobe with better stability and higher loading of nucleic acids. This prepared nanoprobe can easily enter cells without transfection agents and then realize the imaging of intracellular miRNA through fluorescence restoration. Moreover, the coating of PDA can enhance the photothermal conversion efficiency of the nanoprobe, making it suitable for photothermal therapy of cancer. It is expected that the PDA-based versatile modification can help to construct a promising platform for tumor imaging and treatment.

Polydopamine can assist the versatile modification of a nucleic acid probe for intracellular miRNA responsed fluorescence imaging and enhanced photothermal therapy.

Fabrication and evaluation of hemoglobin-based polydopamine microcapsules as oxygen carriers

Polydopamine-hemoglobin (PDA-Hb) microcapsules possess a high oxygen affinity and could bind and release oxygen reversibly as demonstrated by electrochemical methods.

Recent progress in live cell mRNA/microRNA imaging probes based on smart and versatile nanomaterials

We summarize the recent progress in live cell mRNA/miRNA imaging probes based on various versatile nanomaterials, describing their structures and their working principles of bio-imaging applications.

Sensitive detection of intracellular microRNA based on a flowerlike vector with catalytic hairpin assembly

A flowerlike nanovector with horn-shaped tips is developed for in situ detection of intracellular microRNA with multiple signal outputs.

DNAzyme Based Nanomachine for in Situ Detection of MicroRNA in Living Cells

The capability of in situ detection of microRNA in living cells with signal amplification strategy is of fundamental importance, and it will open up a new opportunity in development of diagnosis and prognosis of many diseases. Herein we report a swing DNA nanomachine for intracellular microRNA detection. The surfaces of Au nanoparticles (NPs) are modified by two hairpin DNA. We observe that one DNA (MB2) will open its hairpin structure upon partial hybridization with target miR-21 after entering into cells, and the other part of its hairpin structure could further react with the other hairpin DNA (MB1) to form a Zn²⁺-specific DNAzyme. This results in the disruption of MB1 through shearing action and the release of fluorescein Cy5. To provide an intelligent DNA nanomachine, MB2 is available again with the shearing action to bind with MB1, which provides effective signal amplification. This target-responsive, DNA nanomachine-based method showed a detection limit of 0.1 nM in vitro, and this approach could be an important step toward intracellular amplified detection and imaging of various analytes in living cells.

Trace determination of carbamate pesticides in medicinal plants by a fluorescent technique

The safety issue of using carbamate pesticides in medicinal plants (MPs) has been a global concern and hence attracted attention of many researchers to develop analytical tools for trace pesticides detection. Derived from the fluorescence-based techniques, a rapid, convenient and efficient method for the detection of three carbamate pesticides, including carbofuran, aldicarb and methomyl has been developed by using core-shell QDs. By optimizing experimental parameters, the system demonstrated high detection sensitivities for the investigated carbamates, with the lowest detectable concentrations less than 0.05 μM. The molecular docking study indicated that the selected carbamate pesticides bound to the catalytic active site of acetylcholinesterase via π-π or H-π interactions, which also revealed the potential mechanism of the differences in inhibition strength among the three pesticides on AChE. Moreover, in order to investigate the applicability and reliability of the proposed method for the pesticide analysis in real sample with complex matrix, the matrix effects of eight common MPs have been systematically explored. These findings suggested that this technique was a simple, sensitive and reliable method for rapid determination of carbamate pesticides in real samples, especially those with complex matrices like MPs, vegetables, fruits, and other agricultural crops.

Polydopamine-based concentric nanoshells with programmable architectures and plasmonic properties

Nanoshells, classically comprising gold as the metallic component and silica as the dielectric material, are important for fundamental studies in nanoplasmonics. They also empower a myriad of applications, including sensing, energy harvesting, and cancer therapy. Yet, laborious preparation precludes the development of next-generation nanoshells with structural complexity, compositional diversity, and tailorable plasmonic behaviors. This work presents an efficient approach to the bottom-up assembly of concentric nanoshells. By employing polydopamine as the dielectric material and exploiting its intrinsic adhesiveness and pH-tunable surface charge, the growth of each shell only takes 3-4 hours at room temperature. A series of polydopamine-based concentric nanoshells with programmable nanogap thickness, elemental composition (gold and silver), and geometrical configuration (number of layers) is prepared, followed by extensive structural characterization. Four of the silver-containing nanostructures are newly reported. Systematic investigations into the plasmonic properties of concentric nanoshells as a function of their structural parameters further reveal multiple Fano resonances and local-field "hot spots", infrequently reported plasmonic features for individual nanostructures fabricated using bottom-up wet chemistry. These results establish materials design rules for engineering complex plasmon-based systems originating from the integration of multiple plasmonic elements into defined locations within a compact nanostructure.

A Chiral-Nanoassemblies-Enabled Strategy for Simultaneously Profiling Surface Glycoprotein and MicroRNA in Living Cells

Assemblies of nanomaterials for biological applications in living cells have attracted much attention. Herein, graphene oxide (GO)-gold nanoparticle (Au NP) assemblies are driven by a splint DNA strand, which is designed with two regions at both ends that are complementary with the DNA sequence anchored on the surface of the GO and the Au NPs. In the presence of microRNA (miR)-21 and epithelial cell-adhesion molecule (EpCAM), the hybridization of miR-21 with a molecular probe leads to the separation of 6-fluorescein-phosphoramidite-modified Au NPs from GO, resulting in a decrease in the Raman signal, while EpCAM recognition reduces circular dichroism (CD) signals. The CD signals reverse from negative in original assemblies into positive when reacted with cells, which correlates with two enantiomer geometries. The EpCAM detection has a good linear range of 8.47-74.78 pg mL^-1 and a limit of detection (LOD) of 3.63 pg mL^-1 , whereas miR-21 detection displays an outstanding linear range of 0.07-13.68 amol ng^-1_RNA and LOD of 0.03 amol ng^-1_RNA . All the results are in good agreement with those of the Raman and confocal bioimaging. The strategy opens up an avenue to allow the highly accurate and reliable diagnosis (dual targets) of clinic diseases.

Remote Control of Multimodal Nanoscale Ligand Oscillations Regulates Stem Cell Adhesion and Differentiation

Cellular adhesion is regulated by the dynamic ligation process of surface receptors, such as integrin, to adhesive motifs, such as Arg-Gly-Asp (RGD). Remote control of adhesive ligand presentation using external stimuli is an appealing strategy for the temporal regulation of cell-implant interactions in vivo and was recently demonstrated using photochemical reaction. However, the limited tissue penetration of light potentially hampers the widespread applications of this method in vivo. Here, we present a strategy for modulating the nanoscale oscillations of an integrin ligand simply and solely by adjusting the frequency of an oscillating magnetic field to regulate the adhesion and differentiation of stem cells. A superparamagnetic iron oxide nanoparticle (SPION) was conjugated with the RGD ligand and anchored to a glass substrate by a long flexible poly(ethylene glycol) linker to allow the oscillatory motion of the ligand to be magnetically tuned. In situ magnetic scanning transmission electron microscopy and atomic force microscopy imaging confirmed the nanoscale motion of the substrate-tethered RGD-grafted SPION. Our findings show that ligand oscillations under a low oscillation frequency (0.1 Hz) of the magnetic field promoted integrin-ligand binding and the formation and maturation of focal adhesions and therefore the substrate adhesion of stem cells, while ligands oscillating under high frequency (2 Hz) inhibited integrin ligation and stem cell adhesion, both in vitro and in vivo. Temporal switching of the multimodal ligand oscillations between low- and high-frequency modes reversibly regulated stem cell adhesion. The ligand oscillations further induced the stem cell differentiation and mechanosensing in the same frequency-dependent manner. Our study demonstrates a noninvasive, penetrative, and tunable approach to regulate cellular responses to biomaterials in vivo. Our work not only provides additional insight into the design considerations of biomaterials to control cellular adhesion in vivo but also offers a platform to elucidate the fundamental understanding of the dynamic integrin-ligand binding that regulates the adhesion, differentiation, and mechanotransduction of stem cells.

Electro-Grafted Electrode with Graphene-Oxide-Like DNA Affinity for Ratiometric Homogeneous Electrochemical Biosensing of MicroRNA

This work demonstrated for the first time a simple and rapid approach to endow the electrode with the excellent discrimination ability over single-stranded DNA (ssDNA) and double-stranded DNA (dsDNA) through the robust electrochemical grafting of in situ generated 1-naphthalenesulfonate (NS^-) diazonium salt onto the surface of indium tin oxide (ITO) electrode. On the basis of understanding the influence of sequence and length on the binding affinity of ssDNA and dsDNA toward NS^- grafted ITO (NS^--ITO) electrode, these interesting findings were successfully employed to rationally develop a ratiometric homogeneous electrochemical biosensing platform for microRNA based on the affinity-mediated signal transduction. The achievement of ultrasensitive detection of microRNA lies in a compatibly designed T7 exonuclease-assisted isothermal amplification strategy, in which the presence of target microRNA initiated the continual and opposite affinity inversion of two rationally engineered electrochemical signal reporters, methylene blue (MB) labeled hairpin reporter and ferrocene (Fc) labeled dsDNA reporter, toward NS^--ITO electrode, thereby providing the ratiometric transduction and amplification of the homogeneous electrochemical output signal. By measuring the distinct variation in the peak current intensity ratios of Fc and MB tags, this ratiometric homogeneous electrochemical microRNA biosensing platform showed a detection limit of 25 aM, which is much lower than that of the reported homogeneous electrochemical biosensors. Therefore, we envision that the proposed approach will find useful applications in disease molecular diagnoses and biomedicine.

TEMPO-Conjugated Gold Nanoparticles for Reactive Oxygen Species Scavenging and Regulation of Stem Cell Differentiation

Controlling the differentiation of human mesenchymal stem cells (hMSCs) shows a great potential in regenerative medicine. Because overproduced reactive oxygen species (ROS) have an obvious inhibitory effect on the differentiation and functions of hMSCs, it is highly desirable to develop an effective strategy for ROS scavenging and stem cell differentiation controlling. In this study, gold nanoparticles (Au NPs) with an average size of 40 nm were conjugated with 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) to endow them with ROS-scavenging capacity while holding the beneficial effect of Au NPs. The TEMPO-conjugated Au NPs (Au-PEG-TEMPO NPs) were used for the culture of hMSCs to investigate their effect on ROS scavenging, proliferation, and osteogenic and adipogenic differentiation of hMSCs. The Au-PEG-TEMPO NPs had a negligible influence on cell viability and proliferation of hMSCs and could effectively reduce the ROS level of hMSCs under H₂O₂-exposed conditions because of their excellent cellular uptake. Similar to the counterparts without surface TEMPO modification (Au-mPEG NPs), the Au-PEG-TEMPO NPs could promote the osteogenic differentiation of hMSCs, whereas they could inhibit the adipogenic differentiation of hMSCs. The results indicated that the TEMPO-conjugated Au NPs had high scavenging capacity for overproduced ROS and maintained the promotive effect of Au NPs on osteogenic differentiation of hMSCs without the inhibitory effect of free TEMPO. This study offers a promising strategy for ROS scavenging to control stem cell differentiation in stem cell transplantation and regenerative medicine.

A DNA-Fueled and Catalytic Molecule Machine Lights Up Trace Under-Expressed MicroRNAs in Living Cells

The detection of specific intracellular microRNAs (miRNAs) in living cells can potentially provide insight into the causal mechanism of cancer metastasis and invasion. However, because of the characteristic nature of miRNAs in terms of small sizes, low abundance, and similarity among family members, it is a great challenge to monitor miRNAs in living cells, especially those with much lower expression levels. In this work, we describe the establishment of a DNA-fueled and catalytic molecule machinery in cell signal amplification approach for monitoring trace and under-expressed miRNAs in living cells. The presence of the target miRNA releases the hairpin sequences from the dsDNA (containing the fluorescence resonance energy transfer (FRET) pair-labeled and unfolded hairpin sequences)-conjugated gold nanoparticles (dsDNA-AuNPs), and the DNA fuel strands assist the recycling of the target miRNA sequences via two cascaded strand displacement reactions, leading to the operation of the molecular machine in a catalytic fashion and the release of many hairpin sequences. As a result, the liberated hairpin sequences restore the folded hairpin structures and bring the FRET pair into close proximity to generate significantly amplified signals for detecting trace miRNA targets. Besides, the dsDNA-AuNP nanoprobes have good nuclease stability and show low cytotoxicity to cells, and the application of such a molecular system for monitoring trace and under-expressed miRNAs in living cells has also been demonstrated. With the advantages of in cell signal amplification and reduced background noise, the developed method thus offers new opportunities for detecting various trace intracellular miRNA species.

Instantaneous pH-Boosted Functionalization of Stellate Gold Nanoparticles for Intracellular Imaging of miRNA

Various types of nanoprobes have recently been utilized to monitor living organisms by detecting and imaging intracellular biomarkers, such as microRNAs (miRs). We here present a simple one-pot method to prepare stellate gold nanoparticles functionalized with miR-detecting molecular beacons (SGNP-MBs); low pH conditions permitted the rapid-high loading of MBs on the surface of SGNPs. Compared to the conventional gold nanoparticle-based MBs, SGNPs carried a 4.5-fold higher load of MBs and exhibited a 6.4-fold higher cellular uptake. We demonstrated that SGNP-MBs were successfully internalized in human gastric cancer cell lines and could be used to accurately detect and image intracellular miRs in an miR-specific manner. Furthermore, the relative levels of intracellular miRs in three different cell lines expressing miR-10b (high, moderate, and low levels) could be monitored using SGNP-MBs. Consequently, these results indicated that SGNP-MBs could have applications as highly potent, efficient nanoprobes to assess intracellular miR levels in living cells.

Bacteria-Activated Theranostic Nanoprobes against Methicillin-Resistant Staphylococcus aureus Infection

Despite numerous advanced imaging and sterilization techniques available nowadays, the sensitive in vivo diagnosis and complete elimination of drug-resistant bacterial infections remain big challenges. Here we report a strategy to design activatable theranostic nanoprobes against methicillin-resistant Staphylococcus aureus (MRSA) infections. This probe is based on silica nanoparticles coated with vancomycin-modified polyelectrolyte-cypate complexes (SiO₂-Cy-Van), which is activated by an interesting phenomenon of bacteria-responsive dissociation of the polyelectrolyte from silica nanoparticles. Due to the aggregation of hydrophobic cypate fluorophores on silica nanoparticles to induce ground-state quenching, the SiO₂-Cy-Van nanoprobes are nonfluorescent in aqueous environments. We demonstrate that MRSA can effectively pull out the vancomycin-modified polyelectrolyte-cypate complexes from silica nanoparticles and draw them onto their own surface, changing the state of cypate from off (aggregation) to on (disaggregation) and leading to in vitro MRSA-activated near-infrared fluorescence (NIRF) and photothermal elimination involving bacterial cell wall and membrane disruption. In vivo experiments show that this de novo-designed nanoprobe can selectively enable rapid (4 h postinjection) NIRF imaging with high sensitivity (10⁵ colony-forming units) and efficient photothermal therapy (PTT) of MRSA infections in mice. Remarkably, the SiO₂-Cy-Van nanoprobes can also afford a long-term tracking (16 days) of the development of MRSA infections, allowing real-time estimation of bacterial load in infected tissues and further providing a possible way to monitor the efficacy of antimicrobial treatment. The strategy of bacteria-activated polyelectrolyte dissociation from nanoparticles proposed in this work could also be used as a general method for the design and fabrication of bacteria-responsive functional nanomaterials that offer possibilities to combat drug-resistant bacterial infections.

Recent advances in high-performance fluorescent and bioluminescent RNA imaging probes

RNA plays an important role in life processes. Imaging of messenger RNAs (mRNAs) and micro-RNAs (miRNAs) not only allows us to learn the formation and transcription of mRNAs and the biogenesis of miRNAs involved in various life processes, but also helps in detecting cancer. High-performance RNA imaging probes greatly expand our view of life processes and enhance the cancer detection accuracy. In this review, we summarize the state-of-the-art high-performance RNA imaging probes, including exogenous probes that can image RNA sequences with special modification and endogeneous probes that can directly image endogenous RNAs without special treatment. For each probe, we review its structure and imaging principle in detail. Finally, we summarize the application of mRNA and miRNA imaging probes in studying life processes as well as in detecting cancer. By correlating the structures and principles of various probes with their practical uses, we compare different RNA imaging probes and offer guidance for better utilization of the current imaging probes and the future design of higher-performance RNA imaging probes.

Hybrid Nanoparticle Pyramids for Intracellular Dual MicroRNAs Biosensing and Bioimaging

This study strategically fabricates multifunctional nanopyramids to allow the ultrasensitive quantification of dual microRNAs (miR-203^b and miR-21) in living cells and their responsive bioimaging in vivo. The nanopyramids, composed of Au-Cu₉ S₅ nanoparticles (NPs), upconversion NPs (UCNPs), and Ag₂ S NPs, emit two luminescent signals simultaneously with excitation at 808 nm, arising from the UCNPs at 541 nm in the visible region and from the Ag₂ S NPs at 1227 nm in the second window of near-infrared (NIR-II) region. The upconversion luminescence has a linear relationship with miR-203^b from 0.13 to 54.54 fmol per 10 µg_RNA and a limit of detection (LOD) of 0.09 fmol per 10 µg_RNA , whereas the Ag₂ S NP luminescence has a linear relationship with miR-21 from 0.37 to 43.56 fmol per 10 µg_RNA , with a LOD of 0.23 fmol per 10 µg_RNA . Significantly, this study demonstrates that the nanopyramids can be successfully used for miRs-responsive bioimaging in a tumor-bearing animal model. Furthermore, taking advantage of the photothermal capabilities of pyramids, the tumors can also be eliminated completely. These nanopyramids not only overcome the obstacles in the simultaneous detection of multiple miRs at the cellular level but also provide a cancer theranostic platform in vivo.

A smart ZnO@polydopamine-nucleic acid nanosystem for ultrasensitive live cell mRNA imaging by the target-triggered intracellular self-assembly of active DNAzyme nanostructures

Efficient strategies for the ultrasensitive imaging of gene expression in living cells are essential in chemistry and cell biology. Here, we report a novel and efficient enzyme-free dual signal amplification strategy for live cell mRNA imaging by using a smart nucleic acid hairpin-based nanosystem. This nanosystem consists of a ZnO nanoparticle core, an interlayer of polydopamine and an outer layer of four hairpin DNA (hpDNA) probes. Such a core-shell nanosystem facilitates the cellular uptake of molecular hairpin payloads, protects them from nuclease digestion, and delivers them into the cytoplasm by the acid-triggered dissolution of the ZnO core. In the presence of target mRNA, the released hpDNA probes self-assemble via HCR into wire-shaped active DNAzymes that catalyze the generation of a fluorescence signal. The target-initiated HCR events and DNAzyme cascades offer efficient dual amplification and enable the ultrasensitive detection of mRNA with a femtomolar detection limit. Live cell assays show an intense fluorescence response from a tumor-related biomarker survivin mRNA only in tumor cells untreated with a survivin expression repressor YM155, but not in normal cells. The developed nanosystem provides a potential platform for the amplified imaging of low-abundance disease-related biomarkers in live cells.

Nanozyme-based bio-barcode assay for high sensitive and logic-controlled specific detection of multiple DNAs

Since HCV and HIV share a common transmission path, high sensitive detection of HIV and HCV gene is of significant importance to improve diagnosis accuracy and cure rate at early stage for HIV virus-infected patients. In our investigation, a novel nanozyme-based bio-barcode fluorescence amplified assay is successfully developed for simultaneous detection of HIV and HCV DNAs with excellent sensitivity in an enzyme-free and label-free condition. Here, bimetallic nanoparticles, PtAu_NPs, present outstanding peroxidase-like activity and act as barcode to catalyze oxidation of nonfluorescent substrate of amplex red (AR) into fluorescent resorufin generating stable and sensitive "Turn On" fluorescent output signal, which is for the first time to be integrated with bio-barcode strategy for fluorescence detection DNA. Furthermore, the provided strategy presents excellent specificity and can distinguish single-base mismatched mutant from target DNA. What interesting is that cascaded INHIBIT-OR logic gate is integrated with biosensors for the first time to distinguish individual target DNA from each other under logic function control, which presents great application in development of rapid and intelligent detection.

Mussel-inspired deposition of copper on titanium for bacterial inhibition and enhanced osseointegration in a periprosthetic infection model

Periprosthetic infection represents one of the most devastating complications in orthopedic surgeries.

Antibacterial activity and osseointegration of silver-coated poly(ether ether ketone) prepared using the polydopamine-assisted deposition technique

PEEK-PDA-Ag substrates may be a promising orthopaedic implant material due to the outstanding biocompatibility and antibacterial properties.

Recent progress in nanotechnology for stem cell differentiation, labeling, tracking and therapy

Nanotechnology advancements for stem cell differentiation, labeling, tracking and therapeutic applications in cardiac repair, bone, and liver regeneration are delineated.

Fluorescent Nanocomposite for Visualizing Cross-Talk between MicroRNA-21 and Hydrogen Peroxide in Ischemia-Reperfusion Injury in Live Cells and In Vivo

MicroRNAs (miRNAs) and reactive oxygen species (ROS) are concurrently implicated in heart ischemia-reperfusion (IR) injury. There may exist mutual cross-talk between miRNAs and ROS in cardiac IR injury process. In this study, we developed a novel crown-like silica@polydopamine-DNA-CeO₂ nanocomposite by assembly of silica@polydopamine-DNA1 nanoparticles decorated with satellite CeO₂-DNA2 nanoparticles for detecting and imaging of microRNA-21 (miR-21) and hydrogen peroxide (H₂O₂) in simulated IR injury in living cells and in vivo. The miRNA-21 was found to be regulated by H₂O₂ via PI3K/AKT signaling pathway for the first time in H9C2 cells in simulated ischemia-reperfusion injury. H₂O₂ and miRNA-21 are overproduced during mimicked heart ischemia-reperfusion injury, suggesting that they are closely related to reperfusion injury. All these results reveal that there is definite cross-talk between miR-21 and H₂O₂ in IR injury. The current method can provide a promising strategy to further explore the interplaying roles between ROS and miRNAs in other pathological processes.

Precision combination therapy for triple negative breast cancer via biomimetic polydopamine polymer core-shell nanostructures

Photothermal-based combination therapy using functional nanomaterials shows great promise in eradication of aggressive tumors and improvement of drug sensitivity. The therapeutic efficacy and adverse effects of drug combinations depend on the precise control of timely tumor-localized drug release. Here a polymer-dopamine nanocomposite is designed for combination therapy, thermo-responsive drug release and prevention of uncontrolled drug leakage. The thermo-sensitive co-polymer poly (2-(2-methoxyethoxy) ethyl methacrylate-co-oligo (ethylene glycol) methacrylate)-co-2-(dimethylamino) ethyl methacrylate-b-poly (D, l-lactide-co-glycolide) is constructed into core-shell structured nanoparticles for co-encapsulation of two cytotoxic drugs and absorption of small interfering RNAs against survivin. The drug-loaded nanoparticles are surface-coated with polydopamine which confers the nanoformulation with photothermal activity and protects drugs from burst release. Under tumor-localized laser irradiation, polydopamine generates sufficient heat, resulting in nanoparticle collapse and instant drug release within the tumor. The combination strategy of photothermal, chemo-, and gene therapy leads to triple-negative breast cancer regression, with a decrease in the chemotherapeutic drug dosage to about 1/20 of conventional dose. This study establishes a powerful nanoplatform for precisely controlled combination therapy, with dramatic improvement of therapeutic efficacy and negligible side effects.

Plasmonically Engineered Nanoprobes for Biomedical Applications

The localized surface plasmon resonance of metal nanoparticles is the collective oscillation of electrons on particle surface, induced by incident light, and is a particle composition-, morphology-, and coupling-dependent property. Plasmonic engineering deals with highly precise formation of the targeted nanostructures with targeted plasmonic properties (e.g., electromagnetic field distribution and enhancement) via controlled synthetic, assembling, and atomic/molecular tuning strategies. These plasmonically engineered nanoprobes (PENs) have a variety of unique and beneficial physical, chemical, and biological properties, including optical signal enhancement, catalytic, and local temperature-tuning photothermal properties. In particular, for biomedical applications, there are many useful properties from PENs including LSPR-based sensing, surface-enhanced Raman scattering, metal-enhanced fluorescence, dark-field light-scattering, metal-mediated fluorescence resonance energy transfer, photothermal effect, photodynamic effect, photoacoustic effect, and plasmon-induced circular dichroism. These properties can be utilized for the development of new biotechnologies and biosensing, bioimaging, therapeutic, and theranostic applications in medicine. This Perspective introduces the concept of plasmonic engineering in designing and synthesizing PENs for biomedical applications, gives recent examples of biomedically functional PENs, and discusses the issues and future prospects of PENs for practical applications in bioscience, biotechnology, and medicine.

New Generation of Gold Nanoshell-Coated Esophageal Stent: Preparation and Biomedical Applications

Esophageal cancer is one of the six most common cancers in the world, constituting ∼7% of the gastrointestinal cancers. Esophageal stents can be inserted into the esophagus to open the pathway as a palliative treatment for advanced esophageal cancer. For the treatment of esophageal cancer, a series of anticancer drug-loaded stents such as paclitaxel or 5-fluorouracil/esophageal stent combinations have been prepared by covering a nitinol stent with a polymer or hydrogel shell. For the first time, we developed a gold nanoshell (AuNS)-coated stent with high photothermal efficiency and used in the repetitive photothermal therapy of esophageal cancer. The functionalized stent was prepared by using surface-coated polydopamine as the Au³⁺ anchor and template. The thickness of the AuNS can be easily adjusted by controlling the reaction time and amount of Au³⁺. The AuNS-coated stent efficiently increased the temperature of pork and porcine intestines irradiated with a near-infrared (NIR) laser. The deep penetration of the NIR laser and excellent stability of the stent provide opportunity for the clinical applications of the newly functionalized stent. In vitro toxicity experiments showed excellent biocompatibility and safety of this device. Compared with bare metal stent, AuNS-modified stent exhibits great potential to open the duct passageway and suppress tumor growth in future clinical applications.

Efficient delivery of C/EBP beta gene into human mesenchymal stem cells via polyethylenimine-coated gold nanoparticles enhances adipogenic differentiation

The controlled differentiation of stem cells via the delivery of specific genes encoding appropriate differentiation factors may provide useful models for regenerative medicine and aid in developing therapies for human patients. However, the majority of non-viral vectors are not efficient enough to manipulate difficult-to-transfect adult human stem cells in vitro. Herein, we report the first use of 25 kDa branched polyethylenimine-entrapped gold nanoparticles (AuPEINPs) and covalently bound polyethylenimine-gold nanoparticles (AuMUAPEINPs) as carriers for efficient gene delivery into human mesenchymal stem cells (hMSCs). We determined a functional application of these nanoparticles by transfecting hMSCs with the C/EBP beta gene, fused to EGFP, to induce adipogenic differentiation. Transfection efficacy with AuPEINPs and AuMUAPEINPs was 52.3% and 40.7%, respectively, which was 2.48 and 1.93 times higher than that by using Lipofectamine 2000. Luciferase assay results also demonstrated improved gene transfection efficiency of AuPEINPs/AuMUAPEINPs over Lipofectamine 2000 and polyethylenimine. Overexpression of exogenous C/EBP beta significantly enhanced adipogenesis in hMSCs as indicated by both of Oil Red O staining and mRNA expression analyses. Nanoparticle/DNA complexes exhibited favorable cytocompatibility in hMSCs. Taken together, AuPEINPs and AuMUAPEINPs potentially represent safe and highly efficient vehicles for gene delivery to control hMSC differentiation and for therapeutic gene delivery applications.

Biologically Inspired Polydopamine Capped Gold Nanorods for Drug Delivery and Light-Mediated Cancer Therapy

Multifunctional drug delivery and combined multimodal therapy strategies are very promising in tumor theranostic applications. In this work, a simple and versatile nanoplatform based on biologically inspired polydopamine capped gold nanorods (GNR-PDA) is developed. Dopamine, a well-known neurotransmitter associated with many neuronal disorders, can undergo self-polymerization on the surface of GNRs to form a stable PDA shell. Its unique molecular adsorption property, as well as its high chemical stability and biocompatibility, facilitate GNR-PDA as an ideal candidate for drug delivery. Methylene blue (MB) and doxorubicin (DOX) are directly adsorbed on GNR-PDA via electrostatic and/or π-π stacking interactions, forming GNR-PDA-MB and GNR-PDA-DOX nanocomposites, respectively. The GNR-PDA-MB can generate reactive oxygen species (ROS, from MB) or hyperthermia (from GNR-PDA) with high efficiency under deep-red/NIR laser irradiation, while the GNR-PDA-DOX exhibits light-enhanced drug release under NIR laser irradiation. The combined dual-modal light-mediated therapy, by using GNR-PDA-MB [photodynamic/photothermal therapy (PDT/PTT)] and GNR-PDA-DOX (Chemo/PTT), is carried out and shows remarkable cancer cell killing efficiency in vitro and significant suppression of tumor growth in vivo, which are much more distinct than any single-modal therapy strategy. Our work illustrates that GNR-PDA could be a promising nanoplatform for multifunctional drug delivery and multimodal tumor theranostics in the future.

Polydopamine Nanotubes as an Effective Fluorescent Quencher for Highly Sensitive and Selective Detection of Biomolecules Assisted with Exonuclease III Amplification

In this work, the effective fluorescence quenching ability of polydopamine nanotubes (PDANTs) toward various fluorescent dyes was studied and further applied to fluorescent biosensing for the first time. The PDANTs could quench the fluorophores with different emission frequencies, aminomethylcoumarin acetate (AMCA), 6-carboxyfluorescein (FAM), 6-carboxytetramethylrhodamine (TAMRA), and Cy5. All the quenching efficiencies reached to more than 97%. Taking advantage of PDANTs' different affinities toward ssDNA and dsDNA and utilizing the complex of FAM-labeled ssDNA and PDANTs as a sensing platform, we achieved highly sensitive and selective detection of human immunodeficiency virus (HIV) DNA and adenosine triphosphate (ATP) assisted with Exonuclease III amplification. The limits of detection (LODs) of HIV DNA and ATP reached to 3.5 pM and 150 nM, respectively, which were all lower than that of previous nanoquenchers with Exo III amplification, and the platform also presented good applicability in biological samples. Fluorescent sensing applications of this nanotube enlightened other targets detection based upon it and enriched the building blocks of fluorescent sensing platforms. This polydopamine nanotube also possesses excellent biocompatibility and biodegradability, which is suitable for future drug delivery, cell imaging, and other biological applications.