Cationic oligofluorene-substituted polyhedral oligomeric silsesquioxane as light-harvesting unimolecular nanoparticle for fluorescence amplification in cellular imaging

Conjugated Oligoelectrolyte with DNA Affinity for Enhanced Nuclear Imaging and Precise DNA Quantification

Precise DNA quantification and nuclear imaging are pivotal for clinical testing, pathological diagnosis, and drug development. The detection and localization of mitochondrial DNA serve as crucial indicators of cellular health. We introduce a novel conjugated oligoelectrolyte (COE) molecule, COE-S3, featuring a planar backbone composed of three benzene rings and terminal side chains. This unique amphiphilic structure endows COE-S3 with exceptional water solubility, a high quantum yield of 0.79, and a significant fluorescence Stokes shift (λex = 366 nm, λem = 476 nm), alongside a specific fluorescence response to DNA. The fluorescence intensity correlates proportionally with DNA concentration. COE-S3 interacts with double-stranded DNA (dsDNA) through an intercalation binding mode, exhibiting a binding constant (K) of 1.32 × 106 M-1. Its amphiphilic nature and strong DNA affinity facilitate its localization within mitochondria in living cells and nuclei in apoptotic cells. Remarkably, within 30 min of COE-S3 staining, cell vitality can be discerned through real-time nuclear fluorescence imaging of apoptotic cells. COE-S3's high DNA selectivity enables quantitative intracellular DNA analysis, providing insights into cell proliferation, differentiation, and growth. Our findings underscore COE-S3, with its strategically designed, shortened planar backbone, as a promising intercalative probe for DNA quantification and nuclear imaging.

Chromium(III)-Catalyzed Desymmetrization of meso-Epoxides via Remote Stereocontrol: Synthesis of Chiral Fluorenes Bearing All-Carbon Quaternary Stereocenters

An asymmetric desymmetrization of fluorene-derived meso-epoxides is disclosed for the construction of chiral fluorenes bearing an all-carbon quaternary stereocenter at C9. This desymmetrization is catalyzed by a chiral (salen)CrIII complex via remote stereocontrol, producing diverse chiral fluorenes with excellent yields and stereoselectivity. The practicality of this protocol was demonstrated through the transformation of the obtained products to some intriguing enantioenriched polymerizable monomers.

Functional Diversity in Radiolabeled Nanoceramics and Related Biomaterials for the Multimodal Imaging of Tumors

Nanotechnology advances have the potential to assist toward the earlier detection of diseases, giving increased accuracy for diagnosis and helping to personalize treatments, especially in the case of noncommunicative diseases (NCDs) such as cancer. The main advantage of nanoparticles, the scaffolds underpinning nanomedicine, is their potential to present multifunctionality: synthetic nanoplatforms for nanomedicines can be tailored to support a range of biomedical imaging modalities of relevance for clinical practice, such as, for example, optical imaging, computed tomography (CT), magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT), and positron emission tomography (PET). A single nanoparticle has the potential to incorporate myriads of contrast agent units or imaging tracers, encapsulate, and/or be conjugated to different combinations of imaging tags, thus providing the means for multimodality diagnostic methods. These arrangements have been shown to provide significant improvements to the signal-to-noise ratios that may be obtained by molecular imaging techniques, for example, in PET diagnostic imaging with nanomaterials versus the cases when molecular species are involved as radiotracers. We surveyed some of the main discoveries in the simultaneous incorporation of nanoparticulate materials and imaging agents within highly kinetically stable radio-nanomaterials as potential tracers with (pre)clinical potential. Diversity in function and new developments toward synthesis, radiolabeling, and microscopy investigations are explored, and preclinical applications in molecular imaging are highlighted. The emphasis is on the biocompatible materials at the forefront of the main preclinical developments, e.g., nanoceramics and liposome-based constructs, which have driven the evolution of diagnostic radio-nanomedicines over the past decade.

A decacationic ferrocene-based metallostar

Decacationic metallostars have been prepared by the reaction of permercurated ferrocene FeC₁₀(HgO₂CCF₃)₁₀ with superacidic (C₅F₅NH)(SbF₆) (pK _a = -11 estimated in H₂O) in multigram scale. In the resulting compound, [FeC₁₀Hg₁₀(NC₅F₅) _n ][SbF₆]₁₀, the labile pentafluoropyridine ligands are readily displaced by acetonitrile (MeCN) or tetrahydrothiophene (THT). In the X-ray structure of [FeC₁₀Hg₁₀(THT)₁₀][SbF₆]₁₀·24 MeCN no cation-anion contacts between mercury and fluorine were observed. Moreover, cyclic voltammetry measurements of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ and [FeC₁₀(Hg(THT))₁₀]¹⁰⁺ revealed a (quasi)reversible one-electron oxidation of Fe(ii) to Fe(iii). From the reaction of [FeC₁₀(Hg(MeCN))₁₀]¹⁰⁺ with MoF₆ as oxidant the ferrocenium cation [FeC₁₀(Hg(MeCN))₁₀]¹¹⁺ was obtained and characterized via single crystal XRD. These electrophilic metallostars are promising potential building blocks for the synthesis of dendritic architectures containing a robust, tenfold functionalized ferrocene core.

Synchronous Imaging in Golgi Apparatus and Lysosome Enabled by Amphiphilic Calixarene-Based Artificial Light-Harvesting Systems

Artificial supramolecular light-harvesting systems have expanded various properties on photoluminescence, enabling promising applications on cell imaging, especially for imaging in organelles. Supramolecular light-harvesting systems have been used for imaging in some organelles such as lysosome, Golgi apparatus, and mitochondrion, but developing a supramolecular light-harvesting platform for imaging two organelles synchronously still remains a great challenge. Here, we report a series of lower-rim dodecyl-modified sulfonato-calix[4]arene-mediated supramolecular light-harvesting platforms for efficient light-harvesting from three naphthalene diphenylvinylpyridiniums containing acceptors, Nile Red, and Nile Blue. All of the constructed supramolecular light-harvesting systems possess high light-harvesting efficiency. Furthermore, when the two acceptors are loaded simultaneously in a single light-harvesting donor system for imaging in human prostate cancer cells, organelle imaging in lysosome and Golgi apparatus can be realized at the same time with distinctive wavelength emission. Nile Red receives the light-harvesting energy from the donors, reaching orange emissions (625 nm) in lysosome while Nile Blue shows a near-infrared light-harvesting emission at 675 nm in Golgi apparatus in the same cells. Thus, the light harvesting system provides a pathway for synchronously efficient cell imaging in two distinct organelles with a single type of photoluminescent supramolecular nanoparticles.

Use of Polyhedral Oligomeric Silsesquioxane (POSS) in Drug Delivery, Photodynamic Therapy and Bioimaging

Polyhedral oligomeric silsesquioxanes (POSS) have attracted considerable attention in the design of novel organic-inorganic hybrid materials with high performance capabilities. Features such as their well-defined nanoscale structure, chemical tunability, and biocompatibility make POSS an ideal building block to fabricate hybrid materials for biomedical applications. This review highlights recent advances in the application of POSS-based hybrid materials, with particular emphasis on drug delivery, photodynamic therapy and bioimaging. The design and synthesis of POSS-based materials is described, along with the current methods for controlling their chemical functionalization for biomedical applications. We summarize the advantages of using POSS for several drug delivery applications. We also describe the current progress on using POSS-based materials to improve photodynamic therapies. The use of POSS for delivery of contrast agents or as a passivating agent for nanoprobes is also summarized. We envision that POSS-based hybrid materials have great potential for a variety of biomedical applications including drug delivery, photodynamic therapy and bioimaging.

Zeptomole Imaging of Cytosolic MicroRNA Cancer Biomarkers with A Light-Controlled Nanoantenna

Detecting and quantifying intracellular microRNAs (miRNAs) are a critical step in resolving a cancer diagnostic and resolving the ensemble of gene products that orchestrate the living state of cells. However, the nanoprobe for detecting low abundance miRNAs in cell cytosol is restricted by either the "one-to-one" signal-trigger model or difficulty for cytosol delivery. To address these challenges, we designed a light-harvesting nanoantenna-based nanoprobe, which directs excitation energy to a single molecule to sensitively detect cytosolic miRNA. With light irradiation, the light-harvesting nanoantenna effectively disrupted lysosomal structures by generation of reactive oxygen species, substantially achieved cytosol delivery. The nanoantenna containing > 4000 donor dyes can efficiently transfer excitation energy to one or two acceptors with 99% efficiency, leading to unprecedented signal amplification and biosensing sensitivity. The designed nanoantenna can quantify cytosolic miR-210 at zeptomolar level. The fluorescence lifetime of the donor exhibited good relationship with miR-210 concentration in the range of 0.032 to 2.97 amol/ngRNA. The zeptomole sensitivity of nanoantenna provides accurate bioimaging of miR-210 both in multiple cell lines and in vivo assay, which creates a pathway for the creation of miRNA toolbox for quantitative epigenetics and personalized medicine.

Study on the Biosensor Based on Biomimetic PDA Vesicles Fluorescence Resonance Energy Transfer for the Determination of Ovarian Cancer Marker miRNA-21

In recent years, more and more research is being conducted on microRNAs and their involvement in the regulation of autophagy phagocytosis which is closely related to tumor growth. MicroRNA-21 is a kind of small RNA that can regulate gene expression and plays a significant role in autophagy of tumor cells. But the detection of microRNAs had always been a problem in the field of biological analysis. In this study, we designed a new fluorescent sensor for the detection of miRNA-21. The sensor was based on the successful signal reporting by E36-encapsulated vesicles and the specific interaction between E36 and miRNA-21. In the presence of miRNA, the E36/miRNA-21 complex formed and served as a donor molecule inside the acceptor PDA vesicles to amplify the fluorescence through FRET. Additionally, the sensor was applied to detect miRNA-21 in complex biological samples with satisfactory results.

Luminescent Neutral Cyclometalated Iridium(III) Complexes Featuring a Cubic Polyhedral Oligomeric Silsesquioxane for Lipid Droplet Imaging and Photocytotoxic Applications

New neutral iridium(III) complexes featuring a cubic polyhedral oligomeric silsesquioxane (POSS) unit, [Ir(N^∧C)₂(L1-POSS)] [HN^∧C = 2-phenylpyridine (Hppy; 1), 2-phenylbenzothioazole (Hbt; 2), and 2-(1-naphthyl)benzothiazole (Hbsn; 3); L1-POSS = (E)-4-[(2-hydroxybenzylidene)amino]benzyl 3-heptakis(isobutyl)POSS-propyl carbamate], were designed and synthesized. Their POSS-free counterparts, [Ir(N^∧C)₂(L1)] [L1 = (E)-N-(4-hydroxymethylphenyl)-1-(2-hydroxyphenyl)methanimine; HN^∧C = Hppy (1a), Hbt (2a), and Hbsn (3a)], and the poly(ethylene glycol) (PEG) derivatives [Ir(N^∧C)₂(L1-PEG)] [L1-PEG = (E)-4-[(2-hydroxybenzylidene)amino]benzyl 3-[2-[ω-methoxypoly(1-oxapropyl)]ethyl]carbamate; HN^∧C = Hppy (1b), Hbt (2b), and Hbsn (3b)] were also prepared. The photophysical, photochemical, and biological properties of the POSS complexes were compared with those of their POSS-free and PEG-modified counterparts. Upon irradiation, all of these complexes displayed orange-to-red emission and long emission lifetimes under ambient conditions. The bsn complexes 3, 3a, and 3b exhibited the highest singlet oxygen (¹O₂) generation quantum yields (Φ_Δ = 0.85-0.86) in aerated CH₃CN. Laser-scanning confocal microscopy images revealed that complexes 1-3 and 1a-3a showed exclusive lipid-droplet staining upon cellular uptake, while the PEG derivatives 1b-3b displayed lysosomal localization. Complex 3 was utilized to study various lipid-droplet-related biological events including lipid-droplet accumulation under oleic acid stimulation, the movement of lipid droplets, and preadipocyte differentiation. Notably, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays indicated that the ppy complexes 1 and 1b and the bt complexes 2 and 2b were noncytotoxic both in the dark and upon irradiation at 450 nm for 5 min (IC₅₀ > 200 μM), while the bsn complexes 3, 3a, and 3b showed low dark cytotoxicity (IC₅₀ = 52.9 to >200 μM) and high photocytotoxicity (IC₅₀ = 1.1-5.3 μM). The cellular uptake, internalization mechanisms, and cell death pathways of these complexes were also investigated. This work not only offers promising luminescent probes for lipid droplets through the structural modification of iridium(III) complexes but also paves the way to the construction of new reagents for theranostics.

Thermally Stable Fluorogenic Zn(II) Sensor Based on a Bis(benzimidazole)pyridine-Linked Phenyl-Silsesquioxane Polymer

A 2,6-bis(2-benzimidazolyl) pyridine-linked silsesquioxane-based semi-branched polymer was synthesized, and its photophysical and metal-sensing properties have been investigated. The polymer is thermally stable up to 285 °C and emits blue in both solid and solution state. The emission of the polymer is sensitive to pH and is gradually decreased and quenched upon protonation of the linkers. The initial emission color is recoverable upon deprotonation with triethylamine. The polymer also shows unique spectroscopic properties in both absorption and emission upon long-term UV irradiation, with red-shifted absorption and emission not present in a simple blended system of phenylsilsesquioxane and linker, suggesting that a long-lived energy transfer or charge separated state is present. In addition, the polymer acts as a fluorescence shift sensor for Zn(II) ions, with red shifts observed from 464 to 528 nm, and reversible binding by the introduction of a competitive ligand such as tetrahydrofuran. The ion sensing mechanism can differentiate Zn(II) from Cd(II) by fluorescence color shifts, which is unique because they are in the same group of the periodic table and possess similar chemical properties. Finally, the polymer system embedded in a paper strip acts as a fluorescent chemosensor for Zn(II) ions in solution, showing its potential as a solid phase ion extractor.

Precisely Defined Conjugated Oligoelectrolytes for Biosensing and Therapeutics

Conjugated oligoelectrolytes (COEs) are a relatively new class of synthetic organic molecules with, as of yet, untapped potential for use in organic optoelectronic devices and bioelectronic systems. COEs also offer a novel molecular approach to biosensing, bioimaging, and disease therapy. Substantial progress has been made in the past decade at the intersection of chemistry, materials science, and the biological sciences developing COEs and their polymer analogues, namely, conjugated polyelectrolytes (CPEs), into synthetic systems with biological and biomedical utility. CPEs have traditionally attracted more attention in arenas of sensing, imaging, and therapy. However, the precisely defined molecular structures and interactions of COEs offer potential key advantages over CPEs, including higher reliability and fluorescence quantum efficiency, larger diversity of subcellular targeting strategies, and improved selectivity to biomolecules. Here, the unique-and sometimes overlooked-properties of COEs are discussed and the noticeable progress in their use for biological sensing, imaging, and therapy is reviewed.

Applications of nanoparticles in biomedical imaging

An urgent need for early detection and diagnosis of diseases continuously pushes the advancements of imaging modalities and contrast agents. Current challenges remain for fast and detailed imaging of tissue microstructures and lesion characterization that could be achieved via development of nontoxic contrast agents with longer circulation time. Nanoparticle technology offers this possibility. Here, we review nanoparticle-based contrast agents employed in most common biomedical imaging modalities, including fluorescence imaging, MRI, CT, US, PET and SPECT, addressing their structure related features, advantages and limitations. Furthermore, their applications in each imaging modality are also reviewed using commonly studied examples. Future research will investigate multifunctional nanoplatforms to address safety, efficacy and theranostic capabilities. Nanoparticles as imaging contrast agents have promise to greatly benefit clinical practice.

A review on core-shell structured unimolecular nanoparticles for biomedical applications

Polymeric unimolecular nanoparticles (NPs) exhibiting a core-shell structure and formed by a single multi-arm molecule containing only covalent bonds have attracted increasing attention for numerous biomedical applications. This unique single-molecular architecture provides the unimolecular NP with superior stability both in vitro and in vivo, a high drug loading capacity, as well as versatile surface chemistry, thereby making it a desirable nanoplatform for therapeutic and diagnostic applications. In this review, we surveyed the architecture of various types of polymeric unimolecular NPs, including water-dispersible unimolecular micelles and water-soluble unimolecular NPs used for the delivery of hydrophobic and hydrophilic agents, respectively, as well as their diverse biomedical applications. Future opportunities and challenges of unimolecular NPs were also briefly discussed.

Facile synthesis and bridgehead-functionalization of bicyclo[3.3.3]pentasiloxanes

Various bicyclo[3.3.3]pentasiloxanes (BPSO) were successfully synthesized via regioselective functionalization at the bridgehead positions.

Photosensitizer (PS)/polyhedral oligomeric silsesquioxane (POSS)-crosslinked nanohybrids for enhanced imaging-guided photodynamic cancer therapy

Photodynamic therapy (PDT) has drawn extensive attention as a promising cancer treatment modality. However, most PDT nanoagents suffer from insufficient drug loading capacity, a severe self-quenching effect, premature release of drugs and/or potential toxicity. Herein, we rationally designed an inorganic-organic nanohybrid with high drug loading capacity and superior chemical stability for enhanced PDT. Polyhedral oligomeric silsesquioxane (POSS), an amine-containing cage-shaped building block, was crosslinked with chlorin e6 (Ce6), a carboxyl-containing photosensitizer, via the amine-carboxyl reaction. Polyethylene glycol (PEG) polymers were further modified on the surface of the nanoparticle to improve the aqueous dispersibility and prolong the circulation time of the final nanoconstruct (POSS-Ce6-PEG). The as-prepared POSS-Ce6-PEG has a considerably high loading rate of Ce6 (19.8 wt%) with desirable fluorescence emission and singlet oxygen generation. Besides, in vitro experiments revealed that the nanoagent exhibited enhanced cellular uptake and a preferred intracellular accumulation within mitochondria and the endoplasmic reticulum, resulting in high anticancer efficiency under light irradiation. Furthermore, in vivo imaging-guided PDT was also successfully achieved, showing the effective tumor targeting and ablation ability of POSS-Ce6-PEG. More importantly, the nanoagent possesses negligible dark cytotoxicity and systemic side effects. Therefore, POSS-Ce6-PEG as an eligible PDT theranostic agent holds great potential in clinical applications.

Controlling photophysical properties of ultrasmall conjugated polymer nanoparticles through polymer chain packing

Applications of conjugated polymer nanoparticles (Pdots) for imaging and sensing depend on their size, fluorescence brightness and intraparticle energy transfer. The molecular design of conjugated polymers (CPs) has been the main focus of the development of Pdots. Here we demonstrate that proper control of the physical interactions between the chains is as critical as the molecular design. The unique design of twisted CPs and fine-tuning of the reprecipitation conditions allow us to fabricate ultrasmall (3.0–4.5 nm) Pdots with excellent photostability. Extensive photophysical and structural characterization reveals the essential role played by the packing of the polymer chains in the particles in the intraparticle spatial alignment of the emitting sites, which regulate the fluorescence brightness and the intraparticle energy migration efficiency. Our findings enhance understanding of the relationship between chain interactions and the photophysical properties of CP nanomaterials, providing a framework for designing and fabricating functional Pdots for imaging applications.

Synthesis of small conjugated polymer nanoparticles (Pdots) with bright and stable fluorescence is an active challenge. Here, the authors introduce a strategy to fabricate ultrasmall Pdots with high fluorescence intensity by using twisted, rather than planar, conjugated polymers, lending new insight into the molecular design of Pdots.

A hybrid organic–inorganic three-dimensional cathode interfacial material for organic solar cells

An alcohol soluble hybrid organic–inorganic three-dimensional material POSS-FN has been synthesized and assessed as a cathode interlayer within organic solar cells consisting of a PBDT-BT:PC₆₁BM bulk heterojunction.

Dual-Color Fluorescence Imaging of Magnetic Nanoparticles in Live Cancer Cells Using Conjugated Polymer Probes

Rapid growth in biological applications of nanomaterials brings about pressing needs for exploring nanomaterial-cell interactions. Cationic blue-emissive and anionic green-emissive conjugated polymers are applied as dual-color fluorescence probes to the surface of negatively charged magnetic nanoparticles through sequentially electrostatic adsorption. These conjugated polymers have large extinction coefficients and high fluorescence quantum yield (82% for PFN and 62% for ThPFS). Thereby, one can visualize trace amount (2.7 μg/mL) of fluorescence-labeled nanoparticles within cancer cells by confocal laser scanning microscopy. Fluorescence labeling by the conjugated polymers is also validated for quantitative determination of the internalized nanoparticles in each individual cell by flow cytometry analysis. Extensive overlap of blue and green fluorescence signals in the cytoplasm indicates that both conjugated polymer probes tightly bind to the surface of the nanoparticles during cellular internalization. The highly charged and fluorescence-labeled nanoparticles non-specifically bind to the cell membranes, followed by cellular uptake through endocytosis. The nanoparticles form aggregates inside endosomes, which yields a punctuated staining pattern. Cellular internalization of the nanoparticles is dependent on the dosage and time. Uptake efficiency can be enhanced three-fold by application of an external magnetic field. The nanoparticles are low cytotoxicity and suitable for simultaneously noninvasive fluorescence and magnetic resonance imaging application.

Dual functional and multiple substituted fluorescent star-shaped POSS for a 1 + 1 > 2 explosive vapour detection

A dual functional and multiple substituted fluorescent star-shaped POSS was synthesized for highly efficient NG and TNT vapor detection.

Lanthanide complex-functionalized polyhedral oligomeric silsesquioxane with multicolor emission covered from 450 nm to 1700 nm

Six new hybrid materials covalently linking ternary lanthanide complexes to POSS were prepared, and the luminescent properties were investigated in detail.

Branched Polyhedral Oligomeric Silsesquioxane Nanoparticles Prepared via Strain-Promoted 1,3-Dipolar Cycloadditions

Conjugation of small organic molecules and polymers to polyhedral oligosilsesquioxane (POSS) cores results in novel hybrid materials with unique physical characteristics. We report here an approach in which star-shaped organic-inorganic scaffolds bearing eight cyclooctyne moieties can be rapidly functionalized via strain-promoted azide-alkyne cycloaddition (SPAAC) to synthesize a series of nearly monodisperse branched core-shell nanoparticles with hydrophobic POSS cores and hydrophilic arms. We established that SPAAC is a robust method for POSS core octafunctionalization with the reaction rate constant of 1.9 × 10(-2) M(-1) s(-1). Functionalization with poly(ethylene glycol) (PEG) azide, fluorescein azide, and unprotected lactose azide gave conjugates which represent different classes of compounds: polymer conjugates, fluorescent dots, and bioconjugates. These resulting hybrid compounds were preliminarily tested for their ability to self-assemble in solution and at the air-water interface. We observed the formation of robust smooth Langmuir monolayers with diverse morphologies. We found that polar lactose moieties are completely submerged into the subphase whereas the relatively hydrophobic fluorescein arms had extended conformation at the interface, and PEG arms were partially submerged. Finally, we observed the formation of stable micelles with sizes between 70 and 160 nm in aqueous solutions with size and morphology of the structures dependent on the molecular weight and the type of the peripheral hydrophilic moieties.

Construction and electronic properties of carbon nanotube hybrids with conjugated cubic silsesquioxane

Hierarchical zero-dimensional cubic silsesquioxane/one-dimensional SWNT hybrids provided excellent charge transfer and synergistic effects compared to both SWNTs and OASQ.

Star-shaped molecules with polyhedral oligomeric silsesquioxane core and azobenzene dye arms

We synthesized a series of hybrid nanomaterials combining organic dyes with polyhedral oligomeric silsesquioxanes (POSS) based on three different azobenzenes: monoazobenzene (4-phenylazophenol), bis-azobenzene (Disperse Yellow 7 and Fast Garnet derivative), and push-pull azobenzene (Disperse Red 1) via hydrosilylation coupling. The azo-functionalized POSS compounds possess high thermal stability, and their branched architecture resulted in effective suppression of molecular aggregation and allowed for direct imaging of individual dye-POSS structures with expected molecular dimensions. Stable, uniform, smooth, and ultrathin nanocomposite films with mixed silica-organic composition and relatively low refractive indices can be fabricated from all azo-POSS branched conjugates. Finally, the photoisomerization behavior of POSS-conjugated 4-phenylazophenol was investigated in solution as well as in ultrathin nanocomposite film. We found that conjugation to POSS core did not affect the kinetics of trans-cis photoisomerization and thermal cis-trans relaxation. Furthermore, rapid and reversible photoisomerization was observed in azo-POSS nanocomposite films. We suggest that the highly stable branched azo-POSS conjugates with high dye grafting density described here can be considered for nanometer-sized photoswitches, active layer material with optical-limiting properties, and a medium with photoinduced anisotropy for optical storage.

Two-photon fluorescent Bombyx mori silk by molecular recognition functionalization

Two-photon fluorescent (TPF) Bombyx mori silk fibers were acquired for bioimaging by molecular recognition functionalization.

Multifunctional non-viral delivery systems based on conjugated polymers

Multifunctional nanomaterials with simultaneous therapeutic and imaging functions explore new strategies for the treatment of various diseases. Conjugated polymers (CPs) are considered as novel candidates to serve as multifunctional delivery systems due to their high fluorescence quantum yield, good photostability, and low cytotoxicity. Highly sensitive sensing and imaging properties of CPs are well reviewed, while the applications of CPs as delivery systems are rarely covered. This feature article mainly focuses on CP-based multifunctional non-viral delivery systems for drug, protein, gene, and cell delivery. Promising directions for the further development of CP-based delivery systems are also discussed.

Fluorescence bioimaging with conjugated polyelectrolytes

This review summarizes the recent developments in fluorescent conjugated polyelectrolytes (CPEs) in bioimaging. The CPEs discussed include linear-, hyperbranched-, and polyhedral oligomeric silsesquioxanes (POSS)-based derivatives. Originating from their special optical properties, good photostability, low cytotoxicity, ease of bioconjugation and tuneable size, CPEs have shown wide applications in in vitro and in vivo protein and cell imaging, drug tracking and gene delivery. Moreover, some CPEs also possess antibacterial and anticancer characteristics as well as apoptosis imaging functions. Finally, this review discusses the future outlook of CPEs in bioimaging applications.

Silver nanocube-enhanced far-red/near-infrared fluorescence of conjugated polyelectrolyte for cellular imaging

We present the study of silver nanocube (Ag NC)-enhanced fluorescence of a cationic conjugated polyelectrolyte (CPE) for far-red/near-infrared fluorescence cell imaging. Layer-by-layer self-assembly of polyelectrolytes on 78 nm Ag NCs is used to control CPE-metal distance and its effect on CPE fluorescence. The highest fluorescence enhancement factor (FEF) is obtained for Ag NCs with two bilayers, corresponding to a CPE-metal spacer thickness of ~6 nm. At the optimal excitation wavelength, the FEF is 13.8 with respect to the control silica nanoparticles (NPs). The fluorescent NPs are further used for cellular imaging studies. The CPE-loaded Ag NCs with two bilayers exhibit excellent image contrast, superior to the control of CPE-silica NP at a similar uptake efficiency. The viability test indicates low cytotoxicity of the CPE-loaded Ag NCs, rendering them as promising cell imaging agents.

Fluorescence in nanobiotechnology: sophisticated fluorophores for novel applications

Nanobiotechnology is one of the fastest growing and broadest-ranged interdisciplinary subfields of the nanosciences. Countless hybrid bio-inorganic composites are currently being pursued for various uses, including sensors for medical and diagnostic applications, light- and energy-harvesting devices, along with multifunctional architectures for electronics and advanced drug-delivery. Although many disparate biological and nanoscale materials will ultimately be utilized as the functional building blocks to create these devices, a common element found among a large proportion is that they exert or interact with light. Clearly continuing development will rely heavily on incorporating many different types of fluorophores into these composite materials. This review covers the growing utility of different classes of fluorophores in nanobiotechnology, from both a photophysical and a chemical perspective. For each major structural or functional class of fluorescent probe, several representative applications are provided, and the necessary technological background for acquiring the desired nano-bioanalytical information are presented.

DNA-templated silver nanoclusters-graphene oxide nanohybrid materials: a platform for label-free and sensitive fluorescence turn-on detection of multiple nucleic acid targets

In this study, we develop an efficient method for multiple DNA detection by exploring silver nanoclusters (AgNCs)-graphene oxide (GO) nanohybrid materials. Because of the extraordinarily high quenching efficiency of GO, the ssDNA-AgNCs probe exhibits minimal background fluorescence, while strong emission is observed when it forms a double helix with the specific target DNA, leading to a high signal-to-background ratio. Therefore the AgNCs-GO nanohybrid materials can be successfully applied for DNA detection. The system described here exhibits not only high sensitivity with a detection limit of 1 nM, but also an excellent differentiation ability for single-base mismatched sequences. In addition, by exploring AgNCs as signal reporters and GO as the nanoquencher, this approach avoids labeling the probe DNA or target DNA, which offers the advantages of simplicity and cost efficiency. Moreover, the large planar surface of GO allows adsorption of different DNA-AgNCs probes, each with a distinct emission, leading to a multicolor sensor for the detection of multiple DNA targets in the same solution.