Carrier capability of halloysite nanotubes for the intracellular delivery of antisense PNA targeting mRNA of neuroglobin gene.

Peptide nucleic acid (PNA) is a DNA mimic that shows good stability against nucleases and proteases, forming strongly recognized complementary strands of DNA and RNA. However, due to its feeble ability to cross the cellular membrane, PNA activity and its targeting gene action is limited. Halloysite nanotubes (HNTs) are a natural and low-cost aluminosilicate clay.

Photoactivatable Fluorophores for Bioimaging Applications.

Photoactivatable fluorophores provide the opportunity to switch fluorescence on exclusively in a selected area within a sample of interest at a precise interval of time. Such a level of spatiotemporal fluorescence control enables the implementation of imaging schemes to monitor dynamic events in real time and visualize structural features with nanometer resolution. These transformative imaging methods are contributing fundamental insights on diverse cellular processes with profound implications in biology and medicine.

Photoactivatable BODIPYs for Live-Cell PALM.

Photoactivated localization microscopy (PALM) relies on fluorescence photoactivation and single-molecule localization to overcome optical diffraction and reconstruct images of biological samples with spatial resolution at the nanoscale. The implementation of this subdiffraction imaging method, however, requires fluorescent probes with photochemical and photophysical properties specifically engineered to enable the localization of single photoactivated molecules with nanometer precision. The synthetic versatility and outstanding photophysical properties of the borondipyrromethene (BODIPY) chromophore are ideally suited to satisfy these stringent requirements.

Spectroscopic single-molecule localization microscopy: applications and prospective.

Single-molecule localization microscopy (SMLM) breaks the optical diffraction limit by numerically localizing sparse fluorescence emitters to achieve super-resolution imaging. Spectroscopic SMLM or sSMLM further allows simultaneous spectroscopy and super-resolution imaging of fluorescence molecules. Hence, sSMLM can extract spectral features with single-molecule sensitivity, higher precision, and higher multiplexity than traditional multicolor microscopy modalities.

Exploring the cellular uptake of hectorite clay mineral and its drug carrier capabilities.

In the last years, the use of clay minerals for pharmaceutical purposes has increased due to their interesting properties. Hectorite (Ht) is a clay belonging to the smectite group which has attracted attention for applications in biology, tissue engineering and as drug carrier and delivery system. However, the mechanisms involved in Ht cellular uptake and transport into cells, are still unclear.

Nanocarrier based on halloysite and fluorescent probe for intracellular delivery of peptide nucleic acids.

The development of systems able to deliver genetic material into a target site is a challenge for modern medicine. Single-stranded peptide nucleic acids have attracted attention as promising therapeutic molecules for diagnostic and gene therapy. However, their poor cell membrane permeability represents a drawback for biomedical applications.

Fluorescence Switching for Temperature Sensing in Water.

A water-soluble thermochromic molecular switch with spectrally resolved fluorescence in its two interconvertible states can be assembled in three synthetic steps by integrating a fluorescent coumarin chromophore, a hydrophilic oligo(ethylene glycol) chain, and a switchable oxazole heterocycle in the same covalent skeleton. Measurements of its two emissions in separate detection channels of a fluorescence microscope permit the noninvasive and ratiometric sensing of temperature at the micrometer level with millisecond response in aqueous solutions and within hydrogel matrices. The ratiometric optical output of this fluorescent molecular switch overcomes the limitations of single-wavelength fluorescent probes and enables noninvasive temperature mapping at length scales that are not accessible to conventional thermometers based on physical contact.

BODIPYs with Photoactivatable Fluorescence.

The borondipyrromethene (BODIPY) chromophore is a versatile platform for the construction of photoresponsive dyes with unique properties. Specifically, its covalent connection to a photocleavable group can be exploited to engineer compounds with photoswitchable fluorescence. The resulting photoactivatable fluorophores can increase their emission intensity or shift their emission wavelengths in response to switching.

Far-red photoactivatable BODIPYs for the super-resolution imaging of live cells.

The identification of viable designs to construct switchable fluorescent probes and operate them in the interior of live cells is essential to allow the acquisition of SMLM images and permit the visualization of cellular components with sub-diffraction resolution. Our laboratories developed a mechanism to switch the fluorescence of BODIPY chromophores with the photoinduced cleavage of oxazine heterocycles under mild 405-nm illumination. With appropriate structural modifications, these switchable molecules can be engineered to immobilize covalently on large biomolecules within lysosomal compartments of live COS-7 cells and produce bright far-red fluorescence with optimal contrast upon activation.

Compact, "Clickable" Quantum Dots Photoligated with Multifunctional Zwitterionic Polymers for Immunofluorescence and Imaging.

We detail the preparation of highly fluorescent quantum dots (QDs), surface-engineered with multifunctional polymer ligands that are compact and readily compatible with strain-promoted click conjugation, and the use of these nanocrystals in immunofluorescence and imaging. The ligand design combines the benefits of mixed coordination (i.e.

Photoactivatable fluorophores for single-molecule localization microscopy of live cells.

Photochemical reactions can be designed to convert either irreversibly or reversibly a nonemissive reactant into an emissive product. The irreversible disconnection of a photocleavable group from an emissive chromophore or the reversible interconversion of a photochromic component is generally exploited to implement these operating principles for fluorescence switching. In both instances, the interplay of activating radiation, to convert the nonemissive state into the emissive species, and exciting radiation, to produce fluorescence from the latter, can be exploited to switch fluorescence on in a given area of interest at a precise interval of time.

Live-Cell Imaging at the Nanoscale with Bioconjugatable and Photoactivatable Fluorophores.

Optical diffraction fundamentally limits the spatial resolution of conventional fluorescence images to length scales that are, at least, 2 orders of magnitude longer than the dimensions of individual molecules. As a result, the development of innovative probes and imaging schemes to overcome diffraction is very much needed to enable the investigation of the fundamental factors regulating cellular functions at the molecular level. In this context, the chemical synthesis of molecular constructs with photoactivatable fluorescence and the ability to label subcellular components of live cells can have transformative implications.

High-Throughput Single-Molecule Spectroscopy Resolves the Conformational Isomers of BODIPY Chromophores.

A borondipyrromethene (BODIPY) chromophore is connected to a benzoxazole, benzothiazole, or nitrobenzothiazole heterocycle through an olefinic bridge with configuration. Rotation about the two [C-C] bonds flanking the olefinic bridge occurs with fast kinetics in solution, leading to the equilibration of four conformational isomers for each compound. Ensemble spectroscopic measurements in solutions fail to distinguish the coexisting isomers.

Photopotentiation of the GABA receptor with caged diazepam.

As the inhibitory γ-aminobutyric acid-ergic (GABAergic) transmission has a pivotal role in the central nervous system (CNS) and defective forms of its synapses are associated with serious neurological disorders, numerous versions of caged GABA and, more recently, photoswitchable ligands have been developed to investigate such transmission. While the complementary nature of these probes is evident, the mechanisms by which the GABA receptors can be photocontrolled have not been fully exploited. In fact, the ultimate need for specificity is critical for the proper synaptic exploration.

An all-photonic full color RGB system based on molecular photoswitches.

On-command changes in the emission color of functional materials is a sought-after property in many contexts. Of particular interest are systems using light as the external trigger to induce the color changes. Here we report on a tri-component cocktail consisting of a fluorescent donor molecule and two photochromic acceptor molecules encapsulated in polymer micelles and we show that the color of the emitted fluorescence can be continuously changed from blue-to-green and from blue-to-red upon selective light-induced isomerization of the photochromic acceptors to the fluorescent forms.

Ratiometric temperature sensing with fluorescent thermochromic switches.

The connection of fluorescent chromophores to switchable heterocycles translates into molecular probes with ratiometric response to temperature. The opening and closing of their heterocyclic component equilibrates two emissive species with resolved fluorescence. Their relative emission intensities change monotonically with temperature to enable the visualization of thermal distributions at the microscale.

Far-Red Photoactivatable BODIPYs for the Super-Resolution Imaging of Live Cells.

The photoinduced disconnection of an oxazine heterocycle from a borondipyrromethene (BODIPY) chromophore activates bright far-red fluorescence. The high brightness of the product and the lack of autofluorescence in this spectral region allow its detection at the single-molecule level within the organelles of live cells. Indeed, these photoactivatable fluorophores localize in lysosomal compartments and remain covalently immobilized within these organelles.

Fluorescence activation with switchable oxazines.

The identification of operating principles to activate fluorescence under the influence of external stimulations is essential to enable the implementation of imaging strategies requiring the spatiotemporal control of emission. In this context, our laboratories designed mechanisms to switch fluorescence with either light or pH based on the unique photochemical and photophysical properties of either photoresponsive or halochromic oxazines respectively. These heterocycles can be connected covalently to fluorescent chromophores and opened with either light or pH to impose a significant bathochromic shift on the main absorption of the emissive appendage.

A Photoactivatable Far-Red/Near-Infrared BODIPY To Monitor Cellular Dynamics in Vivo.

A mechanism to photoactivate far-red/near-infrared fluorescence with infinite contrast and under mild visible illumination was designed around the photophysical properties of borondipyrromethene (BODIPY) dyes and the photochemical behavior of oxazine heterocycles. Specifically, the photoinduced and irreversible cleavage of an oxazine ring with a laser line at 405 nm extends the electronic conjugation of a BODIPY chromophore over a 3 H-indole auxochrome with a 2-(4-methoxyphenyl)ethenyl substituent in position 5. This structural transformation shifts bathochromically the main absorption band of the BODIPY component to allow the selective excitation of the photochemical product with a laser line of 633 nm and produce fluorescence between 600 and 850 nm.

Photochemical Barcodes.

A photochemical strategy to encode fluorescence signals in vivo with spatial control was designed around the unique properties of a photoactivatable borondipyrromethene (BODIPY). The photoinduced disconnection of two oxazines, flanking a single BODIPY, in two consecutive steps produces a mixture of three emissive molecules with resolved fluorescence inside polymer beads. The relative amounts and emission intensities of the three fluorophores can be regulated precisely in each bead by adjusting the dose of activating photons to mark individual particles with distinct codes of fluorescence signals.

The integration of triggered drug delivery with real time quantification using FRET; creating a super 'smart' drug delivery system.

The ability to control drug release at a specific physiological target enables the possibility of an enhanced therapeutic effect with reduced off-target toxic side effects. The discipline of controlled drug release has grown to include most areas of medicine with examples in the literature of targeted drug delivery to the majority of organs within the human body. In addition, a variety of external stimuli used to meditate the drug release process have also been investigated.

Highlighting Cancer Cells with Halochromic Switches.

Halochromic coumarin-oxazine prefluorophores and targeting folate ligands can be connected covalently to the side chains of amphiphilic polymers. The resulting macromolecular constructs assemble into nanoparticles in aqueous environments. The prefluorophores do not produce any detectable fluorescence at neutral pH, but are converted into fluorophores with intense visible emission at acidic pH.

Structural implications on the excitation dynamics of fluorescent 3H-indolium cations.

Fluorescent 3H-indolium cations are valuable components for the realization of activatable fluorophores for bioimaging applications. Their relatively poor fluorescent quantum yields in organic solvents, however, appear to be in contradiction to their good performance in analytical methods based on single-molecule detection. The elucidation of the structural factors governing the excitation dynamics of these compounds is, therefore, essential to rationalize these effects and possibly guide the future design of activatable probes with improved performance.

Bioimaging with Macromolecular Probes Incorporating Multiple BODIPY Fluorophores.

Seven macromolecular constructs incorporating multiple borondipyrromethene (BODIPY) fluorophores along a common poly(methacrylate) backbone with decyl and oligo(ethylene glycol) side chains were synthesized. The hydrophilic oligo(ethylene glycol) components impose solubility in aqueous environment on the overall assembly. The hydrophobic decyl chains effectively insulate the fluorophores from each other to prevent detrimental interchromophoric interactions and preserve their photophysical properties.

Free-energy predictions and absorption spectra calculations for supramolecular nanocarriers and their photoactive cargo.

We reconstructed the free-energy landscape for supramolecular nanoparticles of amphiphilic methacrylated-based co-polymers. Their self-assembly in aqueous solution and encapsulation of borondipyrromethene (BODIPY) derivatives were enforced through atomistic free-energy simulations. The BODIPY binding modes detected in each of the free-energy basins were validated through a comparison of theoretical absorption spectra, calculated at the TD-DFT level, to their experimental counterparts.