Practical synthetic route to functionalized rhodamine dyes

Poly(malic acid)-budesonide nanoconjugates embedded in microparticles for lung administration

To improve the therapeutic activity of inhaled glucocorticoids and reduce potential side effects, we designed a formulation combining the advantages of nanoparticles, which have an enhanced uptake by alveolar cells, allow targeted delivery and sustained drug release, as well as limited drug systemic passage, with those of microparticles, which display good alveolar deposition. Herein, a polymer-drug conjugate, poly(malic acid)-budesonide (PMAB), was first synthesized with either 11, 20, 33, or 43 mol% budesonide (drug:polymer from 1:8 to 3:4), the drug creating hydrophobic domains. The obtained conjugates self-assemble into nanoconjugates in water, yielding excellent drug loading of up to 73 wt%, with 80-100 nm diameters. In vitro assays showed that budesonide could be steadily released from the nanoconjugates, and the anti-inflammatory activity was preserved, as evidenced by reduced cytokine production in LPS-activated RAW 264.7 macrophages. Nanoconjugates were then embedded into microparticles through spray-drying with L-leucine, forming nano-embedded microparticles (NEMs). NEMs were produced with an aerodynamic diameter close to 1 µm and a density below 0.1 g.cm-3, indicative of a high alveolar deposition. NEMs spray-dried with the less hydrophobic nanoconjugates, PMAB 1:4, were readily dissolved in simulated lung fluid and were chosen for in vivo experiments to study pharmacokinetics in healthy rats. As it was released in vivo from NEMs, sustained distribution of budesonide was obtained for 48 h in lung tissue, cells, and lining fluid. With high loading rates, modulable release kinetics, and low cytotoxicity, these nanoconjugates delivered by NEMs are promising for the more efficient treatment of pulmonary inflammatory diseases.

Peptide nanovaccine conjugated via a retro-Diels-Alder reaction linker for overcoming the obstacle in lymph node penetration and eliciting robust cellular immunity

Nanoparticles have been regarded as a promising vaccine adjuvant due to their innate immune potentiation and enhanced antigen transport. However, the inefficient infiltration into the lymph node (LN) paracortex of nanoparticles caused by subcapsular sinus (SCS) obstruction is the main challenge in further improvement of nanovaccine immune efficacy. Herein, we propose to overcome paracortex penetration by using nanovaccine to spontaneously and continuously release antigens after retention in the SCS. In detail, we utilized a spontaneous retro-Diels-Alder (r-D-A) reaction linker to connect poly{(2-methyl-2-oxazoline)80-co-[(2-butyl-2-oxazoline)15-r-(2-thioethyl-2-oxazoline)8]} (PMBOxSH) and peptides for the peptide nanovaccine construction. The r-D-A reaction linker can spontaneously break over time, allowing the nanovaccine to release free antigens and adjuvants upon reaching the LN, thereby facilitating the entry of released antigens and adjuvants into the interior of the LNs. We showed that the efficacy of the peptide nanovaccine constructed using this dynamic linker could be significantly improved, thus greatly enhancing the tumor inhibition efficacy in the B16-OVA model. This dynamic-covalent-chemistry-based vaccine strategy may inspire designing more efficient therapeutic vaccines, especially those that require eliciting high-amount T cell responses.

Bioisostere-conjugated fluorescent probes for live-cell protein imaging without non-specific organelle accumulation

Specific labeling of proteins using membrane-permeable fluorescent probes is a powerful technique for bioimaging. Cationic fluorescent dyes with high fluorescence quantum yield, photostability, and water solubility provide highly useful scaffolds for protein-labeling probes. However, cationic probes generally show undesired accumulation in organelles, which causes a false-positive signal in localization analysis. Herein, we report a design strategy for probes that suppress undesired organelle accumulation using a bioisostere for intracellular protein imaging in living cells. Our design allows the protein labeling probes to possess both membrane permeability and suppress non-specific accumulation and has been shown to use several protein labeling systems, such as PYP-tag and Halo tag systems. We further developed a fluorogenic PYP-tag labeling probe for intracellular proteins and used it to visualize multiple localizations of target proteins in the intracellular system. Our strategy offers a versatile design for undesired accumulation-suppressed probes with cationic dye scaffolds and provides a valuable tool for intracellular protein imaging.

Amphiphilic Rhodamine Fluorescent Probes Combined with Basal Imaging for Fine Structures of the Cell Membrane

Confocal fluorescence imaging of fine structures of the cell membrane is important for understanding their biofunctions but is often neglected due to the lack of an effective method. Herein, we develop new amphiphilic rhodamine fluorescent probe RMGs in combination with basal imaging for this purpose. The probes show high signal-to-noise ratio and brightness and low internalization rate, making them suitable for imaging the fine substructures of the cell membrane. Using the representative probe RMG3, we not only observed the cell pseudopodia and intercellular nanotubes but also monitored the formation of migrasomes in real time. More importantly, in-depth imaging studies on more cell lines revealed for the first time that hepatocellular carcinoma cells secreted much more adherent extracellular vesicles than other cell lines, which might serve as a potential indicator of liver cells. We believe that RMGs may be useful for investigating the fine structures of the cell membrane.

Self-indicating polymers: a pathway to intelligent materials

Self-indicating polymers have emerged as a promising class of smart materials that possess the unique ability to undergo detectable variations in their physical or chemical properties in response to various stimuli. This article presents an overview of the most important mechanisms through which these materials exhibit self-indication, including aggregation, phase transition, covalent and non-covalent bond cleavage, isomerization, charge transfer, and energy transfer. Aggregation is a prevalent mechanism observed in self-indicating polymers, where changes in the degree of molecular organization result in variations in optical or electrical properties. Phase transition-induced self-indication relies on the transformation between different phases, such as liquid-to-solid or crystalline-to-amorphous transitions, leading to observable changes in color or conductivity. Covalent bond cleavage-based self-indicating polymers undergo controlled degradation or fragmentation upon exposure to specific triggers, resulting in noticeable variations in their structural or mechanical properties. Isomerization is another crucial mechanism exploited in self-indicating polymers, where the reversible transformation between the different isomeric forms induces detectable changes in fluorescence or absorption spectra. Charge transfer-based self-indicating polymers rely on the modulation of electron or hole transfer within the polymer backbone, manifesting as changes in electrical conductivity or redox properties. Energy transfer is an essential mechanism utilized by certain self-indicating polymers, where energy transfer between chromophores or fluorophores leads to variations in the emission characteristics. Furthermore, this review article highlights the diverse range of applications for self-indicating polymers. These materials find particular use in sensing and monitoring applications, where their responsive nature enables them to act as sensors for specific analytes, environmental parameters, or mechanical stress. Self-indicating polymers have also been used in the development of smart materials, including stimuli-responsive coatings, drug delivery systems, food sensors, wearable devices, and molecular switches. The unique combination of tunable properties and responsiveness makes self-indicating polymers highly promising for future advancements in the fields of biotechnology, materials science, and electronics.

Increasing the versatility of the biphenyl-fused-dioxacyclodecyne class of strained alkynes

Biphenyl-fused-dioxacyclodecynes are a promising class of strained alkyne for use in Cu-free 'click' reactions. In this paper, a series of functionalised derivatives of this class of reagent, containing fluorescent groups, are described. Studies aimed at understanding and increasing the reactivity of the alkynes are also presented, together with an investigation of the bioconjugation of the reagents with an azide-labelled protein.

Nanoscale metal-organic frameworks for the delivery of nucleic acids to cancer cells

Therapeutic nucleic acids (TNAs) are gaining increasing interest in the treatment of severe diseases including viral infections, inherited disorders, and cancers. However, the efficacy of intracellularly functioning TNAs is also reliant upon their delivery into the cellular environment, as unmodified nucleic acids are unable to cross the cell membrane mainly due to charge repulsion. Here we show that TNAs can be effectively delivered into the cellular environment using engineered nanoscale metal-organic frameworks (nanoMOFs), with the additional ability to tailor which cells receive the therapeutic cargo determined by the functional moieties grafted onto the nanoMOF's surface. This study paves the way to integrate the highly ordered programmable nucleic acids into larger-scale functionalized nanoassemblies.

Designing polymers for cartilage uptake: effects of architecture and molar mass

Osteoarthritis (OA) is a progressive disease, involving the progressive breakdown of cartilage, as well as changes to the synovium and bone. There are currently no disease-modifying treatments available clinically. An increasing understanding of the disease pathophysiology is leading to new potential therapeutics, but improved approaches are needed to deliver these drugs, particularly to cartilage tissue, which is avascular and contains a dense matrix of collagens and negatively charged aggrecan proteoglycans. Cationic delivery vehicles have been shown to effectively penetrate cartilage, but these studies have thus far largely focused on proteins or nanoparticles, and the effects of macromolecular architectures have not yet been explored. Described here is the synthesis of a small library of polycations composed of N-(2-hydroxypropyl)methacrylamide (HPMA) and N-(3-aminopropyl)methacrylamide (APMA) with linear, 4-arm, or 8-arm structures and varying degrees of polymerization (DP) by reversible addition fragmentation chain-transfer (RAFT) polymerization. Uptake and retention of the polycations in bovine articular cartilage was assessed. While all polycations penetrated cartilage, uptake and retention generally increased with DP before decreasing for the highest DP. In addition, uptake and retention were higher for the linear polycations compared to the 4-arm and 8-arm polycations. In general, the polycations were well tolerated by bovine chondrocytes, but the highest DP polycations imparted greater cytotoxicity. Overall, this study reveals that linear polymer architectures may be more favorable for binding to the cartilage matrix and that the DP can be tuned to maximize uptake while minimizing cytotoxicity.

Puromycin Prodrug Activation by Thioredoxin Reductase Overcomes Its Promiscuous Cytotoxicity

Overexpression of the selenoprotein thioredoxin reductase (TrxR) has been documented in malignant tissues and is of pathological significance for many types of tumors. The antibiotic puromycin (Puro) is a protein synthesis inhibitor causing premature polypeptide chain termination during translation. The well-defined action mechanism of Puro makes it a useful tool in biomedical studies. However, the nonselective cytotoxicity of Puro limits its therapeutic applications. We report herein the construction and evaluation of two Puro prodrugs, that is, S1-Puro with a five-membered cyclic disulfide trigger and S2-Puro with a linear disulfide trigger. S1-Puro is selectively activated by TrxR and shows the TrxR-dependent cytotoxicity to cancer cells, while S2-Puro is readily activated by thiols. Furthermore, S1-Puro displays higher stability in plasma than S2-Puro. We expect that this prodrug strategy may promote the further development of Puro as a therapeutic agent.

An original methodology to study polymeric nanoparticle-macrophage interactions: Nanoparticle tracking analysis in cell culture media and quantification of the internalized objects

Poly(lactic acid) (PLA) and poly(lactic-co-glycolic acid) (PLGA) are among the most employed (co)polymers for the preparation of drug nanocarriers for the treatment of cancer and infectious diseases. Before considering any clinical use, it is necessary to understand the interactions between polymeric nanoparticles (NPs) and their physiological environment, especially immune cells. Here, we propose a simple, yet precise method to assess NPs internalization kinetics in macrophages, based on the direct analysis of the cell culture media after different incubation times. The proof of concept is given here by using fluorescent PLGA NPs. Nanoparticle tracking analysis (NTA) was a method of choice, enabling detecting each individual NP and analyzing its trajectory while in Brownian motion. As compared to dynamic light scattering (DLS), NTA enabled a more precise determination of NP size distribution. The uptake process was rapid: in one hour, around a third of the NPs were internalized. In addition, the internalized NPs were visualized by confocal microscopy. The fluorescent cellular stacks were analyzed using a freely available macro for ImageJ software, Particle_In_Cell-3D. The internalized objects were localized and counted. This methodology could serve for further studies while analyzing the effects of NPs size, shape and surface properties on their interaction with various cell lines.

A Genetically Encoded Isonitrile Lysine for Orthogonal Bioorthogonal Labeling Schemes

Bioorthogonal click-reactions represent ideal means for labeling biomolecules selectively and specifically with suitable small synthetic dyes. Genetic code expansion (GCE) technology enables efficient site-selective installation of bioorthogonal handles onto proteins of interest (POIs). Incorporation of bioorthogonalized non-canonical amino acids is a minimally perturbing means of enabling the study of proteins in their native environment. The growing demand for the multiple modification of POIs has triggered the quest for developing orthogonal bioorthogonal reactions that allow simultaneous modification of biomolecules. The recently reported bioorthogonal [4 + 1] cycloaddition reaction of bulky tetrazines and sterically demanding isonitriles has prompted us to develop a non-canonical amino acid (ncAA) bearing a suitable isonitrile function. Herein we disclose the synthesis and genetic incorporation of this ncAA together with studies aiming at assessing the mutual orthogonality between its reaction with bulky tetrazines and the inverse electron demand Diels-Alder (IEDDA) reaction of bicyclononyne (BCN) and tetrazine. Results showed that the new ncAA, bulky-isonitrile-carbamate-lysine (BICK) is efficiently and specifically incorporated into proteins by genetic code expansion, and despite the slow [4 + 1] cycloaddition, enables the labeling of outer membrane receptors such as insulin receptor (IR) with a membrane-impermeable dye. Furthermore, double labeling of protein structures in live and fixed mammalian cells was achieved using the mutually orthogonal bioorthogonal IEDDA and [4 + 1] cycloaddition reaction pair, by introducing BICK through GCE and BCN through a HaloTag technique.

Upconversion luminescent nanomaterials: A promising new platform for food safety analysis

Foodborne diseases have become a significant threat to public health worldwide. Development of analytical techniques that enable fast and accurate detection of foodborne pathogens is significant for food science and safety research. Assays based on lanthanide (Ln) ion-doped upconversion nanoparticles (UCNPs) show up as a cutting edge platform in biomedical fields because of the superior physicochemical features of UCNPs, including negligible autofluorescence, large signal-to-noise ratio, minimum photodamage to biological samples, high penetration depth, and attractive optical and chemical features. In recent decades, this novel and promising technology has been gradually introduced to food safety research. Herein, we have reviewed the recent progress of Ln³⁺-doped UCNPs in food safety research with emphasis on the following aspects: 1) the upconversion mechanism and detection principles; 2) the history of UCNPs development in analytical chemistry; 3) the in-depth state-of-the-art synthesis strategies, including synthesis protocols for UCNPs, luminescence, structure, morphology, and surface engineering; 4) applications of UCNPs in foodborne pathogens detection, including mycotoxins, heavy metal ions, pesticide residue, antibiotics, estrogen residue, and pathogenic bacteria; and 5) the challenging and future perspectives of using UCNPs in food safety research. Considering the diversity and complexity of the foodborne harmful substances, developing novel detections and quantification techniques and the rigorous investigations about the effect of the harmful substances on human health should be accelerated.

Size-Dependent Biodistribution of Fluorescent Furano-Allocolchicinoid-Chitosan Formulations in Mice

The aim of this study was to compare the biodistribution in mice of functionalized rhodamine B (Rh) labeled colchicine derivative furano-allocolchicinoid (AC, 6) either conjugated to 40 kDa chitosan (AC-Chi, 8) or encapsulated into chitosan nanoparticles (AC-NPs). AC-NPs were formed by ionotropic gelation and were 400–450 nm in diameter as estimated in mice by dynamic light scattering and confocal microscopy. AC-Chi and AC-NPs preserved the specific colchicine activity in vitro. AC preparations were once IV injected into C75BL/6 mice; muscles, spleen, kidney, liver, lungs, blood cells and serum were collected at 30 min, 2, 5, 10, and 20 h post injection. To analyze the distribution of the furano-allocolchicinoid preparations in body liquids and tissues, Rh was measured directly in sera or extracted by acidic ethanol from tissue homogenates. Preliminary Rh extraction rate was estimated in vitro in tissue homogenates and was around 25–30% from total quantity added. After in vivo injection, AC-NPs were accumulated more in liver and spleen, while less in kidney and lungs in comparison with free AC and AC-Chi. Therefore, incorporation of colchicine derivatives as well as other hydrophobic substances into nano/micro sized carriers may help redistribute the drug to different organs and, possibly, improve antitumor accumulation.

A FRET Based Two-Photon Fluorescent Probe for Visualizing Mitochondrial Thiols of Living Cells and Tissues

Glutathione (GSH) is the main component of the mitochondrial thiol pool and plays key roles in the biological processes. Many evidences have suggested that cysteine and homocysteine also exist in mitochondria and are interrelated with GSH in biological systems. The fluctuation of the levels of mitochondrial thiols has been linked to many diseases and cells’ dysfunction. Therefore, the monitoring of mitochondrial thiol status is of great significance for clinical studies. We report here a novel fluorescence resonance energy transfer based two-photon probe MT-1 for mitochondrial thiols detection. MT-1 was constructed by integrating the naphthalimide moiety (donor) and rhodamine B (accepter and targeting group) through a newly designed linker. MT-1 shows a fast response, high selectivity, and sensitivity to thiols, as well as a low limit of detection. The two-photon property of MT-1 allows the direct visualization of thiols in live cells and tissues by two-photon microscopy. MT-1 can serve as an effective tool to unravel the diverse biological functions of mitochondrial thiols in living systems.

A new sensitive and subunit-selective molecular tool for investigating protein kinase A in the brain

Despite cellular complexity, a limited number of small molecules act as intracellular second messengers. Protein kinase A (PKA) is the main transducer of the information carried by cyclic adenosine monophosphate (cAMP). Recently, cellular imaging has achieved major technical advancements, although the search for more specific and sensitive low-molecular-weight probes to explore subcellular events involving second messengers is still in progress. The convergent synthesis of a novel, fluorescent small molecule comprising the cAMP structure and a rhodamine-based fluorescent residue, connected through a flexible linker, is described here. The interaction motif of this compound with PKA was investigated in silico using a blind docking approach, comparing its theoretical binding energy with the one calculated for cAMP. Moreover, the predicted pharmacokinetic properties were also computed and discussed. The new probe was tested on three areas of the mouse central nervous system (parietal cerebral cortex, hippocampus, and cerebellar cortex) with different fixation methods demonstrating remarkable selectivity towards the PKA RIα subunit. The probe showed overall better performances when compared to other commercially available fluorescent cAMP analogues, acting at lower concentrations, and providing stable labeling.

Multi-component supramolecular fibers with elastomeric properties and controlled drug release

Supramolecular fibers fabricated by co-axial electrospinning combine load-bearing properties and sustained drug release of hydrophobic and UPy-modified drugs.

Analytical control of Rhodamine B by SERS using reduced graphene decorated with copper selenide

A novel approach for the decoration of reduced graphene oxide with copper selenide (CuSe-rGO), using supercritical carbon dioxide (sc-CO₂) as a medium, was developed and proposed as a new substrate for surface-enhanced Raman spectroscopy (SERS) to determine Rhodamine B in chili powder. The synthesized materials graphene oxide (GO), reduced graphene oxide (rGO) and CuSe-rGO were characterized by Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). All SERS spectra were obtained by using a portable Raman spectrometer. The procedure presented involves a simple and rapid sample pretreatment in order to determine Rhodamine B in chili powder, with a limit of quantification of 44.5 ng g^-1. The recovery values of the proposed method resulted in the 96% to 99% range, with RSD values from 2.4% to 3.0%. The developed SERS active hybrid substrate has an enhancement factor higher than those using gold or silver nanoparticles, providing a clear improvement in the sensitivity.

Synthesis and Characterization of ROSA Dye - A Rhodamine B-type Fluorophore, Suitable for Bioconjugation and Fluorescence Studies in Live Cells

BACKGROUND

Herein we report the multigram-scale synthesis, characterization and application of a rhodamine B-based fluorophore (ROSA) suitable for fluorescent studies in biological applications. This fluorophore is devoid of rhodamine spirolactone formation and furthermore characterized by a high molar extinction coefficient (ϵ=87250 ± 1630 M-1cm-1) and quantum yield (φ) of 0.589 ± 0.070 in water. Reported here is also the application of ROSA towards synthesis of a ROSA-PEG-GRGDS-NH2 fluorescent probe suitable for live cell imaging of αvβ3 integrins for in vitro assays.

OBJECTIVES

The main objective of this study is to efficiently prepare rhodamine B derivative, devoid of spirolactone formation that would be suitable for bioconjugation and subsequent bioimaging.

METHODS

Rhodamine B was transformed into rhodamine B succinimide ester (RhoB-OSu) using N-hydroxysuccinimide. RhoB-OSu was further coupled to sarcosine to obtain rhodamine Bsarcosine dye (ROSA) in good yield. The ROSA dye was then coupled to a αvβ3 integrin binding sequence using standard solid-phase conditions. Resulting ROSA-PEG-GRGDS-NH2 probe was used to image integrins on cancer cells.

RESULTS

The rhodamine B-sarcosine dye (ROSA) was obtained in multigram scale in good total yield of 47%. Unlike rhodamine B, the ROSA dye does not undergo pH-dependent spirolactone/spirolactam formation as compared with rhodamine B-glycine. It is also characterized by excellent quantum yield (φ) of 0.589 ± 0.070 in water and high molar extinction coefficient of 87250 ± 1630 M-1cm-1. ROSA coupling to the RGD-like peptide was proved to be efficient and straightforward. Imaging using standard filters on multimode plate reader and confocal microscope was performed. The αvβ3 integrins present on the surface of live WM-266-4 (melanoma) and MCF- 7 (breast cancer) cells were successfully imaged.

CONCLUSION

We successfully derivatized rhodamine B to create an inexpensive, stable and convenient to use fluorescent probe. The obtained derivative has excellent photochemical properties and it is suitable for bioconjugation and many imaging applications.

A functionalized hydroxydopamine quinone links thiol modification to neuronal cell death

Recent findings suggest that dopamine oxidation contributes to the development of Parkinson's disease (PD); however, the mechanistic details remain elusive. Here, we compare 6-hydroxydopamine (6-OHDA), a product of dopamine oxidation that commonly induces dopaminergic neurodegeneration in laboratory animals, with a synthetic alkyne-functionalized 6-OHDA variant. This synthetic molecule provides insights into the reactivity of quinone and neuromelanin formation. Employing Huisgen cycloaddition chemistry (or “click chemistry”) and fluorescence imaging, we found that reactive 6-OHDA p-quinones cause widespread protein modification in isolated proteins, lysates and cells. We identified cysteine thiols as the target site and investigated the impact of proteome modification by quinones on cell viability. Mass spectrometry following cycloaddition chemistry produced a large number of 6-OHDA modified targets including proteins involved in redox regulation. Functional in vitro assays demonstrated that 6-OHDA inactivates protein disulfide isomerase (PDI), which is a central player in protein folding and redox homeostasis. Our study links dopamine oxidation to protein modification and protein folding in dopaminergic neurons and the PD model.

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Chemical modification of 6-OHDA increases stability of 6-OHDA p-quinone by preventing neuromelanin formation.

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Modified 6-OHDA enables visualization of thiol-dependent protein modification by p-quinone.

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Wide-spread proteome modification by 6-OHDA p-quinone impairs neuroblastoma viability.

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6-OHDA p-quinone inactivates PDI linking dopamine oxidation to protein unfolding.

Rhodamine B derivative-modified up-conversion nanoparticle probes based on fluorescence resonance energy transfer (FRET) for the solid-based detection of copper ions

Herein, a novel solid-based up-conversion fluorescence resonance energy transfer (FRET) sensor was developed using rhodamine B hydrazide, which provided a selective fluorescence response and suitable affinity towards Cu²⁺ ions over other biologically relevant metal ions because the Cu²⁺ ion could promote the hydrolysis of α-amino acid esters of rhodamine B hydrazide and yield the Cu·α-amino acid chelate. This solid-based detection system is more convenient for the detection of Cu²⁺ based on color change and emission spectra instead of the complicated and tedious measurements than other up-conversion sensors and up-conversion luminescent nanoparticles used as an excitation source; moreover, the proposed system shows high selectivity, minimum photo-damage to living organisms, and high chemical stability.

PluS Nanoparticles Loaded with Sorafenib: Synthetic Approach and Their Effects on Endothelial Cells

Silica nanostructures are widely investigated for theranostic applications since relatively mild and easy synthetic methods allow the fabrication of multicompartment nanoparticles (NPs) and fine modulation of their properties. Here, we report the optimization of a synthetic strategy leading to brightly fluorescent silica NPs with a high loading ability, up to 45 molecules per NP, of Sorafenib, a small molecule acting as an antiangiogenic drug. We demonstrate that these NPs can efficiently release the drug and they are able to inhibit endothelial cell proliferation and migration and network formation. Their lyophilization can endow them with long shelf stability, whereas, once in solution, they show a much slower release compared to analogous micellar systems. Interestingly, Sorafenib released from Pluronic silica NPs completely prevented endothelial cell responses and postreceptor mitogen-activated protein kinase signaling ignited by vascular endothelial growth factor, one of the major players of tumor angiogenesis. Our results indicate that these theranostic systems represent a promising structure for anticancer applications since NPs alone have no cytotoxic effect on cultured endothelial cells, a cell type to which drugs and exogenous material are always in contact once delivered.

Protein-functionalized nanoparticles derived from end-functional polymers and polymer prodrugs for crossing the blood-brain barrier

Nanoparticles may provide a viable way for neuroprotective drugs to cross the blood-brain barrier (BBB), which limits the passage of most drugs from the peripheral circulation to the brain. Heterotelechelic polymer prodrugs comprising a neuroprotective model drug (adenosine) and a maleimide functionality were synthesized by the "drug-initiated" approach and subsequent nitroxide exchange reaction. Nanoparticles were obtained by nanoprecipitation and exhibited high colloidal stability with diameters in the 162-185 nm range and narrow size distributions. Nanoparticles were then covalently surface-conjugated to different proteins (albumin, α2-macroglobulin and fetuin A) to test their capability of enhancing BBB translocation. Their performances in terms of endothelial permeability and cellular uptake in an in vitro BBB model were compared to that of similar nanoparticles with surface-adsorbed proteins, functionalized or not with the drug. It was shown that bare NPs (i.e., NPs not surface-functionalized with proteins) without the drug exhibited significant permeability and cellular uptake, which were further enhanced by NP surface functionalization with α2-macroglobulin. However, the presence of the drug at the polymer chain-end prevented efficient passage of all types of NPs through the BBB model, likely due to adecrease in the hydrophobicity of the nanoparticle surface and alteration of the protein binding/coupling, respectively. These results established a new and facile synthetic approach for the surface-functionalization of polymer nanoparticles for brain delivery purposes.

Visualizing the brain's astrocytes

Astrocytes are the most abundant cell type in the brain and are a crucial part of solving its mysteries. Originally assumed to be passive supporting cells, astrocyte's functions are now recognized to include active modulation and information processing at the neural synapse. The full extent of the astrocyte contribution to neural processing remains unknown. This is, in part, due to the lack of methods available for astrocyte identification and analysis. Existing strategies employ genetic tools like the astrocyte specific promoters glial fibrillary acidic protein (GFAP) or Aldh1L1 to create transgenic animals with fluorescently labeled astrocytes. Recently, small molecule targeting moieties have enabled the delivery of bright fluorescent dyes to astrocytes. Here, we review methods for targeting astrocytes, with a focus on a recently developed methylpyridinium targeting moiety's development, chemical synthesis, and elaboration to provide new features like light-based spatiotemporal control of cell labeling.

Simultaneous and Traceless Ligation of Peptide Fragments on DNA Scaffold

Peptide ligation is an indispensable step in the chemical synthesis of target peptides and proteins that are difficult to synthesize at once by a solid-phase synthesis. The ligation reaction is generally conducted with two peptide fragments at a high aqueous concentration to increase the reaction rate; however, this often causes unpredictable aggregation and precipitation of starting or resulting peptides due to their hydrophobicities. Here, we have developed a novel peptide ligation strategy harnessing the two intrinsic characteristics of oligodeoxynucleotides (ODNs), i.e., their hydrophilicity and hybridization ability, which allowed increases in the water solubility of peptides and the reaction kinetics due to the proximity effect, respectively. Peptide-ODN conjugates that can be cleaved to regenerate native peptide sequences were synthesized using novel lysine derivatives containing conjugation handles and photolabile linkers, via solid-phase peptide synthesis and subsequent conjugation to 15-mer ODNs. Two complementary conjugates were applied to carbodiimide-mediated peptide ligation on a DNA scaffold, and the subsequent DNA removal was conducted by photoirradiation in a traceless fashion. This DNA scaffold-assisted ligation resulted in a significant acceleration of the reaction kinetics and enabled ligation of a hydrophobic peptide at a micromolar concentration. On the basis of this chemistry, a simultaneous ligation of three different peptide fragments on two different DNA scaffolds has been conducted for the first time.

Engineered Nanostructured Materials for Ofloxacin Delivery

Antibiotic resistance is emerging as a growing worldwide problem and finding solutions to this issue is becoming a new challenge for scientists. As the development of new drugs slowed down, advances in nanotechnology offer great opportunities, with the possibility of designing new systems for carrying, delivery and administration of drugs already in use. Engineered combinations of the synthetic, broad-spectrum antibiotic ofloxacin, rarely studied in this field, with different types of silver, mesoporous silica-based and Pluronic/silica-based nanoparticles have been explored. The nanocarriers as silver core@silica mesoporous (AgMSNPs) and dye-doped silica nanoparticles functionalized with ofloxacin were synthesized and their antibacterial properties studied against S. aureus and E. coli. The best antibacterial results were obtained for the AgMSNPs nanosystem@ofloxacin for the strain S. aureus ATCC 25923, with MIC and MBC values of 5 and 25 μg/mL, proving the efficacy and synergetic effect of the antibiotic and the Ag core of the nanoparticles.

Rhodamine B in spices determined by a sensitive UPLC-MS/MS method

Rhodamine B (RhB) is a banned food additive and has been classified as illegal colourant. Therefore, the risk of RhB contamination should be strictly monitored. In this study, a sensitive UPLC-MS/MS method was applied to monitor RhB in 292 various spices such as chilli, pepper and tomato products. The results showed 22.7% of chilli powder samples, 18.5% of pepper powder samples, 11.1% of chilli oil samples and 9.1% of pepper oil samples were contaminated with RhB. Chilli powder contained RhB up to 44,935 μg/kg with an average of 743 μg/kg, pepper powder up to 65.9 μg/kg with an average of 4.1 μg/kg, chilli oil up to 14.6 μg/kg with an average of 1.0 μg/kg and pepper oil up to 1.1 μg/kg with an average of 0.2 μg/kg, respectively. Considering the common consumption of chilli products and pepper products by so many consumers, RhB exposure is significant and should be decreased.

The Role of Colloidal Stability and Charge in Functionalization of Aqueous Quantum Dots

Semiconductor quantum dots (QDs), also known as nanocrystals, have unique photophysical properties that have allowed them to find utility in many applications, including television and display technologies. They also have significant potential as imaging agents in the biomedical field. To gain the most value from the use of QDs as health-related fluorescent probes, they must be biologically targetable and sensitive to metabolic analytes such as pH and O₂, and the resulting signal must be quantifiable. To achieve these goals, QDs need to be conjugated to vectors such as antibodies or environmentally sensitive chromophores. Until recently, the functionalization of these nanomaterials required a complex fully "bottom-up" approach beginning with the synthesis of the QDs and subsequent manipulations. To simplify this process, our group set out to develop straightforward methods to prepare functionalized nanomaterials for biological imaging and sensing using low-cost, commercially available aqueous QD dispersions. In this Account, we review the common problems and likely solutions related to functionalization of QDs in water with chemical and biological vectors. Early in our investigations, we found that established protocols using a commercially available activating reagent resulted in either low reaction yields or QD precipitation. This was a consequence of the perturbation of the QDs' surface charges by the activating reagent and the conjugation substrate. These surface charges are derived from the anionic surfactants that are commonly employed for encapsulating water-soluble nanomaterials. Thus, cancellation of the surface charges by reagents or substrates results in colloidal instability. To address this problem, we devised conjugation methods that do not alter the overall charge balance of the system. Incorporating reactive moieties directly into the QD's water-solubilizing polymer encapsulants negates the need for destabilizing activators, allowing for functionalization of aqueous samples without precipitation. The most successful approach was realized using neutral activating reagents, such as poly(ethylene glycol) carbodiimide (PEG-CD). PEG-CD binds to the carboxylic acid coating of water-soluble QDs, which primes them for amide bond formation with amine-functionalized substrates. Most importantly, this method can be applied to commercially available aqueous QDs. Using this method, we achieved reaction yields as high as 95%, allowing us to demonstrate a wide-range of QD functionalities and applications for chemical and biological sensing. Conjugation of environmentally sensitive dyes to water-soluble QDs results in reversible and ratiometrically reporting fluorescent probes for metabolic analytes such as pH, bisulfide, and O₂. QDs can also be functionalized with proteins for passive cell delivery or coated with poly(ethylene glycol) to enhance biocompatibility for in vivo studies. In the future, these capabilities may be combined to realize the full potential of quantum dot nanotechnology for biological discovery.

Visualizing the Brain's Astrocytes with Diverse Chemical Scaffolds

Astrocytes are the most abundant cells in the brain. They support neurons, adjust synaptic strength, and modulate neuronal signaling, yet the full extent of their functions is obscured by the dearth of methods for their visualization and analysis. Here, we report a chemical reporter that targets small molecules specifically to astrocytes both in vitro and in vivo. Fluorescent versions of this tag are imported through an organic cation transporter to label glia across species. The structural modularity of this approach will enable wide-ranging applications for understanding astrocyte biology.

Phytosynthetic Ag doped ZnO nanoparticles: Semiconducting green remediators

Highly stable semiconducting silver doped zinc oxide nanoparticles have been synthesized via facile, biomimetic and sustainable route, through utilization of Zinc acetate dihydrate (C4H6O4Zn · 2H2O) as host, Silver nitrate (AgNO3) as dopant and phytochemicals of angiospermic medicinal plant Prunus cerasifera as the reducing agents. Synthesis of Ag doped ZnO nanoparticles was done in a one pot synthetic mode by varying the amount of dopant from 0.2 – 2.0%. Synthesized photocatalyst nanoparticles were analyzed via UV-vis, FTIR, XRD and SEM. Commendable alleviation in the direct band gap i.e. 2.81 eV was achieved as a result of doping. Silver doped zinc oxide nanoparticles size ranged between 72.11 – 100 nm with rough surface morphology and higher polydispersity degree. The XRD patterns revealed the hexagonal wurtzite geometry of crystals with an average crystallite size of 2.99 nm. Persistent organic dyes Methyl Orange, Safranin O and Rhodamine B were sustainably photodegraded in direct solar irradiance with remarkable degradation percentages up to 81.76, 74.11 and 85.52% in limited time with pseudo first order reaction kinetics (R2 =0.99, 0.99 and 0.97). Furthermore, efficient inhibition against nine microbes of biomedical and agriculturally significance was achieved. Synthesized nanoparticles are potential green remediators of polluted water and perilous pathogens.

Post-fabrication QAC-functionalized thermoplastic polyurethane for contact-killing catheter applications

The use of catheters is ubiquitous in medicine and the incidence of infection remains unacceptably high despite numerous advances in functional surfaces and drug elution. Herein we report the use of a thermoplastic polyurethane containing an allyl ether side-chain functionality (allyl-TPU) that allows for rapid and convenient surface modification with antimicrobial reagents, post-processing. This post-processing functionalization affords the ability to target appropriate TPU properties and maintain the functional groups on the surface of the device where they do not affect bulk properties. A series of quaternary ammonium thiol compounds (Qx-SH) possessing various hydrocarbon tail lengths (8-14 carbons) were synthesized and attached to the surface using thiol-ene "click" chemistry. A quantitative assessment of the amount of Qx-SH available on the surface was determined using fluorescence spectroscopy and X-ray photoelectron spectroscopy (XPS). Contact-killing assays note the Q8-SH composition has the highest antimicrobial activity, and a live/dead fluorescence assay reveals rapid contact-killing of Staphylococcus aureus (>75% in 5 min) and Escherichia coli (90% in 10 min) inocula. Scale-up and extrusion of allyl-TPU provides catheter prototypes for biofilm formation testing with Pseudomonas aeruginosa, and surface-functionalized catheters modified with Q8-SH demonstrate their ability to reduce biofilm formation.

Two-photon fluorescent polysiloxane-based films with thermally responsive self switching properties achieved by a unique reversible spirocyclization mechanism

The first example of a two-photon fluorescent polysiloxane-based film with fantastic thermal-responsive properties was reported. A unique alkaline tuned reversible spirocyclization mechanism was proposed.

Responsiveness and reversibility are present in nature, and are ubiquitous in biological systems. The realization of reversibility and responsiveness is of great importance in the development of properties and the design of new materials. However, two-photon fluorescent thermal-responsive materials have not been reported to date. Herein, we engineered thermally responsive polysiloxane materials (Dns-non) that exhibited unique two-photon luminescence, and this is the first report about thermally responsive luminescent materials with two-photon fluorescence. The fluorescence of Dns-non could switch from the “on” to “off” state through a facile heating and cooling process, which could be observed by the naked eye. Monitoring the temperature of the CPU in situ was achieved by easily coating D1-non onto the CPU surface, which verified the potential application in devices of Dns-non. A unique alkaline tuned reversible transition mechanism of rhodamine-B from its spirocyclic to its ring-open state was proposed. Furthermore, Dns-non appeared to be a useful cell adhesive for the culture of cells on the surface. We believe that the constructed thermally responsive silicon films which have promising utilization as a new type of functional fluorescent material, may show broad applications in materials chemistry or bioscience.

A solid-phase synthetic approach to pH-independent rhodamine-type fluorophores

An efficient methodology using the Fukuyama-Mitsunobu reaction was successfully applied to prepare various Rhodamine B-based amides with the locked possibility to form a lactam ring. The procedure was developed for solid-phase synthesis, which can be advantageously applied to the synthesis of chemical libraries in a combinatorial fashion. A series of derivatives including aliphatic as well as aromatic rhodamine amides alkylated via a reaction with various alcohols were synthesized, and their spectral properties were investigated. Blocking lactamization via N-alkylation enabled us to prepare rhodamine derivatives with an excellent fluorescence response. In comparison to their non-alkylated counterparts, these derivatives exhibited pH independence and higher quantum yields.

On-demand one-step synthesis of small-sized fluorescent–magnetic bifunctional microparticles on a droplet-splitting chip

Generation of small-sized multifunctional microparticles: multifunctional microparticles were easily produced based on droplet splitting and photopolymerization in a single step.

Water-soluble and adjustable fluorescence copolymers containing a hydrochromic dye: synthesis, characterization and properties

Water solubility and adjustable fluorescence properties have been successfully implemented in the hydrochromic amino rhodamine via copolymerization. Four copolymers have been synthesized and clearly characterized by UV-Vis spectroscopy, proving greater detail than the commonly used NMR and IR technologies. The four copolymers have good solubility in pure water and in many common organic solvents, while preserving the hydrochromism of the dye monomer. Based on aggregation and dispersion of the copolymers as adjusted by solvent media and temperature, reversible fluorescence properties were successfully realized. Furthermore, their luminescence in solid state was observed. These studies are of great significance for expanding the application of hydrochromic dyes in biological fields and promoting green industrialization.

Water solubility and adjustable fluorescence adjustable properties have been successfully endowed to established in a hydrochromic dye via copolymerization.

Novel cell-penetrating-amyloid peptide conjugates preferentially kill cancer cells

The goal of this study was to develop a peptide which could use the toxic effects of amyloid, a substance which is the hallmark of over 25 known human diseases, to selectively kill cancer cells. Here we demonstrate that two separate amyloid-forming hexapeptides, one from the microtubule associated protein Tau involved in formation of paired helical filaments of Alzheimer's disease, and the other an amyloid forming sequence from apolipoprotein A1, when conjugated to a cell penetrating peptide (CPP) sequence, form toxic oligomers which are stable for up to 14 h and able to enter cells by a combination of endocytosis and transduction. The amyloid peptide conjugates showed selective cytotoxicity to breast cancer, neuroblastoma and cervical cancer cells in culture compared to normal cells. Fluorescence imaging experiments showed the CPP-amyloid peptide oligomers formed intracellular fibrous amyloid, visible in the endosomes/lysosomes, cytosol and nucleus with thioflavin S (ThS) staining. Further experiments with rhodamine-conjugated Dextran, propidium iodide (PI), and acridine orange (AO) suggested the mechanism of cell death was the permeability of the lysosomal membrane brought about by the formation of amyloid pores. Cytotoxicity could be abrogated by inhibitors of lysosomal hydrolases, consistent with a model where lysosomal hydrolases leak into the cytosol and induce cytotoxicity in subsequent downstream steps. Taken together, our data suggest that CPP-amyloid peptide conjugates show potential as a new class of anti-cancer peptides (ACPs).

Novel Cell Model for Tauopathy Induced by a Cell-Permeable Tau-Related Peptide

In the present study, a cell penetrating peptide (CPP)-amyloid conjugate was prepared (T-peptide), where the amyloid-forming sequence was homologous to a nucleating sequence from human Tau protein (³⁰⁶VQIVYK³¹¹). Kinetic and biophysical studies showed the peptide formed long-lived oligomers which were taken up by endocytosis and localized in perinuclear vesicles and in the cytoplasm of murine hippocampal neuroblastoma cells and human HeLa cells. Thioflavin S (ThS) staining of amyloid colocalized with pathological phosphorylated Tau, suggesting that the peptide was able to seed endogenous wild-type Tau. Subsequent experiments showed that aggregates present in the lysosomes mediated lysosome membrane permeability (LMP). We observed a decrease in total Tau, irrespective of phosphorylation state, consistent with Tau fragmentation by lysosomal proteases. We found cytotoxicity of T-peptide could be abrogated by inhibitors of lysosomal hydrolases and caspases, consistent with a model where Tau fragments processed by the lysosome leak into the cytoplasm and induce toxicity in subsequent downstream steps. It is our hope that the T-peptide system may prove amenable to the evaluation of small molecule inhibitors of cytotoxicity, especially those which target either Tau aggregation or the lysosomal/autophagy system.

Sensitive Detection of Rhodamine B in Condiments Using Surface-Enhanced Resonance Raman Scattering (SERRS) Silver Nanowires as Substrate

In this paper, a facile large-scale preparation of surface-enhanced resonance Raman scattering (SERRS) substrates for the determination of Rhodamine B (RhB) based on silver nanowires (Ag NWs) has been developed. The morphology, structure, and properties of as-prepared Ag NWs are characterized using ultraviolet-visible (UV-Vis) spectroscopy, field emission scanning electron microscopy (FE-SEM), and X-ray diffraction (XRD), respectively. Ag NWs were assembled onto glass slides through a self-assembly method. Moreover, in our experiment, as-prepared Ag NWs@glass were used as a SERRS substrate to detect RhB at the excitation wavelength of 532 nm. Experimental conditions such as pH value and soaking time on SERRS performance were studied and optimized. Under the optimized conditions, the SERRS intensity at 1648 cm^-1 exhibited a linear relationship with the concentration of RhB in the range of 1.0 × 10^-9-1.0 × 10^-5mol L^-1 and detection limit (signal-to-noise ratio [S/N] = 3) is as low as 0.3 nmol L^-1. The corresponding correlation coefficient of the linear equation was 0.996. This method based on Ag NWs@glass for the detection of RhB in three kinds of condiment was investigated. The limits of detection (LODs) for RhB were 0.35 µg/g in chili powder, 0.14 µg/g in chili sauce, and 0.02 µg/g in Chinese prickly ash. The relative standard deviations (RSD) were between 2.18% and 4.56% (n = 3) and recoveries at three levels were in the range of 80.0-98.7% for different spiked food products. Moreover, the results showed that the proposed method was sensitive, convenient, and feasible for the determination of RhB in condiments.

Rapid Screening and Identification of Living Pathogenic Organisms via Optimized Bioorthogonal Non-canonical Amino Acid Tagging

Pathogenic bacteria can be a major cause of illness from environmental sources as well as the consumption of contaminated products, giving rise to public health concerns globally. The surveillance of such living organisms in food and water supplies remains an important challenge in mitigating their deleterious societal effects. Here, we have developed an optimized bioorthogonal non-canonical amino acid tagging approach to the imaging, capture, and interrogation of shigatoxigenic/verotoxigenic Escherichia coli (VTEC) and Listeria that enables the distinction between living wild-type pathogenic bacteria. The approaches utilize homopropargylglycine (HPG), as well as optimized growth media, that restricts endogenous methionine biosynthesis in a variety of species of public health concern. Endogenous methionine residues are then replaced with HPG, which can then be modified using a myriad of compatible bioorthogonal reactions for tagging of exclusively live bacteria. The methods reported allow for the very rapid screening and identification of living pathogenic organisms.

Hg(II) sensing platforms with improved photostability: The combination of rhodamine derived chemosensors and up-conversion nanocrystals

This paper reported two nanocomposite sensing platforms for Hg(II) detection with improved photostability, using two rhodamine derivatives as chemosensors and up-conversion nanocrystals as excitation host, respectively. There existed a secondary energy transfer from this excitation host to these chemosensors, which was confirmed by spectral analysis, energy transfer radius calculation and emission decay lifetime comparison. In this case, chemosensor photostability was greatly improved. Further analysis suggested that these chemosensors recognized Hg(II) following a simple binding stoichiometry of 1:1. Hg(II) sensing performance of these sensing platforms was analyzed through their emission spectra upon various Hg(II) concentrations. Emission spectral response, Stern-Volmer equation, emission stability and sensing selectivity were discussed in detail. It was finally concluded that these chemosensors showed emission turn on effect towards Hg(II), with high photostability, good selectivity and linear response.

Methyltransferase-directed covalent coupling of fluorophores to DNA

Highly efficient DNA labelling using an enzymatically-directed, strain-promoted azide–alkyne cycloaddition.

We report an assay for determining the number of fluorophores conjugated to single plasmid DNA molecules and apply this to compare the efficiency of fluorophore coupling strategies for covalent DNA labelling. We compare a copper-catalyzed azide–alkyne cycloaddition reaction, amine to N-hydroxysuccinimidyl ester coupling reaction and strain-promoted azide–alkyne cycloaddition reaction for fluorescent DNA labelling. We found increased labelling efficiency going from the amine to N-hydroxysuccinimidyl ester coupling reaction to the copper-catalyzed azide–alkyne cycloaddition and found the highest degree of DNA labelling with the strain-promoted azide–alkyne cycloaddition reaction. We also examined the effect of labelling on the DNA structure using atomic force microscopy. We observe no distortions or damage to the DNA that was labeled using the amine to N-hydroxysuccinimidyl ester and strain-promoted azide–alkyne cycloaddition coupling reactions. This was in contrast to the copper-catalyzed azide–alkyne cycloaddition reaction, which, despite the use of copper-coordinating ligands in the labelling mixture, leads to some structural DNA damage (single-stranded DNA breaks).