Multi-action of a Fluorophore in the Sight of Light: Release of NO, Emergence of FONs, and Organelle Switching

Light, as an external stimulus, has begun to engage a phenomenal role in the diverse field of science. Encouraged by recent progress from biology to materials chemistry, various light-responsive fluorescent probes have been developed. Herein, we present a 1,8-naphthalimide-based probe NIT-NO₂ capable of releasing nitric oxide (NO) along with the formation of fluorescent organic nanoparticles (FONs) upon exposure to near-visible UV light. By synthesizing the photoproduct NIT-OH, we unveiled that initially NIT-NO₂ released NO and converted to NIT-OH, while prolonged irradiation led to the formation of FONs that is corroborated by the red-edge excitation shift as well as microscopic investigation. Finally, we have successfully applied NIT-NO₂ and NIT-OH for specific labeling of lipid droplets and plasma membranes, respectively, and demonstrated the switching from lipid droplets to plasma membranes by using light as a stimulus. These two probes show unique imaging applications inside the cells depending on the polarity and hydrophobicity of the environment. This work paves a fascinating way for the generation of excitation-dependent FONs from a small organic fluorophore and highlights its potency as an exclusive imaging tool.

Mechanistic Approaches to the Light-Induced Neural Cell Differentiation: Photobiomodulation vs Low-Dose Photodynamic Therapy

BACKGROUND

Neurodegenerative diseases are the results of irreversible damages in the neuronal cells by affecting vital functions temporarily or even permanently. The use of light for the treatment of these diseases is an emerging promising innovative method. Photobiomodulation (PBM) and Photodynamic Therapy (PDT) are the modalities that have a wide range of use in medicine and have opposite purposes, biostimulation and cell death respectively.

METHODS

In this study, we aimed to compare these two modalities (PDT and PBM) at low-level intensities and create a stimulatory effect on the differentiation of PC12 cells. Three different energy densities (1, 3, and 5 J/cm²) were used in PBM and Chlorin e6-mediated PDT applications upon irradiation with 655-nm laser light. The light-induced differentiation profile of PC12 cells was analyzed by morphological examinations, qRT-PCR, cell viability assay, and some mechanistic approaches such as; the analysis of intracellular ROS production, NO release, and mitochondrial membrane potential change.

RESULTS

It has been observed that both of these modalities were successful at neural cell differentiation. PBM at 1 J/cm² and low-dose PDT at 3 J/cm² energy densities provided the best differentiation profiles which were proved by the over-expressions of SYN-1 and GAP43 genes. It was also observed that intracellular ROS production and NO release had pivotal roles in these mechanisms with more cell differentiation obtained especially in low-dose PDT application.

CONCLUSION

It can be concluded that light-induced mechanisms with properly optimized light parameters have the capacity for neural cell regeneration and thus, can be a successful treatment for incurable neurodegenerative diseases.

Preparing a novel magnesium-doped hyaluronan/polyethyleneimine nanoparticle to improve endothelial functionalisation

Nowadays, tissue engineering vascularisation has become an important means of organ repair and treatment of major traumatic diseases. Vascular endothelial layer regeneration and endothelial functionalisation are prerequisites and important components of tissue engineering vascularisation. The present researches of endothelial functionalisation mainly focus on tissue engineering scaffold preparation and implant surface modification. Few studies have reported the interaction of endothelial functionalisation and scaled materials, especially the nanomaterials. Magnesium (Mg), as an essential cytotropic active element in the human body, should promote the growth of endothelial cells. However, the authors' previous work found that the Mg in the alloys had a defect of delayed endothelialisation, which may be attributed to the non-uniform scales of the degradation products from Mg alloys. To validate this hypothesis and fabricate a novel nanomaterial for tissue engineering vascularisation, the authors prepared Mg-doped hyaluronan (HA)/polyethyleneimine (PEI) nanoparticles for endothelial cells testing. Their data showed that the Mg-doped HA/PEI nanoparticle with small scales (diameter <150 nm) presented better ability on improving endothelial cells growth, functionalisation and nitric oxide release.

Efficient Near Infrared Light Triggered Nitric Oxide Release Nanocomposites for Sensitizing Mild Photothermal Therapy

Mild photothermal therapy (PTT), as a new anticancer therapeutic strategy, faces big challenges of limited therapeutic accuracy and side-effects due to uneven heat distribution. Here, near infrared triggered nitric oxide (NO) release nanocomposites based on bismuth sulfide (Bi2S3) nanoparticles and bis-N-nitroso compounds (BNN) are constructed for NO-enhanced mild photothermal therapy. Upon 808 nm irradiation, the high photothermal conversion efficiency and on-demand NO release are realized simultaneously. Due to the unique properties of NO, enhanced antitumor efficacy of mild PTT based on BNN-Bi2S3 nanocomposites is achieved in vitro and in vivo. Mechanism studies reveal that the exogenous NO from BNN-Bi2S3 could not only impair the autophagic self-repairing ability of tumor cells in situ, but also diffuse to the surrounding cells to enhance the therapeutic effect. This work points out a strategy to overcome the difficulties in mild PTT, and has potentials for further exploitation of NO-sensitized synergistic cancer therapy.

PYNOD reduces microglial inflammation and consequent neurotoxicity upon lipopolysaccharides stimulation

PYNOD, a nod-like receptors (NLR)-like protein, was indicated to inhibit NF-κB activation, caspase-1-mediated interleukin (IL)-1β release and cell apoptosis in a dose-dependent manner. Exogenous addition of recombinant PYNOD to mixed glial cultures may suppress caspase-1 activation and IL-1β secretion induced by Aβ. However, to the best of our knowledge, there no study has focused on the immunoregulatory effects of PYNOD specifically in microglia. The present study aimed to explore the roles of PYNOD involved in the lipopolysaccharides (LPS)-induced microglial inflammation and consequent neurotoxicity. Murine microglial BV-2 cells were transfected with pEGFP-C2-PYNOD (0–5.0 µg/ml) for 24 h and incubated with or without LPS (1 µg/ml) for a further 24 h. Cell viability was determined using MTT assay and the secretion of nitric oxide (NO), IL-1β and caspase-1 was measured using the Griess method or ELISA. Protein expression levels of NF-κB p65 and inducible nitric oxide synthase (iNOS) were detected by immunofluorescent staining and/or western blot analysis. Co-culture of BV-2 cells with human neuroblastoma cell line SK-N-SH was performed in Transwell plates and the cell viability and apoptosis (using flow cytometry) of SK-N-SH cells were determined. Results indicated that PYNOD overexpression inhibited NO secretion and iNOS protein expression induced by LPS in BV-2 cells, with no detectable cytotoxicity. PYNOD overexpression also reduced the secretion of IL-1β and caspase-1 from BV-2 cells upon LPS stimulation. These effects were dose-dependent. Additionally, PYNOD overexpression prevented LPS-induced nuclear translocation of NF-κB p65 in BV-2 cells. The growth-inhibitory and apoptosis-promoting effects of BV-2 cells towards SK-N-SH cells were alleviated as a result of PYNOD overexpression. In conclusion, PYNOD may mitigate microglial inflammation and consequent neurotoxicity.

Functional Layer-by-Layer Thin Films of Inducible Nitric Oxide (NO) Synthase Oxygenase and Polyethylenimine: Modulation of Enzyme Loading and NO-Release Activity

Nitric oxide (NO) release counteracts platelet aggregation and prevents the thrombosis cascade in the inner walls of blood vessels. NO-release coatings also prevent thrombus formation on the surface of blood-contacting medical devices. Our previous work has shown that inducible nitric oxide synthase (iNOS) films release NO fluxes upon enzymatic conversion of the substrate l-arginine. In this work, we report on the modulation of enzyme loading in layer-by-layer (LbL) thin films of inducible nitric oxide synthase oxygenase (iNOSoxy) on polyethylenimine (PEI). The layer of iNOSoxy is electrostatically adsorbed onto the PEI layer. The pH of the iNOSoxy solution affects the amount of enzyme adsorbed. The overall negative surface charge of iNOSoxy in solution depends on the pH and hence determines the density of adsorbed protein on the positively charged PEI layer. We used buffered iNOSoxy solutions adjusted to pHs 8.6 and 7.0, while saline PEI solution was used at pH 7.0. Atomic force microscopy imaging of the outermost layer shows higher protein adsorption with iNOSoxy at pH 8.6 than with a solution of iNOSoxy at pH 7.0. Graphite electrodes with PEI/iNOSoxy films show higher catalytic currents for nitric oxide reduction mediated by iNOSoxy. The higher enzyme loading translates into higher NO flux when the enzyme-modified surface is exposed to a solution containing the substrate and a source of electrons. Spectrophotometric assays showed higher NO fluxes with iNOSoxy/PEI films built at pH 8.6 than with films built at pH 7.0. Fourier transform infrared analysis of iNOSoxy adsorbed on PEI at pH 8.6 and 7.0 shows structural differences of iNOSoxy in films, which explains the observed changes in enzymatic activity. Our findings show that pH provides a strategy to optimize the NOS loading and enzyme activity in NOS-based LbL thin films, which enables improved NO release with minimum layers of PEI/NOS.

Electrochemically Modulated Nitric Oxide Release From Flexible Silicone Rubber Patch: Antimicrobial Activity For Potential Wound Healing Applications

Herein, we report a novel design and the antimicrobial efficacy of a flexible nitric oxide (NO) releasing patch for potential wound healing applications. The compact sized polydimethylsiloxane (PDMS) planar patch generates NO via electrochemical reduction of nitrite ions mediated by a copper(II)-ligand catalyst using a portable power system and an internal gold coated stainless steel mesh working electrode. Patches are fabricated via soft lithography and 3-D printing. The devices can continuously release NO over 4 days and exhibit potent bactericidal effects on both Escherichia coli and Staphylococcus aureus. The device may provide an effective, safe, and less costly alternative for treating chronic wounds.

The effect of nitric oxide surface flux on the foreign body response to subcutaneous implants

Although the release of nitric oxide (NO) from biomaterials has been shown to reduce the foreign body response (FBR), the optimal NO release kinetics and doses remain unknown. Herein, polyurethane-coated wire substrates with varying NO release properties were implanted into porcine subcutaneous tissue for 3, 7, 21 and 42 d. Histological analysis revealed that materials with short NO release durations (i.e., 24 h) were insufficient to reduce the collagen capsule thickness at 3 and 6 weeks, whereas implants with longer release durations (i.e., 3 and 14 d) and greater NO payloads significantly reduced the collagen encapsulation at both 3 and 6 weeks. The acute inflammatory response was mitigated most notably by systems with the longest duration and greatest dose of NO release, supporting the notion that these properties are most critical in circumventing the FBR for subcutaneous biomedical applications (e.g., glucose sensors).

S-Nitroso-N-acetyl-D-penicillamine covalently linked to polydimethylsiloxane (SNAP-PDMS) for use as a controlled photoinitiated nitric oxide release polymer

Nitric oxide (NO) plays a critical role in the regulation of a wide variety of physiological processes. It is a potent inhibitor of platelet adhesion and aggregation, inhibits bacterial adhesion and proliferation, is implicated in mediating the inflammatory response toward implanted devices, plays a role in tumor growth and proliferation, and is a neurotransmitter. Herein, we describe the synthesis and NO-release properties of a modified polydimethylsiloxane that contains S-nitroso-N-acetyl-D-penicillamine covalently attached to the cross-linking agent (SNAP-DMS). Light from a C503B-BAN-CY0C0461 light-emitting diode (470 nm) was used as an external trigger to allow precise control over level and duration of NO release ranging from a surface flux of zero to approximately 3.5×10^-10 mol cm^-2 min^-1. SNAP-PDMS films stored in the dark released NO after 297 days, indicating the long-term stability of SNAP-PDMS.

Stöber Synthesis of Nitric Oxide-Releasing S-Nitrosothiol-Modified Silica Particles

We report the synthesis of S-nitrosothiol-modified silica particles capable of nitric oxide (NO) release. The thiol precursor modification to form S-nitrosothiol NO donors was introduced into the silica network via co-condensation of mercaptosilane and alkoxysilane precursors. Both the concentrations of reactants (i.e., water, ammonia, and silane) and the silane feed rate into the reaction proved important in the yield of monodisperse, spherical particles with tunable diameters ranging from 241-718 nm. Subsequent nitrosation resulted in NO storage approaching ~4.40 μmol NO mg(-1), as determined by total NO release. Behaving similar to low molecular weight S-nitrosothiol NO donors, the NO release from the macromolecular silica vehicles was influenced by light, temperature, and metal ions.

Analysis of responses to the Rho-kinase inhibitor Y-27632 in the pulmonary and systemic vascular bed of the rat

Responses to the Rho kinase inhibitor Y-27632 were investigated in the anesthetized rat. Under baseline conditions intravenous injections of Y-27632 decreased pulmonary and systemic arterial pressures and increased cardiac output. The decreases in pulmonary arterial pressures were enhanced when baseline tone was increased with U-46619, and under elevated tone conditions Y-27632 produced similar percent decreases in pulmonary and systemic arterial pressures. Injections of Y-27632 prevented and reversed the hypoxic pulmonary vasoconstrictor response. The increase in pulmonary arterial pressure in response to ventilation with a 10% O(2)-90% N(2) gas mixture was not well maintained during the period of hypoxic exposure. Treatment with the nitric oxide (NO) synthase (NOS) inhibitor nitro-l-arginine methyl ester (l-NAME) increased pulmonary arterial pressure and prevented the decline or fade in the hypoxic pulmonary vasoconstrictor response. The hypoxic pulmonary vasoconstrictor response was reversed by Y-27632 in control and in l-NAME-treated animals. The Rho kinase inhibitor attenuated increases in pulmonary arterial pressures in response to intravenous injections of serotonin, angiotensin II, and Bay K 8644. Y-27632, sodium nitrite, and BAY 41-8543, a guanylate cyclase stimulator, decreased pulmonary and systemic arterial pressures and vascular resistances in monocrotaline-treated rats. These data suggest that Rho kinase is involved in the regulation of baseline tone and in the mediation of pulmonary vasoconstrictor responses. The present data suggest that the hypoxic pulmonary vasoconstrictor response is modulated by the release of NO that mediates the nonsustained component of the response in the anesthetized rat. These data suggest that Rho kinase and NOS play important roles in the regulation of vasoconstrictor tone in physiological and pathophysiological states and that monocrotaline-induced pulmonary hypertension can be reversed by agents that inhibit Rho kinase, generate NO, or stimulate soluble guanylate cyclase.