Multifunctional Molecular Hybrids Photoreleasing Nitric Oxide: Advantages, Pitfalls, and Opportunities

The multifaceted role nitric oxide (NO) plays in human physiology and pathophysiology has opened new scenarios in biomedicine by exploiting this free radical as an unconventional therapeutic against important diseases. The difficulties in handling gaseous NO and the strict dependence of the biological effects on its doses and location have made the light-activated NO precursors, namely NO photodonors (NOPDs), very appealing by virtue of their precise spatiotemporal control of NO delivery. The covalent integration of NOPDs and additional functional components within the same molecular skeleton through suitable linkers can lead to an intriguing class of multifunctional photoactivatable molecular hybrids. In this Perspective, we provide an overview of the recent advances in these molecular constructs, emphasizing those merging NO photorelease with targeting, fluorescent reporting, and phototherapeutic functionalities. We will highlight the rational design behind synthesizing these molecular hybrids and critically describe the advantages, drawbacks, and opportunities they offer in biomedical research.

Simultaneous photoactivation of a fluoroquinolone antibiotic and nitric oxide with fluorescence reporting

The achievement of smart pharmaceuticals whose bioactivity can be spatiotemporally controlled by light stimuli is known as photopharmacology, an emerging area aimed at improving the therapeutic outcome and minimizing side effects. This is especially attractive for antibiotics, for which the inevitable development of multidrug resistance and the dwindling of new clinically approved drugs represent the main drawbacks. Here, we show that nitrosation of the fluoroquinolone norfloxacin (NF), a broad-spectrum antibiotic, leads to the nitrosated bioconjugate NF-NO, which is inactive at the typical minimum inhibitory concentration of NF. Irradiation of NF-NO with visible blue light triggers the simultaneous release of NF and nitric oxide (NO). The photouncaging process is accompanied by the revival of the typical fluorescence emission of NF, quenched in NF-NO, which acts as an optical reporter. This permits the real-time monitoring of the photouncaging process, even within bacteria cells where antibacterial activity is switched on exclusively upon light irradiation. The mechanism of photorelease seems to occur through a two-step hopping electron transfer mediated by the lowest triplet state of NF-NO and the phosphate buffer ions or aminoacids such as tyrosine. Considering the well-known role of NO as an "unconventional" antibacterial, the NF-NO conjugate may represent a potential bimodal antibacterial weapon activatable on demand with high spatio-temporal control.

Evaluation of Anticancer Activity of Nucleoside-Nitric Oxide Photo-Donor Hybrids

Herein, we report the synthesis of a new hybrid compound based on a 2'-deoxyuridine nucleoside conjugated with a NO photo-donor moiety (dU-t-NO) via CuAAC click chemistry. Hybrid dU-t-NO, as well as two previously reported 2'-deoxyadenosine based hybrids (dAdo-S-NO and dAdo-t-NO), were evaluated for their cytotoxic and cytostatic activities in selected cancer cell lines. dAdo-S-NO and dAdo-t-NO hybrids displayed higher activity with respect to dU-t-NO. All hybrids showed effective release of NO in the micromolar range. The photochemical behavior of the newly reported hybrid, dU-t-NO, was studied in the RKO colon carcinoma cell line, whereas the dAdo-t-NO hybrid was tested in both colon carcinoma RKO and hepatocarcinoma Hep 3B2.1-7 cell lines to evaluate the potential effect of NO released upon irradiation on cell viability. A customized irradiation apparatus for in vitro experiments was also designed.

Development of a solid-supported light-triggered nitric oxide donor

Nitric Oxide (NO) photocleavable donors are useful tools for interrogating nitric oxide signalling and have potential use in photopharmacological applications. There is currently intensive research into newer methods to improve NO release and kinetic profiles. Herein, we report the design and synthesis of a solid-supported photocleavable NO donor synthesized by ligating an N-nitroso photocleavable nitric oxide derivative to a TentaGel® polymer resin bead. Illumination with 365 nm light released nitric oxide that could be tracked via a turn-on fluorescence response (λex = 450 nm, λem = 545 nm) and measured using the Griess assay and diaminorhodamine derivatives. These beads were further shown to be compatible with living A549 cells and had the ability to deliver greater concentrations of nitric oxide to cells proximal to a bead versus cells at more distal locations within the same well.

Biomedical applications of stimuli-responsive "smart" interpenetrating polymer network hydrogels

In recent years, owing to the ongoing advancements in polymer materials, hydrogels have found increasing applications in the biomedical domain, notably in the realm of stimuli-responsive "smart" hydrogels. Nonetheless, conventional single-network stimuli-responsive "smart" hydrogels frequently exhibit deficiencies, including low mechanical strength, limited biocompatibility, and extended response times. In response, researchers have addressed these challenges by introducing a second network to create stimuli-responsive "smart" Interpenetrating Polymer Network (IPN) hydrogels. The mechanical strength of the material can be significantly improved due to the topological entanglement and physical interactions within the interpenetrating structure. Simultaneously, combining different network structures enhances the biocompatibility and stimulus responsiveness of the gel, endowing it with unique properties such as cell adhesion, conductivity, hemostasis/antioxidation, and color-changing capabilities. This article primarily aims to elucidate the stimulus-inducing factors in stimuli-responsive "smart" IPN hydrogels, the impact of the gels on cell behaviors and their biomedical application range. Additionally, we also offer an in-depth exposition of their categorization, mechanisms, performance characteristics, and related aspects. This review furnishes a comprehensive assessment and outlook for the advancement of stimuli-responsive "smart" IPN hydrogels within the biomedical arena. We believe that, as the biomedical field increasingly demands novel materials featuring improved mechanical properties, robust biocompatibility, and heightened stimulus responsiveness, stimuli-responsive "smart" IPN hydrogels will hold substantial promise for wide-ranging applications in this domain.

Recent advances on the development of NO-releasing molecules (NORMs) for biomedical applications

Nitric oxide (NO) is an important biological messenger as well as a signaling molecule that participates in a broad range of physiological events and therapeutic applications in biological systems. However, due to its very short half-life in physiological conditions, its therapeutic applications are restricted. Efforts have been made to develop an enormous number of NO-releasing molecules (NORMs) and motifs for NO delivery to the target tissues. These NORMs involve organic nitrate, nitrite, nitro compounds, transition metal nitrosyls, and several nanomaterials. The controlled release of NO from these NORMs to the specific site requires several external stimuli like light, sound, pH, heat, enzyme, etc. Herein, we have provided a comprehensive review of the biochemistry of nitric oxide, recent advancements in NO-releasing materials with the appropriate stimuli of NO release, and their biomedical applications in cancer and other disease control.

Upconversion nanoparticles@single-walled carbon nanotubes composites as efficient self-monitored photo-thermal agents

Conventional photothermal therapy (PTT) usually relies on a macroscopic heat source to raise the temperature of tissues to 41-45 °C, which not only kills the pathological cells but causes severe side effects on nearby normal tissues, thus reducing the accuracy of PTT. Here we successfully fabricated nanocomposites of NaYF4:Yb3+,Tm3+@NaYF4:Yb3+@SiO2-SWCNTs, in which the upconversion nanoparticles (UCNPs) serve as real-time temperature-feedback moiety and the single-walled carbon nanotubes (SWCNTs) serve as efficient nano-heaters. The sample displays an excellent photothermal conversion capacity, i.e., the temperature of the aqueous dispersion increases from 23.3 °C up to 60.1 °C under 980 nm excitation due to the intense absorption and highly efficient heat generation of SWCNTs. Meanwhile, the temperature of the nanocomposites is monitored in real time based on the fluorescent intensity ratio of UCNPs. The in-vitro experiments demonstrate that the temperature of the nanocomposites at tissue injection of 1 mm can reach PTT temperature of 42.2 °C with a facile surrounding temperature of 36.2 °C under moderate laser power (980 nm, 2.0 W cm-2). These results provide a novel design for multifunctional nanocomposites that enable safe and controlled PTT.

Recent Advances in Functional Nanomaterials for Catalytic Generation of Nitric Oxide: A Mini Review

As a gaseous second messenger, nitric oxide (NO) plays an important role in a series of signal pathways. Research on the NO regulation for various disease treatments has aroused wide concern. However, the lack of accurate, controllable, and persistent release of NO has significantly limited the application of NO therapy. Profiting from the booming development of advanced nanotechnology, a mass of nanomaterials with the properties of controllable release have been developed to seek new and effective NO nano-delivery approaches. Nano-delivery systems that generate NO through catalytic reactions exhibit unique superiority in terms of precise and persistent release of NO. Although certain achievements have been made in the catalytically active NO delivery nanomaterials, some basic but critical issues, such as the concept of design, are of low attention. Herein, an overview of the generation of NO through catalytic reactions and the design principles of related nanomaterials are summarized. Then, the nanomaterials that generate NO through catalytic reactions are classified. Finally, the bottlenecks and perspectives are also discussed in depth for the future development of catalytical NO generation nanomaterials.

Thiol-Ene Photo-Click Hydrogels with Tunable Mechanical Properties Resulting from the Exposure of Different -Ene Moieties through a Green Chemistry

Temperature and light responsiveness are widely exploited stimuli to tune the physico-chemical properties of double network hydrogels. In this work, new amphiphilic poly(ether urethane)s bearing photo-sensitive moieties (i.e., thiol, acrylate and norbornene functionalities) were engineered by exploiting the versatility of poly(urethane) chemistry and carbodiimide-mediated green functionalization procedures. Polymers were synthesized according to optimized protocols maximizing photo-sensitive group grafting while preserving their functionality (approx. 1.0 × 1019, 2.6 × 1019 and 8.1 × 1017 thiol, acrylate and norbornene groups/gpolymer), and exploited to prepare thermo- and Vis-light-responsive thiol-ene photo-click hydrogels (18% w/v, 1:1 thiol:ene molar ratio). Green light-induced photo-curing allowed the achievement of a much more developed gel state with improved resistance to deformation (ca. 60% increase in critical deformation, γL). Triethanolamine addition as co-initiator to thiol-acrylate hydrogels improved the photo-click reaction (i.e., achievement of a better-developed gel state). Differently, L-tyrosine addition to thiol-norbornene solutions slightly hindered cross-linking, resulting in less developed gels with worse mechanical performances (~62% γL decrease). In their optimized composition, thiol-norbornene formulations resulted in prevalent elastic behavior at lower frequency compared to thiol-acrylate gels due to the formation of purely bio-orthogonal instead of heterogeneous gel networks. Our findings highlight that exploiting the same thiol-ene photo-click chemistry, a fine tuning of the gel properties is possible by reacting specific functional groups.

Three-in-one: exploration of co-encapsulation of cabazitaxel, bicalutamide and chlorin e6 in new mixed cyclodextrin-crosslinked polymers

Three-in-one: a single bCyD polymer easily prepared in water is used to co-encapsulate cabazitaxel and bicalutamide with chlorin e6 affording a nanoplatform to implement multimodal cancer therapy.

UV-A,B,C Emitting Persistent Luminescent Materials

The nearly dormant field of persistent luminescence has gained fresh impetus after the discovery of strontium aluminate persistent luminescence phosphor in 1996. Several efforts have been put in to prepare efficient, long decay, persistent luminescent materials which can be used for different applications. The most explored among all are the materials which emit in the visible wavelength region, 400-650 nm, of the electromagnetic spectrum. However, since 2014, the wavelength range is extended further above 650 nm for biological applications due to easily distinguishable signal between luminescent probe and the auto-fluorescence. Recently, UV-emitting persistent materials have gained interest among researchers' due to their possible application in information storage, phototherapy and photocatalysis. In the present review, we summarize these recent developments on the UV-emitting persistent luminescent materials to motivate young minds working in the field of luminescent materials.

Nanomaterial-enabled photothermal-based solar water disinfection processes: Fundamentals, recent advances, and mechanisms

The pathogenic microorganisms in water pose a great threat to human health. Photothermal and photothermocatalytic disinfection using nanomaterials (NPs) has offered a promising and effective strategy to address the challenges in solar water disinfection (SODIS), especially in the point-of-use operations. This review aims at providing comprehensive and state-of-the-art knowledge of photothermal-based disinfection by NPs. The fundamentals and principles of photothermal-based disinfection were first introduced. Then, recent advances in developing photothermal/photothermocatalytic catalysts were systematically summarized. The light-to-heat conversion and disinfection performance of a large variety of photothermal materials were presented. Given the complicated mechanisms of photothermal-based disinfection, the attacks from reactive oxygen species and heat, the destruction of bacterial cells, and the antibacterial effects of released metal ions were highlighted. Finally, future challenges and opportunities associated with the development of cost-effective photothermal/photothermocatalytic disinfection systems were outlined. This review will provide guidance in designing future NPs and inspire more research efforts from environmental nano-communities to move towards practical water disinfection operations.

Thermo- and Light-Responsive Polymer-Coated Magnetic Nanoparticles as Potential Drug Carriers

A series of thermo- and light-responsive copolymers of poly (N-isopropylacrylamide) (PNIPAM) and 6-[4-(4-methoxy phenyl azo)-phenoxyl-hexyl methacrylate) (AzoMA) (PNIPAM-b-PAzoMA) were synthesized via reversible addition–fragmentation chain transfer (RAFT) radical polymerization. The resulting copolymers had a narrow molecular weight distribution range of 1.06–1.24, in which Mn changed regularly with the monomer concentration. Subsequently, the diblock copolymers were successfully modified on the surface of iron oxide nanoparticles through the interaction between the chemical bonds to prepare Fe3O4@(PNIPAM-b-PAzoMA) nanoparticles. The size of fabricated nanoparticles with excellent thermo-sensitivity and photo-sensitivity was controlled at about 40–50 nm. Cell viability assays suggested that the nanoparticles showed no significant cytotoxicity and potential drug delivery in the tumor microenvironment.

-808nm-Activated Ca2+Doped Up-conversion Nanoparticles That Release NO Inducing Liver Cancer Cell (HepG2) Apoptosis

A near-infrared (NIR) light-triggered release method for nitric oxide (NO) was developed utilizing core/shell NaYF4: Tm/Yb/Ca@NaGdF4: Nd/Yb up-conversion nanoparticles (UCNPs) bearing a mesoporous silica (mSiO2) shell loaded with the NO donor S-nitroso-N-acetyl-DL-penicillamine (SNAP). To avoid overheating in biological samples, Nd3+ was chosen as a sensitizer, Yb3+ ions as the bridging sensitizer, and Tm3+ ions as UV-emissive activator while co-doping with Ca2+ was done to enhance the luminescence of the activator Tm3+. NO release from SNAP was triggered by an NIR-UV up-conversion process, initiated by 808 nm light absorbed by the Nd3+ ions. NO release was confirmed by the Griess method. Under 808 nm irradiation, the viability of the liver cancer cell line HepG2 significantly decreased with increasing UCNPs@mSiO2-SNAP concentration. For a UCNPs@mSiO2-SNAP concentration of 200 μg/ml, the cell survival probability was 47 %. These results demonstrate that UCNPs@mSiO2-SNAP can induce the release of apoptosis-inducing NO by NIR irradiation.

Nitric Oxide Photoreleasers with Fluorescent Reporting

Nitric oxide (NO) plays a multifaceted role in human physiology and pathophysiology, and its controlled delivery has great prospects in therapeutic applications. The light-activated uncaging of NO from NO caging compounds allows this free radical to be released with accurate control of site and dosage, which strictly determine its biological effects. Molecular constructs able to activate fluorescence concomitantly to NO release offer the important advantage of easy and real-time tracking of the amount of NO uncaged in a non-invasive fashion even in the cell environment. This contribution provides an overview of the advances in photoactivatable NO releasers bearing fluorescent reporting functionalities achieved in our and other laboratories, highlighting the rationale design and their potential therapeutic applications.

A generator of peroxynitrite activatable with red light

The generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) as “unconventional” therapeutics with precise spatiotemporal control by using light stimuli may open entirely new horizons for innovative therapeutic modalities. Among ROS and RNS, peroxynitrite (ONOO⁻) plays a dominant role in chemistry and biology in view of its potent oxidizing power and cytotoxic action. We have designed and synthesized a molecular hybrid based on benzophenothiazine as a red light-harvesting antenna joined to an N-nitroso appendage through a flexible spacer. Single photon red light excitation of this molecular construct triggers the release of nitric oxide (˙NO) and simultaneously produces superoxide anions (O₂˙⁻). The diffusion-controlled reaction between these two radical species generates ONOO⁻, as confirmed by the use of fluorescein-boronate as a highly selective chemical probe. Besides, the red fluorescence of the hybrid allows its tracking in different types of cancer cells where it is well-tolerated in the dark but induces remarkable cell mortality under irradiation with red light in a very low concentration range, with very low light doses (ca. 1 J cm⁻²). This ONOO⁻ generator activatable by highly biocompatible and tissue penetrating single photon red light can open up intriguing prospects in biomedical research, where precise and spatiotemporally controlled concentrations of ONOO⁻ are required.

Excitation of a molecular hybrid with highly biocompatible red light generates cytotoxic peroxynitrite, produces red fluorescence useful for cell tracking and induces remarkable cancer cell death at very low concentrations and very low light doses.

Understanding of [RuL(ONO)]n+ acting as nitric oxide precursor, a theoretical study of ruthenium complexes of 1,4,8,11-tetraazacyclo- tetradecane having different substituents: How spin multiplicity influences bond angle and bond lengths (Ru-O-NO) in releasing of NO

Generation of nitric oxide has been a great interest in cell biology as it involves a wide range of physiological functions including the blood pressure control; thus the exploitation of ruthenium chemistry has been motivated in biochemical and clinical points of view. Herein, the structural and electronic properties of ruthenium(II) complexes of 1,4,8,11-tetraazacyclotetradecane containing pyridyl, imidazole and benzimidazole (L¹, L², L³) were analyzed theoretically in the context of how spin multiplicity plays a crucial role influencing the NO release from the LRu-ONO moiety. The results show that β-cleavage of nitrito in the complex motivates the release of NO as it depends highly on total spin multiplicity of metal ion altering significantly the geometrical parameters; particularly, a decrease of bond length of Ru-ONO is highly associated with an increase of RuO-NO bond distance that correlates with the decrease of the Ru-O-NO bond angle ultimately leading to the release of NO; apparently, the bending nature of Ru-O-NO defines its release from the complex. This is consistent with orbital energy (d_x²-_y²) where the stabilization of axial Ru-O bond in the complex was observed, and proved by molecular orbital studies. In the excitation of the complex (singlet to triplet or singlet to quintet), the NO release has been facilitated, agreeing with the Gibbs free energy data where a lower energy for NO release was obtained compared to other types of excitations. In the calculated electronic spectra, a visible broad band with relatively high intensity for [RuL¹ONO]⁺ was observed, agreeing approximately with reported experimental results.

Near-infrared light and magnetic field dual-responsive porous silicon-based nanocarriers to overcome multidrug resistance in breast cancer cells with enhanced efficiency

The development of drug delivery systems based on external stimuli-responsive nanocarriers is important to overcome multidrug resistance in breast cancer cells. Herein, iron oxide/gold (Fe3O4/Au) nanoparticles were first fabricated via a simple hydrothermal reaction, and subsequently loaded into porous silicon nanoparticles (PSiNPs) via electrostatic interactions to construct PSiNPs@(Fe3O4/Au) nanocomposites. The as-prepared PSiNPs@(Fe3O4/Au) nanocomposites exhibited excellent super-paramagnetism, photothermal effect, and T2-weight magnetic resonance imaging capability. In particular, with the help of a magnetic field, the cellular uptake of PSiNPs@(Fe3O4/Au) nanocomposites was significantly enhanced in drug-resistant breast cancer cells. Moreover, PSiNPs@(Fe3O4/Au) nanocomposites as carriers showed a high loading and NIR light-triggered release of anticancer drugs. Based on the synergistic effect of magnetic field-enhanced cellular uptake and NIR light-triggered intracellular release, the amount of anticancer drug carried by PSiNPs@(Fe3O4/Au) nanocarriers into the nuclei of drug-resistant breast cancer cells sharply increased, accompanied by improved chemo-photothermal therapeutic efficacy. Finally, PSiNPs@(Fe3O4/Au) nanocomposites under the combined conditions of magnetic field attraction and NIR light irradiation also showed improved anticancer drug penetration and accumulation in three-dimensional multicellular spheroids composed of drug-resistant breast cancer cells, leading to a better growth inhibition effect. Overall, the fabricated PSiNPs@(Fe3O4/Au) nanocomposites demonstrated great potential for the therapy of multidrug-resistant breast cancer in future.

On-Demand Reversible UV-Triggered Interpenetrating Polymer Network-Based Drug Delivery System Using the Spiropyran-Merocyanine Hydrophobicity Switch

A reversible switchable on-demand UV-triggered drug delivery system (DDS) based on interpenetrating polymer networks (IPNs) with silicone as the host polymer and spiropyran (SP)-functionalized guest polymer is designed and demonstrated. The photo-responsive IPNs provide a new triggered drug delivery concept as they exploit the change in intermolecular interactions (work of adhesion) among the drug, matrix, and solvent when the incorporated hydrophobic SP moieties transform into the hydrophilic merocyanine form upon light irradiation without degradation and disruption of the DDS. The change in how the copolymer composition (hydrophilicity and content) and the lipophilicity of the drug (log P) affect the release profile was investigated. A thermodynamic model, based on Hansen solubility parameters, was developed to design and optimize the polymer composition of the IPNs to obtain the most efficient light-triggered drug release and suppression of the premature release. The developed IPNs showed excellent result for dopamine, l-dopa, and prednisone with around 90-95% light-triggered release. The model was applied to study the release behavior of drugs with different log P and to estimate if the light-induced hydrophobic-to-hydrophilic switch can overcome the work of adhesion between polymers and drugs and hence the desorption and release of the drugs. To the best of our knowledge, this is the first time that work of adhesion is used for this aim. Comparing the result obtained from the model and experiment shows that the model is useful for evaluating and estimating the release behavior of specific drugs merocyanine, IPN, DDS, and spiropyran.

Photocage-Selective Capture and Light-Controlled Release of Target Proteins

Photochemical transformations enable exquisite spatiotemporal control over biochemical processes; however, methods for reliable manipulations of biomolecules tagged with biocompatible photo-sensitive reporters are lacking. Here we created a high-affinity binder specific to a photolytically removable caging group. We utilized chemical modification or genetically encoded incorporation of noncanonical amino acids to produce proteins with photocaged cysteine or selenocysteine residues, which were used for raising a high-affinity monoclonal antibody against a small photoremovable tag, 4,5-dimethoxy-2-nitrobenzyl (DMNB) group. Employing the produced photocage-selective binder, we demonstrate selective detection and immunoprecipitation of a variety of DMNB-caged target proteins in complex biological mixtures. This combined orthogonal strategy permits photocage-selective capture and light-controlled traceless release of target proteins for a myriad of applications in nanoscale assays.

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The first high-affinity monoclonal antibody specific for a popular photocaging group

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A new tool for selective detection of DMNB-tagged proteins in complex mixtures

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Enables non-covalent capture of native proteins with surface-exposed DMNB groups

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Orthogonal protein manipulation by photocage-selective capture and photolytic release

Photo-Based Nanomedicines Using Polymeric Systems in the Field of Cancer Imaging and Therapy

The use of photo-based nanomedicine in imaging and therapy has grown rapidly. The property of light in converting its energy into different forms has been exploited in the fields of optical imaging (OI) and phototherapy (PT) for diagnostic and therapeutic applications. The development of nanotechnology offers numerous advantages to overcome the challenges of OI and PT. Accordingly, in this review, we shed light on common photosensitive agents (PSAs) used in OI and PT; these include fluorescent and bioluminescent PSAs for OI or PT agents for photodynamic therapy (PDT) and photothermal therapy (PTT). We also describe photo-based nanotechnology systems that can be used in photo-based diagnostics and therapies by using various polymeric systems.

Endoplasmic Reticulum Stress Provocation by Different Nanoparticles: An Innovative Approach to Manage the Cancer and Other Common Diseases

A proper execution of basic cellular functions requires well-controlled homeostasis including correct protein folding. Endoplasmic reticulum (ER) implements such functions by protein reshaping and post-translational modifications. Different insults imposed on cells could lead to ER stress-mediated signaling pathways, collectively called the unfolded protein response (UPR). ER stress is also closely linked with oxidative stress, which is a common feature of diseases such as stroke, neurodegeneration, inflammation, metabolic diseases, and cancer. The level of ER stress is higher in cancer cells, indicating that such cells are already struggling to survive. Prolonged ER stress in cancer cells is like an Achilles' heel, if aggravated by different agents including nanoparticles (NPs) may be exhausted off the pro-survival features and can be easily subjected to proapoptotic mode. Different types of NPs including silver, gold, silica, graphene, etc. have been used to augment the cytotoxicity by promoting ER stress-mediated cell death. The diverse physico-chemical properties of NPs play a great role in their biomedical applications. Some special NPs have been effectively used to address different types of cancers as these particles can be used as both toxicological or therapeutic agents. Several types of NPs, and anticancer drug nano-formulations have been engineered to target tumor cells to enhance their ER stress to promote their death. Therefore, mitigating ER stress in cancer cells in favor of cell death by ER-specific NPs is extremely important in future therapeutics and understanding the underlying mechanism of how cancer cells can respond to NP induced ER stress is a good choice for the development of novel therapeutics. Thus, in depth focus on NP-mediated ER stress will be helpful to boost up developing novel pro-drug candidates for triggering pro-death pathways in different cancers.

A thermoresponsive gel photoreleasing nitric oxide for potential ocular applications

We report herein the design, preparation, characterization and biological evaluation of a thermoresponsive gel based on binary mixtures of Pluronic® co-polymers F127 and P123, the latter being covalently functionalized with a nitric oxide (NO) photodonor (NOPD). The weight ratio between the two polymeric components is optimized in order to observe gelation of their saline water solution in the range of 32-35 °C, in order to exploit the therapeutic properties of NO for potential ocular applications. Rheological measurements were performed to evaluate the gelation temperature and, hence, to select a co-polymer mixture specifically appropriate for the reference application. Integration of the NOPD into the polymeric scaffold does not affect its rheological and spectroscopic properties, making it a good absorber of visible light both in solution and in the gel phase. Irradiation of the saline solution of the polymeric components with visible light triggers NO release, which occurs with an efficiency of more than one order of magnitude faster than that observed for the isolated NOPD. The polymeric system fully preserves such photobehavior after gelation as demonstrated by the effective NO photorelease from the gel matrix and its diffusion in the supernatant upon illumination. The gel is well-tolerated in both dark and light conditions by corneal cells, while being able to induce growth inhibition towards Staphylococcus aureus under visible light irradiation and has high moduli which can contribute to an adequate retention time within the eyes.

Effect of actively targeted copolymer coating on solid tumors eradication by gold nanorods-induced hyperthermia

Efforts in the field of anticancer therapy are increasingly focusing on the development of localized and selective treatments. Photothermal therapy (PTT) can lead to a spatially confined death of cancer cells, exploiting an increasing in temperature generated after UV-NIR irradiation of peculiar materials. Herein, a new actively targeted gold-based drug delivery system, named PHEA-LA-Fol-AuNRs/Iri, was explored for hyperthermia and chemotherapy colon cancer treatment. Gold nanorods were stabilized using a folate-derivative of α,β-poly(N-2-hydroxyethyl)-D,L-aspartamide (PHEA-LA-PEG-FA) as coating agent and then loaded with the antineoplastic drug irinotecan (Iri). The efficacy of empty and irinotecan-bearing systems was investigated in vitro on human colon cancer (HCT116) cell line, as well as in vivo, employing a xenograft mouse model of colon cancer. After laser treatment, both nanostructures tested induced a considerable deceleration in tumor growth overtime, achieving the total eradication of the cancer when the nanosystems produced were intratumorally administered. Biodistribution data showed that the polymer coated nanorods were able to preferentially accumulate in the tumor site. Considering the excellent stability in aqueous media, the capacity to reach the tumor site and, finally, the in vivo efficacy, PHEA-LA-Fol-AuNRs/Iri might be recommended as an effective tool in the chemotherapy and PTT of colon cancer.

In-situ sulfuration of Cu-based metal-organic framework for rapid near-infrared light sterilization

Some new kinds of antibiotics-free antibacterial agents are required to deal with bacterial infections due to the occurrence of drug-resistance. In this work, Cu-based metal-organic framework (HKUST-1) embedded with CuS NPs were fabricated via a simple in-situ sulfuration process. The synthesized MOFs exhibited an highly effective disinfection efficacy of 99.70 % and 99.80 % against Staphylococcus aureus and Escherichia coli within 20 min irradiation of near-infrared (NIR) light, respectively, which was ascribed to the cooperative effects of photodynamic and photothermal effects of the composites. A certain amount of Cu²⁺ ions of the MOFs were reacted to form CuS NPs, which endowed this composite with outstanding photocatalytic and photothermal performance during NIR light irradiation. Moreover, HKUST-1 that composed of low toxic organic ligand 1,3,5-benzenetricarboxylic acid (H₃BTC) coordinating copper ions could be a controllable carrier that imposed certain constraint on the NPs. Hence, these CuS@HKUST-1 would be a promising bioplatform for rapid bacteria-killing.

Graphene Oxide Composite for Selective Recognition, Capturing, Photothermal Killing of Bacteria over Mammalian Cells

The multifunctional photothermal therapy (PTT) platform with the ability to selectively kill bacteria over mammalian cells has received widespread attention recently. Herein, we prepared graphene oxide-amino(polyethyleneglycol) (GO-PEG-NH2) while using the hydrophobic interaction between heptadecyl end groups of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[amino(polyethyleneglycol)] (DSPE-PEG-NH2) and graphene oxide (GO). Based on GO-PEG-NH2, the versatile PTT system was constructed with simultaneous selective recognition, capturing, and photothermal killing of bacteria. When the cells undergo bacterial infection, owing to the poly(ethylene glycol) (PEG) chains and positively charged amino groups, GO-PEG-NH2 can specifically recognize and capture bacteria in the presence of cells. Meanwhile, the stable photothermal performance of GO-PEG-NH2 enables the captured bacteria to be efficiently photothermally ablated upon the irradiation of 808 nm laser. Besides, the GO-PEG-NH2 is highly stable in various biological media and it exhibits low cytotoxicity, suggesting that it holds great promise for biological applications. This work provides new insight into graphene-based materials as a PTT agent for the development of new therapeutic platforms.

Nanoscale lipid vesicles functionalized with a nitro-aniline derivative for photoinduced nitric oxide (NO) delivery

Nanoscale vesicles functionalized with a nitric oxide (NO) releasing molecule 4-nitro-3-(trifluoromethyl)aniline have been reported. The new NO-nano-vesicular donor material shows an effective photo-release of NO upon irradiation with blue light at 410 nm. The kinetics of NO release has been monitored by using simple spectroscopic techniques such as UV-Vis and fluorescence methods. Colorimetric Griess assay and fluorescence DAF assay have been used for the detection and quantification of NO released from vesicles. This new vesicular nanoscale NO donor has the advantages of facile preparation in water, capable of releasing NO in a pure aqueous medium, photo-controlled NO release, bio-compatibility and capacity to modulate the NO donor loading to achieve an essential amount of NO.

Enhancing doxorubicin anticancer activity with a novel polymeric platform photoreleasing nitric oxide

Combination of Doxorubicin with light-regulated NO release achieved through formulation strategy of tailored polymeric conjugate nanoparticles may open new treatment modalities to improve cancer therapies.

Effects of bovine serum albumin (BSA) on the excited-state properties of meso-tetrakis(sulfonatophenyl) porphyrin (TPPS4)

To infer changes in the photophysical properties of porphyrins due to complexation with albumin, a combination of Z-scan and conventional spectroscopic techniques was employed. We measured the characteristics of excited states of meso-tetrakis(sulfonatophenyl) porphyrin bound to bovine serum albumin and observed that the binding reduces the intersystem crossing quantum yield and increases the internal conversion one. A reverse saturable absorption process was observed in the nanosecond timescale. These results are important for prediction of the efficiency of this complex in medical and optical applications, because associating porphyrins to proteins enables better accumulation in tumors and improves its stability in optical devices, but at the same time, decreases its triplet quantum yield.

Contact Lenses Delivering Nitric Oxide under Daylight for Reduction of Bacterial Contamination

Ocular infection due to microbial contamination is one of the main risks associated with the wearing of contact lens, which demands novel straightforward strategies to find reliable solutions. This contribution reports the preparation, characterization and biological evaluation of soft contact lenses (CL) releasing nitric oxide (NO), as an unconventional antibacterial agent, under daylight exposure. A tailored NO photodonor (NOPD) was embedded into commercial CL leading to doped CL with an excellent optical transparency (transmittance = 100%) at λ ≥ 450 nm. The NOPD results homogeneously distributed in the CL matrix where it fully preserves the photobehavior exhibited in solution. In particular, NO release from the CL and its diffusion in the supernatant physiological solution is observed upon visible light illumination. The presence of a blue fluorescent reporting functionality into the molecular skeleton of the NOPD, which activates concomitantly to the NO photorelease, allows the easy monitoring of the NO delivery in real-time and confirms that the doped CL work under daylight exposure. The NO photoreleasing CL are well-tolerated in both dark and light conditions by corneal cells while being able to induce good growth inhibition of Staphylococcus aureus under visible light irradiation. These results may pave the way to further engineering of the CL with NOPD as innovative ocular devices activatable by sunlight.

"Three-Bullets" Loaded Mesoporous Silica Nanoparticles for Combined Photo/Chemotherapy

This contribution reports the design, preparation, photophysical and photochemical characterization, as well as a preliminary biological evaluation of mesoporous silica nanoparticles (MSNs) covalently integrating a nitric oxide (NO) photodonor (NOPD) and a singlet oxygen (¹O₂) photosensitizer (PS) and encapsulating the anticancer doxorubicin (DOX) in a noncovalent fashion. These MSNs bind the NOPD mainly in their inner part and the PS in their outer part in order to judiciously exploit the different diffusion radius of the cytotoxic NO and ¹O₂. Furthermore this silica nanoconstruct has been devised in such a way to permit the selective excitation of the NOPD and the PS with light sources of different energy in the visible window. We demonstrate that the individual photochemical performances of the photoactive components of the MSNs are not mutually affected, and remain unaltered even in the presence of DOX. As a result, the complete nanoconstruct is able to deliver NO and ¹O₂ under blue and green light, respectively, and to release DOX under physiological conditions. Preliminary biological results performed using A375 cancer cells show a good tolerability of the functionalized MSNs in the dark and a potentiated activity of DOX upon irradiation, due to the effect of the NO photoreleased.

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.

Photon-Responsive Antibacterial Nanoplatform for Synergistic Photothermal-/Pharmaco-Therapy of Skin Infection

Abuse of antibiotics and their residues in the environment results in the emergence and prevalence of drug-resistant bacteria and leads to serious health problems. Herein, a photon-controlled antibacterial platform that can efficiently kill drug-resistant bacteria and avoid the generation of new bacterial resistance was designed by encapsulating black phosphorus quantum dots (BPQDs) and pharmaceuticals inside a thermal-sensitive liposome. The antibacterial platform can release pharmaceuticals in a spatial-, temporal-, and dosage-controlled fashion because the BPQDs can delicately generate heat under near-infrared light stimulation to disrupt the liposome. This user-defined delivery of drug can greatly reduce the antibiotic dosage, thus avoiding the indiscriminate use of antibiotics and preventing the generation of superbugs. Moreover, by coupling the photothermal effect with antibiotics, this antibacterial platform achieved a synergistic photothermal-/pharmaco-therapy with significantly improved antibacterial efficiency toward drug-resistant bacteria. The antibacterial platform was further employed to treat antibiotic-resistant bacteria-caused skin abscess and it displayed excellent antibacterial activity in vivo, promising its potential clinical applications. Additionally, the antibacterial mechanism was further investigated. The developed photon-controlled antibacterial platform can open new possibilities for avoiding bacterial resistance and efficiently killing antibiotic-resistant bacteria, making it valuable in fields ranging from antiinfective therapy to precision medicine.

A phototherapeutic fluorescent β-cyclodextrin branched polymer delivering nitric oxide

A water soluble b-CD-branched polymer covalently binds a fluorescein moiety for imaging and a NO photodonor for therapy that can be operated in parallel upon visible light excitation.

Comparing photoswitching of acrylate or methacrylate polymers conjugated with donor–acceptor Stenhouse adducts

Polymers with donor–acceptor Stenhouse adduct (DASA) groups were synthesized using RAFT methods to evaluate the effect of polymer length (20 vs. 100 DP units) and backbone rigidity (acrylate and methacrylate blocks).

Synthesis of Light-Responsive Pyrene-Based Polymer Nanoparticles via Polymerization-Induced Self-Assembly

The use of an in situ, one-pot polymerization-induced self-assembly method to synthesize light-responsive pyrene-containing nanoparticles is reported. The strategy is based on the chain extension of a hydrophilic macromolecular chain transfer agent, poly(oligo(ethylene glycol) methyl ether methacrylate), using a light-responsive monomer, 1-pyrenemethyl methacrylate (PyMA), via a reversible addition-fragmentation chain transfer dispersion polymerization; yielding nanoparticles of various morphologies (spherical micelles and worm-like micelles). In this process, addition of comonomers, such as butyl methacrylate (BuMA) or methyl methacrylate (MMA), are required to obtain high PyMA monomer conversion (>80% in 24 h). The addition of comonomers reduces the π-π stacking of the pyrene moieties, which facilitates the diffusion of monomers in the nanoparticle core. The addition of BuMA (as a comonomer) offers P(PyMA-co-BuMA) core-forming chains with high mobility that enables the reorganization of chains and then the evolution of morphology to form vesicles. In contrast, when MMA comonomer is used, kinetically trapped spheres are obtained; this is due to the low mobility of the core-forming chains inhibiting in situ morphological evolution. Finally, the UV-light-induced dissociation of these light-responsive nanoparticles due to the gradual cleavage of the pyrene moieties and the subsequent hydrophobic-to-hydrophilic transitions of the core-forming blocks is demonstrated.

Near-infrared light triggered drug release from mesoporous silica nanoparticles

Stimuli triggered drug delivery systems enable controlled release of drugs at the optimal space and time, thus achieving optimal therapeutic effects. As one of the most important stimuli used in bioapplications, near-infrared (NIR) light possesses unique advantages such as deep tissue penetration with minimum auto-fluorescence & tissue scattering and high biosafety. Mesoporous silica nanoparticles (MSNs) are one of the most studied nanocarriers; apart from having a high surface area and large pore volume for loading of drugs, they can be easily functionalized with inorganic nanomaterials and stimuli responsive polymers or organic switch molecules, creating possibilities for designing complex stimuli triggered drug delivery systems. Considering the high tissue penetration depth of NIR light and the unique mesoporous structure of MSNs, NIR responsive inorganic nanoparticle functionalized MSNs can be further combined with stimuli responsive materials to form smart "nano-devices" for controlled drug delivery toward tumors, and to date much progress has been made. In this article, recent advances in the design of NIR triggered mesoporous silica drug delivery systems are systematically summarized and some outstanding studies are highlighted. We will also discuss the shortcomings, challenges and opportunities in the field.

Recent Progress in Metal-Based Nanoparticles Mediated Photodynamic Therapy

Photodynamic therapy (PDT) is able to non-invasively treat and diagnose various cancers and nonmalignant diseases by combining light, oxygen, and photosensitizers (PSs). However, the application of PDT is hindered by poor water solubility and limited light-penetration depth of the currently available photosensitizers (PSs). Water solubility of PSs is crucial for designing pharmaceutical formulation and administration routes. Wavelength of light source at visible range normally has therapeutic depth less than 1 mm. In this review, focus is on the recent research progress of metal-based nanoparticles being applied in PDT. The potential toxicity of these nanoscales and future directions are further discussed.