Nano-carrier DMSN for effective multi-antigen vaccination against SARS-CoV-2.

The pandemic caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has had a profound impact on the global health and economy. While mass vaccination for herd immunity is effective, emerging SARS-CoV-2 variants can evade spike protein-based COVID-19 vaccines. In this study, we develop a new immunization strategy by utilizing a nanocarrier, dendritic mesoporous silica nanoparticle (DMSN), to deliver the receptor-binding domain (RBD) and conserved T-cell epitope peptides (DMSN-P-R), aiming to activate both humoral and cellular immune responses in the host. The synthesized DMSN had good uniformity and dispersion and showed a strong ability to load the RBD and peptide antigens, enhancing their uptake by antigen-presenting cells (APCs) and promoting antigen delivery to lymph nodes. The DMSN-P-R vaccine elicited potent humoral immunity, characterized by highly specific RBD antibodies. Neutralization tests demonstrated significant antibody-mediated neutralizing activity against live SARS-CoV-2. Crucially, the DMSN-P-R vaccine also induced robust T-cell responses that were specifically stimulated by the RBD and conserved T-cell epitope peptides of SARS-CoV-2. The DMSN demonstrated excellent biocompatibility and biosafety in vitro and in vivo, along with degradability. Our study introduces a promising vaccine strategy that utilizes nanocarriers to deliver a range of antigens, effectively enhancing both humoral and cellular immune responses to prevent virus transmission.

Flower-like mesoporous silica nanoparticles as an antigen delivery platform to promote systemic immune response.

Virus-like particles (VLPs), a kind of superior subunit vaccine, are assembled from the viral structural proteins with similar capsids to viruses. However, the efficiency of cell uptake is not satisfactory. We prepared flower-like mesoporous silica nanoparticles (SiNPs) with large pore channels and interior cavities to solve the problem. The highly loaded VLPs-SiNPs composites not only enhanced the stability of VLPs, but also delivered antigen to cells and improved the cellular uptake efficiency. Compared with naked VLPs, mice intramuscularly immunized with the VLPs-SiNPs composite induced higher specific antibodies, greater lymphocyte activation and higher level of cytokine secretion. Moreover, the VLPs-SiNPs composite as vaccine also promoted mucosal immune response through intranasal immune pathway. Therefore, the VLPs-SiNPs enable to induce strong cellular, humoral, and slight mucosal immune response through different immunization routes. These results are potentially useful for vaccine formulations and may provide further reference for vaccine design and delivery systems.

A naphthalimide-based lysosome-targeting fluorescent probe for the selective detection and imaging of endogenous peroxynitrite in living cells.

The morpholine (ML) group can be used as a targeting unit for lysosomes. Here, a novel turn-off fluorescence probe for the highly selective imaging of peroxynitrite (ONOO-) produced by the endogenous stimulation of lysosomes in living cells is presented. The probe, denoted ML-NAP-DPPEA, comprises ML and 2-(diphenylphosphino)ethylamine (DPPE) groups attached to the fluorophore naphthalimide (NAP). ML-NAP-DPPEA shows excellent properties, including high selectivity for ONOO-, low cytotoxicity, and no interference, leading to low detection limits (17.6 nM). In the presence of ONOO-, the secondary amine group (NH) is oxidized to an electron-withdrawing group (HN → O), which quenches the fluorescence of ML-NAP-DPPEA. This intracellular lysosomal imaging technique was tested, and the results pointed to its potential use as a probe for studying the biological function and pathological effects of ONOO- in subcellular structure. Graphical abstract.

Ratiometric iridium(III) complex-based phosphorescent chemodosimeter for Hg(2+) applicable in time-resolved luminescence assay and live cell imaging.

A novel iridium(III) complex-based probe Ir4-1 has been designed and synthesized conveniently by incorporating the chemodosimeter into phosphorescent luminophor, which displayed ratiometric luminescence change from yellowish-green to reddish-yellow only toward Hg(2+) ions in aqueous media via desulfurization and intramolecular cyclization with a broad pH range of 5-10. The phosphorescent chemodosimeter could eliminate effectively the signal interference from the short-lived fluorescent background, and the signal-to-noise ratio of the detection was improved distinctly by using time-resolved photoluminescence technique. Furthermore, the mechanism of phosphoresce change of the chemodosimeter was analyzed in detail by time-dependent density functional theory (TD-DFT) calculations, and the probe with long-wavelength emission could be applied to label cells and monitor intracellular Hg(2+) effectively by luminescence ratio imaging.

Turn-on phosphorescent chemodosimeter for Hg2+ based on a cyclometalated Ir(III) complex and its application in time-resolved luminescence assays and live cell imaging.

A novel "turn-on" phosphorescent chemodosimeter based on a cyclometalated Ir(III) complex has been designed and synthesized, which displays high selectivity and sensitivity toward Hg(2+) in aqueous media with a broad pH range of 4-10. Furthermore, by time-resolved photoluminescence techniques, some interferences from the short-lived background fluorescence can be eliminated effectively and the signal-to-noise ratio of the emission detection can be improved distinctly by using the chemodosimeter. Finally, the chemodosimeter can be used to monitor Hg(2+) effectively in living cells by confocal luminescence imaging.

Lysosome-targeted cyclometalated Ir(III) complexes as photosensitizers/photoredox catalysts for cancer therapy.

A novel lysosome-targeted photosensitizer/photoredox catalyst based on cyclometalated Ir(III) complex IrL has been designed and synthesized, which exhibited excellent phosphorescence properties and the ability to generate single oxygen (1O2) and photocatalytically oxidize 1,4-dihydronicotinamide adenine dinucleotide (NADH) under light irradiation. Most importantly, the aforementioned activities are significantly enhanced due to protonation under acidic conditions, which makes them highly attractive in light-activated tumor therapy, especially for acidic lysosomes and tumor microenvironments. The photocytotoxicity of IrL and the mechanism of cell death have been investigated. Additionally, the tumor-killing ability of IrL under light irradiation was evaluated using a 4T1 tumor-bearing mouse model. This work provides a strategy for the development of lysosome-targeted photosensitizers/photoredox catalysts to overcome hypoxic tumors.

Exploring Hollow Mesoporous Silica Nanoparticles as a Nanocarrier in the Delivery of Foot-And-Mouth Disease Virus-like Particle Vaccines.

Virus-like particle (VLP) vaccine is considered to be the most promising candidate alternative to the traditional inactivated vaccine for foot-and-mouth disease (FMD). To elicit a desired immune response, hollow mesoporous silica nanoparticles (HMSNs) have been synthesized and utilized as a nanocarrier for FMD VLP vaccine delivery. The as-prepared HMSNs displayed a relatively small particle size (∼260 nm), large cavity (∼150 nm), and thin wall (∼55 nm). The inherent structural superiorities make them ideal nanocarriers for the FMD VLP vaccine, which exhibited good biocompatibility, great protein-loading capacity, high antibody-response level, and protective efficiency, even comparable to commercial adjuvant ISA 206. All the results suggested that HMSNs may be a valid nanocarrier in VLP-based vaccines.

Dinuclear Tridentate Ru(II) Complex with Strong Near-Infrared Light-Triggered Anticancer Activity.

The design of the dinuclear Ru(II) complex (Ru2) with strong near-infrared (NIR) absorption properties has been reported for efficient anticancer phototherapy. Under 700 nm LED light excitation, Ru2 exhibited remarkable synergistic type I/II photosensitization ability and photocatalytic activity toward intracellular biomolecules. Ru2 showed impressive 700 nm light-triggered anticancer activity under normoxia and hypoxia compared with the clinically used photosensitizer Chlorin e6. The mechanistic studies showed that Ru2 induced intracellular redox imbalance and perturbed the energy metabolism and biosynthesis in A549 cancer cells. Overall, this work provides a new strategy for developing efficient metal-based complexes for anticancer phototherapy under NIR light.

A 700 nm LED Light Activated Ru(II) Complex Destroys Tumor Cytoskeleton via Photosensitization and Photocatalysis.

Photoactivable chemotherapy (PACT) using metallic complexes provides spatiotemporal selectivity over drug activation for targeted anticancer therapy. However, the poor absorption in near-infrared (NIR) light region of most metallic complexes renders tissue penetration challenging. Herein, an NIR light triggered dinuclear photoactivable Ru(II) complex (Ru2) is presented and the antitumor mechanism is comprehensively investigated. The introduction of a donor-acceptor-donor (D-A-D) linker greatly enhances the intramolecular charge transition, resulting in a high molar extinction coefficient in the NIR region with an extended triplet excited state lifetime. Most importantly, when activated by 700 nm NIR light, Ru2 exhibits unique slow photodissociation kinetics that facilitates synergistic photosensitization and photocatalytic activity to destroy diverse intracellular biomolecules. In vitro and in vivo experiments show that when activated by 700 nm NIR light, Ru2 exhibits nanomolar photocytotoxicity toward 4T1 cancer cells via the induction of calcium overload and endoplasmic reticulum (ER) stress. These findings provide a robust foundation for the development of NIR-activated Ru(II) PACT complexes for phototherapeutic application.

A novel Gd3+ DTPA-bisamide complex with high relaxivity as an MRI contrast agent.

A novel Gd(III) complex-based magnetic resonance imaging (MRI) contrast agent GdL has been designed and synthesized, which exhibited a much higher relaxivity (7.8 mM-1 s-1) than the commercially used Magnevist® (3.5 mM-1 s-1), good water solubility (>100 mg mL-1), excellent thermodynamic stability (log KGdL = 17.21 ± 0.27), high biosafety and biocompatibility. In particular, the relaxivity of GdL increased to 26.7 mM-1 s-1 in a 4.5% bovine serum albumin (BSA) solution at 1.5 T, which was not significant in other commercial MRI contrast agents. The interaction sites and interaction types of GdL and BSA were further demonstrated by molecular docking simulations. Furthermore, the in vivo MRI behaviour was evaluated by using a 4T1 tumour-bearing mouse model. These results suggested that GdL is an excellent T1-weighted MRI contrast agent and has the potential to be applied in clinical diagnosis.

Bio-mineralization of virus-like particles by metal-organic framework nanoparticles enhances the thermostability and immune responses of the vaccines.

Virus-like particle (VLPs) vaccines have been extensively studied due to their good immunogenicity and safety; however, they highly rely on cold-chain storage and transportation. Nanotechnology of bio-mineralization as a useful strategy has been employed to improve the thermal stability and immunogenicity of VLPs. A zeolitic imidazole framework (ZIF-8), a core-shell structured nanocomposite, was applied to encapsulate foot-and-mouth disease virus (FMDV) VLPs. It was found that the ZIF-8 shell enhanced the heat resistance of VLPs and promoted their ability to be taken up by cells and escape from lysosomes. The VLPs-ZIF-8 easily activated antigen-presenting cells (APCs), triggered higher secretion levels of cytokines, and elicited stronger immune responses than VLPs alone even after being treated at 37 °C for 7 days. This platform has good potential in the development of VLP-based vaccine products without transportation.

A newly synthesized visual bis(salamo)-based fluorescent chemosensor for exogenous detection of B4O72- in living cells and zebrafish.

A newly synthesized fluorescent chemosensor H6L was explored for detecting B4O72-, characterized by 1H NMR spectrum, mass spectrum and fluorescence spectra. During the detection process of B4O72-, the fluorescence is significantly enhanced and naked eye recognition can be performed under 365 nm UV light without any interference by other typical anions. The limit of detection is as low as 6.97 × 10-10 M. In addition, in order to broaden the application of salamo-based fluorescence sensors in the field of biology, except for the fluorescence imaging of HeLa cells, the first attempt of exogenous detection in zebrafish was conducted successfully.

Four Simple Biomimetic Mineralization Methods to Improve the Thermostability and Immunogenicity of Virus-like Particles as a Vaccine against Foot-and-Mouth Disease.

The need for a cold chain system during storage and transport substantially increases the cost of vaccines. Virus-like particles (VLPs) are among the best countermeasures against foot and mouth disease virus (FMDV). However, VLPs are composed of pure proteins, and thus, are susceptible to heat. To address this problem, four simple biomimetic mineralization methods with the use of calcium phosphate were developed to improve heat tolerance via biomineralization. The results showed that biomineralization can significantly improve the heat resistance of VLPs. The biomineralized VLPs can be stored at low as 25 °C for eight days, and 37 °C for four days. Animal experiments showed that biomineralization had no effect on the immunogenicity of VLPs or the expression of specific antibodies (Abs) and neutralizing Abs. Even after heat treatment at 37 °C for four days, the biomineralized VLPs remained immunogenic and produced highly specific and neutralizing Abs with a high rate of protection. These results suggest that these biomineralization approaches can promote the thermal stability of VLPs against and significantly reduce dependence on cold storage and delivery systems.

Construction of an Effective Delivery System for DNA Vaccines Using Biodegradable Polylactic Acid Based Microspheres.

Nanotechnology represents a new impetus for biomedical research applications, especially using nanotechnology to formulate microspheres or nanospheres based delivery system for treatment of infectious diseases in animals. In this work, polylactic acid (PLA) microspheres with an average size of 156 nm were prepared by combining emulsion polymerization coupled with emulsion-solvent evaporation. Coating with polyethylenimine (PEI) polymers increased the surface charges of the resulting PLA/PEI microspheres, thus enabled plasmid DNA to adsorb tightly to the microspheres. As expected, the plasmid DNA was successfully transferred into the pig kidney-15 cells with high transfection efficiency. In addition, the protection rate of PLA/PEI microspheres loaded with DNA vaccine against foot-and-mouth disease in guinea pigs reached 87.5%, which was significantly higher than that of the pure DNA vaccine group. These results indicated that PLA/PEI microspheres were expected to be an effective delivery system for DNA vaccines.

Evaluation of the Effect of Inactivated Transmissible Gastroenteritis Virus Vaccine with Nano Silicon on the Phenotype and Function of Porcine Dendritic Cells.

A transmissible gastroenteritis virus (TGEV) is a porcine enteropathogenic coronavirus, causing acute swine enteric disease especially in suckling piglets. Mesoporous silica nanoparticles (MSNs) are safe vaccine adjuvant, which could enhance immune responses. Our previous research confirmed that nano silicon had immune-enhancing effects with inactivated TGEV vaccine. In this study, we further clarified the immune-enhancing mechanism of the inactivated TGEV vaccine with MSNs on porcine dendritic cells (DCs). Our results indicated that the inactivated TGEV vaccine with MSNs strongly enhanced the activation of the DCs. Expressions of TLR3, TLR5, TLR7, TLR9, and TLR10, cytokines IFN-α, IL-1ß, IL-6, IL-12, and TNF-α, cytokine receptor CCR-7 of immature DCs were characterized and showed themselves to be significantly higher in the inactivated TGEV vaccine with the MSN group. In summary, the inactivated TGEV vaccine with MSNs has effects on the phenotype and function of porcine DCs, which helps to better understand the immune-enhancing mechanism.

Enhanced immunogenicity of foot and mouth disease DNA vaccine delivered by PLGA nanoparticles combined with cytokine adjuvants.

Although the immunogenicity of DNA vaccines is nonideal, they are still considered as potential alternative vaccine candidates to conventional vaccines. Various DNA delivery systems, including nanoparticles, have been extensively explored and validated to further enhance the immunogenicity of DNA vaccines. DNA vaccines are considered as alternative vaccine candidates. Various DNA delivery systems, including nanoparticles, have been extensively explored to enhance the immunogenicity of DNA vaccines. In this study, positively charged Poly (D, l-lactide-co-glycolic acid) (PLGA) nanoparticles were generated and characterized as a delivery system for O-serotype foot-and-mouth DNA vaccine. A recombinant plasmid encoding swine interleukin (IL)-18, IL-2, or granulocyte-macrophage colony-stimulating factor (GM-CSF) gene was introduced into the DNA vaccine to further improve its immunogenicity, which was evaluated in a guinea pig model. PLGA-pVAX-VP013/IL-18 elicited significantly (P = 0.0149) higher FMDV-specific antibody levels than naked DNA before the challenge. The level of neutralizing antibodies induced by PLGA-pVAX-VP013/IL-18, PLGA-pVAX-VP013/IL-2, and PLGA-pVAX-VP013/GM-CSF significantly increased compared with that induced by naked DNA (P < 0.0001). The lymphocyte proliferation assay showed that cellular immunity induced by PLGA-pVAX-VP013/IL-18 and PLGA-pVAX-VP013/GM-CSF was dramatically enhanced compared with that induced by the inactivated vaccine. The protection by PLGA-pVAX-VP013/IL-18 was consistent with that by the inactivated vaccine post-challenge and was followed by PLGA-pVAX-VP013/GM-CSF. Therefore, cationic PLGA nanoparticles can deliver DNA vaccines and induce humoral and cellular immune responses. The co-administration of FMD DNA vaccine with IL-18 formulated with PLGA nanoparticles was the optimal strategy to improve the immunogenicity of FMD DNA vaccines.

Fluorescence distinguishing of SO2 derivatives and Cys/GSH from multi-channel signal patterns and visual sensing based on smartphone in living cells and environment.

Sulfur dioxide (SO2), cysteine (Cys) and glutathione (GSH), which perform crucial actions in regulating the balance of human, are closely related reactive sulfur species (RSS). Moreover, SO2 is one of the most concerned air pollutants, which is easily soluble in water and forms its derivatives. Therefore, it is highly desirable to differentiate SO2 derivatives and Cys/GSH in living cells and environment. Herein, a new near-infrared (NIR) mitochondria-targeted fluorescent probe, NIR-CG, which could distinguish SO2 derivatives and Cys/GSH by using multiple sets of signal patterns under single excitation was reported. NIR-CG exhibited different fluorescence signal modes to SO32- and Cys/GSH with low limit of detection (17.1 nM for SO32-, 17.3 nM for Cys and 25.9 nM for GSH). The recognition mechanisms of NIR-CG to SO32- and Cys/GSH were verified by HRMS, 1H NMR and DFT calculation. NIR-CG had good ability of mitochondrial targeted and fluorescence imaging in cells. What's more, NIR-CG showed great recovery rates (101-104%) in the determination of SO32- in actual water samples. It was worth noting that NIR-CG-based paper strip successfully realized the visual quantitative detection of SO32- and Cys/GSH by use of smartphone, which offered a novel method to develop powerful sensing platform.

Synthesis and characterization for a highly selective bis(salamo)-based chemical sensor and imaging in living cell.

A new sensor H5L for continuous identification of Cu2+, Al3+ and lysine was synthesized by Schiff base reactions. The sensor could specifically recognized Cu2+ in the EtOH/H2O (1:1 v/v) solution by UV-vis spectra, and the binding constant with Cu2+ can reach 1011 M-1, meanwhile, it was found by the naked-eye that the color of the solution was changed from colorless to yellow. The copper complex L-Cu2+ formed by the sensor H5L and Cu2+ could further recognize Al3+ and lysine in the fluorescence spectra. The LOD values of the three objects were 2.67 × 10-8, 1.96 × 10-8 and 5.59 × 10-9 M, respectively. In addition, fluorescence intracellular images of Al3+ and lysine were performed and obtained satisfactory results.

An ultrasensitive and visible lighting-up probe for imaging thiophenols in water samples, in serum and visualizing thiophenols-induced oxidative stress process in live cells.

Thiophenols, a class of significant industrial materials, are extremely toxic in environmental as well live cells. However, the process of live cells responding to thiophenols is not well understood. Herein, an innovative "OFF-ON" probe FY for thiophenols selectively in 100% aqueous solution was reported. It featured rapid response (~150 s), prominent sensitivity (detection limit: 5 nM), and large Stokes shift (~104 nm), which assured specific detection of thiophenols in A375 cells, HeLa cells and environment. Especially, it proved that thiophenols in live cells can be eliminated by endogenous reactive oxygen species (ROS), indicating that thiophenols may result in cellular oxidative stress. As well, it was resoundingly put into recognizing of thiophenols quantitatively in actual water samples and in serum.

Photostable Ratiometric Two-Photon Fluorescent Probe for Visualizing Hydrogen Polysulfide in Mitochondria and Its Application.

Hydrogen polysulfide (H2Sn) has currently attracted much research interest because it not only plays an important physiological function in many biological and health-related events, but also is considered as a newfound potent signal transducer. Small-molecule-based ratiometric fluorescent probes have advantages in sensitivity and biodetection, but such approaches that are intentionally developed for H2Sn detection and expected to be mitochondria-accessible are still lacking. In this work, because of the triphenylphosphine group introduced into the molecular scaffold of the naphthalimide derivative, Mito-NRT-HP was successfully applied to visualize intracellular H2Sn in mitochondria with excellent aqueous solubility, super photobleaching resistance, favorable cellular membrane permeability, and good biocompatibility. This one- and two-photon fluorescent probe with high selectivity and sensitivity (limit of detection, LOD = 0.01 µM) evinced a 70-fold enhancement of the fluorescence ratio (I546nm/I478nm) in the presence of H2Sn over other reactive sulfur species (RSS). The experimental results also give Mito-NRT-HP the potential for mapping the H2Sn distribution in mitochondria and evaluating the H2Sn roles in more biological processes, and they demonstrated the practical application possibility of Mito-NRT-HP in the early diagnosis of lipopolysaccharide-induced (LPS-induced) acute organ injury.