A novel DNA vaccine encoding the SRS13 protein administered by electroporation confers protection against chronic toxoplasmosis.

Toxoplasma gondii is an obligate intracellular parasite that can infect a variety of mammals including humans and causes toxoplasmosis. Unfortunately, a protective and safe vaccine against toxoplasmosis hasn't been developed yet. In this study, we developed a DNA vaccine encoding the SRS13 protein and immunized BALB/c mice thrice with pVAX1-SRS13 through the intramuscular route (IM) or intradermally using an electroporation device (ID + EP). The immunogenicity of pVAX1-SRS13 was analyzed by ELISA, Western blot, cytokine ELISA, and flow cytometry. The protective efficacy of the pVAX1-SRS13 was investigated by challenging mice orally with T. gondii PRU strain tissue cysts. The results revealed that pVAX1-SRS13 administered through IM or ID + EP routes induced high level of anti-SRS13 IgG antibody responses (P = 0.0037 and P < 0.0001). The IFN-γ level elicited by the pVAX1-SRS13 (ID + EP) was significantly higher compared to the control group (P = 0.00159). In mice administered with pVAX1-SRS13 (ID + EP), CD8+ cells secreting IFN-γ was significantly higher compared to pVAX1-SRS13 (IM) (P = 0.0035) and the control group (P = 0.0068). Mice vaccinated with the SRS13 DNA vaccine did not induce significant IL-4 level. Moreover, a significant reduction in the number of tissue cysts and the load of T. gondii DNA was detected in brains of mice administered with pVAX1-SRS13 through ID + EP and IM routes compared to controls. In conclusion, the SRS13 DNA vaccine was found to be highly immunogenic and confers strong protection against chronic toxoplasmosis.

NIR light-activated dual-modality cancer therapy mediated by photochemical internalization of porous nanocarriers with tethered lipid bilayers.

To overcome endo/lysosomal restriction as well as to increase the clinical availability of nanomedicine, we report on a NIR stimuli-responsive nanoplatform based on mesoporous silica nanoparticles tethered with lipid bilayers (MSN@tLB) for chemotherapy and photodynamic dual-modality therapy. In this nanosystem, a hydrophilic drug molecule zoledronic acid (ZOL) was first incorporated into the MSN core with modifications of hyperbranched polyethylenimine (PEI). To prevent the leakage of the payload, the LB shell was covalently tethered onto the MSN core via the PEI cushion which can greatly enhance the stability of the LB. Meanwhile, a hydrophobic photosensitizer IR-780 iodide was introduced into the hydrophobic compartment to endow the system with photo-activation properties. The as-prepared MSN-ZOL@tLB-IR780 possesses high dispersion stability stemming from the LB, as well as negligible cytotoxicity. After cellular internalization and endo/lysosomal capture of the nanoparticles, photochemical internalization (PCI) mediated simultaneous cargo release and endo/lysosomal escape were achieved by local ROS production upon 808 nm irradiation, thus leading to highly efficient chemo-photodynamic therapy on cancer cells in vitro. Such a system presents a sophisticated platform that integrates biocompatibility, spatiotemporal control, NIR-responsiveness, and synergistic therapies to promote cancer therapy.

Modulation of the structural properties of mesoporous silica nanoparticles to enhance the T1-weighted MR imaging capability.

In this study, we have investigated the contrast enhancement of Gd(iii) incorporated nanoparticle-based contrast agents (CA) by the modulation of the synthesis and structural parameters of the mesoporous silica nanoparticle (MSN) matrix. In the optimisation process, the structure of the MSN matrix, post-synthesis treatment protocols, as well as the source and incorporation routes of paramagnetic gadolinium centers were considered, with the aim to shorten the T1 weighted relaxation time. After preliminary evaluation of the prepared MSNs as nanoparticulate T1/positive contrast agents based on relaxivity, the structure of the MSN matrix was affirmed as the most decisive property to enhance the r1 relaxivity value, alongside the incorporation route of paramagnetic Gd(iii) centers. Based on these findings, the most promising Gd(iii) incorporated MSN-based CA candidate was further evaluated for its cytocompatibility and intensity enhancement by in vitro phantom MR-imaging of labeled cells. Furthermore, pre-labeled tumors grown on a chick embryo chorioallantoic membrane (CAM) were imaged as an in vivo model on a 3T clinical MRI scanner. Our findings show that the optimized MSN-based CA design enables proper access of water to Gd-centers in the selected MSN matrices, and simultaneously decreases the required amount of Gd(iii) content per mass when evaluated against the other MSNs. Consequently, the required Gd amount on a per-dose basis is significantly decreased with regard to clinically used Gd-based CAs for T1-weighted MR imaging.

Comparative safety evaluation of silica-based particles.

PURPOSE: Silica nanoparticles (SNPs) are increasingly used as drug delivery systems (DDS) and for biomedical imaging. Therapeutic and diagnostic agents can be incorporated into the silica matrix to improve the stability and dissolution of drug substances in biological systems. However, the safety of SNPs as drug carriers remains controversial. To date, no validated and accepted nano-specific tests exist to predict the potentially harmful impact of these materials on the human body. METHODS: We synthesized by a systematic approach 12 different types of SNPs with varying size, surface topology (porous vs non-porous), and surface modifications. We characterized these particles in terms of dry state and hydrodynamic diameter, specific surface area, and net surface charge (ζ-potential). For cellular studies, we exposed non-phagocytic (HepG2) cells, phagocytic (THP-1) cells, and erythrocytes to SNPs. Cellular uptake and stability of fluorescently labeled SNPs were analyzed by confocal microscopy and flow cytometry. RESULTS: SNPs with a porous surface and negative net surface charge had the strongest impact on cell viability. This is in contrast to non-porous SNPs. None of the studied particles induced oxidative stress in either cell lines. Particles with a negative surface charge induced hemolysis in a concentration-dependent manner. CONCLUSIONS: Physico-chemical properties promoting cytotoxicity and hemolysis were investigated. Our study revealed potential hazards of spherical amorphous SNPs.

Functionalization of graphene oxide nanostructures improves photoluminescence and facilitates their use as optical probes in preclinical imaging.

Recently reported photoluminescent nanographene oxides (nGOs), i.e. nanographene oxidised with a sulfuric/nitric acid mixture (SNOx method), have tuneable photoluminescence and are scalable, simple and fast to produce optical probes. This material belongs to the vast class of photoluminescent carbon nanostructures, including carbon dots, nanodiamonds (NDs), graphene quantum dots (GQDs), all of which demonstrate a variety of properties that are attractive for biomedical imaging such as low toxicity and stable photoluminescence. In this study, the nGOs were organically surface-modified with poly(ethylene glycol)-poly(ethylene imine) (PEG-PEI) copolymers tagged with folic acid as the affinity ligand for cancer cells expressing folate receptors. The functionalization enhanced both the cellular uptake and quantum efficiency of the photoluminescence as compared to non-modified nGOs. The nGOs exhibited an excitation dependent photoluminescence that facilitated their detection with a wide range of microscope configurations. The functionalized nGOs were non-toxic, they were retained in the stained cell population over a period of 8 days and they were distributed equally between daughter cells. We have evaluated their applicability in in vitro and in vivo (chicken embryo CAM) models to visualize and track migratory cancer cells. The good biocompatibility and easy detection of the functionalized nGOs suggest that they could address the limitations faced with quantum dots and organic fluorophores in long-term in vivo biomedical imaging.