Silicon particles as trojan horses for potential cancer therapy

Chiroptical Second-Harmonic Tyndall Scattering from Silicon Nanohelices

Chirality is omnipresent in the living world. As biomimetic nanotechnology and self-assembly advance, they too need chirality. Accordingly, there is a pressing need to develop general methods to characterize chiral building blocks at the nanoscale in liquids such as water─the medium of life. Here, we demonstrate the chiroptical second-harmonic Tyndall scattering effect. The effect was observed in Si nanohelices, an example of a high-refractive-index dielectric nanomaterial. For three wavelengths of illumination, we observe a clear difference in the second-harmonic scattered light that depends on the chirality of the nanohelices and the handedness of circularly polarized light. Importantly, we provide a theoretical analysis that explains the origin of the effect and its direction dependence, resulting from different specific contributions of "electric dipole-magnetic dipole" and "electric dipole-electric quadrupole" coupling tensors. Using numerical simulations, we narrow down the number of such terms to 8 in forward scattering and to a single one in right-angled scattering. For chiral scatterers such as high-refractive-index dielectric nanoparticles, our findings expand the Tyndall scattering regime to nonlinear optics. Moreover, our theory can be broadened and adapted to further classes where such scattering has already been observed or is yet to be observed.

Nanoparticle-Based Drug Delivery Systems Targeting Tumor Microenvironment for Cancer Immunotherapy Resistance: Current Advances and Applications

Cancer immunotherapy has shown impressive anti-tumor activity in patients with advanced and early-stage malignant tumors, thus improving long-term survival. However, current cancer immunotherapy is limited by barriers such as low tumor specificity, poor response rate, and systemic toxicities, which result in the development of primary, adaptive, or acquired resistance. Immunotherapy resistance has complex mechanisms that depend on the interaction between tumor cells and the tumor microenvironment (TME). Therefore, targeting TME has recently received attention as a feasibility strategy for re-sensitizing resistant neoplastic niches to existing cancer immunotherapy. With the development of nanotechnology, nanoplatforms possess outstanding features, including high loading capacity, tunable porosity, and specific targeting to the desired locus. Therefore, nanoplatforms can significantly improve the effectiveness of immunotherapy while reducing its toxic and side effects on non-target cells that receive intense attention in cancer immunotherapy. This review explores the mechanisms of tumor microenvironment reprogramming in immunotherapy resistance, including TAMs, CAFs, vasculature, and hypoxia. We also examined whether the application of nano-drugs combined with current regimens is improving immunotherapy clinical outcomes in solid tumors.

Recent advances in porous nanomaterials-based drug delivery systems for cancer immunotherapy

Cancer immunotherapy is a novel therapeutic regimen because of the specificity and durability of immune modulations to treat cancers. Current cancer immunotherapy is limited by some barriers such as poor response rate, low tumor specificity and systemic toxicities. Porous nanomaterials (PNMs) possess high loading capacity and tunable porosity, receiving intense attention in cancer immunotherapy. Recently, novel PNMs based drug delivery systems have been employed in antitumor immunotherapy to enhance tissue or organ targeting and reduce immune-related adverse events. Herein, we summarize the recent progress of PNMs including inorganic, organic, and organic–inorganic hybrid ones for cancer immunotherapy. The design of PNMs and their performance in cancer immunotherapy are discussed in detail, with a focus on how those designs can address the challenges in current conventional immunotherapy. Lastly, we present future directions of PNMs for cancer immunotherapy including the challenges and research gaps, providing new insights about the design of PNMs for efficient cancer immunotherapy with better performance as powerful weapons against tumors. Finally, we discussed the relevant challenges that urgently need to be addressed in clinical practice, coupled with corresponding solutions to these problems.

In Vivo Sustained Release of Peptide Vaccine Mediated by Dendritic Mesoporous Silica Nanocarriers

Mesoporous silica nanoparticles have drawn increasing attention as promising candidates in vaccine delivery. Previous studies evaluating silica-based vaccine delivery systems concentrated largely on macromolecular antigens, such as inactivated whole viruses. In this study, we synthesized dendritic mesoporous silica nanoparticles (DMSNs), and we evaluated their effectiveness as delivery platforms for peptide-based subunit vaccines. We encapsulated and tested in vivo an earlier reported foot-and-mouth disease virus (FMDV) peptide vaccine (B₂T). The B₂T@DMSNs formulation contained the peptide vaccine and the DMSNs without further need of other compounds neither adjuvants nor emulsions. We measured in vitro a sustained release up to 930 h. B₂T@DMSNs-57 and B₂T@DMSNs-156 released 23.7% (135 µg) and 22.8% (132 µg) of the total B₂T. The formation of a corona of serum proteins around the DMSNs increased the B₂T release up to 61% (348 µg/mg) and 80% (464 µg/mg) for B₂T@DMSNs-57 and B₂T@DMSNs-156. In vitro results point out to a longer sustained release, assisted by the formation of a protein corona around DMSNs, compared to the reference formulation (i.e., B₂T emulsified in Montanide). We further confirmed in vivo immunogenicity of B₂T@DMSNs in a particle size-dependent manner. Since B₂T@DMSNs elicited specific immune responses in mice with high IgG production like the reference B₂T@Montanide™, self-adjuvant properties of the DMSNs could be ascribed. Our results display DMSNs as efficacious nanocarriers for peptide-based vaccine administration.

The potentials of umbilical cord-derived mesenchymal stem cells in the treatment of multiple sclerosis

Stem cell therapy has indicated a promising treatment capacity for tissue regeneration. Multiple sclerosis is an autoimmune-based chronic disease, in which the myelin sheath of the central nervous system is destructed. Scientists have not discovered any cure for multiple sclerosis, and most of the treatments are rather palliative. The pursuit of a versatile treatment option, therefore, seems essential. The immunoregulatory and non-chronic rejection characteristics of mesenchymal stem cells, as well as their homing properties, recommend them as a prospective treatment option for multiple sclerosis. Different sources of mesenchymal stem cells have distinct characteristics and functional properties; in this regard, choosing the most suitable cell therapy approach seems to be challenging. In this review, we will discuss umbilical cord/blood-derived mesenchymal stem cells, their identified exclusive properties compared to another adult mesenchymal stem cells, and the expectations of their potential roles in the treatment of multiple sclerosis.

[18 F]Flurpiridaz: Facile and Improved Precursor Synthesis for this Next-Generation Cardiac Positron Emission Tomography Imaging Agent

[¹⁸ F]Flurpiridaz is a recently developed positron emission tomography tracer that is currently being investigated in phase III clinical trials to measure myocardial blood flow. The relatively long physical half-life of fluorine-18 alongside the high spatial resolution and outstanding myocardium-to-background ratio fuels its potential to be the next gold standard for the early detection of coronary artery disease. Notwithstanding the expected widespread use of [¹⁸ F]flurpiridaz, the reported multistep synthesis of its precursor for radiofluorination involves a hazardous alkylation step using carcinogenic ethylene oxide, and a low overall chemical yield of 7 %. In this work, we have improved the overall yield more than fivefold and concurrently replaced the hazardous step. Specificity of binding of [¹⁸ F]flurpiridaz to mitochondrial complex 1 was demonstrated by in vitro autoradiography on mouse heart tissue sections. These results thus pave the way for assessing myocardial blood flow and coronary flow reserve in mouse models of cardiovascular disease.

Osteogenic potential of Zn2+-passivated carbon dots for bone regeneration in vivo

Carbon dots are a new kind of nanomaterial which has great potential in biomedical applications. Previously, we have synthesized novel Zn2+-passivated carbon dots (Zn-CDs) which showed good osteogenic activity in vitro. In this study, we will further investigate the osteogenic effects of Zn-CDs in vivo which is essential before their clinical use. Herein, Zn2+-passivated carbon dots (Zn-CDs) are prepared and characterized as previously reported. Then, the optimum dose for inducing osteoblasts was evaluated by MTS assay, intracellular reactive oxygen species (ROS) detection, alkaline phosphatase (ALP) activity test and alizarin red staining in vitro. Finally, a 5 mm diameter calvarial bone defect model was created in rats and Zn-CDs were applied for repairing the critical bone defect. It was shown that zinc gluconate (Zn-G) and Zn-CDs promoted the survival of bone marrow stromal cells (BMSCs) when the zinc ion concentration was 10-4 mol L-1 (Zn-G: 45.6 μg mL-1) and 10-5 mol L-1 (Zn-CDs: 300 μg mL-1) or below respectively. With regard to the osteogenic capability, the ALP activity induced by Zn-CDs was significantly higher than that by Zn-G. Besides, the results of alizarin red staining showed that the area of calcified nodules was increased in a dose-dependent manner in the Zn-CD group. Moreover, there were more calcium nodules in the Zn-CD group than in the Zn-G group at the same concentration of Zn2+ (10-5 mol L-1). Taken together, Zn-CDs achieved the highest osteogenic effect at the concentration of 10-5 mol L-1 without affecting cell proliferation in long-term stimulation. Importantly, the volume of new bone formation in the Zn-CD group (6.66 ± 1.25 mm3) was twice higher than that in the control group (3.33 ± 0.94 mm3) in vivo. Further histological evaluation confirmed the markedly new bone formation at 8 weeks in the Zn-CD group. The in vitro and in vivo experiments revealed that Zn-CDs could be a new predictable nanomaterial with good biocompatibility and fluorescence properties for guiding bone regeneration.

Nanomaterials modulate stem cell differentiation: biological interaction and underlying mechanisms

Stem cells are unspecialized cells that have the potential for self-renewal and differentiation into more specialized cell types. The chemical and physical properties of surrounding microenvironment contribute to the growth and differentiation of stem cells and consequently play crucial roles in the regulation of stem cells’ fate. Nanomaterials hold great promise in biological and biomedical fields owing to their unique properties, such as controllable particle size, facile synthesis, large surface-to-volume ratio, tunable surface chemistry, and biocompatibility. Over the recent years, accumulating evidence has shown that nanomaterials can facilitate stem cell proliferation and differentiation, and great effort is undertaken to explore their possible modulating manners and mechanisms on stem cell differentiation. In present review, we summarize recent progress in the regulating potential of various nanomaterials on stem cell differentiation and discuss the possible cell uptake, biological interaction and underlying mechanisms.

Colloidal synthesis of silicon nanoparticles in molten salts

Silicon nanoparticles are unique materials with applications in a variety of fields, from electronics to catalysis and biomedical uses. Despite technological advancements in nanofabrication, the development of a simple and inexpensive route for the synthesis of homogeneous silicon nanoparticles remains highly challenging. Herein, we describe a new, simple and inexpensive colloidal synthetic method for the preparation, under normal pressure and mild temperature conditions, of relatively homogeneous spherical silicon nanoparticles of either ca. 4 or 6 nm diameter. The key features of this method are the selection of a eutectic salt mixture as a solvent, the identification of appropriate silicon alkoxide precursors, and the unconventional use of alkali earth metals as shape-controlling agents.

Aging of Silicon Nanocrystals on Elastomer Substrates: Photoluminescence Effects

Nanocrystalline silicon is widely known as an efficient and tunable optical emitter and is attracting great interest for applications such as light-emitting devices (LEDs), electronic displays, sensors, and solar-photovoltaics. To date, however, luminescent silicon nanocrystals have been used exclusively in traditional rigid devices, leaving a gap in knowledge regarding how they behave on elastomeric substrates. The present study shows how the optical and structural/morphological properties of plasma-synthesized silicon nanocrystals (SiNCs) change when they are deposited on stretchable substrates made from polydimethylsiloxane (PDMS). Our results indicate that SiNCs deposited directly from the gas phase onto PDMS exhibit morphological changes, as well as modified aging characteristics due to enhanced oxidation. These results begin to fill the knowledge gap and point to the potential of using luminescent SiNC layers for flexible and stretchable electronics such as LEDs, displays, and sensors.

Post-nano strategies for drug delivery: Multistage porous silicon microvectors

Nanodelivery systems usually improve the biodistribution of drugs, leading to reduced side effects and enhanced therapeutic efficacy. However, only a small portion of the injected nanoparticle dose accumulates in pathological tissue. Challenges in drug delivery arise due to a multitude of transport obstacles in the body, including the endothelium, the extracellular matrix, and the cell membrane. In general, nanoparticles are designed to overcome only a few biological barriers, making them inadequate for localized drug delivery. Accordingly, a multifunctional and multicomponent systems are required to effectively address a wide variety of transport obstacles. A suitable approach to obtain high levels of multifunctionality is to bring together the nanoscale with the microscale, resulting in post-nano strategies for drug delivery. This review discusses several such post-nano approaches, with an emphasis on the multistage vector (MSV) platform. The MSV consists of three components on different spatial scales, each intended to address biological barriers that exist in a specific compartment in the body. The first stage vector is a microparticle that is designed to navigate in the vascular compartment. The second stage vector consists of nanoparticles that are released from the microparticle into the tissue interstitium, where they address biological barriers in extracellular and intracellular compartments. The final component of the system is a small molecule therapeutic agent. A new generation of microparticle-based strategies with expanded applications has recently been developed, including injectable nanoparticle generators and silicon particles for immunotherapy. Notably, the advantage of incorporating microstructures in drug delivery vehicles is apparent from the observation that superior functionality only appears on the microscale, highlighting the inherent functional limitations of nanostructures.