Peroxynitrite-Scavenging Organosilica Nanomedicines for Light-Controllable NO Release and Precision On-Demand Glaucoma Therapy

Chemical Synthesis and Multihybridization of Small-Sized Hollow Mesoporous Organosilica Nanoparticles Toward Advanced Theranostics

ConspectusAs one of the most widely used nanomaterials, mesoporous silica nanoparticles (MSNs) have received extensive attraction due to their desirable physicochemical performances of high stability, large surface area, and tunable pore sizes. Besides, the U.S. Food and Drug Administration (FDA) has recognized that silica-based nanoparticles are generally safe for biomedical applications. However, the poor biodegradation and inert Si-O-Si framework of inorganic MSNs severely impair their diverse biomedical applications. A promising strategy to improve the physicochemical properties of MSNs is the incorporation of functional organic moieties into their framework to construct mesoporous organosilica nanoparticles (MONs), which exhibit distinct advantages over traditional inorganic MSNs, such as adjustable organosilica framework, excellent biocompatibility, stimuli-responsive biodegradability, and even improved therapeutic effects. Moreover, the emerging hollow-structured MONs (HMONs) with an internal cavity can offer a large drug loading capacity and thus become increasingly attractive and promising theranostic nanoplatforms in biomedicine. In recent years, numerous studies have delved into establishing multifunctional HMONs with sizes ranging in diameters from 50 to 200 nm for desirable biological responses. With the gradual deepening of research, small-sized HMONs with diameters below 50 nm (sub-50 nm HMONs) demonstrate unparalleled advantages in extending blood circulation time, reducing the risk of vascular occlusion, and achieving high tumor accumulation, thus leading to a growing interest in the design, development, and translation of sub-50 nm HMONs. However, the mechanism of the chemical synthesis and structural regulation of sub-50 nm HMONs is still unclear, which is detrimental to further structural hybridization and surface functionalization.In this account, we will focus on the structural design, chemical synthesis, adjustable framework hybridization, multifunctional surface modification, and versatile biomedical applications of small-sized HMONs. First, we will illustrate the chemical approaches for controllable synthesis of HMONs and the underlying mechanism of particle size regulation below 50 nm. Subsequently, the basic principles and design strategies of multihybridization of sub-50 nm HMONs based on framework hybridization, surface modulation, and in situ polymerization will be systematically discussed. Through diverse functionalization strategies, a series of sub-50 nm multihybridized HMONs-based nanotheranostics are established, and their applications in multimodal biomedical imaging and highly efficient synergistic treatment of various diseases (e.g., cancer, glaucoma, bacterial infection, etc.) will be accounted. Finally, we will summarize the current status and potential challenges of HMONs in clinic trials, as well as provide a comprehensive outlook on the future development of sub-50 nm HMONs. These innovative sub-50 nm HMONs hold the potential to introduce novel theranostic modalities for a variety of systemic disorders and to advance smart promising nanomedicine in the near future.

Anti-oxidative mesoporous polydopamine-based hypotensive nano-eyedrop for improved glaucoma management

Conventional hypotensive eye drops remain suboptimal for glaucoma management, primarily due to their limited intraocular bioavailability and the growing concern regarding ocular surface side effects. Therefore, there is an urgent need to develop innovative intraocular pressure (IOP)-lowering formulations that not only possess enhanced corneal penetration ability but also provide ocular surface protection. Herein, anti-oxidative mesoporous polydopamine nanoparticles (MPDA NPs) were explored as a nano-carrier for Brimonidine to address the above issues. Nearly monodisperse MPDA NPs with obvious nanopores were successfully prepared by template-removal method and used for encapsulation of Brimonidine benefiting from their high specific surface area. Interestingly, the PEGylated and drug loaded MPDA-PEG@Brim NPs showed a near neutral surface charge, which is expected to enhance intraocular drug delivery. Consequently, much higher concentration of Brimonidine in the aqueous humor was found after topical administration of MPDA-PEG@Brim nano-dispersion as compared to free Brimonidine solution. Accordingly, superior IOP reduction effect was achieved for the nano-formulation in both hypertensive and normotensive rat eyes. Moreover, MPDA-PEG NPs showed good capability in scavenging diverse free radicals, alleviating intracellular oxidative stress, and mitigating ocular surface oxidative level in a mouse model of preservative-induced dry eye. In addition, the excellent biosafety of this novel Brimonidine nanodrug was confirmed both in vitro and in vivo. Therefore, the present work may shed light on the development of next generation hypotensive formulations for extended ocular surface protection and glaucoma management.

Evaluation of the Ocular Safety of Hollow Mesoporous Organosilica Nanoparticles with Different Tetrasulfur Bond Content

Background

Drug therapy for eye diseases has been limited by multiple protective mechanisms of the eye, which can be improved using well-designed drug delivery systems. Mesoporous silica nanoparticles (MSNs) had been used in many studies as carriers of therapeutic agents for ocular diseases treatment. However, no studies have focused on ocular biosafety. Considering that MSNs containing tetrasulfur bonds have unique advantages and have drawn increasing attention in drug delivery systems, it is necessary to explore the ocular biosafety of tetrasulfur bonds before their widespread application as ophthalmic drug carriers.

Methods

In this study, hollow mesoporous silica nanoparticles (HMSNs) with different tetrasulfur bond contents were prepared and characterized. The ocular biosafety of HMSN-E was evaluated in vitro on the three selected ocular cell lines, including corneal epithelial cells, lens epithelial cells and retinal endothelial cells (HREC), and in vivo by using topical eye drops and intravitreal injections.

Results

In cellular experiments, HMSNs caused obvious S content-dependent cytotoxic effect. HMSNs with the highest tetrasulfur bond content (HMSN-E), showed the highest cytotoxicity among all the HMSNs, and HREC was the most vulnerable cell to HMSN-E. It was shown that HMSN-E could react with intracellular GSH to generate H2S and decrease intracellular GSH concentration. Treatment of HREC with HMSN-E increased intracellular ROS, decreased mitochondrial membrane potential, and induced cell cycle arrest at the G1/S checkpoint, finally caused apoptosis and necrosis of HREC. Topical eye drops of HMSN-E could cause corneal damage. The intravitreal injection of HMSN-E could induce inflammation in the vitreum and ganglion cell layers, resulting in vitreous opacities and retinal abnormalities.

Conclusion

The incorporation of tetrasulfur bonds into HMSN can have toxic effects on ocular tissues. Therefore, when mesoporous silica nanocarriers are designed for ophthalmic pharmaceuticals, the ocular toxicity of the tetrasulfur bonds should be considered.

Biodegradable Mesoporous Organosilica-Based Nanostabilizer Targeting Mast Cells for Long-Term Treatment of Allergic Diseases

Allergic diseases are immune system dysfunctions mediated by mast cell (MC) activation stimulated by specific allergens. However, current small molecular MC stabilizers for allergic disease prevention often require multiple doses over a long period of time and are associated with serious side effects. Herein, we develop a diselenide-bridged mesoporous silica nanostabilizer, proving that it could specifically target sensitized MCs via the recognition of IgE aptamer and IgE. Meantime, the IgE aptamer can also mitigate allergic reactions by preventing re-exposure of allergens from the surface of sensitized MCs. Furthermore, the diselenide-bridged scaffold can be reduced by the intracellular excessive ROS, subsequently achieving redox homeostasis via ROS depletion. Finally, the precise release of small molecular MC stabilizers along with the biodegradation of nanocarrier can stabilize the membranes of MCs. In vivo assays in passive cutaneous anaphylactic (PCA) and allergic rhinitis (AR) mice indicated that our current strategy further endowed it with a high efficacy, long-term therapeutic time window, as well as negligible inflammatory side effects for allergic diseases, offering a promising therapeutic strategy for the clinical generalization of allergic diseases.

Simultaneous Visualization and Depletion of Peroxynitrite by a Simple Aggregation-Induced Emission Nanoprobe for Preventing Breast Cancer Metastasis after Surgery

Inflammation has been confirmed to be closely related to the development of tumors, while peroxynitrite (ONOO-) is one of the most powerful oxidative pro-inflammatory factors. Although ONOO- can kill bacteria through oxidation, it will activate matrix metalloproteinases (MMPs), accelerate the degradation of the extracellular matrix (ECM), and subsequently lead to the activation and release of other tumor promotion factors existing in the ECM, promoting tumor metastasis and invasion. Herein, we report a simple aggregation-induced emission (AIE) nanoprobe (NP), TPE-4NMB, that can simultaneously visualize and deplete ONOO-. The probe can light up the endogenous and exogenous ONOO- in cells and selectively inhibit the proliferation and migration of 4T1 cells by inducing an intracellular redox homeostasis imbalance through ONOO- depletion. After being modified with DSPE-PEG2000, the TPE-4NMB NPs can be used to image ONOO- induced by various models in vivo; especially, it can monitor the dynamic changes of ONOO- level in the residual tumor after surgery, which can provide evidence for clarifying the association between surgery, ONOO-, and cancer metastasis. Excitingly, inhibited tumor volume growth and decreased counts of lung metastases were observed in the TPE-4NMB NPs group, which can be attributed to the downregulated expression of MMP-9 and transforming growth factor-β (TGF-β), increased cell apoptosis, and inhibited epithelial-mesenchymal transition (EMT) mediated by ONOO-. The results will provide new evidence for clarifying the relationship between surgery, ONOO-, and tumor metastasis and serve as a new intervention strategy for preventing tumor metastasis after tumor resection.