Biodegradable Mesoporous Organosilica Nanosheets for Chemotherapy/Mild Thermotherapy of Cancer: Fast Internalization, High Cellular Uptake, and High Drug Loading

Strategies to Regulate the Degradation and Clearance of Mesoporous Silica Nanoparticles: A Review

Mesoporous silica nanoparticles (MSNs) have attracted extensive attention as drug delivery systems because of their unique meso-structural features (high specific surface area, large pore volume, and tunable pore structure), easily modified surface, high drug-loading capacity, and sustained-release profiles. However, the enduring and non-specific enrichment of MSNs in healthy tissues may lead to toxicity due to their slow degradability and hinder their clinical application. The emergence of degradable MSNs provided a solution to this problem. The understanding of strategies to regulate degradation and clearance of these MSNs for promoting clinical trials and expanding their biological applications is essential. Here, a diverse variety of degradable MSNs regarding considerations of physiochemical properties and doping strategies of degradation, the biodistribution of MSNs in vivo, internal clearance mechanism, and adjusting physical parameters of clearance are highlighted. Finally, an overview of these degradable and clearable MSNs strategies for biosafety is provided along with an outlook of the encountered challenges.

Double-layer hollow mesoporous silica nanoparticles for ultrasound-guided photodynamic treatment

Cervical carcinoma persists as a major global public health burden. While conventional therapeutic modalities inevitably cause ablation of adjacent non-tumorous tissues, photodynamic therapy (PDT) offers a targeted cytotoxic strategy through a photosensitizing agent (PS). However, the hydrophobicity and lack of selective accumulation of promising PS compounds such as zinc(II) phthalocyanine (ZnPc) impedes their clinical translation as standalone agents. The present study sought to incorporate ZnPc within double-layer hollow mesoporous silica nanoparticles (DHMSN) as nanocarriers to enhance aqueous dispersibility and tumor specificity. Owing to their compartmentalized design, the hollow mesoporous silica nanoparticles (HMSN) demonstrated enhanced ultrasonic imaging contrast. Combined with the vaporization of the perfluorocarbon perfluoropentane (PFP), the HMSN-encapsulated ZnPc enabled real-time ultrasound monitoring of PDT treatment.In vivo, the innate thermal energy induced vaporization of the DHMSN-carried PFP to significantly amplify ultrasound signals from the tumor site. Results demonstrated biocompatibility, efficient PFP microbubble generation, and robust photocatalytic activity. Collectively, this investigation establishes ultrasound-guided PDT utilizing multi-layer HMSN as a targeted therapeutic strategy for cervical malignancies with mitigated toxicity.

Biodegradable Metal Complex-Gated Organosilica for Dually Enhanced Chemodynamic Therapy through GSH Depletions and NIR Light-Triggered Photothermal Effects

Hollow silica spheres have been widely studied for drug delivery because of their excellent biosecurity and high porosity. However, difficulties with degradation in the tumor microenvironment (TME) and premature leaking during drug delivery limit their clinical applications. To alleviate these problems, herein, hollow organosilica spheres (HOS) were initially prepared using a "selective etching strategy" and loaded with a photothermal drug: new indocyanine green (IR820). Then, the Cu2+-tannic acid complex (Cu-TA) was deposited on the surface of the HOS, and a new nanoplatform named HOS@IR820@Cu-TA (HICT) was finally obtained. The deposition of Cu-TA can gate the pores of HOS completely to prevent the leakage of IR820 and significantly enhance the loading capacity of HOS. Once in the mildly acidic TME, the HOS and outer Cu-TA decompose quickly in response, resulting in the release of Cu2+ and IR820. The released Cu2+ can react with the endogenous glutathione (GSH) to consume it and produce Cu+, leading to the enhanced production of highly toxic ·OH through a Fenton-like reaction due to the overexpressed H2O2 in the TME. Meanwhile, the ·OH generation was remarkably enhanced by the NIR light-responsive photothermal effect of IR820. These collective properties of HICT enable it to be a smart nanomedicine for dually enhanced chemodynamic therapy through GSH depletions and NIR light-triggered photothermal effects.

Biodegradable hollow mesoporous bimetallic nanoreactors to boost chemodynamic therapy

As an endogenous catalytic treatment, chemodynamic therapy (CDT) was attracting considerable attention, but the weak catalytic efficiency of Fenton agents and the non-degradation of nanocarriers severely limited its development. In this work, a biodegradable bimetallic nanoreactor was developed for boosting CDT, in which Fe-doped hollow mesoporous manganese dioxide (HMnO2) was selected as nanocarrier, and the Fe/HMnO2@DOX-GOD@HA nanoprobe was constructed by loading doxorubicin (DOX) and modifying glucose oxidase (GOD) and hyaluronic acid (HA). The glutathione (GSH) responsive degradation of HMnO2 promoted the release of DOX, by which the release rate significantly increased to 96.6%. Moreover, by the GSH depletion, the reduction of Mn2+/Fe2+ achieved strong bimetallic Fenton efficiency, and the hydroxyl radicals (·OH) generation was further enhanced using the self-supplying H2O2 of GOD. Through the active targeting recognition of HA, the bimetallic nanoreactor significantly enriched the tumor accumulation, by which the enhanced antitumor efficacy was realized. Thus, this work developed biodegradable bimetallic nanoreactor by consuming GSH and self-supplying H2O2, and provided a new paradigm for enhancing CDT.

Hollow mesoporous organosilica nanoparticles reduced graphene oxide based nanosystem for multimodal image-guided photothermal/photodynamic/chemo combinational therapy triggered by near-infrared

Developing a nanosystem that can perform multimodal imaging-guided combination therapy is highly desirable but challenging. In this study, we introduced multifunctional nanoparticles (NPs) consisting of graphene oxide-grafted hollow mesoporous organosilica loaded with the drug doxorubicin (DOX) and photosensitizers tetraphenylporphyrin (TPP). These NPs were encapsulated by thermosensitive liposomes that release their contents once the temperature exceeds a certain threshold. Metal oxide NPs grown on the graphene oxide (GO) surface served multiple roles, including enhancing photothermal efficiency, acting as contrast agents to improve magnetic resonance imaging, increasing the sensitivity and specificity of photoacoustic imaging, and catalysing hydrogen peroxide for the generation of reactive oxygen species (ROS). When locally injected, the HMONs-rNGO@Fe3 O4 /MnOx@FA/DOX/TPP NPs effectively enriched in subcutaneous Hela cell tumour of mice. The photothermal/photodynamic/chemo combination therapy triggered by near-infrared (NIR) successfully suppressed the tumour without noticeable side effects. This study presented a unique approach to develop multimodal imaging-guided combination therapy for cancer.

Recent advances in magnetic nanocarriers for tumor treatment

Magnetic nanocarriers are nano-platforms that integrate multiple moieties based on magnetic nanoparticles for diagnostic and therapeutic purposes. In recent years, they have become an advanced platform for tumor treatment due to their wide application in magnetic resonance imaging (MRI), biocatalysis, magneto-thermal therapy (MHT), and photoresponsive therapy. Drugs loaded into magnetic nanocarriers can efficiently be directed to targeted areas by precisely reshaping their structural properties. Magnetic nanocarriers allow us to track the location of the therapeutic agent, continuously control the therapeutic process and eventually assess the efficacy of the treatment. They are typically used in synergistic therapeutic applications to achieve precise and effective tumor treatment. Here we review their latest applications in tumor treatment, including stimuli-responsive drug delivery, MHT, photoresponsive therapy, immunotherapy, gene therapy, and synergistic therapy. We consider reducing toxicity, improving antitumor efficacy, and the targeting accuracy of magnetic nanocarriers. The challenges of their clinical translation and prospects in cancer therapy are also discussed.

Multivalent Aptamer Approach: Designs, Strategies, and Applications

Aptamers are short and single-stranded DNA or RNA molecules with highly programmable structures that give them the ability to interact specifically with a large variety of targets, including proteins, cells, and small molecules. Multivalent aptamers refer to molecular constructs that combine two or more identical or different types of aptamers. Multivalency increases the avidity of aptamers, a particularly advantageous feature that allows for significantly increased binding affinities in comparison with aptamer monomers. Another advantage of multivalency is increased aptamer stabilities that confer improved performances under physiological conditions for various applications in clinical settings. The current study aims to review the most recent developments in multivalent aptamer research. The review will first discuss structures of multivalent aptamers. This is followed by detailed discussions on design strategies of multivalent aptamer approaches. Finally, recent developments of the multivalent aptamer approach in biosensing and biomedical applications are highlighted.

Biodegradable hollow mesoporous organosilica nanotheranostics (HMONs) as a versatile platform for multimodal imaging and phototherapeutic-triggered endolysosomal disruption in ovarian cancer

A major impediment in the development of nanoplatform-based ovarian cancer therapy is endo/lysosome entrapment. To solve this dilemma, a hollow mesoporous organosilica-based nanoplatform (HMON@CuS/Gd₂O₃) with a mild-temperature photothermal therapeutic effect and multimodal imaging abilities was successfully synthesized. HMON@CuS/Gd₂O₃ exhibited an appropriate size distribution, L-glutathione (GSH)-responsive degradable properties, and high singlet oxygen generation characteristics. In this study, the nanoplatform specifically entered SKOV-3 cells and was entrapped in endo/lysosomes. With a mild near infrared (NIR) power density (.5 W/cm²), the HMON@CuS/Gd₂O₃ nanoplatform caused lysosome vacuolation, disrupted the lysosomal membrane integrity, and exerted antitumour effects in ovarian cancer. Additionally, our in vivo experiments indicated that HMON@CuS/Gd₂O₃ has enhanced T1 MR imaging, fluorescence (FL) imaging (wrapping fluorescent agent), and infrared thermal (IRT) imaging capacities. Using FL/MRI/IRT imaging, HMON@CuS/Gd₂O₃ selectively caused mild phototherapy in the cancer region, efficiently inhibiting the growth of ovarian cancer without systemic toxicity in vivo. Taken together, the results showed that these well-synthesized nanoplatforms are likely promising anticancer agents to treat ovarian cancer and show great potential for biomedical applications.

NIR-Controlled Treatment of Multidrug-Resistant Tumor Cells by Mesoporous Silica Capsules Containing Gold Nanorods and Doxorubicin

Multidrug resistance (MDR) is identified as a major impediment to the efficient chemotherapy of cancer, and considerable endeavors have been devoted to reverse MDR containing structuring varieties of multifunctional nanocarriers. Here, a specially light-activated hollow mesoporous silica nanocontainer with an in situ-synthesized Au nanorod (AuNR) core and a surface-modified hairpin structure DNA gatekeeper is reported for treating MDR tumor cells. In this system, the AuNR only fills part of the space in hollow mesoporous silica due to its controllable size, and the remaining space is used to load enough DOX. By controlling the near-infrared (NIR) laser intensity and exposure duration, the configuration of hairpin-structured DNA (T_m = 51.4 °C) can change reversibly and then trigger the controllable intracellular release of DOX, leading to a significantly enhanced chemotherapeutic efficacy and adjustable photothermal treatment for multidrug-resistant cancer cells. The in vitro experiments showed that this system could effectively overcome the MDR of HepG2-adm cells (a MDR cell line of human hepatocarcinoma cells) by the increased concentration of DOX intracellularly and the photothermal conversion of AuNRs, even at a low concentration (e.g., 30 μg mL^-1). Therefore, this NIR-triggered chemo-photothermal synergistic treatment system can be used as a promising efficient strategy in reversing the multidrug resistance for cancer therapy.

Progress in Mesoporous Silica Nanoparticles as Drug Delivery Agents for Cancer Treatment

Cancer treatment and therapy have made significant leaps and bounds in these past decades. However, there are still cases where surgical removal is impossible, metastases are challenging, and chemotherapy and radiotherapy pose severe side effects. Therefore, a need to find more effective and specific treatments still exists. One way is through the utilization of drug delivery agents (DDA) based on nanomaterials. In 2001, mesoporous silica nanoparticles (MSNs) were first used as DDA and have gained considerable attention in this field. The popularity of MSNs is due to their unique properties such as tunable particle and pore size, high surface area and pore volume, easy functionalization and surface modification, high stability and their capability to efficiently entrap cargo molecules. This review describes the latest advancement of MSNs as DDA for cancer treatment. We focus on the fabrication of MSNs, the challenges in DDA development and how MSNs address the problems through the development of smart DDA using MSNs. Besides that, MSNs have also been applied as a multifunctional DDA where they can serve in both the diagnostic and treatment of cancer. Overall, we argue MSNs provide a bright future for both the diagnosis and treatment of cancer.

Recent Development to Explore the Use of Biodegradable Periodic Mesoporous Organosilica (BPMO) Nanomaterials for Cancer Therapy

Porous nanomaterials can be used to load various anti-cancer drugs efficiently and deliver them to a particular location in the body with minimal toxicity. Biodegradable periodic mesoporous organosilica nanoparticles (BPMOs) have recently emerged as promising candidates for disease targeting and drug delivery. They have a large functional surface and well-defined pores with a biodegradable organic group framework. Multiple biodegradation methods have been explored, such as the use of redox, pH, enzymatic activity, and light. Various drug delivery systems using BPMO have been developed. This review describes recent advances in the biomedical application of BPMOs.