Functional Nanoparticles with a Reducible Tetrasulfide Motif to Upregulate mRNA Translation and Enhance Transfection in Hard‐to‐Transfect Cells

Non-coding RNAs as regulators of autophagy in chondrocytes: Mechanisms and implications for osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease with multiple causative factors such as aging, mechanical injury, and obesity. Autophagy is a complex dynamic process that is involved in the degradation and modification of intracellular proteins and organelles under different pathophysiological conditions. Autophagy, as a cell survival mechanism under various stress conditions, plays a key role in regulating chondrocyte life cycle metabolism and cellular homeostasis. Non-coding RNAs (ncRNAs) are heterogeneous transcripts that do not possess protein-coding functions, but they can act as effective post-transcriptional and epigenetic regulators of gene and protein expression, thus participating in numerous fundamental biological processes. Increasing evidence suggests that ncRNAs, autophagy, and their crosstalk play crucial roles in OA pathogenesis. Therefore, we summarized the complex role of autophagy in OA chondrocytes and focused on the regulatory role of ncRNAs in OA-associated autophagy to elucidate the complex pathological mechanisms of the ncRNA-autophagy network in the development of OA, thus providing new research targets for the clinical diagnosis and treatment of OA.

Advanced gene therapy system for the treatment of solid tumour: A review

In contrast to conventional therapies that require repeated dosing, gene therapy can treat diseases by correcting defective genes after a single transfection and achieving cascade amplification, and has been widely studied in clinical settings. However, nucleic acid drugs are prone to catabolism and inactivation. A variety of nucleic acid drug vectors have been developed to protect the target gene against nuclease degradation and increase the transformation efficiency and safety of gene therapy. In addition, gene therapy is often combined with chemotherapy, phototherapy, magnetic therapy, ultrasound, and other therapeutic modalities to improve the therapeutic effect. This review systematically introduces ribonucleic acid (RNA) interference technology, antisense oligonucleotides, and clustered regularly interspaced short palindromic repeat/CRISPR-associated nuclease 9 (CRISPR/Cas9) genome editing. It also introduces the commonly used nucleic acid drug vectors, including viral vectors (adenovirus, retrovirus, etc.), organic vectors (lipids, polymers, etc.), and inorganic vectors (MOFs, carbon nanotubes, mesoporous silica, etc.). Then, we describe the combined gene therapy modalities and the pathways of action and report the recent applications in solid tumors of the combined gene therapy. Finally, the challenges of gene therapy in solid tumor treatment are introduced, and the prospect of application in this field is presented.

Tetrasulfide bond boosts the anti-tumor efficacy of dimeric prodrug nanoassemblies

Dimeric prodrug nanoassemblies (DPNAs) stand out as promising strategies for improving the efficiency and safety of chemotherapeutic drugs. The success of trisulfide bonds (-SSS-) in DPNAs makes polysulfide bonds a worthwhile focus. Here, we explore the comprehensive role of tetrasulfide bonds (-SSSS-) in constructing superior DPNAs. Compared to trisulfide and disulfide bonds, tetrasulfide bonds endow DPNAs with superlative self-assembly stability, prolonged blood circulation, and high tumor accumulation. Notably, the ultra-high reduction responsivity of tetrasulfide bonds make DPNAs a highly selective "tumor bomb" that can be ignited by endogenous reducing agents in tumor cells. Furthermore, we present an "add fuel to the flames" strategy to intensify the reductive stress at tumor sites by replenishing exogenous reducing agents, making considerable progress in selective tumor inhibition. This work elucidates the crucial role of tetrasulfide bonds in establishing intelligent DPNAs, alongside the combination methodology, propelling DPNAs to new heights in potent cancer therapy.

Engineered Silica Nanoparticles for Nucleic Acid Delivery

The development of nucleic acid-based drugs holds great promise for therapeutic applications, but their effective delivery into cells is hindered by poor cellular membrane permeability and inherent instability. To overcome these challenges, delivery vehicles are required to protect and deliver nucleic acids efficiently. Silica nanoparticles (SiNPs) have emerged as promising nanovectors and recently bioregulators for gene delivery due to their unique advantages. In this review, a summary of recent advancements in the design of SiNPs for nucleic acid delivery and their applications is provided, mainly according to the specific type of nucleic acids. First, the structural characteristics and working mechanisms of various types of nucleic acids are introduced and classified according to their functions. Subsequently, for each nucleic acid type, the use of SiNPs for enhancing delivery performance and their biomedical applications are summarized. The tailored design of SiNPs for selected type of nucleic acid delivery will be highlighted considering the characteristics of nucleic acids. Lastly, the limitations in current research and personal perspectives on future directions in this field are presented. It is expected this opportune review will provide insights into a burgeoning research area for the development of next-generation SiNP-based nucleic acid delivery systems.

Silicon-containing nanomedicine and biomaterials: materials chemistry, multi-dimensional design, and biomedical application

The invention of silica-based bioactive glass in the late 1960s has sparked significant interest in exploring a wide range of silicon-containing biomaterials from the macroscale to the nanoscale. Over the past few decades, these biomaterials have been extensively explored for their potential in diverse biomedical applications, considering their remarkable bioactivity, excellent biocompatibility, facile surface functionalization, controllable synthesis, etc. However, to expedite the clinical translation and the unexpected utilization of silicon-composed nanomedicine and biomaterials, it is highly desirable to achieve a thorough comprehension of their characteristics and biological effects from an overall perspective. In this review, we provide a comprehensive discussion on the state-of-the-art progress of silicon-composed biomaterials, including their classification, characteristics, fabrication methods, and versatile biomedical applications. Additionally, we highlight the multi-dimensional design of both pure and hybrid silicon-composed nanomedicine and biomaterials and their intrinsic biological effects and interactions with biological systems. Their extensive biomedical applications span from drug delivery and bioimaging to therapeutic interventions and regenerative medicine, showcasing the significance of their rational design and fabrication to meet specific requirements and optimize their theranostic performance. Additionally, we offer insights into the future prospects and potential challenges regarding silicon-composed nanomedicine and biomaterials. By shedding light on these exciting research advances, we aspire to foster further progress in the biomedical field and drive the development of innovative silicon-composed nanomedicine and biomaterials with transformative applications in biomedicine.

Dendritic mesoporous nanoparticles for the detection, adsorption, and degradation of hazardous substances in the environment: State-of-the-art and future prospects

Equipped with hierarchical pores and three-dimensional (3D) center-radial channels, dendritic mesoporous nanoparticles (DMNs) make their pore volumes extremely large, specific surface areas super-high, internal spaces especially accessible, and so on. Other entities (like organic moieties or nanoparticles) can be modified onto the interfaces or skeletons of DMNs, accomplishing their functionalization for desirable applications. This comprehensive review emphasizes on the design and construction of DMNs-based systems which serve as sensors, adsorbents and catalysts for the detection, adsorption, and degradation of hazardous substances, mainly including the construction procedures of brand-new DMNs-based materials and the involved hazardous substances (like industrial chemicals, chemical dyes, heavy metal ions, medicines, pesticides, and harmful gases). The sensitive, adsorptive, or catalytic performances of various DMNs have been compared; correspondingly, the reaction mechanisms have been revealed strictly. It is honestly anticipated that the profound discussion could offer scientists certain enlightenment to design novel DMNs-based systems towards the detection, adsorption, and degradation of hazardous substances, respectively or comprehensively.

mRNA-based vaccines and therapeutics: an in-depth survey of current and upcoming clinical applications

mRNA-based drugs have tremendous potential as clinical treatments, however, a major challenge in realizing this drug class will promise to develop methods for safely delivering the bioactive agents with high efficiency and without activating the immune system. With regard to mRNA vaccines, researchers have modified the mRNA structure to enhance its stability and promote systemic tolerance of antigenic presentation in non-inflammatory contexts. Still, delivery of naked modified mRNAs is inefficient and results in low levels of antigen protein production. As such, lipid nanoparticles have been utilized to improve delivery and protect the mRNA cargo from extracellular degradation. This advance was a major milestone in the development of mRNA vaccines and dispelled skepticism about the potential of this technology to yield clinically approved medicines. Following the resounding success of mRNA vaccines for COVID-19, many other mRNA-based drugs have been proposed for the treatment of a variety of diseases. This review begins with a discussion of mRNA modifications and delivery vehicles, as well as the factors that influence administration routes. Then, we summarize the potential applications of mRNA-based drugs and discuss further key points pertaining to preclinical and clinical development of mRNA drugs targeting a wide range of diseases. Finally, we discuss the latest market trends and future applications of mRNA-based drugs.

A Smart DNA-Based Nanosystem Containing Ribosome-Regulating siRNA for Enhanced mRNA Transfection

Messenger RNA (mRNA) transfection is the prerequisite for the application of mRNA-based therapeutics. In hard-to-transfect cells, such as macrophages, the effective transfection of mRNA remains a long-standing challenge. Herein, a smart DNA-based nanosystem is reported containing ribosome biogenesis-promoting siRNA, realizing efficient mRNA transfection in macrophages. Four monomers are copolymerized to form a nanoframework (NF), including N-isopropylacrylamide (NIPAM) as the skeleton and acrydite-DNA as the initiator to trigger the cascade assembly of DNA hairpins (H1-polyT and H2-siRNA). By virtue of the phase transition characteristic of polymeric NIPAM, below the lower critical solution temperature (LCST, ≈34 °C), the NF swells to expose polyT sequences to hybridize with the polyA tail of mRNA. Above the LCST, the NF deswells to encapsulate mRNA. The disulfide bond in the NF responds to glutathione, triggering the disassembly of the nanosystem; the siRNA and mRNA are released in response to triphosadenine and RNase H. The siRNA down-regulates the expression of heat shock protein 27, which up-regulates the expression of phosphorylated ribosomal protein S6. The nanosystem shows satisfactory mRNA transfection and translation efficiency in a mouse model. It is envisioned that the DNA-based nanosystem will provide a promising carrier to deliver mRNA in hard-to-transfect cells and promote the development of mRNA-based therapeutics.

Advances in mRNA therapeutics for cancer immunotherapy: From modification to delivery

RNA vaccines have demonstrated their ability to solve the issues posed by the COVID-19 pandemic. This success has led to the renaissance of research into mRNA and their nanoformulations as potential therapeutic modalities for various diseases. The potential of mRNA as a template for synthesizing proteins and protein fragments for cancer immunotherapy is now being explored. Despite the promise, the use of mRNA in cancer immunotherapy is limited by challenges, such as low stability against extracellular RNases, poor delivery efficiency to the target organs and cells, short circulatory half-life, variable expression levels and duration. This review highlights recent advances in chemical modification and advanced delivery systems that are helping to address these challenges and unlock the biological and pharmacological potential of mRNA therapeutics in cancer immunotherapy. The review concludes by discussing future perspectives for mRNA-based cancer immunotherapy, which holds great promise as a next-generation therapeutic modality.

Urchin-like ceria nanoparticles for enhanced gene therapy of osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disease in the world. Gene therapy based on delivering microRNAs (miRNAs) into cells has potential for the treatment of OA. However, the effects of miRNAs are limited by the poor cellular uptake and stability. Here, we first identify a type of microRNA-224-5p (miR-224-5p) from clinical samples of patients with OA that can protect articular cartilage from degeneration and further synthesize urchin-like ceria nanoparticles (NPs) that can load miR-224-5p for enhanced gene therapy of OA. Compared with traditional sphere ceria NPs, the thorns of urchin-like ceria NPs can efficiently promote the transfection of miR-224-5p. In addition, urchin-like ceria NPs have excellent performance of scavenging reactive oxygen species (ROS), which can regulate the microenvironment of OA to further improve the gene treatment of OA. The combination of urchin-like ceria NPs and miR-224-5p not only exhibits favorable curative effect for OA but also provides a promising paradigm for translational medicine.

MicroRNA-224-5p nanoparticles balance homeostasis via inhibiting cartilage degeneration and synovial inflammation for synergistic alleviation of osteoarthritis

MicroRNAs play a crucial role in regulating cartilage extracellular matrix (ECM) metabolism and are being explored as potential therapeutic targets for osteoarthritis (OA). The present study indicated that microRNA-224-5p (miR-224-5p) could balance the homeostasis of OA via regulating cartilage degradation and synovium inflammatory simultaneously. Multifunctional polyamidoamine dendrimer with amino acids used as efficient vector to deliver miR-224-5p. The vector could condense miR-224-5p into transfected nanoparticles, which showed higher cellular uptake and transfection efficiency compared to lipofectamine 3000, and also protected miR-224-5p from RNase degradation. After treatment with the nanoparticles, the chondrocytes showed an increase in autophagy rate and ECM anabolic components, as evidenced by the upregulation of autophagy-related proteins and OA-related anabolic mediators. This led to a corresponding inhibition of cell apoptosis and ECM catabolic proteases, ultimately resulting in the alleviation of ECM degradation. In addition, miR-224-5p also inhibited human umbilical vein endothelial cells angiogenesis and fibroblast-like synoviocytes inflammatory hyperplasia. Integrating the above synergistic effects of miR-224-5p in regulating homeostasis, intra-articular injection of nanoparticles performed outstanding therapeutic effect by reducing articular space width narrowing, osteophyte formation, subchondral bone sclerosis and inhibiting synovial hypertrophy and proliferation in the established mouse OA model. The present study provides a new therapy target and an efficient intra-articular delivery method for improving OA therapy. STATEMENT OF SIGNIFICANCE: Osteoarthritis (OA) is the most prevalent joint disease worldwide. Gene therapy, which involves delivering microRNAs, has the potential to treat OA. In this study, we demonstrated that miR-224-5p can simultaneously regulate cartilage degradation and synovium inflammation, thereby restoring homeostasis in OA gene therapy. Moreover, compared to traditional transfection reagents such as lipofectamine 3000, G5-AHP showed better efficacy in both microRNA transfection and protection against degradation due to its specific surface structure. In summary, G5-AHP/miR-224-5p was developed to meet the clinical needs of OA patients and the high requirement of gene transfection efficiency, providing a promising paradigm for the future application and development of gene therapy.

Dual-infinite coordination polymer-engineered nanomedicines for dual-ion interference-mediated oxidative stress-dependent tumor suppression

Recently, nanomedicine design has shifted from simple nanocarriers to nanodrugs with intrinsic antineoplastic activities for therapeutic performance optimization. In this regard, degradable nanomedicines containing functional inorganic ions have blazed a highly efficient and relatively safe ion interference paradigm for cancer theranostics. Herein, given the potential superiorities of infinite coordination polymers (ICPs) in degradation peculiarity and functional integration, a state-of-the-art dual-ICP-engineered nanomedicine is elaborately fabricated via integrating ferrocene (Fc) ICPs and calcium-tannic acid (Ca-TA) ICPs. Thereinto, Fc ICPs, and Ca-TA ICPs respectively serve as suppliers of ferrous iron ions (Fe²⁺) and calcium ions (Ca²⁺). After the acid-responsive degradation of ICPs, released TA from Ca-TA ICPs facilitated the conversion of released ferric iron (Fe³⁺) from Fc ICPs into highly active Fe²⁺. Owing to the dual-path oxidative stress and neighboring effect mediated by Fe²⁺ and Ca²⁺, such a dual-ICP-engineered nanomedicine effectively induces dual-ion interference against triple-negative breast cancer (TNBC). Therefore, this work provides a novel antineoplastic attempt to establish ICP-engineered nanomedicines and implement ion interference-mediated synergistic therapy.

Hyaluronic acid-functionalized redox-responsive organosilica nanoparticles for targeted resveratrol delivery to attenuate acrylamide-induced toxicity

The purpose of this study is to construct a redox-responsive and targeted nanoparticle to effectively deliver resveratrol (Res) for alleviating acrylamide (ACR) toxicity. Here, Res-loaded tetrasulfide-containing organosilica nanoparticles (DSMSNs) functionalized with hyaluronic acid on the surface (DSMSNs@Res@HA) were prepared. The DSMSNs@Res@HA nanoparticles were spherical with an encapsulation efficiency of 46.68 ± 1.64 % and a hydrated particle size of about 237.73 nm. As expected, DSMSNs@Res@HA were capable of significantly protecting PC12 cells against ACR-induced damage in oxidative stress, mitochondrial membrane potential decrease, and cell apoptosis compared with free Res and DSMSNs@Res at the equivalent dose. Moreover, DSMSNs@Res@HA could be biodegraded and released Res in response to GSH stimulus. In vivo experiments suggested that DSMSNs@Res@HA significantly reduced histological damage in the brain, liver, and kidney of rats compared with free Res and DSMSNs@Res. After oral administration of DSMSNs@Res@HA, the intestinal flora of ACR-treated rats could be effectively regulated by improving the species uniformity and abundance as well as recovering the species diversity. According to these findings, DSMSNs@Res@HA is worth further investigation as a potential therapeutic nanomedicine to alleviate ACR toxicity and restore gut microbiota diversity.

Mesoporous Organosilica Nanoparticles with Tetrasulphide Bond to Enhance Plasmid DNA Delivery

Cellular delivery of plasmid DNA (pDNA) specifically into dendritic cells (DCs) has provoked wide attention in various applications. However, delivery tools that achieve effective pDNA transfection in DCs are rare. Herein, we report that tetrasulphide bridged mesoporous organosilica nanoparticles (MONs) have enhanced pDNA transfection performance in DC cell lines compared to conventional mesoporous silica nanoparticles (MSNs). The mechanism of enhanced pDNA delivery efficacy is attributed to the glutathione (GSH) depletion capability of MONs. Reduction of initially high GSH levels in DCs further increases the mammalian target of rapamycin complex 1 (mTORc1) pathway activation, enhancing translation and protein expression. The mechanism was further validated by showing that the increased transfection efficiency was apparent in high GSH cell lines but not in low GSH ones. Our findings may provide a new design principle of nano delivery systems where the pDNA delivery to DCs is important.

Mesoporous Organosilica Nanoparticles with Tetrasulphide Bond to Enhance Plasmid DNA Delivery

Cellular delivery of plasmid DNA (pDNA) specifically into dendritic cells (DCs) has provoked wide attention in various applications. However, delivery tools that achieve effective pDNA transfection in DCs are rare. Herein, we report that tetrasulphide bridged mesoporous organosilica nanoparticles (MONs) have enhanced pDNA transfection performance in DC cell lines compared to conventional mesoporous silica nanoparticles (MSNs). The mechanism of enhanced pDNA delivery efficacy is attributed to the glutathione (GSH) depletion capability of MONs. Reduction of initially high GSH levels in DCs further increases the mammalian target of rapamycin complex 1 (mTORc1) pathway activation, enhancing translation and protein expression. The mechanism was further validated by showing that the increased transfection efficiency was apparent in high GSH cell lines but not in low GSH ones. Our findings may provide a new design principle of nano delivery systems where the pDNA delivery to DCs is important.

Amorphous Ultra-Small Fe-Based Nanocluster Engineered and ICG Loaded Organo-Mesoporous Silica for GSH Depletion and Photothermal-Chemodynamic Synergistic Therapy

Intracellular oxidative amplification can effectively destroy tumor cells. Additionally, Fe-mediated Fenton reaction often converts cytoplasm H₂ O₂ to generate extensive hypertoxic hydroxyl radical (^• OH), leading to irreversible mitochondrion damage for tumor celleradication, which is widely famous as tumor chemodynamic therapy (CDT). Unfortunately, intracellular overexpressed glutathione (GSH) always efficiently scavenges ^• OH, resulting in the significantly reduced CDT effect. To overcome this shortcoming and improve the oxidative stress in cytoplasm, Fe₃ O₄ ultrasmall nanoparticle encapsulated and ICG loaded organo-mesoporous silica nanovehicles (omSN@Fe-ICG) are constructed to perform both photothermal and GSH depletion to enhance the Fenton-like CDT, by realizing intracellular oxidative stress amplification. After this nanoagents are internalized, the tetrasulfide bonds in the dendritic mesoporous framework can be decomposed with GSH to amplify the toxic ROS neration by selectively converting H₂ O₂ to hydroxyl radicals through the released Fe-based nanogranules. Furthermore, the NIR laser-induced hyperthermia can further improve the Fenton reaction rate that simultaneously destroyed the mitochondria. As a result, the GSH depletion and photothermal assisted CDT can remarkably improve the tumor eradication efficacy.

Nanostructured Organosilica Nitric Oxide Donors Intrinsically Regulate Macrophage Polarization with Antitumor Effect

Nitric oxide (NO) has many important biological functions; however, it has been a long-standing challenge to utilize the exogenous NO donor itself in the activation of macrophages for cancer immunotherapy. Herein, we report the synthesis of a nanoparticle-based NO delivery platform with a rational design for effective NO delivery and macrophage activation. S-Nitrosothiol (SNO) modified organosilica nanoparticles with a tetrasulfide-containing composition produced a higher level of intracellular NO than their bare silica counterparts in macrophages. Enhanced intracellular delivery of NO resulted in mitochondrial dysfunction and disruption of the tricarboxylic acid cycle, leading to macrophage activation and delayed tumor growth. This study provides insights on intracellularly delivered NO for regulating the polarization of macrophages and cancer immunotherapy.

Spatio-Temporal Controlled Gene-Chemo Drug Delivery in a DNA Nanocomplex to Overcome Multidrug Resistance of Cancer Cells

Multidrug resistance (MDR) in cancer cells is a substantial limitation to the success of chemotherapy. The spatio-temporal controlled gene-chemo therapeutics strategy is expected to surmount the limitation of MDR. We herein develop a DNA nanocomplex to achieve intrinsic stimuli-responsive spatio-temporal controlled gene-chemo drug delivery, overcoming MDR of cancer cells. The drug delivery system consisted of a restriction endonuclease (HhaI)-degradable DNA hydrogel layer, an acid-responsive HhaI nanocapsule (HhaI-GDA), and a glutathione (GSH)-sensitive dendritic mesoporous organosilica nanoparticle (DMON). The DNA hydrogel layer consisted of a DNA network formed through interfacial assembly from ultralong single-stranded DNA (ssDNA), which contained multiple tandem repeated antisense oligonucleotides (ASOs). DMON had dendritic mesopores for enhanced loading of anti-tumor drug doxorubicin (DOX). Upon cellular uptake of the DNA nanocomplex, the GDA shell was degraded at a lysosomal microenvironment, and the activity of HhaI was activated, leading to accurate cleavage ultralong ssDNA to release ASO as gene drugs, which down-regulated the expression of MDR-related P glycoprotein. Spatio-temporal sequentially, DMONs containing disulfide bonds responded to intracellular GSH to release DOX for enhanced chemotherapy.

Tumor Microenvironment-Responsive Yolk-Shell NaCl@Virus-Inspired Tetrasulfide-Organosilica for Ion-Interference Therapy via Osmolarity Surge and Oxidative Stress Amplification

Ion-interference therapy, which utilizes ions to disturb intracellular biological processes, provides inspiration for tumor therapy. Artificially reversing osmotic pressure by transporting large amounts of physiological ions to tumor cells is a straightforward yet low-toxic strategy for ion-interference therapy. However, it is hard to achieve due to the serious limitations of single-ion delivery. Herein, we skillfully deliver NaCl nanocrystals to tumor sites and sequentially realize the explosive release of Na⁺/Cl^- inside tumor cells by utilizing a virus-mimicking and glutathione (GSH)-responsive hollow mesoporous tetrasulfide-bridged organosilica (ssss-VHMS). Once the ssss-VHMS-wrapped NaCl nanocrystals (NaCl@ssss-VHMS) accumulate in the tumors, they would rapidly invade tumor cells via spike surface-assisted endocytosis, thus bypassing Na⁺/K⁺-ATPase transmembrane ion transporters. Afterward, the intracellular overproduced GSH of tumor cells would trigger the rapid degradation of ssss-VHMS via thiol-tetrasulfide exchange, which could not only remarkably deplete the GSH but also explosively release the Na⁺/Cl^-, leading to the osmolarity surge accompanied by reactive oxygen species (ROS) generation. The cell swelling, ROS storm, and GSH exhaustion of NaCl@ssss-VHMS effectively eradicated tumor cells by caspase-1-dependent pyroptosis, caspase-3-dependent apoptosis, and GPX4-dependent ferroptosis, respectively, thus synergistically inhibiting tumor growth. We believe that NaCl@ssss-VHMS would be a potential cancer therapeutic agent, and this discovery could provide a perspective for exploring synergistic ion-interference therapy.

mRNA-based therapeutics: powerful and versatile tools to combat diseases

The therapeutic use of messenger RNA (mRNA) has fueled great hope to combat a wide range of incurable diseases. Recent rapid advances in biotechnology and molecular medicine have enabled the production of almost any functional protein/peptide in the human body by introducing mRNA as a vaccine or therapeutic agent. This represents a rising precision medicine field with great promise for preventing and treating many intractable or genetic diseases. In addition, in vitro transcribed mRNA has achieved programmed production, which is more effective, faster in design and production, as well as more flexible and cost-effective than conventional approaches that may offer. Based on these extraordinary advantages, mRNA vaccines have the characteristics of the swiftest response to large-scale outbreaks of infectious diseases, such as the currently devastating pandemic COVID-19. It has always been the scientists’ desire to improve the stability, immunogenicity, translation efficiency, and delivery system to achieve efficient and safe delivery of mRNA. Excitingly, these scientific dreams have gradually been realized with the rapid, amazing achievements of molecular biology, RNA technology, vaccinology, and nanotechnology. In this review, we comprehensively describe mRNA-based therapeutics, including their principles, manufacture, application, effects, and shortcomings. We also highlight the importance of mRNA optimization and delivery systems in successful mRNA therapeutics and discuss the key challenges and opportunities in developing these tools into powerful and versatile tools to combat many genetic, infectious, cancer, and other refractory diseases.

Emerging mRNA technologies: delivery strategies and biomedical applications

The great success achieved by the two highly-effective messenger RNA (mRNA) vaccines during the COVID-19 pandemic highlights the great potential of mRNA technology. Through the evolution of mRNA technology, chemistry has played an important role from mRNA modification to the synthesis of mRNA delivery platforms, which allows various applications of mRNA to be achieved both in vitro and in vivo. In this tutorial review, we provide a summary and discussion on the significant progress of emerging mRNA technologies, as well as the underlying chemical designs and principles. Various nanoparticle (NP)-based delivery strategies including protein-mRNA complex, lipid-based carriers, polymer-based carriers, and hybrid carriers for the efficient delivery of mRNA molecules are presented. Furthermore, typical mRNA delivery platforms for various biomedical applications (e.g., functional protein expression, vaccines, cancer immunotherapy, and genome editing) are highlighted. Finally, our insights into the challenges and future development towards clinical translation of these mRNA technologies are provided.

Silica Nanoparticles with Virus-Mimetic Spikes Enable Efficient siRNA Delivery In Vitro and In Vivo

Oligonucleotide-based therapy has experienced remarkable development in the past 2 decades, but its broad applications are severely hampered by delivery vectors. Widely used viral vectors and lipid nanovectors are suffering from immune clearance after repeating usage or requiring refrigerated transportation and storage, respectively. In this work, amino-modified virus-mimetic spike silica nanoparticles (NH 2 -SSNs) were fabricated using a 1-pot surfactant-free approach with controlled spike lengths, which were demonstrated with excellent delivery performance and biosafety in nearly all cell types and mice. It indicated that NH 2 -SSNs entered cells by spike-dependent cell membrane docking and dynamin-dependent endocytosis. The positively charged spikes with proper length on the surface can facilitate the efficient encapsulation of RNAs, protect the loaded RNAs from degradation, and trigger an early endosome escape during intracellular trafficking, similarly to the cellular internalization mechanism of virions. Regarding the fantastic properties of NH 2 -SSNs in nucleic acid delivery, it revealed that nanoparticles with solid spikes on the surface would be excellent vehicles for gene therapy, presenting self-evident advantages in storage, transportation, modification, and quality control in large-scale production compared to lipid nanovectors.

Dendritic Mesoporous Nanoparticles: Structure, Synthesis and Properties

Recently, a new family of "dendritic" mesoporous silica nanoparticles has attracted great interest with widespread applications. Despite a large number of publications (>800), the terminology of "dendritic" is ambiguous. Understanding what possible "dendritic structures" are, their formation mechanisms and the underlying structure-property relationship is fundamentally important. With the advance of characterization techniques such as electron tomography, two types of tree branch-like and flower-like structures can be distinguished, both described as "dendritic" in literature. In this review, we start with the definition of "dendritic", then provide critical analysis of reported dendritic silica nanoparticles according to their structural classification. We also update the understandings of the formation mechanisms of two types of "dendritic" nanoparticles, with a focus on how to control different structural parameters. Various applications of dendritic mesoporous nanoparticles are also reviewed with a focus in biomedical field, providing new insights into the structure-property relationship in this family of nanomaterials.

Confined growth of ZIF-8 in dendritic mesoporous organosilica nanoparticles as bioregulators for enhanced mRNA delivery in vivo

Zeolitic imidazolate framework-8 (ZIF-8) and its composites have diverse applications. However, ZIF-8-based nanocomposites are mainly used as carriers in biomolecular delivery, with the functions of metal ions and ligands rarely used to modulate the biofunctions. In this work, dendritic mesoporous organosilica nanoparticles (DMONs) with tetrasulfide bond were used to confine ZIF-8 growth partially inside mesopores as a novel nanocomposite for mRNA delivery. Each component in the resultant DMONs-ZIF-8 contributed to mRNA delivery applications, including high loading benefitting from positively charged ZIF-8 and large mesopores of DMONs, endosomal escape promoted by the imidazole ring of ZIF-8, and long-term glutathione depletion mediated by both zinc ions and tetrasulfide bond. Combined together, DMONs-ZIF-8 demonstrated enhanced mRNA translation and better transfection efficiency than commercial products and toxic polymer-modified DMONs in vitro and in vivo.

mRNA delivery via non-viral carriers for biomedical applications

As an emerging new class of nucleic acid drugs, messenger RNA (mRNA) has huge potential in immunotherapy, regenerative medicine, vaccine, and gene editing. Comparing with siRNA and pDNA, mRNA is more vulnerable to nucleases in vivo. However, the lack of effective and safe delivery methods impedes the broad application of mRNA-based therapeutics. Up to now, the delivery of mRNA remains largely unexplored, and therefore, is a hot topic in the field of gene therapy. In this review, we will summarize the ongoing challenges in mRNA-based therapeutics and unmet requirements for delivery vehicles in terms of the unique structure of mRNA. We then highlight the advancement in mRNA delivery in both fundamental research and clinical applications. Finally, a prospective will be proposed upon reviewing the current progress in mRNA delivery.

Disulfide bond based cascade reduction-responsive Pt(IV) nanoassemblies for improved anti-tumor efficiency and biosafety

The platinum-based drugs prevail in the therapy of malignant tumors treatment. However, their clinical outcomes have been heavily restricted by severe systemic toxicities. To ensure biosafety and efficiency, herein, we constructed a disulfide bond inserted Pt(IV) self-assembled nanoplatform that is selectively activated by rich glutathione (GSH) in tumor site. Disulfide bond was introduced into the conjugates of oxaliplatin (IV) and oleic acid (OA) which conferred cascade reduction-responsiveness to nanoassemblies. Disulfide bond cleavage and reduction of Pt(IV) center occur sequentially as a cascade process. In comparison to oxaliplatin solution, Pt(IV) nanoparticles (NPs) achieved prolonged blood circulation and higher maximum tolerated doses. Furthermore, Oxa(IV)-SS-OA prodrug NPs exhibited potent anti-tumor efficiency against 4T1 cells and low toxicities in other normal tissues, which offers a promising nano-platform for potential clinical application.

Designer Anticancer Nanoprodrugs with Self-Toxification Activity Realized by Acid-triggered Biodegradation and In Situ Fragment Complexation

Prodrugs that allow in situ chemical conversion of less toxic precursors into active drugs in response to certain stimuli are promising anticancer candidates. Herein, we present a novel design of nanoprodrugs with a "degradation-mediated self-toxification" strategy, which realizes intracellular synthesis of anticancer agents using the nanoparticles' own degradation fragments as the precursors. To fulfill this concept, a metal complexing dicyclohexylphosphine (DCP) organosilane is carefully screened out from various ligands to conjugate onto Pd(OH)₂ nanodots confined hollow silica nanospheres (PD-HSN). This constructed nanoprodrug shows acid-triggered degradation in lysosomes and neutralizes protons to induce lysosomes rupturing, generating predesigned less toxic fragments (Pd²⁺ and DCP-silicates) that complex into DCP/Pd complex in situ for inducing DNA damage, leading to enhanced anticancer activity against various cancer cell lines as well as in a xenograft tumour model.

A Systematic Study of Unsaturation in Lipid Nanoparticles Leads to Improved mRNA Transfection In Vivo

Lipid nanoparticles (LNPs) represent the leading concept for mRNA delivery. Unsaturated lipids play important roles in nature with potential for mRNA therapeutics, but are difficult to access through chemical synthesis. To systematically study the role of unsaturation, modular reactions were utilized to access a library of 91 amino lipids, enabled by the synthesis of unsaturated thiols. An ionizable lipid series (4A3) emerged from in vitro and in vivo screening, where the 4A3 core with a citronellol-based (Cit) periphery emerged as best. We studied the interaction between LNPs and a model endosomal membrane where 4A3-Cit demonstrated superior lipid fusion over saturated lipids, suggesting its unsaturated tail promotes endosomal escape. Furthermore, 4A3-Cit significantly improved mRNA delivery efficacy in vivo through Selective ORgan Targeting (SORT), resulting in 18-fold increased protein expression over parent LNPs. These findings provide insight into how lipid unsaturation promotes mRNA delivery and demonstrate how lipid mixing can enhance efficacy.

Benzene-Bridged Organosilica Modified Mesoporous Silica Nanoparticles via an Acid-Catalysis Approach

Surface functionalization of mesoporous silica nanoparticles is important for their applications but fairly challenging using benzene-bridged organosilane as the precursor through the postsynthesis approach. Herein, we report an acid-catalysis approach for the postmodification of benzene-bridged organosilica onto the surface of large-pore mesoporous silica nanoparticles. By using HCl (∼1 M) as the acid catalyst in a tetrahydrofuran solvent, the self-assembly of the bridged organosilica precursor is avoided, while surface modification of mesoporous silica nanoparticles is promoted with controllable organic contents and retained large pore sizes. This strategy can also be applied to the postmodification of organosilica with end benzene groups. The strategy developed in this study is expected to be applied for the postmodification of other organosilica precursors with various functions.

Surfactant-free synthesis of monodispersed organosilica particles with pure sulfide-bridged silsesquioxane framework chemistry via extension of Stöber method

Sulfide bond incorporated organosilica particles have been broadly applied to versatile biomedical applications, wherein the uniformity of particles and the sulfur content significantly dictate the ultimate performance. Unfortunately, due to the difficulty in controlling the chemical behavior of organosilica precursors in a sol-gel process, challenges still exist in developing a facile and green synthetic approach to fabricate organosilica particles with good dispersity and high sulfur content. In the present work, by extending the classic Stöber method, a surfactant-free synthesis of monodispersed organosilica particles with pure sulfide-bridged silsesquioxane framework chemistry is reported for the first time. By simply tailoring the ethanol-to-water ratio and amount of catalyst, the size of disulfide-bridged organosilica particles can be tuned from ~0.50 to ~1.20 µm. Moreover, this approach can be employed to prepare tetra-sulfide bridged silica nanoparticles with an extremely high sulfur content of 30.7 wt% and negligible cytotoxicity. Notably, taking advantage of this extended Stöber method, both hydrophilic (methylene blue) and hydrophobic (curcumin) molecules can be in-situ encapsulated into tetra-sulfide bridged silica nanoparticles, whose glutathione-triggered biodegradability is also demonstrated. Collectively, the innovative synthetic approach and organosilica particles developed in this work are expected to open up new opportunities in hybrid materials fabrication and bio-applications.

Nanomaterial Delivery Systems for mRNA Vaccines

The recent success of mRNA vaccines in SARS-CoV-2 clinical trials is in part due to the development of lipid nanoparticle delivery systems that not only efficiently express the mRNA-encoded immunogen after intramuscular injection, but also play roles as adjuvants and in vaccine reactogenicity. We present an overview of mRNA delivery systems and then focus on the lipid nanoparticles used in the current SARS-CoV-2 vaccine clinical trials. The review concludes with an analysis of the determinants of the performance of lipid nanoparticles in mRNA vaccines.

Emerging Concepts of Nanobiotechnology in mRNA Delivery

Introducing mRNA into cells has attracted intense interest for diverse applications; however, success requires delivery solutions. Engineered nanomaterials have been applied as mRNA nanocarriers; their functions are designed mainly as delivery vehicles, but rarely in regulation of the protein translation. Recently, progress in nanobiotechnology has shifted the design principle of mRNA nanocarriers from simple delivery tools to translation modulators. Here, we review the emerging concepts of nanomaterials regulating mRNA translation and recent progress in mRNA delivery. Designer nanomaterials providing integrated functions for specific mRNA applications are also reviewed to provide insights for the design of next-generation nanomaterials to revolutionize mRNA technology.

Silica-Based Nanoparticles for Biomedical Applications: From Nanocarriers to Biomodulators

Silica-based nanoparticles (SNPs) are a classic type of material employed in biomedical applications because of their excellent biocompatibility and tailorable physiochemical properties. Typically, SNPs are designed as nanocarriers for therapeutics delivery, which can address a number of intrinsic drawbacks of therapeutics, including limited bioavailability, short circulation lifetime, and unfavorable biodistribution. To improve the delivery efficiency and spatiotemporal precision, tremendous efforts have been devoted to engineering the physiochemical properties of SNPs, including particle size, morphology, and mesostructure, as well as conjugating targeting ligands and/or "gatekeepers" to endow improved cell selectivity and on demand release profiles. Despite significant progress, the biologically inert nature of the bare silica framework has largely restricted the functionalities of SNPs, rendering conventional SNPs mainly as nanocarriers for targeted delivery and controlled release. To meet the requirements of next generation nanomedicines with improved efficacy and precision, new insights on the relationship between the physiochemical properties of SNPs and their biological behavior are highly valuable. Meanwhile, a conceptual shift from a simple spatiotemporal control mechanism to a more sophisticated biochemistry and signaling pathway modulation would be of great importance.In this Account, an overview of our recent contribution to the field is presented, wherein SNPs with rationally designed nanostructures and nanochemistry are applied as nanocarriers (defined as "nanomaterials being used as a transport module for another substance" according to Wikipedia) and/or biomodulators (defined as "any material that modifies a biological response" according to Wiktionary). This Account encompasses two main sections. In the first section, we focus on the conventional nanocarriers concept with new insights on the design principles of the nanostructures. We present examples to demonstrate the engineering of pore geometry, surface topology, and asymmetry of nanoparticles to achieve enhanced drug, gene, and protein delivery efficiency. The contribution of surface roughness of SNPs on improving the cellular uptake efficiency, adhesion property, and DNA transfection capacity is particularly highlighted. In the second section, we discuss novel SNPs designed as biomodulators to regulate intracellular microenvironment and cell signaling, such as the oxidative stress and glutathione levels for improving the anticancer efficacy of therapeutics and mRNA transfection in specific cell lines. The interplay between the nanoparticles, biological system, and drugs is discussed. We further discuss how to engineer the composition of SNPs to modulate metal hemostasis to realize inherent anticancer activity. Two typical examples, including modulating copper signaling for tumor vasculature targeted therapy and controlling iron signaling for macrophage polarization based immunotherapy, are presented to highlight the unique advantages of SNPs as nanosized therapeutics in comparison to molecular drugs. Moreover, utilizing these two examples, we showcase the possibility of designing SNPs with intrinsic pharmaceutical activity to indirectly control tumor growth without inducing significant cytotoxicity, thus alleviating the biosafety concerns of nanomedicines. At the end of this Account, we discuss our personal perspectives on the promises, opportunities, and issues in engineered SNPs as nanocarriers as well as their transition toward biomodulators. With a major focus on the latter scenario, the current status and possible future directions are outlined.