Recent Advances in Functional Nanomaterials for Catalytic Generation of Nitric Oxide: A Mini Review

Selenium nanoparticles as catalysts for nitric oxide generation

The critical role of nitric oxide (NO), a potent signalling molecule, in various physiological processes has driven the development of NO delivery strategies for numerous therapeutic applications. However, NO's short half-life poses a significant challenge for its effective delivery. Glutathione peroxidase, a selenium-containing antioxidant enzyme, can catalyse the decomposition of S-nitrosothiols (endogenous NO prodrugs) to produce NO in situ. Inspired by this, we explored selenium nanoparticles (SeNPs) for their enzyme-mimicking NO-generating activity. Stabilised with polyvinyl alcohol (PVA) or chitosan (CTS), SeNPs demonstrated tuneable NO generation when exposed to varying concentrations of NO prodrug, nanoparticles, and glutathione (GSH). In the presence of GSH, a naturally occurring antioxidant in the human body, 0.1 µg mL-1 of SeNPs could catalytically generate 7.5 µM of NO under physiological conditions within 30 min. We investigated the effects of nanoparticle crystallinity and NO prodrug type on NO generation, as well as the stability and sustained NO generation of the catalytic nanoparticles. PVA-stabilised SeNPs were non-toxic to NIH 3T3 cells and effectively dispersed Pseudomonas aeruginosa biofilms upon NO generation. This study broadens the repertoire of nanomaterials for NO generation and highlights SeNPs as a non-toxic alternative for therapeutic NO delivery.

An oxidized chondroitin sulfate-crosslinked and CuCDs-loaded decellularized bovine pericardium with improved anti-coagulation, pro-endothelialization and anti-calcification properties for BHVs

With the growth of the elderly people and the development of transcatheter aortic valve replacement (TAVR) technology, bioprosthetic heart valves (BHVs) originating from the decellularized bovine pericardium (DBP) have become a favourable option for severe valvular heart disease (VHD). However, currently, available commercial bioprosthetic heart valves prepared from glutaraldehyde (GA)-crosslinked xenografts have limited durability because of various factors, including severe cytotoxicity, inflammatory response, poor pro-endothelialization ability and calcification. Therefore, the development of valve materials with better performance is urgent. In this work, we first synthesized Cu-doped carbon dots (CuCDs) with excellent biocompatibility and high stability using sodium citrate, ethylenediamine and copper chloride. Subsequently, oxidized chondroitin sulfate (OCS) was used to crosslink the decellularized bovine pericardium to obtain OCS-BP followed by loading CuCDs onto the surface of this OCS-fixed BP sample through amide bonds formed by an EDC/NHS-catalyzed reaction between the functional groups on CuCDs and OCS-BP to prepare the BHV (CuCDs-OCS-BP) with specific properties. Relevant experiments conducted both in vivo and in vitro indicate that CuCDs-OCS-BP with good stability showed improved mechanical properties, compliance and flexibility, encouraging HUVEC-cytocompatibility, excellent anti-blood cell adhesion, antithrombogenic properties, anti-inflammatory and anti-calcification properties, and a good endothelialisation ability due to the catalytic generation of endogenous nitric oxide. Overall, CuCDs-OCS-BP is a promising material for BHVs.

Fabrication of an Antibacterial/Anticoagulant Dual-Functional Surface for Left Ventricular Assist Devices via Mussel-Inspired Polydopamine Chemistry

Infections and thrombosis remain unsolved problems for implanted cardiovascular devices, such as left ventricular assist devices. Hence, the development of surfaces with improved blood compatibility and antimicrobial properties is imperative to reduce complications after artificial heart implantation. In this work, we report a novel approach to fabricate multifunctional surfaces for left ventricular transplanted ventricular assist devices (LVADs) by immobilizing nitric oxide (NO) generation catalysts and heparin and reducing silver nanoparticles in situ. The general view, structure, and chemical compositions of the pure/modified surfaces were characterized using digital imaging, scanning electron microscope (SEM), atomic force microscope (AFM), water contact angle (WCA), X-ray photoelectron spectroscopy (XPS), and inductively coupled plasma (ICP). All of the results demonstrated that the AgNPs and heparin were successfully immobilized on the surface. The Cu ions and NO release experimental results showed that the immobilized copper ions could catalyze the production of NO from S-nitrosothiols within the biological system. Meanwhile, due to the synergistic anticoagulant effect of NO and surface-immobilized heparin, the fabricated modified surfaces exhibited antiplatelet adhesion activities and good hemocompatibility. Finally, the antimicrobial activity of the samples was evaluated by Escherichia coli and Staphylococcus aureus, and cytocompatibility was measured using human umbilical vein endothelial cells (HUVECs). The results demonstrated that silver nanoparticles (AgNPs) immobilized by surface reduction reaction did not cause any significant inhibition of cell proliferation while providing stable and effective antimicrobial properties. We envision that this simple surface modification strategy with bifunctional activities of antimicrobial and anticoagulant will find widespread use in clinically used indwelling left ventricular assist devices.

Multifunctional nanoplatform with near-infrared triggered nitric-oxide release for enhanced tumor ferroptosis

Ferroptosis has emerged as a promising strategy for cancer treatment. Nevertheless, the efficiency of ferroptosis-mediated therapy remains a challenge due to high glutathione (GSH) levels and insufficient endogenous hydrogen peroxide in the tumor microenvironment. Herein, we presented a nitric-oxide (NO) boost-GSH depletion strategy for enhanced ferroptosis therapy through a multifunctional nanoplatform with near-infrared (NIR) triggered NO release. The nanoplatform, IS@ATF, was designed that self-assembled by loading the NO donor L-arginine (L-Arg), ferroptosis inducer sorafenib (SRF), and indocyanine green (ICG) onto tannic acid (TA)-Fe3+‒metal-phenolic networks (MPNs) modified with hydroxyethyl starch. Inside the tumor, SRF could inhibit GSH biosynthesis, impair the activation of glutathione peroxidase 4, and disrupt the ferroptosis defensive system. In conjunction with TA-Fe3+‒MPNs, which has cascaded Fenton catalytic activity, it could navigate the lethal ferroptosis to cancer cells. Upon NIR laser irradiation, the ICG-generated ROS oxidated L-Arg to a substantial quantity of NO, which further depleted the intracellular GSH and caused LPO accumulation, enhancing cell ferroptosis. Moreover, ICG also serves as a photothermal agent that can produce hyperthermia when exposed to irradiation, further potentiating ferroptosis therapy. In addition, the nanoplatform showed significantly improved tumor therapeutic efficacy and anti-metastasis efficiency. This work thus demonstrated that utilizing NO boost-GSH depletion to enhance ferroptosis induction is a feasible and promising strategy for cancer treatment.

Endothelium-Mimicking Materials: A "Rising Star" for Antithrombosis

The advancement of antithrombotic materials has significantly mitigated the thrombosis issue in clinical applications involving various medical implants. Extensive research has been dedicated over the past few decades to developing blood-contacting materials with complete resistance to thrombosis. However, despite these advancements, the risk of thrombosis and other complications persists when these materials are implanted in the human body. Consequently, the modification and enhancement of antithrombotic materials remain pivotal in 21st-century hemocompatibility studies. Previous research indicates that the healthy endothelial cells (ECs) layer is uniquely compatible with blood. Inspired by bionics, scientists have initiated the development of materials that emulate the hemocompatible properties of ECs by replicating their diverse antithrombotic mechanisms. This review elucidates the antithrombotic mechanisms of ECs and examines the endothelium-mimicking materials developed through single, dual-functional and multifunctional strategies, focusing on nitric oxide release, fibrinolytic function, glycosaminoglycan modification, and surface topography modification. These materials have demonstrated outstanding antithrombotic performance. Finally, the review outlines potential future research directions in this dynamic field, aiming to advance the development of antithrombotic materials.

Computer-aided nanodrug discovery: recent progress and future prospects

Nanodrugs, which utilise nanomaterials in disease prevention and therapy, have attracted considerable interest since their initial conceptualisation in the 1990s. Substantial efforts have been made to develop nanodrugs for overcoming the limitations of conventional drugs, such as low targeting efficacy, high dosage and toxicity, and potential drug resistance. Despite the significant progress that has been made in nanodrug discovery, the precise design or screening of nanomaterials with desired biomedical functions prior to experimentation remains a significant challenge. This is particularly the case with regard to personalised precision nanodrugs, which require the simultaneous optimisation of the structures, compositions, and surface functionalities of nanodrugs. The development of powerful computer clusters and algorithms has made it possible to overcome this challenge through in silico methods, which provide a comprehensive understanding of the medical functions of nanodrugs in relation to their physicochemical properties. In addition, machine learning techniques have been widely employed in nanodrug research, significantly accelerating the understanding of bio-nano interactions and the development of nanodrugs. This review will present a summary of the computational advances in nanodrug discovery, focusing on the understanding of how the key interfacial interactions, namely, surface adsorption, supramolecular recognition, surface catalysis, and chemical conversion, affect the therapeutic efficacy of nanodrugs. Furthermore, this review will discuss the challenges and opportunities in computer-aided nanodrug discovery, with particular emphasis on the integrated "computation + machine learning + experimentation" strategy that can potentially accelerate the discovery of precision nanodrugs.

Recent Advancements in Polymeric N-Nitrosamine-Based Nitric Oxide (NO) Donors and their Therapeutic Applications

Nitric oxide (NO), a gasotransmitter, is known for its wide range of effects in vasodilation, cardiac relaxation, and angiogenesis. This diatomic free radical also plays a pivotal role in reducing the risk of platelet aggregation and thrombosis. Furthermore, NO demonstrates promising potential in cancer therapy as well as in antibacterial and antibiofilm activities at higher concentrations. To leverage their biomedical activities, numerous NO donors have been developed. Among these, N-nitrosamines are emerging as a notable class, capable of releasing NO under suitable photoirradiation and finding a broad range of therapeutic applications. This review discusses the design, synthesis, and biological applications of polymeric N-nitrosamines, highlighting their advantages over small molecular NO donors in terms of stability, NO payload, and target-specific delivery. Additionally, various small-molecule N-nitrosamines are explored to provide a comprehensive overview of this burgeoning field. We anticipate that this review will aid in developing next-generation polymeric N-nitrosamines with improved physicochemical properties.

Platelet Membrane Coated Cu9S8-SNAP for Targeting NIR-II Mild Photothermal Enhanced Chemodynamic/Gas Therapy of Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a highly aggressive and uncommon subtype of breast cancer with a poor prognosis. It is crucial to prioritise the creation of a nanotherapeutic method that is highly selective and actively targeting TNBC. This study explores a new nanosystem, Cu9S8-SNAP@PM (C-S@P), composed of Cu9S8-SNAP coated with a platelet membrane (PM). The purpose of this nanosystem is to cure TNBC using multimodal therapy. The utilisation of PM-coated nanoparticles (NPs) enables active targeting, leading to the efficient accumulation of C-S@P within the tumour. The Cu9S8 component within these NPs serves the potential to exert photothermal therapy (PTT) and chemodynamic therapy (CDT). Simultaneously, the S-Nitroso-N-Acetylvanicillamine (SNAP) component enables nitric oxide (NO) gas therapy (GT). Furthermore, when exposed to NIR-II laser light, Cu9S8 not only increases the temperature of the tumour area for PTT, but also boosts CDT and stimulates the release of NO through thermal reactions to improve the effectiveness of GT. Both in vitro and in vivo experimental results validate that C-S@P exhibits minimal side effects and represents a multifunctional nano-drug targeted at tumors for efficient treatment. This approach promises significant potential for TNBC therapy and broader applications in oncology.

Nanomaterials-Induced Redox Imbalance: Challenged and Opportunities for Nanomaterials in Cancer Therapy

Cancer cells typically display redox imbalance compared with normal cells due to increased metabolic rate, accumulated mitochondrial dysfunction, elevated cell signaling, and accelerated peroxisomal activities. This redox imbalance may regulate gene expression, alter protein stability, and modulate existing cellular programs, resulting in inefficient treatment modalities. Therapeutic strategies targeting intra- or extracellular redox states of cancer cells at varying state of progression may trigger programmed cell death if exceeded a certain threshold, enabling therapeutic selectivity and overcoming cancer resistance to radiotherapy and chemotherapy. Nanotechnology provides new opportunities for modulating redox state in cancer cells due to their excellent designability and high reactivity. Various nanomaterials are widely researched to enhance highly reactive substances (free radicals) production, disrupt the endogenous antioxidant defense systems, or both. Here, the physiological features of redox imbalance in cancer cells are described and the challenges in modulating redox state in cancer cells are illustrated. Then, nanomaterials that regulate redox imbalance are classified and elaborated upon based on their ability to target redox regulations. Finally, the future perspectives in this field are proposed. It is hoped this review provides guidance for the design of nanomaterials-based approaches involving modulating intra- or extracellular redox states for cancer therapy, especially for cancers resistant to radiotherapy or chemotherapy, etc.

Nitric Oxide‐Based Nanomedicines for Conquering TME Fortress: Say “NO” to Insufficient Tumor Treatment

Almost all cancer treatments are significantly limited by the strong tumor microenvironment (TME) fortress formed by abnormal vasculature, dense extracellular matrix (ECM), multidrug resistance (MDR) system, and immune “cold” environment. In the huge efforts of dismantling the TME fortress, nitric oxide (NO)‐based nanomedicines are increasingly occupying a central position and have already been identified as super “strong polygonal warriors” to dismantle TME fortress for efficient cancer treatment, benefiting from NO's unique physicochemical properties and extremely fascinating biological effects. However, there is a paucity of systematic review to elaborate on the progress and fundamental mechanism of NO‐based nanomedicines in oncology from this aspect. Herein, the key characteristics of TME fortress and the potential of NO in reprogramming TME are delineated and highlighted. The evolution of NO donors and the advantages of NO‐based nanomedicines are discussed subsequently. Moreover, the latest progress of NO‐based nanomedicines for solid tumors is comprehensively reviewed, including normalizing tumor vasculature, overcoming ECM barrier, reversing MDR, and reactivating the immunosuppression TME. Lastly, the prospects, limitations, and future directions on NO‐based nanomedicines for TME manipulation are discussed to provide new insights into the construction of more applicable anticancer nanomedicines.

A Self-Adaptive Biomimetic Periosteum Employing Nitric Oxide Release for Augmenting Angiogenesis in Bone Defect Regeneration

The periosteum plays a vital role in the regeneration of critical-size bone defects and highly comminuted fractures, promoting the differentiation of osteoblasts, accelerating the reconstruction of the vascular network, and guiding bone tissue regeneration. However, the materials loaded with exogenous growth factors are limited by the release and activity of the elements. Therefore, the material structure must be carefully designed for the periosteal function. Here, a self-adaptive biomimetic periosteum strategy is proposed, which is a novel interpenetrating double network hydrogel consisting of diselenide-containing gelatin and calcium alginate (modified natural collagen and polysaccharide) to enhance the stability, anti-swelling, and delayed degradation of the hydrogel. The diselenide bond continuously releases nitric oxide (NO) by metabolizing endogenous nitrosated thiols (RSNO), activates the nitric oxide-cycle guanosine monophosphate (NO-cGMP) signal pathway, coordinates the coupling effect of angiogenesis and osteogenesis, and accelerates the repair of bone defects. This self-adaptive biomimetic periosteum with the interpenetrating double network structure formed by the diselenide-containing gelatin and calcium alginate has been proven to be safe and effective in repairing critical-size bone defects and is expected to provide a promising strategy for solving clinical problems.