Bioinspired Antioxidant Defense System Constructed by Antioxidants-Eluting Electrospun F127-Based Fibers

Inflammation-responsive PCL/gelatin microfiber scaffold with sustained nitric oxide generation and heparin release for blood-contacting implants

Delayed endothelialization, the excessive proliferation of smooth muscle cells (SMCs), and persistent inflammation are the main reasons for the implantation failure of blood-contacting materials. To overcome this problem, an inflammation-responsive, core-shell structured microfiber scaffold is developed using polycaprolactone (PCL), selenocystamine-modified gelatin (Gel-Se), L-ascorbyl 6-palmitate (AP), and dexamethasone as the fiber shell, with poly (l-lysine) (PLL) and heparin incorporated in the fiber core. Superhydrophilic microfiber scaffolds exhibit antifouling properties that inhibit protein adsorption and blood cell adhesion, thereby effectively mitigating the risk of acute thrombosis. The continuous release of heparin and sustained generation of nitric oxide (NO) through the catalytic decomposition of S-nitrosothiols by selenocystamine lead to a biomimetic endothelial function for the enhancement of blood compatibility. The inflammation-responsive compound AP can detoxify excess reactive oxygen species (ROS) while controlling the release of dexamethasone to reduce chronic inflammation. We demonstrate the ability of microfiber scaffolds to reduce thrombotic and inflammatory complications, inhibit SMC proliferation, and promote rapid endothelialization both in vitro and ex vivo. Hence, microfiber scaffolds are robust and promising for blood-contacting implants with enhanced antithrombogenicity and anti-inflammatory capabilities.

NADH Photosynthesis System with Affordable Electron Supply and Inhibited NADH Oxidation

Photosynthesis offers a green approach for the recycling of nicotinamide cofactors primarily NADH in bio-redox reactions. Herein, we report an NADH photosynthesis system where the oxidation of biomass derivatives is designed as an electron supply module (ESM) to afford electrons and superoxide dismutase/catalase (SOD/CAT) cascade catalysis is designed as a reactive oxygen species (ROS) elimination module (REM) to inhibit NADH degradation. Glucose as the electron donor guarantees the reaction sustainability accompanied with oxidative products of gluconic acid and formic acid. Meanwhile, enzyme cascades of SOD/CAT greatly eliminate ROS, leading to a ≈2.00-fold elevation of NADH yield (61.1 % vs. 30.7 %). The initial reaction rate and turnover frequency (TOF) increased by 2.50 times and 2.54 times, respectively, compared with those systems without REM. Our study establishes a novel and efficient platform for NADH photosynthesis coupled to biomass-to-chemical conversion.

ROS-responsive PPGF nanofiber membrane as a drug delivery system for long-term drug release in attenuation of osteoarthritis

Excessive reactive oxygen species (ROS) are one of the leading mechanisms in the initiation and development of osteoarthritis (OA). However, conventional injection of ROS-responsive drug delivery systems (DDSs) such as nanoparticles and hydrogels usually cannot provide effective treatment due to rapid clearance and degradation or low bioavailability. In this study, a ROS-responsive nanofiber membrane named PLA/PEGDA-EDT@rGO-Fucoxanthin (PPGF) is fabricated by electrospinning, wherein PEGDA-EDT served as the ROS-responsive motif, reduced graphene oxide (rGO) as the drug carrier and fucoxanthin (Fx) as the antioxidative and anti-inflammatory agent. The results demonstrated that the PPGF nanofiber membrane exhibited sustained and long-term Fx release behavior (at least 66 days) in response to hydrogen peroxide (H₂O₂) in vitro. With low cytotoxicity and smart ROS responsiveness, PPGF showed excellent anti-inflammatory and antioxidative effects on IL-1β-induced chondrocytes by potent ROS scavenging potential and upregulation of antioxidative enzymes. It also demonstrated the attenuation of OA progression with the reduced Osteoarthritis Research Society International (OARSI) score by 93.17% in 8 weeks. The smart ROS-responsive, biodegradable and biocompatible nanofiber membranes possess great potential for OA therapy under arthroscopy.

Nanoarchitectonics of Cartilage-Targeting Hydrogel Microspheres with Reactive Oxygen Species Responsiveness for the Repair of Osteoarthritis

Clinically, intra-articular administration can hardly achieve the truly targeted therapy, and the drugs are usually insufficient to show local and long-term therapeutic effects because of their rapid clearance. Herein, inspired by the phenomenon that bees track the scent of flowers to collect nectar, we developed cartilage-targeting hydrogel microspheres with reactive oxygen species (ROS)-responsive ability via combining the microfluidic method and photopolymerization processes to integrate cartilage-targeting peptides and ROS-responsive nanoparticles in the hydrogel matrix. The hydrogel microspheres with cartilage-targeting properties promoted better retention in the joint cavity and enhanced cellular uptake of the nanoparticles. Moreover, the ROS-responsive nanoparticles could react with osteoarthritis (OA)-induced intracellular ROS, resulting in the depolymerization of nanoparticles, which could not only eliminate excess ROS and reduce inflammation but also promote the release of dexamethasone (Dex) and kartogenin (KGN) in situ, realizing effective OA therapy. It was demonstrated that this hydrogel microsphere showed favorable ROS-responsive ability and enhanced chondrogenic differentiation as well as the downregulation of pro-inflammatory factors in vitro. Additionally, the hydrogel microspheres, similar to bees, could target and effectively repair cartilage in the OA model. Thus, the injectable hydrogel microspheres exerted an excellent potential to repair OA and may also provide an effective avenue for inflammatory bowel disease therapy.

Studies of the Sulfonated Hydrogenated Styrene-Isoprene-Styrene Block Copolymer and Its Surface Properties, Cytotoxicity, and Platelet-Contacting Characteristics

Styrenic thermoplastic elastomers (TPEs) consist of styrenic blocks. They are connected with other soft segments by a covalent linkage and are widely used in human life. However, in biomedical applications, TPEs need to be chemically hydrogenated in advance to enhance their properties such as strong UV/ozone resistance and thermal-oxidative stability. In this study, films composed of sulfonated hydrogenated TPEs were evaluated. Hydrogenated tert-butyl styrene–styrene–isoprene block copolymers were synthesized and selectively sulfonated to different degrees by reaction with acetyl sulfate. By controlling the ratio of the hydrogenated tert-butyl styrene–styrene–isoprene block copolymer and acetyl sulfate, sulfonated films were optimized to demonstrate sufficient mechanical integrity in water as well as good biocompatibility. The thermal plastic sulfonated films were found to be free of cytotoxicity and platelet-compatible and could be potential candidates in biomedical film applications such as wound dressings.

A dynamic remodeling bio-mimic extracellular matrix to reduce thrombotic and inflammatory complications of vascular implants

Thrombotic and inflammatory complications induced by vascular implants remain a challenge to treat cardiovascular disease due to the lack of self-adaption and functional integrity of implants. Inspired by the dynamic remodeling of the extracellular matrix (ECM), we constructed a bio-mimic ECM with a dual-layer nano-architecture on the implant surface to render the surface adaptive to inflammatory stimuli and remodelable possessing long-term anti-inflammatory and anti-thrombotic capability. The inner layer consists of PCL-PEG-PCL [triblock copolymer of polyethylene glycol and poly(ε-caprolactone)]/Au-heparin electrospun fibers encapsulated with indomethacin while the outer layer is composed of polyvinyl alcohol (PVA) and ROS-responsive poly(2-(4-((2,6-dimethoxy-4-methylphenoxy)methyl)phenyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane) (PBA) fibers. In response to acute inflammation after vascular injury, the outer layer reduces ROS rapidly by PBA degradation for inflammation suppression. The degraded outer layer facilitates inner layer reconstruction with enhanced hemocompatibility through the H-bond between PVA and PCL-PEG-PCL. Furthermore, chronic inflammation is effectively depressed with the sustained release of indomethacin from the inner layer. The substantial enhancement of the functional integrity of implants and reduction of thrombotic and inflammatory complications with the self-adaptive ECM are demonstrated both in vitro and in vivo. Our work paves a new way to develop long-term anti-thrombotic and anti-inflammatory implants with self-adaption and self-regulation properties.

Mimic of the Cellular Antioxidant Defense System for a Sustainable Regeneration of Nicotinamide Adenine Dinucleotide (NAD)

The prolonged use of enzymes under oxidative stress is a major challenge in enabling effective enzymatic reaction pathways. Herein, we report a biomimetic antioxidant defensive strategy capable of providing adequate protection of enzymes against superoxide-mediated oxidation. Superoxide dismutase (SOD) and catalase (CAT) were chosen as scavengers and covalently encapsulated into silica nanoreactors, together with glucose dehydrogenase (GDH), which simultaneously should produce the coenzyme nicotinamide adenine dinucleotide (NADH, reduced form). By the enzymatic reactions of SOD and CAT, the interior of silica nanoreactors becomes a "ROS safe zone" to protect the glucose-dependent NADH production of coencapsulated GDH. We further combined this protected NADH-producing module with photocatalytic nanoparticles that enable the light-triggered oxidation of NADH back to NAD⁺ (oxidized form). In combination, these two modules allow interconversion between NAD⁺ and NADH by the addition of glucose or by light irradiation (LED lamp or sunlight). This protection and regeneration strategy is a versatile tool for enzyme applications for biological reactors, catalysis, or prototypes of artificial organelles or building blocks that contains fragile biomolecules and rely on the coenzyme NAD⁺/NADH.

Reduction of thrombotic and inflammatory complications of polystyrene-block-polyisoprene-block-polystyrene (SIS) with one-step electrospinning

Polystyrene-block-polyisoprene-block-polystyrene (SIS) has been used as biomaterials due to its soft and stable properties under physiological conditions. However, the thrombotic and inflammatory complications caused by SIS restrain its application as blood-contacting implant. To overcome this problem, the hydrophilic core-shell structured SIS-based microfiber with antioxidant encapsulation is fabricated with one-step reactive electrospinning. We demonstrate that the phase separation of SIS and acylated Pluronic F127 (F127-DA) components and crosslinking during electrospinning renders the microfiber blood compatible and stable under physiological condition; the encapsulation of 2-O-d-glucopyranosyl-l-ascorbic acid (AA-2G) in microfiber and subsequent release of AA-2G detoxifies the excess reactive oxygen species (ROS). The microfibers are nontoxic to cells and promote the fast growth and proliferation of human umbilical vein endothelial cells (HUVECs) in the presence of ROS; the thrombotic and inflammatory complications are effectively reduced with implant evaluation in vivo. Therefore, our work paves a new way to improve the biocompatibility of SIS, making it a promising candidate for blood contact materials.

Anti-Oxidant in China: A Thirty-Year Journey

Anti-oxidant refers to such a kind of endogenous or exogenous compound that is able to retard or even prohibit in vivo or in vitro oxidation with only small amount being used. The study of anti-oxidants starts nearly 30 years ago, and the research on this topic in China almost begins simultaneously with that in the world. Gratifyingly, contributions on anti-oxidants from China researchers have rapidly increased in the recent decade as anti-oxidants have become a hot topic in biochemistry, pharmacology, food science, chemistry as well as other related disciplines. Anti-oxidants provide a specific viewpoint for clarifying pharmacological effects of Chinese medicinal herbs. For example, as a traditional Chinese medicinal herb, Panax ginseng C. A. Meyer is found to be a natural anti-oxidant resource. Meanwhile, some signaling pathways such as nuclear factor-[Formula: see text]B (NF-[Formula: see text]B), nuclear factor erythroid 2 related factor 2 (Nrf2), and Kelch-like ECH associated protein 1 (Keap1) are regarded to play an important role in anti-oxidant responses. These findings provide a substantial basis for understanding the pharmacological behaviors of Chinese medicinal herbs in view of regulating the aforementioned signaling pathways. Moreover, inhibition of reactive oxygen species (ROS) by supplementation of anti-oxidant becomes a popularly accepted idea in keeping health and treating diseases. Isolations of antio-xidative ingredients from medicinal herbs and foods lead to set up a large range of anti-oxidative compound libraries, and intake of anti-oxidants from foods may be the most efficient way for supplementing exogenous anti-oxidants. On the other hand, designing anti-oxidants with novel structures motivates organic and medicinal chemists to explore the structure–activity relationship, and then, to find novel structural features with anti-oxidative properties. Therefore, it is reasonable to believe that China researchers will donate more endeavors to obtain more achievements on anti-oxidants in the future.

Inhibition of Inflammation-Associated Thrombosis with ROS-Responsive Heparin-DOCA/PVAX Nanoparticles

Inflammation-associated thrombosis is a non-negligible source of mortalities and morbidities worldwide. To manipulate inflammation-associated coagulation, nanoparticles that contain anti-inflammatory polymer (copolyoxalate containing vanillyl alcohol, PVAX) and anti-thrombotic heparin derivative deoxycholic acid (Hep-DOCA) are prepared. The strategy takes advantage of the reducted side effects of heparin through heparin conjugation, achievement of long-term anti-inflammation by inflammation-trigged release of anti-inflammatory agents, and formation of PVAX/heparin-DOCA nanoparticles by co-self-assembly. It is demonstrated that the Hep-DOCA conjugate and PVAX are synthesized successfully; PVAX and Hep-DOCA nanodrugs (HDP) are obtained by co-assembly; the HDP nanoparticles effectively reduce the inflammation and coagulation without inducing lethal bleeding both in vivo and in vitro. The method provided here is versatile and effective, which paves new way to develop nanodrugs to treat inflammation-associated thrombosis safely.

Biomimicking Dual-Responsive Extracellular Matrix Restoring Extracellular Balance through the Na/K-ATPase Pathway

Biomedical implant mimicking the physiological extracellular matrix (ECM) is a new strategy to modulate the cell microenvironment to improve implant integrity and longevity. However, the biomimicking ECM suffers from low sensitivity to pathological change and low efficiency to restore the physiological state in vivo. To overcome these problems, reactive oxygen species (ROS) and K⁺ dual-responsive micro-/nanofibers that encapsulate ascorbic acid-2-glucoside (AA-2G) are fabricated on an elastomer substrate with electrospinning to mimic the ECM. The strategy is based on the fact that ROS and K⁺ dual responsiveness enhance the sensitivity of the ECM to pathological changes and delivery of AA-2G from the ECM to cell membrane promotes reactivating Na/K-ATPase and shifting cellular diseased conditions to the normal state. We demonstrate that the ROS and K⁺-responsive tripolymer of poly(ethylene glycol)diacrylate, 1,2-ethanedithiol, and 4-nitrobenzo-18-crown-6-ether (PEGDA-EDT-BCAm) are synthesized successfully; the ECM composed of acylated poly(caprolactone)/PEGDA-EDT-BCAm/AA-2G micro-/nanofibers is prepared through reactive electrospinning; the ECM is sensitive to ROS and K⁺ concentration in the microenvironment to release AA-2G, which targets the membrane to remove the excessive ROS and reactivate Na/K-ATPase; as a result, the ECM reduces oxidative stress and restores the extracellular physiological state both in vitro and in vivo. This work provides basic principles to design an implant that can adjust the extracellular microenvironment while avoiding pathogenicity to improve implant integrity and longevity in vivo.

Construction of K+ responsive surface on SEBS to reduce the hemolysis of preserved erythrocytes

Hemolysis of stored erythrocytes is a big obstacle for the development of new plasticizer-free polymer containers. Hemolysis is mainly caused by cell membrane oxidation and cation leaks from the intracellular fluid during storage. To construct an anti-hemolytic surface for a plasticizer-free polymer, we fabricated 2-O-α-d-glucopyranosyl-l-ascorbic acid (AA-2G)-loaded polycaprolactone (PCL)-crown ether micro/nanofibers on the surface of styrene-b-(ethylene-co-butylene)-b-styrene (SEBS). Our strategy is based on the sensitive response of the crown ether to leaked potassium, causing the release of AA-2G, the AA-2G can then remove the excess ROS, maintaining the Na/K-pump activity and the cell integrity. We demonstrated that the PCL-crown ether micro/nanofibers have been well prepared on the surface of SEBS; the micro/nanofibers provide a sensitive response to excess K+ and trigger the rapid release of AA-2G. AA-2G then acts as an antioxidant to reduce the excess ROS and maintain the Na/K-pump activity to mitigate cation leaks, resulting in the reduced hemolysis of the preserved erythrocytes. Our work thus provides a novel method for the development of plasticizer-free polymers for the storage of erythrocytes, and has the potential to be used to fabricate long-term anti-hemolytic biomaterials for in vivo use.