Ultrasmall Rhodium Nanozyme with RONS Scavenging and Photothermal Activities for Anti-Inflammation and Antitumor Theranostics of Colon Diseases

Nanozymes for Regenerative Medicine

Nanozymes refer to nanomaterials that catalyze enzyme substrates into products under relevant physiological conditions following enzyme kinetics. Compared to natural enzymes, nanozymes possess the characteristics of higher stability, easier preparation, and lower cost. Importantly, nanozymes possess the magnetic, fluorescent, and electrical properties of nanomaterials, making them promising replacements for natural enzymes in industrial, biological, and medical fields. On account of the rapid development of nanozymes recently, their application potentials in regeneration medicine are gradually being explored. To highlight the achievements in the regeneration medicine field, this review summarizes the catalytic mechanism of four types of representative nanozymes. Then, the strategies to improve the biocompatibility of nanozymes are discussed. Importantly, this review covers the recent advances in nanozymes in tissue regeneration medicine including wound healing, nerve defect repair, bone regeneration, and cardiovascular disease treatment. In addition, challenges and prospects of nanozyme researches in regeneration medicine are summarized.

A Biomarker-Responsive Nanosystem with Colon-Targeted Delivery for Ulcerative Colitis's Detection and Treatment with Optoacoustic/NIR-II Fluorescence Imaging

Ulcerative colitis (UC) is a prevalent idiopathic inflammatory disease which causes such complications as intestinal perforation, obstruction, and bleeding, and thus deleteriously impacting people's normal work and quality of life. Hence, accurate diagnosis of UC is crucial in terms of planning optimal treatment plan. Herein, a pH/reactive oxygen species (ROS) dual-responsive nanosystem (BM@EP) is developed for UC's detection and therapy. BM@EP is composed of a chromophore-drug dyad and the enteric coating. The chromophore-drug dyad (BOD-XT-DHM) is synthesized by linking the chromophore (BOD-XT-BOH) and a flavonoid drug (dihydromyricetin DHM) through boronate ester bond. The enteric coating includes Eudragit S100 and poly(lactic-co-glycolic acid) (PLGA), the former is commonly employed as a pH-dependent polymer coating excipient so as to attain colon-targeted delivery, and the latter has been widely used as an excipient for the controlled-extended release. After oral administration, BM@EP delivers the dyad (BOD-XT-DHM) into the colon and releases the dyad molecules by being triggered by the alkaline pH in t colon, thereafter upon being stimulated by overexpressed H₂ O₂ in the inflamed colon, the boronate bond in the dyad is broken down and correspondingly the drug DHM is released for UC therapy, simultaneously the chromophore is released for near-infrared second window (NIR-II) fluorescence and optoacoustic imaging for UC diagnosis and recovery evaluation.

Pseudocatalytic Hydrogels with Intrinsic Antibacterial and Photothermal Activities for Local Treatment of Subcutaneous Abscesses and Breast Tumors

The intimate relationship between bacteria and tumors has triggered a lot of activities in the development and design of bioactive materials to concurrently respond to antitumor and antibacterial demands. Herein, a pseudocatalytic hydrogel (AM-I@Agar) with intrinsic antibacterial and photothermal activities, synthesized by incorporating prefabricated amylose-iodine nanoparticles into low-melting-point agarose hydrogel, is explored as a bioactive agent for local treatment of subcutaneous abscesses and breast tumors. The AM-I@Agar hydrogel depicts the ability of pseudocatalytic O₂ generation from H₂ O₂ to alleviate hypoxia. Meanwhile, the AM-I@Agar hydrogel exhibits temperature self-regulation features, beneficial for avoiding thermal injury during photothermal therapy owing to thermochromic properties. Upon local injection into a subcutaneous abscess, methicillin-resistant Staphylococcus aureus is effectively eliminated by the AM-I@Agar hydrogel, and complete skin recovery is achieved in 8 d, demonstrating much better antibacterial effects compared with penicillin, a small-molecule antibiotic. AM-I/5-FU@Agar hydrogel, obtained after loading 5-fluorouracil (5-FU), significantly inhibits tumors in both normal 4T1 tumor-bearing mice and MRSA-infected 4T1 tumor-bearing mice models via a synergistic photothermal-chemo effect, and shows treatment efficiency superior to that achieved with photothermal therapy or 5-FU alone. This work provides a concept for the design and development of bioactive agents for potential management of bacteria-associated cancer.

'Switch to love, switch to kill-dose and light co-regulate iron single-atom nanozyme to modulate cell fate

Remote control of cells and the regulation of cell events at the molecular level are of great interest to the biomedical field. In addition to mechanical forces and genes, chemical compounds and light play pivotal roles in regulating cell fate, which have boosted the fast growth of biology. Herein, we synthesized light-regulated, atomically dispersed Fe-N₄immobilized on a carbon substrate nanozyme (Fe-N/C single atom catalysts), whose peroxidase- and catalase-like properties can be enhanced by 120% and 135%, respectively, under 808-nm laser irradiation through the photothermal effect of Fe-N/C. Interestingly, a switch to love/switch to kill interaction between Fe-N/C dose and near-infrared (NIR) light co-regulating the Fe-N/C nanozyme to modulate cell fate was discovered. Based on this, we found that under NIR light irradiation, when the dose of Fe-N/C is low, it can scavenge more reactive oxygen species (ROS) and achieve cell protection; when the dose of Fe-N/C is too high, it tended to lead to cell apoptosis. This work not only provides an effective strategy for the regulation of nanozyme activity but also realizes the dual-functional application of nanozyme materials for the treatment of some specific diseases.

Nanotechnology for research and treatment of the intestine

The establishment of intestinal in vitro models is crucial for elucidating intestinal cell-microbe intrinsic connections and interaction mechanisms to advance normalized intestinal diagnosis and precision therapy. This review discusses the application of nanomaterials in mucosal therapy and mechanism research in combination with the study of nanoscaffold in vitro models of the gut. By reviewing the original properties of nanomaterials synthesized by different physicochemical principles and modifying the original properties, the contribution of nanomaterials to solving the problems of short survival period, low cell differentiation rate, and poor reduction ability in traditional intestinal models is explored. According to nanomaterials’ different diagnostic mediators and therapeutic targets, the current diagnostic principles in inflammatory bowel disease, intestinal cancer, and other diseases are summarized inductively. In addition, the mechanism of action of nanomedicines in repairing mucosa, inhibiting inflammation, and alleviating the disease process is also discussed. Through such systematic elaboration, it offers a basis for nanomaterials to help advance in vitro research on the intestine and provide precision treatments in the clinic.

Harnessing immune response using reactive oxygen Species-Generating/Eliminating inorganic biomaterials for disease treatment

With the increasing understanding of various biological functions mediated by reactive oxygen species (ROS) in the immune system, a number of studies have been designed to develop ROS-generating/eliminating strategies to selectively modulate immunogenicity for disease treatment. These strategies potentially exploit ROS-modulating inorganic biomaterials to harness host immunity to maximize the therapeutic potency by eliciting a favorable immune response. Inorganic biomaterial-guided in vivo ROS scavenging can exhibit several effects to: i) reduce the secretion of pro-inflammatory factors, ii) induce the phenotypic transition of macrophages from inflammatory M1 to immunosuppressive M2 phase, iii) minimize the recruitment and infiltration of immune cells. and/or iv) suppress the activation of nuclear factor kappa-B (NF-κB) pathway. Inversely, ROS-generating inorganic biomaterials have been found to be capable of: i) inducing immunogenic cell death (ICD), ii) reprograming tumor-associated macrophages from M2 to M1 phenotypes, iii) activating inflammasomes to stimulate tumor immunogenicity, and/or iv) recruiting phagocytes for antimicrobial therapy. This review provides a systematic and up-to-date overview on the progress related to ROS-nanotechnology mediated immunomodulation. We highlight how the ROS-generating/eliminating inorganic biomaterials can converge with immunomodulation and ultimately elicit an effective immune response against inflammation, autoimmune diseases, and/or cancers. We expect that contents presented in this review will be beneficial for the future advancements of ROS-based nanotechnology and its potential applications in this evolving field.

NIR-PTT/ROS-Scavenging/Oxygen-Enriched Synergetic Therapy for Rheumatoid Arthritis by a pH-Responsive Hybrid CeO2-ZIF-8 Coated with Polydopamine

Rheumatoid arthritis (RA) is an inflammatory type of arthritis that causes joint pain and damage. The inflammatory cell infiltration (e.g., M1 macrophages), the poor O₂ supply at the joint, and the excess reactive oxygen species (ROS)-induced oxidative injury are the main causes of RA. We herein report a polydopamine (PDA)-coated CeO₂-dopped zeolitic imidazolate framework-8 (ZIF-8) nanocomposite CeO₂-ZIF-8@PDA (denoted as CZP) that can synergistically treat RA. Under near-infrared (NIR) light irradiation, PDA efficiently scavenges ROS and results in an increased temperature in the inflamed area because of its good light-to-heat conversion efficiency. The rise of temperature serves to obliterate hyper-proliferative inflammatory cells accumulated in the diseased area while vastly promoting the collapse of the acidic-responsive skeleton of ZIF-8 to release the encapsulated CeO₂. The released CeO₂ exerts its catalase-like activity to relieve hypoxia by generating oxygen via the decomposition of H₂O₂ highly expressed in the inflammatory sites. Thus, the constructed CZP composite can treat RA through NIR-photothermal/ROS-scavenging/oxygen-enriched combinative therapy and show good regression of pro-inflammatory cytokines and hypoxia-inducible factor-1α (HIF-1α) in vitro and promising therapeutic effect on RA in rat models. The multimodal nano-platform reported herein is expected to shed light on the design of synergistic therapeutic nanomedicine for effective RA therapy.

Radicals Scavenging MOFs Enabling Targeting Delivery of siRNA for Rheumatoid Arthritis Therapy

Macrophages play essential roles in the progression of rheumatoid arthritis (RA), which are polarized into the pro-inflammatory M1 phenotype with significant oxidative stress and cytokines excretion. Herein, an active targeting nanomedicine based on metal-organic frameworks (MOFs) to re-educate the diseased macrophages for RA therapy is reported. The MOFs are prepared via coordination between tannic acid (TA) and Fe³⁺ , and anti-TNF-α siRNA is loaded via a simple sonication process, achieving high loading capacity comparable to cationic vectors. The MOFs show excellent biocompatibility, and enable rapid endo/lysosome escape of siRNA via the proton-sponge effect for effective cytokines down-regulation. Importantly, such nanomedicine displays intrinsic radicals scavenging capability to eliminate a broad spectrum of reactive oxygen and nitrogen species (RONS), which in turn repolarizes the M1 macrophages into anti-inflammatory M2 phenotypes for enhanced RA therapy in combination with siRNA. The MOFs are further modified with bovine serum albumin (BSA) to allow cascade RA joint and diseased macrophages targeted delivery. As a result, an excellent anti-RA efficacy is achieved in a collagen-induced arthritis mice model. This work provides a robust gene vector with great translational potential, and offers a vivid example of rationally designing MOF structure with multifunctionalities to synergize with its payload for enhanced disease treatment.

Zn-dipicolylamine-based reactive oxygen species-responsive lipids for siRNA delivery and in vivo colitis treatment

The reduction of ROS and inflammatory factor levels plays important role in the treatment of colitis. A series of ROS-responsive lipids (ZnDPA-R) based on the thioketal structure were designed and synthesized. It was hoped that the lipidic materials could combine ROS consumption and siRNA delivery capacity to achieve synergistic treatment of colitis. The target liposomes could combine with the phosphate backbone of siRNA to form lipoplexes with the size of ∼100 nm, and could deliver siRNA cargo into the cell. The results of in vitro anti-inflammatory experiments showed that the lipids may effectively consume ROS in cells. Meanwhile, the lipoplexes significantly reduced the expression levels of TNF-α mRNA and related inflammatory factors in macrophages. After PEGylation, the lipoplex was used for the treatment of mouse colitis, and biodistribution results proved that the lipoplexes effectively aggregated in the intestine. The delivery system could not only response to the high ROS level at colitis via thioketal breaking, but also could assist in the treatment of inflammation by ROS consumption. The treatment results revealed that the levels of TNF-α mRNA and related inflammatory factors at the colon lesion were largely reduced, and the inflammatory symptoms were significantly relieved. Hematology test results indicated that the treatment was safe and induced no obvious side effects on mice. This study may shed light on the synergistic treatment for colitis via anti-inflammatory siRNA delivery and ROS depletion strategies. STATEMENT OF SIGNIFICANCE: Downregulation of inflammatory factors and reactive oxygen species (ROS) levels is critical in treating colitis. In the present study, a series of ROS-responsive lipid molecules based on the Zn-DPA headgroup and thioketal linkage were synthesized for delivering TNF-α siRNA and for treating colitis. In addition to silencing the expression of TNF-α mRNA and the related inflammatory factors, the material also achieved synergistic treatment by simultaneous consumption of ROS in the colon lesion. In vitro cell experiments and in vivo colitis treatment in mice showed that the lipoplex exerted a satisfactory therapeutic effect on colitis, and the symptoms of colitis in mice were significantly alleviated. The present study may shed light on the synergistic treatment for colitis through anti-inflammatory siRNA delivery and ROS depletion strategies.

In situ synthesis of Co-doped MoS2 nanosheet for enhanced mimicking peroxidase activity

To enhance the catalytic activity of two-dimensional layered materials as versatile materials, the modification of transition metal dichalcogenide nanosheets such as MoS₂ by doping with heteroatoms has drawn great interests. However, few reports are available on the study of the enzyme-like activity of doped MoS₂. In this study, a facile in situ hydrothermal method for the preparation of various ultrathin transition metals (Fe, Cu, Co, Mn, and Ni) doped MoS₂ nanosheets has been reported. Through the density functional theory (DFT) and steady-state kinetic analysis, the Co-doped MoS₂ nanosheets exhibited the highest peroxidase-like catalytic activity among them. Furthermore, a typical colorimetric assay for H₂O₂ was presented based on the catalytic oxidation of colorless 3,3',5,5'-tetramethylbenzidine (TMB) to a blue product (oxTMB) by Co-MoS₂. The proposed colorimetric method showed excellent tolerance under extreme conditions and a broad linear range from 0.0005 to 25 mM for H₂O₂ determination. Concerning the practical application, in situ detection of H₂O₂ generated from SiHa cells was also fulfilled, fully confirming the great practicability of the proposed method in biosensing fields.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10853-022-07201-z.

Biodegradable MoSe2-polyvinylpyrrolidone nanoparticles with multi-enzyme activity for ameliorating acute pancreatitis

Exogenous antioxidant materials mimicking endogenous antioxidant systems are commonly used for the treatment of oxidative stress-induced injuries. Thus, artificial enzymes have emerged as promising candidates for balancing and treating the dysregulation of redox homeostasis in vivo. Herein, a one-pot hydrothermal strategy for the facile preparation of MoSe₂-polyvinylpyrrolidone (PVP) nanoparticles (NPs) is reported. The synthesized NPs were biodegradable due to their exposure to oxygen and exhibited high stability. Moreover, they effectively mimicked various naturally occurring enzymes (including catalase, superoxide dismutase, peroxidase, and glutathione peroxidase) and scavenged free radicals, such as 3-ethylbenzothiazoline-6-sulfonic acid, ·OH, ·O²⁻, and 1,1-diphenyl-2-picrylhydrazyl radical. Further apoptosis detection studies revealed that MoSe₂-PVP NPs significantly increased the cell survival probability in H₂O₂ in a concentration-dependent manner. The cytoprotective effect of MoSe₂-PVP NPs was explored for an animal model of acute pancreatitis, which confirmed its remarkable therapeutic efficacy. Owing to the biodegradable and biocompatible nature of MoSe₂-PVP NPs, the findings of this work can stimulate the development of other artificial nanoenzymes for antioxidant therapies.

Catalytic antimicrobial therapy using nanozymes

Nanozymes are nanomaterials with enzyme-like characteristics, which catalyze the conversion of enzyme substrates and follow enzymatic kinetics under physiological conditions. As a new generation of artificial enzymes, nanozymes provide alternative approaches for those upon enzymatic catalysis. Compared with natural enzymes, nanozymes have the advantages of simple preparation, good stability and low cost, which makes nanozymes promising for application in many fields, such as antimicrobial infection treatment. Many studies have reported that nanozymes are capable of killing a number of pathogenic bacteria with resistance, fungi as well as viruses, and have shown great curative effects for diseases caused by these pathogens. Herein, we summarize the application of nanozymes for antibacterial, antiviral, and antifungal therapies and outline the issues needing resolution in the future. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease.

Design of therapeutic biomaterials to control inflammation

Inflammation plays an important role in the response to danger signals arising from damage to our body and in restoring homeostasis. Dysregulated inflammatory responses occur in many diseases, including cancer, sepsis and autoimmunity. The efficacy of anti-inflammatory drugs, developed for the treatment of dysregulated inflammation, can be potentiated using biomaterials, by improving the bioavailability of drugs and by reducing side effects. In this Review, we first outline key elements and stages of the inflammatory environment and then discuss the design of biomaterials for different anti-inflammatory therapeutic strategies. Biomaterials can be engineered to scavenge danger signals, such as reactive oxygen and nitrogen species and cell-free DNA, in the early stages of inflammation. Materials can also be designed to prevent adhesive interactions of leukocytes and endothelial cells that initiate inflammatory responses. Furthermore, nanoscale platforms can deliver anti-inflammatory agents to inflammation sites. We conclude by discussing the challenges and opportunities for biomaterial innovations in addressing inflammation.

Application and Utility of Liposomal Neuroprotective Agents and Biomimetic Nanoparticles for the Treatment of Ischemic Stroke

Ischemic stroke is still one of the leading causes of high mortality and severe disability worldwide. Therapeutic options for ischemic stroke and subsequent cerebral ischemia/reperfusion injury remain limited due to challenges associated with drug permeability through the blood-brain barrier (BBB). Neuroprotectant delivery with nanoparticles, including liposomes, offers a promising solution to address this problem, as BBB disruption following ischemic stroke allows nanoparticles to pass through the intercellular gaps between endothelial cells. To ameliorate ischemic brain damage, a number of nanotherapeutics encapsulating neuroprotective agents, as well as surface-modified nanoparticles with specific ligands targeting the injured brain regions, have been developed. Combination therapy with nanoparticles encapsulating neuroprotectants and tissue plasminogen activator (t-PA), a globally approved thrombolytic agent, has been demonstrated to extend the narrow therapeutic time window of t-PA. In addition, the design of biomimetic drug delivery systems (DDS) employing circulating cells (e.g., leukocytes, platelets) with unique properties has recently been investigated to overcome the injured BBB, utilizing these cells’ inherent capability to penetrate the ischemic brain. Herein, we review recent findings on the application and utility of nanoparticle DDS, particularly liposomes, and various approaches to developing biomimetic DDS functionalized with cellular membranes/membrane proteins for the treatment of ischemic stroke.

Nanoparticles in Clinical Translation for Cancer Therapy

The advent of cancer therapeutics brought a paradigm shift from conventional therapy to precision medicine. The new therapeutic modalities accomplished through the properties of nanomaterials have extended their scope in cancer therapy beyond conventional drug delivery. Nanoparticles can be channeled in cancer therapy to encapsulate active pharmaceutical ingredients and deliver them to the tumor site in a more efficient manner. This review enumerates various types of nanoparticles that have entered clinical trials for cancer treatment. The obstacles in the journey of nanodrug from clinic to market are reviewed. Furthermore, the latest developments in using nanoparticles in cancer therapy are also highlighted.

Silk fibroin-capped metal-organic framework for tumor-specific redox dyshomeostasis treatment synergized by deoxygenation-driven chemotherapy

Disturbance in redox homeostasis always leads to oxidative damages to cellular components, which inhibits cancer cell proliferation and causes tumor regression. Therefore, synergistic effects arising from cellular redox imbalance together with other treatment modalities are worth further investigation. Herein, a metal-organic framework nanosystem (NMOF) based on coordination between Fe (III) and 4,4,4,4-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TCPP) was synthesized through a one-pot method. After surface capping of silk fibroin (SF) to form NMOF@SF nanoparticles (NPs), this nanoplatform can serve as an eligible nanocarrier to deliver tirapazamine (TPZ), a hypoxia-activated precursor. As-developed NS@TPZ (NST) NPs remained inactive in the normal tissue, whereas became highly active upon endocytosis by tumor cells via glutathione (GSH)-mediated reduction of Fe (III) into Fe (II), further enabling Fe (II)-mediated chemodynamic therapy (CDT). Upon optical laser irradiation, TCPP-mediated photodynamic therapy (PDT) coordinated with CDT to aggravate intracellular oxidative stress. Thus, such reactive oxygen species accumulation and GSH deprivation contributed to a deleterious redox dyshomeostasis. On the other hand, local deoxygenation caused by PDT can increase the cytotoxicity of released TPZ, which significantly improved the integral therapeutic effectiveness relying on the combined redox balance disruption and bioreductive chemotherapy. More importantly, severe immunogenic cell death can be triggered by the combinatorial treatment modalities and the presence of SF, which facilitated an almost complete tumor eradication in vivo. Taken together, this paradigm provides an insightful strategy for tumor-specific redox dyshomeostasis treatment synergized by deoxygenation-driven chemotherapy, which can remarkably enhance antitumor efficacy with negligible adverse effects. STATEMENT OF SIGNIFICANCE: Recently, silk fibroin (SF) has been demonstrated to be effective in activating antitumor immune system through polarization tumor-associated macrophages into M1 subtype. However, engineering SF into multifunctional nanocomposites is seldom reported for combination tumor therapy. In another aspect, disruption of redox homeostasis becomes increasingly attractive for tumor suppression with high clinical-relevance. Herein, we established a newfashioned NMOF nanosystem, named as NST, for tumor-specific redox dyshomeostasis treatment synergized by deoxygenation-driven chemotherapy. This platform takes advantages of Fe²⁺/Fe³⁺ coupled Fenton-like reaction and GSH depletion, as well as TCPP-mediated photosensitization for admirable redox unbalancing, which further initiates hypoxia-relevant toxin of TPZ for chemotherapy. Finally, combinatorial treatments and the presence of SF could trigger ICD for rendering a complete tumor eradication in vivo.

Self-Cascade Uricase/Catalase Mimics Alleviate Acute Gout

Uricase-based therapies are limited for gout partially due to the accumulation of H2O2 in an arthrosis environment with slow metabolism. To tackle this limitation, previous studies adopted a cascade reaction between the degradation of uric acid (UA) and timely elimination of H2O2 using complicated composites of uricase and catalase (CAT)/CAT-like nanozyme. Herein, the self-cascade nanozyme Pt/CeO2 with high efficiency toward simultaneous UA degradation and H2O2 elimination is demonstrated on the basis of both uricase- and CAT-like activities in Pt, Ir, Rh, and Pd platinum-group metals. With an optimized molar ratio of Pt and CeO2, Pt/CeO2 (1/5) not only does better in degrading UA but also has excellent reactive oxygen species (ROS) and reactive nitrogen species (RNS) scavenging activities. In monosodium urate (MSU)-induced acute gout rats, Pt/CeO2 nanozyme markedly alleviates pain along with joint edema, thus improving gait claudication and tissue inflammation. These results provide novel insights into strategies of an efficient enzyme-mimetic treatment for gout.

Pillararene-functionalized rhodium nanoparticles for efficient catalytic reduction and photothermal sterilization

Pillar[5]arene-functionalized rhodium nanoparticles are prepared for catalytic reduction of toxic nitrophenols and azo dyes and efficient photothermal sterilization.

Oral Nanozyme-Engineered Probiotics for the Treatment of Ulcerative Colitis

Background: Probiotic-based therapy for ulcerative colitis (UC) is a novel and promising approach that has gained much popularity in recent years. However, probiotics may be easily captured and destroyed by...

The functional role of sulforaphane in intestinal inflammation: a review

Intestinal inflammation represented by inflammatory bowel disease (IBD) has become a global epidemic disease and the number of patients with IBD continues to increase. This digestive tract disease not only affects the absorption of food components by destroying the intestinal epithelial structure, but also can induce diseases in remote organs via the gut-organ axis, seriously harming human health. Nowadays, increasing attention is being paid to the nutritional and medicinal value of food components with increasing awareness among the general public regarding health. As an important member of the isothiocyanates, sulforaphane (SFN) is abundant in cruciferous plants and is famous for its excellent anti-cancer effects. With the development of clinical research, more physiological activities of SFN, such as antidepressant, hypoglycemic and anti-inflammatory activities, have been discovered, supporting the fact that SFN and SFN-rich sources have great potential to be dietary supplements that are beneficial to health. This review summarizes the characteristics of intestinal inflammation, the anti-inflammatory mechanism of SFN and its various protective effects on intestinal inflammation, and the possible future applications of SFN for promoting intestinal health have also been discussed.

Carbon dots as nanocatalytic medicine for anti-inflammation therapy

Aberrant reactive oxygen species (ROS) generation is one of the crucial mediators in the pathogenesis of inflammation. So, the development of nanocatalytic medicine to catalyze the ROS-scavenging reactions in pathological regions are promising for anti-inflammatory therapy. Herein, a type of biocompatible metal free carbon dots is prepared via a hydrothermal method which can exhibit peroxidase (POD)-like, catalase (CAT)-like and superoxide dismutase (SOD)-like activities. It has been found that the carbon dots have the capability to efficiently deplete the excessive ROS such as peroxide (H₂O₂)_, superoxide anion (O₂^-) and hydroxyl radical (OH) for their abundant functional groups. After the tail injection in mice with liver inflammation induced by lipopolysaccharide, the carbon dots efficiently reduced the excessive production of ROS and proinflammatory cytokines in vitro. Both in vitro and in vivo results endowed the biocompatible carbon dots with great potential in nanocatalytic medicine for the treatment of disease.

A Novel Cascade Nanoreactor Integrating Two-Dimensional Pd-Ru Nanozyme, Uricase and Red Blood Cell Membrane for Highly Efficient Hyperuricemia Treatment

Nanozyme-based cascade reaction has emerged as an effective strategy for disease treatment because of its high efficiency and low side effects. Herein, a new and highly active two-dimensional Pd-Ru nanozyme is prepared and then integrated with uricase and red blood cell (RBC) membrane to fabricate a tandem nanoreactor, Pd-Ru/Uricase@RBC, for hyperuricemia treatment. The designed Pd-Ru/Uricase@RBC nanoreactor displayed not only good stability against extreme pH, temperature and proteolytic degradation, but also long circulation half-life and excellent safety. The nanoreactor can effectively degrade UA by uricase to allantoin and H₂ O₂ and remove H₂ O₂ by using Pd-Ru nanosheets (NSs) with the catalase (CAT)-like activity. More importantly, the finally produced O₂ from H₂ O₂ decomposition can in turn facilitate the catalytic oxidation of UA, as the degradation of UA is an O₂ consumption process. By integrating the high-efficiency enzymatic activity, long circulation capability, and good biocompatibility, the designed Pd-Ru/Uricase@RBC can effectively and safely treat hyperuricemia without side effects. The study affords a new alternative for the exploration of clinical treatment of hyperuricemia.

Nanozymes Regulate Redox Homeostasis in ROS-Related Inflammation

Reactive oxygen species (ROS), in moderate amounts, play an essential role in regulating different physiological functions in organisms. However, increased amounts of ROS may cause oxidative stress and damage to biomolecules, leading to a variety of diseases including inflammation and even cancer. Therefore, ROS scavenging reagents are needed to maintain healthy levels of ROS. With considerable advances in nanotechnology, nanozymes possess SOD or CAT-like activities with outstanding free radical scavenging activity, facile synthesis conditions, and excellent biocompatibility. Based on these extraordinary properties, nanozymes has been used to modulate the redox homeostasis and relieve the ROS-related injury. This has led to the emergence of nanozyme-based therapies. In the current review, we presented recently developed applications of nanozymes to treat ROS-dependent disorders with an emphasis on inflammatory and brain diseases.

PEGylated Indium Nanoparticles: A Metallic Contrast Agent for Multiwavelength Photoacoustic Imaging and Second Near-Infrared Photothermal Therapy

Indium, a low melting point metal, is well-known for constructing eutectic gallium-indium liquid metal. However, unlike liquid metal nanoparticles, the biomedical applications of metallic indium nanoparticles (In NPs) remain in their infancy. Herein, an ultrasound-assisted liquid-reduction synthesis strategy was developed to prepare PEGylated In NPs, which were then used as a high-performance contrast agent for enhancing multiwavelength photoacoustic imaging and second near-infrared (NIR-II) photothermal therapy of the 4T1 breast tumor. The obtained In NPs depicted remarkable optical absorption from the first near-infrared (NIR-I) to NIR-II region and a high photothermal conversion efficiency of 41.3% at 1064 nm, higher than the majority of conventional NIR-II photothermal agents. Upon injection into the tumor, the photoacoustic intensities of the tumor section post-injection were obviously increased by 2.59-, 2.62-, and 4.27-fold of those of pre-injection by using excitation wavelengths of 750, 808, and 970 nm, respectively, depicting an excellent multiwavelength contrast capability of photoacoustic imaging. In addition, efficient ablation of the 4T1 tumor was achieved through the photothermal performance of PEGylated In NPs under NIR-II laser irradiation. Importantly, as the widely used element in the clinic, In NPs were highly biocompatible in vitro and in vivo. Therefore, this work pioneered the biomedical applications of PEGylated In NPs for cancer diagnosis and treatment.

Prussian blue-based theranostics for ameliorating acute kidney injury

Background

Acute kidney injury (AKI) with high mortality rates is associated with an excess of reactive oxygen/nitrogen species (RONS) within kidney tissues. Recently, nanomedicine antioxidant therapy has been used to alleviate AKI. Herein, we synthesized ultrasmall Prussian blue nanozymes (PB NZs, 4.5 nm) as theranostic agents for magnetic resonance (MR)/photoacoustic (PA) dual-modal imaging guided AKI treatment.

Results

PB NZs exhibited multi-enzyme mimetic abilities, promoting the effective elimination of RONS both in vitro and in vivo. Moreover, benefiting from their imaging contrast properties, the rapid renal accumulation of PB NZs was verified by in vivo PA/MR dual-modal imaging. Due to their excellent enrichment in the kidney and unique multi-enzyme mimetic abilities, ultrasmall PB NZs displayed superior AKI treatment efficacy compared with that of amifostine in two clinically relevant types of AKI induced murine models (either by rhabdomyolysis or cisplatin).

Conclusion

Our findings suggested ultrasmall PB NZs, as nanozyme theranostics, have great potential for AKI management.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01006-z.

Site-Specific Biomimicry of Antioxidative Melanin Formation and Its Application for Acute Liver Injury Therapy and Imaging

Biocompatible nano-antioxidants composed of natural molecules/materials, such as dopamine and melanin, are of great interest for diverse biomedical applications. However, the lack of understanding of the precise structure of these biomaterials and thus the actual dose of effective components impedes their advancement to translation. Herein, a strategy to mimic in situ melanin formation and explore its antioxidative applications is reported, by developing a PEGylated, phenylboronic-acid-protected L-DOPA precursor (PAD) that can self-assemble into well-defined nanoparticles (PADN). Exposure to oxidative species leads to deprotection of phenylboronic acids, transforming PADN to PEG-L-DOPA, which, similar to the biosynthetic pathway of melanin, can be oxidized and polymerized into an antioxidative melanin-like structure. With ultrahigh stability and superior antioxidative activity, the PADN shows remarkable efficacy in prevention and treatment of acute liver injury/failure. Moreover, the in situ structure transformation enables PADN to visualize damaged tissue noninvasively by photoacoustic imaging. Overall, a bioinspired antioxidant with precise structure and site-specific biological activity for theranostics of oxidative stress-related diseases is described.

A Review on Metal- and Metal Oxide-Based Nanozymes: Properties, Mechanisms, and Applications

Since the ferromagnetic (Fe3O4) nanoparticles were firstly reported to exert enzyme-like activity in 2007, extensive research progress in nanozymes has been made with deep investigation of diverse nanozymes and rapid development of related nanotechnologies. As promising alternatives for natural enzymes, nanozymes have broadened the way toward clinical medicine, food safety, environmental monitoring, and chemical production. The past decade has witnessed the rapid development of metal- and metal oxide-based nanozymes owing to their remarkable physicochemical properties in parallel with low cost, high stability, and easy storage. It is widely known that the deep study of catalytic activities and mechanism sheds significant influence on the applications of nanozymes. This review digs into the characteristics and intrinsic properties of metal- and metal oxide-based nanozymes, especially emphasizing their catalytic mechanism and recent applications in biological analysis, relieving inflammation, antibacterial, and cancer therapy. We also conclude the present challenges and provide insights into the future research of nanozymes constituted of metal and metal oxide nanomaterials.

Superoxide dismutase nanozymes: an emerging star for anti-oxidation

Superoxide dismutases (SODs) are a group of metalloenzymes that catalyze the dismutation of superoxide radicals (O2˙-) into hydrogen peroxide (H2O2) and oxygen (O2). As the first line of defense against reactive oxygen species (ROS)-mediated damage, SODs are expected to play an important role in the treatment of oxidative stress-related diseases. However, the clinical applications of SODs have been severely limited by their structural instability and high cost. Compared with natural enzymes, nanozymes, nanomaterials with enzyme-like activity, are more stable, and economical, can be easily modified and their activities can be adjusted. Due to their excellent characteristics, nanozymes have attracted widespread attention in recent years and are expected to become effective substitutes for natural enzymes in many application fields. Importantly, some nanozymes with SOD-like activity have been developed and proved to have a mitigating effect on diseases caused by oxidative stress. These studies on SOD-like nanozymes provide a feasible strategy for breaking through the dilemma of SOD clinical applications. However, at present, the specific catalytic mechanism of SOD-like nanozymes is still unclear, and many important issues need to be resolved. Although there are many comprehensive reviews to introduce the overall situation of the nanozyme field, the research on SOD-like nanozymes still lacks a systematic review. From the structure and mechanism of natural SOD enzymes to the structure and regulation of SOD-like nanozymes, and then to the measurement and application of nanozymes, this review systematically summarizes the recent progress in SOD-like nanozymes. The existing shortcomings and possible future research hotspots in the development of SOD-like nanozymes are summarized and prospected. We hope that this review would provide ideas and inspirations for further research on the catalytic mechanism and rational design of SOD-like nanozymes.

Inorganic nanomaterials with rapid clearance for biomedical applications

Inorganic nanomaterials that have inherently exceptional physicochemical properties (e.g., catalytic, optical, thermal, electrical, or magnetic performance) that can provide desirable functionality (e.g., drug delivery, diagnostics, imaging, or therapy) have considerable potential for application in the field of biomedicine. However, toxicity can be caused by the long-term, non-specific accumulation of these inorganic nanomaterials in healthy tissues, preventing their large-scale clinical utilization. Over the past several decades, the emergence of biodegradable and clearable inorganic nanomaterials has offered the potential to prevent such long-term toxicity. In addition, a comprehensive understanding of the design of such nanomaterials and their metabolic pathways within the body is essential for enabling the expansion of theranostic applications for various diseases and advancing clinical trials. Thus, it is of critical importance to develop biodegradable and clearable inorganic nanomaterials for biomedical applications. This review systematically summarizes the recent progress of biodegradable and clearable inorganic nanomaterials, particularly for application in cancer theranostics and other disease therapies. The future prospects and opportunities in this rapidly growing biomedical field are also discussed. We believe that this timely and comprehensive review will stimulate and guide additional in-depth studies in the area of inorganic nanomedicine, as rapid in vivo clearance and degradation is likely to be a prerequisite for the future clinical translation of inorganic nanomaterials with unique properties and functionality.

Atomic Engineering of Clusterzyme for Relieving Acute Neuroinflammation through Lattice Expansion

Natural enzymes are efficient and versatile biocatalysts but suffer in their environmental tolerance and catalytic stability. As artificial enzymes, nanozymes can improve the catalytic stability, but it is still a challenge to achieve high catalytic activity. Here, we employed atomic engineering to build the artificial enzyme named Au₂₄Ag₁ clusterzyme that hosts an ultrahigh catalytic activity as well as strong physiological stability via atom manipulation. The designed Au₂₄Ag₁ clusterzyme activates the Ag-S active site via lattice expansion in the oligomer atom layer, showing an antioxidant property 72 times higher than that of natural antioxidant Trolox. Enzyme-mimicked studies find that Au₂₄Ag₁ clusterzyme exhibits high catalase-like (CAT-like) and glutathione peroxidase-like (GPx-like) activity with a maximum reaction rate of 68.9 and 17.8 μM/min, respectively. Meanwhile, the unique catalytic landscape exhibits distinctive reactions against inflammation by inhibiting the cytokines at an early stage in the brain. Atomic engineering of clusterzymes provides a powerful and attractive platform with satisfactory atomic dispersion for tailoring biocatalysts freely at the atomic level.

Platinum-Doped Prussian Blue Nanozymes for Multiwavelength Bioimaging Guided Photothermal Therapy of Tumor and Anti-Inflammation

Developing appropriate photothermal agents to meet complex clinical demands is an urgent challenge for photothermal therapy of tumors. Here, platinum-doped Prussian blue (PtPB) nanozymes with tunable spectral absorption, high photothermal conversion efficiency, and good antioxidative catalytic activity are developed by one-step reduction. By controlling the doping ratio, PtPB nanozymes exhibit tunable localized surface plasmon resonance (LSPR) frequency with significantly enhanced photothermal conversion efficiency and allow multiwavelength photoacoustic/infrared thermal imaging guided photothermal therapy. Experimental band gap and density functional theory calculations further reveal that the decrement of free carrier concentrations and increase in circuit paths of electron transitions co-contribute to the enhanced photothermal conversion efficiency of PtPB with tunable LSPR frequency. Benefiting from antioxidative catalytic activity, PtPB can simultaneously relieve inflammation caused by hyperthermia. Moreover, PtPB nanozymes exhibited good biosafety after intravenous injection. Our findings provide a paradigm for designing safe and efficient photothermal agents to treat complex tumor diseases.

Oral delivery of antioxidant enzymes for effective treatment of inflammatory disease

Oral administration of protein is very challenging for therapeutic applications due to its instability and easy degradation in the gastrointestinal tract. Herein, we reported an approach to encapsulate native anti-inflammatory proteins in wind chimes like cyclodextrin (WCC) for efficient oral protein delivery. The amphiphilic WCC can self-assemble into nanoparticles in aqueous solution and achieve superior encapsulation of two antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT) by simply mixing with protein solution, avoiding any extra cumbersome steps that might inactivate protein. WCC nanovehicles can effectively protect enzyme activity and enhance their intracellular delivery. SOD and CAT co-loaded WCC nanoparticles (SC/WCC) can integrate the synergistic effect of SOD and CAT for enhancing the removal of reactive oxygen species (ROS), effectively inhibit the inflammatory response by reducing the secretion of proinflammatory factors and protect cells from ROS-induced oxidative damage. In the mouse colitis model, SC/WCC administered orally was able to efficiently accumulate in the inflamed colon, significantly inhibited the expression of proinflammatory mediators and notably alleviated the symptoms related to colitis. Therefore, we believe that the strategies we described here may provide a convenient and powerful platform for the treatment of other inflammatory diseases.

In vivo guiding inorganic nanozymes for biosensing and therapeutic potential in cancer, inflammation and microbial infections

Researchers have recently introduced some artificial enzymes based on nanomaterials that show significant catalytic activity relative to native enzymes called nanozyme. These nanozymes show superior performance than conventional catalysts and are considered as fascinating candidates for introducing the next generation of biomaterials in various industrial and biomedical fields. Recently, nanozymes have received a great deal of attention in biomedical applications due to their potential properties such as long-term stability, low cost, mass production capability, and controllable catalytic activity. Due to the intrinsic catalytic activity of nanoparticles (NPs) as nanozymes and their ability to be regulated in biomedical processes, this review paper focuses on the in vivo applications of nanozymes in biosensing and therapeutic activities. Despite the challenges and benefits of each approach, this paper attempts to provide an appropriate motivation for the classification of different nanozymes followed by their application in biomedical activities including in vivo biosensing and therapeutic potential in cancer, inflammation and microbial infections. Finally, some ongoing challenges and future perspective of nanozymes in biomedical application were surveyed. In conclusion, this paper may provide useful information regarding the development of nanozymes as promising platforms in biomedical settings due to expedited diagnosis, the advancement of multifactorial therapies and their pronounced stability.

Neutrophil-like Cell-Membrane-Coated Nanozyme Therapy for Ischemic Brain Damage and Long-Term Neurological Functional Recovery

Oxidative stress and a series of excessive inflammatory responses are major obstacles for neurological functional recovery after ischemic stroke. Effective noninvasive anti-inflammatory therapies are urgently needed. However, unsatisfactory therapeutic efficacy of current drugs and inadequate drug delivery to the damaged brain are major problems. Nanozymes with robust anti-inflammatory and antioxidative stress properties possess therapeutic possibility for ischemic stroke. However, insufficiency of nanozyme accumulation in the ischemic brain by noninvasive administration hindered their application. Herein, we report a neutrophil-like cell-membrane-coated mesoporous Prussian blue nanozyme (MPBzyme@NCM) to realize noninvasive active-targeting therapy for ischemic stroke by improving the delivery of a nanozyme to the damaged brain based on the innate connection between inflamed brain microvascular endothelial cells and neutrophils after stroke. The long-term in vivo therapeutic efficacy of MPBzyme@NCM for ischemic stroke was illustrated in detail after being delivered into the damaged brain and uptake by microglia. Moreover, the detailed mechanism of ischemic stroke therapy via MPBzyme@NCM uptake by microglia was further studied, including microglia polarization toward M2, reduced recruitment of neutrophils, decreased apoptosis of neurons, and proliferation of neural stem cells, neuronal precursors, and neurons. This strategy may provide an applicative perspective for nanozyme therapy in brain diseases.

The YTH Domain Family of N6-Methyladenosine "Readers" in the Diagnosis and Prognosis of Colonic Adenocarcinoma

To profile the landscape of methylation N⁶ adenosine (m⁶A) RNA regulators in colonic adenocarcinoma (COAD) and to explore potential diagnostic and prognostic biomarkers, we assessed the differential expression patterns of m⁶A RNA methylation regulators between 418 COAD patients and 41 controls based on profiling from The Cancer Genome Atlas (TCGA) database. We plotted the receiver operating characteristic (ROC) curves and calculated the area under the curve (AUC) values to estimate the discrimination ability. The relationship between the expression of m⁶A RNA methylation regulators and clinicopathological characteristics was explored. Kaplan-Meier plotter, log-rank test, and Cox regression were used and a nomogram was created to explore the prognostic significance of m⁶A-related genes in overall survival at the mRNA level. Pathway analysis was performed by gene set enrichment analysis (GSEA) using TCGA dataset, and a coexpression network was built based on the STRING database. We observed that YTHDF1, METTL3, and KIAA1429 were significantly upregulated, while YTHDF3, YTHDC2, METTL14, and ALKBH5 were significantly downregulated in COAD samples compared to normal samples. YTHDF1 had the highest diagnostic value. Low expression of YTHDF3 predicted a poor survival rate in COAD patients. YTHDC2 was related to sex and showed a downward trend as clinical stage increased. Our results indicate that the YT521-B homology (YTH) domain family (“readers”), especially YTHDF1, YTHDF3, and YTHDC2, might play a significant role in the detection, progression, and prognosis of COAD, indicating that they are promising cancer biomarkers.

Catalytic rhodium (Rh)-based (mesoporous polydopamine) MPDA nanoparticles with enhanced phototherapeutic efficiency for overcoming tumor hypoxia

Rh NPs/Ce6 loaded mesoporous polydopamine (Ce6-Rh@MPDA) nanoparticles were developed to achieve photoacoustic/fluorescence imaging-guided photothermal and photodynamic therapy to eliminate tumors and improve hypoxia in tumor microenvironments.