3D printing of conch-like scaffolds for guiding cell migration and directional bone growth

Regeneration of severe bone defects remains an enormous challenge in clinic.Developing regenerative scaffolds to directionally guide bone growth is a potential strategy to overcome this hurdle.Conch,an interesting creature widely spreading in ocean,has tough spiral shell that can continuously grow along the spiral direction.Herein,inspired by the physiological features of conches,a conch-like(CL)scaffold based onβ-TCP bioceramic material was successfully prepared for guiding directional bone growth via digital light processing(DLP)-based 3D printing.Benefiting from the spiral structure,the CL scaffolds significantly improved cell adhesion,proliferation and osteogenic differentiation in vitro compared to the conventional 3D scaffolds.Particularly,the spiral structure in the scaffolds could efficiently induce cells to migrate from the bottom to the top of the scaffolds,which was like“cells climbing stairs”.Furthermore,the capability of guiding directional bone growth for the CL scaffolds was demonstrated by a special half-embedded femoral defects model in rabbits.The new bone tissue could consecutively grow into the protruded part of the scaffolds along the spiral cavities.This work provides a promising strategy to construct biomimetic biomaterials for guiding directional bone tissue growth,which offers a new treatment concept for severe bone defects,and even limb regeneration.

Nano-calcium silicate mineralized fish scale scaffolds for enhancing tendon-bone healing

Tendon-bone healing is essential for an effective rotator cuff tendon repair surgery,however,this remains a significant challenge due to the lack of biomaterials with high strength and bioactivity.Inspired by the high-performance exoskeleton of natural organisms,we set out to apply natural fish scale(FS)modified by calcium silicate nanoparticles(CS NPs)as a new biomaterial(CS-FS)to overcome the challenge.Benefit from its“Bouligand”microstructure,such FS-based scaffold maintained excellent tensile strength(125.05 MPa)and toughness(14.16 MJ/m^(3)),which are 1.93 and 2.72 times that of natural tendon respectively,allowing it to well meet the requirements for rotator cuff tendon repair.Additionally,CS-FS showed diverse bioactivities by stimulating the differentiation and phenotypic maintenance of multiple types of cells participated into the composition of tendon-bone junction,(e.g.bone marrow mesenchymal stem cells(BMSCs),chondrocyte,and tendon stem/progenitor cells(TSPCs)).In both rat and rabbit rotator cuff tear(RCT)models,CS-FS played a key role in the tendon-bone interface regeneration and biomechanical function,which may be achieved by activating BMP-2/Smad/Runx2 pathway in BMSCs.Therefore,natural fish scale-based biomaterials are the promising candidate for clinical tendon repair due to their outstanding strength and bioactivity.

Organosilicon polymer-derived ceramics: An overview

Polymer-derived ceramics(PDCs) strategy shows a great deal of advantages for the fabrication of advanced ceramics. Organosilicon polymers facilitate the shaping process and different silicon-based ceramics with controllable components can be fabricated by modifying organosilicon polymers or adding fillers. It is worth noting that silicate ceramics can also be fabricated from organosilicon polymers by the introduction of active fillers, which could react with the produced silica during pyrolysis. The organosilicon polymer-derived ceramics show many unique properties, which have attracted many attentions in various fields. This review summarizes the typical organosilicon polymers and the processing of organosilicon polymers to fabricate silicon-based ceramics, especially highlights the three-dimensional(3 D) printing technique for shaping the organosilicon polymerderived ceramics, which makes the possibility to fabricate silicon-based ceramics with complex structure. More importantly, the recent studies on fabricating typical non-oxide and silicate ceramics derived from organosilicon polymers and their biomedical applications are highlighted.

Bioceramic-based scaffolds with antibacterial function for bone tissue engineering:A review

Bone defects caused by trauma,tumor,congenital abnormality and osteoarthritis,etc.have been substantially impacted the lives and health of human.Artificial bone implants,like bioceramic-based scaffolds,provide significant benefits over biological counterparts and are critical for bone repair and regeneration.However,it is highly probable that bacterial infections occur in the surgical procedures or on bioceramic-based scaffolds.Therefore,it is of great significance to obtain bioceramic-based scaffolds with integrative antibacterial and osteogenic functions for treating bone implant-associated infection and promoting bone repair.To fight against infection problems,bioceramic-based scaffolds with various antibacterial strategies are developed for bone repair and regeneration and also have made great progresses.This review summarizes recent progresses in bioceramic-based scaffolds with antibacterial function,which include drug-induced,ion-mediated,physical-activated and their combined antibacterial strategies according to specific antibacterial mechanism.Finally,the challenges and opportunities of antibacterial bioceramic-based scaffolds are discussed.

Forsterite-hydroxyapatite composite scaffolds with photothermal antibacterial activity for bone repair

Bone engineering scaffolds with antibacterial activity satisfy the repair of bacterial infected bone defects,which is an expected issue in clinical.In this work,3D-printed polymer-derived forsterite scaffolds were proposed to be deposited with hydroxyapatite(HA)coating via a hydrothermal treatment,achieving the functions of photothermal-induced antibacterial ability and bioactivity.The results showed that polymer-derived forsterite scaffolds possessed the photothermal antibacterial ability to inhibit Staphylococcus aureus(S.aureus)and Escherichia coli(E.coli)in vitro,owing to the photothermal effect of free carbon embedded in the scaffolds.The morphology of HA coating on forsterite scaffolds could be controlled through changing the hydrothermal temperature and the pH value of the reaction solution during hydrothermal treatment.Furthermore,HA coating did not influence the mechanical strength and photothermal effect of the scaffolds,but facilitated the proliferation and osteogenic differentiation of rat bone mesenchymal stem cells(rBMSCs)on scaffolds.Hence,the HA-deposited forsterite scaffolds would be greatly promising for repairing bacterial infected bone defects.

Manganese-Doped Calcium Silicate Nanowire Composite Hydrogels for Melanoma Treatment and Wound Healing

Melanoma is a serious malignant skin tumor.Effectively eliminating melanoma and healing after-surgical wounds are always challenges in clinical studies.To address these problems,we propose manganese-doped calcium silicate nanowire-incorporated alginate hydrogels(named MCSA hydrogels)for in situ photothermal ablation of melanoma followed by the wound healing process.The proposed MCSA hydrogel had controllable gelation properties,reasonable strength,and excellent bioactivity due to the incorporated calcium silicate nanowires as the in situ cross-linking agents and bioactive components.The doping of manganese into calcium silicate nanowires gave them excellent photothermal effects for eradicating melanoma effectively under near infrared(NIR)irradiation.Moreover,the synergistic effect of manganese and silicon in the MCSA hydrogel effectively promotes migration and proliferation of vascular endothelial cells and promotes angiogenesis.Hence,such bifunctional bioactive hydrogels could achieve combined functions of photothermal therapy and wound healing,showing great promise for melanoma therapy and tissue regeneration.

Manganese silicate nanospheres-incorporated hydrogels:starvation therapy and tissue regeneration

To prevent postoperative skin tumor recurrence and repair skin wound,a glucose oxidase(GOx)-loaded manganese silicate hollow nanospheres(MS HNSs)-incorporated alginate hydrogel(G/MS-SA)was constructed for starvation-photothermal therapy and skin tissue regeneration.The MS HNSs showed a photothermal conversion efficiency of 38.5%,and endowed composite hydrogels with satisfactory photothermal effect.Taking advantage of the catalytic activity of Mn ions,the composite hydrogels could decompose hydrogen peroxide(H2O2)into oxygen(O2),which can alleviate the problem of tumor hypoxia microenvironment and endow GOx with an ability to consume glucose in the presence of O2 for tumor starvation.Meanwhile,hyperthermia triggered by near infrared(NIR)irradiation could not only accelerate the reaction rate of H2O2 decomposition by MS HNSs and glucose consumption by GOx,but also ablate tumor cells.The anti-tumor results showed that synergistic effect of starvation-photothermal therapy led to the highest death rate of tumor cells among all groups,and its anti-tumor effect was obviously improved as compared with that of single photothermal treatment or starvation treatment.Interestingly,the introduction of MS HNSs into hydrogels could distinctly promote the epithelialization of the wound beds by releasing Mn ions as compared with the hydrogels without MS HNSs.It is expected that such a multifunctional platform with starvation-photothermal therapy will be promising for treating tumor-caused skin defects in combination of its regeneration bioactivity in the future.

Spin engineering of single-site metal catalysts

Single-site metal atoms(SMAs)on supports are attracting extensive interest as new catalytic systems because of maximized atom utilization and superior performance.However,rational design of configuration-optimized SMAs with high activity from the perspectives of fundamental electron spin is highly challenging.Herein,N-coordinated Fe single atoms are successfully distributed over axial carbon micropores to form dangling-FeN4 centers(d-FeN4).This unique d-FeN4 demonstrates much higher intrinsic activity toward oxygen reduction reaction(ORR)in HClO4 than FeN4 without micropore underneath and commercial Pt/C.Both theoretical calculation and electronic structure characterization imply that d-FeN4 endows central Fe with medium spin(t2g 4 eg 1),which provides a spin channel for electron transition compared with FeN4 with low spin.This leads to the facile formation of the singlet state of oxygen-containing species from triplet oxygen during the ORR,thus showing faster kinetics than FeN4.This work provides an in-depth understanding of spin tuning on SMAs for advanced energy catalysis.

SARS-CoV-2 immunity and functional recovery of COVID-19 patients 1-year after infection

The long-term immunity and functional recovery after SARS-CoV-2 infection have implications in preventive measures and patient quality of life.Here we analyzed a prospective cohort of 121 recovered COVID-19 patients from Xiangyang,China at 1-year after diagnosis.Among them,chemiluminescence immunoassay-based screening showed 99%(95%CI,98–100%)seroprevalence 10–12 months after infection,comparing to 0.8%(95%CI,0.7–0.9%)in the general population.Total anti-receptor-binding domain(RBD)antibodies remained stable since discharge,while anti-RBD IgG and neutralization levels decreased over time.A predictive model estimates 17%(95%CI,11–24%)and 87%(95%CI,80–92%)participants were still 50%protected against detectable and severe re-infection of WT SARS-CoV-2,respectively,while neutralization levels against B.1.1.7 and B.1.351 variants were significantly reduced.All non-severe patients showed normal chest CT and 21%reported COVID-19-related symptoms.In contrast,53%severe patients had abnormal chest CT,decreased pulmonary function or cardiac involvement and 79%were still symptomatic.Our findings suggest long-lasting immune protection after SARS-CoV-2 infection,while also highlight the risk of immune evasive variants and long-term consequences for COVID-19 survivors.