Enhancing osteogenic bioactivities of coaxial electrospinning nanoscaffolds through incorporating iron oxide nanoparticles and icaritin for bone regeneration

Bone tissue engineering provides a promising strategy for the treatment of bone defects.Nonetheless,the clinical utilization of biomaterial-based scaffolds is constrained by their inadequate mechanical strength and absence of osteo-inductive properties.Here,we proposed to endow nano-scaffold(NS)constructed by coaxial electrospinning technique with enhanced osteogenic bioactivities and mechanical properties by incorporating biocompatible magnetic iron oxide nanoparticles(IONPs)and icaritin(ICA).Four types of nano-scaffolds(NS,ICA@NS,NS-IONPs and ICA@NS-IONPs)were prepared.The incorporation of ICA and IONPs minimally impact their surface morphological and chemical properties.IONPs enhanced the mechanical properties of NS scaffolds,including hardness,tensile strength,and elastic modulus.In vitro assessments demonstrated that ICA@NS-IONPs exhibited enhanced osteogenic bioactivities towards mouse calvarial pre-osteoblast cell line MC3T3-E1 as evidenced by detecting the alkaline phosphatase(ALP)activity level,expressions of osteogenesis-related genes and proteins as well as mineralized nodule formation.Mechanistic investigations revealed that MEK/ERK(MAP kinase-ERK kinase(MEK)/extracellularsignal-regulated kinase(ERK))signaling pathway could offer a plausible explanation for the osteogenic differentiation of MC3T3-E1 cells induced by ICA@NS-IONPs.Furthermore,the implantation of nano-scaffolds in rat skull defects exhibited a substantial improvement in in vivo bone regeneration.Therefore,IONPs and ICA incorporated coaxial electrospinning nano-scaffolds present a novel strategy for the optimization of scaffolds for bone tissue engineering.

Interface Hydrogen-bonded Core-Shell Nanofibers by Coaxial Electrospinning

Core-shell nanofibers were prepared by coaxial electrospinning technology,with poly（ethylene oxide）（PEO） as the core while poly（acrylic acid）（PAA） as the shell.PEO and PAA can form polymer complexes based on hydrogen bonding.In order to avoid forming strong hydrogen bonding complexes at nozzle and blocking spinning process,a polar aprotic solvent,N,N-dimethylformamide（DMF）,was selected to dissolve PEO and PAA respectively.SEM,TEM and DSC were utilized to characterize the morphology and structure of PEO-PAA core-shell nanofibers.FTIR spectra demonstrated that hydrogen bonding was formed at the core-shell interface.In addition,the PAA shell of the nanofibers can be cross-linked by ethylene glycol（EG） under heat treatment,which increases the stability and extends the potential applications in aqueous environment.

Surface Functionalization of PEO Nanofibers Using a TiO_(2) Suspension as Sheath Fluid in a Modified Coaxial Electrospinning Process

Convenient and integration fabrication process is a key issue for the application of functional nanofibers.A surface functionalization method was developed based on coaxial electrospinning to produce ultraviolet(UV)protection nanofibers.The titanium dioxide(TiO_(2))nanoparticles suspension was delivered through the shell channel of the coaxial spinneret,by which the aggregation of TiO_(2) nanoparticles was overcome and the distribution uniformity on the surface of polyethylene oxide(PEO)nanofiber was obtained.With the content of TiO_(2) increasing from 0 to 3%(mass fraction),the average diameter of nanofibers increased from(380±30)nm to(480±100)nm.The surface functionalization can be realized during the electrospinning process to gain PEO/TiO_(2) composite nanofibers directly.The uniform distribution of TiO_(2) nanoparticles on the surface of nanofibers enhanced the UV absorption and resistance performance.The maximum UV protection factor(UPF)value of composite nanofibers reaches 2751.This work presented a novel surface-functionalized way for the preparation of composite nanofiber,which has great application potential in the field of micro/nano system integration fabrication.

The multifunctional wound dressing with core-shell structured fibers prepared by coaxial electrospinning

The non-woven wound dressing with core-shell structured fibers was prepared by coaxial electrospinning. The polycaprolactone （PCL） was electrospun as the fiber＇s core to provide mechanical strength whereas collagen was fabricated into the shell in order to utilize its good biocompatibility. Simultaneously, the silver nanoparticles （Ag- NPs） as anti-bacterial agent were loaded in the shell whereas the vitamin A palmitate （VA） as healing-promoting drug was encapsulated in the core. Resulting from the fiber＇s core- shell structure, the VA released from the core and Ag-NPs present in the shell can endow the dressing both heal-promoting and anti-bacteria ability simultaneously, which can greatly enhance the dressing＇s clinical therapeutic effect. The dressing can maintain high swelling ratio of 190% for 3 d indicating its potential application as wet dressing. Furthermore, the dressing＇s anti-bacteria ability against Staphylococcus aureus was proved by in vitro anti-bacteria test. The in vitro drug release test showed the sustainable release of VA within 72 h, while the cell attachment showed L929 cells can well attach on the dressing indicating its good biocompatibility. In conclusion, the fabricated nanofibrous dressing possesses multiple functions to benefit wound healing and shows promising potential for clinical application.

Flexible,Highly Thermally Conductive and Electrically Insulating Phase Change Materials for Advanced Thermal Management of 5G Base Stations and Thermoelectric Generators

Thermal management has become a crucial problem for high-power-density equipment and devices.Phase change materials(PCMs)have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition.However,low intrinsic thermal conductivity,ease of leakage,and lack of flexibility severely limit their applications.Solving one of these problems often comes at the expense of other performance of the PCMs.In this work,we report core–sheath structured phase change nanocomposites(PCNs)with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning,electrostatic spraying,and hot-pressing.The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m^(-1)K^(-1)at a low BNNS loading(i.e.,32 wt%),which thereby endows the PCNs with high enthalpy(>101 J g^(-1)),outstanding ductility(>40%)and improved fire retardancy.Therefore,our core–sheath strategies successfully balance the trade-off between thermal conductivity,flexibility,and phase change enthalpy of PCMs.Further,the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators,displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.

A core–shell amidoxime electrospun nanofiber affinity membrane for rapid recovery Au(Ⅲ) from water

An affinity membrane was prepared by coaxial electrospinning and amidoxime(AONFA),and it was applied to selectively recovery Au(Ⅲ)from an aqueous solution.The static adsorption results showed that,when p H at 5,the maximum adsorption capacity of AONFA membrane for Au(Ⅲ)was 509.3 mg·g^(-1).AONFA membrane exhibit much higher affinity and selectivity towards Au(Ⅲ)than other metal cations.The membrane could be regenerated effectively by mixture solution of thiourea and HCl,and the desorption ratio reached almost 100%after 4 hours desorption.The dead-end filtration results showed that,the membrane utilization efficiency and adsorption capacity can be improved by increasing the flow rate,while increasing the concentration shorted the breakthrough process and had little impact to adsorption capacity.We can flexibly adjust the flow rate and concentration according to the situation to obtain the maximum utilization efficiency of the membrane in filtration process.The dynamic adsorption capacity is higher than the static adsorption capacity.The adsorption mechanism for Au(Ⅲ)is electrostatic adsorption and reduction.Thus,AONFA membrane filtration was demonstrated to be a promising method for continuous recover Au(Ⅲ)from wastewater.

Electroactive and antibacterial wound dressings based on Ti_(3)C_(2)T_(x)MXene/poly(ε-caprolactone)/gelatin coaxial electrospun nanofibrous membranes

Endogenous electric fields(EFs)are capable of regulating the behaviors of skin cells in wound healing.However,majority of current dressings are primarily engaged in the passive repair of defective tissue,as they lack the ability to actively respond to physiological electrical signals.In this work,a series of nanofibrous membranes(NFMs)were fabricated by coaxial electrospinning,combining the good mechanical properties of poly(ε-caprolactone)(PCL),the bioactivity of gelatin and the electroactivity of Ti_(3)C_(2)T_(x)MXene,as electroactive and antibacterial dressings for cutaneous wound healing.The obtained NFMs exhibited suitable mechanical properties and hydrophilicity,excellent electroactivity,antibacterial activity,and biocompatibility.Especially,Ti_(3)C_(2)T_(x)MXene/PCL/gelatin-6(MPG-6,6 wt.%of Ti_(3)C_(2)T_(x)MXene in sheath spinning liquids)showed the optimal conductivity and antibacterial activity.Excitingly,this scaffold significantly promoted the adhesion,proliferation,and migration of NIH 3T3 cells under the electrical stimulation(ES).The in vivo evaluation in a full-thickness wounds defect model demonstrated that the MPG-6 films significantly accelerated wound closure,increased granulation tissue formation,increased collagen deposition,and promoted wound vascularization.In summary,the versatile scaffold is expected to be an ideal candidate as wound dressings due to its ability to promote the transmission of physiological electrical signals and thus improved the therapeutic outcomes of wound regeneration.

Construction of PMIA@PAN/PVDF-HFP/TiO_(2) coaxial fibrous separator with enhanced mechanical strength and electrolyte affinity for lithium-ion batteries

Poly(m-phthaloyl-m-phenylenediamine)(PMIA)is promising as the separator in lithium-ion batteries(LIBs)for its excellent thermostability,insulation and self-extinguishing properties.However,its low mechanical strength and poor electrolyte affinity limit its application in LIBs.In this work,a new PMIA@polyacrylonitrile-polyvinylidene fluoride hexafluoropropylene-titanium dioxide(PMIA@PAN/PVDFHFP/TiO_(2))composite fibrous separator with a coaxial core-shell structure was developed by combining coaxial electrospinning,hot pressing,and heat treatment techniques.This separator not only inherits the exceptional thermostability of PMIA,showing no evident thermal shrinkage at 220 ℃,but also reveals improved mechanical strength(29.7 MPa)due to the formation of firm connections between fibers with the melted PVDF-HFP.Meanwhile,the massive polar groups in PVDF-HFP play a vital role in improving the electrolyte affinity,which renders the separator a high ionic conductivity of 1.36×10^(-3)s/cm.Therefore,the LIBs with PMIA@PAN/PVDF-HFP/TiO_(2)separators exhibited excellent cycling and rate performance at 25℃,and a high capacity retention rate(76.2%)at 80℃for 200 cycles at 1 C.Besides,the lithium metal symmetric battery assembled by the separator showed a small overpotential,indicating that the separator had a role in inhibiting lithium dendrites.In short,the PMIA@PAN/PVDF-HFP/TiO_(2) separator possesses a wide application prospect in the domain of LIBs.

Multistimuli Responsive and Thermoregulated Capability of Coaxial Electrospun Membranes with Core-sheath Structure and Functional Polypyrrole Layer

Developing thermal management fabrics with good energy storage and multistimuli responsive properties is important for regulating the body temperature in complex environment.Herein,the intelligent nonwoven membranes were fabricated via a coaxial electrospinning method,resulting in a core-sheath structure with poly(ethylene glycol)(PEG)as core and polyurethane(PU)as sheath.Additionally,polypyrrole(PPy)with good light absorption ability and electrical conductivity was deposited onto the surface of the PU@PEG electrospun fibers via electrochemical polymerization.The PPy layer enabled the membranes to respond quickly to sunlight and electrical stimuli.The membranes could heat up to 86°C under simulated sunlight within 200 s or produce remarkable electrothermal effect under a low voltage input of only 1V,exhibiting efficient energy conversion and storage performances.The photothermal and electrothermal conversion effect could be easily adjusted by controlling the polymerization time of PPy.Therefore,the multifunctional membranes with high latent heat,good mechanical properties as well as excellent photothermal/electrothermal conversion ability are promising in personal thermal management applications.

Electrospun Core-Shell Fibrous 2D Scaffold with Biocompatible Poly(Glycerol Sebacate) and Poly-l-Lactic Acid for Wound Healing

Biomimetic scaffolds made by synthetic materials are usually used to replace the natural tissues aimed at speeding up the skin regeneration.In this study,a flexible and cytocompatible poly(glycerol sebacate)@poly-l-lactic acid(PGS@PLLA)fibrous scaffold with a core-shell structure was fabricated by coaxial electrospinning,where the shell PLLA was used to be a skeleton with pores on the fibrous surface.The fibrous morphology with pores on the surface of the prepared fibers was observed by SEM.The core-shell microstructure of PGS@PLLA fibers was confirmed by TEM and Laser Scanning Confocal Microscopy(LSCM).In addition,the prepared fibers exhibited a strong ability to repair tissues of the skin wound,where the stability of cell security and proliferation,and the lower inflammatory response were all superior to those of pure PLLA scaffold.It’s worth noting that the percentage of skin tissue was regenerated by 95%within 14 days,which suggests the potential application for electrospun-based synthetic fibrous scaffolds on wound healing.

Luminescence of EPDM rubber ultrafine fibers containing nanodispersed Eu-complexes

Polyvinylpyrrolidone/ethylene-propylene-diene terpolymer （PVP/EPDM） sheath/core fibers, with the incorporation of Eu（TTA）3Phen （TTA=2-thenoyltrifluoroacetone, Phen=1,10-phenanthroline） complex （Eu-complex） in EPDM, were prepared by coaxial electrospinning. The composite fibers were further vulcanized by peroxide. Scanning electron microscopy （SEM） observations showed that the composite fi- bers had an average diameter of about 200 nm and a smooth surface. The dispersion of Eu-complexes in the fibers was characterized by transmission electron microscopy （TEM）, energy-dispersive X-ray spectroscopy （EDS）, and X-ray diffraction （XRD）. The studies revealed that the Eu-complex was dispersed in the EPDM fibers in the form of molecular clusters and/or nanoparticles with a diameter smaller than 10 nm. Fluorescence spectra and Judd-Ofelt parameters analysis showed that the luminescent quantum efficiency of the composite fibers was greatly improved when the Eu-complex content was 15 wt.%, because the fine dispersion of Eu-complex in EPDM facilitated the increase of radiative transition rate of the composite fibers over that of the neat complex powder.

Decellularized Extracellular Matrix Containing Electrospun Fibers for Nerve Regeneration:A Comparison Between Core–Shell Structured and Preblended Composites

Advanced biomaterial-based strategies for treatment of peripheral nerve injury require precise control over both topological and biological cues for facilitating rapid and directed nerve regeneration.As a highly bioactive and tissue-specifc natural material,decellularized extracellular matrix(dECM)derived from peripheral nerves(decellularized nerve matrix,DNM)has drawn increasing attention in the feld of regenerative medicine,due to its outstanding capabilities in facilitating neurite outgrowth and remyelination.To induce and maintain sufcient topological guidance,electrospinning was conducted for fabrication of axially aligned nanofbers consisting of DNM and poly(ε-caprolactone)(PCL).Core–shell structured fbers were prepared by coaxial electrospinning using DNM as the shell and PCL as the core.Compared to the aligned electrospun fbers using preblended DNM/PCL,the core–shell structured fbers exhibited lower tensile strength,faster degradation,but considerable toughness for nerve guidance conduit preparation and relatively intact fbrous structure after long-term degradation.More importantly,the full DNM surface coverage of the aligned core–shell fbers efectively promoted axonal extension and Schwann cells migration.The DNM contents further triggered neurite bundling and myelin formation toward nerve fber maturation and functionalization.Herein,we not only pursue a multi-functional scafold design for nerve regeneration,a detailed comparison between core–shell structured and preblended electrospinning of DNM/PCL composites was also provided as an applicable paradigm for advanced tissue-engineered strategies using dECM-based biomaterials.

Engineered Spindles of Little Molecules Around Electrospun Nanofbers for Biphasic Drug Release

Biphasic drug release is a popular advanced drug controlled release profle that has been drawing increasing attention from many felds.Electrospun nanofbers and their derivatives can be act as a strong platform for developing biphasic release dosage forms.In this study,a modifed coaxial electrospinning was implemented,in which little molecule solutions that contain a drug ibuprofen(IBU)and polyethylene glycol(PEG)were exploited as a sheath fuid to surround the core solutions composed of polymer ethyl cellulose(EC)and IBU.The prepared nanofber-based structural hybrids,i.e.,engineered spindles-on-astring(SOS)products,were successfully created and subjected to a series of characterizations.Scanning electron microscopy and transmission electron microscopy results showed the engineered SOS structures.IBU and the carriers EC and PEG had good compatibility,as suggested by X-ray difraction and Fourier transform infrared spectroscopy assessments.In vitro dissolution tests verifed that the SOS products were able to provide a typical biphasic release profle,releasing 40%of the loaded IBU within 1 h in an immediate manner in the frst phase,and the rest of the IBU in a sustained manner in the second phase.A combined mechanism of erosion and difusion is proposed for manipulating the IBU molecule release behaviors.

A novel core-shell rifampicin/isoniazid electrospun nanofiber membrane for long time drug dissolution

Rifampicin(RIF)and isoniazid(INH)are commonly applied jointly in clinical to improve the treatment efficacy of tuberculosis.Due to the metabolism of the kidneys,most of RIF and INH would be excreted by human bodies after reaching a high drug concentration,which causes serious waste of drugs and does harm to our health.In this study,polylactic acid(PLLA)was chosen as the carrier to prepare core-shell drug-loaded nanofibers with RIF in the shell and INH in the core by coaxial electrospinning.The results showed that the average diameter of the core-shell drug-loaded fibers with an obvious core-shell structure was about 650 nm.Parts of RIF and INH in the fibers became amorphous;the rest maintained crystalline.The combination of PLLA and RIF made the fibers obvious hydrophobic and exhibited a slowly phased sustained-dissolve property during in vitro dissolution studies.The in vitro antibacterial experiments confirmed that the core-shell drug-loaded nanofibers had a favorite inhibitory effect on Staphylococcus aureus,which endowed practical medical value to the fibers.The core-shell drug-loaded nanofibers effectively separated RIF and INH,preventing the degradation of RIF caused by the direct contact of the two drugs.The slow-dissolve characteristics can maintain a relatively stable drug concentration and avoid the damage to the human body caused by the quick dissolve and rapid metabolism of drugs.The combination with coaxial electrospinning fills the gap in the core-shell system with two drugs and has great significance in the future.