The fabrication of multifunctional sodium alginate scaffold incorporating ibuprofen-loaded modified PLLA microspheres based on cryogenic 3D printing.

A strategy to develop a multifunctional sodium alginate personalized scaffold with enhanced mechanical stability, osteogenesis activity and excellent anti-inflammatory activity by cryogenic 3 D printing combined with subsequent crosslinking with Sr2+ is proposed in this study. The ink for 3 D printing was prepared by dispersing modified PLLA droplets containing ibuprofen into sodium alginate aqueous solution using lecithin as stabilizer. The results showed that the drug-loaded microspheres formed from the low-temperature solidifying of the modified PLLA droplets were homogeneously dispersed in sodium alginate substrate, and the scaffold displayed a sustained drug release performance toward ibuprofen which endowed the scaffold with persistent anti-inflammatory effects. In vitro cell culture indicated that the lecithin not only acted as the stabilizer, but also stimulated the proliferation and mineralization of osteoblastic cells on the scaffold. Sr2+-crosslinking improved the mechanical properties and osteogenic activity of the scaffold.

Cryogenic 3D printing of modified polylactic acid scaffolds with biomimetic nanofibrous architecture for bone tissue engineering.

The individualized polylactic acid (PLA) scaffolds fabricated by 3D printing technique have a good application prospect in the bone tissue engineering field. However, 3D printed PLA scaffold mainly manufactured by using a Fused Deposition Modelling fabrication technique (FDM) has some disadvantages, such as having smooth surface, strong hydrophobicity, poor cell adhesion, undesirable bioactivity, the degradation and deterioration at a high temperature triggering an inflammatory response. In this work, the aminated modified polylactic acid nanofibrous scaffold prepared by cryogenic 3D printing technology is designed to provide a feasible countermeasure to solve the key problems existing at present. The prepared scaffolds were fully characterized in terms of physico-chemical and morphological analyses, and the collected results revealed that the using of the cryogenic 3D printing technology can effectively avoid the degradation and deterioration of PLA at a high temperature required by FDM technique and promote the formation of nanofibrous structures. The in vitro tests with MC3T3-E1 cells confirmed that the cell-responsive biomimetic fibrous architecture and improved hydrophilicity due to the introduction of hydrophilic active amino groups provided a bioactive interface for cell adhesion and growth. Meanwhile, the active amino groups introduced by ammonolysis reaction can act as active sites for biomineralization. Thus, the as-prepared scaffolds may hold great potential for bone tissue engineering applications.

Multifunctional modified polylactic acid nanofibrous scaffold incorporating sodium alginate microspheres decorated with strontium and black phosphorus for bone tissue engineering.

Polylactic acid (PLA) nanofibrous scaffolds have received extensive attention in the field of tissue engineering due to their excellent degradability, biocompatibility and the biomimetic extracellular matrix (ECM) topographies. However, the cell affinity and osteogenic activity of PLA scaffolds is not satisfactory because of their intrinsic hydrophobicity, the absence of cell recognition sites and the nucleation sites of the in vivo biomineralization. Furthermore, effective anti-inflammatory activity for the in vivo scaffold could not be ignored, so a strategy to develop a multifunctional PLLA (poly-L-lactic acid) nanofibrous scaffold with improved hydrophilicity, osteoinductivity, excellent near-infrared photothermal-responsive drug release capacity and anti-inflammatory activity via incorporating sodium alginate microspheres decorated with strontium and ibuprofen-loaded black phosphorus (BP + IBU@SA microspheres) into aminated modified PLLA nanofiber network is proposed in this study. Scanning electron microscopy (SEM) observation showed that the BP + IBU@SA microspheres were homogeneously dispersed into the modified PLLA matrix with uniform nanofiber structure and the chemical composition of the as-prepared scaffolds was confirmed by X-ray diffraction analysis (XRD) and elemental mapping. The photothermal property of the scaffolds was assessed under near-infrared (NIR) light irradiation, the results manifested that the entrapment of BP nanosheets endowed PLLA nanofibrous scaffold with significantly high photothermal conversion efficiency and optical cycle stability. Meanwhile, the scaffold also displayed an excellent photothermal-responsive intelligent drug release performance toward Sr2+ and ibuprofen. Moreover, the in vitro studies revealed that the as-developed scaffolds possessed a good biocompatibility for cell adhesion and proliferation and an improved bioactivity to induce apatite formation. All these results indicated the potential of the fabricated scaffolds in tissue engineering applications.

Biomimetic mineralization of nanocrystalline hydroxyapatites on aminated modified polylactic acid microspheres to develop a novel drug delivery system for alendronate.

EPLA/nHAp composite microsphere, a novel drug delivery system potentially useful for the local delivery of alendronate (AL) to bone tissue was developed via the biomimetic mineralized deposition of nano-hydroxyapatite (nHAp) crystals on the surface of aminated modified polylactic acid (EPLA) microspheres. Scanning electron microscopy (SEM) observation showed that this system consisted of a polymer core with nanofiber network structure and inorganic coating composed of countless rod-like nanocrystalline particles, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis (XRD) confirmed that these particles were nHAp crystals. An efficient AL-loading can be realized by facile impregnation-adsorption method under suitable conditions due to the high adsorption capacity of EPLA/nHAp composite microspheres. The drug loading efficiency of microspheres was detected by indirect ultraviolet spectrophotometry. It was found that the adsorption capacity of EPLA/nHAp composite microsphere towards AL was increased nearly 5-fold compared with that of bare EPLA microspheres owing to the strong interaction between alendronate and hydroxyapatite. Meanwhile, in vitro release study showed that AL-loaded EPLA/nHAp microspheres had a more sustained drug release than AL-loaded EPLA microspheres, all these results demonstrated that the as-prepared EPLA/nHAp composite microsphere is an efficient carrier for the delivery and sustained release of AL. Furthermore, an in vitro cell culture study revealed that these composite microspheres presented a good biocompatibility, showing great potential for the applications in the biomedical field.

Cobalt Nanoparticles/Black Phosphorus Nanosheets: An Efficient Catalyst for Electrochemical Oxygen Evolution.

Black phosphorus (BP) nanosheet (NS) is an emerging oxygen evolution reaction (OER) electrocatalyst with both high conductivity and abundant active sites. However, its ultrathin structure suffers instability because of the lone pair electrons exposed at the surface, which badly restricts durability for achieving long-term OER catalysis. Herein, a facile solvothermal reduction route is designed to fabricate Co/BP NSs hybrid electrocatalyst by in situ growth of cobalt nanoparticles on BP NSs. Notably, electronic structure engineering of Co/BP NSs catalyst is observed by electron migration from BP to Co due to the higher Fermi level of BP than that of Co. Because of the preferential migration of the active lone pairs from the defect of BP NSs, the stability and high hole mobility can be effectively retained. Consequently, Co/BP NSs electrocatalyst exhibits outstanding OER performance, with an overpotential of 310 mV at 10 mA cm-2, and excellent stability in alkaline media, indicating the potential for the alternatives of commercial IrO2. This study provides insightful understanding into engineering electronic structure of BP NSs by fully utilizing defect and provides a new idea to design hybrid electrocatalysts.

Phase-Controlled Synthesis of High-Bi-Ratio Ternary Sulfide Nanocrystals of Cu1.57 Bi4.57 S8 and Cu2.93 Bi4.89 S9.

High Bi-ratio ternary sulfides have been recently reported as superior thermoelectric materials. However, the synthesis of high Bi-ratio Cu-Bi-S nanocrystal remains a challenge. Reported here are the synthesis and characterization of three-phase Cu-Bi-S nanocrystals with the nominal chemical formulae of Cu1.57 Bi4.57 S8 , Cu2.93 Bi4.89 S9 and Cu3 BiS3 . The samples were prepared using a Bi2 S3 precursor by varying the amount and type of Cu2-x S (i. e. Cu2 S or Cu7.2 S4 ) reactants. TEM images reveal that two new samples crystalized having nanorod morphology with radii of approximately 50 nm and lengths of 200 nm. XPS results indicate that the valence states of Bi in both the two new phases are +3 with viable oxidation states for Cu. UV-Vis-NIR absorption spectroscopy reveals that narrow direct bandgaps are 1.12 and 1.27 eV for Cu1.57 Bi4.57 S8 and Cu2.93 Bi4.89 S9 , respectively. Besides, this method could also be applied to synthesize the Cu3 BiS3 phase with a new nanoplate morphology. The as-synthesized Cu-Bi-S samples show Cu/Bi ratio-dependent photoresponsive properties. This study not only reports the structure and bandgap of two ternary sulfides, which have only been discovered in the mineral previously, but also provides an efficient method for synthesizing Bi-rich ternary chalcogenide nanocrystals.

Synthesis of compositionally controllable Cu2(Sn1-xGex)S3 nanocrystals with tunable band gaps.

In this work, we show that compositionally controlled Cu2(Sn1-xGex)S3 nanocrystals can be successfully synthesized by the hot-injection method through careful tuning the Ge/(Sn+Ge) precursor ratio. The band gaps of the resultant nanocrystals are demonstrated to be linearly tuned from 1.45 to 2.33 eV by adjusting the composition parameter x of the Ge/(Sn+Ge) ratio from 0.0 to 1.0. The crystalline structures of the resultant NCs have been studied by the X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), select area electron diffraction (SAED), and Raman spectroscopy. A ligand exchange procedure is further performed to replace the native ligands on the surface of the NCs with sulfur ions. The photoresponsive behavior indicates the potential use of as-prepared Cu2(Sn1-xGex)S3 nanocrystals in solar energy conversion systems. The synthesis of compositionally controlled Cu2(Sn1-xGex)S3 nanocrystals reported herein provides a way for probing the effect of Ge inclusion in the Cu-Sn-S system thin films.

Synergistic effects of intrinsic cation disorder and electron-deficient substitution on ion and electron conductivity in La1-xSrxCo0.5Mn0.5O3-δ (x = 0, 0.5, and 0.75).

The effects of intrinsic cation disorder and electron-deficient substitution for La1-xSrxCo0.5Mn0.5O3-δ (LSCM, x = 0, 0.5, and 0.75) on oxygen vacancy formation, and their influence on the electrochemical properties, were revealed through a combination of computer simulation and experimental study. First-principles calculations were first performed and found that the tendency of the oxygen vacancy formation energy was Mn(3+)-O*-Mn(4+) < Co(2+)-O*-Co(3+) < Co(2+)-O*-Mn(4+), meaning that antisite defects not only facilitate the formation of oxygen vacancy but introduce the mixed-valent transition-metal pairs for high electrical conductivity. Detailed partial density of states (PDOS) analysis for Mn on Co sites (MnCo) and Co on Mn sites (CoMn) indicate that Co(2+) is prone to being Co(3+) while Mn(4+) is prone to being Mn(3+) when they are on antisites, respectively. Also it was found that the holes introduced by Sr tend to enter the Co sublattice for x = 0.5 and then the O sublattice when x = 0.75, which further promotes oxygen vacancy formation, and these results are confirmed by both the calculated PDOS results and charge-density difference. On the basis of microscopic predictions, we intentionally synthesized a series of pure LSCM compounds and carried out comprehensive characterization. The crystal structures and their stability were characterized via powder X-ray Rietveld refinements and in situ high-temperature X-ray diffraction. X-ray photoelectron spectroscopy testified to the mixed oxidation states of Co(2+)/Co(3+) and Mn(3+)/Mn(4+). The thermal expansion coefficients were found to match the Ce0.8Sm0.2O2-δ electrolyte well. The electrical conductivities were about 41.4, 140.5, and 204.2 S cm(-1) at doping levels of x = 0, 0.5, and 0.75, and the corresponding impedances were 0.041, 0.027, and 0.022 Ω cm(2) at 850 °C, respectively. All of the measured results testify that Sr-doped LaCo0.5Mn0.5O3 compounds are promising cathode materials for intermediate-temperature solid oxide fuel cells.