Transdermal drug delivery is a new means of delivering drugs through the skin to achieve therapeutic effects. Microneedles have several advantages, including low cost, easy self-administration, and high delivery efficiency. Different polymers affect the morphology, mechanical properties, and drug delivery efficiency of microneedles. To study the performance and limitations of microneedles (MNs), we prepared different ratios of polymers. MNs were fabricated from polyvinylpyrrolidone (PVP) and sodium carboxymethyl cellulose (CMC-Na) using the centrifugal molding method. Needle morphology, formability, and other properties of the polymers were evaluated to compare the performances of MNs with different ratios. PVP and CMC-Na were intermixed at different ratios with water as the solvent. The soluble MNs were prepared by mold casting. The morphology, thermodynamic properties, and crystallinity were studied using scanning electron microscopy (SEM), thermogravimetric analysis (TG), differential scanning calorimetric analysis (DSC), and X-ray diffraction (XRD). The results showed that composite microneedles have good thermal stability. Among the different compositions tested, the 10% PVP/2% CMC-Na composite microneedle demonstrated the best performance with a regular surface morphology and relatively high thermal decomposition and melting temperatures. These results indicate that microneedles with appropriate ratios of two different materials possess good formability and other properties.

Electrospinning technology is widely used for preparing biological tissue engineering scaffolds because of its advantages of simple preparation, accurate process parameters, and easy control. Poly(L-lactide) (PLLA) is regarded as a promising biomass-based polymer for use in electrospinning. The incorporation of Fe₃O₄ nanoparticles (NPs) could improve the osteogenic differentiation and proliferation of cells in the presence or absence of a static magnetic field (SMF). In this work, these two materials were blended together to obtain electrospun samples with better dispersibility and improved magnetic properties. First, composite PLLA and Fe₃O₄ NP fibers were prepared by means of electrospinning. The influence of electrospinning conditions on the morphology of the composite fibers was then discussed. Changes in magnetic properties and thermal stability resulting from the use of different PLLA/Fe₃O₄ mass ratios were also considered. Next, the morphology, crystal state, thermodynamic properties, and magnetic properties of the electrospun samples were determined using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and vibration sample magnetization (VSM). The results showed that the fibers prepared using PLLA with M_n = 170,000 exhibited good morphology when electrospun at 12 KV. The magnetic properties of PLLA/Fe₃O₄ composite electrospun fibers increased with the NP content, with the exception of thermal stability. The results of the present study may help to promote the further development of PLLA/Fe₃O₄ composite materials in the biomedical field.

Developing scaffolds with appropriate mechanical/structural features as well as tunable bioactivities are indispensable in the field of tissue engineering. This study focused on one such attempt to electrospin the copolymer of L-lactic acid (L-LA) and functional monomer (3(S)- [(benzyloxycarbony)methyl]-1,4-dioxane-2,5-dione, BMD) with small peptide modifications for the purpose of neural tissue engineering. Scanning Electron Microscopy (SEM) micrographs showed fabricated electrospun copolymer as porous and uniform nanofibrous materials with diameter in the range of 800–1000 nm. In addition, the modified scaffolds displayed a lower contact angle than poly(L-lactide) (PLLA) indicating higher hydrophilicity. To further incorporate the bioactive functions, the nanofibers were chemically coupled with small peptide (isoleucine-lysine-valine-alanine-valine, IKVAV). The incorporation of IKVAV onto the electrospun fiber was confirmed by X-ray photoelectron spectroscopy (XPS) and such incorporation did not affect the surface morphology or fiber diameters. To demonstrate the potential of applying the designed scaffolds for nerve regeneration, dorsal root ganglion (DRG) neurons were cultured on the nanofibers to examine the impact on neurite outgrowth of DRGs. The results indicated that the fabricated nanofibrous matrix with small peptide might be a potential candidate for neural tissue engineering.

Cobalt complexes have previously been reported to exhibit high faradaic efficiency in reducing CO₂ to CO. Herein, we synthesized capsule-like cobalt–polypyridine diamine complexes [Co(L¹)](BF₄)₂ (1) and [Co(L²) (CH₃CN)](BF₄)₂ (2) as catalysts for the electrocatalytic reduction of CO₂. Under catalytic conditions, complexes 1 and 2 demonstrated the electrocatalytic reduction of CO₂ to CO in the presence or absence of CH₃OH as a proton source. Experimental and computational studies revealed that complexes 1 and 2 undergo two consecutive reversible one-electron reductions on the cobalt core, followed by the addition of CO₂ to form a metallocarboxylate intermediate [Co^II(L)–CO₂²⁻]⁰. This crucial reaction intermediate, which governs the catalytic cycle, was successfully detected using high resolution mass spectrometry (HRMS). In situ Fourier-transform infrared spectrometer (FTIR) analysis showed that methanol can enhance the rate of carbon–oxygen bond cleavage of the metallocarboxylate intermediate. DFT studies on [Co^II(L)–CO₂²⁻]⁰ have suggested that the doubly reduced species attacks CO₂ on the C atom through the d_z² orbital, while the interaction with CO₂ is further stabilized by the π interaction between the metal d_xz or d_xz orbital with p orbitals on the O atoms. Further reductions generate a metal carbonyl intermediate [Co^I(L)–CO]⁺, which ultimately releases CO.

Fe ₃ O ₄ -OA was incorporated into P(VDF-TrFE) fibers via electrospinning. The resulting membranes exhibited a bone-like topological structure and physiological surface potential, showing cytocompatibility and great potential for bone defect repair.