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.
The composites of graphene oxide (GO) decorated by MnFe 2 O 4 have been synthesised via a green and facile strategy that the pristine GO/MnSO 4 suspension prepared by Hummers method was directly utilised to convert into the GO-MnFe 2 O 4 composites. The as-prepared composites were characterised using X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectra and X-ray photoelectron spectroscopy. The results indicated that the GO-MnFe 2 O 4 composites were successfully synthesised. The removal behaviours of Pb 2+ and Cu 2+ onto GO-MnFe 2 O 4 were investigated, which indicated that the composites exhibited great adsorption property in aqueous solution. The adsorption process could be fitted well by the pseudo-second-order model and Langmuir isotherm. The thermodynamic studies indicated that the adsorption process of Pb 2+ and Cu 2+ onto GO-MnFe 2 O 4 composites was spontaneous and endothermic in nature. Furthermore, the maximum adsorption capacities for Pb 2+ and Cu 2+ calculated from Langmuir model were about 263.85 and 103.41 mg/g at 318 K, respectively. Based on the results from the reusability experiments, the as-prepared GO-MnFe 2 O 4 composites could be used as a potential adsorbent for removing Pb 2+ and Cu 2+ ions from aqueous solutions.
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