In this article, the synthesis of two amphiphilic polyaspartamide copolymers, useful to obtain polymeric nanoparticles without
using surfactants or stabilizing agents, is described. These copolymers were obtained starting from α,β-poly-(N-2-hydroxyethyl)-dl-aspartamide (PHEA) by following a novel synthetic strategy. In particular, PHEA and its pegylated derivative (PHEA-PEG2000) were functionalized with poly(lactic acid) (PLA) through 1,1′-carbonyldiimidazole (CDI) activation to obtain PHEA–PLA and
PHEA-PEG2000–PLA graft copolymers, respectively. These copolymers were properly purified and characterized by 1H-NMR, FT-IR, and Size Exclusion Chromatography (SEC) analyses, which confirmed that derivatization reactions occurred. Nanoparticles
were obtained from PHEA–PLA and PHEA-PEG2000–PLA graft copolymers by using the high pressure homogenization-solvent evaporation method, avoiding the use of surfactants
or stabilizing agents. Polymeric nanoparticles were characterized by dimensional analysis, before and after freeze-drying
process, and Scanning Electron Microscopy (SEM). Zeta potential measurements and X-ray Photoelectron Spectroscopy (XPS) analysis
demonstrated the presence of PEG and/or PHEA onto the PHEA-PEG2000–PLA and PHEA–PLA nanoparticle surface, respectively. 相似文献
Here, the synthesis and the characterization of novel amphiphilic graft copolymers with tunable properties, useful in obtaining polymeric fluorescent nanoparticles for application in imaging, are described. These copolymers are obtained by chemical conjugation of rhodamine B (RhB) moieties, polylactic acid (PLA), and O‐(2‐aminoethyl)‐O′‐methyl poly(ethylene glycol) (PEG) on α,β‐poly(N‐2‐hydroxyethyl)‐d,l ‐aspartamide (PHEA). In particular, PHEA is first functionalized with RhB to obtain PHEA–RhB with a derivatization degree in RhB (DDRhB) equal to 0.55 mol%. By varying the reaction conditions, different amounts of PLA are grafted on PHEA–RhB to obtain PHEA‐RhB‐PLA with DDPLA equal to 1.9, 4.0, and 6.2 mol%. Then, PEG chains are grafted on PHEA‐RhB‐PLA derivatives to obtain PHEA‐RhB‐PLA‐PEG graft copolymers. The preparation of polymeric fluorescent nanoparticles with tunable properties and spherical shape is described by using PHEA‐RhB‐PLA‐PEG with DD in PLA and PEG equal to 4.0 and 4.9 mol%, by following easily scaling up processes, such as emulsion‐solvent evaporation and high pressure homogenization (HPH)‐solvent evaporation techniques.
Electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) offers a renewable approach to produce the value-added platform chemical 2,5-furandicarboxylic acid (FDCA). The key for the economic viability of this approach is to develop active and selective electrocatalysts. Nevertheless, a reliable catalyst evaluation protocol is still missing, leading to elusive conclusions on criteria for a high-performing catalyst. Herein, we demonstrate that besides the catalyst identity, secondary parameters such as materials of conductive substrates for the working electrode, concentration of the supporting electrolyte, and electrolyzer configurations have profound impact on the catalyst performance and thus need to be optimized before assessing the true activity of a catalyst. Moreover, we highlight the importance of those secondary parameters in suppressing side reactions, which has long been overlooked. The protocol is validated by evaluating the performance of free-standing Cu-foam, and CuCoO modified with NaPO2H2 and Ni, which were immobilized on boron-doped diamond (BDD) electrodes. Recommended practices and figure of merits in carefully evaluating the catalyst performance are proposed. 相似文献
Here, a novel strategy of formulating efficient polymeric carriers based on the already described INU-IMI-DETA for gene material whose structural, functional, and biological properties can be modulated and improved was successfully investigated. In particular, two novel derivatives of INU-IMI-DETA graft copolymer were synthesized by chemical functionalisation with epidermal growth factor (EGF) or polyethylenglycol (PEG), named INU-IMI-DETA-EGF and INU-IMI-DETA-PEG, respectively, in order to improve the performance of already described “inulin complex nanoaggregates” (ICONs). The latter were thus prepared by appropriately mixing the two copolymers, by varying each component from 0 to 100 wt% on the total mixture, named EP-ICONs. It was seen that the ability of the INU-IMI-DETA-EGF/INU-IMI-DETA-PEG polymeric mixture to complex siGL3 increases with the increase in the EGF-based component in the EP-ICONs and, for each sample, with the increase in the copolymer:siRNA weight ratio (R). On the other hand, the susceptibility of loaded siRNA towards RNase decreases with the increase in the pegylated component in the polymeric mixture. At all R values, the average size and the zeta potential values are suitable for escaping from the RES system and suitable for prolonged intravenous circulation. By means of biological characterisation, it was shown that MCF-7 cells are able to internalize mainly the siRNA-loaded into EGF-decorated complexes, with a significant difference from ICONs, confirming its targeting function. The targeting effect of EGF on EP-ICONs was further demonstrated by a competitive cell uptake study, i.e., after cell pre-treatment with EGF. Finally, it was shown that the complexes containing both EGF and PEG are capable of promoting the internalisation and therefore the transfection of siSUR, a siRNA acting against surviving mRNA, and to increase the sensitivity to an anticancer agent, such as doxorubicin. 相似文献
Reaction of [GaBi3]2? with [Sm(C5Me4H)3] yielded the first protonated ternary intermetalloid clusters [Sm@Ga3?xH3?2xBi10+x]3? ( 1 ; x=0,1). The presence of the Ga? H bonds and the transfer of electrons and protons during the formation of 1 were elucidated by a combination of experimental and quantum chemical methods, thereby rationalizing the role of the solvent ethane‐1,2‐diamine as a Brønsted acid. As an organic by‐product, we observed the previously unknown octamethylfulvene ( 2 ) upon C? C coupling of (C5Me4H)?. 相似文献
La3B6O13(OH) was obtained by a high-pressure/high-temperature experiment at 6 GPa and 1673 K. The compound crystallizes in the space group P21 (no. 4) with the lattice parameters a=4.785(2), b=12.880(4), c=7.433(3) Å, and β=90.36(10)°, and is built up of corner- as well as edge-sharing BO4 tetrahedra. It represents the first acentric high-pressure borate containing these B2O6 entities. The compound develops borate layers of „sechser“-rings with the La3+ cations positioned between the layers. Single-crystal and powder X-ray diffraction, vibrational and MAS NMR spectroscopy, second-harmonic generation (SHG) and thermoanalytical measurements, as well as computational methods were used to affirm the proposed structure and the B2O6 entities. 相似文献
The continuous emergence of antimicrobial resistance is causing a threat to patients infected by multidrug-resistant pathogens. In particular, the clinical use of aminoglycoside antibiotics, broad-spectrum antibacterials of last resort, is limited due to rising bacterial resistance. One of the major resistance mechanisms in Gram-positive and Gram-negative bacteria is phosphorylation of these amino sugars at the 3’-position by O-phosphotransferases [APH(3’)s]. Structural alteration of these antibiotics at the 3’-position would be an obvious strategy to tackle this resistance mechanism. However, the access to such derivatives requires cumbersome multi-step synthesis, which is not appealing for pharma industry in this low-return-on-investment market. To overcome this obstacle and combat bacterial resistance mediated by APH(3’)s, we introduce a novel regioselective modification of aminoglycosides in the 3’-position via palladium-catalyzed oxidation. To underline the effectiveness of our method for structural modification of aminoglycosides, we have developed two novel antibiotic candidates overcoming APH(3’)s-mediated resistance employing only four synthetic steps. 相似文献