Expanding the Spectrum of Antibiotics Capable of Killing Multidrug-Resistant Staphylococcus aureus and Pseudomonas aeruginosa

Infections from antibiotic-resistant Staphylococcus aureus and Pseudomonas aeruginosa are a serious threat because reduced antibiotic efficacy complicates treatment decisions and prolongs the disease state in many patients. To expand the arsenal of treatments against antimicrobial-resistant (AMR) pathogens, 600-Da branched polyethylenimine (BPEI) can overcome antibiotic resistance mechanisms and potentiate β-lactam antibiotics against Gram-positive bacteria. BPEI binds cell-wall teichoic acids and disables resistance factors from penicillin binding proteins PBP2a and PBP4. This study describes a new mechanism of action for BPEI potentiation of antibiotics generally regarded as agents effective against Gram-positive pathogens but not Gram-negative bacteria. 600-Da BPEI is able to reduce the barriers to drug influx and facilitate the uptake of a non-β-lactam co-drug, erythromycin, which targets the intracellular machinery. Also, BPEI can suppress production of the cytokine interleukin IL-8 by human epithelial keratinocytes. This enables BPEI to function as a broad-spectrum antibiotic potentiator, and expands the opportunities to improve drug design, antibiotic development, and therapeutic approaches against pathogenic bacteria, especially for wound care.     

Hyperbranched Polyethylenimine Modified Waste Fiberboard Activated Carbon for Enhanced Adsorption of Hexavalent Chromium

The objective of this work is to prepare a hyperbranched polyethylenimine (HBPEI) grafted activated carbon obtained from waste fiberboard for effectively removing Cr(VI) from aqueous solution. The waste fiberboard activated carbon (WFAC) was modified by HBPEI and cross-linked with glutaraldehyde (GA). The optimal modified conditions were as follows: HBPEI molecular weight 10,000 g/mol, HBPEI/WFAC (w/w) 0.5, GA concentration 0.25%, reaction time 60 min. Both pristine WFAC and HBPEI–WFAC were characterized by Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET), Scanning electronic microscopy (SEM), and Roman spectra. XPS data showed the obvious increase in nitrogen (from 0.72% to 6.65%) after modification. The results of FTIR and XPS suggested that HBPEI was chemically bonded onto the WFAC by the glutaraldehyde (GA) between the amine groups of WFAC and that of HBPEI. HBPEI was also probably grafted onto WFAC through the intermolecular interaction between the carboxylate groups of WFAC and the amine groups of HBPEI. However, the BET surface area of modified WFAC declined slightly (about 200 m²/g). The I_D/I_G of modified WFAC decreased from 0.92 to 0.82, which indicated that the modification process had no significant effect on the graphitization of activated carbon. The adsorption property onto HBPEI–WFAC and the factors containing contact time, pH value, and Cr(VI) concentration were also investigated. Analysis of the Cr(VI) adsorption data was well simulated by the pseudo-second-order kinetic model and Langmuir adsorption isotherm model, and maximum Cr(VI) uptake of HBPEI–WFAC was 500 mg/g.     

醇脱氢酶在聚乙烯膜表面的固定化研究

以聚丙烯酸（PAA）改性的聚乙烯（PE）膜为载体，研究了醇脱氢酶（ADH）的两种固定化路线，并以甲醛为底物考察了固定化酶的催化性能。路线1用聚乙烯亚胺（PEI）进一步改性，使用戊二醛（GA）固定化ADH。最优固定化pH为6.0，温度为5～15℃，酶浓度为1.0 mg/ml，GA浓度为0.01%(质量)；固定化酶的最适反应pH为6.5，温度为15～30℃，反应速率最高为9.6 μmol/(L·min)；重复利用10次后可保持47.3%的活性。路线2以PAA-PE为载体，用1-(3-二甲氨基丙基)-2-乙基碳二亚胺盐酸盐（EDC）和N-羟基琥珀酰亚胺（NHS）为活化剂，固定化ADH。EDC和NHS最优摩尔比为1∶0.5，固定化时间为24 h；固定化酶的最适反应pH为6.5，温度为20～37℃，反应速率为15.58 μmol/(L·min)；重复利用10次后可保持53.8%的活性。     

Dendrimer as nanocarrier for drug delivery

Dendrimers are novel three dimensional, hyperbranched globular nanopolymeric architectures. Attractive features like nanoscopic size, narrow polydispersity index, excellent control over molecular structure, availability of multiple functional groups at the periphery and cavities in the interior distinguish them amongst the available polymers. Applications of dendrimers in a large variety of fields have been explored. Drug delivery scientists are especially enthusiastic about possible utility of dendrimers as drug delivery tool. Terminal functionalities provide a platform for conjugation of the drug and targeting moieties. In addition, these peripheral functional groups can be employed to tailor-make the properties of dendrimers, enhancing their versatility. The present review highlights the contribution of dendrimers in the field of nanotechnology with intent to aid the researchers in exploring dendrimers in the field of drug delivery.     

Low molecular weight PEI-grafted carboxyl-modified soybean protein as gene carriers with reduced cytotoxicity and greatly improved transfection in vitro

SA-SP-PEI were synthesized via acylation reaction between carboxyl-modified soybean protein (SA-SP) and branched polyethylenimine (PEI) with molecular weight of 600, 1200, and 1800?Da, and designed as SA-SP-PEI600, SA-SP-PEI1200, and SA-SP-PEI1800, respectively. SA-SP-PEI could effectively condense plasmid DNA into nanoscale polyplexes and protect them from enzymatic digestion. MTT assay revealed that SA-SP-PEI exhibited reduced cytotoxicity on 293?T and SH-SY5Y cells. SA-SP-PEI1800/DNA complexes hold highest transfection efficiency on 293?T and SH-SY5Y cells with or without 10% serum, which was owing to its better serum stable and improved biocompatibility. Such polycationic soybean proteins have great potentials as gene carriers by further optimization.     

Facile fabrication of graphene oxide-polyethylenimine composite and its application for the Cr(VI) removal

A binary composite consisting of graphene oxide (GO) and polyethylenimine (PEI) was fabricated by a facile physical mixing. Fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscope (FE-SEM), thermo-gravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and Zeta potential were used to characterize the prepared graphene oxide-polyethylenimine composite (GOPC). A series of experiments were carried out to investigate the effects of some important parameters, such as molecular weight of PEI, pH, time and temperature, on the adsorption efficiency of GOPC. Due to the high amine density of GOPC, its adsorption for Cr(VI) occurred more easily at lower pH mainly via electrostatic interaction. The adsorption process matched well with the Langmuir isotherm model and the pseudo-second-order kinetic model. The maximum adsorption capacity from the Langmuir model was 370.37 mg/g at pH 2.0 and 45°C for GOPC. Thermodynamic parameters revealed spontaneous and endothermic nature of the Cr(VI) adsorption onto GOPC. The main adsorption mechanism of GOPC toward Cr(VI) was electrostatic interaction. The adsorption-desorption experiments suggested GOPC was easily recycled and its stable adsorption capacity endowed it great potential as an adsorbent of Cr(VI) from wastewater.     

Enhanced antibacterial activity of tetramethylguanidinium-conjugated linear polyethylenimine polymers

In the present study, varying amounts of tetramethylguanidinium moiety have been conjugated to linear polyethylenimine to obtain linear polyethylenimine-tmg (LPTG) polymers. Incorporation of hydrophobic and highly basic moiety in the polymeric backbone resulted in the significant improvement in the antibacterial activity which was confirmed by zone of inhibition and MIC assays. Further, the results of transmission electron microscopy and confocal studies revealed that the projected LPTG polymers possessed higher antibacterial activity than the native polymer. In addition, these modified polyethylenimine (PEI) polymers were capable of reducing auric chloride into stable gold nanoparticles. These polyamine-stabilized gold nanoparticles can be used in various biomedical applications.     

Electrochemical regeneration of partially ethoxylated polyethylenimine used in the polymer-supported ultrafiltration of copper

This work is focussed on the application of an electrochemical technology to regenerate the bonding agent of a polymer-supported ultrafiltration process, technique commonly used to remove metal ions from wastewaters. To do this, a batch rotating-electrode electrochemical cell has been set up to recover the copper bind to partially ethoxylated polyethyleneimine by electrodeposition. The influence of the main parameters (current efficiency, stirring rate, pH, electrode material and nature of the counterion) on the performance of the process has been studied. Current efficiency is clearly enhanced with the stirring rate, reaching values as high as 0.93 for the optimum working conditions. Regarding pH, this variable has been observed to play an important role in process efficiency. Thus, it has been found that the reactor can operate at pH 4 without affecting process performance. This is a clear advantage with respect to other regeneration techniques and also to previous works of electrochemical regeneration. The electrode material seems to have a clear influence on process behaviour and especially on the appearance of a first transitory stage with lower current efficiency. Finally, the electrolyte salt also influences significantly on the results and the presence of sulphate as counterion leads to the best system performance.