Anticyanobacterial effect of l-lysine on Microcystis aeruginosa

Cyanobacterial blooms can cause serious environmental problems and threaten aquatic organisms and human health. It is therefore essential to effectively control cyanobacterial blooms in aquatic ecosystems. In the present study, the anticyanobacterial effect of l-lysine on Microcystis aeruginosa was examined. The results showed that the growth of M. aeruginosa (>90%) was effectively inhibited by l-lysine at dosages of 5.0, 6.5, and 8.0 mg L⁻¹ after 3 d treatment. The content of superoxide anion radicals, MDA content and SOD activity in M. aeruginosa cells increased after 1 d of treatment with l-lysine (3.0, 5.0, 6.5, and 8.0 mg L⁻¹), revealing that l-lysine induced oxidative stress in the cyanobacterial cells. The chlorophyll-a and protein contents in M. aeruginosa treated with l-lysine (3.0, 5.0, 6.5, and 8.0 mg L⁻¹) decreased after 2 d, indicating damage of the photosynthetic system by l-lysine treatment. Additionally, the production of exopolysaccharide by M. aeruginosa also increased and the expression of polysaccharide synthesis genes was upregulated by 3.0 mg L⁻¹l-lysine after 3 d of treatment. In response to the algicidal effects of l-Lysine, M. aeruginosa upregulated exopolysaccharide synthesis. Electron microscopic observations demonstrated that the cell membrane of M. aeruginosa was broken down during treatment with l-lysine (≥3.0 mg L⁻¹). Our results revealed that the effects of l-lysine on M. aeruginosa cells were comprehensive, and l-lysine is therefore an efficient anticyanobacterial reagent.

l-lysine had an anticyanobacterial effect on Microcystis aeruginosa, which involved growth inhibition, physiological and metabolic disturbance, and cell membrane damage.     

A channel-structured Eu-based metal–organic framework with a zwitterionic ligand for selectively sensing Fe3+ ions

A novel Eu-based MOF [Eu(IMS1)₂]Cl·4H₂O (1) was successfully constructed based on a semi-rigid zwitterionic 1,3-bis(4-carboxylbenzyl)-imidazolium (IMS1) ligand, featuring a 3-fold interpenetrating dia net structure with a point symbol of 6⁶ and charged permanent micropores. Considering its excellent luminescent property as well as thermal and chemical stability, complex 1 was explored as a potential sensor for detecting Fe³⁺ ions. The results show that complex 1 has a high sensitivity and selectivity for Fe³⁺ based on a ‘turn-off’ effect, for which the electrostatic interaction between Fe³⁺ ions and the inner surface of the micropores may play a critical role. The fluorescence quenching mechanism reveals that dynamic quenching and competitive adsorption between Fe³⁺ and 1 lead to the quenching effect of 1.

A channel-structured Eu-based metal–organic framework with a zwitterionic ligand may serve as a sensor for selectively detecting Fe³⁺ ions.     

Preparation of thermo-responsive drug-loaded nanofibrous films created by electrospinning

We prepared thermosensitive and biocompatible drug-loaded nanofibrous films by an electrospinning technique using a block copolymer, poly(N-isopropylacrylamide)-b-poly(l-lactide) (PNLA), and poly(l-lactide) (PLLA). The copolymer PNLA was synthesized by the radical polymerization of N-isopropylacrylamide (NIPAAm), followed by the ring-opening polymerization of l-lactide. The properties of PNIPAAm and PNLA were selectively discussed based on the results of NMR, FT-IR, GPC, and CA analyses. Because of the low molecular weight of PNIPAAm and PNLA and the hydrolysis of PNLA resulting from its hydrophilicity, these copolymers were inappropriate for electrospinning separately. Hence, a mixture of PNLA and PLLA was used to prepare electrospun nanofibrous films. SEM images of the PNLA/PLLA electrospun films showed that homogeneous fibres with smooth surfaces were obtained. In vitro release studies indicated that the drug-release rate of the PNLA/PLLA electrospun nanofibrous films can be adjusted by the content and molecular weight of PNLA and by the environmental temperature. The results demonstrate that electrospinning is a promising way to create stimuli-responsive fibrous films with potential applications in the design of controllable drug delivery systems.

Thermosensitive and biocompatible PNLA/PLLA drug-loaded nanofibrous films with different morphologies and controlled drug release behaviors by electrospinning technique.     

An antibacterial collagen membrane crosslinked by the inclusion complex of β-cyclodextrin dialdehyde and ofloxacin for bacterial keratitis

Infectious keratitis is one of the leading causes of blindness in the world, especially in developing countries. Corneal transplant surgery is a feasible treatment for bacterial keratitis when drug therapy cannot be effective. However, the amount of corneal donors is far from requirements of clinical treatment and thus, the prognosis of bacterial keratitis is not satisfactory. In this study, we developed a novel antibacterial corneal repair material (β-CD-DA/OFLX-Col) for bacterial keratitis. The inclusion complex of β-cyclodextrin dialdehyde (β-CD-DA) with ofloxacin formed by host–guest interaction was used as both a drug vector and a crosslinker for further reaction with the amino groups on lysine of collagen chains. Physical properties, cytocompatibility, and antibacterial property of β-CD-DA/OFLX-Col film were characterized. The results indicated that the film was mainly transparent and possessed superior mechanical properties. Moreover, human corneal epithelial cells could adhere to the film and proliferate normally, indicating that the β-CD-DA/OFLX-Col film was non-cytotoxic and had good biocompatibility. Most importantly, the β-CD-DA/OFLX-Col film exhibited prominent antibacterial effects against E. coli and S. aureus in vitro, which could minimize the risks of infection. The prepared β-CD-DA/OFLX-Col film could greatly increase bioavailability of drugs and reduce toxic side effects, thus displaying great potential in bacterial keratitis treatment.

The synthesis of antibacterial collagen membrane crosslinked by the inclusion complex of β-cyclodextrin dialdehyde and ofloxacin.     

腹腔感染病原菌及其耐药性

目的了解腹腔感染病原菌构成及其耐药性,为临床腹腔感染的治疗提供参考依据。方法对某院2011年1月—2013年12月住院患者送检的腹腔感染标本进行菌种鉴定及药物敏感性检测,并将数据输入WHONET5.6软件进行统计分析。结果 15 946份腹腔感染标本分离非重复病原菌810株,培养阳性率5.08%;革兰阴性杆菌485株(59.88%),革兰阳性菌275株(33.95%),真菌50株(6.17%);居前5位的病原菌分别为大肠埃希菌(24.20%)、屎肠球菌(15.06%)、鲍曼不动杆菌(8.89%)、肺炎克雷伯菌(7.66%)和凝固酶阴性葡萄球菌(6.91%)。产超广谱β-内酰胺酶(ESBLs)大肠埃希菌和肺炎克雷伯菌检出率分别为59.18%和32.79%,各种肠杆菌科细菌对亚胺培南仍高度敏感,但对碳青霉烯类耐药的菌株占4.08%~6.67%;多重耐药鲍曼不动杆菌占52.11%(37/71),耐甲氧西林金黄色葡萄球菌(MRSA)占53.57%(15/28),耐甲氧西林凝固酶阴性葡萄球菌(MRCNS)占71.43%(40/56),耐万古霉素屎肠球菌(VRE)占8.26%。结论该院腹腔感染病原菌主要是以大肠埃希菌为代表的革兰阴性菌,屎肠球菌是最常见革兰阳性致病菌,细菌耐药形势严峻。     

超声检查和MRI在产前诊断胎儿Dandy-Walker变异型中的对比研究

目的回顾性分析胎儿头颅超声检查(US)和MRI在产前诊断胎儿Dandy-Walker变异型(DWV)中的应用价值。方法选择2011年1月至2013年9月在四川大学华西第二医院经胎儿头颅US疑诊为胎儿DWV的11例胎儿为研究对象,并同时对其进行头颅MRI检查。对疑诊为胎儿DWV者随访至引产后或生后1年,以引产后胎儿的尸检结果或随访1年后对患儿再次进行头颅MRI检查结果及其临床表现作为诊断DWV的金标准,并统计学比较胎儿头颅US及MRI产前诊断该病的正确率。本研究遵循的程序符合四川大学华西第二医院人体试验委员会制定的伦理学标准,得到该委员会批准,征得受试对象监护人知情同意,并与之签署临床研究知情同意书。结果经头颅US疑诊为胎儿DWV的11例胎儿,同时进行头颅MRI检查结果为:正常胎儿为6例,诊断为胎儿DWV为5例。根据胎儿DWV诊断的金标准,胎儿头颅MRI对胎儿DWV的产前诊断正确率显著高于头颅US,且差异有统计学意义(100.0%vs45.4%,P=0.012)。结论胎儿头颅US是产前诊断胎儿中枢神经系统疾病的首选方法。对US疑诊为胎儿DWV者进一步采取头颅MRI检查确诊,是临床诊断胎儿DWV的必要补充。     

Application of HPLC mixed‐mode chromatography in determining radiochemical purity of [14C] labeled metformin hydrochloride

Metformin is currently prescribed worldwide to treat type 2 diabetes, and therefore, radiolabeled [¹⁴C] metformin is often prepared for clinical comparisons of new drug candidates. Prior to using the radiolabeled metformin, the purity needs to be determined to ensure the quality of the material. While typical reversed‐phase LC methods are often the first choice for purity analysis, they are not suitable for this determination because the compound is poorly retained under these conditions. Mixed‐mode chromatography has been demonstrated to overcome these retention issues, and therefore, this methodology was utilized for the purity determination of radiolabeled metformin.