Comprehensive cytotoxicity studies of superparamagnetic iron oxide nanoparticles

Recently lots of efforts have been taken to develop superparamagnetic iron oxide nanoparticles (SPIONs) for biomedical applications. So it is utmost necessary to have in depth knowledge of the toxicity occurred by this material. This article is designed in such way that it covers all the associated toxicity issues of SPIONs. It mainly emphasis on toxicity occurred at different levels including cellular alterations in the form of damage to nucleic acids due to oxidative stress and altered cellular response. In addition focus is been devoted for in vitro and in vivo toxicity of SPIONs, so that a better therapeutics can be designed. At the end the time dependent nature of toxicity and its ultimate faith inside the body is being discussed.     

Outdoor supplementation systems for studies of the effects of increased UV-B radiation

Studies of the effects of increases in ultraviolet-B (UV-B) radiation on plants and terrestrial ecosystems have been undertaken using a variety of methods including: controlled-environment cabinets, glasshouses, outdoor filtration and outdoor supplementation using fluorescent UV-B lamps. Outdoor supplementation systems provide a method of study which creates only small alterations to the microclimate and the number of such studies has increased during the past 3 years. These supplementation systems differ in their methods of operation, equipment, UV-B exposure regime and experimental design. This essay surveys the systems currently developed, considers problems associated with their use and discusses these in relation to the interpretation of biological effects.     

趋磁细菌及磁小体的生物医学应用研究进展

近年来,趋磁细菌及其生物自身合成的磁小体由于良好的生物安全性逐渐被人们所认识,并被用于生物工程和医学应用研究。与人工化学合成磁性纳米颗粒相比,从趋磁细菌中提取的磁小体具有生物膜包被、生物相容性高、粒径均一及磁性高等优势。趋磁细菌因磁小体在其胞内呈链状排列,具有沿磁场方向泳动的能力,也被应用于各种应用研究。因此,综述了趋磁细菌及磁小体特性,并就最近的研究进展重点综述趋磁细菌和磁小体在生物工程及医学应用等领域的最新研究进展。     

微生物几丁质酶研究进展及应用*

几丁质由N-乙酰-D-氨基葡萄糖聚合而成,是自然界中仅次于纤维素的第二大类聚合物。微生物几丁质酶来源丰富,是生物降解或利用几丁质的主要媒介。野生型菌株几丁质酶产量低、活性弱,故近年来有关几丁质酶的研究侧重于对其产量及催化活性的提升等方面。此外,几丁质酶具有水解病原真菌细胞壁、破坏害虫体壁、生产N-乙酰氨基葡萄糖寡聚体或单体的应用价值,在医药、农业、食品加工等领域表现出巨大的市场潜力。综述微生物几丁质酶的来源、分类及工程改造,为后续几丁质酶的研究及开发利用提供参考。     

Recent advances in synthesis and surface modification of lanthanide-doped upconversion nanoparticles for biomedical applications

Lanthanide (Ln)-doped upconversion nanoparticles (UCNPs) with appropriate surface modification can be used for a wide range of biomedical applications such as bio-detection, cancer therapy, bio-labeling, fluorescence imaging, magnetic resonance imaging and drug delivery. The upconversion phenomenon exhibited by Ln-doped UCNPs renders them tremendous advantages in biological applications over other types of fluorescent materials (e.g., organic dyes, fluorescent proteins, gold nanoparticles, quantum dots, and luminescent transition metal complexes) for: (i) enhanced tissue penetration depths achieved by near-infrared (NIR) excitation; (ii) improved stability against photobleaching, photoblinking and photochemical degradation; (iii) non-photodamaging to DNA/RNA due to lower excitation light energy; (iv) lower cytotoxicity; and (v) higher detection sensitivity. Ln-doped UCNPs are therefore attracting increasing attentions in recent years. In this review, we present recent advances in the synthesis of Ln-doped UCNPs and their surface modification, as well as their emerging applications in biomedicine. The future prospects of Ln-doped UCNPs for biomedical applications are also discussed.     

基于酸信号转导系统的细菌耐酸机制及其应用

酸信号转导系统能够感知酸性环境并转化为信号来调控细菌内的各种耐酸机制,帮助细菌应对酸环境的压力,是耐酸细菌能够在酸性环境下存活的重要原因。本文介绍了在耐酸细菌中发挥重要作用的几种主要的酸信号转导系统：EvgS/EvgA、PhoQ/PhoP、ArsS/ArsR和CadC。从这些系统的结构组成及对耐酸系统的调控角度分析耐酸细菌在酸环境中如何进行信号转导,从而激活相应的耐酸机制,并有效应对酸胁迫。深入认识耐酸系统的调控机制,有助于多种耐酸元件的挖掘、优化设计与构建,能够提高目标菌株在酸性环境中的生长和代谢能力,有助于更好地利用高耐酸工程微生物进行有价值的代谢物的工业生产、酸性环境污染的生物修复,也为抑制耐酸致病菌的生长提供全新靶点。     

Preparation, circular dichroism induced helical conformation and optical property of chitosan acid salt complexes for biomedical applications

The efficient procedure for preparation of chitosan acid complexes containing aspartic acid, benzilic acid and terephthalic acid moieties in isopropyl alcohol under mild condition has been demonstrated. The ionic complexation between chitosan and the acid is confirmed by FTIR and ¹H NMR spectroscopy. The circular dichroism (CD) spectra of chitosan/aspartic acid complex showed negative (at λ = 312) band, chitosan/benzilic acid and chitosan/terephthalic complexes showed positive (at λ = 286 and 315 nm) band in DMSO, indicating that the polymers adopted helical (left-handed and last two right-handed) secondary structure. The inversion of the CD pattern in chitosan acid salt complexes suggests that there is a change in the chiral structure of the polymer system. Some physical properties and surface morphology were analyzed by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetry (TG) and scanning electron microscopy (SEM). Optical properties of chitosan derivatives are evaluated by photoluminescence (PL) spectroscopy which showed red shift. The introduction of acid moieties into chitosan increases the solubility in most of the organic solvents, which opens new perspectives for the employment of chitosan-based biohybrid in biomedical applications.