涡旋磁纳米颗粒——崭新的生物医用磁性纳米平台

相比于超顺磁性纳米颗粒,具有涡旋磁畴的磁性纳米颗粒,由于独特的磁化闭合分布、较大的粒径尺寸及外加磁场中的磁化翻转特性,使得其兼具弱的颗粒间磁相互作用和更优异的磁学性能,在生物医学领域展现出了更好的应用优势和潜力.本综述结合近年来国内外对涡旋磁畴的研究及涡旋磁纳米颗粒在生物医学领域的报道,提出了一类新型的生物医用涡旋磁溶胶体系,并以涡旋磁氧化铁纳米盘和纳米环为例,介绍了涡旋磁纳米颗粒的化学合成,并着重论述了这类具有独特涡旋畴结构的纳米颗粒在磁共振成像、抗肿瘤治疗等生物医学应用上的最新研究进展.     

胃癌血清的表面增强拉曼光谱研究

表面增强拉曼光谱技术在癌症诊断领域已经有了广泛的研究和应用,本文利用金纳米溶胶为增强基底,采用便携式近红外拉曼光谱系统,对89例胃癌患者及正常人血清样本进行了SERS光谱探测。结果表明,血清的特征峰主要归属于氨基酸,其次是核酸、糖类及脂类。相比于正常人血清SERS光谱,胃癌血清中归属于核酸的特征峰强度都较高,大部分归属于蛋白质的特征峰强度较低,与医学研究结论相符。说明SERS技术可以有效地反映胃癌患者和正常人血清的差异,为后期SERS技术快速诊断胃癌提供了实验基础。     

Oligonucleotide-displaced organic monolayer-protected silver nanoparticles and enhanced luminescence of their salted aggregates

N-(2-mercaptopropionyl)glycine (tiopronin) monolayer-protected silver particles were partially displaced by single-stranded oligonucleotides through ligand exchanges. The oligonucleotide-displaced particles could be hybridized with complementary fluorophore-labeled oligonucleotides. Both the oligonucleotide-displaced and hybridized particles could be aggregated by electrostatic interactions with salt in buffer solution, and the aggregates displayed enhanced luminescence from fluorophores. This result suggests the possible application of surface-enhanced fluorescence from metallic nanoparticle aggregation for DNA detection.     

Quantification of non‐specific binding of magnetic micro‐ and nanoparticles using cell tracking velocimetry: Implication for magnetic cell separation and detection

The maturation of magnetic cell separation technology places increasing demands on magnetic cell separation performance. While a number of factors can cause sub‐optimal performance, one of the major challenges can be non‐specific binding of magnetic nano‐ or microparticles to non‐targeted cells. Depending on the type of separation, this non‐specific binding can have a negative effect on the final purity, the recovery of the targeted cells, or both. In this work, we quantitatively demonstrate that non‐specific binding of magnetic nanoparticles can impart a magnetization to cells such that these cells can be retained in a separation column and thus negatively impact the purity of the final product and the recovery of the desired cells. Through experimental data and theoretical arguments, we demonstrate that the number of MACS magnetic particles needed to impart a magnetization that is sufficient to cause non‐targeted cells to be retained in the column to be on the order of 500–1,000 nanoparticles. This number of non‐specifically bound particles was demonstrated experimentally with an instrument, cell tracking velocimeter, CTV, and it is demonstrated that the sensitivity of the CTV instrument for Fe atoms contained in magnetic nanoparticles on the order of 1 × 10^?15 g/mL of Fe. Biotechnol. Bioeng. 2010;105: 1078–1093. © 2009 Wiley Periodicals, Inc.     

Resonance Rayleigh-scattering method for the determination of proteins with gold nanoparticle probe

Gold nanoparticles with a 12-nm diameter were used as probes for the determination of proteins by resonance Rayleigh-scattering techniques. In weak acidic solution, large amounts of citrate anions will self-assemble on the surface of positively charged gold nanoparticles to form supermolecular compounds with negative charges. Below the isoelectric point, proteins with positive charges such as human serum albumin (HSA), bovine serum albumin (BSA), and ovalbumin (Ova) can bind gold nanoparticles to form larger volume products (the diameter of the binding product of gold nanoparticles with HSA is 23 nm.) through electrostatic force, hydrogen bonds, and hydrophobic effects, which can result in a red shift of the maximum absorption wavelength, the remarkable enhancement of the resonance Rayleigh-scattering intensity (RRS), and the appearance of the RRS spectra. At the same time, the second-order-scattering (SOS) and frequency-doubling-scattering (FDS) intensities are also enhanced. The binding products of gold nanoparticles with different proteins have similar spectral characteristics and the maximum wavelengths are located near 303 nm for RRS, 540 nm for SOS, and 390 for FDS, respectively. The scattering enhancement (DeltaI) is directly proportional to the concentration of proteins. Among them, the RRS method has the highest sensitivity and the detection limits are 0.38 ng/ml for HSA, 0.45 ng/ml for BSA, and 0.56 ng/ml for Ova, separately. The methods have good selectivity. A new RRS method for the determination of trace proteins using a gold nanoparticle probe has been developed. Because gold nanoparticle probes do not need to be modified chemically in advance, the method is very simple and fast.     

Collagen adhesin–nanoparticle interaction impairs adhesin's ligand binding mechanism

Background

Pathogenic bacteria specifically recognize extracellular matrix (ECM) molecules of the host (e.g. collagen, fibrinogen and fibronectin) through their surface proteins known as MSCRAMMs (Microbial Surface Components Recognizing Adhesive Matrix Molecules) and initiate colonization. On implantation, biomaterials easily get coated with these ECM molecules and the MSCRAMMs mediate bacterial adherence to biomaterials. With the rapid rise in antibiotic resistance, designing alternative strategies to reduce/eliminate bacterial colonization is absolutely essential.

Methods

The Rhusiopathiae surface protein B (RspB) is a collagen‐binding MSCRAMM of Erysipelothrix rhusiopathiae. It also binds to abiotic surfaces. The crystal structure of the collagen‐binding region of RspB (rRspB_31–348) reported here revealed that RspB also binds collagen by a unique ligand binding mechanism called “Collagen Hug” which is a common theme for collagen‐binding MSCRAMMs of many Gram-positive bacteria. Here, we report the interaction studies between rRspB_31–348 and silver nanoparticles using methods like gel shift assay, gel permeation chromatography and circular dichroism spectroscopy.

Results

The “Collagen Hug” mechanism was inhibited in the presence of silver nanoparticles as rRspB_31–348 was unable to bind to collagen. The total loss of binding was likely because of rRspB_31–348 and silver nanoparticle protein corona formation and not due to the loss of the structural integrity of rRspB_31–348 on binding with nanoparticles as observed from circular dichroism experiments.

General significance

Interaction of rRspB_31–348 with silver nanoparticle impaired its ligand binding mechanism. Details of this inhibition mechanism may be useful for the development of antimicrobial materials and antiadhesion drugs.     

Fabrication of hierarchical hybrid structures using bio-enabled layer-by-layer self-assembly

Development of versatile and flexible assembly systems for fabrication of functional hybrid nanomaterials with well-defined hierarchical and spatial organization is of a significant importance in practical nanobiotechnology applications. Here we demonstrate a bio-enabled self-assembly technique for fabrication of multi-layered protein and nanometallic assemblies utilizing a modular gold-binding (AuBP1) fusion tag. To accomplish the bottom-up assembly we first genetically fused the AuBP1 peptide sequence to the C'-terminus of maltose-binding protein (MBP) using two different linkers to produce MBP-AuBP1 hetero-functional constructs. Using various spectroscopic techniques, surface plasmon resonance (SPR) and localized surface plasmon resonance (LSPR), we verified the exceptional binding and self-assembly characteristics of AuBP1 peptide. The AuBP1 peptide tag can direct the organization of recombinant MBP protein on various gold surfaces through an efficient control of the organic-inorganic interface at the molecular level. Furthermore using a combination of soft-lithography, self-assembly techniques and advanced AuBP1 peptide tag technology, we produced spatially and hierarchically controlled protein multi-layered assemblies on gold nanoparticle arrays with high molecular packing density and pattering efficiency in simple, reproducible steps. This model system offers layer-by-layer assembly capability based on specific AuBP1 peptide tag and constitutes novel biological routes for biofabrication of various protein arrays, plasmon-active nanometallic assemblies and devices with controlled organization, packing density and architecture.     

Therapeutic siRNA: principles, challenges, and strategies

RNA interference (RNAi) is a remarkable endogenous regulatory pathway that can bring about sequence-specific gene silencing. If harnessed effectively, RNAi could result in a potent targeted therapeutic modality with applications ranging from viral diseases to cancer. The major barrier to realizing the full medicinal potential of RNAi is the difficulty of delivering effector molecules, such as small interfering RNAs (siRNAs), in vivo. An effective delivery strategy for siRNAs must address limitations that include poor stability and non-targeted biodistribution, while protecting against the stimulation of an undesirable innate immune response. The design of such a system requires rigorous understanding of all mechanisms involved. This article reviews the mechanistic principles of RNA interference, its potential, the greatest challenges for use in biomedical applications, and some of the work that has been done toward engineering delivery systems that overcome some of the hurdles facing siRNA-based therapeutics.     

Combinatorial Synthesis of and High-throughput Protein Release from Polymer Film and Nanoparticle Libraries

Polyanhydrides are a class of biomaterials with excellent biocompatibility and drug delivery capabilities. While they have been studied extensively with conventional one-sample-at-a-time synthesis techniques, a more recent high-throughput approach has been developed enabling the synthesis and testing of large libraries of polyanhydrides¹. This will facilitate more efficient optimization and design process of these biomaterials for drug and vaccine delivery applications. The method in this work describes the combinatorial synthesis of biodegradable polyanhydride film and nanoparticle libraries and the high-throughput detection of protein release from these libraries. In this robotically operated method (Figure 1), linear actuators and syringe pumps are controlled by LabVIEW, which enables a hands-free automated protocol, eliminating user error. Furthermore, this method enables the rapid fabrication of micro-scale polymer libraries, reducing the batch size while resulting in the creation of multivariant polymer systems. This combinatorial approach to polymer synthesis facilitates the synthesis of up to 15 different polymers in an equivalent amount of time it would take to synthesize one polymer conventionally. In addition, the combinatorial polymer library can be fabricated into blank or protein-loaded geometries including films or nanoparticles upon dissolution of the polymer library in a solvent and precipitation into a non-solvent (for nanoparticles) or by vacuum drying (for films). Upon loading a fluorochrome-conjugated protein into the polymer libraries, protein release kinetics can be assessed at high-throughput using a fluorescence-based detection method (Figures 2 and 3) as described previously¹. This combinatorial platform has been validated with conventional methods² and the polyanhydride film and nanoparticle libraries have been characterized with ¹H NMR and FTIR. The libraries have been screened for protein release kinetics, stability and antigenicity; in vitro cellular toxicity, cytokine production, surface marker expression, adhesion, proliferation and differentiation; and in vivo biodistribution and mucoadhesion^1-11. The combinatorial method developed herein enables high-throughput polymer synthesis and fabrication of protein-loaded nanoparticle and film libraries, which can, in turn, be screened in vitro and in vivo for optimization of biomaterial performance.     

甘油三酯介质中制备壳聚糖纳米粒工艺研究

用乳化溶剂扩散法结合离子沉淀交联法从甘油三酯介质中制备壳聚糖纳米粒,用L9(34)正交设计优选纳米粒制备的处方工艺条件,用显微镜测定纳米粒的粒径,用透射电镜观察纳米粒的形态。结果:正交设计确定纳米粒制备的最优处方工艺条件为:搅拌速度150 r.min-1,壳聚糖质量分数0.10%,壳聚糖分子量9.1万,甘油三酯与壳聚糖酸溶液体积之比200:1,制备的纳米粒平均粒径为(150±50)nm。甘油三酯介质中制备壳聚糖纳米粒工艺简便,制剂具有广泛应用前景。