Janus Particles: Synthesis, Self-assembly, Physical properties, and Applications

Posted on Thu, Jan 19, 2017

Janus particles named after Roman god Janus who was illustrated with two faces, one looking to the future, and the other to the past. Pierre-Gilles de Gennes mentioned the term Janus particle in his Nobel lecture on soft matter in 1991. Janus particles are synthesized by joining two or more different materials together. Each material imparts a unique and useful quality to the particle; therefore, one Janus particle can display multiple properties and functionalities. It is this fundamental asymmetry that makes Janus particles a powerful tool in biotechnology for biosensing, bioseparation, self-assembly, drug delivery, and much more. This blog post will summarize a lengthy and informative reviewarticle of the same title that was published in Chemical Reviews in 2013.

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Biphasic Janus particles with nanoscale anisotropy

Posted on Thu, Jan 12, 2017

 

Janus Particles and anisotropy

Janus particles (JPs) have two or more properties or functions wrapped up into one package. There are many different synthesis methods, properties, and applications for JPs. Anisotropy is defined as an object having a different physical property or different value when measured in different directions. Janus particles are anisotropic. Their properties are asymmetric. They can have a hydrophobic face and a hydrophilic face. They can have magnetic properties as well as optical reporters on the same particle. JPs can have different optical properties on either side. They can have different ligands on opposing faces. It is anisotropy that makes them useful tools for biosensing and bioseparation. One particle with multiple functionalities is often more useful than an isotropic particle with one property.

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Cell separation based on cell density

Posted on Thu, Jan 05, 2017

The ability to isolate cells is important in both clinical and research settings.  There are many available techniques for cell separation. These techniques differ in specificity of cell selection, cost of equipment, time to complete, technology needed, and skill required. Cell separation based on cell density is rapid and inexpensive, but is unspecific. Still, it is a fundamental technique that is commonly used in a variety of settings for general cell separation.

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Protein A magnetic beads for antibody capture and labeling

Posted on Thu, Dec 29, 2016

 

Antibodies labeled with fluorescent tags, radioactive molecules, biotin, enzymes, and other small molecules are essential for immunoassays, cell sorting, diagnostic assays, cell imaging, and other procedures. The attachment of small molecules to individual antibodies is not trivial, and to do it with a specific orientation is especially challenging. The purified antibody to be labeled must be in solution at high concentrations, and the process requires multiple washing steps. On-bead labeling methods are used to improve the labeling efficiency. Protein A binds to the Fc region of IgG antibodies across a variety of species, and is commonly used to capture antibodies onto a bead surface for isolation or for small molecule modification.

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Chemiluminescence examples

Posted on Thu, Dec 22, 2016

Chemiluminescence is the release of light from a chemical reaction. The light is released either from a high-energy intermediate itself or when a high-energy intermediate relaxes down to the lower energy final product. It is important to remember that chemiluminesence is the result of a chemical reaction, and is not the same as fluorescence. This means that chemiluminescent reactions do not need an input of excitation light of any kind. The overriding chemical formula of chemiluminescent reactions is

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Cell sorting techniques

Posted on Thu, Dec 15, 2016

Fundamental research often involves the study of isolated cell populations. It is these enriched populations that enable researchers to make new discoveries about cell function, signaling, gene expression, fate decisions, and much more. Techniques for the rapid and accurate enrichment of target cell populations are an area of great interest. Cell sorting techniques fall into two general categories: bulk sorting and single cell sorting. In bulk cell sorting all of the target cells are collected in one sweep, whereas in single cell sorting every cell is individually analyzed. There are multiple methods of bulk cell sorting: filtration, sedimentation, centrifugation, cell culture, and magnetic cell sorting. The main single cell sorting method is flow cytometry. While cell sorting can be very accurate, it is hard to say that a sorted cell population is “pure”. Instead, the collected population is referred to as “enriched”.

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Multiplex immunoassays

Posted on Thu, Dec 08, 2016

Traditional immunoassays such as the enzyme-linked immunosorbent assay (ELISA) are able to measure the presence or absence of only one analyte per reaction. Multiplex immunoassays measure dozens of different analytes in a single reaction. This is particularly beneficial for precious samples, and when only a small volume is collected for analysis. The multiplex immunoassay also saves working time since multiple assays can be completed simultaneously.

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Genomic DNA isolation

Posted on Thu, Nov 24, 2016

In bacteria there are two main types of DNA—genomic and plasmid. Plasmid DNA is unique to bacteria. Eukaryotic cells don't typically have plasmid DNA unless it was put there by transfection for experimental purposes. The most important goal when isolating nucleic acids is to obtain the highest purity genetic material possible. When isolating genomic DNA it is important to remove plasmid DNA and RNA from the sample. Similarly, sometimes an experiment calls for the isolation of plasmid DNA, and the selective removal of genomic DNA is necessary. Also, some commercial RNA isolation kits include gDNA eliminator spin columns to remove genomic DNA from the isolate. 

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Choosing the appropriate DNA extraction protocol

Posted on Thu, Nov 17, 2016

There are three general steps to DNA extraction

  1. celllysis and deactivation of DNAases
  2. Removal of contaminating molecules: proteins, polysaccharides, salts, other nucleic acids
  3. Recovery of DNA
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In-vitro diagnostic IVD coatings for magnetic particles

Posted on Thu, Nov 10, 2016

In-vitro diagnostic assays are used to diagnose infection or disease by specifically targeting a unique surface antigen or DNA sequence. Traditionally it was necessary to increase microbe density by culturing the sample for a few days under strict laboratory conditions. This was an important step toward obtaining enough genetic material for accurate analysis by qPCR.

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