Nano Discovery Inc.

NanoDLSay™: Nanoparticle-Enabled Dynamic Light Scattering Assay



1. Introduction

2. What is dynamic light scattering?

3. Why use gold nanoparticles (AuNPs)?

4. Broad applications of NanoDLSay™ and superior analytical performance

Please visit APPLICATION NOTES page for more technical details.

1. Introduction

NanoDLSay™ is an analytical technique for chemical and biological detection and analysis based on the size change of gold nanoparticle (AuNP) probes upon binding with target analytes. Biomolecules such as proteins and DNAs are macromolecules. Their sizes (Diameter, D) typically fall in the range of a few to tens of nanometers. When target analyte molecules or species are bound to a gold nanoparticle probe, the nanoparticle size will increase. By monitoring the gold nanoparticle size change using dynamic light scattering (DLS), target analytes can be detected and quantified. NanoDLSay™ detection is not limited to large biomolecules and species. In a more general format, assays can be designed to introduce gold nanoparticle cluster formation upon binding with the target analytes. For example, gold nanoparticles conjugated with metal-chelating ligands can cluster together upon binding with the specific metal ions. The nanoparticle cluster formation leads to an increase of the average particle size of the assay solution. Using one of the two assay formats, individual particle size increase or nanoparticle cluster formation, NanoDLSay™ can be applied for the detection and analysis of an unlimited range of chemical and biological molecular targets and species, including proteins, DNAs, RNAs, carbohydrates, viruses, small chemicals and toxic metal ions with superior analytical performance.  The most unique thing about NanoDLSay™ is that, it not only can detect the target analytes, but also reveal their "size" information. This capability is particularly useful for protein detection and analysis. For protein-related applications, please visit PROTEIN RESEARCH for more details.

2. What is dynamic light scattering?

Dynamic light scattering (DLS) is an analytical technique for particle size measurement. It is particularly useful for measuring particle size in the nanometer range. DLS monitors the dynamic scattering light intensity fluctuation due to the Brownian motion of particles in the sample solution. From the  light intensity fluctuation pattern, a correlation function is constructed. Using the Stokes-Einstein equation and the translational diffusion coefficient determined from the correlation function, the hydrodynamic diameter of a particle solution can be obtained. Currently DLS can measure particle sizes in the range of 1 nm to 5-6 microns with excellent precision and reproducibility. For example, when measuring a mono-dispersed gold nanoparticle solution with an average diameter of 100 nm, the measurement error of a good DLS instrument can be as little as ± 2 nm (CV% < 2%). DLS has been used for more than 40 years mainly as a material characterization tool.

In the past ten years, DLS technique and products have evolved dramatically in both hardware and software. Nowadays, DLS is as easy to use as a simple UV-Visible spectrophotomer. No special environment is required to house the instrument and no special training is needed to learn how to operate a DLS instrument. The hardware of DLS instruments is maintenance-free.

 

3. Why use gold nanoparticles (AuNPs)?

Gold nanoparticles scatter light intensely in the visible light region.  They appear as beautiful super-shining stars under a dark-field optical microscope. This property makes gold nanoparticles an excellent optical probe to enhance light scattering-based detection techniques. In order to detect a specific molecule or a target from real samples, the optical signal from the probe must be substantially stronger than the sample matrix to avoid matrix interference. Many sample matrices such as blood and urine also scatter light intensely. The exceptionally strong light scattering intensity of gold nanoparticles makes them easily detectable by DLS even in the most challenging sample matrices. As a result of using gold nanopartices, NanoDLSay™ can be used for a wide variety of sample analysis, such as cell extracts, tissue products and blood serum without any special sample preparation and treatment.

4. Broad applications of NanoDLSay™ and superior analytical performance

NanoDLSay™ is not a technique that is limited to certain type of target analytes. As stated in the introduction part, using one of the assay formats, i.e., individual nanoparticle size increase, or nanoparticle cluster formation, NanoDLSay™ can be applied for the detection and analysis of target analytes ranging from large biomacromolecules and species such as proteins, DNAs, aggregate particles, viruses, to small chemical molecules and even small ions. All these applications have been demonstrated in the published literature. NanoDLSay™ not only can do what other existing analytical techniques can do with numerous advantages, it can reveal new molecular information and mechanisms that cannot be or have not been observed by any other existing techniques. NanoDLSay™ is a new tool that will allow the researchers to go much further and beyond. 

Analytical Performance Data

Notes: (1) ng-nanogram; fg-femtogram; fM-femtomolar; pM-picomolar; nM-nanomolar; ppb-parts per billion; ppt-parts per trillion; TCID₅₀-50% tissue culture infective dose. (2) All data were taken from published papers. Refer to the published LITERATURE for more information.