Structural Properties
Conjugated Polymer Nanoparticles (CPNs™) are water-soluble micelles compromising of a Light Emitting Polymer and are around 70-80 nm in size. CPNs™ exhibit luminescence or fluorescence with emission wavelengths from 420 nm to 1130 nm. They are encapsulated within a biocompatible surfactant, increasing the hydrophilicity and allowing them to form micelles. This ‘core-shell’ structure, consisting of the polymer forming the core and the surfactant the surrounding shell, provides a ready base on which to covalently bond functionalising molecules, such streptavidin, antibodies, targeting proteins or nucleic acids.
Stream’s CPNs™ also incorporate iron oxide into their core. This allows CPNs™, and the molecules or cells to which they are attached, to be manipulated using magnets to direct movement and facilitate purification.
The iron oxide can be also be visualised using Magnetic Resonance Imaging (MRI), acting as a contrast reagent.
Biological Properties
CPNs™ are readily conjugated to biomolecules such as antibodies or streptavidin allowing their use in a wide range of molecular biological applications. The intense brightness of the CPNs™ dramatically increases the sensitivity of these applications, with single nanoparticles being detectable in flow cytometry and immunocytochemistry, allowing the study of individual proteins in samples and cells.
The streptavidin and antibodies are covalently conjugated to the CPNs™ via the surfactant’s carboxylic acid groups using N-ethyl-N’-dimethylaminopropyl-carbodiimide (EDC) chemistry. The CPNs™ conjugates can be used in ‘end user’ assays at concentrations matching those of other conjugated fluorophores. Due to differences in assay systems, working dilutions should be determined by titration assay.
Storage
CPNs™ are both thermal and photostable, and can be stored at room temperature. It is not advised to freeze or thaw before use as this diminishes the optical properties. Once conjugated to biological materials, CPNs™ should be stored at 2-6°C. Cell samples or cultures labelled with CPNs™ can be frozen.
Optical Properties
The energy emitted by CPNs™ is dependent on the specific polymer core creating a common platform of labels across the visible and NIR spectrum. At present, we offer CPN™ products in a range of fluorescence emission wavelengths, from 420 nm to 1130 nm. Our CPNs™ can retain their fluorescence and light emission for over 12 months due to their extreme brightness and photostability, and can be stored under ambient temperature and lighting conditions. Furthermore, they retain their properties after use in cells when conjugated with antibodies.