Quantum dots (QDs) are tiny particles of a semiconducting material with diameters in the range of 2-10 nanometers (10-50 atoms). They were first discovered in 1980, but found an application in medicine only in recent years. Quantum dots display unique optical properties, combining high brightness and several distinctive colours. These features make quantum dots particularly suited to be used in sensing and imaging. More information on quantum dots can be found in our Learning Centre.
The critical part of Lateral Flow Assays (LFAs) is the conjugation chemistry between a label and a disease-specific antibody, which provides the source of sensitivity. The existing and most widely used label is colloidal gold, however a high concentration of gold-antibody conjugates is required for effective testing. As a consequence, colloidal gold-based tests present two main disadvantages:
- Large amounts of antibodies are required, which translate to higher cost to produce the test kits;
- It cannot detect early stage viral infections due to low pathogen load, which translate into poor clinical sensitivity.
Radetec Diagnostics developed a new way to produce highly-fluorescent quantum dots stable in buffers, which can be linked to several biologically-active molecules (e.g. antibodies). These quantum dots have successfully employed in our rapid tests for Sexually Transmitted Infections and COVID-19.
Radetec Diagnostics utilises a world-first technique, which optimises the performance of fluorescence particles, quantum dots (QDs), combined with conventional lateral flow assay (LFA) to produce a vastly more sensitive test (10-100 times sensitivity compared to existing gold nanoparticle technology). Leverage with the LFA existing advantages of faster (results within 10mins) and inexpensive (reduce existing costs by upwards of 50%), Radetec can make world leading test kits for the diagnosis of STIs.
QDs-based tests effectively address these two limitations. QDs generate very bright fluorescence (brighter than other fluorescence molecules), meaning that a lower amount of QD-antibody is necessary to generate a signal. This high brightness also allows the detection of lower concentration of pathogens, enabling early diagnosis and treatment, with substantial healthcare cost savings.
The conjugation between QDs and antibodies presents the biggest hurdle of their application with LFA. A major challenge is that every antibody is different, therefore it is necessary to establish different reaction conditions for each antibody, resulting in high costs for the development of a test.
Our technology works by replacing the current colloidal gold with our QDs, which allows for the reading of a fluorescence signal in the presence of pathogens. Fluorescence-based detection is extremely sensitive, that allows the detection of just few pathogens in the sample. Further, a fluorescence-based detection method offers a wider dynamic range than colloidal gold, and provides the possibility of quantitative detection, which allows the clinician to estimate the stage of an infection, hence providing more informed treatment decision-making on the spot, leading to improved economic and social outcomes.
Radetec Diagnostic’s patented technology enables to:
- Retain the antibody activity when bound to a quantum dot nanoparticle – a process that often compromises the antibody through irreversible chemical or structural modification.
- Achieve optimal control over the surface chemistry of nanoparticles and their bioconjugation reaction, with low batch-to-batch assay reproducibility.
This increased activity then leads to improved analytical limit of detection and quantitative results when these antibody-conjugated quantum dots are used in a diagnostic tests. These characteristics make Radetec’s quantum dots especially suited for the development of rapid tests with high sensitivity.