Last May I was in Shanghai, invited by Merck Millipore to contribute to the Forum they organized. SEPMAG was one of the sponsors and I was one of the speakers. In a previous post I have reviewed the talks about new trends on immunomagnetic assays, coupling of biomarkers and the use of Biomagnetic Separation in CLIA IVD-kits Manufacture.
Today I’ll close my revision of the Forum with a short summary of the contributions about lateral flow and immunoturbidimetry, as well as the discussion about readers and microfluidics.
Dr. Sergi Gassó, General Director Pragmatic Diagnostics, explain how latex- enhanced immunoturbidimetry (L-IT) is used for the detection of a wide range of proteins and small molecules. He describes L-IT is a quick test (5-15 min) that uniquely needs mixing the sample and the immunoreagent, and can be semi-automated or automated conventional Clinical Chemistry analyzers. This tests can be competitive or immunometric, being the first often used for small molecules detection. Dr. Gassó described L-IT development: the choice of the latex particle size, depending on the wavelength, and how the capture molecule can be coated -passive adsorption (hydrophobic interactions) or covalent binding-.
The major challenges were described, as the non-specific binding and the prozone effect. The first can be mitigated by addition of detergents, blocking agents or optimization of the coating procedures. The second depends on the amount of sample and capture molecule used. The speaker concluded that L-IT is a very convenient technology for small molecules and proteins where the required analytical sensitivity is within the achievable range.
On lateral flow, Dr. Jeff Bauer, President of Kestrel BioSciences, reviewed lateral flow assays. He pointed the colloidal gold disavantages: poor reproducibility and poor sensitivity dues the variation of gold particle lot to lot production and conjugation. He explain the new trend on quantitative lateral flow assay in POCT: the use of latex particles colored or fluorescent and reader systems, coupled with advanced device design. This approach yields more sensitive, quantitative tests. High fluorescent microparticles could yield higher sensitivities, up to 100 folds coloidal gold, achieving pg/ml levels. He emphasizes than Europium label microspheres have the advantage of separating he excitation and emission spectra by a wide Stokes shift. This factor allows the use of an inexpensive fluorescent reader that requires a low-cost UV-LDE for the excitation energy and a photodiode to record the fluorescent signal from the test strip.
On the same subject, Dr. Matthias Volk, Executive Director and General Manager, Suzhou Sensogen Biotech, also discusses the new trends and techniques in lateral flow rapid tests to increase the sensitivity and lower CV values. He argues that ideal rapid tests should provide short time (5 to 10 min) with the same sensitivity as routine lab tests (ELISA; CLIA; FLIA) with CV below 10% and for COG of less than US$0.50/tests, with results potentially quantitative. The reach this goal, the first choice should be the right binding agents. Herby mouse monoclonal –the most common selection- is not the best. Sheep monoclonal Ab and other might be better. The reduction of CV values is also critical.
Dried particle bound are often not released homogenously. Proper choice of components and pre-treatment is crucial. Kinetic optimization is often forgotten, as the labelled particles diffuse slower and reduce sensitivity in given time frames. The classical gold/latex have limitation in sensitivity that overcome in given time by the uses of new readers/interpretation cards but have their limit, even with innovative silver enhancing. New combinations of fluorescence with visual cards can be a new way for more sensitivity visual and reader based analysis.
The new approaches for manufacturing Paper based microfluidics as next generation of lateral flow tests were exposed by Dr. Xin Yang, from the Institute for Advanced materials NJTech. He emphasizes the potential role of high-resolution inkjet printing. High resolution fluidic pathways defined in nitrocellulose membranes through the printing of PDMS as hydrophobic barriers Channels of the ordered of 100 micrometers can be defined, benefiting for improved device CV’s. As well as microfluidic channels it is also possible to inkjet antibodies, reagents and even electronic sensic materials in a highly integrated and scalable way.
Dr. Wang Long, R&D Manager of Beijing COX Biotech, reviewed the development of the Quantitative Lateral Flow Immunoassay Based on Fluorescent Bead, including POCT and POL, the second is about how to develop the quantitative lateral flow immunoassays based on fluorescent beads, including how to choose a suitable method as corporate clients, how to conjugate the fluorescent bead to IgG, and the several example of problems or troubleshooting occurred in their R&D process.
Another vision of immunoassay design and development was the exposed by Dr. He Jianwen, (DIASORIN). He argued that even if immunoassays are simple in principle, they are complex in business, as they require multiple choices of technologies, system, and applications. Developing immunoassays is a systematic project across functions: finding key raw materials, define reagent formulation, and optimize the process are the key steps. The feasibility is the critical phase to assay development, in which solid phase of particle is the core of the assay technology. Right assay design and process are the keys to success.
Luo Haifeng, R&D Manager of Beijing Hotgen Biotech described the Upconverting Phosphor Technology in the Development of Quantitative Rapid Test. Upconversion is a type of nonlinear process, capable of converting lower energy light into a higher energy emission, however normal fluorescent.
Another group of talks was centered on readers for quantitative lateral flow assays. Dr. Cornelia Haenel (QIAGEN) exposed the benefits and advantages of their Lateral flow reader, as also did Dr. Kevin Jones (MEDMIRA) with their own RVF technology. This last emphasizes the capability of producing multiplexed assays, a subject also developped by Dr. Grace Yuan (Merck Chemicals).
As general impression, the two days had a dense, very interesting program. The organizers facilitate a lot of breaks, that helped to interact public and speaker and I hope it would spark new collaborations. Make sure to check the first one of these posts about the forum.