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Enhancing Efficiency and Economics in Process Development and Manufacturing of Biotherapeutics Protein Quantitation of 70 Complex Samples Octet Systems Sample and instrument prep 30 min Data analysis 10 min 60 min total assay time 40 min operator hands-on time Sample run time 20 min HPLC Sample and instrument prep 4 hr Sample injection and run time 18 hr Data analysis 50 min 23 hr total assay time 5 hr operator hands-on time ELISA Bind capture antigen to plate Overnight (16 hr) Sample and instrument prep 1 hr Sample run time 4 hr Data analysis 30 min 21.5 hr total assay time 5.5 hr operator hands-on time Figure 2: Comparison of protein quantitation in complex matrices using Octet systems and alternative methods. ADVANTAGES OVER ELISA AND HPLC The principles of concentration measurement with an Octet system are similar to established immunoassays such as ELISA and HPLC. However, protein quantitation protocols on the Octet platform provide several advantages. The Octet platform monitors binding of proteins from solution to a biosensor surface in real time, without need for labels or other detection reagents. This real-time monitoring of binding interactions enables clear discrimination between specific and non-specific binding signals, which can shorten assay development times dramatically. Octet assays are also much faster: quantitation of a 96-well plate requires 15 – 30 minutes, or 60 minutes for a 384-well plate, depending on the instrument model. Figure 2 provides a comparison of analysis times. Analysis of 70 samples on an Octet RED96 system requires as little as 55 minutes including operator hands-on time, whereas ELISA or HPLC assays require at least 22 hours including several hours of analyst involvement. Samples run on Octet systems are also recoverable, so that researchers may save and reuse precious samples for other experiments. In addition, Octet assays are not affected by absorption interferences in colored samples or by light scattering with turbid samples, enabling measurement of analyte concentration in crude matrices such as cell culture supernatant, cell lysate and serum. Octet concentration assays are complemented by the platform’s ability to measure functional activity. For example, titer for a monoclonal antibody (mAb) can be determined using biosensors coated with Protein A, while the functional activity of the mAb can be assessed in a second assay step involving binding to its specific antigen. In contrast, HPLC and A280 spectroscopy can determine only the total protein concentration of a sample, and separate assays must be used to measure biological activity. BIO-LAYER INTERFEROMETRY TECHNOLOGY (BLI) BLI technology monitors and analyzes the interference pattern generated from the reflection of white light from two different surfaces: a layer of immobilized protein on the biosensor tip and an internal reference layer (Figure 3). Any increase or decrease in the number of binding molecules on the biosensor surface produces a change in optical thickness that causes a shift in the interference 2
Application Note 11 Incident white light BLI signal processing Biocompatible surface Relative Intensity 1.0 0.8 0.6 0.4 Δ λ Bound molecule 0.2 Unbound molecules have no effect Wavelength (nm) Figure 3: Bio-Layer Interferometry is an optical analytical technique that analyzes the interference pattern of white light reflected from two surfaces. Changes in the number of molecules bound to the biosensor causes a shift in the interference pattern that is measured in real time. Biosensors Standard Reference Unknown Binding (nm) 0 T ime (sec) 120 Binding Rate Concentration Figure 4: A typical quantitation assay setup. Biosensors dip into standards run in duplicate to obtain binding (nm shift) vs. time (sec) curves. The initial slope of the interaction is used to create the standard curve of the binding rate vs. concentration. The concentration of an unknown sample is then interpolated from the standard curve. pattern. Unbound molecules in complex matrices and changes in the refractive index of the surrounding medium have minimal effect on the interference pattern. BLI technology simplifies protein quantitation by enabling specific measurement in complex samples. The one-step Dip and Read assay format uses native proteins, without need for labels or secondary reagents. CONCENTRATION MEASUREMENT Accurate determination of biologically relevant protein concentrations is essential to several areas in the biopharmaceutical industry including research, bioprocessing, quality control and manufacturing. The Octet platform uses a simple Dip and Read approach for rapid analysis of samples in 96 and 384-well microplate formats. The concentration of the target protein or antibody in a sample is determined via a direct binding or sandwich assay. Biosensors coated with a capture molecule, called the ligand, are dipped into solutions containing the analyte in a highly parallel, automated method to measure binding interactions. In a typical quantitation assay, a standard curve is generated using known amounts of the protein analyte, and unknown sample concentrations are interpolated from the standard curve (Figure 4). Concentration can be 3
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