Development and validation of a bioassay to evaluate binding of adalimumab to cell membrane-anchored TNFα using flow cytometry detection

Highly Responsive Bioassay for Quantification of Glucocorticoids

Measurement of total cortisol levels in serum samples is currently based on immunoassays or liquid chromatography-mass spectrometry (LC-MS/MS). However, measurement of bioavailable cortisol is laborious, unreliable, and inconvenient for the patient. Therefore, a new versatile assay with the ability to measure both total and bioavailable cortisol from serum represents an important supplement to the current methods. We have generated a cell-based glucocorticoid reporter assay (HEK293F-GRE). The assay was validated for cell line stability, accuracy by dilution, precision, repeatability, reproducibility, and specificity. Additionally, the assay was tested for measuring both total and bioavailable cortisol in serum. The assay showed linearity at five dilution levels with R2 = 0.98 and an accuracy between 0.8 and 1.2. Precision (CV < 20%) was validated down to 3-6 nM dexamethasone, and estimation of the total cortisol concentration was comparable to cortisol immunoassay and LC-MS/MS in most serum samples. Moreover, the assay estimated the bioavailable cortisol fraction in serum samples to a level that agreed with the literature. The HEK293F-GRE assay holds the potential to be a complementary method for estimating cortisol in clinical practice. The ability to quantify bioavailable cortisol directly from serum samples is alluring and provides an opportunity for monitored and personal dose regimens of exogenous glucocorticoids.

Flow cytometry: A powerful analytical technique for characterizing the biological function of biotherapeutics and biosimilars

Biotherapeutics are complex molecules with therapeutic activity produced through biotechnology and/or genetic engineering. These medicines have clinical applications in diagnostic procedures and therapies for many disorders, including cancer, autoimmunity, and chronic degenerative diseases. Most biotherapeutics are expensive and sometimes unaffordable for low-income patients suffering from cancer or chronic illness. Biosimilars emerged in the 2000 s after patents of many innovative biotherapeutic products expired. The Biosimilar market is growing fast and demands reliable technologies for analyzing the physicochemical properties and bioactivity of products. A big challenge for biosimilar development is to prove comparable bioactivity, safety, efficacy, and toxicity profile as the innovator product. Bioactivity assessment can utilize different analytical techniques such as ELISA, flow cytometry, and surface plasmon resonance. Flow cytometry is a versatile analytical tool that can be used for the development of quantitative, reproducible, and accurate protocols suitable for routine evaluation of bioactivity in-vitro. Nevertheless, flow cytometry has been very scarcely used in comparability evaluation between biosimilar versus an originator product. Here, we review potential applications of flow cytometry to carry out functional bioassays of biotherapeutics or biosimilars.

Bridging the Gap between Digital Assays and Point-of-Care Testing: Automated, Low Cost, and Ultrasensitive Detection of Thyroid Stimulating Hormone

Medical diagnostics is moving toward disease-related target detection at very low concentrations because of the (1) quest for early-stage diagnosis, at a point where only limited target amounts are present, (2) trend toward minimally invasive sample extraction, yielding samples containing low concentrations of target, and (3) need for straightforward sample collection, usually resulting in limited volume collected. Hence, diagnostic tools allowing ultrasensitive target detection at the point-of-care (POC) are crucial for simplified and timely diagnosis of many illnesses. Therefore, we developed an innovative, fully integrated, semi-automated, and economically viable platform based on (1) digital microfluidics (DMF), enabling automated manipulation and analysis of very low sample volumes and (2) low-cost disposable DMF chips with microwell arrays, fabricated via roll-to-roll processes and allowing digital target counting. Thyroid stimulating hormone detection was chosen as a relevant application to show the potential of the system. The assay buffer was selected using design of experiments, and the assay was optimized in terms of reagent concentration and incubation time toward maximum sensitivity. The hydrophobic-in-hydrophobic microwells showed an unparalleled seeding efficiency of 97.6% ± 0.6%. A calculated LOD of 0.0013 μIU/mL was obtained, showing the great potential of the platform, especially taking into account the very low sample volume analyzed (1.1 μL). Although validation (in biological matrix) and industrialization (full automation) steps still need to be taken, it is clear that the combination of DMF, low-cost DMF chips, and digital analyte counting in microwell arrays enables the implementation of ultrasensitive and reliable target detection at the POC.