Iongels
are soft ionic conducting materials, usually composed of
polymer networks swollen with ionic liquids (ILs), which are being
investigated for applications ranging from energy to bioelectronics.
The employment of iongels in bioelectronic devices such as bioelectrodes
or body sensors has been limited by the lack of biocompatibility of
the ILs and/or polymer matrices. In this work, we present iongels
prepared from solely biocompatible materials: (i) a biobased polymer
network containing tannic acid as a cross-linker in a gelatin matrix
and (ii) three different biocompatible cholinium carboxylate ionic
liquids. The resulting iongels are flexible and elastic with Young‘s
modulus between 11.3 and 28.9 kPa. The morphology of the iongels is
based on a dual polymer network system formed by both chemical bonding
due to the reaction of the gelatin’s amines with the polyphenol
units and physical interactions between the tannic acid and the gelatin.
These biocompatible iongels presented high ionic conductivity values,
from 0.003 and up to 0.015 S·cm–1 at room temperature.
Furthermore, they showed excellent performance as a conducting gel
in electrodes for electromyography and electrocardiogram recording
as well as muscle stimulation.
Serology assays are essential tools to mitigate the effect of COVID-19, help to identify previous SARS-CoV-2 infections or vaccination, and provide data for surveillance and epidemiologic studies. In this study, we report the production and purification process of the receptor-binding domain (RBD) of SARS-CoV-2 in HEK293 cells, which allowed the design, optimization, and validation of an indirect ELISA (iELISA) for the detection of human anti-RBD antibodies. To find the optimal conditions of this iELISA, a multivariate strategy was performed throughout design of experiments (DoE) and response surface methodology (RSM), one of the main tools of quality by design (QbD) approach. The adoption of this strategy helped to reduce the time and cost during the method development stage and to define an optimum condition within the analyzed design region. The assay was then validated, exhibiting a sensitivity of 94.24 (86.01–98.42%; 95% CI) and a specificity of 95.96% (89.98–98.89%; 95% CI). Besides, the degree of agreement between quality results assessed using kappa’s value was 0.92. Hence, this iELISA represents a high-throughput technique, simple to perform, reliable, and feasible to be scaled up to satisfy the current demands. Since RBD is proposed as the coating antigen, the intended use of this iELISA is not only the detection of previous exposure to the virus, but also the possibility of detecting protective immunity.
Key points
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RBD was produced in 1-L bioreactor and highly purified.
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An iELISA assay was optimized applying QbD concepts.
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The validation procedure demonstrated that this iELISA is accurate and precise.
Graphical Abstract
Supplementary Information
The online version contains supplementary material available at 10.1007/s00253-022-12254-w.
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