Toshihiro Kasama

[This corrects the article DOI: 10.1016/j.isci.2023.107820.].

We present a rapid and highly sensitive immunoassay platform based on an ultra-thin immuno-wall microfluidic device with an easy-to-perform sequential fluorescence signal increment method. The ultra-thin immuno-wall was fabricated using a special type of water-soluble photopolymer mixed with streptavidin via photolithography. During photolithography, the photopolymer formed a three-dimensional cross-linked structure, and streptavidin was immobilized in the cross-linked structure based on the click chemistry reaction. The immobilized streptavidin was used to immobilize biotin-conjugated antibodies on the cross-linked structure to capture biomarkers, forming immune complexes on the surface, known as an "immuno-wall." A sequential fluorescence signal increment method utilizes two different fluorescence-labeled antibodies with high affinity that were incubated several cycles in the immuno-wall to enhance the fluorescence signal. Moreover, an ultra-thin immuno-wall was developed to reduce the nonspecific binding and increase the signal-to-noise ratio. To evaluate the performance of this immunoassay platform, the spike protein from the SARS-CoV-2 virus was selected as the target biomarker. This immunoassay platform exhibited a limit of detection of 0.01 ng/mL, and the detection time was 30 min, which is comparable to rapid antigen tests. This immunoassay platform demonstrates significant potential for early-phase disease diagnosis.

Lascufloxacin (LSFX) achieves concentrations in epithelial lining fluid (ELF) that are more than 15 times higher than those in the bloodstream, making it a promising candidate for respiratory and otorhinolaryngological infections. These concentrations were replicated using the Hollow-Fiber Infection Model and demonstrated bactericidal efficacy of LSFX against levofloxacin-sensitive and -resistant Streptococcus pneumoniae. The study confirms that LSFX's elevated concentration in ELF plays a significant role in its bactericidal activity.

Due to the inherent characteristics including confinement of molecular diffusion and high surface-to-volume ratio, microfluidic device-based immunoassay has great advantages in cost, speed, sensitivity, and so on, compared with conventional techniques such as microtiter plate-based ELISA, latex agglutination method, and lateral flow immunochromatography. In this paper, we explain the detection of C-reactive protein as a model antigen by using our microfluidic immunoassay device, so-called immuno-pillar device. We describe in detail how we fabricated and used the immuno-pillar devices.