Changchun Institute of Biological Products Co., Ltd.

Mucosal immunity is crucial for preventing the infection and transmission of respiratory viruses. Nasal antibody is inversely correlated with a lower risk of infection with respiratory viruses. However, the current reference standard for nasal antibody assessment is serum-based, mainly consisting of monomeric IgG and IgA. The applicability of serum-derived standards for assessing nasal antibodies, consisting mostly of dimeric or polymeric secretory IgA (sIgA), remains unvalidated. Herein, we first proved that the sera-derived standard was not applicable for assessing nasal antibodies. Using a non-homologous standard as a calibrator introduced systematic error up to 10 times, which did not benefit the understanding of mucosal antibody response. Therefore, we attempted to develop two candidate standards (CS1, CS2) using nasal mucosal lining fluids (NMLFs) collected from SARS-CoV-2 Omicron convalescents or intranasal vaccine recipients, and CS3 using a sIgA monoclonal antibody. CS2 exhibited broad-spectrum binding activity against 12 SARS-CoV-2 strains, including all tested Omicron subvariants. A collaborative study conducted by seven laboratories demonstrated that CS2 improved the harmonization of inter-laboratory variability (pre-standardization geometric coefficients of variance, 14-314%; post-standardization, 3-35%). Using CS2 ensured an accurate assessment of nasal antibodies. Thus, CS2 was established as a national standard for evaluating nasal SARS-CoV-2-specific antibodies (Lot: 300052-202401, 1000 U/mL). Our work provides a benchmark for evaluating mucosal vaccines for SARS-CoV-2 and inspires new avenues for developing new reference standards for other mucosal vaccines.

The field of view (FOV) is a critical parameter for the applications of liquid crystal tunable filters (LCTFs). This work systematically investigates the impact of FOV on the filtering characteristics of the Lyot-type LCTF and establishes a quantitative evaluation method. First, phase retardation model of FOV was constructed to derive formulas for both spectral transmission and wavelength shift. Then, the variation characteristic of filter wavelength with the azimuth angle was analyzed for different FOVs, and the quantified evaluation method of the FOV effect was proposed based on the maximum wavelength shift. In succession, the change rule of maximum wavelength shift with the FOV and filtering wavelength are simulated. Furthermore, the influence of liquid crystal (LC) birefringence on the maximum wavelength shift was analyzed and the results indicate that larger Δ n results in larger effective FOV. The proposed model and evaluation method were validated experimentally. For a single-stage filter, the experimental results show excellent agreement with the simulations. However, for a cascaded LCTF, the measured transmittance curve deviates from that of the simulated significantly, which is caused by the LC cell thickness mismatch in the experiment. It illustrates that the LC cell thickness not only satisfies the demanded phase retardation of all the stages, but also the recursive relation d i  = 2 i-1d1 , which is often overlooked in the LCTF design. All the results confirm that the proposed model and evaluation method can effectively characterize the FOV properties of LCTFs. This work will provide a foundation for designing the LCTFs with large FOV.

Exosomes play a pivotal role in cancer diagnosis and therapy, yet their clinical application faces significant technical challenges. To address this, we developed a sensitive, aptamer-based platform that integrates nucleic acid amplification and a G-quadruplex (G4) with two-signal output for exosome detection. Our approach employs CD63 antibody-conjugated magnetic beads (MBs) for efficient exosome capture and purification. The captured exosomes are then bound by CD63-specific aptamers embedded in rolling circle amplification (RCA) products, forming a sandwich complex with the MBs. The RCA products also contain G4 repeats, enabling two-signal output through interaction with Fe(III)-protoporphyrin IX (Hemin) and N-methylporphyrin-dipropionic acid IX (NMM). The G4-Hemin complex catalyzes the oxidation of 3,3',5,5'-tetramethylbenzidine (TMB), producing a colorimetric signal, while the G4-NMM enhances fluorescence emission. This detection system achieves high sensitivity, with detection ranges of 4.0 × 10³ to 4.0 × 10⁷ particles/mL (colorimetric) and 4.0 × 10² to 4.0 × 10⁶ particles/mL (fluorescence), and low detection limits of 1.78 × 10³ particles/mL (colorimetric) and 96 particles/mL (fluorescence). Demonstrating high performance in complex media (10% exosome-depleted fetal bovine serum, FBS), this biosensor achieves sensitivity comparable to current methods at a low cost ($5.19 per test). This combination of robustness, sensitivity, and affordability makes it a highly promising platform for clinical exosome-based diagnostics.