Automatic ultrasensitive lateral flow immunoassay based on a color-enhanced signal amplification strategy.

Lateral flow immunoassays (LFIAs) are an essential and widely used point-of-care test for medical diagnoses. However, commercial LFIAs still have low sensitivity and specificity. Therefore, we developed an automatic ultrasensitive dual-color enhanced LFIA (DCE-LFIA) by applying an enzyme-induced tyramide signal amplification method to a double-antibody sandwich LFIA for antigen detection. The DCE-LFIA first specifically captured horseradish peroxidase (HRP)-labeled colored microspheres at the Test line, and then deposited a large amount of tyramide-modified signals under the catalytic action of HRP to achieve the color superposition. A limit of detection (LOD) of 3.9 pg/mL and a naked-eye cut-off limit of 7.8 pg/mL were achieved for detecting severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) nucleoprotein. Additionally, in the inactivated virus detections, LOD equivalent to chemiluminescence (0.018 TCID50/mL) was obtained, and it had excellent specificity under the interference of other respiratory viruses. High sensitivity has also been achieved for detection of influenza A, influenza B, cardiac troponin I, and human chorionic gonadotrophin using this DCE-LFIA, suggesting the assay is universally applicable. To ensure the convenience and stability in practical applications, we created an automatic device. It provides a new practical option for point-of-care test immunoassays, especially ultra trace detection and at-home testing.

A nasal spray vaccination device based on Laval nozzle and its experimental test.

In order to realize the application of the nasal spray vaccination in the prevention and protection of respiratory infectious diseases, a nasal spray vaccination device is designed in this paper. The device uses a Laval nozzle structure to generate a high-speed airflow that impinges on the vaccine reagent and forms nebulized particles. Through optimizing of the Laval nozzle structure and testing experiments on spray particle size, spray velocity, spray angle and spray rate, a set of parameters which is applicable to actual nasal spray vaccination is obtained. The experimental results show that when the air source pressure is 2 bar, the spray angle is about 15°, the diameter of the spray particles Dv50 is about 17 µm, the volume fraction of particles with diameter smaller than 10um is about 24%, the spray rate is close to 300 µl/s. The vaccine activity tests demonstrate that under these conditions, not only the biological activity of vaccines is guaranteed, but also the delivery efficiency is well assured.