Background and Aims The safety and antibody responses of coronavirus disease 2019 (COVID‐19) vaccination in patients with chronic hepatitis B (CHB) virus infection is still unclear, and exploration in safety and antibody responses of COVID‐19 vaccination in CHB patients is significant in clinical practice. Methods 362 adult CHB patients and 87 healthy controls at an interval of at least 21 days after a full‐course vaccination (21–105 days) were enrolled. Adverse events (AEs) were collected by questionnaire. The antibody profiles at 1, 2 and 3 months were elucidated by determination of anti‐spike IgG, anti‐receptor‐binding domain (RBD) IgG, and RBD‐angiotensin‐converting enzyme 2 blocking antibody. SARS‐CoV‐2 specific B cells were also analysed. Results All AEs were mild and self‐limiting, and the incidence was similar between CHB patients and controls. Seropositivity rates of three antibodies were similar between CHB patients and healthy controls at 1, 2 and 3 months, but CHB patients had lower titers of three antibodies at 1 month. Compared to healthy controls, HBeAg‐positive CHB patients had higher titers of three antibodies at 3 months (all P < .05) and a slower decline in antibody titers. Frequency of RBD‐specific B cells was positively correlated with titers of anti‐RBD IgG (OR = 1.067, P = .004), while liver cirrhosis, antiviral treatment, levels of HBV DNA, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and total bilirubin (TB) were not correlated with titers of anti‐RBD IgG. Conclusions Inactivated COVID‐19 vaccines were well tolerated, and induced effective antibody response against SARS‐CoV‐2 in CHB patients.

Exosomes as nanosized vesicles have been recognized as potential noninvasive biomarkers for early cancer diagnosis. Herein, we presented a sensitive multicolor visual method for exosome detection based on enzyme-induced silver deposition on gold nanorods (Au NRs). To achieve highly sensitive determination of exosomes, hybridization chain reaction (HCR) was employed to introduce more alkaline phosphatase (ALP) for signal amplification. First, exosomes were captured by magnetic bead-labeled CD63 aptamer, and, then, cholesterol-modified DNA probes were spontaneously inserted into the exosomal lipid membrane. The ends of the DNA probes act as the initiator to trigger the HCR for signal amplification. Finally, with the help of HCR, increased sites led to enhanced ALP loading and thus boosted the ascorbic acid generation. Silver ions were reduced by ascorbic acid, and silver shells were formed on Au NRs, giving rise to the blue shift of the longitudinal localized surface plasmon resonance peak. Correspondingly, the concentration of exosomes can be obviously distinguished with naked eyes via the vivid color variation. Due to the dual signal amplification of HCR and metallization of Au NRs, highly sensitive detection for exosomes were realized with detection limits as low as 1.6 × 102 particles/μL by UV–vis spectroscopy and 9 × 103 particles/μL by naked eyes. Compared to the reported colorimetric methods for exosome quantification, visualization based on plentiful color tonalities is the most captivating merit of our approach, and HCR-induced signal amplification highlights the virtue of the strategy. The applicability of the method was validated by the analysis of clinical samples.

Exosomes involved in tumor-specific processes display excellent potential in the early diagnosis of cancer. Herein, a highly sensitive plasmonic colorimetric biosensor was proposed for exosome quantification. The sensing strategy mainly includes two steps: exosome-triggered competitive reaction and etching of gold nanobipyramid@MnO2 nanosheet nanostructures (Au NBP@MnO2 NSs). A competitive reaction between exosomes and placeholder chains induced by exosomes can translate the signal of exosomes into the amount of alkaline phosphatase, which simplifies the experimental process and amplifies the signal. The etching of Au NBP@MnO2 NSs by ascorbic acid generated from the hydrolysis of l-ascorbic acid 2-phosphate by alkaline phosphatase changes the refractive index of Au NBPs, accompanied by the blue shift of the longitudinal localized surface plasmon resonance peak. Profiting from the signal amplification of the competitive reaction and superior refractive index sensitivity of colorimetric substrates, this protocol exhibits high sensitivity toward exosomes within 8.5 × 102 to 8.5 × 104 particles μL–1, along with a detection limit of 1.35 × 102 particles μL–1, which is more sensitive than previously reported colorimetric methods. In addition, a sensitive multicolor visual detection of exosomes was realized by adjusting the aspect ratio of Au NBPs. It is worth mentioning that the Au NBP@MnO2 NSs was synthesized through in situ growth of MnO2 nanosheets on Au NBPs, and the attractive optical properties and ease of etching make Au NBP@MnO2 NSs promising candidates for plasmonic detection.

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