ABSTRACT
As the COVID-19 pandemic evolves and new variants emerge, the development of more efficient identification approaches of variants is urgent to prevent continuous outbreaks of SARS-CoV-2. Field-effect transistors (FETs) with two-dimensional (2D) materials are viable platforms for the detection of virus nucleic acids (NAs) but cannot yet provide accurate information on NA variations. Herein, 2D Indium selenide (InSe) FETs were used to identify SARS-CoV-2 variants. The device's mobility and stability were ensured by atomic layer deposition (ALD) of Al2O3. The resulting FETs exhibited sub-fM detection limits ranging from 10(-14) M to 10(-)(8) M. The recognition of single-nucleotide variations was achieved within 15 min to enable the fast and direct identification of two core mutations (L452R, R203M) in Delta genomes (p < .01). Such capability originated from the trap states in oxidized InSe (InSe1-xOx) after ALD, resulting in traps-involved carrier transport responsive to the negative charges of NAs. In sum, the proposed approach might highly provide epidemiological information for timely surveillance of the COVID pandemic.
ABSTRACT
Introduction: Messenger RNA (mRNA) based vaccines (Pfizer/BioNTech and Moderna) have shown to be highly effective at providing immunity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Aims: To study the duration of immunity, evolution of IgG antibody levels and IgG avidity (an index of antibody-antigen binding strength), and differences in immune responses between (mRNA) based vaccines. Methods: We performed a prospective study of 72 subjects without a history of SARS-CoV-2 who received both doses of either the Pfizer (n=55) or Moderna (n=17) mRNA vaccine. Anti-spike protein receptor binding domain (RBD) IgG antibody levels and IgG avidity indices were measured longitudinally using a qualitative finger stick MidaSpot™ rapid test at the point-of-care and a quantitative dry blood spot-based pGOLD™ laboratory test over ∼ 4 months post-vaccination. Results: On average, anti-RBD IgG antibody levels peaked at ∼2 weeks after second vaccination dose and declined thereafter, while antibody avidity increased suggesting antibody maturation (Figure). Moderna vaccine recipients exhibited higher side effect severity, higher peak anti-RBD IgG antibody levels and higher avidity up to the 90 days point, when compared to Pfizer vaccine recipients. Nevertheless, the differences in antibody and avidity levels diminished at ∼ 120 days post-vaccination, in line with the similar efficacy of the two vaccines. A qualitative MidaSpot finger stick rapid test detected 100% anti-SARS-CoV-2 RBD positivity for fully vaccinated subjects in both Pfizer and Moderna cohorts and turning negative greater than 90 days post-vaccination for 9% of subjects in the Pfizer cohort whose quantitative anti-IgG fell below the 25-percentile levels. Conclusions: Longitudinal quantitative measurements of anti-RBD antibody and avidity levels provide insight to immune responses and could aid the assessment of immunity and vaccine effectiveness.