Abstract
Diphtheria is a vaccine-preventable disease, yet immunization can wane over time to non-protective levels. We have developed a low-cost, miniaturized electroanalytical biosensor to quantify anti-diphtheria toxin (DTx) immunoglobulin G (anti-DTx IgG) antibody to minimize the risk for localized outbreaks. Two epitopes specific to DTx and recognized by antibodies generated post-vaccination were selected to create a bi-epitope peptide, biEP, by synthesizing the epitopes in tandem. The biEP peptide was conjugated to the surface of a pencil-lead electrode (PLE) integrated into a portable electrode holder. Captured anti-DTx IgG was measured by square wave voltammetry from the generation of hydroquinone (HQ) from the resulting immunocomplex. The performance of the biEP reagent presented high selectivity and specificity for DTx. Under the optimized working conditions, a logarithmic calibration curve showed good linearity over the concentration range of 10−5–10−1 IU mL−1 and achieved a limit of detection of 5 × 10−6 IU mL−1. The final device proved suitable for interrogating the immunity level against DTx in actual serum samples. Results showed good agreement with those obtained from a commercial enzyme-linked immunosorbent assay. In addition, the flexibility for conjugating other capture molecules to PLEs suggests that this technology could be easily adapted to the diagnoses of other pathogens.
Highlights
IntroductionThe respiratory and cutaneous disease diphtheria (DIPH) is caused by toxins released from the bacteria Corynebacterium diphtheriae and C. ulcerans during pharynx infections, tonsils, or skin
An electrochemical immunosensor was developed using graphite rods in pencil lead refills bound with a peptide consisting of two epitopes of diphtheria toxin (DTx) linked in tandem by two glycines
A portable electroanalytical biosensor to assist in controlling diphtheria vaccination programs by accurately determining anti-DTx anti-diphtheria toxin immunoglobulin (IgG) titers in serum is described
Summary
The respiratory and cutaneous disease diphtheria (DIPH) is caused by toxins released from the bacteria Corynebacterium diphtheriae and C. ulcerans during pharynx infections, tonsils, or skin. DIPH is a vaccine-preventable disease with the efficacy of the toxoidbased vaccine varying between 54–87%. 80–85% of the population needs to be vaccinated [3]. A major issue is that the immunity induced by the vaccines can wane over time, and any drop in the protection levels in a population could allow for an opportunistic return of this transmissible disease leading to an outbreak [1,4]. Previous studies suggest that 49% of the French adult population presents an antibody titer below protective levels [4]. To maintain the antibody titer at a protective level, booster shots are required.
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