Structure-guided development of an electrochemical aptasensor for Salmonella Typhi HlyE antigen detection using in silico and experimental approaches

Why a Faster Typhoid Test Matters

Typhoid fever still sickens millions of people every year, especially in places without reliable clean water or strong laboratory services. Doctors currently rely on blood cultures that take days and need trained staff and special equipment. This paper describes a new kind of rapid blood test, built on a tiny electronic sensor and a strand of designer DNA, that aims to bring accurate typhoid diagnosis to simple clinics and even rural settings.

A New Target on a Dangerous Bacterium

Typhoid fever is caused by the bacterium Salmonella Typhi. Instead of looking for the whole germ or for the body’s antibodies, the researchers focused on a single protein that the bacterium makes, called HlyE. This protein acts as a toxin and is a promising sign that the true typhoid germ is present. Many existing quick tests look for antibodies, which can be thrown off by other infections. By hunting directly for a key bacterial protein in blood, the new approach aims to deliver more specific answers about who really has typhoid.

Harnessing Designer DNA as a Sensing Tool

The heart of the new test is an aptamer, a short strand of DNA carefully selected to stick tightly and selectively to the HlyE protein. The team had previously isolated several candidate aptamers, and here they zeroed in on one called AptHlyE97. Using computer models and solution experiments, they examined how this DNA strand folds into a three-dimensional shape and how it wraps around the HlyE protein. Their simulations showed that AptHlyE97 grips HlyE more strongly than the other candidates and that its two ends remain free, making it easier to attach to a solid surface without disturbing the binding action.

Building a Tiny Electronic Test Strip

To turn this molecular handshake into a practical test, the researchers built an electrochemical sensor on a disposable gold electrode, similar in spirit to the strips used in home blood sugar meters. They fastened many copies of AptHlyE97 upright on the gold surface using a sulfur-based linker and then filled the remaining bare spots with a small blocking molecule so that stray proteins would not stick. When a blood sample containing the HlyE protein touches the strip, the protein binds to the DNA strands and slightly insulates the surface. This changes the electrical signal measured when harmless probe chemicals shuttle electrons to and from the electrode.

Putting the Sensor to the Test

The team carefully tuned how much aptamer to attach and then measured how the electrical signal changed as they added increasing amounts of purified HlyE protein. The sensor showed a clear, nearly straight-line response over a wide range of concentrations, and it could detect extremely small amounts of the protein—down to a fraction of a billionth of a gram per milliliter of solution. They then challenged the sensor with mixtures from different bacteria closely related to Salmonella Typhi. Only samples from the true typhoid bacterium produced a large signal drop, showing that the aptamer-coated strip can tell dangerous cousins apart.

From Laboratory Bench to Real Patients

To see whether this idea might work in real-world care, the researchers tested serum from patients whose typhoid status had already been confirmed by standard blood culture, as well as from healthy people and patients with other infections. In this small group, the sensor correctly identified every typhoid patient and misclassified only one non-typhoid case, corresponding to perfect sensitivity and good specificity. A standard statistical analysis of test performance showed that the sensor was very effective at separating true cases from non-cases, even though the study was still at an early, small-scale stage.

What This Could Mean for Everyday Care

In simple terms, the study shows that a tiny strip coated with a smart piece of DNA can spot a telltale typhoid protein in blood with high accuracy. Although more work is needed to fine-tune the test and validate it in larger, diverse groups of patients, this approach could eventually offer a quick, low-cost tool to diagnose typhoid at the bedside or in community clinics without full laboratories. Faster, more reliable detection would help doctors start the right treatment sooner and could play a meaningful role in controlling typhoid outbreaks in the places that need help most.

Citation: Ahmad Najib, M., Winter, A., Mustaffa, K.M.F. et al. Structure-guided development of an electrochemical aptasensor for Salmonella Typhi HlyE antigen detection using in silico and experimental approaches. Sci Rep 16, 11128 (2026). https://doi.org/10.1038/s41598-026-38666-6

Keywords: typhoid fever, electrochemical biosensor, aptamer, point-of-care testing, Salmonella Typhi