The device, developed by researchers from IdISBa and the Haematology and Haemotherapy Department of Son Espases University Hospital, could facilitate the early diagnosis of serious complications associated with a weakened immune system in patients undergoing chemotherapy, while laying the groundwork for future point-of-care immune monitoring tools.

Researchers from the Innovation in Immunopathogenesis of Infections Group (GTERi) at the Health Research Institute of the Balearic Islands (IdISBa) and the Haematology and Haemotherapy Department of Son Espases University Hospital have developed an innovative paper-based biosensor capable of rapidly, simply, and decentralisedly measuring neutrophil levels in blood, one of the main indicators of a person's immune competence. The findings have been published in Sensors and Actuators B: Chemical, the second most cited journal worldwide in the field of engineering and instrumentation.

Neutrophils are the most abundant white blood cells of the innate immune system and constitute the body's first line of defence against bacterial and fungal infections. When their numbers decline significantly, patients become particularly vulnerable to potentially serious infections. This condition, known as neutropenia, is common among individuals undergoing cancer treatments such as chemotherapy.

The new device, based on a foldable origami-style paper structure and gold nanoparticles functionalised with antibodies, enables the quantification of neutrophils directly from a blood sample in less than 20 minutes, without the need for specialised equipment, laboratory instrumentation, or highly trained personnel.

Rapid diagnosis where it is needed most

Currently, determining neutrophil counts typically requires haematology analysers located in clinical laboratories. This can delay decision-making in situations where every minute matters.

The technology developed by the researchers aims to bring this diagnostic capability closer to the point of care, whether in emergency departments, outpatient clinics, oncology day hospitals, primary care centres, or even home settings and resource-limited regions.

During device validation, the researchers demonstrated that the biosensor was capable of detecting neutrophil concentrations ranging from extremely low levels to normal values. Furthermore, the results showed that other blood components do not interfere with the measurement.

Potential for the management of febrile neutropenia

One area where this technology could have a particularly significant impact is the early diagnosis of febrile neutropenia, one of the most common and dangerous complications in cancer patients receiving immunosuppressive treatments such as chemotherapy.

Febrile neutropenia is a medical emergency that requires prompt evaluation to initiate antibiotic treatment and prevent severe infections. Having a portable tool capable of determining a patient's immune status within minutes could accelerate the identification of high-risk cases and facilitate early intervention.

According to the researchers, the speed of analysis and the lack of complex equipment make this biosensor an especially attractive alternative for scenarios where immediate access to a laboratory is not available.

Beyond cell counting

Although the biosensor is currently a prototype and its validation has focused exclusively on neutrophil quantification, the results have much broader applications. The biosensor preserves the integrity of blood cells and enables the analysis of markers present on their surface, a feature that opens up new possibilities for assessing the functional state of the immune system outside the laboratory environment.

The authors highlight that this strategy lays the foundation for the development of a new generation of rapid, portable, affordable, and user-friendly diagnostic devices capable of monitoring immune responses to infections in real time and directly at the patient's location.

The researchers believe that this advance represents an important step towards more accessible and decentralised healthcare, where information about immune status can be obtained immediately to improve clinical care and health outcomes.

Next steps and clinical application

One of the most frequently asked questions regarding advances of this kind is when they will be translated into clinical practice. The researchers emphasise that the primary objective of this work is to establish the foundations for future developments and that commercial translation depends on multiple factors.

In this regard, the current device is a prototype-a proof of concept-and the team is already working on a version 2.0 that will improve its accuracy and generate new intellectual property, both of which are key steps towards technology transfer. However, before any potential clinical application, diagnostic validation studies through specifically designed clinical trials will be essential, requiring significant funding.

Consequently, although several years of work and compliance with the regulatory framework applicable to medical devices will still be necessary, the researchers continue advancing the development of this technology in order to make its future implementation possible.

Reference: Gonzalo-Jiménez DJ, Rubí P, Vaquer A, Gómez P, Montolio S, Clemente A. Decentralized Quantification of Neutrophils in Whole Blood Using a Rapid Gold Nanoparticle-based Paper Biosensor. Sensors and Actuators B: Chemical. Available online 26 June 2026, Article 140407.

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