Rocio Arreguin-Campos

Bacterial endospores are a major challenge in food safety due to their high resistance and potential to cause spoilage and foodborne illness. Current detection methods can be labor-intensive and require specialized instrumentation. A low-cost, label-free thermal sensing platform for indirect detection of Bacillus cereus endospores using molecularly imprinted polymers (MIPs) targeting dipicolinic acid (DPA), a spore biomarker, was developed. The MIPs were synthesized by free-radical bulk polymerization, characterized by rebinding assays, and evaluated using the Heat Transfer Method (HTM). At 100 μM DPA, the MIPs exhibited an imprinting factor (IF) of 2.62 ± 0.18 (n = 3), demonstrating preferential DPA binding. Sensor performance was evaluated using aqueous DPA, structural analogues, and a complex food matrix. HTM measurements produced concentration-dependent responses, with limits of detection of 0.20 ± 0.15 μM in aqueous DPA solutions and 0.060 ± 0.0098 μM in unpretreated, spiked ultrahigh-temperature (UHT) milk. Terbium(III) fluorescence independently supported DPA retention by the MIPs. Real-time assays with germinated B. cereus suspensions at 105 colony-forming units (CFU) mL–1 enabled proof-of-concept monitoring of biologically released DPA under laboratory conditions. These findings highlight the potential of combining DPA-imprinted polymers with HTM for real-time and label-free indirect endospore detection.

Timely identification of pathogens within the food production chain is crucial to prevent spoilage and reduce the substantial economic burden associated with crop loss. Botrytis cinerea is the causative agent of gray mold disease, which affects important crops such as tomatoes. In this study, we introduce a sensing platform for real-time monitoring of this fungus. The sensor consists of a polymeric receptor imprinted with the physical and chemical characteristics of the fungus’s spores, enabling identification. Detection is achieved using a thermal transducer, which offers a reproducible concentration-dependent signal toward the analyte. The sensor was tested for specificity with other spores (Ampelomyces quisqualis, Fusarium oxysporum, and Akanthomyces muscarius), with a significantly higher response intensity for the targeted microorganism. The sensor’s practical applicability was evaluated using B. cinerea-containing water collected from a greenhouse dedicated to tomato cultivation. These results highlight the platform’s potential as a routine monitoring tool for this plant pathogen.

Early detection of Mycobacterium leprae infection is essential to interrupt leprosy transmission and guide prophylactic interventions. Current diagnostic strategies rely largely on clinical signs, and laboratory tools lack sensitivity to detect asymptomatic individuals, who can play a critical role in disease transmission and evolve to disease as well. In this study, we report the development of a heat-transfer method (HTM)-based biosensor employing a newly designed multiepitope protein receptor, capable of detecting anti-M. leprae antibodies in human serum, with sensitivity for leprosy contacts. The protein, initially tested in ELISA assays, was then immobilized on aluminum chips, and its successful attachment and functionality were confirmed using FTIR, EDX, ELISA-like, and confocal fluorescence assays. Evaluation of the sensor was performed using an HTM transducing platform, where thermal measurements revealed a clear response to antibody binding that is serum dilution-dependent as it is in established methods such as ELISA. The biosensor distinguished serum from M. leprae-exposed individuals from that of non-exposed controls and a tuberculosis sample, with effect sizes up to four times higher. Notably, responses were comparable to the ones obtained using ELISA at similar serum dilution. These findings demonstrate, for the first time, the feasibility of using a thermal biosensing platform to detect specific antibodies in a clinically relevant scenario, paving the way for a sensitive, low-cost, and point-of-care tool for early leprosy detection and contact surveillance. This strategy addresses the critical challenge of identifying M. leprae exposure and holds potential for broader application in infectious disease diagnostics.

Leprosy remains an important neglected tropical disease with about 200,000 new cases detected annually worldwide. Although the disease is highly responsive to treatment, a timely and accurate diagnosis continues to be a critical barrier to disease control. Traditional diagnostic methods, including PCR, bacilloscopy, histopathology, and serology, are hindered by limited sensitivity, procedural complexity, and restricted accessibility in resource-constrained settings. This review summarizes studies from the past decade on biosensor-based strategies for leprosy diagnosis. Biosensor platforms for leprosy include electrochemical, piezoelectric, and optical systems, with recent innovations encompassing immunosensors, biomimetic, and DNA-based approaches, some achieving diagnostic accuracies above 90%. These platforms employ different bioreceptors such as conjugated peptides, DNA probes, and molecularly imprinted polymers. Certain platforms can also differentiate paucibacillary from multibacillary cases, addressing a critical limitation of the current methods. These capabilities highlight the potential of biosensors as powerful tools for point-of-care testing. However, clinical translation is constrained by challenges such as affordability, robustness under field conditions, and the lack of large-scale validation studies. Additional operational barriers, including regulatory approval, supply chain logistics, and user training, must also be addressed. Future progress will depend on multidisciplinary strategies, integrating novel biomarker discovery as recognition elements and exploring detection systems previously used for other mycobacterial and infectious diseases. Large multicenter trials and user-centered design approaches are essential for clinical implementation. By overcoming these challenges, biosensors have the potential to redefine leprosy diagnostics, enabling earlier detection and improved surveillance, and accelerating progress toward global elimination goals.

Early and accurate identification of individuals exposed to leprosy is essential for controlling the transmission. Our study assessed the potential of a novel recombinant multiepitope protein, designed using five synthetic Mycobacterium leprae-specific peptides that were selected based on their prior performance in ELISA assays. The protein was expressed in a bacterial system and further evaluated in ELISA assays for IgG and IgM. The reactivity was assessed in 357 serum samples from leprosy patients, 234 household contacts (HHC), 26 tuberculosis patients, and 61 healthy controls from different regions of Brazil. The multiepitope protein showed strong IgG and IgM responses in HHC, with AUC values above 0.80. No significant differences in antibody responses were observed between HHC of paucibacillary and multibacillary patients, for either the peptides or the novel protein. Among leprosy patients, peptides and protein responses ranged from moderate to good (AUC 0.67–0.81). These findings highlight the utility of these novel markers as promising tools for serological screening of exposure to M. leprae.

Xylazine adulterated Fentanyl is considered one of the deadliest drug threats ever faced in the United States. However, due to the complexity of the illegal drug supply, xylazine detection in the frame of drug-checking (harm reduction) remains an unsolved challenge, one which has cost numerous lives across North America. In this work, we present two sensor platforms for detecting xylazine in drug-checking applications. Both platforms are based on molecularly imprinted polymers (MIPs) using vinyl phosphonic acid as the main monomer. By combining the MIPs with thermometric and colorimetric readouts, we achieved xylazine detection in a wide concentration range, relevant in real-world scenarios. First, the heat-transfer method (HTM) allowed xylazine detection in the low concentration range within 15 min per concentration, with a limit of detection (LoD) of 16.5 ng/mL (75 nM). Second, a dye displacement assay employing methylene blue provided rapid ( 76 μg/mL-five times lower than the average concentration reported for street samples. Additionally, the colorimetric sensor exhibited potential for detecting various unwanted xylazine analogues, which could potentially act as fentanyl adulterants in the future. Most importantly, the colorimetric sensor consistently detected xylazine in a highly complex, street-like fentanyl sample containing five common interferents. The synergy of the proposed sensors offers a promising alternative for centralized and on-site xylazine screening in harm reduction settings.

Malaria is a major public healthcare concern worldwide, representing a leading cause of death in specific regions. The gold standard for diagnosis is microscopic analysis, but this requires a laboratory setting, trained staff, and infrastructure and is therefore typically slow and dependent on the experience of the technician. This study introduces, for the first time, a biomimetic sensing platform for the direct detection of the disease. The heart of the sensor consists of a synthetic receptor created by surface imprinting Plasmodium falciparum-infected erythrocytes in a polymeric matrix. This receptor layer is coupled to a low-cost and fast thermal transducer platform, allowing for real time detection of the infection. The artificial receptor is a composite of poly(dimethylsiloxane) and graphene oxide that, in combination with the thermal readout, exhibited a limit of detection below 0.5% parasitemia in erythrocyte samples. This value is relevant for the diagnosis of infection in patients with low parasitemia levels. This study proves that biomimetic sensors could be further explored for the development of point-of-care technologies for the management of the disease.

Pseudomonas aeruginosa is a ubiquitous multi-drug-resistant bacterium, capable of causing serious illnesses and infections. This research focuses on the development of a thermal sensor for the indirect detection of P. aeruginosa infection using molecularly imprinted polymers (MIPs). This was achieved by developing MIPs for the detection of pyocyanin, the main toxin secreted by P. aeruginosa. To this end, phenazine was used as a dummy template, evaluating several polymeric compositions to achieve a selective MIP for pyocyanin recognition. The sensitivity of the synthesized MIPs was investigated by UV-vis analysis, with the best composition having a maximum rebinding capacity of 30 μmol g^-1 and an imprinting factor (IF) of 1.59. Subsequently, the MIP particles were immobilized onto planar aluminum chips using an adhesive layer, to perform thermal resistance measurements at clinically relevant concentrations of pyocyanin (1.4-9.8 μM), achieving a limit of detection (LoD) of 0.347 ± 0.027 μM. The selectivity of the sensor was also scrutinized by subjecting the receptor to potential interferents. Furthermore, the rebinding was demonstrated in King's A medium, highlighting the potential of the sensor for the indirect detection of P. aeruginosa in complex fluids. The research culminates in the demonstration of the MIP-based sensor's applicability for clinical diagnosis. To achieve this goal, an experiment was performed in which the sensor was exposed to pyocyanin-spiked saliva samples, achieving a limit of detection of 0.569 ± 0.063 μM and demonstrating that this technology is suitable to detect the presence of the toxin even at the very first stage of its production.