Electrochemiluminescence Double Quenching System Based on Novel Emitter GdPO4:Eu with Low-Excited Positive Potential for Ultrasensitive Procalcitonin Detection

Gold-copper-doped lanthanide luminescent metal-organic backbone induced self-enhanced molecularly imprinted ECL sensors for ultra-sensitive detection of chlorpyrifos

Herein, a self-enhanced molecularly imprinted polymer luminescence (MIP-ECL) sensing platform based on gold-copper doped Tb-MOFs (Au@Cu:Tb-MOFs) was constructed for ultra-sensitive detection of chlorpyrifos (CPF). In this work, Au@Cu:Tb-MOFs as co-reaction promoters greatly improve the ECL emission signal, while Au@Cu:Tb-MOFs were used as cathode emitters. And chlorpyrifos and 4,7-bis(thiophene-2-yl)benzo [c][1,2,5] thiadiazole were electropolymerized on electrode surface to form MIP, where this films with thiophene derivatives could greatly improve ECL signal. Notably, the introduction of MIP as recognition elements enabled specific identification of target analytes, in which molecular docking technique validated target analyte and functional monomers are tightly bound through Pi-alkyl interaction. As the concentration of CPF increases, the ECL signal gradually decreases, showing a good linear relationship in the range of 0.1-106 pg/mL with a low detection limit (LOD) of 0.029 pg/mL. Moreover, actual sample testing experiment of this method displayed a special correlation in organophosphorus detection and development potential in actual sample analysis.

Two Birds with one Stone: Dual-mode immunoassay constructed using a novel emitter ethylene glycol-induced perylene diimide and a multifunctional ANS probe

Perylene diimide (PDI) is a readily reducible electron-deficient dye that exhibits strong photoluminescent properties, providing new opportunities for synthesizing novel electrochemiluminescence (ECL) emitters. In this study, ethylene glycol (EG) was used to induce the self-assembly of PDI supramolecules for the preparation of ultrathin EG-PDI nanosheets characterized by low crystallinity and weak stacking interaction. Notably, EG-PDI integrates luminescent and catalytic functions into one device, accelerating the interfacial electron transfer and the faster charge transfer kinetics of EG-PDI with K2S2O8. Furthermore, the narrow band gap of EG-PDI facilitates its excitation at an ultra-low potential (-0.3 V). To improve the efficiency of tumor marker analysis, multifunctional Au nanostars (ANS) was introduced both as an energy acceptor of the ECL system and a probe for the photothermal system. Dual-mode immunoassay have demonstrated superior analytical performance in detecting alpha-fetoprotein (AFP), meeting the requirements of modern clinical diagnostics in resource-limited environments.

Chitosan modified graphene field-effect transistor biosensor for ultrasensitive procalcitonin detection

Sepsis is a systemic inflammatory response caused by a bacterial infection that often leading to tissue damage, organ failure and death. Procalcitonin (PCT), as a peptide precursor to hormones, is the main biomarker to identification of the sepsis. In this study, a chitosan modified graphene field transistor (CTS-GFET) was established and first time used for PCT ultra-sensitive detection. CTS was functionalized on the GFET channel surface to immobilized anti-PCT by glutaraldehyde. This biosensor exhibited the detection limit as low as 0.82 ag/mL in PBS, which exhibited 3 times enhancement compared with GFET biosensors. The enhancement mechanisms of CTS-GFET were studied by electrical theoretical model. In addition, the CTS-GFET biosensor was successfully applied to quantify the concentration of the PCT in human serum samples, indicating the potential use in clinical application.

Rapid and sensitive electrochemiluminescence detection using easily fabricated sensor with an integrated two-electrode system

The electrochemiluminescence (ECL) behavior of a tri(2,2'-bipyridyl)ruthenium(ii) (Ru(bpy)32+)/tripropylamine (TPrA) system was investigated in sensor chips with two kinds of integrated two-electrode systems, which included screen-printed electrodes (SPE) and physical vapor deposition (PVD) electrodes. Firstly, under excitation with an optimal transient potential (TP) within 100 ms, the ECL assay could be carried out on the microchips using an Au & Au electrode system, emitting strong and stable light signal. Secondly, on the PVD chip, the ECL intensity initiated by optimal TP was eight times stronger than the peak light signal emitted by the linear sweep voltammetry model. Finally, the logarithmic ECL intensities exhibited a linear increase with the logarithmic concentrations of Ru(bpy)32+ in both the SPE and PVD chips without any reference electrode (RE). Typically, the integration of an interdigital two-electrode system in the microchip significantly enhanced the ECL sensitivity of Ru(bpy)32+ because the large relative area between the working electrode (WE) and counter electrode (CE) achieved a highly efficient mass transfer. This improvement enabled the establishment of a reliable linear relationship across a wide concentration range, spanning from 1 pM to 1 μM (R2 = 0.998). Therefore, the exceptional ECL response of the Ru(bpy)32+/TPrA system on microfluidic chips using a two-electrode system and the TP excitation model has been demonstrated. This suggests that ECL chips without a RE have broad potential for the rapid and sensitive detection of multiple targets.

An electrochemiluminescence immunosensor with double co-reaction accelerators based on Ag3PO4@EuPO4-AgNP for detecting squamous cell carcinoma antigen

This study aimed to design a sandwich electrochemiluminescence (ECL) immunosensor with double co-reaction accelerators for sensitively detecting squamous cell carcinoma antigen (SCCA). First, silver orthophosphate (Ag3PO4) nanoparticles were modified on the surface of EuPO4 nanowires to improve their poor dispersibility/solubility. At the same time, EuPO4 was used as a co-reaction accelerator to catalyze S2O82- to produce more intermediates (SO4•-), significantly enhancing the ECL signal of Ag3PO4. Ag nanoparticles (AgNP) modified on Ag3PO4@EuPO4 composite nanomaterials were used not only as linkers of luminescence groups and biomarkers but also as a co-reaction accelerator to effectively enhance ECL signal. The designed ECL immunosensor displayed several advantages, including good stability and reproducibility. Under the optimal conditions, its linear range in detecting SCCA was 0.0001-50 ng·mL-1, the detection limit was 25 fg·mL-1 (S/N = 3), the recovery was 96.6-100.4%, and the relative standard deviation was less than 4.8%. It was successfully applied to detect SCCA in human serum.

Electrochemiluminescence nanoemitters for immunoassay of protein biomarkers

The family of electrochemiluminescent luminophores has witnessed quick development since the electrochemiluminescence (ECL) phenomenon of silicon nanoparticles was first reported in 2002. Moreover, these developed ECL nanoemitters have extensively been applied in sensitive detection of protein biomarker by combining with immunological recognition. This review firstly summarized the origin and development of various ECL nanoemitters including inorganic and organic nanomaterials, with an emphasis on metal-organic frameworks (MOFs)-based ECL nanoemitters. Several effective strategies to amplify the ECL response of nanoemitters and improve the sensitivity of immunosensing were discussed. The application of ECL nanoemitters in immunoassay of protein biomarkers for diagnosis of cancers and other diseases, especially lung cancer and heart diseases, was comprehensively presented. The recent development of ECL imaging with the nanoemitters as ECL tags for detection of multiplex protein biomarkers on single cell membrane also attracted attention. Finally, the future opportunities and challenges in the ECL biosensing field were highlighted.

Construction of efficient electrochemiluminescence resonance energy transfer sensor based on SnO2/SnS2QDs-Ru@IRMOF-3 composite for sensitive detection of procalcitonin

An efficient electrochemiluminescence resonance energy transfer (ECL-RET) method is proposed which combines the luminescent materials of tris(4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) (energy donor) and tin dioxide and tin disulfide quantum dots (SnO₂/SnS₂QDs) (energy acceptor) into the isoreticular metal - organic framework-3 (IRMOF-3) material to form a composite. In this mode, the distance between the energy donor and the acceptor was greatly shortened, reducing the energy loss, and thereby effectively improving RET efficiency and further significantly improving the ECL signal. The obtained composite (SnO₂/SnS₂QDs-Ru@IRMOF-3) was combined with sandwich immunoreaction to construct an ECL immunosensor for the sensitive detection of procalcitonin (PCT). Under the optimized experimental conditions with a working potential of - 1.48 V (vs Ag/AgCl), the proposed PCT biosensor exhibited a linear concentration range of 1 × 10^-4-200 ng mL^-1, with a detection limit of 0.029 pg mL^-1 (S/N = 3). The biosensor was used to detect PCT in actual samples. The biosensor has broad application prospects in biological analysis and clinical diagnosis due to its high sensitivity, good selectivity, and good stability.

Dual-Mechanism Quenching of Electrochemiluminescence Immunosensor Based on a Novel ECL Emitter Polyoxomolybdate-Zirconia for 17β-Estradiol Detection

The exploration of novel electrochemiluminescence (ECL) reagents has been a breakthrough work in ECL immunoassay. In this work, the ECL properties of polyoxomolybdate-zirconia (POM-ZrO₂) were discovered for the first time and their luminescence mechanism was initially explored. Virgulate POM-ZrO₂ was synthesized from phosphomolybdic acid hydrate and zirconium oxychloride by solvothermal method, which achieved intense and stabilized cathode ECL emission at a negative potential. Polyaniline@Au nanocrystals (PANI@AuNPs) as the executor of the dual-mechanism quenching strategy were used to reduce the output signal. The quenching efficiency was significantly enhanced by the dual mechanisms of ECL energy transfer and electron transfer. Specifically, PANI@AuNPs can serve as an energy receptor to absorb the energy emitted by POM-ZrO₂ (energy donor), while the appropriate energy level can be regarded as the condition for electron transfer to quench the ECL intensity of POM-ZrO₂. Herein, the proposed dual-mechanism quenching strategy was applied to the immunoassay of 17β-estradiol by constructing a competitive immunosensor. As expected, the immunosensor demonstrated favorable analytical performance and a wide sensing range from 0.01 pg/mL to 200 ng/mL. Hence, it provides a novel method for the sensitive analysis of other biomolecules, such as disease markers and environmental estrogens.

High-bioactivity microfluidic immunosensing platform for electrochemiluminescence determination of CYFRA 21-1 with the introduction of Fe3O4@Cu@Cu2O

Relying on the electrochemiluminescence (ECL) and microfluidic technology, an immunosensor chip with high bioactivity was designed for sensitive determination of cytokeratin 19 fragment 21-1 (CYFRA 21-1). The mesoporous nanomaterial Fe₃O₄@Cu@Cu₂O as the co-reaction accelerator was used to catalyze the S₂O₈^2- to produce more SO₄^•- to achieve the amplification of the ECL signal. In fact, the generating of SO₄^•- could not only be done with the aid of the reversible cycles of Fe²⁺ and Fe³⁺ and Cu⁺ and Cu²⁺, but could be achieved also through the catalase-like function of Fe₃O₄. What is more, it has also been proved that Fe₃O₄@Cu@Cu₂O exhibited better catalytic performance than single Fe₃O₄, Cu₂O, and Cu@Cu₂O, which supported its application in this system. In addition, a portable microfluidic immunosensor chip for CYFRA 21-1-sensitive determination was assembled, which showed high selectivity, sensitivity, and strong universality in clinical cancer screening and diagnosis. It should be noted that HWRGWVC (HWR) was introduced as the antibody fixator to improve the incubation and binding efficiency of the antibody, which increased the ECL intensity and improved the sensitivity of the immunosensor. This strategy provided a new idea for cancer identification and diagnosis in clinical medicine.

Bio-Receptors Functionalized Nanoparticles: A Resourceful Sensing and Colorimetric Detection Tool for Pathogenic Bacteria and Microbial Biomolecules

Pathogenic bacteria and several biomolecules produced by cells and living organisms are common biological components posing a harmful threat to global health. Several studies have devised methods for the detection of varying pathogenic bacteria and biomolecules in different settings such as food, water, soil, among others. Some of the detection studies highlighting target pathogenic bacteria and biomolecules, mechanisms of detection, colorimetric outputs, and detection limits have been summarized in this review. In the last 2 decades, studies have harnessed various nanotechnology-based methods for the detection of pathogenic bacteria and biomolecules with much attention on functionalization techniques. This review considers the detection mechanisms, colorimetric prowess of bio-receptors and compares the reported detection efficiency for some bio-receptor functionalized nanoparticles. Some studies reported visual, rapid, and high-intensity colorimetric detection of pathogenic bacteria and biomolecules at a very low concentration of the analyte. Other studies reported slight colorimetric detection only with a large concentration of an analyte. The effectiveness of bio-receptor functionalized nanoparticles as detection component varies depending on their selectivity, specificity, and the binding interaction exhibited by nanoparticles, bio-receptor, and analytes to form a bio-sensing complex. It is however important to note that the colorimetric properties of some bio-receptor functionalized nanoparticles have shown strong and brilliant potential for real-time and visual-aided diagnostic results, not only to assess food and water quality but also for environmental monitoring of pathogenic bacteria and a wide array of biomolecules.

Low-sample-consumption and ultrasensitive detection of procalcitonin by boronate affinity recognition-enhanced dynamic light scattering biosensor

Accurate determination of procalcitonin (PCT) is highly crucial in bacterial infection diagnosis. Many biosensors previously developed suffer from large sample consumption or lengthy waiting time, which raise difficulties for more vulnerable patients, such as infants, old people, and other critically ill patients. To address this dilemma, we present an innovative boronate affinity recognition (BAR)-enhanced dynamic light scattering (DLS) biosensor to achieve ultrasensitive PCT detection. In this biosensing system, monoclonal antibody-modified magnetic nanoparticles (MNP@mAb) are designed as probes to capture PCT from serum samples and generate DLS signal transduction. Polyvalent phenylboronic acid-labeled bovine serum albumin (BSA@PBA) is used as scaffold to aggregate MNP@mAb and PCT (MNP@mAb-PCT) complex because of the specific interaction of cis-diol-containing PCT with boronic acid ligands on the surface of BSA@PBA. The BAR-enhanced DLS biosensor shows ultrahigh sensitivity to PCT determination due to high binding affinity, with the limit of detection of 0.03 pg/mL. The total detection time of PCT in whole blood or serum is less than 15 min with small sample consumption (about 1 μL) due to the rapid magnetic separation and aggregation of MNP@mAb-PCT triggered by BSA@PBA. In addition, the proposed DLS biosensor exhibits a high specificity for PCT quantitative detection. Therefore, this work provides a promising and versatile strategy for extending DLS biosensor to rapid and ultrasensitive detection of trace PCT for broader patients and more urgent cases.

Copper doped terbium metal organic framework as emitter for sensitive electrochemiluminescence detection of CYFRA 21-1

Lanthanide metal organic frameworks (L-MOFs) are emerging as promising electrochemiluminescence (ECL) emitters for bioanalysis. This work proposed a copper doped terbium MOF as a luminescent tag for construction of a "signal-on" ECL immunosensing method. The Tb-Cu-PA MOF was prepared using Tb³⁺ and Cu²⁺ ions as metal linkers and m-phthalic acid as bridge ligand, and exhibited strong ECL emission with K₂S₂O₈ as a coreactant. The immunosensor was prepared by immobilizing capture antibody on Pd nanoparticles modified Ni-Co layered double hydroxide (Pd-ZIF-67@LDH) nanoboxes, which showed strong electrocatalytic activity toward the reduction of S₂O₈^2- for amplifying the ECL signal. Upon the sandwich-typed immunoreactions, Tb-Cu-PA MOF labeled antibody was introduced onto the immunosensor for sensitive ECL detection of target protein. Using cytokeratin 19 fragment 21-1 (CYFRA21-1), a representative lung cancer biomarker, as target model, the ECL immunosensing method showed a linear range of 0.01-100 ng/mL and a detection limit of 2.6 pg/mL (S/N = 3). This immunosensing strategy highlighted the advances of using luminescent and electroactive MOFs in the developments of highly efficient immunosensors for bioanalysis.

Extensive tailoring of REPO4 and REVO4 crystallites via solution processing and luminescence

This article highlighted the recent achievements in crystal engineering of REPO4 and REVO4via solution processing, with an emphasis on solution chemistry, the role of chelate ion, crystallization mechanism and luminescence properties.

Copper-Doped Terbium Luminescent Metal Organic Framework as an Emitter and a Co-reaction Promoter for Amplified Electrochemiluminescence Immunoassay

This work designed a signal amplification strategy for construction of a highly sensitive electrochemiluminescence (ECL) biosensor by doping Cu²⁺ in a terbium luminescent metal organic framework (Cu:Tb-MOF) to act as a co-reaction promoter, which enhanced the generation of SO₄^•- radical during the cathodic process in the presence of K₂S₂O₈ as a co-reactant. The porous and hollow morphology and the size of Cu:Tb-MOF could be efficiently tuned via changing the molar ratio of Cu²⁺ and Tb³⁺ and the reaction time, which were related to the specific surface area, pore diameter, and the ECL intensity of the MOF structure. To further improve the sensitivity of the ECL biosensor, H₂O₂ was introduced into the ECL system to act as another co-reaction promoter, leading to a new ECL mechanism involving dual co-reaction promoters. In view of the low electron transfer resistance of Cu:Tb-MOF, a label-free ECL immunosensor was conveniently constructed by co-immobilizing Cu:Tb-MOF and the capture antibody on the electrode surface. Using pro-gastrin-releasing peptide (ProGRP, a biomarker of small-cell lung cancer) as the model target, the proposed immunosensor exhibited excellent performance with a detection range of 1.0 pg·mL^-1 to 50 ng·mL^-1 and a limit of detection down to 0.68 pg·mL^-1 (3σ). This work demonstrated a strategy to use the MOF structures as both an emitter and a co-reaction promoter for amplified ECL emission and proposed an innovative route to extend the application of lanthanide MOFs.

Low-Triggering-Potential Electrochemiluminescence from Surface-Confined CuInS2@ZnS Nanocrystals and their Biosensing Applications

Electrochemiluminescence (ECL) of low triggering potential is strongly anticipated for ECL assays with less inherent electrochemical interference and improved long-term stability of the working electrode. Herein, effects of the thiol capping agents and the states of luminophores, i.e., the thiol-capped CuInS₂@ZnS nanocrystals (CuInS₂@ZnS-Thiol), on the ECL triggering potential of CuInS₂@ZnS-Thiol/N₂H₄·H₂O were explored on the Au working electrode. The thiol capping agent of glutathione (GSH) not only enabled CuInS₂@ZnS-Thiol/N₂H₄·H₂O with the stronger oxidative-reduction ECL than other thiol capping agents but also demonstrated the largest shift for the ECL triggering potential of CuInS₂@ZnS-Thiol/N₂H₄·H₂O upon changing the luminophores from the monodispersed state to the surface-confined state. CuInS₂@ZnS-GSH/N₂H₄·H₂O exhibited an efficient oxidative-reduction ECL around 0.78 V (vs Ag/AgCl) with CuInS₂@ZnS-GSH of the monodispersed state. Upon employing CuInS₂@ZnS-GSH as the ECL tag and immobilizing them onto the Au working electrode, the oxidative-reduction ECL of CuInS₂@ZnS-GSH/N₂H₄·H₂O was lowered to 0.32 V (vs Ag/AgCl), which was about 0.88 V lower than that of traditional Ru(bpy)₃²⁺/TPrA (typically ∼1.2 V, vs Ag/AgCl). The ECL of the CuInS₂@ZnS-GSH/N₂H₄·H₂O system with the luminophore of both monodispersed and surface-confined states was spectrally identical to each other, indicating that this surface-confining strategy exhibited negligible effect on the excited state for the ECL of CuInS₂@ZnS-GSH. A surface-confined ECL sensor around 0.32 V was fabricated with CuInS₂@ZnS-GSH as a luminophore, which could sensitively and selectively determine the K-RAS gene from 1 to 500 pM with a limit of detection at 0.5 pmol L^-1 (S/N = 3).

Functionalized europium-porphyrin coordination polymer: Rational design of high performance electrochemiluminescence emitter for mucin 1 sensing

The excellent characteristics of porphyrins have inspired widespread interest in electrochemiluminescence (ECL). However, the limited ECL intensity and poor stability of porphyrins in aqueous solution are still severely restricted further biological application. Here, we subtly synthesized a functionalized europium and 5,10,15,20-tetrakis (4-carboxyphenyl) porphyrin (TCPP) coordination polymer (Eu-PCP) by a one-step solvothermal method. In sharp contrast to the pristine TCPP, Eu-PCP showed a higher and more stable ECL red-light emission (673 nm) at low potential (-1.1 V, vs Ag/AgCl), which was 7.7-fold higher ECL intensity and 4.6-fold efficiency. In view of the crucial role of mucin 1 (MUC1) in tumor overexpression, it was selected as the target molecule. Combined with exonuclease III (Exo III)-assisted recycling amplification strategy, a ternary ECL biosensor was constructed for the MUC1 detection based on Eu-PCP as a satisfied ECL emitter, gold nanoparticles capped CeO₂ (CeO₂@Au) as the coreactant accelerator and peroxydisulfate as coreactant. Meanwhile, gold nanoparticles capped MnO₂ (MnO₂@Au) was used as the quenching probe to achieve a highly sensitive detection of MUC1. The proposed biosensor exhibited a wide linear range from 1 fg mL^-1 to 10 ng mL^-1 with a low limit of detection (0.32 fg mL^-1). By changing the corresponding target recognition DNA, this strategy could be expanded to detect other biomarkers.

Facile construction of ratiometric electrochemical immunosensor using hierarchical PtCoIr nanowires and porous SiO2@Ag nanoparticles for accurate detection of septicemia biomarker

Procalcitonin (PCT) is a sensitive and specific biomarker for sepsis diagnosis. In this study, a novel ratio-typed electrochemical immunosensor was constructed for reliable and sensitive assay of PCT based on hierarchical PtCoIr nanowires/polyethylene polyamine-grafted-ferrocene (PtCoIr HNWs/PEPA-Fc) and porous SiO₂@Ag nanoparticles-toluidine blue (porous SiO₂@Ag NPs-TB). Importantly, the PtCoIr HNWs/PEPA-Fc was first modified on the sensing interface, which harvested stable and strong electrochemical signals for readout of Fc due to the enriched anchoring sites created by the PtCoIr HNWs. Meanwhile, porous SiO₂@Ag NPs-TB behaved as the label to conjugate with secondary antibody (Ab₂), which also provided another strong detection signals originated from TB confined in such porous structures. The resulting immunosensor displayed a measurable output of procalcitonin (PCT) in the dynamic scope of 0.001 ~ 100 ng mL^-1 with a low limit of detection (LOD) of 0.46 pg mL^-1 (S/N = 3). Moreover, we exploited this strategy for PCT assay in a diluted human serum sample with acceptable results, exhibiting promising applications in the clinical analysis.

A frogspawn-like Ag@C core–shell structure for an ultrasensitive label-free electrochemical immunosensing of carcinoembryonic antigen in blood plasma

Novel frogspawn-like Ag@C nanoparticles were successfully used to fabricate an ultrasensitive electrochemical immunosensing platform toward CEA in human blood samples.

Protein Discrimination Using a Fluorescence-Based Sensor Array of Thiacarbocyanine-GUMBOS

Sensitive and selective detection of proteins from complex samples has gained substantial interest within the scientific community. Early and precise detection of key proteins plays an important role in potential clinical diagnosis, treatment of different diseases, and proteomic research. In the study reported here, six different compounds belonging to a group of uniform materials based on organic salts (GUMBOS) have been synthesized using three thiacarbocyanine (TC) dyes and employed as fluorescent sensors. Fluorescence properties of micro- and nanoaggregates of these TC-based GUMBOS formed in phosphate buffer solutions are studied in the absence and presence of seven proteins. Fluorescence response patterns of these TC-based GUMBOS were analyzed by linear discriminant analysis (LDA). The constructed LDA model allowed discrimination of these seven proteins at various concentrations with 100% accuracy. The sensing and discrimination abilities of these TC-based GUMBOS were further evaluated in mixtures of two major proteins, i.e., human serum albumin and hemoglobin. Fluorescence response patterns of these mixtures were analyzed by LDA. This model allowed discrimination of various mixtures with 100% accuracy. Moreover, spiked urine samples were prepared and the responses of these sensors were collected and analyzed by LDA. Remarkably, discrimination of these seven proteins was also achieved with 100% accuracy.

Magnetic Bead-Based Electrochemical Immunoassays On-Drop and On-Chip for Procalcitonin Determination: Disposable Tools for Clinical Sepsis Diagnosis

Procalcitonin (PCT) is a known protein biomarker clinically used for the early stages of sepsis diagnosis and therapy guidance. For its reliable determination, sandwich format magnetic bead-based immunoassays with two different electrochemical detection approaches are described: (i) disposable screen-printed carbon electrodes (SPE-C, on-drop detection); (ii) electro-kinetically driven microfluidic chips with integrated Au electrodes (EMC-Au, on-chip detection). Both approaches exhibited enough sensitivity (limit of detection (LOD) of 0.1 and 0.04 ng mL⁻¹ for SPE-C and EMC-Au, respectively; cutoff 0.5 ng mL⁻¹), an adequate working range for the clinically relevant concentrations (0.5–1000 and 0.1–20 ng mL⁻¹ for SPE-C and EMC-Au, respectively), and good precision (RSD < 9%), using low sample volumes (25 µL) with total assay times less than 20 min. The suitability of both approaches was successfully demonstrated by the analysis of human serum and plasma samples, for which good recoveries were obtained (89–120%). Furthermore, the EMC-Au approach enabled the easy automation of the process, constituting a reliable alternative diagnostic tool for on-site/bed-site clinical analysis.

Polymer-Based Micromotor Fluorescence Immunoassay for On-the-Move Sensitive Procalcitonin Determination in Very Low Birth Weight Infants' Plasma

A new fluorescence micromotor-based immunoassay (FMIm) has been developed for procalcitonin (PCT) determination as an early sepsis diagnostic analytical tool. The micromotors combine the high binding capacity of the specific antibodies onto their polymeric polypyrrole outer layer (PPy layer), with their magnetic guidance (Ni layer) and self-propulsion by catalytic generation of oxygen bubbles (PtNP inner layer) to actively recognize the PCT antigen. This FMIm allowed a sensitive (LOD = 0.07 ng mL^-1) and direct PCT determination in clinical samples from very low-birth-weight infants (VLBWI) with sepsis suspicion, using small volumes of sample (25 μL) in a clinically relevant range of concentrations (0.5-150 ng mL^-1). The good agreement between PCT levels obtained by our micromotor-based method and routine immunofluorescence hospital determination demonstrates the feasibility for the analysis in VLBWI samples and its potential as a point-of-care diagnostic tool for sepsis.