Neurotransmitters play important roles in the normal functioning of the central nervous system. The accurate and sensitive quantification of neurotransmitters using chromatographic and optical analytical methods is of key interest in the management of related neurodegenerative maladies. In this study, electrochemical sensors based on electrodes modified with composite nanomaterials were investigated as reliable, fast and low-cost analytical devices for direct neurotransmitter quantification. A sensing platform was developed by means of an innovative preparation method using alternating currents (ACs). Low-cost sensing materials based on gold nanoparticles (AuNPs) and poly(3,4-ethylenedioxythiophene) were synthesized in situ onto glassy carbon electrodes by means of AC. A polymeric matrix was prepared by applying an AC at a frequency of 100 mHz for 300s, resulting in an increase in roughness. AuNPs were synthesized by applying an AC at a frequency of 50 mHz for 100s. The use of AC enabled the preparation of AuNPs embedded in the polymeric matrix characterized by increased electroactive surface area. The sensing platform was tested and successfully validated in the detection of epinephrine, with good analytical performance, achieving a low detection limit of 1.8 µM and a wide linear response range of 2 to 100 μM epinephrine. The practical applicability of the electrochemical sensing platform was demonstrated inthe detection of epinephrine in human serum samples with good accuracy and recovery. AC frequency modulated the electrodeposition process, resulting in enhanced roughness. Consequently, the novel AC-based method ensured an improved sensitivity of the sensing platform compared to other electrochemical epinephrine sensors produced by classical methods, like potentiostatic and galvanostatic ones.

Acknowledgments: This work was supported by a grant of the Ministry of Research, Innovation and Digitization, CCCDI-UEFISCDI, project number PN-III-P2-2.1-PED-2021-3693, (607PED/27.06.2022), within PNCDI III.

Quercetin (QR-3,3′,4′,5,7-pentahydroxylflavone) is very well known as a strong antioxidant with anti-inflammatory, antiviral, antineoplastic, and antithrombotic properties that can act as a free radical scavenger in human beings. It can be found in vegetables such as capers, lovage, broccoli, lettuce, spinach, onions, tea, seeds, and fruit skins. QR is recognized as one of the most important nutrients in a person's daily diet. Lipoic acid (LA), also known as 1,2-dithiolane-3-pentanoic acid, is synthesized by animal, plant, and human cells from fatty acids and cysteine. LA is often used in the treatment of oxidative stress, diabetes, cardiovascular and hepatitis diseases, and heavy metal poisoning. In the literature, several chromatographic and optical methods have been developed in order to determine the presence of lipoic acid and quercetin with a low detection limit, but these methods have drawbacks such as sample pretreatments, the use of hazardous and expansive chemicals, and sophisticated extraction procedures. In view of this, an alternate electrochemical method for the sensitive determination of LA and QR is required. In the present work, we have developed novel electrochemical platforms for LA and QR sensing based on PEDOT-PB (Prussian Blue) and PEDOT-AgNPs . Both nanocomposite materials were synthesized using a sinusoidal currents (SCs) method. The amplitude and frequency of the SCs method have been optimized. The developed electrochemical sensing platforms that use PEDOT-PB and PEDOT-AgNPs were assessed and validated for their LA and QR determination in synthetic and real samples in terms of their limit of detection, limit of quantification, and linear response range. The proposed sensing platforms ensured a comparable, fast, simple, and reliable detection of the target analytes QR and LA without sample pretreatment, as is usually required by other analytical methodologies such as chromatographic and optical methods.

Acknowledgments: this work was supported by a grant from the Ministry of Research, Innovation and Digitization, CCCDI-UEFISCDI, project number PN-III-P2-2.1-PED-2021-3693, (607PED/27.06.2022), within PNCDI III.

The severity of various diseases is related to the concentration of interleukin 6 (IL-6), a proinflammatory cytokine crucial for the proliferation and differentiation of immunocompetent and hematopoietic cells. In ischemic cerebrovascular disease, it is known that, after traumatic injury, increased plasma levels of IL-6 are associated with neuronal inflammation and brain death. Research has shown that elevated plasma IL-6 levels within the first 12 h after an ischemic vascular event are strong predictors of early mortality. Therefore, developing a device that can detect the presence of IL-6 in a murine model of induced ischemic disease could be beneficial for monitoring the disease and selecting the appropriate treatment in the future. This study aimed to detect IL-6 using biosensors developed within optical fibers; the biosensors were assembled using a self-assembled monolayer technique. Subsequently, detection was carried out using samples from rats (Sprague Dawley strain) with an induced ischemic disease. Samples were left to interact with the sample for 2 h to characterize the changes in the sensor's transmission response. Both the response of the biosensor to IL-6 and the self-assembly steps were characterized by transmission spectroscopy at wavelengths of 1250-1450 nm and micro-MIR spectroscopy. Spectral changes were observed at different stages of the assembly and detection processes. By performing a PCA on the experimental data, it was possible to observe the clustering of the different assembly stages and the final detection. This allowed for discrimination not only at the stage of the biosensor's construction but also in its detection of IL-6.

Mastitis has a significant impact on animal welfare and dairy industry profitability (regular losses 5%-25%, outbreaks 85%), which is the main reason for antibiotic use (risk to the food chain). Diagnosis is based on clinical observations and measures of the inflammatory response by somatic cell counts (SCC) in milk (crucial in quality and salubrity, with limits of 400,000 cells/ml in the EU and 750,000 cells/ml in the US). SCC is a late indicator of mastitis in milk, while early diagnosis is possible by an increased WBC count in the blood, suggesting probable mastitis (prevention). WBC react to inflammation, are released into the bloodstream, and migrate to the mammary gland to fight infection. Furthermore, the SSC value does not discriminate which cells are being counted, as this value can comprise the number different types of white blood cells and mammary gland cells. In this preliminary study, we recorded spectra of fresh milk obtained from 50 cows during milking. The milk collected was sent to a certified laboratory for butyric acid (TB), total protein (TP), urea (U), and SSC. This preliminary test using a spectroscopy point-of-care system provided the following metrics for on-site quantification: i. TB: R=0.79 and TE=10.0%; ii. TP: R=0.94 and TE=2.8%; and iii. U: R=0.73 and TE=12.0%; and iv. SSC: R=0.72 and TE=12%. These results demonstrate the possibility of performing a direct measurement of both milk quality and mastitis detection using reagentless POC spectral technology. Further research is necessary to evaluate the efficiency of POC in large-scale studies, as well as its capacity to discriminate between mammary and immune system cells and the presence of bacteria in milk.

Blood hemograms are an essential part of the clinical pathology diagnosis. This is especially important for chronic or acute conditions that require blood transfusions (e.g., anemia, cancer, hemophilia, and kidney and liver diseases). The capacity to monitor hemogram parameters using a wearable device without blood withdrawal is evaluated in this study using ultraviolet, visible, and near-infrared spectroscopy transmittance measurements simulating the wrist vein. Tylose gel and catheter tubes representing internal and near-surface wrist veins were studied to simulate different anatomical characteristics (e.g., skin tone, thickness, and depth of the monitored vein). The results showed that diffusive transmittance through the anatomical surrogate can correctly quantify the hemogram in terms of red blood cells (RBC), hemoglobin (Hgb), and discriminate levels of total white blood cells (WBC), achieving the following correlation (R) and total error (TE) against laboratory automated hematology machines: i. RBC: R=0.85 and TE=5.9%; ii. Hgb: R=0.81 and TE=5.25%; and iii. WBC: R=0.78 and TE=12.0%. These results demonstrate the possibility of performing a hemogram analysis without blood withdrawal using diffuse reflectance spectroscopy and artificial intelligence. Further research is necessary to evaluate the efficiency of different optical designs to be incorporated into a wearable bracelet system for noninvasive blood hemogram analysis.

Urinalysis is a noninvasive clinical chemistry method that is essential for human diagnosis. It is one of the most convenient body fluids that can be regularly monitored. Parameters such as urea (UR), uric acid (UA), creatinine (CRE), total protein (TP), and amylase (AMY) are commonly used in urinalysis. Urine analysis is now commonly performed at the point-of-care of test strips using colorimetric reactions. Similar reactions are used in the wet-lab approach in the clinical pathology laboratory. Spectral Point-of-Care can eliminate the use of reagents, allowing simple, fast, and consumable-free measurements. Herein, we present a case study of urinalysis using ultraviolet, visible, and near-infrared spectroscopy to relate spectral information to urine composition using self-learning artificial intelligence. This preliminary study demonstrated the capacity for direct detection of UR, CRE, TP, and AMY. These parameters were determined with significant statistical agreement in terms of correlation (R) and total error (TE) with the ground-truth methods used in the clinical pathology laboratory, where i. UR: R=0.79 and TE=15.5%; ii. UA: R=0.82 and TE=25.1%; iii. CRE: R=0.77 and TE=24.6%; iii. TP: R=0.74 and TE=25%; and iv. AMY: R=0.9 and TE=14.5%. These results demonstrate the possibility of performing clinical chemistry on urine without any reagents. Further research is necessary to enhance the detection of constituents with lower absorbance and expand the range of parameters investigated to develop a system that can perform urinalysis with a drop of urine.

Blood serum clinical chemistry is an essential part of clinical pathology diagnosis. Diagnostic parameters such as bilirubin (BIL), triglycerides (TRIG), uric acid (UA), urea (UR), creatinine (CRE), and myoglobin (MIO) are currently measured using reagent-based methods and wet lab chemistry, either at the clinical pathology laboratory by automated clinical chemistry machines (ACC) or at the point-of-care (POC). The use of reagents and fluids in technologies, such as chemo/biochips, restricts the application of POC technology to controlled environments and the need to manage consumables. Furthermore, blood is still collected by traditional venipuncture, centrifugation, or filtration to remove the cellular fraction, which increases the complexity of the operation and makes it less attractive for emergency or harsh scenarios. The current state-of-the-art limitations imposed by wet chemistry can be overcome using Spectral POC technology. In this study, we assessed blood serum chemistry using ultraviolet, visible, and near-infrared spectroscopy to relate spectral information to blood serum composition using self-learning artificial intelligence. This preliminary study demonstrated the feasibility of the direct detection of BIL, TRIG, UA, UR, CRE, and MIO. These parameters were determined with significant statistical agreement in terms of correlation (R) and total error (TE) with the ground-truth methods used in the clinical pathology laboratory, where i. BIL: R=0.99 and TE=10.4%; ii. TRIG: R=0.84 and TE=22.6%; iii. UR: R=0.82 and TE=32.3%; iv. CRE: R=0.88 and TE=20.9%; and v. MIO: R=0.96 and TE=42.65%. These results show that it is possible to perform clinical chemistry in the blood serum without any reagents. Further research is necessary to enhance the detection of constituents with less absorbance and expand the range of parameters investigated to develop a system that can perform blood chemistry directly in a drop of blood without using reagents or with the need to remove the cell fraction.

Blood hemograms are an essential part of the clinical pathology diagnosis. These are currently performed in the clinical laboratory using automated hematology machines (AHM) to discriminate blood cells by capillary laser scattering technology. Despite all the efforts in this miniaturization through microfluidics, this approach may not be appropriate for use at point-of-care (POC) under harsh or non-ideal operational conditions. AHM already uses low volumes of blood samples, but the blood is still collected by traditional venipuncture, and quantification of cells and hemoglobin still requires the use of reagents. A way to allow POC technology to be used in the harsh conditions of emergency medicine is to remove both venipuncture procedures and reagents.Research in canines and felines has demonstrated that hemogram analysis using reagent-less spectral technology at the point-of-care (POC) with an ultra-portable device that requires a single drop of blood is feasible for quantification with analytical-grade quality red blood cells (RBC), hemoglobin (Hgb), and hematocrit (HTC). Such POC uses solely ultraviolet, visible, and near-infrared spectroscopy to unscramble spectral information related to blood composition using self-learning artificial intelligence, providing unequivocal advantages in terms of convenience, real-time results, pain-free procedure, and reduced risk of infection.Herein, we demonstrate the feasibility of direct detection of RBC, Hgb, and HTC counts in human blood using spectral POC technology for medical applications. The results showed excellent agreement in terms of correlation (R) and total error (TE) against the ground-truth method, where i. RBC: R2=0.84-0.77, TE=7.3 -5.7%; ii. Hgb: R=0.74-0.85 and TE=4.9-6.4%; and iii. HTC: R=0.74-0.80 and TE=5.5-7.6%.Spectral POC demonstrates promise as a method for conducting rapid and simple point-of-care hemogram analyses in human patients. Further research is necessary to enhance and confirm the instrument's accuracy and to expand the range of parameters examined.

Insects cause substantial damage to crops, with the FAO estimating up to 40 percent of global crop losses, totaling around USD 220 billion annually. This underscores the critical need for innovative insect detection methods. Green leaf volatiles (GLVs) are organic compounds emitted by plants in response to insect attacks, offering potential for early detection . Current detection methods like gas chromatography–mass spectroscopy (GC-MS) are costly and complex, limiting real-time monitoring. There is a pressing need for affordable, portable sensors with high sensitivity to monitor GLVs in real time to address this critical agricultural challenge.

Chemical analyte binding to sensing materials can lead to optical, mechanical, thermal, electrical, and mass changes. By utilizing a transducer capable of detecting these multidimensional changes, sensor performance, including sensitivity and selectivity, can be enhanced. In this study, we developed a novel sensor capable of capturing both piezoelectric and colorimetric signals for the sensitive and selective detection of hexanol, a well-known green leaf volatile. We used a piezoelectric micro quartz tuning fork (MQTF) as the transducer. The MQTF's two prongs were coated with a metal–organic framework (MOF)–thymol blue hybrid sensing material, enabling detection through both color change and resonating frequency shifts upon hexanol binding. MOFs offer a high surface area and tunable pore size, enhancing sensor sensitivity and selectivity. The sensor's frequency shift indicates mass change due to hexanol binding to MOFs, while colorimetric sensing relies on thymol blue's reaction with hexanol. Tests demonstrate the sensor's ability to detect hexanol from 60ppb to 250ppm with high sensitivity and selectivity. Its compact size, cost-effectiveness, simple fabrication, wide detection range, and accuracy make the MOF-based colorimetric–piezoelectric sensor an ideal choice for early insect herbivore attack detection in agriculture.

The skin, the largest organ in the human body, provides several benefits for drug delivery. These advantages stem from its expansive surface area and the avoidance of the first-pass metabolism in the gastrointestinal tract. This, in turn, enhances drug bioavailability and minimizes potential side effects [1]. Currently, transdermal drug delivery (TDD) relies on topical products or transdermal patches. However, these methods face limitations due to the physio-chemical properties that impede their permeation through the lipophilic stratum corneum (SC) and their slow diffusion rate through the skin. To overcome these challenges, microneedles (MNs) have been developed. These microneedles penetrate the SC in a minimally invasive manner, creating "micro-conduits" that facilitate the transport of drugs into the skin tissue from the skin surface [2].

Herein, we have developed a microneedle array modified with molecularly imprinted polymers (MIPs) able to entrap bovine serum albumin (BSA) and insulin labeled with fluorescein isothiocyanate (FITC). Several MIPs based on the co-polymerization of o-phenylendiamine and gallic acid (1:1, 1:3 and 1:10) were tested in order to ensure the formation of hydrogen bonds between the polymer and the target. The target release was triggered by an electrochemical and bioelectrochemical oxygen reduction reaction (ORR) occurring at the electrode surface [3].

References

1. Fakhraei Lahiji, S., Kim, Y., Kang, G., Kim, S., Lee, S., & Jung, H. Tissue interlocking dissolving microneedles for accurate and efficient transdermal delivery of biomolecules. Sci. rep. 9(1), 7886 (2019).
2. Oliveira, D., Correia, B. P., Sharma, S., & Moreira, F. T. C. Molecular imprinted polymers on microneedle arrays for Point of Care transdermal sampling and sensing of inflammatory biomarkers. ACS omega, 7(43), 39039-39044 (2022).
3. Bollella, P., Sharma, S., Cass, A. E. G., & Antiochia, R. Minimally‐invasive microneedle‐based biosensor array for simultaneous lactate and glucose monitoring in artificial interstitial fluid. Electroanalysis, 31(2), 374-382 (2019).