Lactate is an important intermediate of metabolic processes, which is formed during anaerobic respiration. Accumulation of this compound may indicate various diseases, including cancer, so detection of lactate is important from a medical point of view. We report on the novel electrochemical lactate biosensors based on Prussian blue nanoparticles.

Synthesis of Prussian blue nanoparticles was carried out by means of the reaction between potassium hexacyanoferrate (III), iron (III) chloride and hydrogen peroxide, followed by ultrasonic dispersing of the suspension. The size of nanoparticles was determined using dynamic light scattering analysis and further operations were conducted using particles with diameters ranging from 20 to 60 nm. Prussian blue modified sensors were prepared by depositing nanoparticles on the surface of screen-printed carbon electrodes. The quality of electroactive coating was tested using cyclic voltammetry. The immobilization of lactate oxidase was performed through drop-casting on the sensor surface of mixture containing enzyme, (3-aminopropyl)triethoxysilane and isopropyl alcohol. Thus, after the formation of the (3-aminopropyl)triethoxysiloxane membrane biosensors were ready for electrochemical lactate detection.

The apparent Michaelis constant and inactivation constant (assuming that inactivation is pseudo first order reaction) were calculated (0.29±0.03 mM and 1.5±0.3 ms^-1, respectively) and compared with values obtained for previously known biosensors based on Prussian blue films. The developed lactate biosensors are not inferior in characteristics to those previously known, while the manufacturing process is less laborious and more reproducible.

Obtained values also indicate that lactate biosensors based on Prussian blue nanoparticles and lactate oxidase have sufficient sensitivity and operational stability for analytical purposes in medical and biological researches.

Biosensor technology is a fast-growing area in biomedicine as the demand for rapid analysis is increasing nowadays. A significant problem that biosensors face is the degradability and failure of biosensor materials, mainly due to temperature, pH, or the state of applied stress. Innovative material design and synthesis methods are required to close the reusability gap for these devices. Moreover, new materials are needed to ensure a better and cheaper diagnosis, especially in countries where diagnostic equipment is not readily available. Self-healing materials, a novel class of smart materials, can repair themselves without external stimuli when damage occurs to the structure. Deformations can be self-healed, giving rise to multiple applications in biotechnology when constant diagnosis monitoring is needed. These materials are ideal for various applications, including flexible electronics and biosensors. This review summarizes the synthesis methods, properties, and applications of self-healing materials in biosensors. Furthermore, emphasis is given to the sustainability and environmental aspects of these materials.

Features of the interaction of biomolecules with organic, inorganic or carbon structures ultimately determine the performance of any biosensor. This is due to the fact that it determines whether the functions inherent in the biological molecule, the use of which is the goal of creating biosensors, will be preserved during immobilization within the sensitive layer. That is why the study of hybrid materials is such an important part in the development of effective biosensors. Composite nanostructured layers of biological molecules with nanobodies are also of significant interest from the point of view of their implementation in gas sensors, so-called “bio-sniffers”. Their adsorption properties depend on surface morphology, particle size, packing, etc. Since there are many ways to create the surface organization of nanostructures, these materials open up wide opportunities for the development of new sensor coatings with desired adsorption properties.

In recent years, thanks to the advances in chemistry, there has been a significant increase in interest in carbon structures such as fullerene which is an allotropic modification of carbon, in which carbon atoms are connected by single and double bonds to form a closed mesh with fused rings. Of particular interest is the interaction of labile biomolecules with rigid frameworks of spherical fullerenes of the C60 type. In this work, we studied the features of such structures based on ovalbumin molecules. As an object of comparison, similar layers of ovalbumin, but deposited on a pre-deposited film of a classical organic semiconductor, copper phthalocyanine (CuPc), were studied. For research, QCM resonators with a resonant frequency of 10 MHz were used. Fullerene and CuPc films were obtained by thermal deposition in a vacuum. Proteins were deposited on the surface of C60 and CuPc by the drop method, i.e., protein molecules were bound to the surface due to physical adsorption. The effect of saturated vapors of alcohol, water, isobutyl alcohol, acetone, cyclohexane and benzene on the response of QCM sensors with two types of surface coatings was studied.

The results of a comparative analysis of the obtained data made it possible to confirm our earlier statement that biological molecules are capable of significantly changing their mechanical properties under the action of certain analytes. A necessary condition for this is the preservation of their labile structure and the possibility of interaction with the corresponding analytes, leading to a change in their spatial configuration. The reasons for this effect may be associated with the peculiarities of the influence of these compounds both on the structure of the protein and on the features of its connection with carbon nanocages.

Miniaturized and integrated devices for fast determination of clinical biomarkers is of high demand in the current healthcare environment. In this work, we present a functionalized self-assembled monolayer (SAM) on the gold surface of a screen-printed electrode (AuSPE). The device was applied for uric acid (UA) detection, a biomarker associated with arthritis, diabetes mellitus, and kidney function. Prior to SAM formation AuSPE was subjected to pretreatment with KOH and Au electrodeposition to provide additional roughness to the substrate. The SAM was formed in the AuSPE/KOH/AuNPs surface by cysteamine method, which was carried out when working surface dipping in cysteamine solution at 20 mM for 24 hours, and rinsed with ethanol and milli-Q water, then uricase enzyme was immobilized through physical absorption, at room temperature with an average humidity percentage recorded of 86%, the duration of this process was 1 hour and the AuSPE/KOH/AuNPs/SAM/Uox biosensor was rinsed with phosphate saline buffer (PBS) and milli-Q water prior to the UA detection process. The physical and electrochemical characterization of AuSPE modification was carried out by Scanning Electron Microscopy (SEM) and Cyclic Voltammetry (CV). The calibrated data of the Au/KOH/AuNPs/SAM/Uox biosensor showed a linear relation in the range of 50 – 1000 µM, a sensibility of 0.1449 µA/[(µM)cm²], and a limit of detection (LOD) of 4.4669 µM. The Au/KOH/AuNPs/SAM/Uox also exhibited a good selectivity for UA in presence of ascorbic acid. Moreover, the methodology exhibited good reproducibility, stability, and sensitive detection of UA. This performance of the proposed biosensor is in good accordance with clinical needs, and can be compared with previous biosensors based on nanostructured surfaces of high fabrication complexity.

Here we describe a multianalyte biosensor platform for fluorescent analysis of different human state biomarkers (α-amylase, phenylalanine, glucose, lactate/pyruvate, alcohol) and some immunosuppressive drugs (cyclosporine A, tacrolimus, methotrexate, rapamycin) using chimeric PQQ- and natural NAD⁺-dependent enzymes. The principle of the approach is based on the analysis of the brightness of photography of the sensor plate taken with a smartphone camera and processed via ImageJ software. The brightness of the image correlates with the fluorescence intensity of the sensor’s spots which is produced by enzymatic reduction of phenazine methosulfate or its derivative used as a fluorescence probe at UV 356 nm irradiation, where the amount of the reduced dye depends on the concentration of the target analyte (the enzymatic substrate) in the tested sample. The sensor plate is composed of simple and cheap components, while the procedure of its preparation and usage is easy and does not require any specific skills or expensive instrumentation. The proposed sensor platform is characterized by a high selectivity and storage stability depending on the selectivity and stability characteristics of the used enzyme in an immobilized state. The proposed sensor platform could be used for precision quantitative analysis of a single (or several) analytes or used for simultaneous qualitative multianalyte assay of numerous of them via Boolean Logic Gates.

With an increase in the average age of the global population over the last several decades, glaucoma has become an important global health concern that claims the eyesight of many patients annually [1]. Glaucoma-induced neuron damage is irreversible, which means that early detection is necessary since patients are often not aware of vision loss until a very advanced stage of the disease [3]. One risk factor that is often indicative of glaucoma is an increase in a patient’s intraocular pressure (IOP) [2]. IOP is determined by the inflow and outflow of aqueous humor to the eye, which is subject to change throughout the day as a person moves; in fact, fluid flow can be 50% lower during sleeping hours [2]. Such large variations mean that it is not possible for a singular pressure measurement taken at one time of the day to embody the entirety of a patient’s unique IOP trends that could signify glaucoma development. Therefore, there is a need for continuous IOP monitoring for early detection of glaucoma.

Previously we had developed a soft contact lens sensor for IOP measurement using microfluidic sensing techniques [4]. This proposal aims to further that work by adding new feature designs to the lens to modify the local strength of the lens. Under IOP changes, the new added features will be deformed accordingly. Through the calibration of the features size and shape change, IOP will be determined. First, a finite element model will be developed in COMSOL with varying applied pressure between 10 and 35 mmHg. The maximum deformation of the designed features on the lens will be used to optimize the design, including feature location, size etc. Experimental testing will be conducted using porcine eyes. The performance of the new wearable sensor will be evaluated. This analysis will further the research of wearable lenses for intraocular pressure measurement to detect early onset glaucoma.

References

[1] S. Kingman, "Glaucoma is second leading cause of blindness globally," Bulletin of the World Health Organization, vol. 82, no. 11, pp. 887-888, Novemebr 2004.

[2] D. Križaj, H. Kolb, E. Fernandez and R. Nelson, "What is glaucoma?," in Webvision: The Organization of the Retina and Visual System, Salt Lake City, 2019.

[3] D. A. Lee and E. J. Higginbotham, "Glaucoma and its treatment: A review," American Journal of Health-System Pharmacy, vol. 62, no. 7, pp. 691-699, 2005.

[4] Campigotto, A., Leahy, S., Zhao, G., Campbell, R. J., & Lai, Y. (2019). Non-invasive intraocular pressure monitoring with contact lens. British Journal of Ophthalmology, https://doi.org/10.1136/bjophthalmol-2018-313714

This research paper presents a misaligned double gate junctionless Metal-Oxide-Semiconductor Field-Effect Transistor for label-free detection of biomolecules. The proposed biosensor combines the advantages of junctionless, double and misaligned gate MOSFETs, which results in improved sensitivity and selectivity for biological recognition. The results show that the proposed biosensor can effectively detect biomolecules and has the potential for use in various applications.

Biosensors have become an important tool in various fields, such as healthcare, environmental monitoring, and food safety, due to their ability to detect biomolecules. MOSFETs have been widely used as biosensors due to their less complex structure and easy to use. However, traditional MOSFETs have limitations in terms of sensing performance, and there is a need for improved designs that overcome these limitations.

The results of this study show that the proposed biosensor can effectively detect various biomolecules such as protein and DNA and has the potential for use in various applications such as healthcare, environmental monitoring, and food safety. The proposed biosensor design has the potential to revolutionize the field of biosensors. Its combination of improved sensitivity and selectivity makes it a valuable tool for various applications. The study also provides insight into the design and optimization of future MOSFET-based biosensors and opens up new avenues for research in this field.

In conclusion, this research paper presents a dielectric modulated novel misaligned double gate junctionless MOSFET-based biosensor promising improved sensing performance in various applications. The proposed design provides a valuable contribution to the field of biosensors and has the potential to revolutionize the way biomolecules are detected.

A custom handcrafted electrode design is proposed here to electrically stimulate dorsal column fibers of the spinal cord in parkinsonian rats. The primary purpose of this electrode is to alleviate motor symptoms in Parkinson’s disease under the assumption that SCS might suppress the aberrant beta-frequency synchronous corticostriatal oscillations, thus restoring neural activity in the primary cortex and dorsolateral striatum to a state observed prior to the onset of spontaneous locomotion. Biocompatible materials were chosen in order to build a fully functional implantable device. Due to limitations in the epidural space of the spinal cord, platinum foil was taken as the option to make the electric contacts. Under exhausting repeated cycles of electrical stimulation, Pt foil suffers mechanical deformations on its surface. This can lead to significant changes in contact topography, thus changing the electrical impedance and biocompatibility features. It is essential to evaluate if the whole construction of the electrode is compatible with the number of stimuli to be held on parkinsonian rats in future studies in order to shed light on a systematic therapy using SCS. Electrodes were undergone wettability and electrical impedance tests before and after 48 h of electrical stimulation done in saline solution 0.9% at a frequency of 100 Hz, and 1.6 mA intensity. The stimulation had a k = 1.90, found in platinum oxidation and tissue damage. A wettability test was performed to characterize the interaction of the contact angle before and after, where there was an increase in this angle after the stimulation test. An electrical impedance test has shown that electrochemical interactions caused an increase in impedance after the stimulation period.

Sustainable materials for the design of smart sensors are an emergent technology and desirable to minimize electronics' environmental impact. Herein, we proposed a bifunctional substrate of polylactic acid (PLA) and polyethylene glycol (PEG) prepared by the solution-blow spinning technique to design an electrochemical biosensor. The PLA/PEG nanofibers are degradable, free of waste, low-cost, and considered a sustainable material, making promising for electrochemical biosensors projection. The substrate was namely bifunctional because they were employed as support for screen-printed carbon electrodes (SPCE) and a matrix for covalently bounded glucose oxidase (GOx). The GOx was incorporated directly on PLA/PEG surface and was responsible to hydrogen peroxide production which is detected on the SPCE surface. Prussian Blue nanoparticles (PB) were electrodeposited on the SPCE surface to decrease the reduction potential of the hydrogen peroxide, allowing to perform the chronoamperometric measurements with a low applied potential of 0 V vs. Ag/AgCl directly in undiluted human urine and yielding a high selectivity toward interferent compounds. The current signals of amperometric response increased linearly between 0.5 and 5.5 mM of glucose at the linear regression of 1.9 × 10^–6 + 18.1 × 10^–4 C_glucose (M), R² = 0.998 and the detection limit estimated was 0.197 mM. The flexible, bifunctional platform showed a stable signal for 60 days, which is maybe because of the GOx immobilization on the PLA/PEG surface. The glucose biosensor was statistically equivalent to the commercial colorimetric kit. The use of PLA/PEG mat and the bifunctional architecture is an affordable and sustainable alternative for the design of a new generation of biosensors for clinical analyses.

Heavy metal ions, such as Lead (Pb), Chromium (Cr), Cadmium (Cd) etc. present a serious environmental threat when found in soil and water; thus their accurate and fast detection poses as a major challenge. Although several detection methods have been proposed in the literature, they are both expensive and time consuming. In this work we present a biosensing device for heavy-metal ion detection based on Platinum nanoparticles (Pt NPs) and DNAzymes. The biosensors feature two distinctive DNAzymes species with different chemical modification groups (i.e thiol and amino modified), that enable their attachment on the Pt NP layer.

The bio-sensing devices were characterized by measuring changes in resistance using a Keithley 2400 multimeter, under a 1 V bias. As a first step, buffer solution was drop-casted on top of the bio-sensors; this step was repeated until device resistance became immune to any further buffer addition. After the buffer-stabilization steps, a buffer solution containing a known heavy-metal ion concentration was drop-casted on the sensor, resulting in an increase in device resistance in accordance with the mechanism discussed in previous publicatios of this group. In this study, we compare the sensitivity of the two different DNAzymes for varying Pb²⁺ concentrations. Both techniques present a linear response range, for maximum concentrations of 225 nM and 250 nM in the case of thiol and amino modified DNAzymes respectively. The devices also exhibit a low limit of detection (LoD) of 25 nM, in agreement with the permitted levels of Pb²⁺ for the EU. Finally, thiol modified DNAzymes showcase higher sensitivity when compared to the amino modified DNAzymes; this can be related to the variations between the two chemical modifications and the quality of their attachment on the NP layer