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1H magnetic resonance imaging (MRI) has established itself as a key diagnostic technique, affording the visualization of brain anatomy, blood flow, activity and connectivity. The detection of other atoms (e.g. 19F, 23Na, 31P), so called hetero-nuclear MRI and spectroscopy (MRS), provides investigative avenues that complement and extend the richness of information that can be gained from 1H MRI. Especially 19F MRI is increasingly emerging as a multi-nuclear (1H/19F) technique that can be exploited to visualize cell migration and trafficking. The lack of a 19F background signal in the brain affords an unequivocal detection suitable for quantification. Fluorine-based contrast material can be engineered as nanoemulsions, nanocapsules, or nanoparticles to label cells in vitro or in vivo. Fluorinated blood substitutes, typically nanoemulsions, can also carry oxygen and serve as a theranostic in poorly perfused brain regions. Brain tissue concentrations of fluorinated pharmaceuticals, including inhalation anesthetics (e.g. isoflurane) and anti-depressants (e.g. fluoxetine), can also be measured using MRS. However, the low signal from these compounds provides a challenge for imaging. Further methodological advances that accelerate signal acquisition (e.g. compressed sensing, cryogenic coils) are required to expand the applications of 19F MR imaging to, for instance, determine the regional pharmacokinetics of novel fluorine-based drugs. Improvements in 19F signal detection and localization, combined with the development of novel sensitive probes, will increase the utility of these multi-nuclear studies. These advances will provide new insights into cellular and molecular processes involved in neurodegenerative disease, as well as the mode of action of pharmaceutical compounds.

The interaction of explosion-induced blast waves with the head (i.e., a direct mechanism) or with the torso (i.e., an indirect mechanism) presumably causes traumatic brain injury. However, the understanding of the potential role of each mechanism in causing this injury is still limited. To address this knowledge gap, we characterized the changes in the brain tissue of rats resulting from the direct and indirect mechanisms at 24 h following blast exposure. To this end, we conducted separate blast-wave exposures on rats in a shock tube at an incident overpressure of 130 kPa, while using whole-body, head-only, and torso-only configurations to delineate each mechanism. Then, we performed histopathological (silver staining) and immunohistochemical (GFAP, Iba-1, and NeuN staining) analyses to evaluate brain-tissue changes resulting from each mechanism. Compared to controls, our results showed no significant changes in torso-only-exposed rats. In contrast, we observed significant changes in whole-body-exposed (GFAP and silver staining) and head-only-exposed rats (silver staining). In addition, our analyses showed that a head-only exposure causes changes similar to those observed for a whole-body exposure, provided the exposure conditions are similar. In conclusion, our results suggest that the direct mechanism is the major contributor to blast-induced changes in brain tissues.

The registration of the mass spectrometry imaging (MSI) data with mouse brain tissue slices from the atlases could perform automatic anatomical interpretation, and the comparison of MSI data in particular brain regions from different mice could be accelerated. However, the current registration of MSI data with mouse brain tissue slices is mainly focused on the coronal. Although the sagittal plane is able to provide more information about brain regions on a single histological slice than the coronal, it is difficult to directly register the complete sagittal brain slices of a mouse as a result of the more significant individualized differences and more positional shifts of brain regions. Herein, by adding the auxiliary line on the two brain regions of central canal (CC) and cerebral peduncle (CP), the registration accuracy of the MSI data with sagittal brain slices has been improved (∼2-5-folds for different brain regions). Moreover, the histological sections with different degrees deformation and different dyeing effects have been used to verify that this pipeline has a certain universality. Our method facilitates the rapid comparison of sagittal plane MSI data from different animals and accelerates the application in the discovery of disease markers.

Oleoylethanolamide is an endogenous molecule with neuroprotective effects. It has been reported that exogenous oleoylethanolamide can be administered therapeutically, but the confounding presence of the endogenous molecule has led to conflicting reports regarding the mechanisms of the effects and highlights a need for an adequate methodology to differentiate them. We have developed a liquid chromatography-tandem mass spectrometry method to study oleoylethanolamide in rat plasma and brain using a 13 C-labeled isotope, 13 C-oleoylethanolamide. 13 C-oleoylethanolamide was extracted using a liquid-liquid extraction employing acetonitrile and tert-butyl methyl ether (1:4). Analysis was performed using a gradient with a total run time of 12 min. 13 C-oleoylethanolamide, d4 -oleoylethanolamide (internal standard), and 12 C-oleoylethanolamide (endogenous background) eluted simultaneously at 1.64 min. The method was validated for specificity, sensitivity, accuracy, and precision and found to be capable of quantification within acceptable limits of ±15% over the calibration range of 0.39-25 ng/mL for the plasma and 1.17-75 ng/g for the brain. It was then applied to quantify 13 C-oleoylethanolamide over 90 min after intravenous administration of a solution (1 mg/kg) in rats. Results suggest that 13 C-oleoylethanolamide does not reach therapeutic concentrations in the brain, despite a relatively prolonged plasma circulation, suggesting that rapid degradation in the brain remains an obstacle to its clinical application to neurological disease.

We developed a method of reducing the background fluorescence of samples made from formalin-fixed and paraffin-embedded blocks of the brain of the second-trimester human fetuses. For reducing excess background fluorescence, the samples were subjected to photobleaching using an LED lamp with blue and red emission peaks in the range of visible spectrum in a construction of an original design. The decrease in the background autofluorescence was checked by measuring the intensity of the emitted background fluorescence of the samples and relative abundance of immunopositive structures after immunohistochemical staining. It was found that the proposed method reliably reduced the background fluorescence of the samples, which improved the quality of multicolor immunofluorescence images of the cerebral cortex.

Studies indicate that the soil, water and consequently foodstuffs in Serbia are significantly poor in zinc (Zn), and thus, it is likely that there is a Zn deficiency in the Serbian population. This study examined the Zn status in multiple clinical samples, including body fluids (serum, cerebrospinal fluid), whole blood and Zn-rich solid tissues (thyroid and brain tissue). Differences between sex and age were also considered, and comparative analysis of Zn status with other world populations was performed. Serum samples from a large number of Serbian adults approximately had twofold lower Zn amounts when compared to other populations. A similar trend was obtained for whole blood. Males had significantly higher amounts of Zn in serum, whole blood and thyroid tissue samples than females. Higher amounts of Zn were observed in the group older than 50 years. Importantly, in thyroid and brain tissues, Zn was 10- and 20-fold lower, respectively, than reported in the literature. Our results indicate that the population in Serbia could be considered Zn deficient. Therefore, adequate oral Zn supplementation and/or foodstuff fortification should be considered to prevent the deleterious effects caused by Zn deficiency.

Proteomic investigations of Alzheimer’s and Parkinson’s disease have provided valuable insights into neurodegenerative disorders. Thus far, these investigations have largely been restricted to bottom-up approaches, hindering the degree to which one can characterize a protein’s “intact” state. Top-down proteomics (TDP) overcomes this limitation; however, it is typically limited to observing only the most abundant proteoforms and of a relatively small size. Therefore, fractionation techniques are commonly used to reduce sample complexity. Here, we investigate gas-phase fractionation through high-field asymmetric waveform ion mobility spectrometry (FAIMS) within TDP. Utilizing a high complexity sample derived from Alzheimer’s disease (AD) brain tissue, we describe how the addition of FAIMS to TDP can robustly improve the depth of proteome coverage. For example, implementation of FAIMS with external compensation voltage (CV) stepping at −50, −40, and −30 CV could more than double the mean number of non-redundant proteoforms, genes, and proteome sequence coverage compared to without FAIMS. We also found that FAIMS can influence the transmission of proteoforms and their charge envelopes based on their size. Importantly, FAIMS enabled the identification of intact amyloid beta (Aβ) proteoforms, including the aggregation-prone Aβ(1–42) variant which is strongly linked to AD. Raw data and associated files have been deposited to the ProteomeXchange Consortium via the MassIVE data repository with data set identifier PXD023607.

Immune checkpoint inhibitors targeting the PD-1/PD-L1 pathway have become a "game-changer" in the cancer treatment. However, none of the small molecular inhibitors has been approved yet. To explore the advantages and disadvantages of various scaffolds, different biological evaluations were performed on the three selected small inhibitors, namely Incyte-001, Incyte-011, and BMS-1001. In the HTRF assay, BMS-1001 showed the best binding activity for PD-L1 (IC50 = 0.9 nM) while Incyte-011 (IC50 = 5.293 nM) was twice more potent than the Incyte-001 (IC50 = 11 nM). Also, only Incyte-011 increased the IFN-γ production. Notably, the Incyte-001 exhibited the high-est cytotoxicity (EC50 = 1.635 μM). Interestingly, Incyte-001 (injected intravenously 2mg/kg) also displayed good blood-brain barrier permeability and reached a high concentration in the brain tissue. Finally, molecular docking and modeling studies suggested that the compounds bind in a pocket at the interface of two PD-L1 monomers. Overall, our work shows that PD-1/PD-L1 small molecular inhibitors have different biological characteristics depending on their unique skeletons, which can be further improved to better their clinical application.

Inorganic nanostructured materials such as silicon, carbon, metals, and metal oxides have been explored as matrices of low-background signals to assist the laser desorption/ionization (LDI) mass spectrometric (MS) analysis of small molecules, but their applications for imaging of small molecules in biological tissues remain limited in the literature. Titanium dioxide is one of the known nanoparticles (NP) that can effectively assist LDI MS imaging of low molecular weight molecules (LMWM). TiO2 NP is commercially available as dispersions, which can be applied using a chemical solution sprayer. However, aggregation of NP can occur in the dispersions and the aggregated NP can slowly clog the sprayer nozzle. In this work, the use of zinc oxide (ZnO) NP for LDI MS imaging is investigated as a superior alternative due to its dissolution in acidic pH. ZnO NP was found to deliver similar or better results in the imaging of LMWM in comparison to TiO2 NP. The regular acid washes were effective in minimizing clogging and maintaining high reproducibility. High-quality images of mouse sagittal and rat coronal tissue sections were obtained. Ions were detected predominately as Na+ or K+ adducts in the positive ion mode. The number of LMWM detected with ZnO NP was similar to that obtained with TiO2 NP, and only a small degree of specificity was observed.

Background: Estimation of the postmortem interval (PMI) is a pivotal task in forensic investigations. Methods relied on PM biochemical alteration of the compounds such as cadaverine (Cad) and putrescine (Put) can provide more accurate data about the exact PMI. Aim: To investigate the correlation between Cad and Put levels in human brain tissue, measured by gas chromatography-mass spectrometry (GC–MS), and the PMI, to see if they can be used as reliable indicators for PMI estimation. Methodology: Brain specimens were taken during autopsy of three male victims, who died by stab wounds. Autopsy was done within three hours after death (the moment of death was known). The fifteen brain specimens (five from each victim’s brain, according to a fixed time schedule to simulate progressive postmortem intervals), were prepared for injection into the GC–MS and the levels of Cad and Put in the brain tissue specimens were measured. Results: Both Cad and Put levels increased in the brain tissue samples as long as the PMI increased, and there was a statistically highly significant (p

The blood-brain barrier (BBB) comprises the interface between blood, brain and cerebrospinal fluid. Its primary function, which is mainly carried out by tight junctions, is to stabilize the tightly controlled microenvironment of the brain. To study the development and maintenance of the BBB, as well as various roles their intrinsic mechanisms that play in neurological disorders, suitable measurements are required to demonstrate integrity and functional changes at the interfaces between the blood and brain tissue. Markers and plasma proteins with different molecular weight (MW) are used to measure the permeability of BBB. In addition, the expression changes of tight-junction proteins form the basic structure of BBB, and imaging modalities are available to study the disruption of BBB. In the present review, above mentioned methods are depicted in details, together with the pros and cons as well as the differences between these methods, which maybe benefit research studies focused on the detection of BBB breakdown.

Summary Background Cerebral deposition of abnormally misfolded and aggregated alpha-synuclein (αSyn) is a neuropathological hallmark of Parkinson's disease (PD). Pathologically aggregated αSyn species of PD (αSynPD) can act, in a ‘prion-like’ manner, as proteinaceous nuclei (‘seeds’) which are capable of self-templated propagation. This has raised concerns that αSynPD seeds transmitted iatrogenically between humans may stimulate αSyn pathologies or clinically harmful effects in the recipients. Effective decontamination when reprocessing medical devices could significantly counteract such risks. Steam sterilization at 134°C is recommended as an essential pathogen inactivation step in many reprocessing guidelines for medical devices, and also shows effectiveness against prions, the self-propagating biological agents long thought to exhibit the highest resistance to steam sterilization. Methods This study examined the reduction in αSynPD seeding activity in brain tissue homogenates from patients with PD after steam sterilization at 134°C using a specifically adapted real-time quaking induced conversion assay. Findings Titres of approximately 1010 50% seeding doses per gram were detected in non-steam-sterilized caudate nucleus tissue of patients with PD by endpoint titration. Five minutes of steam sterilization reduced this titre by only 2.25 ± 0.15 decadic-logarithmic units, with an extension of the sterilization time to 90 min not causing additional inactivation. These findings reveal that αSynPD species are disease-associated biological agents with seeding activity that has higher resistance to steam sterilization than prions. Conclusion The remarkable heat resistance of αSynPD seeds calls for thoroughly validated cleaning and disinfection methods that reliably remove or inactivate possible contaminations of seeding-active αSyn aggregates when reprocessing medical devices.

Highlights • Cerebrocortical hypoxia-ischemia can be simulated in mouse cortical slices. • Tissue recovery is maximised by optimising the dissolved oxygen levels in the artificial cerebrospinal fluid. • Supplementing dissolved oxygen with oxygen nanobubbles does not support improved tissue recovery. • Oxygen in nanobubble form is not biologically available to cortical tissue., Hypoxic-ischaemic brain injury is a major cause of morbidity and mortality internationally. Using an in vitro isolated cortex model, this study investigated the optimal cerebrospinal fluid oxygenation parameters for rescuing metabolically challenged cortical tissue. In particular, we asked whether maximizing oxygen content with oxygen nanobubbles could support improved tissue recovery. Mouse cortical slices were metabolically starved, followed by recovery in artificial cerebrospinal fluid (aCSF) containing different levels of dissolved oxygen ranging from mean(SD) 2(0.5) to 39(1.0) mg/L; with and without oxygen nanobubbles. Tissue recovery was assessed by quantifying and comparing the amplitude, length, high frequency content and event frequency of seizure-like events generated in no-magnesium aCSF at the beginning and end of the protocol. In general, there was improved recovery with increasing oxygen content up to 25–34 mg/L. The outcome of slices recovered in nanobubbled aCSF was no different to conventionally oxygenated slices with similar dissolved oxygen content. Dissolved oxygen content above 34 mg/L afforded no additional benefit. In conclusion, aCSF dissolved oxygen content of approximately 30 mg/L is optimal for cortical tissue recovery from metabolic starvation, which is easily achievable using conventional oxygenation methods. Oxygen in the form of nanobubbles does not appear to be readily available for tissue oxidative processes in this model.

Gene expression studies are reported to be influenced by pre-analytical factors that can compromise RNA yield and integrity, which in turn may confound the experimental findings. Here we investigate the impact of four pre-analytical factors on brain-derived RNA: time-before-collection, tissue specimen size, tissue collection method, and RNA isolation method. We report no significant differences in RNA yield or integrity between 20 mg and 60 mg tissue samples collected in either liquid nitrogen or the RNAlater stabilizing solution. Isolation of RNA employing the TRIzol reagent resulted in a higher yield compared to isolation via the QIAcube kit while the latter resulted in RNA of slightly better integrity. Keeping brain tissue samples at room temperature for up to 160 min prior to collection and isolation of RNA resulted in no significant difference in yield or integrity. Our findings have significant practical and financial consequences for clinical genomic departments and other laboratory settings performing large-scale routine RNA expression analysis of brain samples.

This study investigated the inhibitory effect of Cyperus esculentus L. (raw and processed) tubers on Iron (Fe2+) induced lipid peroxidation and key enzymes linked with neurodegeneration in vitro. Ten grams of tiger nut tubers was weighed and added to 100 mL of distilled water (1:10 w/v), left for 24 h, filtered, centrifuged to obtain a clear supernatant and lyophilized. Activities of acetyl cholinesterase (AChE), butyryl cholinesterase (BChE), Fe2+-induced lipid peroxidation as well as antioxidants status as indicated by 2,2-azino-bis (3-ethylbenthiazoline-6-sulphonic acid radical scavenging ability and Fe chelation were evaluated. Raw tiger nut extracts inhibited activities of AChE and BChE in the brain tissue of rats (0 – 11.54 mg /mL) with EC50 = 3.599 mg /mL and 2.71 ± 0.01 mg /mL respectively, and increased antioxidant activity when compared with the processed tuber. Inhibition on these enzymes as well as prevention of Fe2+ induced lipid peroxidation may be the possible mechanism of action by which tiger nut prevents neurodegeneration.

Traumatic brain injury (TBI) is a health problem of global concern because of its serious adverse effects on public health and social economy. A technique that can be used to precisely detect TBI is highly demanded. Here, we report on a synchrotron radiation-based Fourier transform infrared (SR-FTIR) microspectroscopic imaging technique that can be exploited to identify TBI-induced injury by examining model mouse brain tissue slices. The samples were first examined by conventional histopathological techniques including hematoxylin and eosin (H&E) staining and 2,3,5-triphenyltetrazolium chloride staining and then spectroscopically imaged by SR-FTIR. SR-FTIR results show that the contents of protein and nucleic acid in the injured region are lower than their counterparts in the normal region. The injured and normal regions can be unambiguously distinguished from each other by the principle component analysis of the SR-FTIR spectral data corresponding to protein or nucleic acid. The images built from the spectral data of protein or nucleic acid clearly present the injured region of the brain tissue, which is in good agreement with the H&E staining image and optical image of the sample. Given the label-free and fingerprint features, the demonstrated method suggests potential application of SR-FTIR spectroscopic mapping for the digital and intelligent diagnosis of TBI by providing spatial and chemical information of the sample simultaneously.

Purpose MK6240 is a second-generation tau PET tracer designed to detect the neurofibrillary tangles in the brains of patients with Alzheimer’s disease (AD). The aim of the study was to characterize 3H-MK6240 in AD and control brain tissue and to compare its binding properties with those of first-generation tau PET tracers. Methods Saturation binding assays with 3H-MK6240 were carried out in the temporal and parietal cortices of AD brains to determine the maximum number of binding sites (Bmax) and the dissociation constants (Kd) at these sites. Competitive binding assays were carried out between 3H-MK6240 and unlabelled MK6240, AV-1451 (aka T807, flortaucipir) and THK5117, and between 3H-THK5351 and unlabelled MK6240. Regional binding studies with 3H-MK6240 were carried out in homogenates from six AD and seven control brains and, using autoradiography, on large frozen sections from two AD brains and one control brain. Results The saturation binding assays gave Bmax and Kd values of 59.2 fmol/mg and 0.32 nM in the temporal cortex and 154.7 fmol/mg and 0.15 nM in the parietal cortex. The competitive binding assays revealed two binding sites with affinities in the picomolar and nanomolar range shared by 3H-MK6240 and all the tested unlabelled compounds. There were no binding sites in common between 3H-THK5351 and unlabelled MK6240. Regional binding of 3H-MK6240 was significantly higher in AD brain tissue than in controls. Binding in brain tissue from AD patients with early-onset AD was significantly higher than in brain tissue from patients with late-onset AD. Binding of 3H-MK6240 was not observed in off-target regions. Autoradiography showed high regional cortical binding in the two AD brains and very low binding in the control brain. Conclusions 3H-MK6240 has a high binding affinity for tau deposits in AD brain tissue but also has different binding characteristics from those of the first-generation tau tracers. This confirms the complexity of tau tracer binding on tau deposits with different binding affinities for different binding sites.

The objective of the study was to evaluate the organ-specific features of the expression of protective proteins of the HSP family in response to prolonged dust exposure in an experiment.Material and methods. The experiments were performed on 60 male Wistar rats weighing 200-250 g. The animals were divided into groups: rats inhaled coal-rock dust in the priming dust chamber for 4 hours daily for 6 weeks (average concentration 50 mg/m3), and the control rats (they were in an equal volume chamber, where the same temperature and air exchange conditions were maintained, but without the supply of coal-rock dust). In the cytoplasmic fraction of the lungs, heart, liver, and brain, the levels of HSP72 and heme oxygenase-1 (HOx-1) were determined by Western blot analysis.Results. The prolonged exposure of coal-rock dust to the body changed the level of intracellular proteins HSP72 and HOx-1 in the lungs, heart, liver, and brain. An increase in both HSP72 and HOx-1 levels occurred in the lungs and brain tissue; a significant increase in HOx-1 was recorded in the heart and HSP72 in the liver. These data indicate the organ-specific expression of intracellular proteins during dust exposure to the body. The following molecular mechanisms are involved in the development of the response to prolonged inhalation of coal-rock dust: 1) in the lungs and brain - both stress (HSP72) and hypoxic (HOx-1) components; 2) in the heart - a hypoxic component, manifested by the intensive synthesis of HOx-1 throughout the study period; 3) in the liver - a stress component due to significant expression of HSP72, which is associated with the manifestation of a protective effect for both the organ itself and the body as a whole.Conclusion. The results obtained indicate the organ-specificity of the cellular response of the body to the prolonged exposure to industrial dust. A change in the expression level of HSP72 and HOx-1 characterizes the degree of protection of organs from damage caused by inhalation of coal-rock dust, which grows in the series as liver < heart < lungs and brain.

Back Ground: Cypermethrin (CPM) is non-systematic type II synthetic pyrethroid, commonly used for pest control in livestock, forestry, horticulture, household, public and animal health services, private homes, and animal husbandry. By scavenging free radicals and modulating antioxidant protection mechanism, plant phytochemicals (vitamin C and Curcumin) are known to exert their protective impact, Aim: The current research aimed to examine the ameliorative effect of combining curcumin with prevention of vitamin C against the toxic effects of cypermethrin. Method: Four groups of ten male rats each, –ve control, +ve control group (200 mg curcumin and 100 mg vit. C/ kg bw), cypermethrin alone (200 mg / Kg bw), and cypermethrin supplemented with the protective antioxidants orally intubated for 28 - days. Result: Oral cypermethrin induced a significant increase in MDA and PC in serum, liver and brain as the oxidant biomarkers. While the antioxidant biomarkers (CAT, GSH or SH protein) were significantly decreases in serum and brain tissues. The phase II biotransformation GST was increased significantly in brain and liver tissues. ATPase activity declined significantly in brain tissue only. Conclusion: we can deduce that, cypermethrin induce oxidative stress in serum and organs tissues of male rats and the protective role curcumin and vit. C was more evident on serum, brain than liver.

Background: Magnetic Resonance Spectroscopy (MRS) is a method for measuring or assessing changes in the chemical elements of brain tissue in abnormalities such as tumours, stroke, epilepsy, metabolic disorder, infections, and neurodegenerative disease. MRS sequences require techniques to suppress fat and water signals, so the value of metabolic elements such as NAA Choline, Creatine, Lipids, and Lactate not been covered by fat and water. The peak amplitude of metabolic elements in MRS depends on the parameter used in the MRS sequences especially TE. Some studies suggest that variation and combinations of TE can provide more complete information on metabolite element, and can even be used to grading tumour stages.Methods: Type of this research is a qualitative study with an observational approach. Data collection was conducted in June 2019 at Radiology Department with observation method, unstructured interview, and documentation related to Magnetic Resonance Spectroscopy procedures. Data processing and analysis are carried out descriptively related to the result of observation, interview, and documentation.Results: The Head MR Spectroscopy examination procedure is a follow-up procedure of contrast MRI of the head. The main metabolite elements assessed on MRS are NAA, Choline, and Creatine, while those calculated and analyzed are the Area Under Cover (AUC) Integrals which are a collection of NAA and Choline signals. MRS sequences use Multi Voxel Spectroscopy (MVS). Chemical Shift Imaging (CSI) is used to suppress fat and water signals. TE parameter used in MRS sequences is only intermediate 135 ms.

Objectives: An ultra-performance liquid chromatography tandem mass spectrometry (UPLC–MS/MS) assay has been developed and validated for the quantification of oxycodone in rat serum and brain tissue homogenates. Methods: A simple extraction method using methyl-t-butyl ether was used for sample extraction with oxycodone–D3 as an internal standard (IS). A Symmetry® C18 column (100 mm x 4.6 mm, 5 µm) connected to a Phenomenex Luna® guard column (4 x 3 mm, 5 µm) was used for chromatographic separation. The mobile phase was composed of a mixture of acetonitrile and 0.1 % formic acid in water (pH = 2.7) (15:85, v/v). The flow rate was 0.4 mL/min, the total run time was 5 min, and the injection volume was 10 µL. The column and autosampler temperatures were maintained at 60 °C and 25 °C, respectively. Results: The calibration curve for oxycodone was linear over the range of 10–2000 ng/mL. Oxycodone extraction recovery from rat serum and brain samples ranged from 90.78–105.85 % and 98.42–104.38 % with relative standard deviation (RSD) values of 0.94–3.87 % and 1.04–2.82 %, respectively. The inter-day accuracy values ranged from 87.67–104.83 %, while the intra-day accuracy values ranged from 86.95–105.67 %. Conclusion: This method can be used for the quantification of oxycodone in samples obtained from preclinical animal studies and has great promise for applications in the quantification of oxycodone in human biological matrices.

In the list of environmental pollutants, mercury is one of the first places. It is mercury, its inorganic and especially organic compounds belong to extremely toxic substances of the first class of danger.Mercury has been known since ancient times, it is mentioned in the writings of Aristotle, Theophrastus, Pliny the Elder, Vitruvius and other ancient scholars. The Latin name for this metal is “Hydrargium”, given to mercury by Greek physician Dioscorides (1st century B.C.), means in translation “silver water”. The most important and ancient in Ukraine is the Mykytiv mercury deposit, which was opened in 1879. and operated since 1885. Production of mercury until 1914 was 300–400 t/year (most of it was exported). After the revolution and the war it was slowly recovered (127 tons in 1926), in 1935–1940 it is annually brought to about 300 tons. After the Second World War, the Mykytiv deposit was built. Discovered in it reserves (up to a depth of 300 m) were evaluated in 6.000 tons in 1927, after deep drilling was introduced in the 1960s. they have increased slightly. In the world economy, mercury is widely used in the electrical engineering and instrument industry, laboratory and medical practice, in the production of chlorine/alkali, in agriculture (included in fertilizers), in small-scale mining of gold and silver and other fields. No other chemical element belonging to the first class of danger has such wide use in production processes, products, substances and such multivariate penetration into the organism (with air, food, water, through the skin) as mercury and its compounds. The main source of mercury poisoning is mercury vapor and dust of mercury compounds. The toxicity of metallic mercury is due to the fact that while inhaling its vapors more than 80 % of the mercury is absorbed by the brain, kidneys and other internal organs, leading to he devastating consequences primarily on the central nervous system and kidneys. Mercury semi withdrawal period from humans is from 35 to 96 days. The average semi withdrawal period from the blood is 65 days, from hair 72 days, in total from the organism - 76 days. A longer semi withdrawal period of mercury from the brain than from other organs has been recorded in experimental animal searches. In humans, high levels of mercury in brain tissue were detected 10 years after it ceased contact with a toxic substance. Mercury poisoning can be acute or chronic. In everyday life, most often find the second option.

Objective: In present study, we aimed to clarify effect of aging on the susceptibility of brain tissue to neurodegeneration induced by ischemia.Methods: Damage induced by oxygen-glucose deprivation...

External organic or inorganic objects (foreign bodies) that are inadvertently or purposefully placed in the human or animal tissues can trigger local tissue responses that aim at the elimination and/or segregation of foreign bodies from the tissue. The foreign body response (FBR) may have major implications for neurodegeneration associated with the formation of aberrant protein-based aggregates or plaques. The distinct physical features of the plaques, including high rigidity and varying surface properties, may trigger microglial mechanosensing of the plaque as a foreign body. The microglial FBR may have a dual function by promoting and/or suppressing the plaque driven neurodegeneration. Microglial contact with the plaque may trigger inflammatory activation of microglia and support microglia-driven neuronal damage. Conversely, persistent microglial activation may trigger the formation of a microglia-supported cell barrier that segregates and compacts the plaques thus preventing further plaque-induced damage to healthy neurons.

We evaluated oxyphytosterol (OPS) concentrations in plasma and various tissues of two genetically modified mouse models with either increased cholesterol (apoE KO mice) or increased cholesterol and plant sterol (PS) concentrations (apoExABCG8 dKO mice). Sixteen female apoE KO and 16 dKO mice followed the same standard, low OPS-chow diet. Animals were euthanized at 36 weeks to measure PS and OPS concentrations in plasma, brain, liver and aortic tissue. Cholesterol and oxysteml (OS) concentrations were analyzed as reference for sterol oxidation in general. Plasma campesterol (24.1 +/- 4.3 vs. 11.8 +/- 3.0 mg/dL) and sitosterol (67.4 +/- 12.7 vs. 4.9 +/- 1.1 mg/dL) concentrations were severely elevated in the dKO compared to the apoE KO mice (p < 0.001). Also, in aortic and brain tissue, PS levels were significantly elevated in dKO. However, plasma, aortic and brain OPS concentrations were comparable or even lower in the dKO mice. In contrast, in liver tissue, both PS and OPS concentrations were severely elevated in the dKO compared to apoE KO mice (sum OPS: 7.4 +/- 1.6 vs. 4.1 +/- 0.8 ng/mg, p < 0.001). OS concentrations followed cholesterol concentrations in plasma and all tissues suggesting ubiquitous oxidation. Despite severely elevated PS concentrations, OPS concentrations were only elevated in liver tissue, suggesting that OPS are primarily formed in the liver and plasma concentrations originate from hepatic spill-over into the circulation.

This work describes for the first time the fabrication and characterization of multicomponent interpenetrating networks composed of collagen I, hyaluronic acid, and poly(ethylene glycol) diacrylate for the 3D culture of human neural stem cells, astrocytes, and microglia. The chemical composition of the scaffolds can be modulated while maintaining values of complex moduli within the range of the mechanical performance of brain tissue (∼6.9 kPa) and having cell viability exceeding 84%. The developed scaffolds are a promising new family of biomaterials that can potentially serve as 3D in vitro models for studying the physiology and physiopathology of the central nervous system.

Flexible deep brain probes have been the focus of many research works and aims at achieving better compliance with the surrounding brain tissue while maintaining minimal rejection. Strategies have been explored to find the best way to implant a flexible probe in the brain, while maintaining its flexibility once positioned in the cortex. Here, we present a novel and versatile scalable batch fabrication approach to deliver ultra-thin and flexible penetrating neural probe consisting of a silk-parylene bilayer. The biodegradable silk layer provides a temporary and programmable stiffener to ensure ease of insertion of the ultrathin parylene-based flexible devices. The innovative and yet robust batch fabrication technology allows complete design freedom of the neural probe in terms of materials, size, shape and thickness. These results provide a novel technological solution for implanting ultra-flexible and ultrathin devices, which possesses great potential for brain research.

The presence of amyloid fibrils is a hallmark of more than 50 human disorders, including neurodegenerative diseases and systemic amyloidoses. A key unresolved challenge in understanding the involvement of amyloid in disease is to explain the relationship between individual structural polymorphs of amyloid fibrils, in potentially mixed populations, and the specific pathologies with which they are associated. Although cryo-electron microscopy (cryo-EM) and solid-state nuclear magnetic resonance (ssNMR) spectroscopy methods have been successfully employed in recent years to determine the structures of amyloid fibrils with high resolution detail, they rely on ensemble averaging of fibril structures in the entire sample or significant subpopulations. Here, we report a method for structural identification of individual fibril structures imaged by atomic force microscopy (AFM) by integration of high-resolution maps of amyloid fibrils determined by cryo-EM in comparative AFM image analysis. This approach was demonstrated using the hitherto structurally unresolved amyloid fibrils formed in vitro from a fragment of tau (297-391), termed ‘dGAE’. Our approach established unequivocally that dGAE amyloid fibrils bear no structural relationship to heparin-induced tau fibrils formed in vitro. Furthermore, our comparative analysis resulted in the prediction that dGAE fibrils are closely related structurally to the paired helical filaments (PHFs) isolated from Alzheimer’s disease (AD) brain tissue characterised by cryo-EM. These results show the utility of individual particle structural analysis using AFM, provide a workflow of how cryo-EM data can be incorporated into AFM image analysis and facilitate an integrated structural analysis of amyloid polymorphism.

The pathological origin of Alzheimer's disease (AD) is still shrouded in mystery, despite intensive worldwide research efforts. The selective visualization of β-amyloid (Aβ), the most abundant proteinaceous deposit in AD, is pivotal to reveal AD pathology. To date, several small-molecule fluorophores for Aβ species have been developed, with increasing binding affinities. In the current work, two organic small-molecule dioxaborine-derived fluorophores were rationally designed through tailoring the hydrophobicity with the aim to enhance the binding affinity for Aβ1-42 fibrils -while concurrently preventing poor aqueous solubility-via biannulate donor motifs in D-π-A dyes. An unprecedented sub-nanomolar affinity was found (K d = 0.62 ± 0.33 nM) and applied to super-sensitive and red-emissive fluorescent staining of amyloid plaques in cortical brain tissue ex vivo. These fluorophores expand the dioxaborine-curcumin-based family of Aβ-sensitive fluorophores with a promising new imaging agent. ispartof: Bioactive Materials vol:13 pages:239-248 ispartof: location:China status: published

There is increasing evidence of altered tissue mechanics in neurodegeneration. However, due to difficulties in mechanical testing procedures and the complexity of the brain, there is still little consensus on the role of mechanics in the onset and progression of neurodegenerative diseases. In the case of Alzheimer’s disease (AD), magnetic resonance elastography (MRE) studies have indicated viscoelastic differences in the brain tissue of AD and healthy patients. However, there is a lack of viscoelastic data from contact mechanical testing at higher spatial resolution. Therefore, we report viscoelastic maps of the hippocampus obtained by a dynamic indentation on brain slices from the APP/PS1 mouse model where individual brain regions are resolved. A comparison of viscoelastic parameters shows that regions in the hippocampus of the APP/PS1 mice are significantly stiffer than wild-type (WT) mice and have increased viscous dissipation. Furthermore, indentation mapping at the cellular scale directly on the plaques and their surroundings did not show local alterations in stiffness although overall mechanical heterogeneity of the tissue was high (SD~40%). Therefore, reported mechanical alterations at a tissue scale indicates global remodeling of the brain tissue structure.

Purpose Low-field (B-0 < 0.1 T) MRI has generated much interest as a means of increased accessibility via reduced cost and improved portability compared to conventional clinical systems (B-0 >= 1.5 Tesla). Here we measure MR relaxation times at 50 mT and compare results with commonly used models based on both in vivo and ex vivo measurements. Methods Using 3D turbo spin echo readouts, T-1 and T-2 maps of the human brain and lower leg were acquired on a custom-built 50 mT MRI scanner using inversion-recovery and multi-echo-based sequences, respectively. Image segmentation was performed based on a histogram analysis of the relaxation times. Results The average T-1 times of gray matter, white matter, and cerebrospinal fluid (CSF) were 327 +/- 10 ms, 275 +/- 5 ms, and 3695 +/- 287 ms, respectively. Corresponding values of T-2 were 102 +/- 6 ms, 102 +/- 6 ms, and 1584 +/- 124 ms. T-1 times in the calf muscle were measured to be 171 +/- 11 ms and were 130 +/- 5 ms in subcutaneous and bone marrow lipid. Corresponding T-2 times were 39 +/- 2 ms in muscle and 90 +/- 13 ms in lipid. Conclusions For tissues except for CSF, the measured T-1 times are much shorter than reported at higher fields and generally lie within the range of different models in the literature. As expected, T-2 times are similar to those seen at typical clinical field strengths. Analysis of the relaxation maps indicates that segmentation of white and gray matter based purely on T-1 or T-2 will be quite challenging at low field given the relatively small difference in relaxation times.

Development of new products for the prevention of traumatic brain injuries are mostly based on mechanical investigations. However, there is a demand for new and more sophisticated analyzes focusing on molecular levels to improve protective equipment. Recently we evaluated the mature protein laminin LN521 to find out the consequences to dynamic and semi-static impact and found substantial fragmentation and aggregation of the laminin structures. The objective in the present study was to analyze the effect of polymer materials to prevent the cell membrane protein Laminin from being denatured and, hence, reducing impacts to the head evaluated by using two different mechanical methods, denatured electrophoresis and electron microscopy. Thus, following dynamic impacts without and with the polymer materials the results showed a significant reduction of the force as well as the translational acceleration with up to over 50%. Also, in the present laboratory investigation the mature laminin was used following dynamic impact to find out if this molecule can serve as a complementary analyzer to mechanical methods when searching for optimal protective materials. The results showed that the polymer materials had the capacity to save the laminin structures from both fragmentation and aggregation as evaluated with denatured electrophoresis and electron microscopy. Therefore, proteins may complement today's calculation simulations and mechanical investigations in the search for improved protective systems to the skull bone and brain tissue. The present result shows that laminin structures may become a valuable method to further identify new structures on a molecular level in the search for improved protective materials to the brain tissue at physical exercise and at accidents.

Reactive oxygen species (ROS) produced by an inflammatory response in the brain are associated with various neurological disorders. To investigate ROS-associated neuroinflammatory diseases, fluorescent probes with practicality are in demand. We have investigated hypochlorous acid, an important ROS, in the brain tissues of neuroinflammation and maternal immune activation (MIA) model mice, using a new fluorescent probe. The probe has outstanding features over many known probes, such as providing two bright ratio signals in cells and tissues in deep-red/near-infrared wavelength regions with a large spectral separation, in addition to being strongly fluorescent, photo- and chemo-stable, highly selective and sensitive, fast responding, and biocompatible. We have found that the level of hypochlorous acid in the brain tissue of a neuroinflammatory mouse model was higher (2.7-4.0-fold) compared with that in normal brain tissue. Furthermore, the level of hypochlorous acid in the brain tissue of a MIA mouse model was higher (1.2-1.3-fold) compared with that in the normal brain tissue. The "robust" probe provides a practical tool for studying ROS-associated neurological disorders.

Magnetic Resonance Spectroscopy (MRS) allows for the non-invasive quantification of neurochemicals and has the potential to differentiate between the pathologically distinct diseases, multiple sclerosis (MS) and AQP4Ab-positive neuromyelitis optica spectrum disorder (AQP4Ab-NMOSD). In this study we characterised the metabolite profiles of brain lesions in 11 MS and 4 AQP4Ab-NMOSD patients using an optimised MRS methodology at ultra-high field strength (7T) incorporating correction for T2 water relaxation differences between lesioned and normal tissue.\ud \ud MS metabolite results were in keeping with the existing literature: total N-acetylaspartate (NAA) was lower in lesions compared to normal appearing brain white matter (NAWM) with reciprocal findings for myo-Inositol. An unexpected subtlety revealed by our technique was that total NAA differences were likely driven by NAA-glutamate (NAAG), a ubiquitous CNS molecule with functions quite distinct from NAA though commonly quantified together with NAA in MRS studies as total NAA. Surprisingly, AQP4Ab-NMOSD showed no significant differences for total NAA, NAA, NAAG or myo-Inositol between lesion and NAWM sites, nor were there any differences between MS and AQP4Ab-NMOSD for a priori hypotheses. Post-hoc testing revealed a significant correlation between NAWM Ins:NAA and disability (as measured by EDSS) for disease groups combined, driven by the AP4Ab-NMOSD group.\ud \ud Utilising an optimised MRS methodology, our study highlights some under-explored subtleties in MRS profiles, such as the absence of myo-Inositol concentration differences in AQP4Ab-NMOSD brain lesions versus NAWM and the potential influence of NAAG differences between lesions and normal appearing white matter in MS.

Apart from a role as a key regulator of calcium/phosphate homeostasis, vitamin D (Vit D) is suggested to be a potential player in nervous system growth and function. This study aimed to assess the impacts of Vit D administration against memory impairment, oxidative damage and acetylcholinesterase (AchE) overactivity caused by hypothyroidism in juvenile rats. The animals were randomly grouped as: 1) Control; 2) Hypothyroid; 3) Hypothyroid-Vit D 100 and 4) Hypothyroid-Vit D 500. Propylthiouracil (PTU) was added to their drinking water (0.05%) for 6 weeks and Vit D (100 or 500 IU/kg) treatment was daily performed by gavage. Morris water maze (MWM) and passive avoidance (PA) tests were performed. The brains were removed under deep anesthesia, then the hippocampal and cortical tissues were separated to assess biochemical parameters. Hypothyroidism was significantly associated with learning and memory impairment in MWM and PA tests. Hypothyroidism also elevated acetylcholinesterase (AChE) activity and malondialdehyde (MDA) content, while it reduced thiol content and superoxide dismutase (SOD) activity in the brain. Treatment with Vit D recovered hypothyroidism-induced cognitive impairment and improved memory performance in MWM and PA tasks. On the other hand, Vit D alleviated AChE activity and MDA level, whereas increased SOD activity and thiol content in the hippocampal and cortical tissues. In conclusion, these outcomes suggest that oral consumption of Vit D may play a protective role against memory dysfunction caused by hypothyroidism by inhibiting AChE activity and oxidative stress in the brain.

This short commentary is intended to briefly discuss the benefits of plant secondary metabolites against brain tissue injury promoted by oxidative stress. Henceforth, the physicochemical features and biological activities of phytocomponents were assessed based on literature reports, which showcased their thermodynamic feasibility to reduce reactive oxygen species. It was strongly hinted that secondary metabolites possessing antioxidant potential may be of use in the therapeutics against neurodegenerative disorders owing to free radical scavenging, what hinders further damage to brain tissue.

Mass spectrometry (MS) has emerged as a valuable technology for molecular and spatial evaluation of biological samples. Ambient ionization MS techniques, in particular, allow direct analysis of tissue samples with minimal pretreatment. Here, we describe the design and optimization of an alternative ambient liquid extraction MS approach for metabolite and lipid profiling and imaging from biological samples. The system combines a piezoelectric picoliter dispenser to form solvent nanodroplets onto the sample surface with controlled and tunable spatial resolution and a conductive capillary to directly aspirate/ionize the nanodroplets for efficient analyte transmission and detection. Using this approach, we performed spatial profiling of mouse brain tissue sections with different droplet sizes (390, 420, and 500 μm). MS analysis of normal and cancerous human brain and ovarian tissues yielded rich metabolic profiles that were characteristic of disease state and enabled visualization of tissue regions with different histologic composition. This method was also used to analyze the lipid profiles of human ovarian cell lines. Overall, our results demonstrate the capabilities of this system for spatially controlled MS analysis of biological samples.

Previously we have shown that nM ouabain-induced activation of cAMP-dependent Na/Ca exchange in reverse (R) mode in cell membrane has age-dependent weakening hydration effect on heart muscle and brain tissues and such Na/Ca exchange is characterized by quantum mechanical sensitivity. As in biological experiments radioactive 45Ca is used for the study of cold 40Ca exchange in cells and organisms, in the present work, the age-dependent effect of physiological solution (PS) containing either 40Ca or 45Ca on tissue hydration in different experimental conditions was studied in order to evaluate the bioequivalence of these two forms of Ca. The obtained data indicate that the intraperitoneal injections of 40Ca PS and 45Ca PS leading to activation of RNa/40Ca and RNa/45Ca exchanges, respectively, have different age-dependent effects on heart muscle and brain tissue hydration. As in myocyte membrane, the Na/Ca exchange is more expressed than in neuronal membrane, the age-dependent heart muscle hydration is more sensitive to quantum properties of Ca than brain tissue hydration. The [45Ca]i, in contrary to [40Ca]i, has age-dependent weakening and stabilizing effect on tissue hydration and makes the latter insensitive to ouabain. The obtained data bring us to a strong conclusion that RNa/Ca exchange has quantum mechanical properties and in biological experiments radioactive 45Ca cannot be used for adequate estimation of the functional activity of 40Ca ions in cells and organisms.

Оксидативный стресс играет ведущую роль в патогенезе некоторых заболеваний печени, так как способствует усилению образования активных форм кислорода и интенсификации перекисного окисления липидов (ПОЛ). Этот механизм лежит в основе перестройки биологических мембран, регуляции их состава и основных функций, среди которых основой жизнеобеспечения является барьерная функция. Перекисное окисление липидов обеспечивает в организме фаго- и пиноцитоз, а также синтез многих биологически активных соединений, среди которых простагладины, лейкотриены, холестерин, прогестерон. Центральным защитным звеном от экспонентного роста свободных радикалов является система глутатиона, включающая в себя глутатион и ферменты его метаболизма: каталазу, глутатионредуктазу, глутатионтрансферазу, глутатионпероксидазу. Дисбаланс между интенсификацией свободнорадикального окисления, вызываемого активными формами кислорода, и активностью защитной антиоксидантной системы организма приводит к серьезным нарушениям: дезорганизацией клеточных структур, изменениями их функциональной активности. В статье представлено исследование взаимосвязей распределения концентраций ферментов системы ПОЛ-АО в сыворотке крови и тканях печени белых беспородных крыс. С помощью коэффициентов Кендела Тау, Спирмена и гамма корреляции выявлено, что при концентрации СОД, ГП и МДА в организме животных в пределах физиологической нормы достоверно определяется слабая прямая корреляционная связь между активностью этих ферментов в сыворотке крови и тканях печени. При концентрации диеновых конъюгатов (ДК) в организме крыс в пределах физиологической нормы достоверно определяется слабая обратная корреляционная связь между активностью ДК в сыворотке крови и тканях печени.

It is known that inhalation anesthetics are effective in the formation of oxidative stress and free radicals. The purpose of this study is to investigate these effects of desflurane and to detect changes in different flows. The rats were divided into three groups (10 mice/group). The first group was the control group. In the second group, mice were sedated with ketamine and given desflurane at a concentration of 6% in a 100% oxygen flow at a flow rate of 8 lt / min in a glass box for 20 minutes. The third group was comprised of ketamine-sedated mice that were given desflurane at a concentration of 6% in a 100% oxygen flow at a flow rate of 2 lt/min in a glass box for 20 minutes. Biochemical parameters were measured using commercial kits. Serum, brain, liver tissue MDA and SOD levels were significantly higher in the high flow group than in the control and low flow group. Serum GPx levels were significantly lower in the high flow group compared to both groups. ADMA levels in the serum, liver, and brain tissue were significantly higher in the high flow group. There was no significant difference in serum 8-OHdG levels between all three groups. Brain and liver tissue 8-OHDG levels were higher in both groups than control group. It has been observed that the use of low flow fresh gas even in the same concentrations of desflurane anesthesia models decreases oxidative stress whereas the use of high flow increases oxidative stress.

In this study, it was aimed to research the effects of cutaneous and oral exposure to aluminum nanoparticles (Al-NPs) and magnesium nanoparticles (Mg-NPs) on the brain tissue, which is vitally important in terms of its structure and functions. The study was performed on Wister-Albino rats, which were divided into 10 groups, such as control groups (groups 1 and 2), groups, to which Al and Mg NPs were applied as 500 mg/kg and 1500 mg/kg orally (groups 3-6) and 1000 mg/kg and 2000 mg/kg cutaneously (groups 7-10). The dosages were administered as a single dose. While brain tissue and serum MDA levels as well as brain tissue TNF-α and IL-6 levels have significantly increased in the group, to which 1500 mg/kg Mg-NPs was applied orally, significant decreases have also been observed in brain tissue GPX and SOD levels of the same group. Additionally, meaningful decreases in brain tissue SOD levels and significant increases in TNF-α and IL-6 levels have been observed in the group, to which 1500 mg/kg Al-NP was applied orally. On the other hand, it was found that brain tissue GPX and SOD levels of the group, to which 2000 mg/kg Mg-NP was applied cutaneous, have been decreased significantly. Histopathological examinations have also supported these findings. At the end of the study, it was observed that the toxic effect of Al and Mg NPs has varied, depending on the application method, dosage and duration.

Background: Renal ischemia-reperfusion (RIR) is a common clinical injury that affects the function of other remote organs such as the brain by initiating a cascade of complex and wide-ranging inflammatory responses. RIR also follows a different course in men and women. Since there is little information on the effect of RIR on the brain as a sensitive organ in both males and females, the present research was performed to investigate the effect of gender on RIR-induced brain tissue alterations in adult rats. Materials and Methods: In this study, 28 Wistar rats (14 female and 14 male rats) weighing 200 ± 20 g were divided into the following groups: 1- male sham (MS), 2- female sham (FS), 3- male ischemia (MI) with 3-hour reperfusion (ISC3hr), and 4- Female ischemia (FI) with 3-hour reperfusion (ISC3hr). Bilateral renal ischemia was induced for 45 minutes and blood samples were taken after reperfusion for the measurements of serum blood urea nitrogen (BUN), creatinine (Cr), malondialdehyde (MDA), and nitrite levels. The left kidney was removed for evaluation of MDA and tissue nitrite levels. Right kidney and brain tissue underwent histological examination. Results: Serum BUN level increased in both genders. Serum nitrite level was significantly different between both genders, meaning that it was increased in the female rats as compared to male ones. Overall brain tissue damage was significantly increased in males compared to females. Conclusion: RIR has an effect on the function and tissue of kidney and brain in both genders. Female rats are more susceptible to the nitric oxide system than the male ones. This study showed that male brain tissue was more susceptible to RIR. Therefore, gender is one of the important factors that should be considered in clinical treatments.

A simple and sensitive spectroflourimetric method has been proposed for the determination of the antitumor agent letrozole in tablets, spiked human plasma, and rat brain tissue homogenates. Our method involves measuring the native fluorescence of letrozole at 590 nm upon excitation at 239 nm as indicated upon scanning its three-dimensional spectrum. Various experimental parameters were intensively studied and the method was validated as per ICH guidelines. The calibration curve was linear over the concentration range 5–160 ng/mL, with limit of detection 1.36 ng/mL. It was successfully applied to the analysis of letrozole in Femara® tablets with mean recovery 99.35 ± 1.49% and was further applied to study the alkaline degradation kinetics of letrozole. The pseudo first-order rate constant and half-life were calculated. Moreover, successful application of our proposed procedure was carried out on spiked human plasma and rat brain tissue samples. Linear ranges were found to be 5–30 and 10–130 ng/mL, with detection limits 1.25 and 1.71 ng/mL for plasma and brain samples, respectively. Thanks to the method's simplicity, selectivity, and high sensitivity, it can be used for routine analysis in quality control laboratories and for further clinical investigations involving letrozole.

Implantable electronics are essential for electrophysiological recording at single-neuron and sub-millisecond resolution in the fields of neuroscience and neuroprosthesis. Advances in nano/microfabrication techniques offer new and exciting opportunities for the development of high-density implantable electronics. However, the mechanical mismatch between microfabricated rigid electronics and soft brain tissues has been shown to cause inflammatory responses, leading to signal degradation during chronic recording. Recently, flexible electronics with improved mechanical compatibility to brain tissues have been intensively investigated to improve the performance of chronic neural recordings. Flexible electronics can form conformal interfaces with brain tissue, resulting in minimized inflammatory responses and stable signal recordings. In addition, ultra-small, high-density, and multiple-functionality are also desirable features of flexible neural electronics. In this review, we highlight recent progress in microfabricated flexible electronics for in vivo brain activity recordings, and focus on structural design, brain/tissue interface, implantation method, minimization, and multifunctional integration.