Artificial Cerebrospinal Fluid Research Articles

Acute brain slice elastic modulus decreases over time

A common benchmark in the brain tissue mechanics literature is that the properties of acute brain slices should be measured within 8 h of the experimental animal being sacrificed. The core assumption is that—since there is no substantial protein degradation during this time—there will be no change to elastic modulus. This assumption overlooks the possibility of other effects (such as osmotic swelling) that may influence the mechanical properties of the tissue. To achieve consistent and accurate analysis of brain mechanics, it is important to account for or mitigate these effects. Using atomic force microscopy (AFM), tissue hydration and volume measurements, we find that acute brain slices in oxygenated artificial cerebrospinal fluid (aCSF) with a standard osmolarity of 300 mOsm/l experience rapid swelling, softening, and increases in hydration within the first 2 hours after slicing. Reductions in elastic modulus can be partly mitigated by addition of chondroitinase ABC enzyme (CHABC). Increasing aCSF osmolarity to 400 mOsm/l does not prevent softening but may hasten equilibration of samples to a point where measurements of relative elastic modulus are consistent across experiments.

Tissue oxygen partial pressure as a viability metric for ex vivo brain tissue slices

BackgroundDespite the prevalent use of the ex vivo brain slice preparation in neurophysiology research, a reliable method for judging tissue viability ― and thus suitability of a slice for inclusion in an experiment ― is lacking. The utility of indirect electrophysiological measures of tissue health is model-specific and needs to be used cautiously. In this study, we verify a more direct test of slice viability, based on tissue oxygen consumption rate. New methodWe hypothesised that the minimum intra-slice partial pressure of oxygen (pO2min) would correlate with tissue oxygen consumption rate, providing an accessible method for reliably assessing tissue viability status. Using mouse brain cortex slices, we measured tissue oxygen consumption rate using a Fick’s law diffusion–consumption model applied to full intra-tissue pO2 profiles and compared this to pO2min and 2,3,5-triphenol tetrazolium chloride (TTC) viability staining. ResultsTissue pO2min correlated strongly with oxygen consumption rate in both neurophysiological active and quiescent tissue (in “no-magnesium” and “normal” artificial cerebrospinal fluid, respectively) (R2 =49.7% and 42.1%, respectively). Both correlated with TTC viability stain. Oxygen consumption rate was positively related to the frequency of seizure-like event activity in no-magnesium artificial cerebrospinal fluid (R2 = 44.8%). Comparison with existing methodsWhile measurement of tissue oxygen levels and oxygen consumption is not new, intra-tissue pO2min is a novel approach to assess brain slice viability. ConclusionThe results confirm that tissue oxygen minimum pO2min is a robust metric for estimating tissue viability status — the lower the pO2min, the healthier the tissue.

Anthocyanin attenuates high salt-induced hypertension via inhibiting the hyperactivity of the sympathetic nervous system

ABSTRACT Background Anthocyanin plays a protective role in cardiovascular disease through antioxidant effect. Whether anthocyanin can reduce salt-induced hypertension and the related mechanisms remain unclear. Methods Chronic infusion of vehicle (artificial cerebrospinal fluid, aCSF, 0.4 μL/h) or anthocyanin (10 mg/kg, 0.4 μL/h) into bilateral paraventricular nucleus (PVN) of Sprague-Dawley rats was performed. Then, the rats were fed a high salt diet (8% NaCl, HS) or normal salt diet (0.9%, NaCl, NS) for 4 weeks. Results High salt diet induced an increase in blood pressure and peripheral sympathetic nerve activity (increased LF/HF and decreased SDNN and RMSSD), which was accompanied by increased reactive oxygen species (ROS) production and angiotensin II type-1 receptor (AT1R) expression and function in the PVN. Moreover, the NOD-like receptor protein 3 (NLRP3) and related inflammatory proteins (caspase-1) expression, the pro-inflammatory cytokine levels including IL-1β and TNF-α were higher in PVN of rats with a high salt diet. Bilateral PVN infusion of anthocyanin attenuated NLRP3-dependent inflammation (NLRP3, caspase-1, IL-1β and TNF-α) and ROS production, reduced AT1R expression and function in PVN and lowered peripheral sympathetic nerve activity and blood pressure in rats with salt-induced hypertension. Conclusions Excessive salt intake activates NLRP3-dependent inflammation and oxidative stress and increased AT1R expression and function in the PVN. Bilateral PVN infusion of anthocyanin lowers peripheral sympathetic nerve activity and blood pressure in rats with salt-induced hypertension by improvement of expression and function of AT1R in the PVN through inhibiting NLRP3 related inflammatory and oxidative stress.

Surface‐enhanced Raman spectroscopy combined with multivariate analysis for the detection and differentiation of dopamine and DOPAC in cerebrospinal fluid

AbstractDopamine (DA) is a vital neurotransmitter for brain functions, including pleasure, memory, motivation, and movement control. Dopaminergic neuron degradation is correlated to neurological disorders such as Parkinson's disease, and changes in DA concentration are related to mental health disorders. Currently, the gold standard for monitoring DA concentrations in the brain is electrochemistry. However, although electrochemistry has high sensitivity, it has low specificity for molecules with similar molecular structures, such as DA and its metabolites. Here, we demonstrate that surface‐enhanced Raman spectroscopy (SERS), a vibrational spectroscopy that provides molecule‐specific information with excellent sensitivity, requires small sample sizes/volumes, and is non‐destructive, is optimal for the detection and differentiation of DA and its metabolites. We show that SERS combined with multivariate analysis allows for the detection and differentiation of DA and its metabolites, including 3‐O‐methyldopamine (3‐OMD), homovanillic acid (HVA), 3,4‐dihydroxyphenylacetic acid (DOPAC), and 3‐methoxytyramine (3‐MT) at physiologically relevant concentrations in artificial cerebrospinal fluid (aCSF).

Effect of isolated intracranial hypertension on cerebral perfusion within the phase of primary disturbances after subarachnoid hemorrhage in rats.

Elevated intracranial pressure (ICP) and blood components are the main trigger factors starting the complex pathophysiological cascade following subarachnoid hemorrhage (SAH). It is not clear whether they independently contribute to tissue damage or whether their impact cannot be differentiated from each other. We here aimed to establish a rat intracranial hypertension model that allows distinguishing the effects of these two factors and investigating the relationship between elevated ICP and hypoperfusion very early after SAH. Blood or four different types of fluids [gelofusine, silicone oil, artificial cerebrospinal fluid (aCSF), aCSF plus xanthan (CX)] were injected into the cisterna magna in anesthetized rats, respectively. Arterial blood pressure, ICP and cerebral blood flow (CBF) were continuously measured up to 6 h after injection. Enzyme-linked immunosorbent assays were performed to measure the pro-inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) in brain cortex and peripheral blood. Silicone oil injection caused deaths of almost all animals. Compared to blood, gelofusine resulted in lower peak ICP and lower plateau phase. Artificial CSF reached a comparable ICP peak value but failed to reach the ICP plateau of blood injection. Injection of CX with comparable viscosity as blood reproduced the ICP course of the blood injection group. Compared with the CBF course after blood injection, CX induced a comparable early global ischemia within the first minutes which was followed by a prompt return to baseline level with no further hypoperfusion despite an equal ICP course. The inflammatory response within the tissue did not differ between blood or blood-substitute injection. The systemic inflammation was significantly more pronounced in the CX injection group compared with the other fluids including blood. By cisterna magna injection of blood substitution fluids, we established a subarachnoid space occupying rat model that exactly mimicked the course of ICP in the first 6 h following blood injection. Fluids lacking blood components did not induce the typical prolonged hypoperfusion occurring after blood-injection in this very early phase. Our study strongly suggests that blood components rather than elevated ICP play an important role for early hypoperfusion events in SAH.

Polyvinylpyrrolidone-coated catheters decrease choroid plexus adhesion and improve flow/pressure performance in an in vitro model of hydrocephalus.

Proximal catheter obstruction is the leading cause of ventricular shunt failure in pediatric patients. Our aim is to evaluate various types of shunt catheters to assess in vitro cellular adhesion and obstruction. Four catheter types were tested: (1) antibiotic and impregnated, (2) barium-stripe polyvinylpyrrolidone coated (PVP), (3) barium-stripe, and (4) barium-impregnated. Catheters were seeded with choroid plexus epithelial cells to test cellular adhesion and inoculated with the same cells to test flow/pressure performance under choroid plexus growth conditions. Ventricular catheters were placed into a three-dimensional printed phantom ventricular replicating system through which artificial cerebrospinal fluid (CSF) was pumped. Differential pressure sensors were used to measure catheter performance. PVP catheters had the lowest median cell attachment (10 cells) compared to antibiotic-impregnated (230 cells), barium stripe (513 cells), and barium-impregnated (146 cells) catheters after culture (p < 0.01). In addition, PVP catheters (- 0.247cm H2O) and antibiotic-impregnated (- 1.15cm H2O) catheters had significantly lower pressure in the phantom ventricular system compared to the barium stripe (0.167cm H2O) and barium-impregnated (0.618cm H2O; p < 0.01) catheters. PVP catheters showed less cellular adhesion and, together with antibiotic-impregnated catheters, required less differential pressure to maintain a consistent flow. Our findings suggest clinical relevance for using PVP ventricular catheters in patients with recurrent catheter obstruction by choroid plexus.

Intraoperative irrigation of artificial cerebrospinal fluid and temperature of irrigation fluid for chronic subdural hematoma: a systematic review and meta-analysis.

To systematically review the different types of irrigation fluid and the different temperatures of irrigation fluid on postoperative recurrence rates in the evacuation of chronic subdural hematoma (CSDH). We conducted a comprehensive search of electronic databases, including PubMed, Embase, the Cochrane Library, the China National Knowledge Infrastructure (CNKI), WanFang, the Chinese VIP Information (VIP), and China Biology Medicine (CBM), and reference lists of relevant studies to identify all eligible studies. Two reviewers independently screened the titles and abstracts for inclusion, and the full-text articles were assessed for eligibility based on predetermined inclusion and exclusion criteria. Data were extracted using a standardized form, and the quality of the studies was assessed using a risk of bias tool. Meta-analyses were performed using a fixed-or random-effects model, and heterogeneity was assessed using the I2 statistic. The primary endpoint was the postoperative recurrence rate. After stringent screening, a total of 11 studies were identified, including six English publications, four Chinese publications, and one Japanese publication, involving a population of 29,846 patients. Our meta-analysis provides evidence that artificial cerebrospinal fluid (ACF) could decrease the post-operative recurrence rate by 47% after the evacuation of CSDH when compared to normal saline (NS) [(odds ratio) OR 0.53, 95% confidence intervals (CI): 0.31-0.90, p = 0.02, I2 = 67%]. Besides, the irrigation fluid at body temperature could decrease the postoperative recurrence rate of CSDH by 64% when compared to room temperature (OR = 0.36, 95% CI = 0.22-0.59, p < 0.0001, I2 = 0%). Our analysis revealed significant difference in the choice of irrigation fluid for CSDH surgery. Notably, we found that irrigation with fluid at body temperature demonstrated superiority over irrigation with fluid at room temperature, resulting in fewer instances of recurrence. This straightforward technique is both safe and widely available, providing an opportunity to optimize outcomes for patients with CSDH. Our findings suggest that the use of body-temperature NS or ACF of room temperature during operation should be considered a standard of procedure in CSDH surgery. Nevertheless, whether the different temperature of ACF could be considered a standard of procedure in CSDH surgery still need high-quality RCTs to further identify. https://www.crd.york.ac.uk/prospero/; Identifier CRD42023424344.

Isoquercitrin Played a Neuroprotective Role in Rats After Cerebral Ischemia/Reperfusion Through Up-Regulating Neuroglobin and Anti-Oxidative Stress

This study aims to investigate whether isoquercitrin (Iso) exerts a neuroprotective role effect after cerebral ischemia-reperfusion (CIR) via up-regulating neuroglobin (Ngb) or reducing oxidative stress. The middle cerebral artery occlusion/reperfusion (MCAO/R) model was constructed using Sprague Dawley rats. First, we divided 40 mice into 5 groups (n=8): sham, MCAO/R, Low-dosed Iso (5 mg/kg Iso), Mid-dosed Iso (10 mg/kg Iso), and High-dosed Iso (20 mg/kg Iso). Then, 48 rats were separated into 6 groups (n=8): sham, MCAO/R, Iso, artificial cerebrospinal fluid, Ngb antisense oligodeoxynucleotides (AS-ODNs), and AS-ODNs ± Iso. The effects of Iso on brain tissue injury and oxidative stress were evaluated using hematoxylin-eosin staining, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay, immunofluorescence, western blotting, and real-time quantitative polymerase chain reaction, enzyme-linked immunosorbent assay, and reactive oxygen species (ROS) detection. The neurologic score, infarct volume, histopathology, apoptosis rate, and ROS production were reduced in Iso dose-dependent. The Ngb expression enhanced in Iso dose-dependent. The oxidative stress-related factors SOD, GSH, CAT, Nrf2, HO-1, and HIF-1α levels also increased in Iso dose-dependent, whereas the MDA levels decreased. However, related regulation of Iso on brain tissue damage and oxidative stress were reversed after low expression of Ngb. Isoquercitrin played a neuroprotective role after CIR through up-regulating of Ngb and anti-oxidative stress.

Effect of high-frequency stimulation on the complexity of low-Mg2+-induced epileptiform discharge rhythm waves in the CA3 region of rat hippocampal slices

High-frequency stimulation (HFS) is a crucial therapeutic approach for neurodegenerative conditions, such as epilepsy. However, its underlying mechanism of inhibition remains unclear. In this study, a rat model of epileptiform discharges (EDs) was constructed by perfusing brain slices with magnesium-free artificial cerebrospinal fluid (aCSF), where after HFS was used to stimulate the CA3 area of the hippocampus. The EDs signals of each sub-region of hippocampal slices before and after HFS were recorded based on a multi-electrode Array (MEA). Secondly, the changes of approximate entropy (ApEn) complexity of rhythms in different regions of hippocampal slices before and after HFS were deeply analyzed The results showed that different rhythm characteristics of EDs signals exhibited significant differences before and after HFS. Here HFS significantly inhibited the delta rhythm of field potential and enhanced the beta rhythm. Finally, the changing rhythm of the EDs signal in the propagation path before and after HFS was analyzed, and it was found that the inhibitory target of HFS on EDs signal was in the CA3b sub-region. The rhythm would gradually decline with the propagation of EDs signal in the hippocampal neural pathway. This study shows that HFS can modulate the local field potential, thus inhibiting the pathological rhythm caused by epilepsy, which provides a novel research incentive for HFS to inhibit EDs.

Toward Highly Matching the Dura Mater: A Polyurethane Integrating Biocompatible, Leak-Proof, and Self-Healing Properties.

The dura mater is the final barrier against cerebrospinal fluid leakage and plays a crucial role in protecting and supporting the brain and spinal cord. Head trauma, tumor resection and other traumas damage it, requiring artificial dura mater for repair. However, surgical tears are often unavoidable. To address these issues, the ideal artificial dura mater should have biocompatibility, anti-leakage, and self-healing properties. Herein, this work has used biocompatible polycaprolactone diol as the soft segment and introduced dynamic disulfide bonds into the hard segment, achieving a multifunctional polyurethane (LSPU-2), which integrated the above mentioned properties required in surgery.In particular, LSPU-2 matches the mechanical properties of the dura mater and the biocompatibility tests with neuronal cells demonstrate extremely low cytotoxicity and do not cause any negative skin lesions. In addition, the anti-leakage properties of the LSPU-2 are confirmed by the water permeability tester and the 900mm H2 O static pressure test with artificial cerebrospinal fluid. Due to the disulfide bond exchange and molecular chain mobility, LSPU-2 could be completely self-healed within 115min at human body temperature. Thus, LSPU-2 comprises one of the most promising potential artificial dura materials, which is essential for the advancement of artificial dura mater and brain surgery.

Ultralight 3D Graphene Oxide Aerogel Decorated with Pd-Fe Nanoparticles for the Simultaneous Detection of Eight Biomolecules.

In this proof-of-concept study, an ultralight graphene oxide aerogel (GOx-Aero) decorated with bimetallic palladium-iron nanoparticles (Pd-Fe) was synthesized and immobilized on a glassy carbon electrode (GCE) for electrochemical sensor applications. The main objective of this work was to develop a sensitive electrochemical sensor capable of simultaneously detecting eight biomolecules, including ascorbic acid (AA), dopamine (DA), uric acid (UA), 8-hydroxyguanine (8HG), guanine (G), adenine (A), thymine (T), and cytosine (C). To the best of our knowledge, this is the first time that an electrochemical sensor has been able to detect eight biomolecules simultaneously. The bimetallic GOx aerogel significantly enhanced the performance of the sensor by increasing the electroactive area, conductivity, and anodic peak current response. The sensor demonstrated sharp, well-defined, and continuous oxidation peaks for all eight analytes of interest and wide linear ranges of 5.0-1750, 0.25-100.0, 0.5-500.0, 0.5-375.0, 0.5-500.0, 0.5-500.0, 5.0-1500.0, and 5.0-1500.0 μM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The prepared sensor also exhibited excellent stability, reproducibility, and sensitivity with a very low limit of detection (LOD) of 553.7, 1.8, 69.6, 43.2, 42.9, 72.3, 57.2, and 318.4 nM for AA, DA, UA, 8HG, G, A, T, and C, respectively. The Pd-Fe-GOx-Aero-GCE was also tested in various real samples such as artificial saliva, artificial cerebrospinal fluid (CSF), salmon sperm DNA, and genomic DNA from calf thymus, where it demonstrated good recovery values. Additionally, the novel developed sensor was used to monitor the interaction between the anticancer drug, cisplatin, which has well-described binding affinity with the G and A bases in DNA. Overall, Pd-Fe-GOx-Aero-GCE displayed an extremely promising platform not only for the simultaneous detection of eight biomolecules in complex biological matrices but also for DNA-drug interaction studies toward the development of electrochemical high-throughput drug screening assays, which is of great importance in the field.

Interference of different anesthetic agents on behavior and oxidative stress in the animal model of Aβ1‐42‐induced dementia in mice.

AbstractBackgroundAlzheimer’s disease (AD) is a progressive neurodegenerative disease. The animal model of AD‐like dementia induced by the peptide β‐amyloid 1‐42 (Aβ1‐42) is widely used. However, the animals have to be anesthetized and no studies are evaluating which anesthetic causes less interference in this model. This study aimed to evaluate the interference of different anesthetics on behavioral and oxidative stress in a mice model of Aβ1‐42‐induced dementia.MethodMale and female BALB/c mice at 3‐ month‐old were used under three different protocols. Protocol 1 (inhalation): (1) 100% oxygen (isoflurane control); (2) artificial cerebrospinal fluid (ACSF) + isoflurane; (3) Aβ1‐42 + isoflurane. Protocol 2 (intraperitoneal): (1) saline; (2) ACSF + ketamine + xylazine; (3) ACSF + ketamine + dexmedetomidine; (4) Aβ1‐42 + ketamine + xylazine; (5) Aβ1‐42 + ketamine + dexmedetomidine. Protocol 3 (intraperitoneal): (1) saline; (2) ACSF + propofol; (3) Aβ1‐42 + propofol. After the anesthesia, mice were injected with Aβ1‐42 (400 pmol) free‐hand intracerebroventricular, then after 13 days, mice were submitted to the Y‐maze test (spatial memory), plus‐maze (anxiety), and open‐field (habituation memory); then, hippocampus were dissected to analysis.ResultIsoflurane per se (protocol 1) caused no memory impairment, but caused an anxiolytic effect in males, in addition, to increased sulfhydryl content in males. In protocol 2, ACSF + ketamine + xylazine induced spatial memory impairment in males and habituation memory impairment in females; the anesthetics of protocol 2 increased 2',7' dichlorodihydrofluorescein (DCF) levels in females, and ACSF + ket + dex reduced levels of glutathione (GSH) in males. In protocol 3, propofol per se caused an anxiolytic effect in males and increased DCF levels in males and females, increased superoxide dismutase activity in males, and reduction in females, in addition, increased sulfhydryl content in males.ConclusionAll anesthetic protocols evaluated caused alterations in the behavior and/or oxidative stress parameters; however, isoflurane seems to cause less interference in the animal model, followed by propofol. Protocol 3 seems to cause more interference, including in the Y‐maze (spatial memory), which is one of the main behavior tests to evaluate the mice model of Aβ1‐42‐induced dementia.

Multiplex in‐vivo quantification of tau by mass spectrometry: Method optimization for comprehensive detection of tau proteoforms and biomarker identification

AbstractBackgroundNeurodegenerative diseases diagnosis is still challenging, especially at the early stages. The diagnosis of Alzheimer’s disease (AD) relies on the identification of tau proteoforms (i.e., phosphorylation) in the cerebrospinal fluid (CSF) and plasma. However, pathophysiological fluid biomarkers are still lacking for non‐AD tauopathies. Multiplex liquid chromatography (LC)‐mass spectrometry (MS/MS) offers the opportunity to quantify the vast diversity of tau proteoforms (3R and 4R isoforms, truncations, phosphorylations, acetylations). The current gold standard for tau extraction before LC‐MS/MS analysis of very low concentrations in biofluids relies on immunoprecipitation (IP) approaches. Nonetheless, IP may miss some proteoforms due to its high selectivity. Here, we tested anti‐body free and IP approaches and compared their ability to detect tau proteoforms with LC‐MS/MS.MethodWe analyzed samples of artificial CSF (recombinant tau protein in diluted serum), and human CSF (from AD and non‐AD patients). Fully 15N‐labeled tau was added as an internal standard to the samples. Regarding IP, we first assessed a panel of commercial tau antibodies (in line with the literature) coated on magnetic beads. For the antibody‐free approach, we performed perchloric acid precipitation, followed by micro‐Solid Phase Extraction (Pc‐µSPE) using Oasis hydrophilic‐lipophilic balance sorbent. Purified proteins were digested into peptides using trypsin before multiplex quantitative analysis on reversed‐phase capillary LC, coupled with a qExactive high‐resolution mass spectrometer operated in the Parallel Reaction Monitoring (PRM) acquisition mode.ResultIP optimization led to a combination of antibodies targeting the central and N‐ter domains of tau. IP and Pc‐µSPE comparison in artificial CSF showed a higher sensitivity of IP: limits of detection decreased up to a factor 5. In the human CSF, Pc‐µSPE allowed for better detection of peptides from the N‐ter to the C‐ter than IP, and a higher signal for tau proteoforms (e.g., 3R and 4R isoforms and phosphorylated tau species).ConclusionDespite better performances when dealing with canonical tau, IP was overcome by the antibody‐free sample preparation when identifying tau proteoforms with LC‐MS/MS in human CSF. The protocol is readily applicable to samples of clinical cohorts. This result opens the possibility of better detecting tau proteoforms and identifying pathophysiological biomarkers for non‐AD tauopathies.

Bioresorbable Insertion Aids for Brain Implantable Flexible Probes: A Comparative Study on Silk Fibroin, Alginate, and Disaccharides

Miniaturized, flexible, and biocompatible neural probes have the potential to circumvent the brain's foreign body response, but the problem of surgical implantation remains. Herein, a probe intended for implantation in the rat hippocampus is coated in four bioresorbable stiffeners to determine which is most effective in aiding insertion. The stiffeners (sucrose, maltose, silk fibroin, and alginate) are evaluated through mechanical, chemical, and dissolution tests. After coating with silk fibroin, the buckling force of the neural probe increases from 0.31 to 75.99 mN. This goes in accordance with subsequent successful insertion tests. Fourier transform infrared spectroscopy results demonstrate the increase in β‐sheet content of silk fibroin samples after treatment (e.g., water annealing) and show relevant changes due to dehydration of the alginate hydrogel. Both qualitative and quantitative dissolution studies in artificial cerebrospinal fluid illustrate that alginate and silk fibroin outlasts the disaccharide stiffeners. In this work, a variety of multidisciplinary analyses are carried out to find the best bioresorbable stiffener for deep brain implantable devices with the highest buckling force, longest dissolution time, and the most tunable structure. For the first time, an alginate hydrogel is used as a stiffener to aid insertion, expanding its usefulness beyond neural tissue engineering.

FAST (Flexible Acetylcholine Sensing Thread): Real-Time Detection of Acetylcholine with a Flexible Solid-Contact Potentiometric Sensor.

Acetylcholine (ACh) is involved in memory and learning and has implications in neurodegenerative diseases; it is therefore important to study the dynamics of ACh in the brain. This work creates a flexible solid-contact potentiometric sensor for in vitro and in vivo recording of ACh in the brain and tissue homogenate. We fabricate this sensor using a 250 μm diameter cotton yarn coated with a flexible conductive ink and an ACh sensing membrane that contains a calix[4]arene ionophore. The exposed ion-to-electron transducer was sealed with a 2.5 μm thick Parylene C coating to maintain the flexibility of the sensor. The resulting diameter of the flexible ACh sensing thread (FAST) was 400 μm. The FAST showed a linear response range from 1.0 μM to 10.0 mM in deionized water, with a near-Nernstian slope of 56.11 mV/decade and a limit of detection of 2.6 μM. In artificial cerebrospinal fluid, the limit of detection increased to 20 μM due to the background signal of ionic content of the cerebrospinal fluid. The FAST showed a signal stability of 226 μV/h over 24 h. We show that FAST can measure ACh dynamics in sheep brain tissue and sheep brain homogenate after ACh spiking. FAST is the first flexible electrochemical sensor for monitoring ACh dynamics in the brain.

Development of a shortwave infrared sinuscope for the detection of cerebrospinal fluid leaks.

Cerebrospinal fluid (CSF) rhinorrhea (leakage of brain fluid from the nose) can be difficult to identify and currently requires invasive procedures, such as intrathecal fluorescein, which requires a lumbar drain placement. Fluorescein is also known to have rare but significant side effects including seizures and death. As the number of endonasal skull base cases increases, the number of CSF leaks has also increased for which an alternative diagnostic method would be highly advantageous to patients. We aim to develop an instrument to identify CSF leaks based on water absorption in the shortwave infrared (SWIR) without the need of intrathecal contrast agents. This device needed to be adapted to the anatomy of the human nasal cavity while maintaining low weight and ergonomic characteristics of current surgical instruments. Absorption spectra of CSF and artificial CSF were obtained to characterize the absorption peaks that could be targeted with SWIR light. Different illumination systems were tested and refined prior to adapting them into a portable endoscope for testing in 3D-printed models and cadavers for feasibility. We identified CSF to have an identical absorption profile as water. In our testing, a narrowband laser source at 1480nm proved superior to using a broad 1450nm LED. Using a SWIR enabling endoscope set up, we tested the ability to detect artificial CSF in a cadaver model. An endoscopic system based on SWIR narrowband imaging can provide an alternative in the future to invasive methods of CSF leak detection.

Folic acid does not have an anti-manic effect but protect the brain against oxidative stress in an animal model of mania induced by ouabain

BackgroundBipolar disorder (BD) is a complex and severe mental disorder that affects 1–3 % of the world population. Studies have suggested the involvement of oxidative stress in the physiopathology of this psychiatry disorder. Folic acid (FA), a vitamin from the B complex, is a nutraceutical that has recently been researched as a possible treatment for BD since folate is reduced in patients with the disorder. The present study aimed to evaluate the effects of lithium (Li) and FA on behavioral changes and oxidative stress parameters in an animal model of mania induced by ouabain (OUA). MethodsWistar rats received a single intracerebroventricular (ICV) injection of OUA or artificial cerebrospinal fluid (aCSF). From the day following ICV injection, the rats were treated for seven days with gavage injections of Li (47.5 mg/kg/mL), FA (50 mg/kg/mL), or water (1 mL/kg). On the 7th day after OUA injection, locomotor activity was measured using the open-field test. In addition, the oxidative stress parameters were evaluated in rats' frontal cortex, striatum, and hippocampus. ResultsOUA induced mania-like behavior and oxidative stress in rats' brains, but Li could reverse these alterations. FA did not affect behavior parameters; however, it presents an antioxidant effect on the brain structures evaluated. LimitationsThe study was only evaluated male rats and ICV injection is an invasive procedure. ConclusionThese results indicate that even though FA has an effect against the oxidative stress induced by OUA, this effect was not strong enough to interfere with behavior parameters.

A label-free dually-amplified aptamer sensor for the specific detection of amyloid-beta peptide oligomers in cerebrospinal fluids

Amyloid-beta peptide oligomer (Aβo) is widely acknowledged to be associated with Alzheimer's disease (AD). The immediate and accurate detection of Aβo may provide the index for tracking the progress of the state of the disease, as well as some useful information for investigating the pathology of AD. In this work, based on a triple helix DNA which triggers a series of circular amplified reactions in the presence of Aβo, we designed a simple and label-free colorimetric biosensor with dually-amplified signal for the specific detection of Aβo. The sensor displays some advantages including high specificity, high sensitivity, low detection limit down to 0.23 pM, and wide detection range with three orders of magnitude from 0.3472 to 694.44 pM. Furthermore, the proposed sensor was successfully applied for detecting Aβo in artificial and real cerebrospinal fluids with satisfactory results, suggesting the potential application of the proposed sensor for state-monitoring and pathological studies of AD.

Encapsulation of rat brain slices in agar gel solution for long-term and reversible cryopreservation

Earlier there was found activity of glutamatergic ionotropic α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPAR) and N-methyl-D-aspartate receptors (NMDAR) disturbed after prolonged cryopreservation of brain slices at temperature of -10 оС. To eliminate cryodamage of AMPAR and NMDAR, the slices were encapsulated in the special freezing solution (SFS). SFS consisted of agar at various concentrations (33, 44 and 50 %) and artificial cerebrospinal fluid (67, 56 and 50 %, respectively). This solution was used for long-term cryopreservation of slices (52 days, -10 оС). Alterations in amplitudes of AMPA and NMDA potentials in the slices after rewarming were studied. Recovery of AMPAR and NMDAR after cryopreservation of the slices in SFS was the most optimal when the agar concentration in SFS was 50 %. Cryopreservation of the slices in SFS with different agar concentrations predominantly promoted the development of long-term potentiation in 78 % of the tested slices. Thus, the encapsulation of brain slices in SFS contributes to the preservation of AMPAR and NMDAR activity during long-term and reversible cryopreservation.

Long-lasting restoration of memory function and hippocampal synaptic plasticity by focused ultrasound in Alzheimer's disease

BackgroundFocused ultrasound (FUS) is a medical technology that non-invasively stimulates the brain and has been applied in thermal ablation, blood–brain barrier (BBB) opening, and neuromodulation. In recent years, numerous experiences and indications for the use of FUS in clinical and preclinical studies have rapidly expanded. Focused ultrasound-mediated BBB opening induces cognitive enhancement and neurogenesis; however, the underlying mechanisms have not been elucidated. MethodsHere, we investigate the effects of FUS-mediated BBB opening on hippocampal long-term potentiation (LTP) and cognitive function in a 5xFAD mouse model of Alzheimer's disease (AD). We applied FUS with microbubble to the hippocampus and LTP was measured 6 weeks after BBB opening using FUS. Field recordings were made with a concentric bipolar electrode positioned in the CA1 region using an extracellular glass pipette filled with artificial cerebrospinal fluid. Morris water maze and Y-maze was performed to test cognitive function. ResultsOur results demonstrated that FUS-mediated BBB opening has a significant impact on increasing LTP at Schaffer collateral - CA1 synapses and rescues cognitive dysfunction and working memory. These effects persisted for up to 7 weeks post-treatment. Also, FUS-mediated BBB opening in the hippocampus increased PKA phosphorylation. ConclusionTherefore, it could be a promising treatment for neurodegenerative diseases as it remarkably increases LTP, thereby improving working memory.