Development of an electrochemical sensor using carbon nanotubes and hydrophobic natural deep eutectic solvents for the detection of α-glucosidase activity in extracts of autochthonous medicinal plants

The present work describes for the first time the use of a hydrophobic natural deep eutectic solvent (H-NADES) as a dispersant for carboxylated nanotubes for the design and construction of an electrochemical sensor for the assay of α-glucosidase and its inhibitors. In this work, we used as the electrochemical probe the product of the enzymatic reaction, which consists of two redox groups and generates the analytical signal. The combination of de carboxylic multi-walled carbon nanotubes (MWCNTc) and the H-NADES of thymol and lactic acid (TLa) increases the electroactive surface area and promotes electron transfer of the electrode modified with carbon nanotubes. The electrochemical sensor enabled the detection of α-glucosidase in a range of 0.004-0.1 U mL-1 with a detection limit of 0.0013 U mL-1, which is lower than most existing methods. In addition, two α-glucosidase inhibitors, acarbose and quercetin, and two plant extracts, Schinus molle and Eugenia uniflora, were evaluated to assess the feasibility of screening potential antidiabetic drugs, and the IC50 values were 5.37 μg mL-1 and 5.28 μg mL-1. Thus, this sensing strategy represents the beginning of the incorporation of NADES in the development and design of novel sensors and their application in electrochemistry and medical analysis.

Highly sensitive and selective electrochemical sensor for simultaneous determination of gallic acid, theophylline and caffeine using poly(l-proline) decorated carbon nanotubes in biological and food samples

In this work, a novel, simple and reproducible poly(l-proline)/functionalized multi-walled carbon nanotube composite on glassy carbon electrode (poly(PRO)-MWCNTs/GCE) was developed as an electrochemical sensor for the simultaneous determination of gallic acid (GA), theophylline (TP) and caffeine (CAF) by differential pulse voltammetry (DPV). The sensing platform was optimized by experimental design and response surface methodology, using various factors affecting polymerization and detection, such as electropolymerization time and potential, and pH, respectively. As a result, the dispersion conditions were the mixing of 1.78 mg MWCNTs with 1.00 mL l-proline solution to 4.14 mg mL-1 (in SDBS 0.5%), followed by 21 min of sonication with electropolymerization by 16 cyclic scans. In addition, the final analysis was performed at a pH of 3.00 and prior accumulation at 0.350 V for 40 s. The electrochemical behavior of GA, TP and CAF on the optimized sensor was investigated. As a result, the electrode preserves and synergistically combines the properties of each modifier. This new electrochemical sensor showed superior electrocatalytic properties for the oxidation of GA, TP and CAF, which significantly improved the sensitivity of the three compounds. Under the optimized experimental conditions, the detection limits achieved by S/N were 0.03, 0.04 and 0.11 μmol L-1 for GA, TP and CAF, respectively. The analysis of real samples was successfully performed in human breast milk, tea, infusion of yerba mate, coffee, Coca-Cola zero and energy drink, showing good recoveries, ranged between 87 and 108%. The proposed sensor also showed good selectivity, repeatability and reproducibility, indicating feasibility and reliability. This is the first time that the l-proline monomer is used as a dispersant for MWCNTs and as a precursor for the in-situ polymerization of the proline polymer. Previously, the electropolymerizations were carried out with the monomer in solution rather than as an exfoliant of MWCNTs, where the polymer is electrosynthesized between MWCNTs rather than on them. In this way, the large specific surface area and strong adsorption ability of the nanomaterial are enhanced, and the ability to promote electron transfer reaction is increased, which provides enough effective reaction sites.

In situ or Ex situ Synthesis for Electrochemical Detection of Hydrogen Peroxide-An Evaluation of Co2SnO4/RGO Nanohybrids

Nowadays, there is no doubt about the high electrocatalytic efficiency that is obtained when using hybrid materials between carbonaceous nanomaterials and transition metal oxides. However, the method to prepare them may involve differences in the observed analytical responses, making it necessary to evaluate them for each new material. The goal of this work was to obtain for the first time Co₂SnO₄ (CSO)/RGO nanohybrids via in situ and ex situ methods and to evaluate their performance in the amperometric detection of hydrogen peroxide. The electroanalytical response was evaluated in NaOH pH 12 solution using detection potentials of -0.400 V or 0.300 V for the reduction or oxidation of H₂O₂. The results show that for CSO there were no differences between the nanohybrids either by oxidation or by reduction, unlike what we previously observed with cobalt titanate hybrids, in which the in situ nanohybrid clearly had the best performance. On the other hand, no influence in the study of interferents and more stable signals were obtained when the reduction mode was used. In conclusion, for detecting hydrogen peroxide, any of the nanohybrids studied, i.e., in situ or ex situ, are suitable to be used, and more efficiency is obtained using the reduction mode.

Mesoscopic behaviour of multi-layered graphene: the meaning of supercapacitance revisited

The double layer capacitive phenomena is just a particular case of a more general quantum mechanical approach, wherein the electrochemical capacitance is central hence governing the super-capacitance phenomenology in general.

Electrochemical sensing of guanine, adenine and 8-hydroxy-2′-deoxyguanosine at glassy carbon modified with single-walled carbon nanotubes covalently functionalized with lysine

Synthesis and characterization of l-lysine covalently functionalized SWCNT and analytical application for the highly sensitive quantification of guanine, adenine and 8-hydroxy-2′-deoxyguanosine.

Single forebrain ventricle without prosencephaly: agenesis of the corpus callosum with dehiscent fornices

Coalescence of the cerebral ventricles with formation of a single forebrain ventricle is described in an unusual case of agenesis of the corpus callosum with dehiscent fornices and severe hydrocephalus. The cerebral hemispheres were fully cleaved. The detached fornices were widely separated from the thalami. The membrana tectoria was retroverted over the midbrain and cerebellum, where it joined the fornices and merged with a curved membranous ependymal dome which, at a great distance, circumvented the thalami as it extended toward the anterior commissure. Other anomalies included arhinencephaly, multiple subependymal heterotopias, and Dandy-Walker malformation. Similar malformations have been described as interhemispheric cysts, as (holo)prosencephaly, or as "midline telencephalic dysgenesis." The basic features of prosencephaly and agenesis of the corpus callosum are reviewed and compared to the present case.

Cocaine-induced intratumoral hemorrhage: case report and review of the literature

A unique case is described of a 28-year-old man who had seizures and a hemorrhage within a previously unsuspected cerebellopontine angle schwannoma within minutes of nasally inhaling cocaine. A review of the literature on cocaine-induced seizures and cocaine-induced cerebral hemorrhage is also given.

Angiographically occult vascular malformations in childhood

Five infants and children with angiographically occult vascular malformations of the brain detected by computed tomography (CT) are presented. Four malformations were located in the cerebral hemisphere, and one was in the brain stem. CT demonstrated high density lesions with little or no enhancement after infusion of the contrast material. The malformations were resected and histologically proven. All patients have done well. The pertinent literature is reviewed. These lesions are uncommon during infancy and childhood and mimic gliomas clinically and radiographically. The need for surgical extirpation of these lesions is stressed.

Suprasellar cysts: surgical treatment and results

The purpose of this paper is to present the clinical picture, diagnostic studies, and treatment of 5 cases of suprasellar cyst. The clinical symptoms and signs result from increased intracranial pressure without lateralizing signs (midline syndrome) and direct compression of the adjacent structures (hypothalmopituitary syndrome). The findings of computerized transmission tomography (CTT) and cerebral angiography in patients with suprasellar cyst are very similar to those of severe hydrocephalus. Cerebral angiography, however, reveals in inordinate mass effect in the parasellar area. Even though the location of the parasellar cyst is well demonstrated on postventriculoperitoneal shunt CTT scans, pneumonencephalography is necessary to confirm the diagnosis. We treated our patients with uni- or bilateral ventriculoperitoneal shunts, followed by craniotomy and cystosubarachnoid marsupialization. Cystoperitoneal shunting was performed after craniotomy in some instances, in place of it in others.

Percutaneous epidural neurostimulation in modulation of paraplegic spasticity. Six case reports

Six cases of paraplegic, post-traumatic spasticity, alleviated by percutaneous epidural neurostimulation with temporary or permanent implanted neuroelectrodes from the L1 to L4 intervertebral levels are presented. Modulation of this spasticity and secondary beneficial physiological effects were achieved, including regulation of bowel regimens, production of sweating and piloerection below the level of the lesion, and morning erections. The main advantages of percutaneous epidural neurostimulation in modulating spasticity are the avoidance of destructive neurosurgical procedures, the regulation of secondary physiological and autonomic responses, the avoidance of antispasticity medications, and the reversibility of the neurostimulation procedure.

Physiopathology and a new treatment of chronic subdural hematoma in children

Chronic collections of fluid in the subdural spaces may result from trauma or may complicate meningitis. The etiological factor, or factors, which contribute to chronicity of subdural fluid in children remains obscure. We postulate that one possible mechanism is the progressive stretching and narrowing of the cortical veins, bridging the subarachnoid and subdural spaces to enter the superior sagittal sinus. This process ultimately leads to thrombosis of these 'hanging veins'. Narrowing and angulation of these veins could result in elevated back pressure favoring the formation of a transudate. 16 children who had progressive and persistent collections of xanthochromic fluid in the subdural spaces secondary to trauma or infection who were treated previously either with subdural tap, burr holes, subdural peritoneal shunt, craniotomy, stripping of membranes and/or a combination of these, were treated by lowering and advancing the superior sagittal sinus with its overlying sagittal suture and performing a duraplasty. This new surgical technique is directed to improve venous drainage from the superior anastomotic vein into the superior sagittal sinus. Angiographic follow-up showed that only 2 patients still have evidence of fluid collection: the rest of the patients showed normal arterial phases, the medullary system was minimally filled and all of these showed remarkable improvement of the venous drainage throughout the superficial cortical veins with no evidence of hanging veins. Intellectual development of these children following lowering of the superior sagittal sinus showed that 8 patients (50%) were normal or above normal; 5 patients (31.2%) were retarded and 3 patients (18.7%) were borderline.

Radiation myelopathy in children

Three children, 1 with medulloblastoma, 1 with anaplastic cerebellar tumor, and 1 with acute lymphocytic leukemia, received craniospinal irradiation with an estimated cord dose between 1,100 and 1,200 rets. All 3 patients after a latent period of seven to eight months developed subacute transverse myelopathy. The myelopathy was cervical in 2 patients and thoracic in 1. Spinal fluid examination showed high protein levels in 2 patients. Myelography demonstrated a swollen cord in 2 patients and normal appearance in 1. Autopsy in 1 patient disclosed a necrotizing myelopathy. The findings suggest that children tolerate less well than adults what previously have been considered safe doses of radiation to the spinal cord.

A new surgical approach to the treatment of coronal synostosis

The authors described a surgical technique for the treatment of unilateral coronal synstosis, which they have carried out successfully in 16 children. Frontal craniotomy, removal of the lesser wing of the sphenoid, orbital unroofing, and removal of the entire orbital rim are recommended as essential elements of carnio-orbital reconstruction in the treatment of plagiocephaly.

Congenital anomaly of the odontoid in children. A report of four cases

The embryologic origins of congenital abnormalities of the odontoid process are reviewed. Four cases of odontoid dysgenesis in childhood are presented. All of our cases were associated with a head injury, which subsequently led to the diagnosis. Pain was the most common presenting complaint in our patients. Decreased cervical mobility was the most consistent physcial finding. There was no major neurological defect implicating spinal cord compression in any of our patients. This is not true of adults with congenital abnormalities of the odontoid, particularly those with atlantoaxial instability. The diagnosis of odontoid dysgenesis is a radiographic one. Flexion-extension films, tomograms and cineradiograms are often required to make the diagnosis. C1-C2 subluxation, either anterior or posterior is often found. Prompt posterior cervical fusion is recommended as the treatment of choice.

Angiographic characteristics of certain subdural collections of fluid

The presence of abnormal amounts of fluid in the subdural space has been referred to as subdural hematoma, subdural effusion and subdural hygroma. These are supposed to be differentiated by the appearance of the fluid and the presence of membranes in the dubdural space. Although both hygroma and chronic subdural hematoma are liquid, space-occupying lesions which cause pressure in the underlying brain, we have found that there are definite angiographic, clinical and prognostic differences between them. These differences are described.

Laminotomy and total reconstruction of the posterior spinal arch for spinal canal surgery in childhood

Kyphosis, anterior subluxation, and instability of the spine are reported as postoperative complications of multiple level laminectomies in children. The surgical procedure of multiple level laminotomies is proposed as an alternative. Indications in infants and children, the surgical technique, and the postoperative management are presented. The goal is preservation of the normal architecture of the spine in patients who are still developing.

Peritoneal cysts: a complication of ventriculoperitoneal shunts

Large abdominal cysts are not a common complication of peritoneal shunts. In our experience only 11 of 1,585 peritoneal shunts developed this complication (0.7 percent). We believe that infection, particularly by S. epidermidis and multiple-shunt revisions, is related to the development of the cysts. Simple parencentesis and replacement of the shunt usually are sufficient treatment for this complication if infection is not present.

Cystic cavum veli interpositi associated with normal or low pressure hydrocephalus

A new clinical syndrome, characterized by progressive increase in head size (without intracranial hypertension), variable delay in milestones, moderate ventricular dilation, and the presence of a cavum veli interpositi is herein described. The arteriographic and venographic signs are suggestive, but not diagnostic, of the presence of a cavum veli interpositi. Pneumoencephalography, with adequate filling of the subarachnoid spaces and ventricles, is essential to confirming the diagnosis. Cerebrospinal fluid shunting appears to result in an improvement, but the results cannot as yet be considered definitive since only 10 of our 29 patients were shunted.

Acute subdural hematoma in infancy and childhood

27 cases of acute posttraumatic subdural hematomas diagnosed and treated by the authors from 1968 to 1972 are presented. Five were newborns, 18 were infants, and three were toddlers. The youngest patient was 38 h and the oldest 5 years old. The most common age was between 1 and 3 months. Falls were the most frequent cause of injury, parental or familial abuse was next. A correlative analysis of the different clinical pictures in each of these age groups is made. We stressed that the presence of hemorrhages in the fundi, and convulsions, in the infant who has suffered a head injury, are indications for contrast studies. A critical analysis of subdural taps, as a method of diagnosis and treatment, is made: we seriously doubt that subdural taps are of any real value in the clinical management of a child with acute head injury. Comparative analysis of the surgical treatment and results is made. Twelve patients were treated with repeated subdural taps, 15 with craniotomy. Of the former group, 41.6% developed a chronic subdural whereas only 13% of the latter group developed this complication. Five out of the 27 patients died. Comparative psychological evaluation of these two groups, surgical and nonsurgical, is presented. In the surgical group 72.7% had an IQ over 80 and in the nonsurgical group only 25% had an IQ over 80. A correlative analysis of the clinical picture, method of diagnosis, surgical result, and psychological tests are analyzed.

Diagnosis and surgical treatment of choroid plexus papillomas

This is a report of 22 cases of papillomas of the choroid plexus diagnosed and managed personally by the author. The angiographic diagnosis and extension of choroid plexus papillomas are described, as is the surgical technique for removing these tumors from the lateral, third, and fourth ventricles. Specific attention is given to using the angiogram as the study of choice upon which surgical technique is planned. The diagnosis of choroid plexus papilloma of the lateral ventricle is made by observing the presence of a hypertrophied anterior choroidal artery, a 'double tumor' sign with one tumor at the trigone and the other within the temporal or frontal horn, tumor stain at the trigone, and asymmetrical hydrocephalus, generally, with a shift away from the side of the larger ventricle. Posterior fossa papillomas cause symmetrical hydrocephalus and generally have tumor stain located within the midline, with the major feeding coming from either the superior cerebellar or the posteroinferior cerebellar arteries. Surgical removal of the tumor should entail an 'en bloc' resection following occlusion of the feeding and draining vessels. The tumor should be removed directly when it is in the lateral ventricle and following ventriculocerebral spinal fluid shunting when it is in the posterior fossa.