Textile Organic Electrochemical Transistors as a Platform for Wearable Biosensors.

The development of wearable chemical sensors is receiving a great deal of attention in view of non-invasive and continuous monitoring of physiological parameters in healthcare applications. This paper describes the development of a fully textile, wearable chemical sensor based on an organic electrochemical transistor (OECT) entirely made of conductive polymer (PEDOT:PSS). The active polymer patterns are deposited into the fabric by screen printing processes, thus allowing the device to actually "disappear" into it. We demonstrate the reliability of the proposed textile OECTs as a platform for developing chemical sensors capable to detect in real-time various redox active molecules (adrenaline, dopamine and ascorbic acid), by assessing their performance in two different experimental contexts: i) ideal operation conditions (i.e. totally dipped in an electrolyte solution); ii) real-life operation conditions (i.e. by sequentially adding few drops of electrolyte solution onto only one side of the textile sensor). The OECTs response has also been measured in artificial sweat, assessing how these sensors can be reliably used for the detection of biomarkers in body fluids. Finally, the very low operating potentials (<1 V) and absorbed power (~10-4 W) make the here described textile OECTs very appealing for portable and wearable applications.

A simple all-PEDOT:PSS electrochemical transistor for ascorbic acid sensing.

An ascorbic acid (AA) sensor was developed by employing an organic electrochemical transistor (OECT) based only on PEDOT:PSS as a conductive material. The device was prepared by spin coating using the CLEVIOS™ PH 1000 suspension (PEDOT:PSS) masking the gate and the channel areas with tape. The device was electrically characterized while the doping level of the PEDOT:PSS in the channel was controlled using both the gate electrode and the potentiostat. It was demonstrated that the current that flows in channel (Id) is controlled by the concentration of oxidized sites in the examined potential range. AA reacts with the conductive polymer leading to the extraction of charge carriers from the channel, and thus resulting in a decrease of the absolute value of Id. It was observed that Id linearly depends on the logarithm of the AA concentration between 10-6 and 10-3 M. The OECT response to AA was studied by varying the gate voltage or the PEDOT:PSS thickness. The performance of the device for optimized conditions shows a limit of detection equal to 10-8 M and a sensitivity of 4.5 ± 0.1 × 10-6 A decade-1.

Dopamine amperometric detection at a ferrocene clicked PEDOT:PSS coated electrode.

Chemically modified electrodes are widely employed in electroanalytical chemistry and an important goal is to strongly anchor redox mediators on the electrode surface. In this work, indium tin oxide (ITO) electrodes have been coated with PEDOT:PSS that has been ferrocene-functionalized, by a two-step procedure consisting of the electrodeposition of PEDOT-N3 followed by copper-catalyzed azide-alkyne cycloaddition of ethynylferrocene. The coated electrodes have been characterized by XPS, showing successful ferrocene immobilization, by AFM, and by cyclic voltammetry (CV), which is dominated by the stable and highly reversible response of ferrocene. The electrocatalytical performance of the device is assessed by analyzing 3,4-dihydroxyphenyl ethylamine, also commonly known as dopamine (DA). The sensor presents a linear range between 0.01 and 0.9 mM, a mean sensitivity of 196 mA M-1 cm-2 and a limit of detection (LoD) of 1 µM.

Alpha-galactosidase versus active charcoal for improving sonographic visualization of abdominal organs in patients with excessive intestinal gas.

UNLABELLED: Intestinal gas is a frequent cause of poor visualization during gastrointestinal ultrasound (US). The enzyme alpha-galactosidase may reduce intestinal gas production, thereby improving abdominal US visualization. We compared the efficacies of alpha-galactosidase and active charcoal in improving US visualization in patients with previous unsatisfactory abdominal US scans caused by excessive intestinal gas. MATERIALS AND METHODS: 45 patients with poor visualization of at least one target organ: pancreas, hepatic lobes (score 0-2) or common bile duct (CBD) (score 0-1) were enrolled in a prospective randomized, crossover, observer-blinded study. The patients received alpha-galactosidase (Sinaire Forte, Promefarm, Milan, Italy) 600 GalU t.i.d. for 2 days before abdominal US plus 900 GalU the morning of exam or active charcoal 448 mg t.i.d., for 2 days before the exam plus 672 mg the morning of the exam. Visualization was graded as follows: 0 = none (complete gas interference); 1 = severe interference, 2 = moderate interference, 3 = mild interference; 4 = complete (no gas interference). RESULTS: 42 patients completed the study. Both alpha-galactosidase and active charcoal improved the visualization of target organs. Visualization of the right hepatic lobe, CBD and pancreatic tail was significantly improved (vs. baseline) only by alpha-galactosidase (p < 0.01). Scores ≥3 for all parts of the pancreas and both hepatic lobes were achieved in only 12.5% of the patients after both treatments. Both products were well tolerated. CONCLUSION: Alpha-galactosidase and active charcoal can improve US visualization of abdominal organs in patients whose scans are frequently unsatisfactory due to excessive intestinal gas. Visualization of the pancreatic tail and right hepatic lobe was significantly improved only by alpha-galactosidase. However, both treatments allowed adequate visualization of all target organs during the same examination only in a few patients.

Effect of low temperature on soybean peroxidase: spectroscopic characterization of the quantum-mechanically admixed spin state.

A spectroscopic study of soybean peroxidase (SBP) has been carried out using electronic absorption, resonance Raman (RR) and electron paramagnetic resonance (EPR) spectroscopy in order to determine the effects of temperature on the heme spin state. Upon lowering the temperature a transition from high spin to low spin is induced in SBP resulting from conformational changes in the heme cavity, including a contraction of the heme core, the reorientation of the vinyl group in position 2 of the porphyrin macrocycle, and the binding of the distal His to the Fe atom. Moreover, the combined analysis of the data derived from the different techniques at both room and low temperatures demonstrates that at low temperature the quantum-mechanically admixed spin state (QS) of SBP has RR frequencies different from those observed for the QS species at room temperature.

Formation of two types of low-spin heme in horseradish peroxidase isoenzyme A2 at low temperature.

Electronic absorption, resonance Raman and EPR spectra are reported for ferric horseradish peroxidase isoenzyme A2 at neutral and alkaline pH together with its imidazole complex at 12 K. The data are compared with those obtained at room temperature. At neutral pH, lowering the temperature induces conformational changes with the formation of two types of low-spin hemes, a bis-histidyl type and a hydroxo type. The transition induced by lowering the temperature is accompanied by a change in the orientation of a vinyl substituent which appears less conjugated to the porphyrin macrocycle than at room temperature. At low temperature the low-spin hemes coexist with a quantum admixed spin species. All the forms are characterized by extremely high resonance Raman frequencies, indicating a contraction of the core size from that of the room temperature species. At alkaline pH, only one low-spin species is observed at both room and low temperatures, with a hydroxo ligand bound to the heme iron. The v(Fe-OH) stretching mode has been assigned at 512 cm(-1), on the basis of the isotopic shift observed in D2O and H2(18)O. This relatively low frequency, together with the anomalous shift observed in deuterium, indicates that the hydrogen bonds between the oxygen atom and the distal residues are stronger than in metmyoglobin, but weaker than those of horseradish peroxidase isoenzyme C. This is in agreement with the lower tetragonality, determined from the EPR g values, of alkaline horseradish peroxidase isoenzyme A2 than of metmyoglobin.

Peroxidase-benzhydroxamic acid complexes: spectroscopic evidence that a Fe-H2O distance of 2.6 A can correspond to hexa-coordinate high-spin heme.

Resonance Raman (RR) spectra have been obtained for single-crystal horseradish peroxidase isozyme C complexed with benzhydroxamic acid (BHA). The data are compared with those obtained in solution by both RR and electronic absorption spectroscopies at room and low (12-80 K) temperatures. Moreover, the analysis has been extended to Coprinus cinereus peroxidase complexed with BHA. The results obtained for the two complexes are very similar and are consistent with the presence of an aqua six-coordinate high-spin heme. Therefore it can be concluded that despite the rather long Fe-H2O distance of 2.6-2.7 A found by X-ray crystallography in both complexes, the distal water molecule can still coordinate to the heme iron.

The quantum mixed-spin heme state of barley peroxidase: A paradigm for class III peroxidases.

Electronic absorption and resonance Raman (RR) spectra of the ferric form of barley grain peroxidase (BP 1) at various pH values, at both room temperature and 20 K, are reported, together with electron paramagnetic resonance spectra at 10 K. The ferrous forms and the ferric complex with fluoride have also been studied. A quantum mechanically mixed-spin (QS) state has been identified. The QS heme species coexists with 6- and 5-cHS hemes; the relative populations of these three spin states are found to be dependent on pH and temperature. However, the QS species remains in all cases the dominant heme spin species. Barley peroxidase appears to be further characterized by a splitting of the two vinyl stretching modes, indicating that the vinyl groups are differently conjugated with the porphyrin. An analysis of the currently available spectroscopic data for proteins from all three peroxidase classes suggests that the simultaneous occurrence of the QS heme state as well as the splitting of the two vinyl stretching modes is confined to class III enzymes. The former point is discussed in terms of the possible influences of heme deformations on heme spin state. It is found that moderate saddling alone is probably not enough to cause the QS state, although some saddling may be necessary for the QS state.

Versatility of heme coordination demonstrated in a fungal peroxidase. Absorption and resonance Raman studies of Coprinus cinereus peroxidase and the Asp245-->Asn mutant at various pH values.

The pH dependence of the electronic absorption and resonance Raman (RR) spectra of FeIII and FeII forms of Coprinus cinereus peroxidase (CIP) and its Asp245-->Asn (D245N) mutant has been examined in detail. The spectral data were obtained in the pH range 3.8-12.0. These spectra were used to assess the spin and ligation states of the heme via the porphyrin marker band frequencies and the wavelengths of the absorption maxima, especially that of the band (CT1) due to the charge transfer from the porphyrin to the heme iron via the a' 2u(pi)-->eg (d pi) electronic transition. The RR spectra were obtained by using different excitation wavelengths and polarized light. The data obtained for ferric CIP show that two pH-induced structural transitions exist. At acid pH the Soret and the CT1 absorption maxima occur at 394 and 652 nm, respectively, compared with the values of 403 and 649 nm observed at neutral pH. The electronic data indicate that at acid pH the proximal Fe-Im bond might be weakened or ruptured, and the RR spectra show a new species (5-c HS) different from the normal neutral 5-coordinate high-spin (5-c HS) heme. At pH 12.0, the protein converts to a 6-coordinate low-spin (6-c LS) heme with a hydroxyl ligand coordinated in the sixth position of the heme iron and strongly hydrogen-bonded with the positively charged guanidinium group of the distal Arg51 residue. Replacement of the aspartate carboxylate group of Asp245, which acts as hydrogen-bond acceptor to the proximal His183 ligand of the heme Fe, with a carboxamide group of an asparagine residue has a profound influence on the heme coordination. The RR spectra of the Fe(II) form of this mutant at both neutral and alkaline pH values show a band at 204 cm-1 assigned to the Fe-His stretch associated with a fairly weak or non-hydrogen-bonded imidazole. The ferric form of the mutant shows a great variability in coordination and spin states upon pH titration. Between pH 8.8 and 3.8 the spectra are mainly characteristic of a 6-coordinate high-spin heme, presumably with a water molecule bound on the distal side of the Fe atom. The pKa of the alkaline transition of the mutant is much lower than that of the wild-type protein. At pH 10.0 the D245N mutant is in its final alkaline form, which markedly differs from that of the parent enzyme. The spectral data indicate that the majority of the protein has 5-coordinate high-spin heme (5-c HS), with the Fe-His 183 bond broken and the distal axial coordination site of the heme iron occupied by a hydroxyl group, which is strongly hydrogen-bonded with distal Arg51. Therefore, the Asp245-->Asn mutation on the proximal side results in the breakage of the Fe-His bond at alkaline pH.

Effect of the His175-->Glu mutation on the heme pocket architecture of cytochrome c peroxidase.

Resonance Raman (RR) and electronic absorption spectra of the ferric and ferrous forms of the His175Glu mutant of cytochrome c peroxidase are reported. At 296 K, the FeIII form is five-coordinate high spin and the resonance Reman spectra are very similar to those obtained for the wild type enzyme, even though in the mutant the Fe atom is bound to an oxygen atom of the Glu residue. The only difference is that the bands due to the out-of-plane modes are very weak, indicating a less distorted heme plane compared to CCP. The absorption spectrum is similar to that of CCP, as far as the Soret and alpha, beta bands are concerned, but the charge-transfer band due to the a2u(pi)-->eg(d pi) transition is 8 nm blue-shifted relative to that of the wild type enzyme, indicating that a more negative ligand is bound to the heme iron. As the temperature is lowered, the five-coordinate heme converts to a six-coordinate high-spin form. The conversion is readily reversible. A temperature effect on the protein structure is proposed that permits the Fe atom to approach the heme plane and to bind the distal water molecule. The results are discussed in terms of the X-ray structure, which shows a different disposition of the distal water molecules in the Glu175 mutant. The RR spectra also show that the heme is more contracted and distorted at 19 K than at room temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Spin state and axial ligand bonding in the hydroxide complexes of metmyoglobin, methemoglobin, and horseradish peroxidase at room and low temperatures.

Absorption and resonance Raman spectra using Soret excitation of alkaline metmyoglobin (metMb), methemoglobin (metHb), and horseradish peroxidase (HRP) were obtained at room and low temperature. At 298 K both metMb and metHb exhibit two isotope-sensitive bands assigned to high- and low-spin nu(Fe-OH) stretching modes, respectively, which are correlated with the spin-state population. The low-spin stretch occurs 60 cm-1 to higher energy than the corresponding high-spin vibration. When the temperature is lowered, only the low-spin species is observed. HRP exhibits at both 298 and 20 K only the low-spin nu(Fe-OH) stretching mode, which occurs 50 cm-1 to lower energy than the corresponding modes observed in the globins. This is explained in the context of a strong hydrogen bond between the hydroxyl ligand and the distal His42 and/or Arg38. Lowering temperature causes in all of the examined proteins a strengthening of the Fe-OH bond and a contraction of the core of about 0.01 A, as determined by the upshifting of the low-spin nu(Fe-OH) stretching mode and the core size marker bands. Both effects are ascribed to an increase of the packing forces.

Diaphragm pacing: clinical and experimental results.

Over the last 26 years diaphragm pacing has been used in over 400 adults and 70 children to support ventilation and oxygenation. Diaphragm pacing can be useful for conditions in which the brain stem respiratory centers provide little or no stimulation to the respiratory muscles, i.e. central hypoventilation syndrome, Arnold-Chiari malformation/brain stem dysfunction, and high quadriplegia. Because the pacing systems are so portable, the greatest advantages accrue to those patients who require ventilatory support both while awake and asleep. Infants and children require tracheostomy to avoid upper airway obstruction and bilateral pacing to meet higher metabolic demands. The stimulus parameters most appropriate for pediatric patients have been characterized as low stimulus frequency, short inspiratory time, and moderate respiratory rate. Use of similar stimulus parameters in an immature animal model has resulted in preservation of diaphragmatic structure and function but transformation of the diaphragm from a mixed muscle to one with a uniform population of type 1, fatigue-resistant fibers (physiologic, histochemical, myosin isoform, and ultrastructural evidence). In 33 pediatric patients, representing 96 patient-years of use, there were 26 failures of the pacing systems requiring removal and/or replacement of the internal components. Mean time to failure was 56 months. Of our 36 patients who had diaphragm pacing systems implanted, 26 are alive and 22 are currently using the pacing systems. wo recent advances may further improve the long-term outcome of patients using diaphragm pacing. Smaller, better encapsulated receivers may improve system longevity and a new stimulus electrode may reduce the risk of diaphragmatic damage.

Resonance Raman investigation of ferric iron in horseradish peroxidase and its aromatic donor complexes at room and low temperatures.

Resonance Raman (RR) spectra of the acidic form of FeIII horseradish peroxidase (HRP) were obtained at room and low temperatures using B- and Q-band excitation. At 296 K, HRP exhibits two sets of porphyrin skeletal stretching frequencies which are attributed to a thermal mixture of 5- and 6-coordinate high-spin FeIII states. When the temperature is lowered, the observed bands shift to higher frequencies, and these are assigned to intermediate- and low-spin states. Addition of 40% glycerol has no effect on the spectra at 296 K, but at 20 K, all four frequency sets are observed corresponding to the two forms observed at room and low temperature in the absence of glycerol. The 296 K RR spectrum of the HRP-hydroquinone complex is similar to that of free HRP, but conversion to the intermediate- and low-spin states is complete at a higher temperature than in the free enzyme. Addition of benzohydroxamic acid (BHA) to HRP shifts the RR frequencies to those corresponding to a 6-coordinate high-spin species at both room and low temperature. Two upsilon (C = C) stretching modes are observed for HRP and its donor complexes, indicating that the vinyl groups are inequivalent. On BHA binding, one of the vinyl modes and upsilon 37 (Eu) are enhanced, suggesting symmetry lowering of the heme site.

[Epidural sacral anesthesia with 3% mepivacaine in rectal surgery]. / Epidurale sacrale con mepivacaina 3% nella chirurgia proctologica.

The authors think that the sacral epidural anaesthesia effected with Mepivacaine 3%, 6 ml (180 mg) and Fentanyl 2 ml (100 mcg) is perfectly indicated for the proctologic surgery as it is of simple execution and presents a short latency (12 min.), good deepness and perfect haemodynamic stability. Besides, it does not endanger the lower limbs innervation. No urinary retention.

Effects of continuous low-frequency pacing on immature canine diaphragm.

Although diaphragm pacing has been shown to be a practical method of supporting ventilation in children, its usefulness has been limited because of concern that continuous (24 h/day) diaphragm pacing would fatigue and damage the diaphragm. We examined the functional and structural effects of continuous low-frequency diaphragm pacing on the left hemidiaphragm of five immature dogs aged 65 +/- 2 (SD) days at onset of pacing. Stimulus parameters approximated those required to pace infants: frequency 11.1 Hz, inspiratory time 810 ms, and respiratory rate 20 breaths/min. Animals were paced 24 h/day for 24-28 days. Paced tidal volumes and airway occlusion pressures were unchanged at low (less than 15 Hz) stimulus frequencies but were reduced at high (greater than 20 Hz) stimulus frequencies. Although histologically the paced hemidiaphragms appeared normal, histochemical studies showed a conversion from a mixture of type I (54%) and type II (46%) fibers to a uniform population of type I fibers with high oxidative enzyme activity. Transformation of muscle type was also demonstrated by pyrophosphate gel electrophoresis; fast and slow isomyosin bands were noted in control specimens, whereas only slow isomyosin was identified in paced specimens. Thus, in immature dogs, continuous low-frequency pacing affects both function and structure of the diaphragm.

Comparison of transthoracic impedance/heart rate monitoring and pulse oximetry for patients using diaphragm pacemakers.

Patients using diaphragm pacemakers have several respiratory-related problems placing them at high risk for death during sleep, including central hypoventilation, abnormal arousal responses, upper airway and/or tracheostomy obstruction, and, in the case of high quadriplegia, lack of motor response to airway obstruction. The recent death from airway obstruction of a patient using diaphragm pacemakers prompted us to re-evaluate both the need for home monitoring and the type of monitor to prescribe. We compared the performance of a transthoracic impedance/heart rate (TI/HR) monitor with that of a pulse oximeter in six patients with central hypoventilation syndrome whose treatment included diaphragm pacing. Polygraphic recordings of airflow, ECG, SaO2, transthoracic impedance, heart rate, and breath detection were obtained during brief tracheostomy occlusion during patient sleep. Although none of 13 occlusions was detected by the TI/HR monitor, the pulse oximeter identified 13 of 13 occlusions. Three reasons for TI/HR monitor failure included 1) the breath detection circuit consistently registered a breath with each obstructed, paced diaphragmatic contraction; 2) bradycardia did not occur during any airway occlusion; and 3) pacemaker stimuli were misinterpreted as additional heart beats, increasing apparent heart rate. Thus, pulse oximetry, but not TI/HR monitoring, can detect life-threatening airway obstruction in children using diaphragm pacemakers.

The perinatal management of central nervous system anomalies.

The diagnosis, proper evaluation, and treatment of a CNS anomaly requires the participation of many subspecialists and support personnel. The outcome can be favorably modified through the choice of elective termination, aggressive or passive perinatal intervention, and the 24-hour availability of neurosurgical expertise. At the conclusion of the pregnancy, accurate and informative counseling also should be provided. Although these discussions need not take place immediately, review of the final diagnosis, its risk of recurrence, and the appropriate screening for subsequent pregnancy should be included.

Raman excitation profiles of actinomycin D.

Pre-resonance Raman spectra of actinomycin D have been measured using the exciting lines of an Ar+ laser. The analysis of the excitation profiles provided information on the origin of the electronic states; in particular, the absorption feature between 400 and 500 nm was interpreted as due to a vibrational structure of a single electronic state which is located at 450 nm. In addition, on the basis of the excitation profiles, the number of observed Raman bands, and their frequencies, it has been possible to propose a vibrational assignment of the chromophoric framework of the drug.