Early fitting in cochlear implant surgery: preliminary results.

PURPOSE: Cochlear implants are usually activated 3-5 weeks after surgery; to date, no universal protocol exists regarding switch on and fitting of these devices. The aim of the study was to assess safety and functional results of activation and fitting of cochlear implant within 24 h following surgery. METHODS: In this retrospective case-control study, 15 adult patients who underwent cochlear implant surgery, for a total of 20 cochlear implant procedures were analyzed. In particular, clinical safety and feasibility were investigated by examinating patients at activation and at each follow-up. Values of electrodes' impedance and most comfortable loudness (MCL) were analyzed from the time of surgery to 12 months after activation. Free-field pure tone average (PTA) was also recorded. RESULTS: No major or minor complications were reported and all patients could perform the early fitting. Activation modality influenced impedance values only in the short term but the differences were not statistically significant (p > 0.05). Mean MCL values in the early fitting group were lower than MCL of the late fitting in all follow-up sessions, and the difference was statistically significant (p < 0.05). The mean PTA was lower in the early fitting group but the difference was not statistically significant (p < 0.05). CONCLUSIONS: Early fitting of cochlear implants is safe, allows for an early rehabilitation and can have possible beneficial effects on stimulation levels and dynamic range.

Cochlear implantation after solid organ transplantation: long term results and review of the literature.

OBJECTIVE: To analyze rate and type of complications in cochlear implant (CI) recipients receiving immunosuppressive therapy following solid organ transplant (SOT). STUDY DESIGN: Retrospective case series. English language literature review. SETTING: Tertiary referral center. INTERVENTION: Cochlear implantation surgery following solid organ transplantation (SOT) and immunosuppressive therapy. METHODS: Data of patients who received CI after SOT and with at least one year of follow up were reviewed. Main outcome measures were the rate and type of complications, classified as major (requiring a second surgical procedure) and minor (requiring medical therapy). A search was performed in PubMed database on January 2019 using the keywords: organ transplant; cochlear implant, complications, deafness, solid organ transplant, immunosuppressive therapy. Only studies reporting on patients who have been implanted after the transplant procedure and with a follow up period of at least 1 year were considered. Final analysis was performed on pooled data. RESULTS: Four patients received CI surgery following SOT. Age at treatment ranged from 40 to 47 years (mean 44.25 years). Follow-up after implantation averaged 5.25 years (range 1-10 years), without complications. Review of the available literature on the subject yielded seven papers; a total of 26 procedures in 22 patients satisfied inclusion criteria. Pooled data from the present series and from the literature were analyzed; the global rate of complications was 16.6%, with 10% major (3 of 30 procedures) and 6.6% minor (2 of 30 procedures). The three reported cases of major complications appear unrelated to SOT. Major complications were found in one case over 16 procedures in pediatric patients (6.2%), while in adults the percentage raised to 14.3% (2/14 procedures). CONCLUSIONS: Cochlear implantation is a safe and effective intervention, even during immunosuppressive therapy after organ transplantation.

Low-Temperature Storage Improves the Over-Time Stability of Implantable Glucose and Lactate Biosensors.

Molecular biomarkers are very important in biology, biotechnology and even in medicine, but it is quite hard to convert biology-related signals into measurable data. For this purpose, amperometric biosensors have proven to be particularly suitable because of their specificity and sensitivity. The operation and shelf stability of the biosensor are quite important features, and storage procedures therefore play an important role in preserving the performance of the biosensors. In the present study two different designs for both glucose and lactate biosensor, differing only in regards to the containment net, represented by polyurethane or glutharaldehyde, were studied under different storage conditions (+4, -20 and -80 °C) and monitored over a period of 120 days, in order to evaluate the variations of kinetic parameters, as VMAX and KM, and LRS as the analytical parameter. Surprisingly, the storage at -80 °C yielded the best results because of an unexpected and, most of all, long-lasting increase of VMAX and LRS, denoting an interesting improvement in enzyme performances and stability over time. The present study aimed to also evaluate the impact of a short-period storage in dry ice on biosensor performances, in order to simulate a hypothetical preparation-conservation-shipment condition.

Prevention and management of vascular complications in middle ear and cochlear implant surgery.

The objective of this study is to illustrate prevention strategies and management of vascular complications from the jugular bulb (JB) and internal carotid artery (ICA) during middle ear surgery or cochlear implantation. The study design is retrospective case series. The setting is tertiary referral university hospital. Patients were included if presented pre- or intraoperative evidence of high-risk anatomical anomalies of ICA or JB during middle ear or cochlear implant surgery, intraoperative vascular injury, or revision surgery after the previous iatrogenic vascular lesions. The main outcome measures are surgical outcomes and complications rate. Ten subjects were identified: three underwent cochlear implant surgery and seven underwent middle ear surgery. Among the cochlear implant patients, two presented with anomalies of the JB impeding access to the cochlear lumen and one underwent revision surgery for incorrect positioning of the array in the carotid canal. Subtotal petrosectomy was performed in all cases. Anomalies of the JB were preoperatively identified in two patients with attic and external auditory canal cholesteatoma, respectively. In a patient, a high and dehiscent JB was found during myringoplasty, while another underwent revision surgery after iatrogenic injury of the JB. A dehiscent ICA complicated middle ear effusion in one case, while in another case, a carotid aneurysm determined a cholesterol granuloma. Rupture of a pseudoaneurysm of the ICA occurred in a child during second-stage surgery and required permanent balloon occlusion without neurological complications. Knowledge of normal anatomy and its variants and preoperative imaging are the basis for prevention of vascular complications during middle ear or cochlear implant surgery.

Cochlear implantation in patients with Cogan syndrome: long-term results.

The objective of this study was to evaluate the long-term outcomes of patients with Cogan syndrome (CS) who have undergone cochlear implantation. Subjects consisted of 12 cochlear implant users with a typical form of CS. Measures included word and sentence recognition scores. The speech recognition performance was rated before cochlear implantation and at 1 and 5 years after implantation. The speech materials were presented in quiet only condition. The mean 12-month post-operative word and sentence recognition scores were 91.4 and 93.1%, respectively. Five years after implantation, the group means for word and sentence recognition tests were 94 and 96.3%, respectively. No patients in this series experienced flap complication or other local or systemic complications. This long-term study on 12 subjects with CS over 5 years of cochlear implant use reveals that cochlear implantation is safe in the long term and provides excellent and stable hearing results.

Lower cranial nerves function after surgical treatment of Fisch Class C and D tympanojugular paragangliomas.

The aim of this study was to report the postoperative lower cranial nerves (LCNs) function in patients undergoing surgery for tympanojugular paraganglioma (TJP) and to evaluate risk factors for postoperative LCN dysfunction. A retrospective case review of 122 patients having Fisch class C or D TJP, surgically treated from 1988 to 2012, was performed. The follow-up of the series ranged from 12 to 156 months (mean, 39.4 ± 32.6 months). The infratemporal type A approach was the most common surgical procedure. Gross total tumor removal was achieved in 86% of cases. Seventy-two percent of the 54 patients with preoperative LCN deficit had intracranial tumor extension. Intraoperatively, LCNs had to be sacrificed in 63 cases (51.6%) due to tumor infiltration. Sixty-six patients (54.09%) developed a new deficit of one or more of the LCNs. Of those patients who developed new LCN deficits, 23 of them had intradural extension. Postoperative follow-up of at least 1 year showed that the LCN most commonly affected was the CN IX (50%). Logistic regression analysis showed that intracranial transdural tumor extension was correlated with the higher risk of LCN sacrifice (p < 0.05). Despite the advances in skull base surgery, new postoperative LCN deficits still represent a challenge. The morbidity associated with resection of the LCNs is dependent on the tumor's size and intradural tumor extension. Though no recovery of LCN deficits may be expected, on long-term follow-up, patients usually compensate well for their LCNs loss.

Cochlear implantation in irradiated tympanojugular paraganglioma.

OBJECTIVE: Indications for cochlear implantation have extended progressively over the years both from an audiological and clinical point of view, including the introduction of cochlear implants (CI) for hearing rehabilitation following skull base surgeries and neurotological procedures. In the past, cochlear implantation has been used for hearing rehabilitation in radiation-induced sensorineural hearing loss in nasopharyngeal and tonsillar carcinoma with successful outcomes. Here we describe a similar outcome following total deafness after tympanojugular paraganglioma irradiation, which is also the first such report in literature. DESIGN: The irradiated ear of this patient was implanted with a CI through standard posterior tympanotomy. STUDY SAMPLE: A 26 year old male with multiple paragangliomas with bilateral deafness, secondary to surgery on one ear and radiotherapy for the opposite ear. RESULTS: After a follow-up of 48 months, no local complications have occurred and the hearing results have remained stable with 100% sentence recognition. CONCLUSIONS: Bilateral and multiple paragangliomas are rare tumors. Despite the modality of treatment, the hearing is almost always compromised. In these patients, cochlear implantation offers a new perspective for hearing restoration. This report demonstrates that cochlear implantation can be effectively performed after tympanojugular paraganglioma irradiation with long-lasting, satisfactory results, even in the presence of residual tumor.

Lipomas of the internal auditory canal and cerebellopontine angle.

OBJECTIVES: Lipomas of the internal auditory canal (IAC) and cerebellopontine angle (CPA) are exceedingly rare lesions. The purpose of this report was to describe our experience with lipomas of the IAC and CPA and perform a review of the literature. METHODS: We report 8 cases of lipomas involving the IAC and/or the CPA that were managed at Gruppo Otologico between April 1987 and October 2012. RESULTS: Four cases of entirely intracanalicular lipomas were radiologically misinterpreted as vestibular schwannomas and underwent tumor removal by a translabyrinthine approach. Two of these patients experienced postoperative facial nerve palsy. Lipomas were suspected in 4 patients on the basis of imaging findings and were managed conservatively. Of these 4 cases, 3 did not show any growth after an average period of 28 months, and 1 case demonstrated tumor growth on follow-up imaging. CONCLUSIONS: Neuroimaging represents an extremely important tool for this diagnosis. Attempts to achieve complete resection may result in severe neurologic sequelae, especially in large lesions. Observation with repeated imaging in order to detect growth of the lesion is usually recommended. Debulking of the tumor, mainly aimed at brain stem and cranial nerve decompression, should be considered in cases of disabling and uncontrolled neurologic symptoms and signs.

Intraoperatively diagnosed cerebellopontine angle facial nerve schwannoma: how to deal with it.

OBJECTIVE: This study aimed to report our experience in the management of patients with intraoperatively diagnosed intracranial facial nerve schwannomas (FNSs) and propose a decision-making strategy. METHODS: Twenty-three patients with FNS of the internal auditory canal and/or cerebellopontine angle operated on between 1992 and 2012 were identified. RESULTS: Preoperatively, all cases have been radiographically diagnosed as vestibular schwannomas. Operative procedures consisted of total tumor resection with grafting in 43.4% of patients, near-total resection leaving behind the tumor capsule overlying the facial nerve in 21.7%, total tumor resection with preservation of anatomic continuity of the facial nerve in 13%, and subtotal resection in 4.3%. Four patients (17.4%) underwent bony decompression with no tumor removal. CONCLUSION: Management of FNS diagnosed at surgery represents a significant clinical challenge. We considered total tumor resection with grafting when patients presented with preoperative facial nerve palsy (≥ grade III). Both subtotal and near-total tumor removal can be performed in patients with preoperative good facial function and/or large tumors with brainstem compression. Patients with small tumors who were selected for hearing preservation surgery can be considered for bony decompression. Fascicle preservation surgery may be an option when a clear cleavage plane between the tumor and the facial nerve is found.

Long-term results of external auditory canal closure and mastoid obliteration in cochlear implantation after radical mastoidectomy: a clinical and radiological study.

Cochlear implant candidates with mastoid cavity present a significant challenge to safe cochlear implantation because of possible spread of infection to the inner ear as well as an increased risk of electrode array extrusion. Closure of the external auditory canal is one of the several surgical techniques utilized to block the potential entry routes for infection and to protect the implanted device. The main concern after external auditory canal closure is the risk of developing a cholesteatoma, which can lead to an asymptomatic erosion of the temporal bone and/or cochlear implant failure. In this study we present the results of very long-term (mean 12 years) clinical and radiological follow-up in 12 patients who underwent external auditory canal closure associated with mastoid and Eustachian tube obliteration to facilitate cochlear implantation. To date, with a mean ± SD follow-up of 12 ± 4.7 years (range 5-21 years), the only complication experienced was the breakdown of the EAC closure in one patient, successfully treated by performing a rotation skin flap. The results of this study confirmed that external auditory canal closure is a reliable technique in cochlear implantation after radical mastoidectomy provided that a rigorous surgical technique is performed. A right balance between the need to reduce costs and to avoid unnecessary doses of radiation to patients and the task of a radiological surveillance may be represented by performing computed tomography 12-18 months postoperatively and then, only if clinically warranted.

Are the current treatment strategies for facial nerve schwannoma appropriate also for complex cases?

OBJECTIVES: To describe the decision-making strategies for complex facial nerve schwannomas (FNSs). MATERIALS AND METHODS: Charts belonging to 103 consecutive patients with facial nerve tumors managed between 1990 and 2011 were examined retrospectively to identify complex FNSs. To be classified as complex, at least one of the following criteria had to be met: (1) FNS with large intraparotid tumor component and preoperative good facial nerve function (3 cases); (2) multiple-segment FNSs with extension to both the cerebellopontine angle and the middle cranial fossa in patients with preoperative good hearing (5 cases); (3) fast-growing FNS with preoperative good facial nerve function (4 cases), and (4) large FNS compressing the temporal lobe with preoperative normal facial nerve function (1 case). RESULTS: Thirteen patients were classified as complex; 12 patients had total tumor removal with sural nerve grafting and 1 patient had partial tumor removal. Two patients with intratemporal-intraparotid FNS underwent a transmastoid-transparotid approach. One patient with a tumor extending from the geniculate ganglion to the parotid portion of the facial nerve underwent a combined middle fossa transmastoid-transparotid approach. A transcochlear approach with temporal craniotomy was performed in all the patients with multiple-segment FNS as well as in patients with fast-growing tumors extending both in the cerebellopontine angle and middle cranial fossa. A partial tumor removal through the middle fossa approach was performed in 1 patient with a large tumor compressing the temporal lobe. CONCLUSIONS: Therapeutic options for patients with FNS include surgical intervention, observation and radiotherapy. Nowadays, surgical resection with facial nerve repair is usually the standard management for patients with poor facial function (House-Brackmann grade III or worse). In patients presenting with normal or near-normal facial nerve function, initial observation with periodic examination and imaging is usually recommended. However, on rare occasions surgeons can be faced with a situation in which the management decision-making process is particularly challenging. In these complex cases treatment should be individualized. We recommend early surgical intervention regardless of the preoperative facial and hearing functions in the following cases: intratemporal FNSs extending with a large tumor component into the parotid, multiple-segment FNSs extending in both the cerebellopontine angle and the middle cranial fossa, fast-growing FNSs, and large FNSs with temporal lobe compression.

Preoperative protective stenting of the internal carotid artery in the management of complex head and neck paragangliomas: long-term results.

OBJECTIVES: To investigate the long-term results of preoperative stenting of the internal carotid artery (ICA) in complex head and neck paragangliomas (HNP) as well as to report on indications and technical details of the procedure. METHOD: A comprehensive retrospective review of patients affected by HNP, consecutively operated on and preoperatively treated with stenting of the ICA in a quaternary referral skull base center, was performed. RESULTS: Nineteen patients affected by complex HNP were identified, on whom 21 preoperative stenting procedures were performed. The mean follow-up period after stent insertion was 53.8 months; the patients' age ranged from 33 to 56 years. Fourteen patients were affected by tympanojugular paragangliomas, 4 by vagal paragangliomas and 1 by bilateral carotid body tumors. Five patients presented with recurrent tumors, while 7 presented with multiple or bilateral HNP. There were no complications associated with endovascular procedures. Total tumor removal was accomplished in 52.4% of the cases with 1 recurrence. An advanced stage was the main factor conditioning total removal. Clinical control was obtained in 80% of the patients with residual disease. Total tumor removal from and around the ICA was obtained in 95.2% of the cases. Long-term stent patency was evident in 20 of 21 cases. CONCLUSIONS: Preoperative stenting of the ICA represents a safe and effective procedure in selected cases, obviating the need for balloon occlusion or bypass procedures and reducing the risk of intraoperative vascular injury.

Unilateral ectopic parotid gland in CHARGE syndrome.

Unilateral absence of a parotid gland at the expected location is an extremely rare condition with only a few cases reported in the medical literature and, to our knowledge, never previously described in association with CHARGE syndrome (Coloboma of the eye, Heart defects, Atresia of the choanae, Retardation of growth and/or development, Genital and/or urinary abnormalities, and Ear abnormalities and deafness). Although this entity is usually associated with a complex constellation of anomalies, additional findings have been described, including cranial nerve dysfunction (VII, VIII, IX and X). We present a case that illustrates the association of CHARGE syndrome with absence of parotid gland at normal location with ectopic parotid tissue lateral to masseter muscle, incidentally detected on brain MRI and subsequently confirmed on neck MRI.

Skull base chondrosarcomas: surgical treatment and results.

OBJECTIVES: We describe our experience in the management of patients with skull base chondrosarcoma, an uncommon neoplasm of the skull base. METHODS: Thirteen cases of surgically treated skull base chondrosarcomas were identified. The patients' follow-ups ranged from 7 to 86 months (mean, 47 months). RESULTS: The most common tumor locations were the jugular foramen (5 cases), the petrous apex (3 cases), and the petroclival region (3 cases). An infratemporal fossa type A approach was performed in 2 cases, and 2 patients underwent an infratemporal fossa type B approach. Two patients underwent a transotic approach, 1 patient underwent a petro-occipital transsigmoid approach, and a petro-occipital transsigmoid approach combined with a transotic approach was chosen in 1 case. One patient underwent an infratemporal fossa type C approach combined with a transotic approach, and 2 patients underwent an infratemporal fossa type B approach combined with a transotic approach. One patient underwent an infratemporal fossa type B approach combined with a transzygomatic approach, and the last patient underwent a transmastoid approach. Gross total tumor removal was achieved in all patients. Postoperative radiotherapy was performed in 7 cases. The most common complications were lower cranial nerve deficits. Two patients experienced recurrences, 36 months and 6 years after surgical removal. CONCLUSIONS: We believe that the primary treatment for chondrosarcomas of the skull base is gross total surgical resection. We usually do not recommend radiotherapy as the primary treatment for patients with skull base chondrosarcomas; however, radiotherapy may be considered as an alternative primary treatment in selected cases in which there are serious medical contraindications to surgery, as well as in elderly patients. We reserve postoperative radiotherapy for patients with histologically aggressive tumors (grade II or III), as well as for cases of subtotal resection or recurrent tumors.

Noonan syndrome: cochlear implantation in the setting of cochlear nerve deficiency.

BACKGROUND AND AIM: Noonan syndrome (NS) is a congenital disorder characterized by a wide heterogeneity in clinical and genetic features. Hearing loss can frequently occur in NS, although not always mentioned in its diagnostic criteria. We are reporting on a child with an established NS who underwent bilateral cochlear implantation (CI) in the setting of cochlear nerve deficiency. CASE PRESENTATION: We present the case of a child-girl affected by NS. Newborn hearing screening and audiological evaluations reveled an asymmetric sensorineural hearing loss (SNHL), profound at left ear and severe at right ear. Hearing aids were fitted at the age of six months. Brain magnetic resonance imaging showed hypoplastic cochlear nerves. Due to progressive worsening of the hearing thresholds and inappropriate speech development, at the age of 2 years she underwent a left-sided cochlear implantation. Four years later, right ear was also implanted. Six years after the first surgery, a partial extrusion of the electrode array was noticed. Explantation and reimplantation of a new device was performed, adopting a subtotal petrosectomy approach. The patient reached a score of 95% in open-set speech perception tests. CONCLUSIONS: Hearing loss is a frequent finding in patients with NS; however, its nature and severity are very heterogenous. In consideration of the possible progression of SNHL, audiological follow-up in NS patients must be carefully and periodically performed so as to early detect worsening of hearing threshold. If indicated, cochlear implantation should be considered, taking account of audiological and systemic features of this syndrome.

Study on transfer learning capabilities for pneumonia classification in chest-x-rays images.

BACKGROUND: over the last year, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) and its variants have highlighted the importance of screening tools with high diagnostic accuracy for new illnesses such as COVID-19. In that regard, deep learning approaches have proven as effective solutions for pneumonia classification, especially when considering chest-x-rays images. However, this lung infection can also be caused by other viral, bacterial or fungi pathogens. Consequently, efforts are being poured toward distinguishing the infection source to help clinicians to diagnose the correct disease origin. Following this tendency, this study further explores the effectiveness of established neural network architectures on the pneumonia classification task through the transfer learning paradigm. METHODOLOGY: to present a comprehensive comparison, 12 well-known ImageNet pre-trained models were fine-tuned and used to discriminate among chest-x-rays of healthy people, and those showing pneumonia symptoms derived from either a viral (i.e., generic or SARS-CoV-2) or bacterial source. Furthermore, since a common public collection distinguishing between such categories is currently not available, two distinct datasets of chest-x-rays images, describing the aforementioned sources, were combined and employed to evaluate the various architectures. RESULTS: the experiments were performed using a total of 6330 images split between train, validation, and test sets. For all models, standard classification metrics were computed (e.g., precision, f1-score), and most architectures obtained significant performances, reaching, among the others, up to 84.46% average f1-score when discriminating the four identified classes. Moreover, execution times, areas under the receiver operating characteristic (AUROC), confusion matrices, activation maps computed via the Grad-CAM algorithm, and additional experiments to assess the robustness of each model using only 50%, 20%, and 10% of the training set were also reported to present an informed discussion on the networks classifications. CONCLUSION: this paper examines the effectiveness of well-known architectures on a joint collection of chest-x-rays presenting pneumonia cases derived from either viral or bacterial sources, with particular attention to SARS-CoV-2 contagions for viral pathogens; demonstrating that existing architectures can effectively diagnose pneumonia sources and suggesting that the transfer learning paradigm could be a crucial asset in diagnosing future unknown illnesses.

Subtotal petrosectomy and cochlear implantation.

OBJECTIVE: The objective of this study is to analyse surgical outcomes in a series of patients who underwent subtotal petrosectomy in combination with cochlear implantation. METHODS: Retrospective chart review. Thirty patients (32 ears) underwent subtotal petrosectomy and cochlear implantation in one stage. Indications for subtotal petrosectomy included the following: cholesteatoma, chronic otitis media, previous canal wall-down, osteoradionecrosis, revision surgery for clinical reasons, inner ear malformations, middle ear anatomical variations and severe cochlear ossification. RESULTS: Follow-up ranged from 2 to 54 months. Only 2 complications related to the subtotal petrosectomy (1 subcutaneous abdominal haematoma and 1 subcutaneous abdominal seroma) occurred in this series. Complete electrode insertion was achieved in all but 4 cases. CONCLUSIONS: Subtotal petrosectomy is a safe procedure and can offer technical advantages in some cases of complex cochlear implantation.

Intracranial facial nerve grafting after removal of vestibular schwannoma.

OBJECTIVE: The objectives of this study were to evaluate outcomes from facial nerve (FN) cable grafting in patients who experienced FN transection during vestibular schwannoma removal and to compare the FN outcomes of patients who underwent FN grafting by using fibrin glue with those of patients who underwent FN grafting by using microsuture. MATERIAL AND METHODS: We retrospectively evaluated a series of 33 patients in whom FN grafting was achieved either by using microsuture (8 cases) or fibrin glue (25 cases). Immediate repair of the FN was performed in all cases at the time of initial resection. The patients FN function was assessed preoperatively, in the immediate postoperative period, and at 3, 6, 9, and 12 months or more postoperatively using the House-Brackmann grading system. All patients had at least 1-year follow-up. RESULTS: At 12 months, a House-Brackmann grade III was achieved in 75% of those who underwent cable nerve graft interposition by using microsuture and in 76% of those who underwent cable nerve graft interposition by using fibrin glue. Analysis of final FN function outcomes demonstrated no statistically significant difference in FN outcomes between the 2 groups (P = .891, Mann-Whitney U test; P = .1, Fisher exact test). CONCLUSIONS: The functional results after FN cable grafting by using fibrin glue exclusively were equivalent to those obtained with microsuture. However, the technique of FN repair by means of fibrin glue is technically simple, less time-consuming, and imparts less trauma on the nerve than does the traditional suture method.

The Presence of Polysaccharides, Glycerol, and Polyethyleneimine in Hydrogel Enhances the Performance of the Glucose Biosensor.

The use of amperometric biosensors has attracted particular attention in recent years, both from researchers and from companies, as they have proven to be low-cost, reliable, and very sensitive devices, with a wide range of uses in different matrices. The continuous development of amperometric biosensors, since their use involves an enzyme, is specifically aimed at keeping and increasing the catalytic properties of the loaded protein, so as to be able to use the same device over time. The present study aimed to investigate the impact of glycerol and polysaccharides, in the presence of polycationic substances to constitute a hydrogel, in enhancing the enzymatic and analytic performance of a glucose biosensor. Initially, it was possible to verify how the deposition of the starch-based hydrogel, in addition to allowing the electropolymerization of the poly(p-phenylenediamine) polymer and the maintenance of its ability to shield the ascorbic acid, did not substantially limit the permeability towards hydrogen peroxide. Moreover, different biosensor designs, loading a mixture containing all the components (alone or in combination) and the enzyme, were tested in order to evaluate the changes of the apparent enzyme kinetic parameters, such as VMAX and KM, and analytical response in terms of Linear Region Slope, highlighting how the presence of all components (starch, glycerol, and polyethyleneimine) were able to substantially enhance the performance of the biosensors. The surface analysis of the biosensors was performed by scanning electron microscope (SEM). More, it was shown that the same performances were kept unchanged for seven days, proving the suitability of this biosensor design for short- and mid-term use.

Real-time telemetry monitoring of oxygen in the central complex of freely-walking Gromphadorhina portentosa.

A new telemetric system for the electrochemical monitoring of dissolved oxygen is showed. The device, connected with two amperometric sensors, has been successfully applied to the wireless detection of the extracellular oxygen in the central complex of freely-walking Gromphadorhina portentosa. The unit was composed of a potentiostat, a two-channel sensor conditioning circuit, a microprocessor module, and a wireless serial transceiver. The amperometric signals were digitalized and sent to a notebook using a 2.4 GHz transceiver while a serial-to-USB converter was connected to a second transceiver for completing the communication bridge. The software, running on the laptop, allowed to save and graph the oxygen signals. The electronics showed excellent stability and the acquired data was linear in a range comprised between 0 and -165 nA, covering the entire range of oxygen concentrations. A series of experiments were performed to explore the dynamics of dissolved oxygen by exposing the animals to different gases (nitrogen, oxygen and carbon dioxide), to low temperature and anesthetic agents (chloroform and triethylamine). The resulting data are in agreement with previous O2 changes recorded in the brain of awake rats and mice. The proposed system, based on simple and inexpensive components, can constitute a new experimental model for the exploration of central complex neurochemistry and it can also work with oxidizing sensors and amperometric biosensors.