ABSTRACT
The design of neural electrodes has changed in the past decade, driven mainly by the development of new materials that open the possibility of manufacturing electrodes with adaptable mechanical properties and promising electrical properties. In this paper, we report on the mechanical and electrochemical properties of a polydimethylsiloxane (PDMS) composite with edge-functionalized graphene (EFG) and demonstrate its potential for use in neural implants with the fabrication of a novel neural cuff electrode. We have shown that a 200 µm thick 1:1 EFG/PDMS composite film has a stretchability of up to 20%, a Young's modulus of 2.52 MPa, and a lifetime of more than 10000 mechanical cycles, making it highly suitable for interfacing with soft tissue. Electrochemical characterization of the EFG/PDMS composite film showed that the capacitance of the composite increased up to 35 times after electrochemical reduction, widening the electrochemical water window and remaining stable after soaking for 5 weeks in phosphate buffered saline. The electrochemically activated EFG/PDMS electrode had a 3 times increase in the charge injection capacity, which is more than double that of a commercial platinum-based neural cuff. Electrochemical and spectrochemical investigations supported the conclusion that this effect originated from the stable chemisorption of hydrogen on the graphene surface. The biocompatibility of the composite was confirmed with an in vitro cell culture study using mouse spinal cord cells. Finally, the potential of the EFG/PDMS composite was demonstrated with the fabrication of a novel neural cuff electrode, whose double-layered and open structured design increased the cuff stretchability up to 140%, well beyond that required for an operational neural cuff. In addition, the cuff design offers better integration with neural tissue and simpler nerve fiber installation and locking.
Subject(s)
Graphite , Nerve Tissue , Mice , Animals , Electrodes , Dimethylpolysiloxanes/chemistryABSTRACT
BACKGROUND: Allopurinol is a xanthine oxidase inhibitor used in the treatment of patients with gout. Approximately 2% of patients are affected by adverse reactions to this drug. Severity ranges from mild rashes to severe reactions in up to 0.4% of cases. De-sensitization is carried out by administering increasing doses of the drug. CASE REPORT: Thirty-year old man diagnosed with hypercholesterolemia and hypertriglyceridemia treated with bezafibrate and pravastatin, systemic arterial hypertension treated with losartan and a 10-year history of hyperuricemia with gout. Tophi were found in metacarpophalangeal joints and elbows. Treatment was started with allopurinol 300 mg/day. Two weeks later, he experienced facial erythema with itching and maculopapular lesions on the malar region 1 hour after the medication was ingested. An outpatient drug de-sensitization protocol was initiated, starting with 5 mg, and with gradual dose increases every 4 to 5 days for 59 days until the desired maintenance dose (300 mg) was reached. CONCLUSIONS: Experience shows that de-sensitization to allopurinol is a safe alternative when there is hypersensitivity and treatment with this drug is required.
Antecedentes: El alopurinol es un inhibidor de la xantinooxidasa usado en el tratamiento de pacientes con gota. Aproximadamente 2 % de los pacientes son afectados por reacciones adversas a dicho fármaco. La severidad varía de erupciones cutáneas leves a reacciones graves hasta en 0.4 % de los casos. La desensibilización se lleva a cabo incrementando paulatinamente la dosis del fármaco. Reporte de caso: Hombre de 30 años con diagnóstico de hipercolesterolemia e hipertrigliceridemia tratadas con bezafibrato y pravastatina, hipertensión arterial sistémica tratada con losartán e hiperuricemia con gota de 10 años de diagnóstico. Los tofos se encontraban en articulaciones metacarpofalángicas y codos. Se inició tratamiento con 300 mg diarios de alopurinol, a las dos semanas el paciente presentó eritema facial con prurito y lesiones maculopapulares en región malar una hora después de la ingesta del medicamento. Se inició protocolo ambulatorio de desensibilización a dicho fármaco comenzando con 5 mg, con incremento gradual de la dosis cada cuatro o cinco días por 59 días, hasta llegar a la dosis de mantenimiento deseada (300 mg). Conclusiones: La experiencia muestra que la desensibilización a alopurinol es una alternativa segura cuando existe hipersensibilidad y necesidad de tratamiento con este fármaco.
