Antimicrobial effects of silver nanoparticle-microspots on the mechanical properties of single bacteria

Silver nanoparticles (AgNPs) conjugated with polymers are well-known for their powerful and effective antimicrobial properties. In particular, the incorporation of AgNPs in biocompatible catecholamine-based polymers, such as polydopamine (PDA), has recently shown promising antimicrobial activity, due to the synergistic effects of the AgNPs, silver(I) ions released and PDA. In this study, we generated AgNPs-PDA-patterned surfaces by localised electrochemical depositions, using a double potentiostatic method via scanning electrochemical cell microscopy (SECCM). This technique enabled the assessment of a wide parameter space in a high-throughput manner. The optimised electrodeposition process resulted in stable and homogeneously distributed AgNP-microspots, and their antimicrobial activity against Escherichia coli was assessed using atomic force microscopy (AFM)-based force spectroscopy, in terms of bacterial adhesion and cell elasticity. We observed that the bacterial outer membrane underwent significant structural changes, when in close proximity to the AgNPs, namely increased hydrophilicity and stiffness loss. The spatially varied antimicrobial effect found experimentally was rationalised by numerical simulations of silver(I) concentration profiles.

[Functional disorders of the hypothalamo-pituitary-thyroid axis in epilepsy]

Changes of the hormonal functions of the axis hypothalamus-hypophysis-thyroid were assessed in epileptics prior to the beginning of the anticonvulsant therapy (50 cases), during short-lasting treatment (12 months) and during long-lasting treatment (54 cases treated during a mean period of 15.3 years). The serum levels were determined of thyreotropin (TSH), total T4, total T3, total cholesterol, and thyroxin-binding globulin capacity. The test of TRH stimulation was used for the determination of the hypothalamo-hypophyseal system function. It was found that epilepsy may impair the function of the axis hypothalamus-hypophysis-thyroid probably at the hypothalamic level. Anticonvulsants (diphenylhydantoin, phenobarbital, carbamazepine) may cause hormonal disturbances producing both tertiary and primary hypothyroidism, and in patients treated many years the response of the TSH was more evidently impaired than in the cases treated for a short time.