(-)-α-Bisabolol reduces nociception and trigeminal central sensitisation in acute orofacial neuropathic pain induced by infraorbital nerve injury.

Neuropathic orofacial pain conditions represent a challenge to diagnose and treat. Natural substances are promising therapeutic options for the control of pain. AIMS: This study aimed to examine whether (-)-α-bisabolol (BISA), a natural terpene, can attenuate nociceptive behaviour and central sensitisation in a rodent model of trigeminal neuropathic pain. MATERIALS AND METHODS: Infraorbital nerve transection (IONX) or sham operation was performed in adult male rats. Head withdrawal thresholds as a measure of facial mechanical sensitivity were tested with von Frey monofilaments applied bilaterally to the facial vibrissal pad pre-operatively (baseline) and then post-operatively before and at 60, 120, 240 and 360 min after administration of vehicle control per oris (p.o.) or BISA (200 mg/kg p.o.) (n = 8/group). Effects of BISA or vehicle on the activity of nociceptive neurons recorded in the medullary dorsal horn (MDH) were tested on post - operative day 8-10. ANOVA followed by post-hoc Bonferroni tested for statistically significant differences (p < 0.05) across study groups and time points. KEY FINDINGS: IONX animals (but not sham or naïve animals) showed post-operative facial mechanical hypersensitivity that was unaffected by vehicle. However, administration of BISA at post-operative day 7 significantly reversed the mechanical hypersensitivity in IONX rats; this effect lasted for at least 6 h. BISA also attenuated IONX-induced central sensitisation of MDH nociceptive neurons, as reflected in reversal of their reduced activation thresholds, increased responses to graded mechanical stimuli and enhanced spontaneous activity. SIGNIFICANCE: BISA may attenuate nociceptive behaviour and central sensitisation in a rat model of acute trigeminal neuropathic pain.

Pulsed plasma discharge polymer coatings.

The authors studied a pulsed radiofrequency glow discharge polymer film deposition method (pRFGD) on polyethylene terephthalate (PET), silicon (Si), and potassium chloride (KCl) surfaces, with the aim of better controlling film uniformity and homogeneity. A pulse generator was used to control a conventional 13.56 MHz RFGD circuit to provide plasma on and off times throughout a wide range of duty cycles. Starting monomers included fluorocarbon monomers (C8F16O and C3F6O) and more conventional unsaturated monomers [acrylonitrile (C3H3N) and vinyl trimethyl silane (C5H12Si)]. With each of these monomers progressive, large scale changes in the molecular structure of the plasma deposited films were noted with systematic variations in the RF duty cycle. Film characterizations were performed using electron spectroscopy for chemical analysis (ESCA) and fourier transform infrared (FTIR) analysis. In the case of fluorocarbon (FC) films, systematically decreasing plasma on time at a constant off time resulted in enhanced CF2 and CF3 content compared with that seen with the less highly fluorinated groups. There was virtually no oxygen atom incorporation in the FC films obtained from the oxygen containing monomers. Overall, a dramatic decrease in cross-linking of the FC polymer films was observed with decreasing RF duty cycles. A highly ordered Teflon-like structure was obtained for the lowest duty cycles. In the silane experiments, a systematic variation in the ratio of Si-H/Si-CH3 groups was observed, with this ratio increasing as the RF duty cycle decreased. Experiments with C3H3N revealed an increasing surface density of -CN groups with decreasing RF duty cycle.(ABSTRACT TRUNCATED AT 250 WORDS)

Molecular surface tailoring of biomaterials via pulsed RF plasma discharges.

A pulsed RF plasma glow discharge is employed to demonstrate molecular level controllability of surface film deposits. Molecular composition of plasma deposited films is shown to vary in a significant manner with the RF duty cycle. Three fluorocarbon monomers are used to illustrate the process. All three exhibit a trend towards increased surface CF2 content with decreasing pulsed RF duty cycle, including exclusion of oxygen. Significant variations in carbon-fluorine surface functionalities are obtained over a controllable range of film thickness. Film growth rate measurements reveal the occurrence of surface reactions during significant portions of the off portion of the duty cycle. Albumin adsorption on fluorocarbon-treated PET films is unchanged from PET controls for a 100-fold range of bulk concentrations and 60-fold range of adsorption times. However, increased retention of albumin is observed following incubation with protein-denaturing sodium dodecyl sulfate solution, the retention decreasing with increasing bulk concentration of albumin. The increased retention of albumin suggests the treated surfaces may have promise as biocompatible materials.