Changes in chemical and ultrastructural composition of ameroid constrictors following in vitro expansion

Abstract

ObjectiveTo (1) characterise the chemical and ultra-structural composition of ameroid constrictors, at a native state and during in vitro expansion and (2) determine the presence of irritant compounds at the surface or within the bulk of the constrictor.MethodsTwelve sterile, commercially packaged ameroid constrictors (3 repeats of 3.5 mm, 5 mm, 6 mm and 7 mm internal diameter) were analysed by time-of-flight secondary ion mass spectrometry, Raman spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy and scanning electron microscopy.ResultsAmeroid constrictors have a composition commensurate with casein with little-to-no intra- or inter- constrictor variation. Microscopic analysis indicated that the topographical features of the constrictor surfaces were consistent between all constrictors. Following in vitro expansion there was a reproducible decrease in Ca+ ion content, little-to-no variation in secondary protein structure and morphological changes including the presence of surface aggregates present only at the inner surface of the ameroid constrictor. The potential irritant polydimethylsiloxane was found on the constrictor surface. A trace quantity of an ion fragment assigned as formaldehyde was detected; however, the extremely low level is thought highly unlikely to play a role as an inflammatory trigger clinically.DiscussionThere is a high degree of inter- and intra-constrictor homogeneity from different batches, and reproducible ultrastructural changes following in vitro expansion. Variations occur in both the surface chemistry and topography of the device during closure, which can potentially affect the biomaterial-host interface. Ameroid constrictor closure mechanism is likely involving calcium-mediated inter-protein interactions rather than the imbibition of water only.

Outcomes of dogs treated for extrahepatic congenital portosystemic shunts with thin film banding or ameroid ring constrictor

“…The apparent better predictability of shunt closure with AC compared to TFB in our population also reflects the findings of two studies reporting a much higher material consistency in chemical and ultrastructural analysis of AC compared to TFB. 10,15 We found the postoperative complication rates for both groups comparable (28% for TFB vs. 35% for AC). These rates are higher than those previously reported for these occlusion methods individually (9-13% reported for TFB and 10-20% for AC), 4,5,11,14,18,26 but close to the rates reported in a recent study comparing TFB (26%) and AC (23%).…”

“…[11][12][13][14] It was demonstrated by recent studies that AC closure mechanism was likely involving calcium-mediated inter-protein interactions rather than the imbibition of water only. 15,16 Complete shunt occlusion is achieved in 79-82% of dogs with this technique. 5,17 Persistence and recurrence of clinical signs is the most common complication of CPSS surgery and is reportedly due to incomplete vessel occlusion with persistent residual shunting (TFB -16-47%, AC -18-21%), suboptimal placement of the attenuating device (TFB -15-40%) or development of additional acquired shunts (TFB -19%, AC -4%).…”

Clinical outcomes for 20 cats with congenital extrahepatic portosystemic shunts treated with ameroid constrictor ring attenuation (2002–2020)

“…Surgical options for feline extrahepatic PSS (EHPSS) include acute partial or complete shunt ligation with suture, or gradual attenuation with thin film band or ameroid ring constrictor (ARC) 3–9 . Thin film bands and ARCs attenuate shunts through local stimulation of inflammation and fibrous tissue formation; ARCs also provide partial early compression secondary to calcium‐mediated interprotein interactions leading to swelling of the casein within the constraining metal ring, as well as thrombus formation 4,5,7,8,9,10,11,12 . Gradual occlusion with these devices reduces the risk of fatal portal hypertension 4,5,9,13 .…”

“…[3][4][5][6][7][8][9] Thin film bands and ARCs attenuate shunts through local stimulation of inflammation and fibrous tissue formation; ARCs also provide partial early compression secondary to calciummediated interprotein interactions leading to swelling of the casein within the constraining metal ring, as well as thrombus formation. 4,5,7,8,9,10,11,12 Gradual occlusion with these devices reduces the risk of fatal portal hypertension. 4,5,9,13 Some surgeons prefer ARCs over thin film bands because the bands vary in chemical composition, which could affect or limit the cat's inflammatory response to the device.…”

The chemical and ultra-structural analysis of thin plastic films used for surgical attenuation of portosystemic shunts in dogs and cats

“…ATR-IR and XPS techniques have been successfully applied to study several biomaterials in human and veterinary medicine (Ribuffo et al, 2015, Ameen et al, 1993, Tam et al, 2005Elsohaby et al, 2016, Lackowski et al, 2007, Anderson et al, 2018. Alone these techniques may not be sensitive enough to define the very top surface of a material (<10nm).…”