Prevention of calcification of glutaraldehyde-crosslinked porcine aortic cusps by ethanol preincubation: Mechanistic studies of protein structure and water-biomaterial relationships

Abstract

Clinical usage of bioprosthetic heart valves (BPHVs) fabricated from glutaraldehyde-pretreated porcine aortic valves is restricted due to calcification-related failure. We previously reported a highly efficacious ethanol pretreatment of BPHVs for the prevention of cuspal calcification. The aim of the present study is to extend our understanding of the material changes brought about by ethanol and the relationship of these material effects to the ethanol pretreatment anticalcification mechanism. Glutaraldehyde-crosslinked porcine aortic valve cusps (control and ethanol-pretreated) were studied for the effects of ethanol on tissue water content and for spin-lattice relaxation times (T1) using solid state proton NMR. Cusp samples were studied for protein conformational changes due to ethanol by ATR-FTIR spectroscopy. The changes in cuspal tissue-cholesterol (in vitro) interactions also were studied. Cusp material stability was assessed in terms of residual glutaraldehyde content and collagenase degradation. Water content of the cusp samples was decreased significantly due to ethanol pretreatment. The cuspal collagen conformational changes (per infrared spectroscopy) brought about by ethanol pretreatment were persistent even after rat subdermal implantation of cusp samples for 7 days. In vitro cholesterol uptake by cusps was greatly reduced as a result of ethanol pretreatment. Ethanol pretreatment of cusps also resulted in increased resistance to collagenase digestion. Cuspal glutaraldehyde content was not changed by ethanol pretreatment. We conclude that ethanol pretreatment of bioprosthetic heart valve cusps causes multi-component effects on the tissue/material and macromolecular characteristics, which partly may explain the ethanol-pretreatment anticalcification mechanism.

A Review of the Biocompatibility of Implantable Devices: Current Challenges to Overcome Foreign Body Response

“…For instance, ethanol preincubation is known to be effective in preventing the calcification of glutaraldehyde cross-linked heart valves. 146,147 Since some surfactants such as sodium dodecyl sulfate reduce mineralization, these are used in commercial products, such as commercial porcine valves. 148,149 To prevent calcification induced by glutaraldehyde, chemical modification of the device surface has been investigated [e.g., using hyaluronic acid, 152 sulfonated poly(ethylene oxide) and heparin, 151,152 protamine, 153,154 bovine pericardium, [155][156][157] and l-arginine 156,157 ].…”

Pericardial Processing: Challenges, Outcomes and Future Prospects

“…Early results are promising but require further investigation on larger studies. Alcohol solutions, including ethanol, have been investigated as a treatment to remove tissue phospholipids, thus preventing calcification (Pathak et al, 2004;Vyavahare et al, 1998). Besides, other techniques have been proposed to minimize the side effects of glutaraldehyde residues on GA-treated pericardium.…”

Dynamic Simulation of Bioprosthetic Heart Valves Using a Stress Resultant Shell Model

“…27,28,30,45 Calcification can also occur near the area with large leaflet flexion where both tensile and compressive planar stresses are induced. 30,46 It was also reported that large deflection induced substantial bending stresses in BHV leaflets during the cardiac cycle contributing significantly to the total resultant stresses. 14 Therefore, it is important to perform an accurate dynamic analysis on BHV and determine the regions of extreme stress concentration during the entire cardiac cycle.…”

“…In general, it has been widely accepted that structural degeneration is frequently accompanied by excessive calcification on BHV leaflets causing stenosis and cuspal tears even though the detailed mechanism of calcification is still not clearly understood. 1,30,41,46 Cuspal commissures and basal attachments are the common locations of the deposition of calcified substances on BHV. 27,28,30,45 Calcification can also occur near the area with large leaflet flexion where both tensile and compressive planar stresses are induced.…”