Biochemical properties of heat-treated valvular bioprostheses

Isolated aortic valve replacement with bio-prostheses in patients age 50 to 65 years: a decade of statewide data on cost and patient outcomes

BACKGROUND

Guidelines for choice of replacement valve-mechanical versus bio-prosthetic, are well established for patients aged <50 and >65 years. We studied the trends and implications of aortic valve replacement (AVR) with mechanical versus bioprosthetic valve in patients aged 50 to 65 years.

METHODS

STS and cost database of 17 centers for isolated AVR surgery were analyzed by dividing them into bioprosthetic valve (BV) or mechanical valve (MV) groups.

RESULTS

From 2002 to 2011, 3,690 patients had AVR, 18.6% with MV and 81.4% with BV. Use of BV for all ages increased from 71.5% in 2002 to 87% in 2011. There were 1127 (30.5%) patients in the age group 50-65 years. Use of BV in this group almost doubled, 39.6% in 2002 to 76.8% in 2011. Mean age of patients in BV group was higher (59.2±4.2 years vs. 56.7±4.3 years, P≤0.0001). Preoperative renal failure, heart failure and chronic obstructive pulmonary disease favored use of BV, whereas preoperative atrial fibrillation favored AVR with MV. Mortality (MV 2.2% vs. BV 2.36%) and other postoperative outcomes between the groups were similar. Cost of valve replacement increased for both groups (MV $26,191 in 2002 to $42,592 in 2011; BV $27,404 in 2002 to $44,257 in 2011).

CONCLUSIONS

Use of bioprostheses for AVR has increased; this change is more pronounced in patients aged 50-65 years. Specific preoperative risk factors influence the choice of valve for AVR. Postoperative outcomes between the two groups were similar. Long-term implications of this changing practice, in particular, reoperation for bioprosthetic valve degeneration should be examined.

Comparison on the properties of bovine pericardium and porcine pericardium used as leaflet materials of transcatheter heart valve

BACKGROUND

In order to obtain the smaller delivery diameter, porcine pericardium had been used as a substitute material of bovine pericardium for the leaflet materials of transcatheter heart valve (THV). However, the differences between them had not been fully studied. Therefore, this study compared the microstructure, biochemical and mechanical properties of two materials and hydrodynamics of THV made by the two materials in detail.

METHODS

In this study, firstly, the microstructure of pericardium was analyzed by staining and scanning electron microscope; secondly, the biochemical properties of pericardium after different processes were compared by heat shrinkage temperature test, free amino and carboxyl concentration test, enzyme degradation test, subcutaneous implantation calcification analysis in rats; finally, the mechanical properties were evaluated by uniaxial tensile test before and after the pericardium being crimped, and then, the hydrodynamics of THV was studied according to the ISO5840 standard.

RESULTS

Compared with bovine pericardium, after the same process, porcine pericardium showed a looser and tinier fiber bundle, a similar free carboxyl concentration, a lower resistance to enzyme degradation, a significantly lower calcification, bearing capacity and damage after being crimped, a better hydrodynamic and adaption with lower cardiac output and deformation of implantation position. Meanwhile the dehydration process of pericardium almost had preserved all the biochemical advantages of two materials.

CONCLUSION

In this study, porcine and bovine pericardium showed some significant differences in biochemical, mechanical properties and hydrodynamics. According to the results, it was presumed that the thinner porcine pericardium might be more suitable for THV of right heart system. Meanwhile, more attention should be taken for the calcification of THV made by the bovine pericardium.

A novel antibacterial acellular porcine dermal matrix cross-linked with oxidized chitosan oligosaccharide and modified by in situ synthesis of silver nanoparticles for wound healing applications

Not only are the physicochemical properties and biocompatibility of biomaterials important considerations, but also their antibacterial properties. In this study, a novel chemically-cross-linked antibacterial porcine acellular dermal matrix (pADM) scaffold was fabricated according to a two-step method. A naturally-derived oxidized chitosan oligosaccharide (OCOS) was used to cross-linked pADM (termed OCOS-pADM) to improve its physicochemical properties. Residual aldehyde groups within the OCOS-pADM were used in a redox reaction with Ag ions to produce Ag nanoparticles (AgNPs) in situ. As the AgNPs were tightly adhered onto the scaffold fibrils (termed OCOS-AgNPs-pADM), this effectively functionalized scaffold with antibacterial properties. The generated AgNPs were characterized by UV-Vis diffuse reflectance spectroscopy, XPS and SEM. The results of DSC, TG and enzymatic degradation demonstrated that OCOS-AgNPs-pADM possessed improved thermal stability and resistance to enzymatic degradation compared with pADM scaffolds. The kinetic experiment of the release of silver showed that silver was released in a controllable way. After introducing AgNPs into scaffolds, the OCOS-AgNPs-pADM possessed wide-spectrum antibacterial activity against Escherichia coli and Staphylococcus aureus. Furthermore, MTT assay and CLSM showed that the scaffolds had good biocompatibility. Pieces of OCOS-AgNPs-pADM were implanted into Sprague-Dawley rats to characterize their ability to repair full-thickness skin wounds. And results showed that the OCOS-AgNPs-pADM could accelerate the wound healing process. Overall, this work contributes new insight into the chemical cross-linking and functionalization of pADM scaffolds. In addition, as novel antibacterial scaffolds, OCOS-AgNPs-pADMs have the potential for development as wound dressing materials.

Fixation of vascular grafts with increased glutaraldehyde concentration enhances mechanical properties without increasing calcification

Our objective was to study the effect of glutaraldehyde (GLU) concentration, heat, and photooxidation on mechanical properties and calcification of bovine pericardium grafts in an in vivo model. Fresh pericardia were treated as follows: 0.625% GLU for 7 days (standard); 0.625%, 1%, and 3% GLU at 4 degrees C for 20 days and 50 degrees C for additional 20 days; irradiation in cross-linking medium with metilene blue at 0 degrees C for 8 hours. Tissues were subjected to tensile mechanical tests (n = 76). Fixed patches were subcutaneously implanted in mice for 50 days (n = 16 per treatment). Calcification was assessed by atomic absorption spectrophotometry (n = 55) and von Kossa staining (n = 28). Analysis of variance and Tukey's test were used for statistical analysis. The 3% GLU and 3% GLU + heat treatments showed an enhancement of the mechanical properties above standard treatment. No significant difference was found in calcification between treatments. The 3% GLU treatment enhances the mechanical properties of the tissue above standard treatment without increasing calcification and without applying heat; therefore it is recommended for high-strength applications. Supplementary treatments to decrease calcification could be combined with this methodology to obtain a high-strength-low-calcification biomaterial for manufacturing of long-term cardiovascular grafts.