Cardiovascular diseases are among the major causes of morbity and mortality. Particularly, the prevalence of heart valve disease(damaged heart valve leaflet) is one of the most common ailment. In elderly people, every year 30,000 patients are treated with heart valve replacement surgeries in the developed countries. Mechanical and bioprosthetic heart valves are commonly used in heart valve surgeries. While mechanical valves require the patient to be on blood thinning agent, rest of the life, bioprosthetic valves have only limited life span. Adequate knowledge of the biomechanics of nano-microscale structure and the viscoelastic properties of the native (bovine) heart valves can pave the ways for enhancing the strength of bio-prosthetic heart valves. In present work, we measured the viscoelastic and structural properties of the native bovine myocardiam and valvular tissue of heart valve. These heart valves were taken from bovine hearts and cryopreserved as necessary. The rheological and viscoelastic properties of heart valves were investigated by fixing in formaldehyde and phosphate buffer solutions (PBS). The samples were then tested in SEM (Scanning Electron Microscope) to investigate the microstructure of valve leaflets. Using Dynamic Shear Rheometer, the critical parameters such as modulus of elasticity, storage modulus, loss modulus, complex modulus, complex viscosity and the oscillatory shear properties were thoroughly investigated. Results show that the rheological properties vary with different chemical fixation effects. Chemical fixations like formaldehyde fixation were improving the rheological properties of heart valves. However, there is no significant influence of different time periods of fixations on mechanical properties. The complex modulus as well as the compression and storage moduli of the sample fixed with formaldehyde showed the satisfactory values after the fixation. It was indicating the mechanical strength has improved in terms of its structure, as much as solid/rigid as before the fixation. Also, the viscosity of fresh valve was higher, showing that the aldehyde fixation alters the mechanical property of the heart valve. Through the creep tests, it was investigated that the fixation of the heart valves did affect the viscoelasticity and mechanical properties of the heart valves. The valves become stiffer when they were fixed with formaldehyde. The reactions were less by a whole order of magnitude. However, by fixing the sample in formaldehyde we observed that the aortic valve had much more strength than the fresh sample. Another proof of how the aldehyde fixation drastically affected the stiffness of the valve was in the fact that the extension of the aldehyde-fixed valve under a stress of 5 kPa was less than that of the fresh valve at 0.5 kPa. These outcomes provide significant insights into the correlations between the microstructure and mechanics of the heart valves and their macro scale behaviors under various conditions. These results were modeled using Computer Aided Engineered software. The software can help scientists in evaluating the performance of tissue engineered heart valves with natural heart valves.

Heart valve (HV) diseases are among the leading causes of cardiac failure and deaths. Of the various HV diseases, damaged HV leaflets are among the primary culprits. In many cases, impaired HV restoration is not always possible, and the replacement of valves becomes necessary. Bioprosthetic HVs have been used for the replacement of the diseased valves, which is obtained from the sources of bovine and porcine origin, while tissue-engineered heart valves (TEHV) have emerged as a promising future solution. The bioprosthetic valves are prone to become calcified, and thus they last for only ten to fifteen years. The adequate understanding of the correlations between the biomechanics and rheological properties of native HV tissues can enable us to improve the durability of the bioprosthetic HV as well as help in the development of tissue-engineered heart valves (TEHV). In this study, the structural and rheological properties of native bovine aortic HV and pericardium tissues were investigated. The microstructures of the tissues were investigated using scanning electron microscopy, while the rheological properties were studied using oscillatory shear measurement and creep test. The reported results provide significant insights into the correlations between the microstructure and viscoelastic properties of the bovine aortic HV and pericardium tissues.

Non-healing chronic wounds are the key concern in type-2 diabetes that frequently leads to chronic infections, finally causing amputation of limbs, organs etc. Decrease in the proliferation and migration of cells such as keratinocytes and fibroblasts is the major reason for the development of such chronic diabetic wounds. Multiple evidences have shown that CTGF and reduced graphene oxide possesses angiogenic property and promote wound healing by promoting proliferation and migration of fibroblasts and keratinocytes cells.Conjugation of rGO with CTGF using EDC-NHS chemistry is a novel approach to accelerate the wound healing process. In the current work, we have developed a rGO/CTGF incorporated GelMA hydrogel dressing to improve wound healing by increasing proliferation and migration of cells as well as promoting formation of new blood vessels for increased supply of nutrients, oxygen and growth factors to wound area